Hydrogen Injection in a Dual Fuel Engine Fueled with Low-Pressure Injection of Methyl Ester of Thevetia Peruviana (METP) for Diesel Engine Maintenance Application

energies

Article Hydrogen Injection in a Dual Fuel Engine Fueled with Low-Pressure Injection of Methyl Ester of Thevetia Peruviana (METP) for Diesel Engine Maintenance Application

Mahantesh Marikatti 1, N. R. Banapurmath 2, V. S. Yaliwal 1, Y.H. Basavarajappa 3, Manzoore Elahi M Soudagar 4 , Fausto Pedro García Márquez 5,* , MA Mujtaba 4 , H. Fayaz 6, Bharat Naik 7, T.M. Yunus Khan 8 , Asif Afzal 9 and Ahmed I. EL-Seesy 10

1 Department of Mechanical Engineering, SDM College of Engineering and Technology, Dharwad, Karnataka 580002, India; mkmarikatti@rediffmail.com (M.M.); vsyaliwal2000@rediffmail.com (V.S.Y.) 2 Department of Mechanical Engineering, B.V.B. College of Engineering and Technology KLE Technological University, BVB College Campus, Hubli, Karnataka 580021, India; [email protected] 3 Department of Mechanical Engineering, P.E.S. Institute of Technology and Management, Shivamogga 577204, India; [email protected] 4 Department of Mechanical Engineering, Faculty of Mechanical Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia; [email protected] (M.E.M.S.); [email protected] (M.M.) 5 Ingenium Research Group, University of Castilla-La Mancha, Ciudad Real 13071, Spain 6 Modeling Evolutionary Algorithms Simulation and Artificial Intelligence, Faculty of Electrical & Electronics Engineering, Ton Duc Thang University, Ho Chi Minh City 758307, Vietnam; [email protected] 7 Department of Mechanical Engineering, Jain College of Engineering, Belagavi Karnataka 590014, India; [email protected] 8 Research Center for Advanced Materials Science (RCAMS), King Khalid University, P.O. Box 9004, Abha 61413, Asir, Saudi Arabia; [email protected] 9 P. A. College of Engineering (Affiliated to Visvesvaraya Technological University, Belagavi), Mangalore 574153, India; [email protected] 10 Department of Mechanical Engineering, Benha Faculty of Engineering, Benha University, 13512 Benha, Qalubia, Egypt; [email protected] * Correspondence: [email protected]; Tel.: +34-926-295300

Received: 31 July 2020; Accepted: 22 October 2020; Published: 29 October 2020

Abstract: The present work is mapped to scrutinize the consequence of biodiesel and gaseous fuel properties, and their impact on compression-ignition (CI) engine combustion and emission characteristics in single and dual fuel operation. Biodiesel prepared from non-edible oil source derived from Thevetia peruviana belonging to the plant family of Apocynaceaeis. The fuel has been referred as methyl ester of Thevetia peruviana (METP) and adopted as pilot fuel for the effective combustion of compressed gaseous fuel of hydrogen. This investigation is an effort to augment the engine performance of a biodiesel-gaseous fueled diesel engine operated under varied engine parameters. Subsequently, consequences of gas flow rate, injection timing, gas entry type, and manifold gas injection on the modified dual-fuel engine using conventional mechanical fuel injections (CMFIS) for optimum engine performance were investigated. Fuel consumption, CO, UHC, and smoke formations are spotted to be less besides higher NOx emissions compared to CMFIS operation. The fuel burning features such as ignition delay, burning interval, and variation of pressure and heat release rates with crank angle are scrutinized and compared with base fuel. Sustained research in this direction can convey practical engine technology, concerning fuel combinations in the dual fuel mode, paving the way to alternatives which counter the continued fossil fuel utilization that has detrimental impacts on the climate.

Energies 2020, 13, 5663; doi:10.3390/en13215663 www.mdpi.com/journal/energies Energies 2020, 13, 5663 2 of 27

Keywords: methyl ester Thevetia peruviana (METP) biodiesel; manifold injection; combustion parameters; hydrogen injection; electronic control unit

1. Introduction Brake thermal efficiency, fuel consumption, power, consistency, and robustness of compression ignition (CI) engines are more than their counterpart petrol engines. Hence, they are well accepted for applications related to sectors of power, transport, and agriculture. Achieving improved conservation of energy with high brake thermal efficiency associated with lower emissions are given prime importance, and they are imperative for engine design and development [1,2]. Diesel engines operate on a wide range of alternative and renewable fuels (biodiesels, alcohols, and gases like Compressed Natural Gas (CNG), hydrogen, producer gas, and biogas) [3]. Researchers have explored these alternatives to conventional fuel from the perspective of lowering oil-import burdens on developing countries, heralding self-reliance through sustainable energy [4,5]. Several investigators have studied techniques to strengthen the performance of a compression-ignition (CI) engine at reduced emission levels. In this regard, natural gas exhibiting properties more similar to diesel, while operating at lower operating costs, resulting in lower emission levels to be an encouraging substitute to diesel fuel. Compared to diesel, CNG has a higher specific enthalpy that establishes its energy density per unit volume to be equivalent to corresponding diesel fuel expressed per unit mass basis. The comparison between its utilization and reserves has been found to be better off as compared diesel fuel, that clearly establishes the contention to be a sustainable fuel for future [6,7]. Renewable, sustainable, and alternative fuels have several advantages that include environmental benignity, conservative foreign exchange usage, and arrest socio-economic anxieties [8–10]. Fossil fuels are primary energy sources, but they are depleting in nature, and combustion of such fuels for power generation, resulting in hazardous environmental degradation. The higher standards of living, urbanization besides socio-economic development around the globe have worsened the environmental conditions, leading to epidemically poor air quality. There is an urgent need to look into the issues caused by the burning of fossil fuels. In this context, energy from renewable and sustainable fuels seems to be better for achieving the improved economy of any nation and standard of life [11,12]. Therefore, the utilization of biomass-derived fuels like biodiesel, biogas, hydrogen, producer gas, etc., dramatically contributes to sustainable waste management systems to eliminate or reduce the use of fossil fuels [13]. Energy management with high efficiency and lesser emission is significant for country development [14–16]. The government of India has been put into practice for the biomass power/co-generation program. In general, overall, approximately 500 projects on biomass-based power generation and cogeneration collecting to 4760 MW capability have been already established in India for maintaining power to the network. In India, the possibility of biomass is anticipated at almost 500 million metric tons annually. Studies showed that the Ministry had assessed additional biomass accessibility at about 120–150 million metric tons per annum, including both farming and forestry remainders corresponding to about 18,000 MW. Additionally, about 7000 MW added power could be created using waste bagasse-based cogeneration. This status indicates there is a tremendous amount of potential for harnessing energy from such renewable sources of energy. Hence, in the present energy scenario, power generation through biomass-derived fuels is of utmost importance. Power generation through the integrated gasifier-engine system using waste biomass or pallets/briquettes is necessary. To harness plenty of power through such devices, highly efficient power generation equipment’s production and skilled person’s development are essential [17–19]. Use of gaseous fuels such as compressed natural gas and hydrogenated compressed natural gas (HCNG) in a diesel engine is more attractive fuels [7,20,21]. Maximum energy from the natural gas can be harnessed when it is mixed with hydrogen; thereby, its flame speed further increased and leads to better and faster combustion. Energies 2020, 13, 5663 3 of 27

Das et al. [22] addressed development of hydrogen-powered CI engines. They have described the method of using hydrogen in diesel engines and addressed its advantages and disadvantages. Further, they have studied objectionable burning trends such as backfire, pre-ignition, knocking, and speedy pressure rise rate. In their work, an innovative and revolutionary viewpoint of the utilization of hydrogen in CI engines has been demonstrated gas operated diesel engines on dual fuel mode suffers from poor utilization of the gaseous fuel during combustion at lower and intermediate loads. Hence, they result in poor engine performance and emissions [23]. However, at higher loads, gaseous fuel performs better, leading to improved gaseous fuel utilization, engine performance, and higher CO level were observed in comparison with normal diesel operation [20,24–26]. Researchers have reported values of 20% to 30% higher thermal efficiency with the addition of hydrogen. This could be due to the increased flame speed of HCNG caused by the addition of Hydrogen, and hence the equivalence ratio is considerably greater than the stoichiometric situation, and distinct the burning of methane is not as steady as with a combination of H2-CNG [27]. Higher CO intensity under dual fuel mode has been described contrasted to normal diesel function styles even at higher loads, which signaled some flame extinction zones to exist [28,29]. High flame speed of hydrogen exists over an ample variety of temperatures and pressures, and higher flame speed causes an increase in the rate of pressure rise and combustion. The stratified combination procedure can be utilized to combust a lean combination when it is lesser than the lesser flammability limit of hydrogen. Hydrogen managed engines can have a durable and permanent flow of hydrogen without throttling as gaseous hydrogen has wide flammability [23,30–34]. The impact of injection timing, injection interval, and hydrogen substance on the burning aspects of a CI engine employed in the dual-fuel approach applying diesel and hydrogen manifold injection has been described. Engine function at the optimum start of injection at gas exchange Top Dead Centre (TDC) with an injection period of 30 ◦CA for an H2 flow rate of 7.5 lpm caused superior performance with appropriate levels of emission intensities [35–38]. Dimitriou et al. [39] investigated the hydrogen on the combustion of diesel-powered diesel engines functioned on a dual fuel approach. They have achieved a hydrogen energy share of up to 98% at low load operation. They observed that the carbon-based and NOx formation were dropped and 85% reduced soot level associated with the conventional diesel operation. They found increased NOx level at medium load and claimed that this may be due to high energy content of hydrogen. Serrano et al. [40] addressed energy efficiency enhancement and emissions reduction techniques by utilizing hydrogen in a diesel engine. They have studied engine operation at two velocities and numerous injection approaches. They have also addressed self-ignition, combustion knocking, and water was an injection in the intake manifold to reduce the NOx intensity. Increased NOx and smoke formations have been described with heightened hydrogen proportion. However, 30% of water injection resulted in 37% efficiency and lowered NOx emissions. Khan et al. [41] scrutinized the performance and emission qualities of a CI engine functioned on a dual fuel mode employing a B20 combination and analyzed the influence of injection pressure and hydrogen injection (15 lpm). They have operated the engine on dual fuel mode. They have diverged the injection pressure from 200 to 240 bar in steps of 20. They found minimum Specific Fuel Consumption (SFC) and maximum ηth with lowered emission concentrations at optimum injection pressure associated to the operation with other blends and injection pressures. Koten et al. [42] examined the influence of hydrogen on the performance and emissions of four cylinders, a water-cooled diesel engine. They have added hydrogen with air in the intake manifold, and hydrogen was used at various proportions (0.20, 0.40, 0.60, and 0.80 lpm). The researchers have reported on engine performance characteristics at varying loads under a constant 1800 rpm operation. It observed an increase in the exhaust gas temperature and NOx emissions at the addition of 0.80 lpm hydrogen and higher loads. With hydrogen addition, emissions levels such as smoke, HC, and CO were decreased with growing in NOx level. Liew et al. [43] observed an increase in the peak cyl pr. and the peak HRR when greater hydrogen was combined at high load. They observed a three-stage combustion process for the diesel–hydrogen operated dual-fuel engine associated with diesel engines two-stage burning development. Due to fuel diffusion combustion and the premixed hydrogen burning, multiple Energies 2020, 13, 5663 4 of 27 turbulent flames were developed, leading to amplified peak heat release. No change has been noticed when greater hydrogen was added at a low load. The use of hydrogen resulted in greater power to weight ratio associated with diesel-fueled function. However, it resulted in peak power and was found to be approximately 14% greater. For ensuring satisfactory combustion, they have adopted inlet air heating for the hydrogen-fueled engine, which in turn resulted in a greater peak in-cylinder pressure [43]. Exergy analysis has been carried out by [44]. The study revealed that available work at rated load increased from 29% to 32%. Reduction in irreversibility and lowered intensive entropy generation during combustion was reported to be the reason. Rakopoulos and Kyritsis [45] analyzed the second law of thermodynamics concerning hydrogen-fueled engines. They observed differences in the irreversibility generation during combustion between hydrogen and hydrocarbons. Entropy generation during the oxidation reaction of the two fuels is accountable for the remarked manner. They noticed that decreased burning irreversibility when hydrogen content was increased. Increased second law efficiency has been reported with increased hydrogen. Tarkanand Karagöz [46] studied diesel–hydrogen burning in a CI engine. They found a reduction in the indicated thermal efficiency and increased indicated specific fuel consumption when hydrogen energy fraction was increased. As far as emission concentrations were involved, smoke, CO, and CO2 were decreased with enlarging hydrogen proportion. At the 16% hydrogen energy fraction, no change in NOx formation has been reported. Loganathan and Velmurugan [47] modified the conventional diesel engine to operate on gas. They supplied hydrogen with exhaust gas recirculation through the intake. They injected hydrogen at an injection pressure of 2 bar with 2, 4, 6, 8 and 10 L/min. Combustion characteristics of an engine such as ignition delay, burning interval, rate of pressure rise (ROPR), heat release rate (HRR), cumulative heat release rate (CHR), and cyclic pressure fluctuations were reported. They found a decrease in the peak pressure and HRR with the expanded Exhaust Gas Recirculation (EGR) rate. Variations in cyclic pressure and the high burning period have been reported with EGR. Reduction in combustion irreversibility was reflected in Santoso et al. [48], who investigated Brake Specific Energy Consumption (BSEC), indicated efficiency, and Cylinder Pressure (CP). They observed that the addition of hydrogen led to a reduction in the peak CP and engine efficiency. The reaction growth was fluctuating, and the burning ratio of reaction was slower, as demonstrated by the Computational Fluid Dynamics (CFD) computation [49]. Some investigators have applied a diesel engine on dual fuel mode utilizing different biodiesel and gas (Liquified Petroleum Gas (LPG), CNG, hydrogen, biogas) combinations. Further, hydrogen-enriched gases like CNG, the low calorific value like producer gas have been used in dual fuel concepts with diesel, biodiesel injection to improve the performance and emission characteristics as well. Producer gas has a minimum calorific value that caused inadequate performance with expanded HC and CO formations. However, it created a substantial drop in smoke and NOx intensities [18,50]. In this context, researchers combined hydrogen in producer gas and introduced a combination into the cylinder employing an appropriate blending chamber. Yaliwal et al. [51] examined the impact of hydrogen in the producer gas-fueled dual-fuel engine. They integrated the hydrogen in the variety from 4–12 L/min and was introduced in the intake manifold. They detected that diminished de-rating with augmented brake thermal efficiency with lowered emission concentrations. Nevertheless, they realized an enlarge in NOx level and declined smoke, HC, and CO patterns. Nevertheless, they noticed an enlarge in the ignition delay with heightened cylinder pressure and HRR. Halewadimath et al. [52] described that the utilization of hydrogen injection in a producer gas powered diesel engine was provided an enhancement in the thermal efficiency with diminished emission quantities. In addition, they have adapted the conventional mechanical fuel injection system into common rail direct injection, and also substituted HCC into re-entrant CC (RCC). This modification additional expanded the ηth with substantial declines in emissions except for NOx formation. However, Yasin et al. [53] reported that lower heating value of hydrogen is higher than diesel fuel, but the decrease in volumetric efficiency reduced the torque and hence the power produced by the engine. Energies 2020, 13, 5663 5 of 27

In their study, the CRDI diesel engine with RCC was run on neem oil methyl ester-hydrogen-producer gas combination and at an injection timing 10◦ BTDC and IP of 800 bar. They reported that BTE was increased by 3.02% and smoke, HC, and CO were diminished by 22.4%, 12.2%, 10.8%, respectively, while the NOx soared by 18.6% in comparison with the similar fuel combination with HCC. Additional, expanded cylinder pressure and HRR were remarked. The literature survey on dual fuel engine concept with biodiesel (METP) and hydrogen utilization is limited to low pressure injection of the pilot fuels selected. Further, METP was not much investigated in dual fuel concept with hydrogen dosage. Use of high-pressure injection of viscous fuels of biodiesels coupled with higher calorific value hydrogen gas is not much investigated. Hence the present work discusses the combined effect of injection of both liquid and gaseous fuels on the performance of the modified diesel engine operated in dual fuel mode and the associated feasibility studies. Direct Injection and Port Injection use computer-controlled electric injectors to spray fuel into the engine. The difference is where they spray the fuel. Direct injection has the injectors mounted in the cylinder head and the injectors spray fuel directly into the engine cylinder. It then mixes with the air. Only air passes through the intake manifold runners and past the intake valves with direct injection. There are advantages and disadvantages of both systems. The advantages of direct injection is better fuel economy, less emissions, and better performance. Fuel economy improvements can be as much as 15%, allowing much less fuel to be wasted. It delivers fuel more precisely to increase better combustion with more power while maintaining better fuel economy and lowering emissions. A 25% emission drop at cold-start is possible. Direct injection meters the amount of fuel exactly into each cylinder for optimum performance and it’s sprayed under very high pressure, up to 15,000 PSI on some vehicles, so the fuel atomizes well and ignites almost instantly. The major drawback of direct injection is carbon buildup on the backside of the intake valves. This can throw a computer code, and could result with a ignition failure. The other disadvantage of direct injection is cost. The injector tips are mounted right into the combustion chamber, so the materials of the injector have to be very good quality. High pressure is needed to inject fuel directly into the cylinders which means expensive high-pressure fuel pumps are needed. They are typically mechanically driven from the engine, which adds to the complexity [54]. The extensive literature review mainly highlights the trial engine tests conducted on customized single cylinder, four stroke, water cooled and DI diesel engine operated on dual fuel mode with two varieties of CMFIS injection systems. The liquid fuel, such as METP, has been used as injected liquid pilot fuel with gaseous hydrogen supplied as manifold injected fuel at optimized engine parameters. The CMFIS dual-fuel engine was operated under optimum engine settings of 27◦ BTDC (Before Top Dead Centre), 240 bar injection pressure adopting a 5-hole injector with 0.2 mm orifice. The selection of an injector with fixed number of holes also depends on its compatibility with combustion chamber. In the present work, the injector is optimized with modified combustion chamber as well. The engine adopted re-entrant combustion chamber with dual-fuel operation on biodiesel and gaseous fuel. The engine parameters were optimized with respect to gaseous fuel flow rates, injection timing, injection duration and methods of gaseous fuel injection methodology. The use of hydrogen through injection facility in a biodiesel fueled dual fuel engine has been less investigated and reported. The presented work compares hydrogen injection and induction methods. The two fuels selected for investigations are nature based and renewable to make the initiative to be sustainable practice as it avoids use of fossil fuels. Major modification in the existing engines will require higher operating costs of the transportation. The present work helps in this direction by suitably adopting renewable energy technologies using minimum interventions in the existing diesel engine technology. Additionally, the present work suggests methods to fine tune the existing diesel engines used for the transportation sector without much burden on the cost of engine operation as well. Overall concept adopted strongly in line with the sustainable development goals envisaged by United Nation by year 2030 towards realization of eco-friendly power generation and utilization. Energies 2020, 13, 5663 6 of 27

2. Materials and Methods This section describes the fuels used and their properties along with the experimental setup used in the engine performance investigations.

2.1. Liquid and Gaseous Fuels Properties In the present investigation, two fuels were utilized viz, conventional fuel, and biodiesel obtained from Thevetia peruviana (B100) termed as METP. The biodiesel obtained from Thevetia peruviana belongs to the family of Apocynaceae, which is plentifully accessible in India. This plant is native of Central and South America, but now regularly cultivated during the steamy and sub-tropical areas. It is a classic humid shrub or tiny tree that holds yellow or orange-yellow, the flowers, and its fruit is deep red/black covering a sizeable seed that carries some similarity to a Chinese lucky nut. Figure1 indicates the fuels utilized in the CMFIS engine. The properties of fuels applied are shown in Tables1 and2. Additionally, hydrogen (H2) gas (purity 99.99%) was obtained from the BHORUKA GASES PVT.LTD., Bangalore. The hydrogen injection system has a suitable venture and is fitted inside the intake manifold to supply Hydrogen gas. The auto-ignition temperature of 858 K, flammability limits (% volume in air) of 4–75, stoichiometric air/fuel ratio on mass basis of 34.3, density at 15 ◦C and 1 bar (kg/m3) of 0.0838, net heating value (MJ/kg) of 119.93, and flame velocity (cm/s) of 265–325.

Table 1. Speciﬁcation of tested fuels.

Property D100 B100 ASTM Standard Density (kg/m3) 829 892 ASTM D5052 Viscosity at 40 C ◦ 3.52 5.748 —– (mm2/s) Flash point (◦C) 53 178 ASTM D93 Fire point (◦C) 59 188 ASTM D93 Caloriﬁc value (MJ/kg) 42.19 39.46 ASTM D5865 Cetane number 45–51 46 ASTM D675

Table 2. Properties of hydrogen.

Parameters Values

Chemical composition H2 Auto-ignition temperature (K) 858 K Minimum Ignition Energy (MJ) 0.02 Flammability limits (% Volume in Air) 4–75 Stoichiometric Air/Fuel Ratio on mass basis 34.3 3 Density at 15 ◦C and 1 bar (kg/m ) 0.0838 Net Heating value (MJ/kg) 119.93 Flame velocity (cm/s) 265–325 Octane number 130 EnergiesEnergies 20202020,, 1313,, x 5663 FOR PEER REVIEW 7 7of of 27 27

FigureFigure 1. 1. AA layout layout of of the the test test rig. rig.

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2.2. Engine Test Rig with CMFIS 2.2. Engine Test Rig with CMFIS Tests were performed using single cylinder, CI engine with a cylinder capacity of 660 CC, a compressionTests were ratio performed of 17.5, generating using single 5.2 kW cylinder, at 1500 CI rpm, engine and withits layout a cylinder is indicated capacity in Figure of 660 2, CC, as awell compression as its description ratio of demonstrates 17.5, generating in Table 5.2 kW 3. Th ate 1500 engine rpm, operates and its typicall layouty is at indicated 1500 rpm inspeed. Figure The2, ascompression well as its descriptionratio is adjusted demonstrates without inimpeding Table3. Thethe engineengine operatesand burning typically chamber at 1500 geometry rpm speed. by Thespecifically compression constructed ratio is tilting adjusted cylinder without block impeding arrangement. the engine The and setup burning encompasses chamber of geometry CI engine by specificallyconnected to constructed a dynamometer tilting for cylinder inserting block and applied arrangement. with numerous The setup devices encompasses for ignitions of CI pressure engine connectedand measurements to a dynamometer of crank angle. for inserting The signals and appliedinterfaced with across numerous the engine devices display for ignitions to the computer pressure andfor P-V measurements and P-θ diagrams. of crank angle. Sensors The signalsare utilized interfaced for air across and the fuel engine flow, display temperatures, to the computer and load for P-Vmeasurement. and P-θ diagrams. The system Sensors has are a utilized self-contained for air and panel fuel flow,case temperatures,covering of andair loadcase, measurement.manometer, Thetransmitters system has for a air self-contained and fuel flow panel measurements, case covering ofdoub airle case, fuel manometer, tanks utilized transmitters for dual for fuel air test, and fuel flowassessing measurements, unit, engine double indicator, fuel tanks and process utilized formarker. dual fuelRotameters test, fuel were assessing comprised unit, engine of cooling indicator, and andcalorimeter process marker.fluid flow Rotameters measurements. were comprised The syst ofem cooling permits and calorimetercompression fluid ratio flow alterations measurements. for Themeasurement system permits of mechanical compression efficiency, ratio alterations indicated forand measurement brake thermal of efficiency, mechanical volumetric efficiency, efficiency, indicated andas well brake as thermalbrake, indicated efficiency, and volumetric frictional epower,fficiency, Indicated as well asMean brake, Effective indicated Pressure and frictional (IMEP), power,Brake IndicatedMean Effective Mean EPressureffective Pressure(BMEP), (IMEP), heat balance, Brake Mean A/F Eratio,ffective and Pressure specific (BMEP), fuel consumption. heat balance, The A/F ratio,introduction and specific injector fuel pressure consumption. and injection The introduction timing, as stated injector by pressure the manufacturer, and injection respectively, timing, as statedis 205 bybar the and manufacturer, 23° BTDC. To respectively, evaluate the is impact 205 bar of and injection 23◦ BTDC. timings, To evaluate static timings the impact about of 19° injection BTDC timings,and 27° staticBTDC timings are utilized about apart 19◦ BTDC from andthe 27specified◦ BTDC inje arection utilized timing. apart The from comprehensive the specified injectionexamination timing. is Theperformed comprehensive in such a examinationmanner that isthe performed performance in such of the a mannerengine worsens that the performanceappreciably with of the retarded engine worsenstiming below appreciably 19° BTDC with and retarded advanced timing timing below abov 19e ◦27°BTDC BTDC. and The advanced injection timing timing above was maintained 27◦ BTDC. Theconstant injection at 23° timing BTDC, was and maintained the compression constant ratio at 23varied◦ BTDC, from and 15 theto 17.5. compression Figure 1 illustrates ratio varied the from layout 15 toof 17.5.the testbed. Figure 1 illustrates the layout of the testbed.

Figure 2. ToroidalToroidal re-entrant combustion chamber.

The governor is used to regulateTable the 3. engine Descriptions speed. of The the enginetest rig. incorporated with the combustion chamber of hemispherical shape with overhead valves works through pushrods. Engine cooling is Parameter Values carried by circulatingMake and coolant Model through the waterKirloskar, jackets TV1 on various components of the engine that require cooling.Engine The type pressure transducer of piezoelectricSingle cylinder, nature 4-S CI is installedengine with the surface of the cylinder head toCooling gauge system the cylinder pressure. Thewater common cooled rail or high-pressure collector is utilized to protect fuel atBore lifted X pressure.Stroke Up to this, the collector87.5 mm volume × 110 mm needs to keep up the pressure changes brought by fuelDisplacement pulses and conveyedVolume by pump and660 fuel-injection cc cycles. This guarantees that, when the injector opens,Compression infusion weight Ratio stays steady. On17.5 the other hand, the aggregator volume ought to be suﬃciently massiveCombustion to suit Chamber this necessity, and theOpen other Chamber hand, it (Direct must beInjection) suﬃciently little to give a fast Rated Power 5.2 kW weight increment on motor begin. Figure2 shows the toroidal reentrant combustion chamber shape. Rated Speed 1500 rpm

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At the beginning of the experimentation, a consequence of EGR on the performance of METP-hydrogen fuelled dual-fuel engine with hydrogen injection using the Manifold method has been considered. The percentage of EGR was ﬁxed at 20% for this case based on the results obtained on METP-Hydrogen dual-fuel engine operation, in which hydrogen was inducted earlier, and accordingly, the percentage of EGR was ﬁxed at 20% for the study.

Table 3. Descriptions of the test rig.

Parameter Values Make and Model Kirloskar, TV1 Engine type Single cylinder, 4-S CI engine Cooling system water cooled Bore X Stroke 87.5 mm 110 mm × Displacement Volume 660 cc Compression Ratio 17.5 Combustion Chamber Open Chamber (Direct Injection) Rated Power 5.2 kW Rated Speed 1500 rpm Air measurement manometer Make MX 201 Type U-type Range 100-0-100 mm Eddy current dynamometer Model AG-10 Type Eddy current Maximum Engine Power 7.5 kW at 1500–3000 rpm Flow Flow through dynamometer Dynamometer arm length 0.180 m Fuel measuring unit range 0–50 mL

2.3. Manifold Injection System A pressure regulator with two-stage is fitted on the Hydrogen gas cylinder that supplies hydrogen at 2 bar. Hydrogen was permitted to flow across a rotameter that is calibrated to provide an identified flow rate of the metered gas. Flashback arrester, flame arrester, and wet type flame trap were linked end to end to avoid fire hazards and induct the metered gas into the intake manifold. The hydrogen quantity rate flow rate was varied from 0.10 to 0.25 kg/h. Hydrogen is extremely inflammable, and thus a flashback arrester (acts as a non-return valve) was applied. The wet type of flame trap extinguishes any accidental flame flowing back into the gas supply side. A flame arrester is also utilized in the investigation. The hydrogen injector utilized has the terms as presented in Table4. The engine is conducted with a pilot injection of METP whilst H2-gas was inserted in the inlet manifold and port (dual fuel mode). The flow rate of the liquid fuel is controlled spontaneously as the engine is self-governed. The flow rate of hydrogen gas is modified for the applied load safeguarding smooth engine function devoid of any knock. The hydrogen gas manifold and port injection system utilize an applicable ECU. The ECU secures the signal around the TDC arrangement across the infrared sensor to monitor the hydrogen gas injection timing. The hydrogen gas injector is a solenoid type and employs a 12 V battery for power supply.

Table 4. Descriptions of the hydrogen injector.

Make Quantum Technologies Operating Voltage 8 V DC~16 V DC Peak Current level 4.0 A Holding current level 1.0 A Max. operating pressure 345 kPa (50 psi) Working Pressure 103–345 kPa Energies 2020, 13, 5663 10 of 27

HRR was calculated based on the ﬁrst law of thermodynamics,

Energies 2020, 13, x FOR PEER REVIEW γ 1 10 of 27 Qa = [PdV] + [Vdp] + Q γ 1 γ 1 wall − − HRR was calculated based on the first law of thermodynamics, where, 𝛾 1 𝑄 𝑃𝑑𝑉 𝑉𝑑𝑝 𝑄𝑤𝑎𝑙𝑙 𝛾1 𝛾1 Q —Apparent heat release rate, J awhere, V—Instantaneous volume of the cylinder (m3) P—CylinderQa—Apparent pressure heat release (bar) rate, J V—Instantaneous volume of the cylinder (m3) Q —Heat transfer to the wall (J) wallP—Cylinder pressure (bar) Qwall—Heat transfer to the wall (J) h i Qwall = h A Tg Tw 𝑄 ℎ × 𝐴 𝑇× −𝑇 h—Heat transfer coeﬃcient in W/m2 K T—Cylinderh—Heat transfer gas temperature coefficient in in W/m K 2 K A—InstantaneousT—Cylinder gas Areatemperature (m2) in K A—Instantaneous Area (m2) The Figure3 shows the schematic layout of the test facility adopted for the investigations on dual The Figure 3 shows the schematic layout of the test facility adopted for the investigations on fuel mode operation of CI engine with Hydrogen injection. The diagram provides details of various dual fuel mode operation of CI engine with Hydrogen injection. The diagram provides details of measurement equipment for engine operation with initial conditions of injection set to TDC, 5 ATDC, various measurement equipment for engine operation with initial conditions of injection set to ◦TDC, 10 ATDC, 15 ATDC, and injection ON time (i.e., injection duration) of 30, 60, and 90 deg. CA for ◦5° ATDC, 10°◦ ATDC, 15° ATDC, and injection ON time (i.e., injection duration) of 30, 60, and 90 deg. HydrogenCA for Hydrogen under optimized under optimized level. The level. hydrogen The ﬂowhydrogen rate wasflow adopted rate was to adopted be 0.25 kgto/ hbe incorporating 0.25 kg/h optimumincorporating injection optimum time for injection hydrogen time throughfor hydrogen a series through of investigative a series of investigative trials. Figure trials.4 indicates Figure the4 dual-fuelindicates engine the dual-fuel test rig engine provided test with rig provided hydrogen with injections. hydrogen injections.

FigureFigure 3. 3.Schematic Schematic lineline diagramdiagram for dual fuel fuel mode mode with with hydrogen hydrogen injection. injection.

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Figure 4. PhotographicPhotographic view of dual fuel engine te testst rig provided with hydrogen injection.

3. Results and Discussion The salientsalient results results obtained obtained through through the extensivethe exte experimentalnsive experimental observations observations have been have discussed been withdiscussed respect with to consequencesrespect to consequences of various start of various of injection start (SOI)of injection and injection (SOI) and duration injection (ID) duration for hydrogen (ID) operationfor hydrogen under operation manifold under injection. manifold Facilities injection. were Facilities established were for established Hydrogen injectionfor Hydrogen into the injection engine inletinto the manifold engine asinlet well manifold as the port.as well For as this,the port. a low For pressure this, a low (5 bar) pressure solenoid (5 bar) hydrogen solenoid nozzle hydrogen was utilizednozzle was to injectutilized hydrogen to inject into hydrogen the inlet into manifold the inlet and manifold port using and anport electronic using an control electronic unit control (ECU). Furtherunit (ECU). experiments Further experiments were performed were on performed a dual-fuel on engine a dual-fuel with aengine pilot injection with a pilot of METP injection at optimized of METP injectionat optimized timing injection of 27◦ timingBTDC, of 240 27° bar BTDC, IP, CR 240 17.5, bar IP, and CR an 17.5, engine and speed an engine of 1500 speed pm. of For 1500 hydrogen pm. For SOIhydrogen were keptSOI were at TDC, kept 5◦ at, 10 TDC,◦, and 5°, 15 10°,◦ ATDC and 15° in bothATDC the in versions both the ofversions a manifold of a manifold and port injection.and port Theinjection. SOI beyondThe SOI 15 beyond◦ ATDC 15° resulted ATDC in resulted engine knocking,in engine knocking, and hence and the hence results the are results not presented are not forpresented this case. for Hydrogenthis case. Hydrogen injection durationinjection (ONduration time) (ON was time) selected was fromselected as 30from to 90as ◦30CA toin 90 steps °CA ofin 30steps◦CA. of 30 The °CA. characteristics The characteristics (i.e., performance, (i.e., performa emission,nce, emission, and burning) and burning) of the dual-fuel of the dual-fuel engine has engine been investigatedhas been investigated when fuelled when with fuelled Hydrogen-Diesel with Hydrogen-Diesel/METP/METP combination. combination. The hydrogen The hydrogen flow rate flow was maintainedrate was maintained at 0.25 kg at/h, 0.25 and kg/h, METP and was METP applied was as applied pilot injected as pilot fuel. injected fuel. 3.1. Impact of EGR on the Implementation of METP-Hydrogen-Powered Dual-Fuel Engine with 3.1. Impact of EGR on the Implementation of METP-Hydrogen-Powered Dual-Fuel Engine with Hydrogen Hydrogen Introduction Introduction The effect of EGR on the ηth for Diesel/METP-hydrogen dual-fuel function is shown in Figure5. The effect of EGR on the ηth for Diesel/METP-hydrogen dual-fuel function is shown in Figure 5. It is evident from Figure5 that the BTE reduces with increasing EGR rates. This could be ascribed to It is evident from Figure 5 that the BTE reduces with increasing EGR rates. This could be ascribed to the fact that the mixture was diluted when burnt gas was mixed; hence it results in increased HC and the fact that the mixture was diluted when burnt gas was mixed; hence it results in increased HC and CO emission levels. Additionally, drastic changes in the specific heat of a charge during compression CO emission levels. Additionally, drastic changes in the specific heat of a charge during compression and expansion are responsible for the results observed. The presence of EGR in the charge decreases and expansion are responsible for the results observed. The presence of EGR in the charge decreases inlet charge temperature resulting in decreased BTE. All factors mentioned and along with the thermal inlet charge temperature resulting in decreased BTE. All factors mentioned and along with the effect of EGR, significantly vary the combustion characteristics. Further, when part of the exhaust thermal effect of EGR, significantly vary the combustion characteristics. Further, when part of the gas was admitted to the engine through the intake manifold, it replaces the equal amount of intake exhaust gas was admitted to the engine through the intake manifold, it replaces the equal amount of air. This leads to decreased air-fuel ration and chemical kinetics and affects the dual-fuel engine intake air. This leads to decreased air-fuel ration and chemical kinetics and affects the dual-fuel combustion negatively. Further these results into decreased BTE due to reduced volumetric efficiency. engine combustion negatively. Further these results into decreased BTE due to reduced volumetric efficiency.

Energies 2020, 13, 5663 12 of 27 Energies 2020, 13, x FOR PEER REVIEW 12 of 27

Figure 5. EffectEﬀect of of Exhaust Exhaust Gas Gas Recirculation Recirculation (EGR) (EGR) on on the the Brake Thermal Efficiency Eﬃciency (BTE) with inductioninduction method.

For the the same same EGR EGR rates, rates, decreased decreased BTE BTE was wasobtained obtained for METP-Hydrogen for METP-Hydrogen compared compared to diesel– to hydrogen.diesel–hydrogen. For the For similar the similar injected injected fuel fuelduring during dual dual fuel fuel process process hydrogen hydrogen injection, injection, improved improved performance has been observed. This may be due to the higher flameflame velocity of H22. In In this this hydrogen hydrogen injectioninjection method method using using EGR, EGR, decreased decreased BTE BTE has has been been no noticedticed that that is is caused caused by by the the effect effect of inactive radicals present in tire out exhaust gas. Further, Further, it it decreases decreases the the combustion combustion process process by by the the increased increased temperaturetemperature of charge charge in in the the combustion combustion chamber, chamber, leading leading to to reduced reduced volumetric volumetric efficiency. efficiency. The EGR EGR effecteffect on the smoke opacity for dieseldiesel/METP-Hydrogen/METP-Hydrogen injection is presented in Figure6 6.. IncreasedIncreased smoke opacity has been noticed with the addition of EGR in the injection injection of hydrogen. The The utilization utilization of EGR in a dualdual fuelfuel engineengine doesdoes not not outcome outcome any any improvements improvements in in smoke smoke emission. emission. The The presence presence of ofexhaust exhaust gas gas significantly significantly decreases decreases air proportionately,air proportionately, leading leading to a reductionto a reduction in the in oxidation the oxidation rates. rates.However, However, hydrogen hydrogen use in theuse combustionin the combusti alongon with along EGR with marginally EGR marginally decreases decreases smoke emission. smoke emission.This may beThis attributed may be attributed to increased to increased ignition centers ignition caused centers by caused the higher by the flame higher velocity flame of velocity hydrogen. of hydrogen.A lower percentage A lower percentage of exhaust gasof exhaust (5% and gas 10%) (5% changes and 10%) the changes smoke emission the smoke marginally emission compared marginally to comparedthe operation to withthe operation higher EGR with rates higher (15% EGR and 20%).rates Hydrogen(15% and domination20%). Hydrogen during domination lower EGR during rates is lowerbetter EGR compared rates is to better higher compared EGR rates to caused higher byEGR the rates higher caused flame by velocity. the higher When flame the velocity. percentage When of theEGR percentage was increased, of EGR leading was toincreased, an increase leading in the to smoke an increase opacity, in owing the tosmoke a reduction opacity, in owing the air-fuel to a reductionratio. Hydrogen in the air-fuel injection ratio. leads Hydrogen to better soot injection oxidation leads due to better to the soot utilization oxidation of available due to the air. utilization However, ofa negativeavailable e ffair.ect However, on the smoke a negative levels witheffect EGR on the has smoke been observed.levels with EGR has been observed. The effect of EGR on HC and CO levels for diesel/METP-hydrogen injection is demonstrated in Figures7 and8. The presence of HC and CO in the exhaust indicates the quality of burning. A high proportion of such emissions clearly shows the incomplete combustion of fuel. The addition of exhaust gas further lowers the air-fuel ratio leading to dilute and reduce the strength of the mixture caused by the decrease of oxygen concentration. This results in decreased combustion temperature and resulting in higher HC and CO concentrations in the exhaust. The higher amount of HC and CO is due to retarded oxidation rates, and hence HC and CO formation is more dominant at light loads in dual-fuel operation. Use of a lower percentage of exhaust gas (5% and 10%) mixing results into marginal changes in the HC and CO concentrations compared with higher EGR rates (15% and 20%). At higher EGR rates, the air-fuel ratio changes drastically, leading to incomplete combustion. However, the use of hydrogen injection with EGR leads to greater utilization of air at the time of fuel combustion. This can at least lower the both HC and CO emissions due to better utilization of air and higher flame velocity of hydrogen. Further increased ignition delay during dual fuel operation may also be compensated by hydrogen presence.

Figure 6. Influence of EGR on the smoke opacity with induction method.

Energies 2020, 13, x FOR PEER REVIEW 12 of 27

Figure 5. Effect of Exhaust Gas Recirculation (EGR) on the Brake Thermal Efficiency (BTE) with induction method.

For the same EGR rates, decreased BTE was obtained for METP-Hydrogen compared to diesel– hydrogen. For the similar injected fuel during dual fuel process hydrogen injection, improved performance has been observed. This may be due to the higher flame velocity of H2. In this hydrogen injection method using EGR, decreased BTE has been noticed that is caused by the effect of inactive radicals present in tire out exhaust gas. Further, it decreases the combustion process by the increased temperature of charge in the combustion chamber, leading to reduced volumetric efficiency. The EGR effect on the smoke opacity for diesel/METP-Hydrogen injection is presented in Figure 6. Increased smoke opacity has been noticed with the addition of EGR in the injection of hydrogen. The utilization of EGR in a dual fuel engine does not outcome any improvements in smoke emission. The presence of exhaust gas significantly decreases air proportionately, leading to a reduction in the oxidation rates. However, hydrogen use in the combustion along with EGR marginally decreases smoke emission. This may be attributed to increased ignition centers caused by the higher flame velocity of hydrogen. A lower percentage of exhaust gas (5% and 10%) changes the smoke emission marginally compared to the operation with higher EGR rates (15% and 20%). Hydrogen domination during lower EGR rates is better compared to higher EGR rates caused by the higher flame velocity. When the percentage of EGR was increased, leading to an increase in the smoke opacity, owing to a reductionEnergies 2020 in, 13 the, 5663 air-fuel ratio. Hydrogen injection leads to better soot oxidation due to the utilization13 of 27 of available air. However, a negative effect on the smoke levels with EGR has been observed.

Energies 2020, 13, x FOR PEER REVIEW 13 of 27 Energies 2020, 13, x FOR PEER REVIEW 13 of 27 The effect of EGR on HC and CO levels for diesel/METP-hydrogen injection is demonstrated in The effect of EGR on HC and CO levels for diesel/METP-hydrogen injection is demonstrated in Figures 7 and 8. The presence of HC and CO in the exhaust indicates the quality of burning. A high Figures 7 and 8. The presence of HC and CO in the exhaust indicates the quality of burning. A high proportion of such emissions clearly shows the incomplete combustion of fuel. The addition of proportion of such emissions clearly shows the incomplete combustion of fuel. The addition of exhaust gas further lowers the air-fuel ratio leading to dilute and reduce the strength of the mixture exhaust gas further lowers the air-fuel ratio leading to dilute and reduce the strength of the mixture caused by the decrease of oxygen concentration. This results in decreased combustion temperature caused by the decrease of oxygen concentration. This results in decreased combustion temperature and resulting in higher HC and CO concentrations in the exhaust. The higher amount of HC and CO and resulting in higher HC and CO concentrations in the exhaust. The higher amount of HC and CO is due to retarded oxidation rates, and hence HC and CO formation is more dominant at light loads is due to retarded oxidation rates, and hence HC and CO formation is more dominant at light loads in dual-fuel operation. Use of a lower percentage of exhaust gas (5% and 10%) mixing results into in dual-fuel operation. Use of a lower percentage of exhaust gas (5% and 10%) mixing results into marginal changes in the HC and CO concentrations compared with higher EGR rates (15% and 20%). marginal changes in the HC and CO concentrations compared with higher EGR rates (15% and 20%). At higher EGR rates, the air-fuel ratio changes drastically, leading to incomplete combustion. At higher EGR rates, the air-fuel ratio changes drastically, leading to incomplete combustion. However, the use of hydrogen injection with EGR leads to greater utilization of air at the time of fuel However, the use of hydrogen injection with EGR leads to greater utilization of air at the time of fuel combustion. This can at least lower the both HC and CO emissions due to better utilization of air and combustion. This can at least lower the both HC and CO emissions due to better utilization of air and higher flame velocity of hydrogen. Further increased ignition delay during dual fuel operation may higher flame velocity of hydrogen. Further increased ignition delay during dual fuel operation may also be compensated by hydrogen presence. also be compensated by hydrogen presence. FigureFigure 6. InfluenceInﬂuence of of EGR EGR on on the the smoke smoke opacity opacity with with induction method.

CMFIS: Diesel-Hydrogen 70 Speed:CMFIS: 1500 rpm, pilot fuel, IT: 27obTDC, METP-HydrogenDiesel-Hydrogen o 70 IOP:205(D),Speed: 1500 240rpm, bar pilot (METP), fuel, IT: CR:17.5, 27 bTDC, METP-Hydrogen TRCC,IOP:205(D), Hydrogen 240 barflow (METP), rate: 0.25 CR:17.5, kg/h TRCC, Hydrogen flow rate: 0.25 kg/h 60 60

50 50

Hydrocarbon (ppm) 40 Hydrocarbon (ppm) 40

30 30

0 5 10 15 20 0 5Percentage 10 of EGR 15 20 Percentage of EGR

Figure 7. Influence of EGR on the HC with the induction method. Figure 7. InfluenceInﬂuence of EGR on the HC with the induction method. 0.25 0.25 CMFIS: Diesel-Hydrogen Diesel-Hydrogen Speed:CMFIS: 1500 rpm, pilot fuel, IT: 27obTDC, METP-Hydrogen o METP-Hydrogen IOP:205(D),Speed: 1500 240rpm, bar pilot (METP), fuel, IT: CR:17.5, 27 bTDC, 0.20 IOP:205(D), 240 bar (METP), CR:17.5, 0.20 TRCC, Hydrogen flow rate: 0.25 kg/h TRCC, Hydrogen flow rate: 0.25 kg/h

0.15 0.15

0.10 0.10 Carbon monoxide (% Vol.) monoxide (% Carbon

Carbon monoxide (% Vol.) monoxide (% Carbon 0.05 0.05

0.00 0.00 0 5 10 15 20 0 5 10 15 20 Percentage of EGR Percentage of EGR Figure 8. InfluenceInﬂuence of of EGR EGR on CO with injection method. Figure 8. Influence of EGR on CO with injection method. Figure 9 represents the consequence of EGR on the nitrogen oxide (NOx) formation for METP- Figure 9 represents the consequence of EGR on the nitrogen oxide (NOx) formation for METP- hydrogen operation. The hydrogen injection method with EGR induction may lead to a deficiency in hydrogen operation. The hydrogen injection method with EGR induction may lead to a deficiency in

Energies 2020, 13, 5663 14 of 27 Energies 2020, 13, x FOR PEER REVIEW 14 of 27

oxygenFigure concentration9 represents during the consequence combustion of leading EGR onto lower the nitrogen combustion oxide temperature. (NOx) formation This causes for a METP-hydrogendecrease in NOx operation. levels in the The exhaust. hydrogen In dual injection fuel strategy method with with high EGR EGR induction rates (15–20%), may lead NOx to levels a deficiencywere reduced in oxygen compared concentration to lower during EGR rates combustion (5–10%). leading For the to dual-fuel lower combustion operation temperature.with hydrogen Thisinjection causes and a decrease at lower in EGR NOx rates, levels comparatively in the exhaust. increased In dual NOx fuel levels strategy were with observed high EGRcompared rates to (15–20%),lower load. NOx At levels low were loads, reduced little quantity compared of topilot lower is used, EGR leading rates (5–10%). to lower For the the flame dual-fuel speed. operation This may withresult hydrogen in incomplete injection andcombustion; at lower EGRhence rates, lower comparatively NOX levels increased were observed NOx levels in the were exhaust observed gas. comparedAdditionally, to lower low load. combustion At low loads, temperature little quantity caused of by pilot the isdiminished used, leading adiabati to lowerc flame the temperature flame speed. is Thisaccountable may result for in incompletethis propensity. combustion; Nonetheless, hence fo lowerr 15% NO EGRX levels rates were and observedbeyond 15% in the EGR, exhaust NOx gas.levels Additionally,were reduced low caused combustion by the temperatureincreased mixture caused dilution by the diminishedand oxygen adiabatic deficiency. flame temperature is accountable for this propensity. Nonetheless, for 15% EGR rates and beyond 15% EGR, NOx levels were reduced caused by the increased mixture dilution and oxygen deficiency.

2400 CMFIS: Diesel-Hydrogen o 2200 Speed: 1500 rpm, pilot fuel, IT: 27 bTDC, METP-Hydrogen IOP:205(D), 240 bar (METP), CR:17.5, 2000 TRCC, Hydrogen flow rate: 0.25 kg/h 1800 1600 1400

1200 1000

Nitrogen oxide (ppm) oxide Nitrogen 800 600 400 200 0 0 5 10 15 20 Percentage of EGR

Figure 9. Influence of EGR on the NOX with induction method. 3.2. Impact of Hydrogen StartFigure of Injection 9. Influence and of its EGR Injection on the Interval NOX with with induction a Fixed 20%method. EGR on the Performance of METP-Hydrogen Fueled Dual-Fuel Engine with Hydrogen Using the Manifold Injection Method 3.2. Impact of Hydrogen Start of Injection and its Injection Interval with a Fixed 20% EGR on the PerformanceIn this section, of METP-Hydrogen the impact of hydrogen Fueled Dual-Fuel starts of Engi injection,ne with and Hydrogen its injection Using duration the Manifold was optimizedInjection forMethod dual fuel engine procedure employing diesel/METP as injected fuels. Experimental investigations have been carried out to achieve comparative measures in conditions of performance and emissions. The effectIn ofthis hydrogen section, injectionthe impact timing of hydrogen and injection starts duration of injection, on brake and thermal its injection efficiency duration (BTE) ofwas dual-fueloptimized engine for powereddual fuel with engine diesel procedure/METP-hydrogen employin usingg diesel/METP CMFIS facilities as injected is presented fuels. inExperimental Figure 10 forinvestigations 80% load, respectively. have been carried Further, out hydrogen to achieve was comparative injected (manifold) measures atin variedconditions injection of performance timings andand injection emissions. duration The foreffect 80% of load.hydrogen BTE forinjection METP-hydrogen timing and operation injection isduration observed on to brake be smaller thermal contrastedefficiency to (BTE) diesel–hydrogen of dual-fuel operation. engine powered Hydrogen with properties diesel/METP-hydrogen being common, injected using CMFIS pilot fuel facilities assets is competepresented for ain significant Figure 10 responsibilityfor 80% load, respectively. on the observed Further, varied hydrogen trends. Lowerwas injected Cv and (manifold) higher viscosity at varied of METPinjection caused timings lowered and injection the engine duration performance for 80% when load. compared BTE for METP-hydrogen to diesel–hydrogen operation operation. is observed With theto manifold be smaller injection, contrasted enhanced to diesel–hydrogen combustion occurs operat dueion. to Hydrogen improved properties air-hydrogen being mixing common, that injected takes placepilot before fuel assets the mixture compete enters for a thesignificant engine cylinder.responsibility Further, on the the observed electronic varied injection trends. of hydrogen Lower Cv in and thehigher manifold viscosity offers theof METP greatest caused benefit lowered towards precisethe engine control performance of the amount when of Hydrogencompared enteringto diesel– intohydrogen the intake operation. of the engine. With the However, manifold manifoldinjection, injectionenhanced of combustion hydrogen leadsoccurs to due better to improved mixing of air- hydrogenhydrogen with mixing air caused that bytakes the place more timebefore available the mixture for hydrogen enters the to mix engine with cylinder. air leading Further, to better the combustion.electronic injection However, of gashydrogen injector in plays the manifold a major of rolefers in the injection greatest and benefit is responsible towards precise for improved control of enginethe amount performance. of Hydrogen Additionally, entering hydrogen into the hasintake the of highest the engine. flame However, velocity leading manifold to increasedinjection of burninghydrogen of the leads complete to better fuel mixing combination. of hydrogen Outcomes with ai exhibitedr caused that by the METP-Hydrogen more time available dual-fuel for hydrogen engine to mix with air leading to better combustion. However, gas injector plays a major role in injection and is responsible for improved engine performance. Additionally, hydrogen has the highest flame

Energies 2020, 13, x FOR PEER REVIEW 15 of 27 Energies 2020, 13, 5663 15 of 27 velocity leading to increased burning of the complete fuel combination. Outcomes exhibited that METP-Hydrogen dual-fuel engine procedure with manifold injection was found to be smooth for procedureselected injection with manifold timings injectionwhen varied was foundfrom TDC to be to smooth 15° ATDC. for selected As the injectionSOI was timingsvaried from when TDC varied to from10° ATDC, TDC to the 15 ◦performanceATDC. As the was SOI improved, was varied and from beyond TDC to 15° 10 ◦ATDC,ATDC, a thedrop performance in BTE was was observed improved, for anddual beyond fuel engine 15◦ ATDC, operation. a drop An in increase BTE was in observed BTE might for dualbe ascribed fuel engine to enhancement operation. An in increase the hydrogen in BTE mightmixing be rate ascribed with air, to enhancementand subsequently, in the improved hydrogen combustion mixing rate is with followed air, and by subsequently, significant combustion improved combustionrates associated is followed with higher by significantflame velocities combustion of hydrogen rates and associated could be with responsible higher flame for the velocities presented of hydrogenresults. At and 15° couldATDC, be the responsible maximum for flame the presented speed achievable results. At during 15◦ ATDC, stoichio themetric maximum combustion flame speed may achievablebe reduced duringas at 10° stoichiometric ATDC, an appreciable combustion amount may be of reduced METP asair atmixture 10◦ ATDC, is already an appreciable prepared amount during ofthe METP delay airperiod mixture and iscombusts already preparedthe mixture during rapidly, the delay giving period higher and rates combusts of in-cylinder the mixture pressures rapidly, in givingthe engine higher cylinder rates of[42]. in-cylinder At 15° ATDC, pressures decreased in the BTE engine could cylinder be due [42 to]. some At 15 of◦ ATDC,the hydrogen decreased injected BTE couldnot burning be due in to the some engine of the cylinder hydrogen and injected persisting not burninginto the inexhaust the engine and leaving cylinder the and engine persisting unburnt into thedue exhaustto its higher and auto-ignition leaving the engine temperature. unburnt For due any to given its higher SOI for auto-ignition hydrogen injection temperature. duration For of any 60 given°CA caused SOI for higher hydrogen BTE injection and could duration be anticipated of 60 ◦CA to caused additional higher period BTE and available could befor anticipated the uniform to additionalcombination period of hydrogen available with for air. the This uniform further combination leads to better of hydrogen burning withtaking air. place This inside further the leads engine to bettercylinder. burning Finally, taking it is concluded place inside that the the engine burning cylinder. was noticed Finally, to itbe is smoother concluded with that injection the burning timing was of noticed10° ATDC to be and smoother injection with duration injection of timing 60 °CA, of 10 an◦ dATDC these and were injection optimized duration for ofhydrogen 60 ◦CA, andmanifold these wereinjection optimized for the fordual-fuel hydrogen engine. manifold injection for the dual-fuel engine.

Figure 10. BTE for manifold injection of hydrogen in CMFIS based dual fuel engine.

This section is highlighted the various emission levels of the dual-fuel engine provided with CMFIS facilitiesfacilities and and operated operated on METP-hydrogenon METP-hydrogen with ECUwith controlledECU controlled manifold manifold injection ofinjection hydrogen. of Thehydrogen. variation The of variation smoke emissions of smoke for emissions various hydrogenfor various injection hydrogen timing injection and injection timing and interval injection with CMISinterval for with diesel CMIS/RuOMR-hydrogen-powered for diesel/RuOMR-hydrogen-powe dual-fuelred engine dual-fuel at 80% engine load isat presented 80% load inis presented Figure 11. Further,in Figure hydrogen 11. Further, was hydrogen injected (manifold) was injected at varied (manifold) injection at varied timings injection and injection timings duration and injection for 80% load.duration For similarfor 80% working load. For situations, similar working higher smoke situatio concentrationsns, higher smoke were concentrations remarked for METP-Hydrogen were remarked infor comparison METP-Hydrogen to conventional in comparison oil-hydrogen to conventional operation. oil-hydrogen This might be operation. ascribed toThis diﬀ mighterences be in ascribed injected pilotto differences fuel properties in injected such aspilot higher fuel viscosityproperties and su lowerch as higher volatility viscosity of the METPand lower [55]. volatility As the SOI of wasthe variedMETP [55]. from As TDC the toSOI 10 was◦ ATDC varied smoke from opacityTDC to 10° decreased. ATDC smoke The higher opacity BTE decreased. at these The SOIs higher could BTE be responsibleat these SOIs for could the resultsbe responsible obtained. for Hydrogen the result injections obtained. at Hydrogen 10◦ ATDC injection with CMFIS at 10° facility ATDC results with inCMFIS higher facility peak pressureresults in and higher burning peak temperaturespressure and prevailing burning temperatures inside the combustion prevailing chamber inside the at thecombustion injection chamber moment. at Beyond the injection 15◦ ATDC, moment. smoke Be opacityyond 15° is increased, ATDC, smoke probably opacity due tois incompleteincreased,

Energies 2020, 13, 5663 16 of 27 Energies 2020, 13, x FOR PEER REVIEW 16 of 27 combustionprobably due arising to incomplete from improper combustion air-hydrogen arising fr mixing.om improper For all air-hydrogen SOIs injection mixing. duration For of all 60 SOIs◦CA showedinjection lowered duration smoke of 60 opacity.°CA showed Decreasing lowered or increasingsmoke opacity. the injection Decreasing duration or increasing concerning the 60 injection◦CA has notduration much concerning eﬀect on the 60 smoke °CA has opacity not much reduction. effect Injection on the smoke duration opacity with 60reduction.◦CA resulted Injection in a sudurationﬃcient timewith availability60 °CA resulted for uniform in a sufficient mixing oftime both availability hydrogen for and uniform air [22,23 mixing]. It is concludedof both hydrogen that Hydrogen and air SOI[22,23]. 10◦ ItATDC is concluded and injection that Hydrogen duration SOI of60 10°◦ CAATDC led and to uniform injection mixing duration of hydrogenof 60 °CA led with to air.uniform This couldmixing lead of hydrogen to better oxidationwith air. This of the could fuel lead mixture, to be leadingtter oxidation to better of the cracking fuel mixture, of the fuel leading combinations to better usedcracking [42]. of In the addition, fuel combinations Hydrogen has used no [42]. carbon, In addition, and hence Hydrogen this factor has might no carbon, also be accountableand hence this for thefactor remarked might also manner. be accountable for the remarked manner.

Figure 11.11. SmokeSmoke opacity opacity for for manifold manifold injection injection of hydrogen of hydrogen in conventional in conventional mechanical mechanical fuel injections fuel (CMFIS)injections based (CMFIS) dual-fuel based engine.dual-fuel engine.

Figure 12 shows the emissions of HC of a dual-fueldual-fuel engineengine fueledfueled withwith dieseldiesel/METP-hydrogen/METP-hydrogen operation inin whichwhich diesel diesel and and METP METP were were injected injected using using both CMFIS.both CMFIS. Further, Further, Hydrogen Hydrogen was injected was (manifold)injected (manifold) at varied at injection varied timings injection and timings injection and duration injection for duration 80% load. for Findings 80% load. demonstrated Findings thatdemonstrated hydrogen injectionthat hydrogen with diesel injection resulted with indiesel lower resulted HC intensity in lower associated HC intensity with METP-Hydrogen associated with operation.METP-Hydrogen This might operation. be assigned This might to the be poor assigned burning to characteristics the poor burning of METP characteristics compared of to METP diesel. Dicomparedfferent injection to diesel. timings Different and injection injection timings durations and with injection CMFIS durations facility resulted with CMFIS in diff facilityerent HC resulted levels. Asin different the SOI ofHC hydrogen levels. As was the varied SOI of from hydrogen TDC towas 10 ◦variedATDC, from HC TDC emission to 10° was ATDC, decreased. HC emission The higher was BTEdecreased. and reduced The higher wall BTE wetting and reduced at these wall SOIs wetting could be at responsiblethese SOIs could for the be resultsresponsible obtained. for the Beyond results 15obtained.◦ ATDC, Beyond HC emission 15° ATDC, is increased, HC emission probably is dueincreased, to incomplete probably combustion due to incomplete arising from combustion improper air-hydrogenarising from improper mixing. Forair-hydrogen all SOIs, the mixing. injection For durationall SOIs, ofthe 60 injection◦CA showed duration lower of HC.60 °CA Decreasing showed orlower increasing HC. Decreasing the injection or increasing duration concerningthe injection 60 du◦CAration has concerning not much e60ffect °CA on has the not HC much reduction effect [51 on]. Forthe HC all SOIs, reduction the injection [51]. For duration all SOIs, of the 60 injection◦CA showed duration lower of HC. 60 °CA Further, showed at 60 lower◦CA HC. injection Further, duration, at 60 the°CA hydrogen injection getsduration, sufficient the time hydrogen to mix withgets airsuffic leadingient time to a moreto mix homogeneous with air leading mixture. to Thisa more can leadhomogeneous to better combustion mixture. This of thecan fuellead combinations to better combus usedtion [26 ,of32 ,the45]. fuel Therefore, combinations it is concluded used [26,32,45]. that for 10Therefore,◦ ATDC hydrogenit is concluded injection that and for 60 10°◦CA ATDC duration hydrogen with CMFIS injection was and found 60 °CA to be duration optimum. with Advancing CMFIS orwas retarding found to the be hydrogen optimum. injection Advancing regarding or retarding 10◦ ATDC the caused hydrogen a higher injection HC level, regarding and this 10° might ATDC be attributedcaused a higher to non-uniform HC level, air-hydrogenand this might mixtures be attributed with reduced to non-uniform chemical kineticsair-hydrogen observed mixtures during with the ignitionreduced delaychemical period. kinetics observed during the ignition delay period.

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0.12 CMFIS: Speed: 1500 rpm, pilot fuel IT: 27obTDC, IOP:205(D), 240 bar (METP), Diesel - Hydrogen CR:17.5, TRCC, Hydrogen flow rate: 0.1 kg/h, EGR: 20% METP-Hydrogen

0.10 0.092 0.09 0.088 0.088 0.086 0.084 0.084 0.084 0.084 0.082 0.082

0.08 0.08 0.078 0.078 0.078 0.076 0.076 0.074 0.074 0.07 0.07 0.07 0.064 0.062 0.06

0.04

HC emission (g/kWh) 0.02

0.00 30˚ CA (6.6 mS) (6.6 CA 30˚ mS) (6.6 CA 30˚ mS) (6.6 CA 30˚ mS) (6.6 CA 30˚ 60˚ CA (13.2 mS) CA (13.2 60˚ mS) CA (19.8 90˚ mS) CA (13.2 60˚ mS) CA (19.8 90˚ mS) CA (13.2 60˚ mS) CA (19.8 90˚ mS) CA (13.2 60˚ mS) CA (19.8 90˚

TDC 5˚ aTDC (1.1 mS) 10˚ aTDC (2.2 mS) 15˚ aTDC (3.3 mS) Start of injection and injection duration of Hydrogen (Manifold injection)

Figure 12. Hydrocarbon (HC) for manifold injection of hydrogen in CMFIS based dual-fuel engine. Figure 12. Hydrocarbon (HC) for manifold injection of hydrogen in CMFIS based dual-fuel engine. Figure 13 indicates the emissions of CO of a dual-fuel engine fueled with diesel/METP- hydrogen Figure 13 indicates the emissions of CO of a dual-fuel engine fueled with diesel/METP- hydrogen operation in which diesel and METP were injected using both CMFIS. Further, hydrogen was injected operation in which diesel and METP were injected using both CMFIS. Further, hydrogen was injected (manifold) at varied injection timings and injection duration for 80% load. Biodiesel operation (manifold) at varied injection timings and injection duration for 80% load. Biodiesel operation with with hydrogen injection has higher CO emission levels over a given range of operating conditions hydrogen injection has higher CO emission levels over a given range of operating conditions contrasted to petroleum oil-hydrogen operation. It might be ascribed to their higher viscosity and contrasted to petroleum oil-hydrogen operation. It might be ascribed to their higher viscosity and lower volatility [51]. This is primarily attributed to the decrease burning rates associated with biodiesel lower volatility [51]. This is primarily attributed to the decrease burning rates associated with triggered by heightened area of quenching interior combustion chamber with Hydrogen injection. biodiesel triggered by heightened area of quenching interior combustion chamber with Hydrogen The lower BTE obtained with HB-hydrogen might be accountable for the risen CO level contrasted to injection. The lower BTE obtained with HB-hydrogen might be accountable for the risen CO level petroleum oil-hydrogen injection. It is observed that hydrogen manifold injection produces lesser CO contrasted to petroleum oil-hydrogen injection. It is observed that hydrogen manifold injection emission levels. As the SOI was varied from TDC to 10◦ ATDC, emissions of CO decreased. The higher produces lesser CO emission levels. As the SOI was varied from TDC to 10° ATDC, emissions of CO BTE at these SOIs might be accountable for the results obtained. Beyond 15◦ ATDC CO increased decreased. The higher BTE at these SOIs might be accountable for the results obtained. Beyond 15° probably due to incomplete combustion arising from improper air-hydrogen mixing. For all SOIs, ATDC CO increased probably due to incomplete combustion arising from improper air-hydrogen the injection duration of 60 ◦CA showed lower CO. Decreasing or increasing the injection duration mixing. For all SOIs, the injection duration of 60 °CA showed lower CO. Decreasing or increasing the with respect to 60 ◦CA has not much eﬀect on the smoke opacity reduction. Further, at 60 ◦CA injection injection duration with respect to 60 °CA has not much effect on the smoke opacity reduction. Further, duration, the hydrogen gets suﬃcient time to mix with air leading to a more homogeneous mixture. at 60 °CA injection duration, the hydrogen gets sufficient time to mix with air leading to a more This further assists in the augmented burning of the fuel combinations used caused by their better homogeneous mixture. This further assists in the augmented burning of the fuel combinations used oxidation [38]. Hence, CO levels were decreased for the combination of 10◦ ATDC injection timing caused by their better oxidation [38]. Hence, CO levels were decreased for the combination of 10° and 60 ◦CA injection duration. Dual fuel procedure with a manifold injection when the engine was ATDC injection timing and 60 °CA injection duration. Dual fuel procedure with a manifold injection conducted with hydrogen injection timing of 10◦ BTDC and injection interval of 60 ◦CA triggers into when the engine was conducted with hydrogen injection timing of 10° BTDC and injection interval lower CO quantities. Reduction in oxidation rate instigated by the substitute of air by hydrogen and of 60 °CA triggers into lower CO quantities. Reduction in oxidation rate instigated by the substitute dropped burning temperature may be accountable for the noticed tendencies. Further it is observed of air by hydrogen and dropped burning temperature may be accountable for the noticed tendencies. that at all SOI with port injection of hydrogen and injection durations lead to reduced air intake and Further it is observed that at all SOI with port injection of hydrogen and injection durations lead to air-hydrogen mixing. Pilot fuel injection of METP with CMFIS system in dual fuel engine may decrease reduced air intake and air-hydrogen mixing. Pilot fuel injection of METP with CMFIS system in dual the atomization leading to increased CO amounts. fuel engine may decrease the atomization leading to increased CO amounts.

Energies 2020, 13, 5663 18 of 27 Energies 2020, 13, x FOR PEER REVIEW 18 of 27

0.21 CMFIS: 0.20 Speed: 1500 rpm, pilot fuel IT: 27obTDC, IOP:205(D), 240 bar (METP), Diesel - Hydrogen CR:17.5, TRCC, Hydrogen flow rate: 0.1 kg/h, EGR: 20% 0.19 METP-Hydrogen 0.18 0.176

0.17 0.17 0.164 0.163 0.16 0.156 0.151 0.15

0.15 0.148

0.14 0.14 0.14

0.13 0.13

0.12 0.12 0.11 0.11 0.11 0.11 0.11 0.1 0.1 0.1 0.10 0.1 0.09 0.09 0.09 0.09 CO emissionCO (% vol.)

0.08 0.08

0.07

0.06 30˚ CA (6.6 mS) (6.6 CA 30˚ mS) (6.6 CA 30˚ mS) (6.6 CA 30˚ mS) (6.6 CA 30˚ 60˚ CA (13.2 mS) 90˚ CA (19.8 mS) 60˚ CA (13.2 mS) 90˚ CA (19.8 mS) 60˚ CA (13.2 mS) 90˚ CA (19.8 mS) 60˚ CA (13.2 mS) 90˚ CA (19.8 mS)

TDC 5˚ aTDC (1.1 mS) 10˚ aTDC (2.2 mS) 15˚ aTDC (3.3 mS) Start of injection and injection duration of Hydrogen (Manifold injection)

FigureFigure 13. CarbonCarbon Monoxide Monoxide (CO) (CO) for manifold for manifold injectio injectionn of Hydrogen of Hydrogen in CMFIS in based CMFIS a dual-fuel based a dual-fuelengine. engine.

FigureFigure 1414 illustratesillustrates thethe emissionsemissions ofof NOxNOx emissionsemissions ofof aa dual-fueldual-fuel engineengine fuelledfuelled withwith dieseldiesel/METP-hydrogen/METP-hydrogen operationoperation in which diesel and METP were injected using both CMFIS. Further,Further, hydrogen was was injected injected (manifold) (manifold) at at varied varied injection injection timings timings and and injection injection duration duration for 80% for 80% load. NO concentrations grow when the burning occurs in the presence of oxygen and at load. NOx concentrationsX grow when the burning occurs in the presence of oxygen and at higher peak highercombustion peak combustiontemperatures temperatures and boosted andresidence boosted time residence. For all time.the operating For all the parameters operating used, parameters higher used, higher NO concentrations were detected for diesel–hydrogen dual fuel operation compared to NOX concentrationsX were detected for diesel–hydrogen dual fuel operation compared to METP- METP-hydrogen,hydrogen, a dual-fuel a dual-fuel operation. operation. Higher Higher premix premixeded combustion combustion phase phase associated associated with with dieseldiesel comparedcompared toto METPMETP withwith hydrogenhydrogen injectioninjection (manifold)(manifold) beingbeing commoncommon isis mainlymainly responsibleresponsible forfor thesethese trendstrends ofof results.results. HigherHigher temperaturetemperature prevailingprevailing insideinside thethe combustioncombustion chamberchamber instigatedinstigated byby thethe utilization of hydrogen leads to higher NO for both liquid pilot fuels injected [32,38,45]. Investigations utilization of hydrogen leads to higherX NOX for both liquid pilot fuels injected [32,38,45]. onInvestigations dual fuel operation on dualwith fuel CMISoperation facilities with usingCMIS a facilities manifold using injection a manifold of hydrogen injection at injection of hydrogen timing at ofinjection 10◦ ATDC timing and ofinjection 10° ATDC duration and injection of 60 ◦durationCA causes of 60 into °CA higher causes NOx into concentrations.higher NOx concentrations. As the SOI hasAs the diff eredSOI has from differed TDC to from 10◦ ATDC,TDC to NOx 10° ATDC, enlarged. NO Improvedx enlarged. engine Improved performance engine performance with higher with BTE athigher these BTE SOIs at could these be SOIs accountable could be for accountabl the findingse achieved.for the findings Beyond achieved. 15◦ ATDC, Beyond emissions 15° ofATDC, NOx reduced,emissions possibly of NOx attributed reduced, topossibly incomplete attributed burning to arisingincomplete from improperburning arising air-hydrogen from improper mixing with air- decreasedhydrogen mixing in-cylinder with temperatures. decreased in-cylinder For all SOIs,temperat theures. injection For all duration SOIs, the of 60injection◦CA showed duration higher of 60 NOx,°CA showed and this higher could NOx, be due and to this a higher could premixed be due to combustiona higher premixed phase ascombustion more fuel phase burns as during more thisfuel phase.burns during Decreasing this phase. or increasing Decreasi theng or injection increasing duration the injection concerning duration 60 ◦CA concerning has not much60 °CA eff hasect not on themuch NOx effect increase. on the Hence NOx increase. higher NOx Hence levels higher were NO exhaustedx levels were when exhausted the combustion when the is taking combustion place atis increasedtaking place combustion at increased temperatures combustion in temperatures the flame zone. in Injectionthe flame of zone. hydrogen Injection increases of hydrogen the combustion increases temperaturethe combustion attributed temperature to its higher attributed burning to its speed higher facilitating burning enhanced speed facilitating flame propagation enhanced during flame thepropagation burning processduring the [47 ].burning Further, process at 60 [47].◦CA Further, injection at duration,60 °CA injection the hydrogen duration, gets the su hydrogenfficient time gets tosufficient mix with time air, to leading mix with to air, a more leading homogeneous to a more homogeneous mixture. This mixture. can cause This better can cause burning better of theburning fuel combinationsof the fuel combinations utilized by enhanced utilized oxidationby enhanced of the oxidation fuel combinations. of the fuel Hence, combinations. it is concluded Hence, that it the is NOxconcluded concentrations that the NOx were enhancedconcentrations at 10 ◦wereATDC enha injectionnced at timing 10° ATDC and 60 injection◦CA injection timing duration. and 60 °CA injection duration.

Energies 2020, 13, 5663 19 of 27 Energies 2020, 13, x FOR PEER REVIEW 19 of 27

CMFIS: 16 Speed: 1500 rpm, pilot fuel IT: 27obTDC, IOP:205(D), 240 bar (METP), Diesel - Hydrogen CR:17.5, TRCC, Hydrogen flow rate: 0.1 kg/h, EGR: 20% METP-Hydrogen 14 12.9 12.59 12.409 12.4 12.26 12.21 12.14 12.01 11.87

12 11.81 11.75 11.74 11.74 11.73 11.47 11.47 11.41 11.25 11.12 11.12 11.06 10.59 10.27 10

8 7.67

4 NOx emissionsNOx (g/kWh) 2

0 30˚ CA (6.6 mS) (6.6 CA 30˚ mS) (6.6 CA 30˚ mS) (6.6 CA 30˚ mS) (6.6 CA 30˚ 60˚ CA (13.2 mS) (13.2 CA 60˚ mS) (19.8 CA 90˚ mS) (13.2 CA 60˚ mS) (19.8 CA 90˚ mS) (13.2 CA 60˚ mS) (19.8 CA 90˚ mS) (13.2 CA 60˚ mS) (19.8 CA 90˚

TDC 5˚ aTDC (1.1 mS) 10˚ aTDC (2.2 mS) 15˚ aTDC (3.3 mS) Start of injection and injection duration of Hydrogen (Manifold injection)

Figure 14. NOxNOx for for manifold manifold injection injection of hydrogen in CMFIS based a dual-fuel engine.

This sectionsection highlights highlights the the various various burning burning factors factors such assuch ID, CD,as ID, peak CD, pressure, peak HRRpressure, associated HRR associatedwith METP-hydrogen with METP-hydrogen operated dual-fuel operated engine dual-fue withl ECUengine controlled with ECU hydrogen controlled using hydrogen both manifold using bothand portmanifold injection and methods. port injection Injection methods. of hydrogen Inject playsion of a significanthydrogen roleplays in a the significant combustion role behavior in the combustionas compared behavior to when as the compared same was to inducted when the [ 47same]. Figure was inducted 15 shows [47]. the Figure ignition 15 delay shows of the a modified ignition delaydual-fuel of a engine modified fueled dual-fuel with diesel engine/METP-hydrogen fueled with diesel/METP-hydrogen operation in which diesel operation and METP in werewhich injected diesel andusing METP both CMFIS.were injected Further, using hydrogen both wasCMFIS. injected Furthe (manifold)r, hydrogen at varied was injectioninjected (manifold) timings and at injection varied injectionduration timings for 80 and and 100% injection load. duration Hydrogen for injection 80 and 100% is common, load. Hydrogen and for the injection same SOI is common, and injection and forduration the same for theSOI dual-fuel and injection engine duration operation for durations,the dual-fuel higher engine viscosity operation and lowerdurations, cetane higher number viscosity of the andMETP lower resulted cetane in number increased of ignitionthe METP delay resulted compared in increased to diesel. ignition At an optimizeddelay compared SOI of to 10 diesel.◦ ATDC At and an optimized60 ◦CA, the SOI injection of 10° ATDC duration and was 60 °CA, found the for injection all the duration cases considered. was found Results for all the showed cases thatconsidered. beyond 10Results◦ ATDC showed injection that timing beyond and 10° for ATDC varied injection injection timing duration, and lowered for varied peak injection pressures duration, with heightened lowered peakignition pressures delay has with been heightened observed. Further,ignition atdelay other has operating been observed. conditions, Further, the mixing at other of air-hydrogen operating conditions,becomes challenging the mixing and of air-hydrogen requires higher becomes chemical challenging delay. and requires higher chemical delay. Figure 16 demonstrates the combustion duration of a modified dual-fuel engine fueled with diesel/METP-hydrogen operation in which diesel and METP were injected using both CMFIS facilities. Further, Hydrogen was injected (manifold) at varied injection timings and injection duration for 80% and 100% load. For all the operating conditions tested, higher combustion durations were obtained for METP-hydrogen engine operation when in comparison to diesel–hydrogen operation. It might be anticipated to the lower peak pressures observed during the premixed combustion phase associated with reduced HRR [20,31]. Higher viscosity and lower calorific value of the METP, along with incomplete mixing of fuel combination is also responsible for increased combustion duration [32]. At optimized SOI of 10◦ ATDC and 60 ◦CA injection duration with CMFIS facility, combustion duration decreased compared to other tested parameters used. This is due to improved air-hydrogen mixing caused by the enhanced chemical kinetics leading to an increase in the combustion temperature. However, for manifold controlled injection of Hydrogen with CMFIS operation, lowered combustion durations occurred, and this could be due to improved air-fuel mixing obtained in the former method. However, beyond 10◦ ATDC injection timing and for varied injection duration, lowered peak pressures with increasing combustion duration has been observed. Reduced premixed combustion lead to higher combustion duration [32]. Further, at other operating conditions, the mixing of air-hydrogen becomes difficult and requires higher chemical delay. It is concluded that SOI of 10◦ ATDC and duration of

Figure 15. Ignition delay for manifold injection of hydrogen in CMFIS based dual-fuel engine.

Energies 2020, 13, x FOR PEER REVIEW 19 of 27

12 11.81 11.75 11.74 11.74 11.73 11.47 11.47 11.41 11.25 11.12 11.12 11.06 10.59 10.27 10

8 7.67

4 NOx emissionsNOx (g/kWh) 2

TDC 5˚ aTDC (1.1 mS) 10˚ aTDC (2.2 mS) 15˚ aTDC (3.3 mS) Start of injection and injection duration of Hydrogen (Manifold injection)

Figure 14. NOx for manifold injection of hydrogen in CMFIS based a dual-fuel engine.

This section highlights the various burning factors such as ID, CD, peak pressure, HRR associated with METP-hydrogen operated dual-fuel engine with ECU controlled hydrogen using both manifold and port injection methods. Injection of hydrogen plays a significant role in the combustion behavior as compared to when the same was inducted [47]. Figure 15 shows the ignition delay of a modified dual-fuel engine fueled with diesel/METP-hydrogen operation in which diesel and METP were injected using both CMFIS. Further, hydrogen was injected (manifold) at varied injection timings and injection duration for 80 and 100% load. Hydrogen injection is common, and for the same SOI and injection duration for the dual-fuel engine operation durations, higher viscosity andEnergies lower2020 ,cetane13, 5663 number of the METP resulted in increased ignition delay compared to diesel.20 At of an 27 optimized SOI of 10° ATDC and 60 °CA, the injection duration was found for all the cases considered. Results showed that beyond 10° ATDC injection timing and for varied injection duration, lowered Energiespeak60 ◦CA pressures 2020 and, 13 with, x FOR with CMFIS PEER heightened REVIEW and manifold ignition gas injectiondelay has facility been resulted observed. in aFurther, reduction at in other the combustion operating20 of 27 conditions,durations compared the mixing to of other air-hydrogen SOI and injection becomes durations challenging tested. and requires higher chemical delay. Figure 16 demonstrates the combustion duration of a modified dual-fuel engine fueled with diesel/METP-hydrogen operation in which diesel and METP were injected using both CMFIS facilities. Further, Hydrogen was injected (manifold) at varied injection timings and injection duration for 80% and 100% load. For all the operating conditions tested, higher combustion durations were obtained for METP-hydrogen engine operation when in comparison to diesel–hydrogen operation. It might be anticipated to the lower peak pressures observed during the premixed combustion phase associated with reduced HRR [20,31]. Higher viscosity and lower calorific value of the METP, along with incomplete mixing of fuel combination is also responsible for increased combustion duration [32]. At optimized SOI of 10° ATDC and 60 °CA injection duration with CMFIS facility, combustion duration decreased compared to other tested parameters used. This is due to improved air-hydrogen mixing caused by the enhanced chemical kinetics leading to an increase in the combustion temperature. However, for manifold controlled injection of Hydrogen with CMFIS operation, lowered combustion durations occurred, and this could be due to improved air-fuel mixing obtained in the former method. However, beyond 10° ATDC injection timing and for varied injection duration, lowered peak pressures with increasing combustion duration has been observed. Reduced premixed combustion lead to higher combustion duration [32]. Further, at other operating conditions, the mixing of air-hydrogen becomes difficult and requires higher chemical delay. It is concluded that SOI of 10° ATDC and duration of 60 °CA and with CMFIS and manifold gas injection facility resultedFigure 15. in IgnitionIgnition a reduction delay delay for for in manifold manifold the combusti injection injectionon of ofdurations hydrogen incompared CMFIS based to other dual-fuel SOI engine. and injection durations tested.

Figure 16. CombustionCombustion duration duration for for manifold manifold injection injection of of hydrogen hydrogen in CMFIS CMFIS based based dual-fuel dual-fuel engine.

Figure 17 indicates the peak pressure variation for modified modiﬁed dual-fuel engine fuelled with diesel/METP-hydrogendiesel/METP-hydrogen operationoperation in in which which diesel diesel and and METP METP were injectedwere injected using bothusing CMFIS both facilities.CMFIS facilities.Additionally, Additionally, hydrogen hydrogen was injected was (manifold) injected (manifold) at varied injection at varied timings injection and timings injection and duration injection for duration80% load. for METP 80% showed load. METP lower showed peak pressures lower peak due to pressures lowered BTEdue associatedto lowered with BTE lowered associated premixed with loweredHRR with premixed both gas HRR andliquid with both injection gas and facilities. liquid Peak injection pressures facilities. were Peak higher pressures for pilot were fuel injectionhigher for of pilotMETP fuel with injection CRDI systemof METP as with higher CRDI fuel system injection as higher pressure fuel may injection enhance pressure the fuel may mixing enhance rates the due fuel to mixingoptimized rates fuel due droplet to optimized sizes. At fuel injection droplet timing sizes. of At 10 ◦injectionATDC and timing injection of 10° duration ATDC ofand 60 injection◦CA for duration of 60 °CA for hydrogen in both versions of the manifold and port injection, higher peak pressures were found for both diesel–hydrogen and METP-hydrogen dual-fuel operation compared to other test conditions. At these conditions, the flame speed of hydrogen burning in the air being higher, the energy required to initiate the combustion with hydrogen is less. A combination of

Energies 2020, 13, 5663 21 of 27 hydrogen in both versions of the manifold and port injection, higher peak pressures were found for both diesel–hydrogen and METP-hydrogen dual-fuel operation compared to other test conditions. At these conditions, the ﬂame speed of hydrogen burning in the air being higher, the energy required Energies 2020, 13, x FOR PEER REVIEW 21 of 27 to initiate the combustion with hydrogen is less. A combination of hydrogen and air are combustible hydrogenover an exceptionally and air are varied combustible assortment over of ﬂammability an exceptionally restrictions varied at ordinaryassortment temperatures of flammability and can restrictionscontinue from at ordinary 4% to 74% temperatures by volume ofand hydrogen can continue in air. from 4% to 74% by volume of hydrogen in air.

Figure 17. PeakPeak pressure pressure for manifold injection of hydrogen in CMFIS based dual-fuel engine.

The ignition delay is the time lag between the start of injection and the start of ignition. The start of injection was obtained based on the static injection timing. ID ID is is measured measured from cylinder pressure versus crank angle diagrams. It It is is measured measured from from the the start start of of injection to the start of combustion (where thethe pressure pressure curve curve deviates). deviates). Combustion Combusti durationon duration was measured was measured from the startfrom ofthe combustion start of combustionto 90% of the to cumulative 90% of the heatcumulati releaseve rate.heat Inrelease cylinder-pressure rate. In cylinder-pressure was measured was with measured a piezoelectric with a piezoelectrictransducer. Peak transducer. pressure Peak refers pressure to the maximum refers to cylinderthe maximum pressure cylinder observed pressure in the cycle.observed in the cycle.Figure 18 present the variation of injection timing and injection duration on the HRR of the modifiedFigure dual-fuel 18 present engine the fueled variation with of diesel injection/METP-hydrogen timing and combinationinjection duration in which on dieselthe HRR and METPof the modifiedwere injected dual-fuel using bothengine CMFIS fueled facilities with atdiesel/M 80% load.ETP-hydrogen Moreover, hydrogencombination was injectedin which (manifold) diesel and at METPvaried injectionwere injected timings using and injectionboth CMFIS duration facilities for 80 at and 80% 100% load. load. Moreover, METP showedhydrogen lower was HRRs injected due (manifold)to lowered BTEat varied associated injection with timings reduced and premixed injection combustion duration phasefor 80 with and both100% gas load. and METP liquid injectionshowed lowerfacilities. HRRs HRRs due were to lowered higher forBTE pilot associated fuel injection with re ofduced METP premixed with CDRI combustion system as phase higher with fuel both injection gas andpressure liquid may injection enhance facilities. the fuel HRRs mixing were rates higher due for to pilot optimized fuel injection fuel droplet of METP sizes with [56]. CDRI Lower system HRR asfor higher METP-hydrogen fuel injection obtained pressure could may be enhance due to the the fact fuel that mixing the hydrogen rates due injectionto optimized during fuel the droplet intake sizesprocess [56]. lowers Lower the HRR in-cylinder for METP-hydrogen temperatures. Thisobtained could could result be in due retarded to the primary fact that fuel the combustion. hydrogen injectionIn addition, during the lowerthe intake calorific process value lowers of METP the in-cylinder in both versions temperatures. of CMFIS This injection could result facilities in retarded relative primaryto diesel fuel fuel combustion. is associated In with addition, reduced the premixed lower calorific combustion value withof METP hydrogen in both fuel versions injection of mayCMFIS be injectionaccountable facilities for the relative diminished to diesel HRR whenfuel is contrasted associated to dieselwith reduced function. premixed At an injection combustion timing ofwith 10◦ hydrogenATDC and fuel injection injection duration may of be 60 ◦accountableCA for hydrogen for the in bothdiminished CMFIS ofHRR manifold when injection, contrasted higher to diesel HRRs function.were found At foran injection both diesel–hydrogen timing of 10° ATDC and METP-hydrogen and injection duration dual-fuel of operation60 °CA for compared hydrogen toin otherboth CMFIStested conditions.of manifold At injection, these conditions, higher theHRRs flame we speedre found of Hydrogen for both burningdiesel–hydrogen in the air and is increased, METP- hydrogenwhile the energy dual-fuel required operation to initiate compared the burning to other with tested hydrogen conditions. is reduced. At these However, conditions, at other the SOIs flame and speedinjection of Hydrogen durations, theburning combustion in the air of is hydrogen increased, led while to reduced the energy pressure required and temperatureto initiate the instigated burning with hydrogen is reduced. However, at other SOIs and injection durations, the combustion of hydrogen led to reduced pressure and temperature instigated by the diminished blending rates of air-hydrogen mixtures. Hence with CMFIS facility, at SOI of 10° ATDC and injection duration of 60 °CA, higher HRR has been noticed.

Energies 2020, 13, 5663 22 of 27

by the diminished blending rates of air-hydrogen mixtures. Hence with CMFIS facility, at SOI of 10◦ ATDCEnergies and2020, injection13, x FOR PEER duration REVIEW of 60 ◦CA, higher HRR has been noticed. 22 of 27

Figure 18.18. HeatHeat Release Release Rate Rate (HRR) (HRR) for for manifold manifold injection injection of hydrogen of hydrogen in CMFIS in CMFIS based dual-fuelbased dual-fuel engine. engine. 4. Conclusions 4. ConclusionsIn the current study, the engine operated smoothly at a fixed speed of 1500 rpm with very minimal vibrationIn the and current noise level.study, Subsequent the engine conclusionsoperated sm wereoothly derived at a fixed from investigationsspeed of 1500 undertaken:rpm with very minimal vibration and noise level. Subsequent conclusions were derived from investigations 1. Optimized SOI of 10◦ ATDC and 60 ◦CA duration provides an enhancement in dual-fuel undertaken: engine performance with METP and hydrogen fuel mixtures in manifold injection method with 1. OptimizedCMFIS system. SOI of 10° ATDC and 60 °CA duration provides an enhancement in dual-fuel engine 2. performancePrecise injection with ofMETP gaseous and fuelshydrogen in the fuel manifold mixtures injection in manifold along injection with CMFIS method amenities with CMFIS can system.additionally provide further improvement in power characteristics and emission stability. 3.2. PreciseManifold injection injection of provides gaseous uniformfuels in mixingthe manifold of air-hydrogen injection and along thereby with augmentsCMFIS amenities the dual-fuel can additionallyengine performance provide infurther conditions improvement of augmented in power BTE, characteristics diminished smoke, and emission HC and stability. CO emissions. 3. ManifoldHowever injection the study provides noticed boostuniform in the mixing magnitude of air-hydrogen of NOx emissions. and thereby augments the dual- 4. fuelThe CMFISengine methodperformance integrated in conditions with manifold of augmented injection ofBTE, gaseous diminish fueled can smoke, lead to considerableHC and CO emissions.improvement However in engine the performance.study noticed boost in the magnitude of NOx emissions. 4. The CMFIS method integrated with manifold injection of gaseous fuel can lead to considerable Theimprovement reported study in engine can be performance. further extended to incorporate investigations on regulation of hydrogen flowrate, alternate fuel blends and varying load conditions. Also, there is further scope on the study of effectThe of nanoparticle reported study fuel additivescan be further ternary extended fuel blends to [incorporate57–62]. investigations on regulation of hydrogen flowrate, alternate fuel blends and varying load conditions. Also, there is further scope on Authorthe study Contributions: of effect of nanoparticleM.M. (Mahantesh fuel additives Marikatti), ternary conceptualization, fuel blends methodology,[57–62]. investigation; N.R.B., V.S.Y. and Y.B., supervision, project administration, draft and resources; M.E.M.S., interpretation of results, conceptualizationAuthor Contributions: and reviewing; M.M. (Mahantesh F.P.G.M., Marikatti), formal analyses, conceptualizat reviewing;ion, M.M. methodology, (MA Mujtaba), investigation; formal analyses, N.R.B., review and editing; H.F. and B.N., review and editing, validation; T.Y.K., writing methodology; A.A. and A.I.E.-S., reviewV.S.Y. and and Y.H.B., editing. supervision, All authors haveproject read administration, and agreed to dr theaft published and resources; version M.E.M.S., of the manuscript. interpretation of results, conceptualization and reviewing; F.P.G.M., formal analyses, reviewing; M.M. (MA Mujtaba), formal analyses, Funding: review andThis editing; research H.F. received and B.N., no review external and funding. editing, validation; T.Y.K., writing methodology; A.A. and A.I.E.- ConflictsS., review ofand Interest: editing.The All authorsauthors declarehave read no conflictand agreed of interest. to the published version of the manuscript.

Funding: This research received no external funding.

Conflicts of Interest: The authors declare no conflict of interest.

Energies 2020, 13, 5663 23 of 27

Nomenclature

ASTM American Society of Testing and Materials ATDC After top dead center SFC Specific Fuel Consumption BSFC Brake Specific Fuel Consumption BSEC Brake Specific Energy Consumption CC Combustion chamber ◦CA Crank angle (degrees) CO Carbon monoxide UHC Unburned Hydrocarbons CP Cylinder pressure CNG Compressed Natural Gas LPG Liquefied Petroleum Gas CRDI Common Rail Direct Injection CFD Computational Fluid Dynamics ECU Electronic control unit H2 Hydrogen HRR Heat release rate IP Injection pressure METP Methyl Ester Thevetia peruviana PP Peak Pressure TCC Toroidal CC BTE Brake Thermal Efficiency BP Brake Power TDC Top dead center BTDC Before top dead center CD Combustion duration CI Compression ignition CO2 Carbon dioxide CR Compression ratio CMFIS Conventional Mechanical Fuel Injection System BMEP Brake Mean Effective Pressure IMEP Indicated Mean Effective Pressure EGR Exhaust gas recirculation HCC Hemispherical CC HCNG hydrogenated compressed natural gas ID Ignition delay IT Injection timing NOX Oxides of nitrogen TRCC Toroidal re-entrant CC UBHC Unburnt hydrocarbon

References

1. Soudagar, M.E.M.; Nik-Ghazali, N.-N.; Kalam, M.; Badruddin, I.A.; Banapurmath, N.; Ali, M.A.B.; Kamangar, S.; Cho, H.M.; Akram, N. An investigation on the influence of aluminium oxide nano-additive and honge oil methyl ester on engine performance, combustion and emission characteristics. Renew. Energy 2020, 146, 2291–2307. [CrossRef] 2. Delvi, M.K.; Soudagar, M.E.M.; Khan, H.; Ahmed, Z.; Shariff, I.M. Biodiesel production utilizing diverse sources, classification of oils and their esters, performance and emission characteristics: A research. Int. J. Recent Technol. Eng. 2019, 8, 1–8. 3. Mujtaba, M.; Masjuki, H.; Kalam, M.; Noor, F.; Farooq, M.; Ong, H.C.; Gul, M.; Soudagar, M.E.M.; Bashir, S.; Rizwanul Fattah, I. Effect of additivized biodiesel blends on diesel engine performance, emission, tribological characteristics, and lubricant tribology. Energies 2020, 13, 3375. [CrossRef] Energies 2020, 13, 5663 24 of 27

4. El-Seesy, A.I.; Hassan, H.; Ibraheem, L.; He, Z.; Soudagar, M.E.M. Combustion, emission, and phase stability features of a diesel engine fueled by jatropha/ethanol blends and n-butanol as co-solvent. Int. J. Green Energy 2020, 17, 1–12. [CrossRef] 5. Soudagar, M.E.M.; Nik-Ghazali, N.-N.; Badruddin, I.A.; Kalam, M.; Kittur, M.I.; Akram, N.; Ullah, M.A.; Khan, T.Y.; Mokashi, I. Production of Honge Oil Methyl Ester (Home) and Its Performance Test on Four Stroke Single Cylinder vcr Engine. In AIP Conference Proceedings; AIP Publishing LLC: Melville, NY, USA, 2019; p. 200006. 6. Gavhane, S.R.; Kate, M.A.; Pawar, A.; Safaei, M.R.; M Soudagar, M.E.; Mujtaba Abbas, M.; Muhammad Ali, H.; Banapurmath, R.N.; Goodarzi, M.; Badruddin, I.A. Effect of zinc oxide nano-additives and soybean biodiesel at varying loads and compression ratios on vcr diesel engine characteristics. Symmetry 2020, 12, 1042. [CrossRef] 7. Márquez, F.P.G.; Karyotakis, A.; Papaelias, M. Renewable Energies: Business Outlook 2050; Springer: Berlin/Heidelberg, Germany, 2018. 8. Soudagar, M.E.M.; Nik-Ghazali, N.-N.; Kalam, M.A.; Badruddin, I.; Banapurmath, N.; Akram, N. The effect of nano-additives in diesel-biodiesel fuel blends: A comprehensive review on stability, engine performance and emission characteristics. Energy Convers. Manag. 2018, 178, 146–177. [CrossRef] 9. Pliego Marugán, A.; Garcia Marquez, F.P.; Lev, B. Optimal decision-making via binary decision diagrams for investments under a risky environment. Int. J. Prod. Res. 2017, 55, 5271–5286. [CrossRef] 10. Marugan, A.P.; Márquez, F.P.G. Decision-Making Management: A Tutorial and Applications; Academic Press: Cambridge, MA, USA, 2017. 11. Khan, H.; Soudagar, M.E.M.; Kumar, R.H.; Safaei, M.R.; Farooq, M.; Khidmatgar, A.; Banapurmath, N.R.; Farade, R.A.; Abbas, M.M.; Afzal, A. Effect of nano-graphene oxide and n-butanol fuel additives blended with diesel—Nigella sativa biodiesel fuel emulsion on diesel engine characteristics. Symmetry 2020, 12, 961. [CrossRef] 12. Soudagar, M.E.M.; Nik-Ghazali, N.-N.; Akram, N.; Al-Rashid, M.A.; Badruddin, I.A.; Khan, H.; Kallannavar, V.; Shahpurkar, K.; Afzal, A.; Farade, R. The Potential of Nanoparticle Additives in Biodiesel: A Fundamental Outset. In AIP Conference Proceedings, 2020; AIP Publishing LLC: Melville, NY, USA, 2020; p. 030003. 13. Soudagar, M.E.M.; Kittur, P.; Parmar, F.; Batakatti, S.; Kulkarni, P.; Kallannavar, V. Production of Mahua Oil Ethyl Ester (Moee) and Its Performance Test on Four Stroke Single Cylinder vcr Engine. In IOP Conference Series: Materials Science and Engineering, 2017; IOP Publishing: Bristol, UK, 2017. 14. Muñoz, C.Q.G.; Márquez, F.P.G. Future maintenance management in renewable energies. In Renewable Energies; Springer: Berlin/Heidelberg, Germany, 2018; pp. 149–159. 15. Sadeghian, O.; Moradzadeh, A.; Mohammadi-Ivatloo, B.; Abapour, M.; Garcia Marquez, F.P. Generation units maintenance in combined heat and power integrated systems using the mixed integer quadratic programming approach. Energies 2020, 13, 2840. [CrossRef] 16. Dey, B.; García Márquez, F.P.; Basak, S.K. Smart energy management of residential microgrid system by a novel hybrid mgwoscacsa algorithm. Energies 2020, 13, 3500. [CrossRef] 17. ETEnergyWorld. India can generate 18,000 megawatt renewable energy using biomass. The Economic Times, 9 December 2019. 18. Yaliwal, V.; Banapurmath, N.; Gireesh, N.; Tewari, P. Production and utilization of renewable and sustainable gaseous fuel for power generation applications: A review of literature. Renew. Sustain. Energy Rev. 2014, 34, 608–627. [CrossRef] 19. Yaliwal, V.; Banapurmath, N.; Tewari, P. Performance, combustion and emission characteristics of a single-cylinder, four-stroke, direct injection diesel engine operated on a dual-fuel mode using honge oil methyl ester and producer gas derived from biomass feedstock of different origin. Int. J. Sustain. Eng. 2014, 7, 253–268. [CrossRef] 20. Banapurmath, N.; Gireesh, N.; Basavarajappa, Y.; Hosmath, R.; Yaliwal, V.; Pai, A.; Gopal Navale, K.; Jog, P.; Tewari, P. Effect of hydrogen addition to cng in a biodiesel-operated dual-fuel engine. Int. J. Sustain. Eng. 2015, 8, 332–340. [CrossRef] Energies 2020, 13, 5663 25 of 27

21. Ministry of New and Renewable Energy. Bio Energy; Ministry of New and Renewable Energy: New Delhi, India, 2019. Available online: https://mnre.gov.in/ (accessed on 1 October 2020). 22. Das, L. Hydrogen engines: A view of the past and a look into the future. Int. J. Hydrogen Energy 1990, 15, 425–443. [CrossRef] 23. Das, L. Hydrogen engine: Research and development (r&d) programmes in indian institute of technology (iit), delhi. Int. J. Hydrogen Energy 2002, 27, 953–965. 24. Raman, V.; Hansel, J.; Fulton, J.; Lynch, F. Hythane-an ultraclean transportation fuel. Hydrog. Energy Prog. 1994, 3, 1797. 25. Akansu, S.O.; Bayrak, M. Experimental study on a spark ignition engine fueled by ch4/h2 (70/30) and lpg. Int. J. Hydrogrn Energy 2011, 36, 9260–9266. [CrossRef] 26. Pullagura, G.; BabjiAlapati, M.; Prakash, R. Effect of hydrogen enrichment on the combustion characteristics of a biofuel diesel engine. IosrjenIssn 2012, 2, 2250–3021. [CrossRef] 27. Gosal, M.; Das, L.; Babu, M.G. Improved efficiency of cng using hydrogen in spark ignition engine. J. Pet. Technol. Altern. Fuels 2013, 4, 99–112. 28. Liu, J.; Yang, F.; Wang, H.; Ouyang, M.; Hao, S. Effects of pilot fuel quantity on the emissions characteristics of a cng/diesel dual fuel engine with optimized pilot injection timing. Appl. Energy 2013, 110, 201–206. [CrossRef] 29. Mahla, S.; Das, L.; Babu, M. Effect of egr on performance and emission characteristics of natural gas fueled diesel engine. Jordan J. Mech. Ind. Eng. 2010, 4, 523–530. 30. Furuhama, S.; Yamane, K.; Yamaguchi, I. Combustion improvement in a hydrogen fueled engine. Int. J. Hydrogen Energy 1977, 2, 329–340. [CrossRef] 31. Naber, J.; Siebers, D. Hydrogen combustion under diesel engine conditions. Int. J. Hydrogen Energy 1998, 23, 363–371. [CrossRef] 32. Varde, K.; Frame, G. Hydrogen aspiration in a direct injection type diesel engine-its effects on smoke and other engine performance parameters. Int. J. Hydrogen Energy 1983, 8, 549–555. [CrossRef] 33. Kitagawa, T.; Kido, H.; Nakamura, N.; Aishima, M. Flame inertia into lean region in stratified hydrogen mixture. Int. J. Hydrogen Energy 2005, 30, 1457–1464. [CrossRef] 34. Soberanis, M.E.; Fernandez, A. A review on the technical adaptations for internal combustion engines to operate with gas/hydrogen mixtures. Int. J. Hydrogen Energy 2010, 35, 12134–12140. [CrossRef] 35. Kumar, M.S.; Ramesh, A.; Nagalingam, B. Use of hydrogen to enhance the performance of a vegetable oil fuelled compression ignition engine. Int. J. Hydrogen Energy 2003, 28, 1143–1154. 36. Geo, V.E.; Nagarajan, G.; Nagalingam, B. Studies on dual fuel operation of rubber seed oil and its bio-diesel with hydrogen as the inducted fuel. Int. J. Hydrogen Energy 2008, 33, 6357–6367. 37. Saravanan, N.; Nagarajan, G. An experimental investigation on hydrogen fuel injection in intake port and manifold with different egr rates. Int. J. Energy Environ. 2010, 1, 221–248. 38. Korakianitis, T.; Namasivayam, A.; Crookes, R. Hydrogen dual-fuelling of compression ignition engines with emulsified biodiesel as pilot fuel. Int. J. Hydrogen Energy 2010, 35, 13329–13344. [CrossRef] 39. Dimitriou, P.; Kumar, M.; Tsujimura, T.; Suzuki, Y. Combustion and emission characteristics of a hydrogen-diesel dual-fuel engine. Int. J. Hydrogen Energy 2018, 43, 13605–13617. [CrossRef] 40. Serrano, J.; Jiménez-Espadafor, F.; López, A. Analysis of the effect of different hydrogen/diesel ratios on the performance and emissions of a modified compression ignition engine under dual-fuel mode with water injection. Hydrogen-diesel dual-fuel mode. Energy 2019, 172, 702–711. [CrossRef] 41. Khan, N.; Balunaik, B.; Yousufuddin, S. Performance and emission characteristics of a diesel engine with varying injection pressure and fueled with hydrogen and cottonseed oil methyl ester blends. Mater. Today Proc. 2018, 5, 3369–3377. [CrossRef] 42. Koten, H. Hydrogen effects on the diesel engine performance and emissions. Int. J. Hydrogen Energy 2018, 43, 10511–10519. [CrossRef] 43. Liew, C.; Li, H.; Nuszkowski, J.; Liu, S.; Gatts, T.; Atkinson, R.; Clark, N. An experimental investigation of the combustion process of a heavy-duty diesel engine enriched with H2. Int. J. Hydrogen Energy 2010, 35, 11357–11365. [CrossRef] Energies 2020, 13, 5663 26 of 27

44. Chintala, V.; Subramanian, K.A. Assessment of maximum available work of a hydrogen fueled compression ignition engine using exergy analysis. Energy 2014, 67, 162–175. [CrossRef] 45. Rakopoulos, C.; Kyritsis, D. Hydrogen enrichment effects on the second law analysis of natural and landfill gas combustion in engine cylinders. Int. J. Hydrogen Energy 2006, 31, 1384–1393. [CrossRef] 46. Sandalcı, T.; Karagöz, Y. Experimental investigation of the combustion characteristics, emissions and performance of hydrogen port fuel injection in a diesel engine. Int. J. Hydrogen Energy 2014, 39, 18480–18489. [CrossRef] 47. Loganathan, M.; Velmurugan, A.; Page, T.; Gunasekaran, E.J.; Tamilarasan, P. Combustion analysis of a hydrogen-diesel fuel operated di diesel engine with exhaust gas recirculation. Front. Energy 2017, 11, 568–574. [CrossRef] 48. Santoso, W.; Bakar, R.; Nur, A. Combustion characteristics of diesel-hydrogen dual fuel engine at low load. Energy Procedia 2013, 32, 3–10. [CrossRef] 49. Masood, M.; Ishrat, M.; Reddy, A. Computational combustion and emission analysis of hydrogen–diesel blends with experimental verification. Int. J. Hydrogen Energy 2007, 32, 2539–2547. [CrossRef] 50. Banapurmath, N.; Tewari, P.; Hosmath, R. Experimental investigations of a four-stroke single cylinder direct injection diesel engine operated on dual fuel mode with producer gas as inducted fuel and honge oil and its methyl ester (home) as injected fuels. Renew. Energy 2008, 33, 2007–2018. [CrossRef] 51. Yaliwal, V.; Banapurmath, N.; Hosmath, R.; Khandal, S.; Budzianowski, W.M. Utilization of hydrogen in low calorific value producer gas derived from municipal solid waste and biodiesel for diesel engine power generation application. Renew. Energy 2016, 99, 1253–1261. [CrossRef] 52. Halewadimath, S.; Yaliwal, V.; Banapurmath, N.; Sajjan, A. Influence of hydrogen enriched producer gas (hpg) on the combustion characteristics of a crdi diesel engine operated on dual-fuel mode using renewable and sustainable fuels. Fuel 2020, 270, 117575. [CrossRef] 53. Karagöz, Y.; Sandalcı, T.; Yüksek, L.; Dalkılıç, A.S.; Wongwises, S. Effect of hydrogen–diesel dual-fuel usage on performance, emissions and diesel combustion in diesel engines. Adv. Mech. Eng. 2016, 8, 1687814016664458. [CrossRef] 54. Kostuchowski, J. Direct injection vs port injection remanufactured engines. Tristar: Engine and Transmission, 31 August 2018. 55. Deka, D.C.; Basumatary, S. High quality biodiesel from yellow oleander (thevetia peruviana) seed oil. Biomass Bioenergy 2011, 35, 1797–1803. [CrossRef] 56. Deb, M.; Sastry, G.; Panua, R.; Banerjee, R.; Bose, P. Effect of hydrogen-diesel dual fuel combustion on the performance and emission characteristics of a four stroke-single cylinder diesel engine. Int. J. Mech. Aerosp. Ind. Mechatron. Manuf. Eng. 2015, 9, 6–12. 57. Soudagar, M.E.M.; Mujtaba, M.A.; Safaei, M.R.; Afzal, A.; Raju, V.D.; Ahmed, W.; Banapurmath, N.R.; Hossain, N.; Bashir, S.; Badruddin, I.A.; et al. Effect of Sr@ ZnO nanoparticles and Ricinus communis biodiesel-diesel fuel blends on modified CRDI diesel engine characteristics. Energy 2020, 119094. [CrossRef] 58. Venu, H.; Raju, V.D.; Lingesan, S.; Soudagar, M.E.M. Influence of Al2O3nano additives in ternary fuel (diesel-biodiesel-ethanol) blends operated in a single cylinder diesel engine: Performance, Combustion and Emission Characteristics. Energy 2020, 119091. [CrossRef] 59. Soudagar, M.E.M.; Afzal, A.; Safaei, M.R.; Manokar, A.M.; L-Seesy, A.I.E.; Mujtaba, M.A.; Samuel, O.D.; Badruddin, I.A.; Ahmed, W.; Shahpurkar, K.; et al. Investigation on the effect of cottonseed oil blended with different percentages of octanol and suspended MWCNT nanoparticles on diesel engine characteristics. J. Therm. Anal. Calorim. 2020, 1–18. [CrossRef] 60. Soudagar, M.E.M.; Banapurmath, N.R.; Afzal, A.; Hossain, N.; Abbas, M.M.; Haniffa, M.A.C.M.; Naik, B.; Ahmed, W.; Nizamuddin, S.; Mubarak, N.M. Study of diesel engine characteristics by adding nanosized zinc oxide and diethyl ether additives in Mahua biodiesel–diesel fuel blend. Sci. Rep. 2020, 10, 1–17. [CrossRef] [PubMed] Energies 2020, 13, 5663 27 of 27

61. Mujtaba, M.A.; Kalam, M.A.; Masjuki, H.H.; Gul, M.; Soudagar, M.E.M.; Ong, H.C.; Ahmed, W.; Atabani, A.E.; Razzaq, L.; Yusoﬀ, M. Comparative study of nanoparticles and alcoholic fuel additives-biodiesel-diesel blend for performance and emission improvements. Fuel 2020, 279, 118434. [CrossRef] 62. Hussain, F.; Soudagar, M.E.M.; Afzal, A.; Mujtaba, M.; Fattah, I.R.; Naik, B.; Mulla, M.H.; Badruddin, I.A.; Khan, T.M.Y.; Raju, V.D.; et al. Enhancement in Combustion, Performance, and Emission Characteristics of a Diesel Engine Fueled with Ce-ZnO Nanoparticle Additive Added to Soybean Biodiesel Blends. Energies 2020, 13, 4578. [CrossRef]

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