The Effects of Port Water Injection on Spark Ignition Engine Performance and Emissions Fueled by Pure Gasoline, E5 And

processes

Article The Eﬀects of Port Water Injection on Spark Ignition Engine Performance and Emissions Fueled by Pure Gasoline, E5 and E10

Farhad Salek 1, Meisam Babaie 2,*, Maria Dolores Redel-Macias 3, Ali Ghodsi 1, Seyed Vahid Hosseini 1, Amir Nourian 2 , Martin L Burby 2 and Ali Zare 4

1 Faculty of Mechanical and Mechatronic Engineering, Shahrood University of Technology, Shahrood 3619995161, Iran; [email protected] (F.S.); [email protected] (A.G.); [email protected] (S.V.H.) 2 School of Science, Engineering and Environment, University of Salford, Manchester M5 4WT, UK; [email protected] (A.N.); [email protected] (M.L.B.) 3 Rural Engineering Department, Ed Leonardo da Vinci, Campus de Rabanales, Universidad de Córdoba, 14071 Córdoba, Spain; [email protected] 4 Flow, Aerosols & Thermal Energy (FATE) Group, School of Engineering, Deakin University, Geelong, VIC 3216, Australia; [email protected] * Correspondence: [email protected]; Tel.: +44-(0)161-295-5547

Received: 22 August 2020; Accepted: 22 September 2020; Published: 27 September 2020

Abstract: It has been proven that vehicle emissions such as oxides of nitrogen (NOx) are negatively affecting the health of human beings as well as the environment. In addition, it was recently highlighted that air pollution may result in people being more vulnerable to the deadly COVID-19 virus. The use of biofuels such as E5 and E10 as alternatives of gasoline fuel have been recommended by different researchers. In this paper, the impacts of port injection of water to a spark ignition engine fueled by gasoline, E5 and E10 on its performance and NOx production have been investigated. The experimental work was undertaken using a KIA Cerato engine and the results were used to validate an AVL BOOST model. To develop the numerical analysis, design of experiment (DOE) method was employed. The results showed that by increasing the ethanol fraction in gasoline/ethanol blend, the brake specific fuel consumption (BSFC) improved between 2.3% and 4.5%. However, the level of NOx increased between 22% to 48%. With port injection of water up to 8%, there was up to 1% increase in engine power whereas NOx and BSFC were reduced by 8% and 1%, respectively. The impacts of simultaneous changing of the start of combustion (SOC) and water injection rate on engine power and NOx production was also investigated. It was found that the NOx concentration is very sensitive to SOC variation.

Keywords: E10 biofuel; Ethanol; NOx; water port injection; start of combustion

1. Introduction Vehicle emissions are one of the main concerns around the world from both environmental and health perspectives. When the concentration of emissions, such as carbon monoxide (CO) and oxides of nitrogen (NOx) in the air exceeds a threshold limit, inhalation of these emissions by humans can result in deleterious health effects [1–3]. Recently, researchers have reported a link between air pollution and increased death rates from the Corona virus [4,5]. Due to such detrimental effects, authorities and researchers around the world are developing measures that can mitigate the adverse effects of using fossil fuels for internal combustion (IC) engines.

Processes 2020, 8, 1214; doi:10.3390/pr8101214 www.mdpi.com/journal/processes Processes 2020, 8, 1214 2 of 18

One of the solutions is to use alternative renewable fuels instead of fossil fuels. In IC engines, biofuels extracted from different renewable sources can be added into the fossil fuels at various percentages to provide a fuel mixture, the thermo-physical properties of which are better than pure gasoline. For example, ethanol has been used as an additive for gasoline in various countries for a number of years and is known as E5 [6,7]. One advantage of biofuels such as E5 is that they can be produced from renewable energy sources such as food waste through thermal processes [8–12]. The ethanol share in E5 fuel is about 5% which has increased to 10% in E10 and it has been recently employed in some countries based on their emission regulations (i.e., WLTP regulation) and fuel standards [6]. However, there are a few reservations that held out the increase in the ethanol level within the fuel blend (i.e., from E5 to E10) in some countries such as the UK despite the potential environmental benefits of biofuels, especially on CO2 reduction [13]. Changing the ethanol percentage in the fuel will affect the thermo-physical properties of the fuel blend with positive impacts on combustion and some emissions [14,15]. The effects of adding ethanol to gasoline fuel on engine performance and combustion characteristics have been investigated in the literature [2,16–19]. Adding ethanol to fuel can increase the mixed fuel octane number. Increasing the octane number of the fuel can reduce the engine knock intensity [20,21]. This means a better combustion efficiency, increasing the power and decreasing different exhaust emissions for the engine, except for NOx [22]. It has been reported that injection of biofuels into the engines leads to higher NOx emission production. This can be due to the addition of the fuel oxygen content which results in higher flame temperature during combustion [23,24]. The hydrous ethanol was also introduced as an alternative to ethanol for reducing engine NOx emissions [1,3,22]. The hydrous ethanol contains water, the injection of which into the combustion chamber results in a reduction in flame temperature, leading to lower NOx formation. However, as reported by Costa [22], this may bring some drawbacks at lower engine speeds such as a reduction in engine thermal efficiency. Apart from fuel solutions, other technical modifications are recommended in the literature to reduce the extra emissions produced by biofuel [25]. Zhuang et al. [16] studied the effects of ignition timing in a gasoline/ethanol dual-fuel engine using microscopic combustion in a numerical analysis. In this study, the start of combustion was changed in each configuration and its impacts on the combustion process that directly affect the emission characteristics were investigated. According to their result, retarding the start of combustion can improve the combustion efficiency. Huang et al. [17] conducted an experimental study in which the impacts of ethanol injection timing for an engine with an ethanol direct injection system was investigated. In this study, the ethanol was injected directly into the combustion chamber in a gasoline engine with a port fuel injection (PFI) system. Based on the results of their investigation, delaying the ethanol injection timing led to overcooling the combustion chamber which resulted in a reduction in NO emissions and an increase in CO and hydrocarbons (HC). In this paper, the effect of the port injection of water into a spark ignition gasoline engine equipped with multi-point fuel injection system and fueled by gasoline, E5 and E10 was investigated with respect to performance and emissions. The first part of the work involved the experimental analysis of a gasoline fueled engine to obtain its main functional outputs. After that, the engine was modeled in AVL BOOST software and the results of the model were validated against experimental data. The Latin Hypercube sampling method was employed to define the number of experiments and values of each design point in each experiment, and the performance of the engine and its emissions were evaluated in various rates of water injection. This study also investigated the impacts of variation of the start of combustion angle on engine output parameters when different rates of water are injected. Processes 2020, 8, 1214 3 of 18

2. Methodology

2.1. Experimental Study Processes 2020, 8, x FOR PEER REVIEW 3 of 18 The KIA Cerato engine was used for this study and the performance data was collected experimentally to validate the AVL model. The technical speciﬁcation of the KIA Cerato engine provided in Table 1. The engine was tested on an engine test bed and its main output parameters is provided in Table1. The engine was tested on an engine test bed and its main output parameters were measured at various speeds under full load condition (Figure 1). During the experimental tests, were measured at various speeds under full load condition (Figure1). During the experimental tests, the engine functional outputs such as BSFC, NOx emission rate, BMEP, torque and power at various the engine functional outputs such as BSFC, NOx emission rate, BMEP, torque and power at various speeds had been recorded. speeds had been recorded. Table 1. Technical specifications of KIA Cerato engine. Table 1. Technical speciﬁcations of KIA Cerato engine. Parameter Unit Value Parameter Unit Value Bore mm 86 BoreStroke mmmm 86 86 Stroke mm 86 Connecting rod length mm 143.5 Connecting rod length mm 143.5 NumberNumber of Cylinders of Cylinders -- 4 4 DisplacementDisplacement volume volume cccc 20002000 MaximumMaximum RPM RPM RPMRPM 70007000 RatedRated RPM RPM RPMRPM 60006000 Compression Ratio 10.5 Compression Ratio 10.5

Figure 1. Experimental testing of KIA Cerato engine on engine test bed.

2.2. Engine Mathema Mathematicaltical Model After completion completion of of the the experimental experimental phase, phase, the the engine engine was was mathematically mathematically modelled modelled using using the theAVL AVL BOOST BOOST software. software. AVL AVL BOOST BOOST provides provides a a 1- 1-DD thermodynamic thermodynamic precise precise model model for for internal combustion enginesengines andand itit isis widelywidely used used in in academia academia and and the the automotive automotive industry. industry. The The AVL AVL model model of theof the KIA KIA Cerato Cerato engine engine is shown is shown in Figure in Figure2. The 2. engineThe engine contains contains 4 gasoline 4 gasoline/ethanol/ethanol injectors injectors (I1, I2, (I1, I3, I4)I2, I3, and I4 one) and water one injectorwater injector (I5). The (I5 engine). The engine cylinders cylinders are named are named C1, C2, C1, C3 andC2, C3 C4, and and C4, the and catalyst the convertercatalyst converter and air cleanerand air arecleaner indicated are indicated as CAT1 as and CAT1 CL1, and respectively. CL1, respectively. PL3 and PL3 PL4 and are PL4 the are engine the muengineﬄer muffler and the measureand the pointsmeasure (MP), points which (MP), are usedwhich for are measuring used for air measuring thermophysical air thermophysical properties in variousproperties sections. in various sections.

Processes 2020, 8, x FOR PEER REVIEW 4 of 18 Processes 2020, 8, 1214 4 of 18

Figure 2. Block diagram of engine model in AVL BOOST software.

Due to the variationFigure of the 2. Block lower diagram heating of valuesengine model with diinﬀ AVLerent BOOST fuels insoftware. dual-fuel (and blended fuels) engines, the equivalent brake speciﬁc fuel consumption (BSFC) should be calculated and used to Due to the variation of the lower heating values with different fuels in dual-fuel (and blended compare the fuel consumptions, as shown in Equation (1): fuels) engines, the equivalent brake specific fuel consumption (BSFC) should be calculated and used to

compare the fuel consumptions, as shown in. Equation (1):. LHVe m + me gasoline LHVgasoline = 퐿퐻푉푒 BSFCeqv 푚̇ 푔푎푠표푙푖푛푒. +푚̇ 푒 (1) W 퐿퐻푉푔푎푠표푙푖푛푒 퐵푆퐹퐶푒푞푣 = engine (1) 푊̇ 푒푛푔푖푛푒 . . . where,where,mgasoline 푚̇ 푔푎푠표푙푖푛푒, me ,and 푚̇ 푒W andengine 푊arė 푒푛푔푖푛푒 the are gasoline the gasoline mass ﬂow mass rate, flow ethanol rate, mass ethanol ﬂow mass rate flow and engine rate and powerengine output power parameters, output parameters, respectively. respectively. TheThe ethanol ethanol was was added added to theto the fuel fuel at 5%at 5% and and 10% 10% volume volume fractions fractions and and the the fuels fuels used used in thisin this study study areare shown shown in Tablein Table2. The 2. The ethanol ethanol volume volume fraction fraction in gasolinein gasoline/ethanol/ethanol mixture mixture injected injected by by I1, I1, I2, I2, I3 andI3 and I4 injectorsI4 injectors are are also also indicted indicted in in this this table. table.

TableTable 2. The2. The speciﬁcation specification of fuelsof fuels used used in thisin this study. study.

FuelFuel Type Type Ethanol Volume Volume Fraction Fraction(%) (%) GasolineGasoline 0 0 E5 (5%(5% ethanol, ethanol, 95% 95% gasoline) gasoline) 5 5 E10 (10%(10% ethanol, ethanol, 90% 90% gasoline) gasoline) 1010

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Water was then injected into the engine in various ratios when needed. The injection of water was continuous. The water injection ratio (WIR) is deﬁned by the Equation (2):

. . WIR = mwater/m f uel (2)

. where the WIR and mwater are the water injection ratio and water mass ﬂow rate, consecutively.

2.2.1. Combustion and Heat Transfer Models The Wiebe two-zone combustion model has been chosen for modelling the combustion procedure in the engine AVL model. In this combustion model, the combustion chamber is divided into two zones (burnt and unburnt zones) in which the mixture temperature for each zone is calculated separately [26,27]. This model is widely used for the modelling of dual-fuel engines with species transport in AVL BOOST [26,27]. In the Wiebe two-zone model, the fuel mass burned fraction (x) during combustion is expressed by Equation (3):

SOCm+1 x = 1 exp [ a ∝ − ] (3) − − BDUR SOC, BDUR, , m and a are the start of the combustion, burn duration, crankshaft angle, ∝ Wiebe shape and Wiebe parameter, respectively. Applying ﬁrst law of thermodynamics to each zone provides: dmbub dVb dQ f X dQwb dmb dmBB,b = Pc + + hu h (4) d − d d − d d − BB,b d ∝ ∝ ∝ ∝ ∝ ∝ dmuuu dVu X dQwu dmB dmBB,u = Pc hu hBB u (5) d − d − d − d − , d ∝ ∝ ∝ ∝ ∝ dVb dQ f dQw dmb dmBB,b where dmu, Pc d , d , d , hu d and hBB,b d are variation of in-cylinder internal energy, piston work, fuel∝ input∝ energy,∝ wall∝ heat losses,∝ enthalpy ﬂow from unburnt to burnt zone and blow by enthalpy, respectively. Furthermore, for modelling heat transfer between walls and mixture, the Woschni 1978 model was employed [28,29].

2.2.2. Emission Model For calculation of the NOx formation rate in AVL BOOST, the Pattas and Hafner equation [26] combined with Zeldovich mechanism [26] were used:

2 r1 r4 rNO = CPPMCKM(2, 0) 1 aNO [ + ] (6) − 1 + aNOAK2 1 + AK4

CNO.act 1 aNO = (7) CNO.equ CKM

r1 AK2 = (8) r2 + r3 r4 AK4 = (9) r5 + r6 where CPPM, CKM, Ci and rNO are the post processing multiplier, kinetic multiplier, molar concentration and reaction rate of NOx, respectively.

2.2.3. Knock Model The knock model is used for calculating the minimum octane number required for working free of knock. It is employed for the assessment of engine knock intensity variation when various fuels are injected [30]. As indicated in Equation (10), Kc is the parameter that identiﬁes the knock onset. In this Processes 2020, 8, 1214 6 of 18 equation, τ is the ignition delay and t is the elapsed time from start of compression; when its value reaches 1 the knocking is initiated [31]. Z t 1 Kc = dt (10) 0 τiD

Furthermore, in knock modelling, the ignition delay has a strong relation with fuel octane number Processesand in-cylinder 2020, 8, x FOR gas PEER thermophysical REVIEW condition [30]: 6 of 18

a ON nB//T τ==A.( ) ). p−e (11(11)) iD · 100 · where , ON, p and T are ignition delay, minimum octane number, pressure and temperature where τ , ON , p and T are ignition delay, minimum octane number, pressure and temperature of of in-cylinderiD gas, consecutively. Moreover, A, a, n and B are constant parameters used in the model in-cylinder gas, consecutively. Moreover, A, a, n and B are constant parameters used in the model which are equal to 17.68, 3.402, 1.7 and 3800 in this study, respectively [30]. which are equal to 17.68, 3.402, 1.7 and 3800 in this study, respectively [30].

2.3.2.3. V Validationalidation TheThe validation validation of of the the computer computer model model was was performed performed by bycomparing comparing the theresults results of running of running the gasolinethe gasoline fueled fueled engine engine at various at various RPMs RPMs in the in engine the engine test room test room with withthe AVL the AVLmodel model outputs. outputs. The engineThe engine BSFC, BSFC, torque torque and andNOx NOx production production were were used used for validat for validationion purposes. purposes. Figure Figure 3a shows3a shows the enginethe engine torque torque and and BSFC BSFC from from the the experiments experiments as aswell well as as the the AVL AVL model. model. Furthermore, Furthermore, the the NOx NOx concentrationsconcentrations from from the the engine engine exhaust exhaust for for both both the the AVL AVL and and experiment experiment are are compared compared in in Figure Figure 3b.3b. ByBy comparing comparing the the experimental experimental and and simulation simulation values, it can can be be found found that that the the maximum maximum error error of of the the AVLAVL model model is is below below 8%, 8%, which which proves proves that the that developed the developed model can model represent can the represent engine performance the engine performancewith a high degree with a ofhigh accuracy. degree of accuracy.

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FigureFigure 3. ((aa)) Engine TorqueTorque andand BSFC BSFC and and ( b()b NOx) NOx concentration concentration in in the the exhaust exhaust in thein the AVL AVL model model and andexperimental experimental tests tests obtained obtained from from running running the enginethe engine by gasoline by gasoline at full at loadfull load and and various various RPMs. RPMs.

2.4.2.4. Design Design of of Experiments Experiments Method Method and and Analysis Analysis TheThe parameters parameters studied studied in in this this research research (design (design variables) variables) w wereere the the start start of of combustion combustion (SOC) (SOC) angle,angle, water water injection injection ratio ratio and and ethanol ethanol volume volume fraction fraction as as presented presented in inTable Table 3.3 As. As it itcan can be be seen seen in thisin this table, table, the the maximum maximum value value of of the the water water injection injection ratio ratio is is 8%, 8%, because because the the R R-square-square value value of of differentdifferent responses inin regressionregression analysis analysis is is higher higher than than 99%, 99%, when when the the water water injection injection ratio ratio is below is below 8%. 8%.The The Latin Latin Hypercube Hypercube sampling sampling method method was used was toused define to thedefine sampling the sampling space. Asspace. shown As inshown Figure in4, Figurethe Latin 4, the Hypercube Latin Hypercube recommended recommended 200 points 200 for points the designfor the variablesdesign variables for this for study. this study. These pointsThese pointswere used were in used the in regression the regression analysis analysis to obtain to obtain the engine the engine output output parameters parameters and and emissions emissions as theas thefunction function of design of design variables variables at the at engine the engine rated rated RPM RPM (6000 (6000 RPM) RPM) at which at which the maximum the maximum power power will be willreached. be reached. The flow The chart flow of chart the researchof the researc methodh method proposed proposed in this in paper this paper is also is shown also shown in Figure in Figure5. 5.

Processes 2020, 8, x FOR PEER REVIEW 7 of 18 Processes 2020, 8, 1214 7 of 18 Processes 2020, 8, x FOR PEER REVIEW 7 of 18 Table 3. Maximum and minimum values of each design parameter. Table 3. Maximum and minimum values of each design parameter. DesignTable Parameter 3. Maximum andUnit minimum Minimum values of each Value design Maximum parameter. Value DesignEthanolDesign Parameter volume Parameter fraction UnitUnit- Minimum Minimum0 Value Value Maximum Maximum0.1 Value Value Ethanol volume fraction - 0 0.1 EthanolWater volume injection fraction ratio -- 0 00.08 0.1 WaterStartWater injection of injection combustion ratio ratio Degree -- −200 00.085 0.08 Start ofStart combustion of combustion DegreeDegree −20 205 5 −

Figure 4. The sampling space and the design points in Latin Hypercube DOE method. Figure 4. The sampling space and the design points in Latin Hypercube DOE method. Figure 4. The sampling space and the design points in Latin Hypercube DOE method.

Figure 5. The research method flow ﬂow chart proposed in this paper. 3. Results and DiscussionFigure 5. The research method flow chart proposed in this paper. 3. Results and Discussion 3. ResultsAs discussed, and Discussion the mathematical model of the KIA Cerato engine in AVL BOOST was developed As discussed, the mathematical model of the KIA Cerato engine in AVL BOOST was developed for this study. The water port injector was added to inject water into the engine at diﬀerent ratios. for thisAs study. discussed, The waterthe mathematical port injector model was added of the KIAto inject Cerato water engine into in the AVL engine BOOST at diff waserent developed ratios. for this study. The water port injector was added to inject water into the engine at different ratios.

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The range of the design variables (SOC, water injection ratio and ethanol volume fraction) were deﬁned in the AVL design explorer and engine output parameters were calculated at engine rated speed (6000 RPM). The general equation format which was developed for each engine output parameter (response) by regression analysis is shown below:

Response = cte + (a SOC) + (b m fe) + (c WIR) + (d SOC m fe)+ × × × × × (12) 2 2 2 (e SOC WIR) + ( f m fe WIR) + g SOC + h m fe + i WIR × × × × × × × where SOC, m fe and WIR are start of combustion, ethanol volume fraction and water injection ratio design parameters, respectively. Equation (12) consists of some constant and multipliers which are calculated and provided in Table4 for each response, with the goodness of ﬁtness analysis for the equations (see Table5). In Table4, cte denotes the constant parameter for each response equation in the regression analysis.

3.1. Engine Performance Parameters The effects of water port injection into the engine for pure gasoline, E5 and E10 at rated RPM and a constant SOC of 5 degree are presented in this section. Figure6 shows the engine power output for − different fuels (gasoline, E5 and E10) and different water injection ratios. As can be seen, when no water is injected into the engine, there was a slight increase in power when using E10 compared to E5 and pure gasoline. This increase in power by injection of ethanol is due to an increase in flame velocity, which is achieved by ethanol injection and resulted in an improvement of the engine performance. Furthermore, with the injection of water, there was an increase in engine power for all three fuels with the maximum engine power output of about 96.75 kW for E10 when the water injection was approximately 8%. Therefore, the combination of E10 fuel and 8% water injection can deliver around a 1.3% increase in engine power output when compared with the gasoline fueled engine. Engine BMEP at varying water injection ratios and fuel types is shown in Figure7. As can be seen, as in the case of power, a small increase in BMEP was observed by shifting to E10 from gasoline or E5. The engine BMEP for each fuel increased slightly with water injection; this increase was approximately 0.02 bar for E5 and 8% water injection compared to pure gasoline without any water injection, and about 0.05 bar when E10 was used. Figure8 presents the impacts of water port injection on engine brake thermal e fficiency at various injection ratios for various fuels. As shown, there is not a significant difference between E5 and E10 in terms of the brake thermal efficiency. Compared with gasoline, brake thermal efficiency increased by about 1% for E10. Furthermore, water port injection increased the engine brake thermal efficiency for all the fuels. It was also found that the combination of ethanol with water injection does not have a negative effect on brake thermal efficiency. Processes 2020, 8, 1214 9 of 18

Table 4. The Equation (6) constant parameters and multipliers.

Responses cte a b c D e f g h i Power 89.840 1.053 3.807 10.930 0.056 0.053 3.817 0.035 2.957 12.480 − − − − − BMEP 8.992 0.105 0.381 1.094 0.006 0.005 0.382 0.004 0.296 1.249 − − − − − Brake power eﬃciency 25.120 0.294 8.725 2.744 0.067 0.008 1.797 0.010 6.177 4.030 − − − − − Peak cylinder 2511 5.705 230 256.400 3.682 0.904 36.830 0.211 170.600 87.120 temperature − − − NOx concentration 3.787 10 4 2.651 10 5 1.688 10 3 7.633 10 4 1.019 10 4 1.545 10 5 0.002 2.357 10 7 0.004 4.331 10 4 × − − × − × − − × − − × − − × − − × − × − Processes 2020, 8, 1214 10 of 18 Processes 2020, 8, x FOR PEER REVIEW 10 of 18 Processes 2020, 8, x FOR PEER REVIEW 10 of 18

Table 5. The ﬁtness goodness for each response equation. Table 5. The fitness goodness for each response equation. Table 5. The fitness goodness for each response equation. Responses p-Value R2 Responses p-Value R2 Responses p-Value R2 PowerPower <0.0001<0.0001 0.99 0.99 PowerBMEP <0.0001<0.0001 0.99 0.99 BMEP <0.0001 0.99 Brake powerBMEP e ﬃciency <0.0001<0.0001 0.99 0.99 Brake power efficiency <0.0001 0.99 BrakePeak cylinder power temperatureefficiency <0.0001<0.0001 0.99 0.99 Peak cylinderCO concentration temperature <0.0001<0.0001 0.99 0.99 Peak cylinder temperature <0.0001 0.99 COHC concentration concentration <0.0001<0.0001 0.99 0.99 CO concentration <0.0001 0.99 HCNOx concentration concentration <0.0001<0.0001 0.99 0.99 HC concentration <0.0001 0.99 NOx concentration <0.0001 0.99 NOx concentration <0.0001 0.99

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Processes 2020, 8, 1214 11 of 18 Processes 2020, 8, x FOR PEER REVIEW 11 of 18

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The engine equivalent BSFC for different different water injection rates rates and and fuels fuels is is presented presented in in Figure Figure 99.. It can be seen that by using E10 instead of of E5, E5, BSFC BSFC was was decreased decreased by by almost almost 2% 2% (to (to 307 307 g/kWh). g/kWh). Comparing E5 and E10 fuels with gasoline, the the engine BSFC BSFC decreased decreased by by nearly nearly 2.3% 2.3% and and 4.5%, 4.5%, respectively. The reason is due to an increase in combust combustionion efficiency efficiency as a result of ethanol injection into the combustion chamber. It It was was also found that the injection of water had a positive impact on BSFC andand thethe engine engine equivalent equivalent BSFC BSFC decreased decreased by by up up to 1% to with1% with water water injection injection for each for fuelingeach fueling mode. mode.Knock onset is one of the most limiting factors in PFI spark ignition engines. It limits the range of fuels,Knock compression onset is ratio one of and the ignition most limiting advances factors that canin PFI be used.spark Itignition is also dependentengines. It limits on the the resulting range ofthermal fuels, level compression of the combustion ratio and chamber. ignition All advances these factors that change can be significantly used. It is also with dependent the use of di onfferent the resultingdegrees of thermal ethanol level and of water the combustion injection. The chamber. mathematical All these model factor useds change for simulating significantly the Knockwith the onset use wasof different presented degrees before of based ethanol on ignitionand water delay, injection. which The depends mathematical on various model parameters used for including simulating octane the Knocknumber, onset pressure was presented and temperature before based of in-cylinder on ignition gas. delay, From thiswhich analysis, depends the on minimum various parameters fuel octane includingnumber required octane for number, preventing pressure engine and knock temperature is obtained of in in this-cylinder study and gas. the From results this are analysis, presented the in minimumFigure 10. fuel As shown, octane number with injection required of ethanol,for preventing there is engine a minimal knock increment is obtained to thein this minimum study and octane the resultsnumber are required presented to avoid in Figure the knocking,10. As shown, so the with new injection fuel should of ethanol, satisfy there this minimumis a minima requirement.l increment toHowever, the minimum by water octane injection number up required to 8% the tominimum avoid the octaneknocking, number so the was new decreased fuel should by satisfy nearly this 1.5. Therefore,minimum itrequirement. can be concluded However, that portby water injection injection of water up isto helping8% the in minimum reducing octane the knock number intensity, was whichdecreased has been by nearly caused 1.5. by Therefore, the injection it ofcan E5 be and concluded E10 fuels. that port injection of water is helping in reducing the knock intensity, which has been caused by the injection of E5 and E10 fuels.

Processes 2020, 8, 1214 12 of 18 Processes 2020, 8, x FOR PEER REVIEW 12 of 18 Processes 2020, 8, x FOR PEER REVIEW 12 of 18

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80.5 80.5 0 0.02 0.04 0.06 0.08 0 0.02 Water inj0.04ection ratio 0.06 0.08 Water injection ratio Figure 10. Minimum octane number in various water injection ratios for each fuel. Figure 10. MinimumMinimum octane octane number number in in var variousious water water injection injection ratios for each fuel. 3.2. NOx Emissions and Peak Cylinder Temperature 3.2. NOx NOx Emissions Emissions and and Peak Peak Cylinder Cylinder Temperature Temperature Figures 11 and 12 show the effect of using gasoline, E5 and E10 fuels on peak cylinder Figures 11 11 and and 12 12 show show the etheﬀect effect of using of gasoline,using gasoline, E5 and E10 E5 fuelsand E10on peak fuels cylinder on peak temperature cylinder temperature and NOx formation at various water injection ratios. Since the cylinder temperature is a temperatureand NOx formation and NOx at variousformation water at various injection water ratios. injection Since the ratios. cylinder Since temperature the cylinder is temperature a key parameter is a keyon NOparameterproduction, on NOX it production, is presented it andis presented discussed and together discussed with together NOx in with this NOx section. in this As section. shown, key parameterX on NOX production, it is presented and discussed together with NOx in this section. As shown, switching to E5 and E10 from pure gasoline resulted in an increase in peak cylinder Asswitching shown, to switching E5 and E10 to E5 from and pure E10 gasoline from pure resulted gasoline in an resulted increase in in an peak increase cylinder in peak temperature, cylinder temperature, thus increasing the formation of NOx by 22% and 48%, respectively. However, the peak temperature,thus increasing thus the increasing formation the of formati NOx byon 22%of NOx and by 48%, 22% respectively.and 48%, respectively. However, However, the peak the cylinder peak cylinder temperature showed a decreasing trend with water injection for all fuels. Therefore, water cylindertemperature temperature showed a showed decreasing a decreasing trend with trend water with injection water for injection all fuels. for Therefore, all fuels. water Therefore, injection water can injection can be used for reducing NOx production when using biofuels. Comparing E5 and E10, injectionbe used for can reducing be used NOx for productionreducing NOx when production using biofuels. when Comparing using biofuels. E5 and Comparing E10, NOxconcentration E5 and E10, NOx concentration increased by about 22% by fuel shift, however, the injection of water showed a NOxincreased concentration by about increased 22% by fuel by about shift, however,22% by fuel the shift, injection however, of water the injection showed of a positivewater showed eﬀect ina positive effect in reducing NOx, with a reduction in NOx concentration of up to 8%. positivereducing effect NOx, in with reducing a reduction NOx, with in NOx a reduction concentration in NOx of upconcentration to 8%. of up to 8%.

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25802580

)

( ( GGaassoolilninee

e e EE55

r r 25702570

u E10 u E10

e 2560 e 2560

y y 2550

c 2550

P 25402540

00 0.020.02 0.040.04 0.060.06 0.080.08 WWaatteerr iinnjjeeccttiioonn rraattiioo FigureFigureFigure 11. 11. 11. Peak PeakPeak cylinder cylinder cylinder temperature temperature temperature in in in various various various water water water injection injection injection ratios ratios ratios for for for eac eac eachhh fuel. fuel. fuel.

900900

)

m m 800800

(

r r 700

t 700

c c Gasoline n Gasoline

c c EE55

x x 600600 EE1100

500500 00 0.020.02 0.040.04 0.060.06 0.080.08 WWaatteerr iinnjjeeccttiioonn rraattiioo FFigureFigureigure 12. 12. 12. NOx NOxNOx concentration concentration concentration in in in various various various water water water injection injection injection ratios ratios ratios for for for each each each fuel. fuel. fuel. 3.3. The Effects of Start of Combustion Parameter 3.3.3.3. TheThe Effects Effects of of Start Start ofof Combustion Combustion Parameter Parameter In this section, the effect of water injection with various ratios on engine main parameters such as InIn thisthis section,section, thethe effecteffect ofof waterwater injectioninjection withwith variousvarious ratiosratios onon engineengine mainmain parametersparameters suchsuch engine power and NOx production for E5, E10 and gasoline fuel at varying ignition timing (SOC) are asas engine engine power power and and NOx NOx production production for for E5, E5, E10 E10 and and gasoline gasoline fuel fuel atat varying varying ignition ignition timing timing (SOC) (SOC) presented. The start of combustion parameter is one of the important parameters in engine research. areare presented. presented. The The start start of of combustion combustion parameter parameter is is one one of of the the important important parameters parameters in in engine engine It shows the crank angle position when the combustion starts. The effects of start of combustion on research.research. It It shows shows the the crank crank angle angle position position when when the the combustion combustion starts. starts. The The effects effects ofof start start of of engine power output at various water injection ratios are shown in Figure 13a–c. As can be seen, combustioncombustion onon engineengine powerpower outputoutput atat variousvarious waterwater injectioninjection ratiosratios areare shownshown inin FigureFigure 13a13a––c.c. AsAs the engine ignition timing has a significant effect on engine power for all the fuels. The variation of the cancan bebe seen,seen, thethe engineengine ignitionignition timingtiming hashas aa significantsignificant effecteffect onon engineengine powerpower forfor allall thethe fuels.fuels. TheThe engine power by SOC was much more significant compared to water injection. Therefore, with water variationvariation of of the the engine engine power power by by SOC SOC was was muchmuch more more significant significant compared compared to to water water injection. injection. injection up to 8%, there was no significant effect on engine power output, as compared with SOC. Therefore,Therefore, withwith waterwater injectioninjection upup toto 8%,8%, therethere waswas nono significantsignificant effecteffect onon engineengine powerpower output,output, asas For instance, increasing the water injection rate by up to 8% led to an increase in power of nearly 1%, comparedcompared withwith SOC.SOC. ForFor instance,instance, increasingincreasing thethe waterwater injectioninjection raterate byby upup toto 8%8% ledled toto anan increaseincrease while advancing the start of combustion from 5 to 20 degrees resulted in an increase in engine power inin ppowerower ofof nearlynearly 1%,1%, whilewhile advancingadvancing thethe startstart ofof− combustioncombustion fromfrom 55 toto −20−20 degreesdegrees resultedresulted inin anan by 17%. The maximum power production occurred when SOC was equal to 15 degrees. increaseincrease inin engineengine powerpower byby 17%.17%. TheThe maximummaximum powerpower productionproduction occurredoccurred− whenwhen SOCSOC waswas equalequal toto −15 −15 degrees. degrees.

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95 95

)

W 100 W

k k 100

(

w w 90 90

95 SOC=-20 (deg) SOC=0 (deg) SOC=-20 (deg) SOC=0 (deg) e 95

)

n n SOC=-15 (deg) SOC=5 (deg) SOC=-15 (deg) SOC=5 (deg)

g SOC=-10 (deg) g SOC=-10 (deg)

(

SOC=-5 (deg) SOC=-5 (deg)

E E 85

e 85 e

w w 90 90

SOC=-20 (deg) SOC=0 (deg) SOC=-20 (deg) SOC=0 (deg)

n n SOC=-15 (deg) SOC=5 (deg) SOC=-15 (deg) SOC=5 (deg)

g SOC=-10 (deg) g SOC=-10 (deg)

n 80 n SOC=-5 (deg) 80 SOC=-5 (deg)

E E 85 0 85 0.02 0.04 0.06 0.08 0 0.02 0.04 0.06 0.08 Water injection ratio Water injection ratio

80 (a) 80 (b) 0 0.02 0.04 0.06 0.08 0 0.02 0.04 0.06 0.08 Water injection ratio Water injection ratio 100 (a) (b)

100 95

)

(

r 95

)

w 90 W

(

r SOC=-20 (deg) SOC=0 (deg)

n SOC=-15 (deg) SOC=5 (deg)

w i 90

g SOC=-10 (deg)

n SOC=-S5O (dCe=g-2)0 (deg) SOC=0 (deg)

85 n SOC=-15 (deg) SOC=5 (deg)

g SOC=-10 (deg)

n SOC=-5 (deg)

E 85

80 0 0.02 0.04 0.06 0.08 80 Water injection ratio 0 0.02 0.04 0.06 0.08 Water injection ratio (c) (c) Figure 13. Engine power in various water injection ratios and start of combustion angles for gasoline Figure 13. Engine power in various water injection ratios and start of combustion angles for gasoline (aFigure), E5 (b 13.) andEngine E10 ( powerc). in various water injection ratios and start of combustion angles for gasoline (a), E5(a), ( bE5) and(b) and E10 E10 (c). (c). Figure 14a–c demonstrate the variation of NOx concentration in engine exhaust gas with FigureFigure 14a–c 14a demonstrate–c demonstrate the variationthe variation of NOx of NOx concentration concentration in engine in engine exhaust exhaust gas gas with with diff erent different water injection ratios and start of combustion for gasoline, E5 and E10 fuels, respectively. waterdifferent injection water ratios injection and start ratios of and combustion start of combustion for gasoline, for E5gasoline, and E10 E5 and fuels, E10 respectively. fuels, respectively. Despite the DespiteDespite the positive the positive effect effect of SOCof SOC on on power, power, it it resulted resulted in aa negative negative effect effect on on NO NOx. Thisx. This is due is dueto the to the positive effect of SOC on power, it resulted in a negative effect on NO . This is due to the extra energy extra extraenergy energy released released in the in the combustion combustion chamber chamber and and the simultaneoussimultaneous xincrease increase in flamein flame temperature temperature released in the combustion chamber and the simultaneous increase in flame temperature by changing by changingby changing the SOC. the SOC. As Ascan can be beseen seen from from this this figure figure and waswas discussed discussed before, before, the the injection injection of water of water the SOC. As can be seen from this figure and was discussed before, the injection of water can reduce can reducecan reduce the NOxthe NOx concentration. concentration. Thus, Thus, water water injectioninjection andand tuning tuning SOC SOC should should be combinedbe combined to to the NOx concentration. Thus, water injection and tuning SOC should be combined to achieve the best achieveachieve the best the bestperformance performance of ofthe the engine engine for for power power delivery as as well well as as NOx NOx emiss emission.ion. performance of the engine for power delivery as well as NOx emission.

1000 1200 1000

) 1200

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)

(

) 1000

800

m ( 800

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(

a ( 800 a 600

o 600

t e 400

a 400600

e e 400

c 200

c 200 O 400 SOC=-20 (deg)

SOC=-20 (deg) n

O n SOC=0 (deg) SOC=0 (deg)

o SOC=-15 (deg)

N SOC=-15 (deg) c SOC=5 (deg)

SOC=5 (deg) c SOC=-10 (deg)

0 SOC=-10 (deg) x

x 200 SOC=-5 (deg) 200 0SOC=-20S O(dCe=g-)5 (deg) O SOC=-20 (deg) O SOC=0 (deg) SOC=0 (deg) N SOC=-15 (deg) N SOC=-15 (deg) SOC=5 (deg) 0 0.02 0.04SOC=5 (deg) 0.06 0.08 0 SOC=-10 (dWeg)ater injection ratio SO0C=-10 (deg) 0.02 0.04 0.06 0.08 SOC=-5 (deg) 0 SOC=-5 (deg) Water injection ratio 0 0.02 0.04 0.06 0.08 0 0.02 0.04 0.06 0.08 Water injection ratio Water in(jeact)i on ratio (b) (a) (b)

Figure 14. Cont.

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1200

) 1000

( 800

a 600

e c 400

x 200 O SOC=-20 (deg) N SOC=-15 (deg) SOC=0 (deg) SOC=5 (deg) 0 SOC=-10 (deg) SOC=-5 (deg)

0 0.02 0.04 0.06 0.08 Water injection ratio (c)

FigureFigure 14. 14.NOx NOx concentration concentration in variousin various water water injection injection ratios ratios and and start start of combustionof combustion angles angles for for gasolinegasoline (a), ( E5a), (E5b) and(b) and E10 E10 (c). (c).

4. Conclusions4. Conclusions TheThe impact impact of port of port water water injection injection on performance on performance and emissions and emissions in a spark in ignitiona spark engineignition fueled engine by gasolinefueled by and gasoline biofuel and were biofuel investigated were investigated in this paper. in this Experimental paper. Experimental tests on a KIAtests Ceratoon a KIA engine Cerato wereengine performed were performed to obtain the to main obtain engine the main functional engine parameters functional atparameters various RPMs. at various Then, RPMs. the proposed Then, the engineproposed was modeled engine numericallywas modeled in AVLnumerically BOOST software,in AVL BOOST and the software, results of and modelling the results were of compared modelling withwere the experimental compared with test the results experimental for validation test purposes. results for The validation Latin Hypercube purposes. sampling The Latin method Hypercube was usedsampling to apply method the design was of used experiment to apply (DOE) the method design of for experiment deﬁning the (DOE) minimum method number for definingof design the pointsminimum required number in the of AVL design software. points Regression required in analysis the AVL was software. employed Regression following analysis the DOE was method employed to deﬁnefollowing the equationsthe DOE method for each to engine define output the equations parameter for basedeach engine on the output design parameter variables. based The main on the conclusionsdesign variables. drawn from The thismain paper conclusions are presented drawn asfrom follows: this paper are presented as follows:

- - IncreasingIncreasing the the ethanol ethanol fraction fraction from from E5 to E5 E10 to resultedE10 resulted in a smallin a small increase increase in the in power the power output output of theof engine. the engine. - - AddingAdding ethanol ethanol also also showed showed a small a small positive positive impact impact on BMEP.on BMEP. - - ComparingComparing E5 andE5 and E10 E10 fuels fuels with with gasoline, gasoline, the the engine engine BSFC BSFC decreased decreased by by nearly nearly 2.3% 2.3% and and 4.5%, 4.5%, respectively.respectively. So, So, a better a better fuel fuel economy economy and and reduction reduction in greenhouse in greenhouse gas emissions gas emissions are expected are expected as a resultas a result of an increaseof an increase in the in ethanol the ethanol content. content. - - WithWith the the combination combination of E10of E10 fuel fuel and and 8% 8% water water injection, injection, an increasean increase of approximatelyof approximately 1.3% 1.3% in in engineengine power power output output can can be obtained,be obtained, when when compared compared with with a gasoline a gasoline fueled fueled engine. engine. - The break thermal efficiency was not changed significantly between E5 and E10. Compared with - The break thermal efficiency was not changed significantly between E5 and E10. Compared with gasoline, the brake thermal efficiency increased by about 1% for E10. Water injection did not gasoline, the brake thermal efficiency increased by about 1% for E10. Water injection did not make any significant difference in improving the thermal efficiency for all fuels. make any significant difference in improving the thermal efficiency for all fuels. - By using E10 instead of E5, BSFC decreased by approximately 2% to 307 g/kWh. Comparing E5 - By using E10 instead of E5, BSFC decreased by approximately 2% to 307 g/kWh. Comparing E5 and E10 fuels with gasoline, the engine BSFC decreased by nearly 2.3% and 4.5%, consecutively. and E10 fuels with gasoline, the engine BSFC decreased by nearly 2.3% and 4.5%, consecutively. - Changing the fuel from gasoline to E5 and E10 resulted in an increase in peak cylinder - Changing the fuel from gasoline to E5 and E10 resulted in an increase in peak cylinder temperature, temperature, which led to an increase in NOx formation of up to 22% and 48%, for E5 and E10, which led to an increase in NOx formation of up to 22% and 48%, for E5 and E10, respectively. respectively. - - WaterWater injection injection can can reduce reduce the the NOx NOx formation formation rate rate by upby toup nearly to nearly 8%. 8%. - - TheThe engine engine power power generation generation rate rate has has changed changed slightly slightly as aas result a result of theof the injection injection of waterof water at at variousvarious ratios ratios for for diff differenterent values values of SOC. of SOC.

AuthorAuthor Contributions: Contributions:F.S., F.S., M.B., M.B., and and A.Z., A.Z., Conceptualization, Conceptualization, methodology, methodology, simulation; simulation; S.V.H., S.V.H., A.G., A.G., and and F.S., F.S., Experiments,Experiments, validation; validation; F.S., F.S., M.B., M.B., A.Z., A.Z., M.D.R.-M., M.D.R.-M., S.V.H., S.V.H., A.G., A.G., A.N. A.N. and and M.L.B., M.L.B., Analysis; Analysis; F.S., F.S., and and A.G., A.G., Visualization;Visualization; S.V.H., S.V.H M.B.,., M.D.R.-M., M.B., M.D.R. Resources;-M., Resources; F.S., and M.B.,F.S., andWriting—draft M.B., Writing preparation;—draft A.Z.,preparation; M.B., M.D.R.-M., A.Z., M.B., A.N.,M.D.R. and M.L.B.,-M., A.N., Writing—review and M.L.B., Writing and editing;—review M.B., and and editing; A.Z., Supervision. M.B., and A.Z., All authorsSupervision. have readAll authors and agreed have to read theand published agreed version to the published of the manuscript. version of the manuscript.

Funding: This research received no external funding.

Processes 2020, 8, 1214 16 of 18

Funding: This research received no external funding. Acknowledgments: AVL list GmbH support for proving the simulation tools for the University of Salford through their University Partnership Program, which is greatly appreciated. Special thanks to the Dina Motors company for their support during this research. Conﬂicts of Interest: The authors declare no conﬂict of interest.

Nomenclature

DOE Design of experiment I Injector C Cylinder CAT Catalyst converter CL Air cleaner MP Measure point PL Plenium BSFC Brake specific fuel consumption [g/kWh] WIR Water injection ratio mf Mass fraction SOC Start of combustion BDUR Burn duration Crank shaft angle ∝ m Wiebe shape a Wiebe parameter η Overall efficiency E Engine SB System boundary CO Carbon monoxide NOx Nitrogen oxide COVID-19 Corona virus BMEP Brake mean effective pressure [bar] WLTP Worldwide harmonised light vehicle test procedure Subscripts eqv Equivalent u Unburnt b Burnt w Wall heat loss f Fuel

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