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Combustion and Emissions Characteristics of the Turbine Engine Fueled with HEFA Blends from Different Feedstocks

Combustion and Emissions Characteristics of the Turbine Engine Fueled with HEFA Blends from Different Feedstocks

Article and Emissions Characteristics of the Fueled with HEFA Blends from Different Feedstocks

Bartosz Gawron 1,* , Tomasz Białecki 1 , Anna Janicka 2 and Tomasz Suchocki 3 1 Division for and , Air Force Institute of , 01-494 Warsaw, Poland; [email protected] 2 Division of Automotive , Faculty of Mechanical Engineering, Wroclaw University of Science and Technology, Wyb. Wyspianskiego 27, 50-370 Wroclaw, Poland; [email protected] 3 Turbine Department, Institute of Fluid Flow Machinery, Polish Academy of Sciences, Fiszera 14, 80-231 Gdansk, Poland; [email protected] * Correspondence: [email protected]; Tel.: +48-261-851-448

 Received: 30 January 2020; Accepted: 7 March 2020; Published: 10 March 2020 

Abstract: In the next decade, due to the desire for significant reduction in the carbon footprint left by the sector and the development of a sustainable alternatives to , from renewable sources will play an increasing role as a for turbine . Currently, apart from five types of containing synthesized that are certified by the ASTM D7566 standard, there is yet another synthetic blending component that is at the stage of testing and certification. Hydroprocessed esters and fatty acids enable the production of a synthetic component for jet fuel from any form of native fat or . Used feedstock affects the final synthetic blending component composition and consequently the properties of the blend for jet fuel and, as a result, the operation of turbine engines. A specialized laboratory test rig with a miniature engine was used for research, which is an interesting alternative to complex and expensive tests with full scale turbine engines. The results of this study revealed the differences in the parameters of engine performance and emission characteristics between tested fuels with synthetic blending components and neat jet fuel. The synthetic blending component was obtained from two different feedstock. Noticeable changes were obtained for fuel consumption, CO and NOx emissions. With the addition of the hydroprocessed esters and fatty acids (HEFA) component, the fuel consumption and CO emissions decrease. The opposite trend was observed for NOx emission. The tests presented in this article are a continuation of the authors’ research area related to alternative fuels for aviation.

Keywords: alternative fuels; emissions; HEFA process; synthetic blending component; turbine engine

1. Introduction

Aircraft engines emit pollutants, among which (CO2) is the most significant (GHG), which boosts climate change. The aviation industry is responsible for approx. 2% of all anthropogenic CO2 emissions worldwide [1]. Non-CO2 emissions of jet fuel combustion (vapor trail, nitrous oxide and soot aerosols) raise the contribution of aviation to climate change up to 4.9% [2]. International Air Association (IATA), the global trade association, adopted ambitious targets to mitigate CO2 emissions. There has been an average improvement in fuel efficiency of 1.5% per year from 2009 to 2020, carbon-neutral growth from 2020 and a halving of emissions by 2050 relative to 2005 levels [3]. The widespread use of fuels from renewable sources is a key measure to meet the set assumptions.

Energies 2020, 13, 1277; doi:10.3390/en13051277 www.mdpi.com/journal/energies Energies 2020, 13, 1277 2 of 12

One of the ways to reduce the negative impact of aviation on the environment is the use of alternative fuels. The ASTM D7566 standard [4] has approved five types of aviation turbine fuels for turbine engines from a feedstock other than petroleum, which can contain up to 50% synthetic component. Hydroprocessed esters and fatty acids (HEFA) are one of the approved processes for obtaining alternative fuels which are also known as hydroprocessed renewable jet (HRJ). The HEFA process consists in obtaining paraffins by chemical conversion of triglycerides by of triglycerides, monoglycerides, diglycerides, as well as free fatty acids and their esters. Hydrogenation removes from the molecules of esters of fatty acids and free fatty acids. The next production stages include hydrocracking, hydroisomerization, isomerization, fractionation or the combination of these. The production of these hydrocarbons can use other typical refinery processes [5,6]. The produced fuel containing synthesized hydrocarbons is chemically almost identical with conventional fuel, and it even exceeds some requirements set down for conventional turbine . It differs from fossil fuel in that it consists of exclusively paraffin hydrocarbons. These fuels do not contain aromatic compounds or sulfur. The feedstocks which are used for HEFA blending component production include vegetable (jatropha, camelina), animal fats (), waste cooking oils and microalgal oils. Fuels from HEFA process, as other alternative fuels obtained from the approved for aviation, constitute the so-called drop-in fuel, which means that they are fully interchangeable and compatible. They do not require any changes in engines, fuel systems and fuel distribution networks. If a synthetic blending component is blended with conventional fuel, it must comply with ASTM D7566 requirements. However, each subsequent fuel recertification is carried out only and exclusively for compliance with the conventional fuel requirement—ASTM D1655 [7]. Alternative fuels tests may have a different nature and scope. It is possible to find numerous publications [8–13] on the tests of alternative fuels for gas ; these, however, do not mention a direct possibility of using them in aviation. There are several researchers who have tested alternative fuels for aviation application [14–18]. Some authors focused only on the tests of HEFA blends obtained from different feedstock [19–24]. The ASTM D7566 allowed five technologies with which synthetic blending components can be produced. The aforesaid standard contains detailed information on manufacture that must be applied to obtain each synthetic component but does not indicate which feedstock can be used. Feedstock is known to affect the chemical composition of jet fuel, which translates into its physicochemical properties, and this may have an adverse effect on the operation of the turbine engine. The combustion characteristics of fuel, especially in the context of gaseous emissions, are very much important due to GHG emissions and climate change. Zhang et al. [25] reviewed turbine engine tests to evaluate their performance and pollutant emissions while using alternative jet fuels. Engine tests have been conducted on various engines: many types of aero-engines such as , and APUs. Yang et al. [26] presents a review of the characteristics including gaseous emissions of bio-jet fuels. He remarks/observes that engine tests with alternative fuels are carried out on full-size engines, which entails huge costs. It is worth noting that there was one research related to small scale engine tests (SR-30 engine) [25]. The miniature engine tests, especially stationary power units, are an interesting solution in the field of alternative fuels. The aim of this study is the performance and emissions characteristics of a small scale turbojet engine fed with Jet A-1/HEFA blending component obtained from camelina and used cooking oil (UCO). The blend results were compared with those obtained for neat Jet A-1.

2. Materials and Methods

2.1. Description of the Test Rig The tests were carried out on the GTM-140 miniature turbojet engine, being a part of the laboratory test rig, MiniJETRig (Miniature Test Rig), for aviation fuel combustion process research. Energies 2020, 13, 1277 3 of 12

Gawron and Białecki [27] presented in detail the construction and research capabilities of the test rig and the technical specification and measurements of the miniature turbojet engine [28] (Table1). For these tests, the engine with pneumatic start-up and a straight duct in the exhaust system was selected, which allows for obtaining the maximum of 70 and enables the measurement of the mass flow rate. In order to minimize the effect of dilution of , a gas analyzer measuring 1 probe was placed centrally at a distance of not more than 2 of the diameter of the engine exhaust , in accordance with ARP 1256 [29].

Table 1. Details of measurement equipment for gas emissions.

Parameter Sensor Type Range Least Count Accuracy CO electrochemical 0–2000 0.1 ppm 5% measured value ± CO infrared 0–25 0.01% 5% measured value 2 ± NO electrochemical 0–500 0.1 ppm 5% measured value ± NO electrochemical 0–100 0.1 ppm 5 ppm 2 ±

The fact that lubrication of bearings is mainly carried out in the open system by adding oil to the fuel is an unfavorable factor for conducting the research on miniature engines because it has a negative impact on combustion assessment, especially in terms of exhaust emissions. Oil flow contained in the fuel was eliminated by splitting the power supply into two independent systems. Owing to this fact, the fuel reaching the becomes neat test fuel. The miniature turbojet engine GTM-140 is used not only in aviation alternative fuels research area but also for emission toxicity tests. The results of the preliminary studies were presented by Gawron et al. [30,31] and Janicka et al. [32].

2.2. Tested Fuels The tests made use of the widely used Jet A-1 fuel and its blends with the component obtained from HEFA technology, described by Gutiérrez-Antonio et al. [5] in detail. The feedstocks of synthetic blending components are camelina oil plant and UCO. A blend of Jet A-1 with the HEFA component derived from camelina was marked as HEFA CAM, whereas, the one from UCO was marked as HEFA UCO. The synthetic blending component content makes up respectively 48% and 50%. UCO is a waste from the , and it has a limited use. Since it does not compete with a food chain, and offers a significant reduction in CO2 emissions, it is qualified as sustainable feedstock, whereas is a plant that produces inedible oil seeds. This feedstock can be grown on marginal land, which is not currently used, does not compete with other plants and yields an excellent crop. The tested conventional fuel meets the requirements of ASTM D1655, while the synthetic components and its blends complies with the standard of ASTM D7566. Table2 presents the selected physicochemical properties of all tested fuels.

Table 2. Jet A-1 and Hydroprocessed esters and fatty acids (HEFA) blends selected properties.

Limits ASTM Results Property Unit D1655/D7566 Jet A-1 HEFA CAM HEFA UCO Density at 15 C kg/m3 775.0 840.0 790.2 779.9 771.1 ◦ ÷ Viscosity in 20 C mm2/s Max 8.0 3.117 4.968 3.514 − ◦ Heat of combustion MJ/kg Min 42.8 43.307 43.691 43.744 ◦C Min 38 42.0 44.5 43.5 Freezing point C Max 40 63.8 57.5 51.5 ◦ − − − − Smoke point mm Min 18 25.0 25.0 26.0 Naphthalenes (v/v) % Max 3.0 0.47 0.57 0.24 Aromatics (v/v) % Max 25 15.0 9.1 7.2 Energies 2020, 13, 1277 4 of 12

The analysis of laboratory results shows that input of HEFA component did not cause significant changesEnergies in 20 selected20, 13, x FOR physicochemical PEER REVIEW properties. The density and the content of aromatics4 reduction of 12 was observedThe analysis in relation of laboratory to neat Jet results A-1. shows However, that there input occurred of HEFA an component increase did in viscosity not cause at the temperature of 20 C and in the heat of combustion. High viscosity can contribute to poor atomization, significant changes− ◦ in selected physicochemical properties. The density and the content of aromatics whichreduction in turn causeswas observed incomplete in relation combustion. to neat Jet A-1. However, there occurred an increase in viscosity atIt the was temperature also observed of –20 a °C deterioration and in the heat of propertiesof combustion. of HEFAHigh viscosity blends can at lowcontribute temperatures, to poor the parameter,atomization, in which which case in turn the fulfilmentcauses incomplete of requirements combustion. was unreachable by first generation (candidatesIt was for also the aviation observed turbine a deterioration fuel). However, of properties the of obtained HEFA blends values at lo arew su temperaturesfficient to, meetthe the requirementsparameter, of in the which applicable case the standards.fulfilment of requirements was unreachable by first generation biofuels (candidates for the aviation turbine fuel). However, the obtained values are sufficient to meet the 2.3. Procedurerequirements and of Test the Conditions applicable standards.

2.3.Bench Procedure tests wereand Test carried Conditions out in accordance with a methodology and profile of the engine run presentedBench in Reference tests were [28 carried]. The out selected in accordance four rotational with a methodology speeds correspond and profile to variousof the engine characteristic run operatingpresented modes in Reference of the turbine [28]. The engine. selected The four engine rotational run speeds time atcorrespond a given speedto various has characteristic been selected to guaranteeoperating the modes stability of ofthe the turbine measured engine. parameters. The engine run time at a given speed has been selected to guaranteeA slight changethe stability was of madethe measured in the parameters. above-mentioned methodology. The rotational speed of 39,000 rpmA slight(idle) change was replaced was made with in the 45,000 above rpm,-mentioned which methodology. was necessitated The rotational by the problems speed of 39 connected,000 withrpm the fuel(idle) flow was measurementreplaced with 45 in,000 the rpm, initial which operating was necessitated range of a fuelby the consumption problems connected sensor atwith the low rotationalthe fuel speed. flow measurement Figure1 demonstrates in the initial the operating modified range test profile.of a fuel consumption sensor at the low rotational speed. Figure 1 demonstrates the modified test profile.

Figure 1. Figure 1.Modified Modified profil profilee of of engine engine test test..

In orderIn order to minimize to minimize the the impact impact on on ambient ambient conditions,conditions, which which affects affects both both the theengine engine performance performance and theand characteristicthe characteristic of of gaseous gaseous emissions, emissions, the bench bench tests tests were were carr carriedied out outin the in same the same day. day.Table Table3 3 presentspresents the the detailed detailed ambient ambient conditions, conditions, i.e. i.e.,, pressure, pressure, temperature temperature and relative and relative humidity. humidity.

TableTable 3. 3.Ambient Ambient test test conditions conditions..

Fuel Test No. Po (hPa) To (oC) RH (%) Fuel Test No. Po (hPa) To (◦C) RH (%) Test 1 995.2 27.9 62.0 Test 1 995.2 27.9 62.0 Jet A-1 Jet A-1 Test 2 Test 2 995.1995.1 28.828.8 60.3 60.3 Test 1 994.3 30.7 50.2 Test 1 994.3 30.7 50.2 HEFA CAM HEFA CAM Test 2 Test 2 994.1994.1 31.031.0 48.5 48.5 Test 1 Test 1 994.8994.8 29.429.4 55.9 55.9 HEFA UCO HEFA UCO Test 2 Test 2 994.7994.7 29.929.9 52.8 52.8

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2.4. Uncertainty Analysis Experiments for each tested fuel were executed twice. The analyzed parameters in every individual test were averagedEnergies 2020, 1 in3, x selectedFOR PEER REVIEW sets of measurement data, characterized by small values5 of of12 standard deviations. Next, the results were averaged. The average value of each parameter was supplemented with a maximum2.4. Uncertainty and minimumAnalysis value, which correspond to the extreme values from single engine runs [21]. UncertaintyExperiments of measurement for each tested equipmentfuel were executed was presented twice. The in analyzed [28] (engine parameters sensors) in every and [13] (gas analyzer sensors).individual test were averaged in selected sets of measurement data, characterized by small values of standard deviations. Next, the results were averaged. The average value of each parameter was supplemented with a maximum and minimum value, which correspond to the extreme values from 3. Resultssingle and Discussion engine runs [21]. Uncertainty of measurement equipment was presented in [28] (engine sensors) and [13] (gas analyzer sensors). 3.1. Combustion Characteristics 3. Results and Discussion The results of the engine tests for two different synthetic blending components obtained from the same HEFA3.1. Combustion technology Characteristics were compared with those for conventional aviation turbine fuel Jet A-1. Due to high measurementThe results of the uncertainty engine tests for of thetwo performancedifferent synthetic parameters blending components at 45,000 obtained rpm, thefrom analysis of results at thisthe same speed HEFA was technology omitted. were compared with those for conventional aviation turbine fuel Jet A-1. Due to high measurement uncertainty of the performance parameters at 45,000 rpm, the analysis of Figure2 shows the results for thrust (K), fuel consumption (C f), thrust-specific fuel consumptions results at this speed was omitted. (TSFC) and turbine temperature (T4), whereas Figures3–5 present relative changes of thrust, fuel Figure 2 shows the results for thrust (K), fuel consumption (Cf), thrust-specific fuel consumptionconsumptions and TSFC (TSFC) of a and diff turbineerent temperatu feedstockre (T4), of the whereas synthetic-blending-component-fed Figures 3–5 present relative changes of engine in relation tothrust, neat Jetfuel A-1. consumption and TSFC of a different feedstock of the synthetic-blending-component-fed This sectionengine in may relation be dividedto neat Jet by A-1. subheadings. It should provide a concise and precise description of This section may be divided by subheadings. It should provide a concise and precise the experimentaldescription results, of the theirexperimental interpretation results, their as wellinterpretation as the experimental as well as the experimental conclusions conclusions that can be drawn. Withinthat the can range be drawn. of the engine thrust (Figure3), values of this parameter for HEFA blends are higher as comparedWithin the with range those of the for engine neat thrust Jet A-1. (Figure The 3), higher values of thrust this parameter values for obtained HEFA blends for HEFA are blends result fromhigher their as highercompared combustion with those for heat.neat JetHowever, A-1. The higher as thethrust speed values increases,obtained for theseHEFA blends differences are result from their higher combustion heat. However, as the speed increases, these differences are becomingbecoming smaller. smaller. This may This may be related be related to to measurement measurement accuracy accuracy of the of a thepplied applied sensor, which sensor, is which is characterizedcharacterized by greater by greater inaccuracy inaccuracy when when measuring measuring low low thrust. thrust.

Figure 2. Cont.

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Energies 2020, 13, 1277 6 of 12 Energies 2020, 13, x FOR PEER REVIEW 6 of 12

Figure 2. Selected engine parameters as a function of rotational speed. (A) thrust, (B) fuel Figureconsumption, 2. SelectedFigure (C 2). turbineengineSelected parametersenginetemperature, parameters as a( Das function) a thrust function ofspecific of rotational rotational fuel speed. speed.consumptions. (A ()A thrust,) thrust, (B ) fuel (B) fuel consumption, (C) turbineconsumption, temperature, (C) (turbineD) thrust temperature, specific (D fuel) thrust consumptions. specific fuel consumptions.

Figure 3. Changes of engine thrust for synthetic blending components with regard to Jet A-1.

The fuel consumption for both blends with synthetic blending component (Figure 4) during Figure 3. Changes of engine thrust for synthetic blending components with regard to Jet A-1. Figureengine 3. testsChanges on all of rotational engine thrustspeeds foris characterized synthetic blending by a lower components value than thatwith for regard Jet A- 1.to Most Jet A of-1. these differences are above the range of measurement error of the sensor (accuracy ±2% for turbine The fuelflow consumption meter). The results for are both determi blendsned bywith the synthetic physicochemical blending properties component of tested fuels. (Figure Both4 ) during engineThe tests fuelHEFA on consumption allblends rotational compared for speeds to both Jet A is- blends1 characterizedfuel are with characterized synthetic by a by lower lower blending valuedensity component than and higher that forcombustion (Figure Jet A-1. 4) Most during of enginethese di testsfferencesheat. on all are rotational above the speeds range is of characterized measurement by error a lower of the value sensor than (accuracy that for Jet2% A for-1. Most turbine of ± theseflow meter).differences TheTSFC resultsare (Figure above are 5) for determinedthe the range HEFA of blendsby measurement the are physicochemical characterized error by of lower the properties values sensor compared of(accuracy tested with fuels. ±Jet2% A - Bothfor1. turbine HEFA flow meter).The Thedifferences results between are determi fuels are nedgetting by smaller the physicochemical as the speed increases. properties This is caused of testedby smaller fuels. Both blends compareddifferences to in Jet engine A-1 thrust fuel are at higher characterized rotational spee byds. lower density and higher combustion heat. HEFATSFC blends (Figure compared5) for the to HEFAJet A-1 blends fuel are are characterized characterized by by lower lower density values and compared higher withcombustion Jet A-1. heat.The di fferences between fuels are getting smaller as the speed increases. This is caused by smaller differencesTSFCEnergies (Figure in engine 2020 , 5)13, xfor thrust FOR the PEER atHEFA REVIEW higher blends rotational are characterized speeds. by lower values compared7 ofwith 12 Jet A-1. The differences between fuels are getting smaller as the speed increases. This is caused by smaller differences in engine thrust at higherCf rotational speeds.HEFA UCO HEFA CAM 0

-0.5

1 1 [%] - -1 -1.5 -2 -2.5 -3 -3.5 Change wrt Jet A -4 70000 88000 112000

Rotational speed [rpm] Figure 4. FigureChanges 4. Changes of fuel of consumptionfuel consumption for for syntheticsynthetic blending blending components components with regard with to regard Jet A-1. to Jet A-1.

Figure 5. Changes of thrust-specific fuel consumptions (TSFC) for synthetic blending components with regard to Jet A-1.

3.2. Exhaust Emissions Characteristics

Figure 6 provides results for oxygen (O2), carbon oxide (CO), carbon dioxide (CO2) and nitrogen oxides (NOx) whereas Figures 7–9 present relative changes of the emissions of O2, CO and CO2 for different feedstocks of synthetic-blending-component-fed engine as compared to the emissions for neat Jet A-1. The data for CO, CO2 and NOx were converted from the value of parameters measured in ppm or % to emission indices expressed in g/kg of fuel.

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Cf HEFA UCO HEFA CAM Energies 2020, 13, x FOR0 PEER REVIEW 7 of 12

-0.5 1 1 [%] - -1 -1.5 Cf HEFA UCO HEFA CAM -2 0

-2.5-0.5 1 1 [%] - -3 -1 -3.5-1.5 Change wrt Jet A -4 -2 -2.5 70000 88000 112000 -3 -3.5 Change wrt Jet A -4 Rotational speed [rpm] 70000 88000 112000

EnergiesFigure2020, 13 4,. 1277 Changes of fuel consumption for synthetic blending components with regard to Jet A-1. 7 of 12 Rotational speed [rpm]

Figure 4. Changes of fuel consumption for synthetic blending components with regard to Jet A-1.

Figure 5.5. ChangesChanges ofof thrust-specific thrust-specific fuel fuel consumptions consumptions (TSFC) (TSFC) for for synthetic synthetic blending blending components components with withregardFigure regard to Jet 5 .to A-1.Changes Jet A-1 .of thrust-specific fuel consumptions (TSFC) for synthetic blending components 3.2. Exhaustwith Emissionsregard to Jet Characteristics A-1. 3.2. Exhaust Emissions Characteristics 3.2.Figure Exhaust6 provides Emissions results Characteristics for oxygen (O 2), carbon oxide (CO), carbon dioxide (CO2) and nitrogen Figure 6 provides results for oxygen (O2), carbon oxide (CO), carbon dioxide (CO2) and nitrogen oxides (NOx)Figure whereas6 provides Figures results 7for–9 oxygenpresent (O relative2), carbon changes oxide (CO), of the carbon emissions dioxide of(CO O2)2 ,and CO nitrogen and CO 2 for oxides (NOx) whereas Figures 7–9 present relative changes of the emissions of O2, CO and CO2 for differentoxides feedstocks (NOx) whereas of synthetic-blending-component-fed Figures 7–9 present relative changes of engine the emissions as compared of O2, CO to theandemissions CO2 for for different feedstocks of synthetic-blending-component-fed engine as compared to the emissions for neatdifferent Jet A-1. feedstocks The data for of CO,synthetic CO2-blendingand NOx-componentwere converted-fed engine from as the compared value of to parameters the emissions measured for in neat Jet A-1. The data for CO, CO2 and NOx were converted from the value of parameters measured ppmn oreat %Jet to A emission-1. The data indices for CO, expressed CO2 and NO inx g were/kg of converted fuel. from the value of parameters measured in ppmin ppm or % or to % emissionto emission indices indices expressed expressed in g/kgg/kg of of fuel. fuel.

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Figure 6. Selected gas component emission as a function of rotational speed. (A)O2,(B) EI CO, (C) EI CO2,(D) EI NOx. Figure 6. Selected gas component emission as a function of rotational speed. (A) O2, (B) EI CO, (C) EI

CO2, (D) EI NOx.

Figure 7 demonstrates that the combustion in the engine for all the tested fuels was carried out with the same proportion of oxygen in the chamber (changes do not exceed 1%).

HEFA UCO HEFA CAM O2 [%]

0 1 1 [%]

- -0.2 -0.4 -0.6 -0.8 -1

-1.2 Change wrt Jet A 45000 70000 88000 112000

Rotational speed [rpm]

Figure 7. Changes of O2 emission for synthetic blending components with regard to Jet A-1.

Figure 8 shows that CO emissions for HEFA blends in relation to Jet A-1 for the analyzed engine operating conditions are lower (except for 112,000 rpm). Measurements of CO emissions at the highest rotational speed, due to a decrease in the value of CO emissions along with an increase in speed, are burdened with the greatest inaccuracy. The biggest difference between these fuels was approx. 9% in the case of the rotational speed of 70,000 rpm.

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Figure 6. Selected gas component emission as a function of rotational speed. (A) O2, (B) EI CO, (C) EI Energies 2020, 13, 1277 8 of 12 CO2, (D) EI NOx.

Figure 7 demonstrates that the combustion in the engine for all the tested fuels was carried out Figure7 demonstrates that the combustion in the engine for all the tested fuels was carried out with the same proportion of oxygen in the chamber (changes do not exceed 1%). with the same proportion of oxygen in the chamber (changes do not exceed 1%).

HEFA UCO HEFA CAM O2 [%]

0 1 1 [%]

- -0.2 -0.4 -0.6 -0.8 -1

-1.2 Change wrt Jet A 45000 70000 88000 112000

Rotational speed [rpm]

FigureFigure 7 7.. ChangesChanges of of O O22 emissionemission for for synthetic synthetic blending blending components components with with regard regard to to Jet Jet A A-1.-1.

FigureFigure 88 showsshows thatthat CO emissions forfor HEFAHEFA blendsblends inin relationrelation toto JetJet A-1A-1 forfor thethe analyzedanalyzed engineengine operatingoperating conditions conditions are are lower lower (except (except for for 112,000 112,000 rpm). rpm). Measurements Measurements of CO of emissions CO emissions at the highest at the highestrotational rotational speed, duespeed, to a due decrease to a decrease in the value in the of COvalue emissions of CO emissions along with along an increase with an in increase speed, arein burdened with the greatest inaccuracy. The biggest difference between these fuels was approx. 9% in speed,Energies 20are20 , burdened13, x FOR PEER with REVIEW the greatest inaccuracy. The biggest difference between these fuels9 wasof 12 approx.the case 9% of thein the rotational case of speedthe rotational of 70,000 speed rpm. of 70,000 rpm.

EI CO [g/kgfuel] HEFA UCO HEFA CAM 12

1 1 [%] 9 - 6 3 0 -3

Change wrt Jet A -6 -9 45000 70000 88000 112000

Rotational speed [rpm]

Figure 8. Changes of CO emission index for HEFA blends with regard to Jet A-1. Figure 8. Changes of CO emission index for HEFA blends with regard to Jet A-1.

The CO2 emission (Figure9) for both HEFA blends at all the analyzed states of engine operation The CO2 emission (Figure 9) for both HEFA blends at all the analyzed states of engine operation are lower in comparison with that of Jet A-1. The CO2 emission changes do not exceed 1.5%. Within the arerange lower of this in comparison parameter, therewith arethat no of significantJet A-1. The changes CO2 emission between changes tested fuels. do not exceed 1.5%. Within the range of this parameter, there are no significant changes between tested fuels.

EI CO2 [g/kgfuel] HEFA UCO HEFA CAM 0

1 1 [%] -0.2 - -0.4 -0.6 -0.8 -1 Change wrt Jet A -1.2 -1.4 45000 70000 88000 112000

Rotational speed [rpm]

Figure 9. Changes of CO2 emission index for HEFA blends with regard to Jet A-1.

The NOx emission (Figure 10) for both HEFA blends at all the analyzed states of engine operation are higher in comparison with Jet A-1. The biggest differences between tested fuels obtained at 45,000 rpm, approx. 22% for HEFA CAM and approx. 12% for HEFA UCO. As the speed increases, the differences between HEFA blends and Jet A-1 become smaller. The increase in NOx emissions can be explained by the fact that the HEFA blends are characterized by higher heat of combustion than Jet A-1. Whereas higher heat of combustion can translate into higher temperature in the combustion chamber.

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EI CO [g/kgfuel] HEFA UCO HEFA CAM 12

1 1 [%] 9 - 6 3 0 -3

Change wrt Jet A -6 -9 45000 70000 88000 112000

Rotational speed [rpm]

Figure 8. Changes of CO emission index for HEFA blends with regard to Jet A-1.

The CO2 emission (Figure 9) for both HEFA blends at all the analyzed states of engine operation are lower in comparison with that of Jet A-1. The CO2 emission changes do not exceed 1.5%. Within theEnergies range2020 of, 13 this, 1277 parameter, there are no significant changes between tested fuels. 9 of 12

EI CO2 [g/kgfuel] HEFA UCO HEFA CAM 0

1 1 [%] -0.2 - -0.4 -0.6 -0.8 -1 Change wrt Jet A -1.2 -1.4 45000 70000 88000 112000

Rotational speed [rpm]

Figure 9. Changes of CO2 emission index for HEFA blends with regard to Jet A-1. Figure 9. Changes of CO2 emission index for HEFA blends with regard to Jet A-1.

The NOx emission (Figure 10) for both HEFA blends at all the analyzed states of engine operation are higherThe NO inx comparisonemission (Figure with Jet 10) A-1. for both The biggest HEFA blendsdifferences at all between the analyzed tested fuels states obtained of engine at operation45,000 rpm, are approx. higher 22% in for comparison HEFA CAM with and Jet approx. A-1. The 12% forbiggest HEFA differences UCO. As the between speed increases,tested fuels the obtaineddifferences at between45,000 rpm HEFA, approx. blends 22% and for Jet HEFA A-1 become CAM and smaller. approx. The 12% increase for HEFA in NOx UCO. emissions As the canspeed be increases, the differences between HEFA blends and Jet A-1 become smaller. The increase in NOx Energiesexplained 2020 by, 13, the x FOR fact PEER that REVIEW the HEFA blends are characterized by higher heat of combustion than Jet10 of A-1. 12 emissionsWhereas higher can be heat explain of combustioned by the canfact translatethat the intoHEFA higher blends temperature are characterized in the combustion by higher chamber. heat of combustion than Jet A-1. Whereas higher heat of combustion can translate into higher temperature in the combustion chamber. EI NOx [g/kgfuel] HEFA UCO HEFA CAM

25 1 1 [%] - 20

15

10

5 Change wrt Jet A 0 45000 70000 88000 112000

Rotational speed [rpm]

Figure 10. Changes of NOx emission index for HEFA blends with regard to Jet A-1. Figure 10. Changes of NOx emission index for HEFA blends with regard to Jet A-1. 4. Conclusions 4. ConclusionsInvestigation of the performance and emissions characteristics for the miniature turbojet engine usingInvestigation a Jet A-1/HEFA of the blends performance were studied. and emissions The HEFA characteristics component for was the obtained miniature from turbojet two di enginefferent usingfeedstock: a Jet A camelina-1/HEFA blends and used were cooking studied oil.. The TheHEFA HEFA component fuels results was obtained were compared from two different with the feedstock:corresponding camelina values and forneat used Jet cooking A-1. The oil.tests The were HEFA carried fuels out according results were to aspecified compared methodology with the correspondingincluding authorial values profile for ofneat engine Jet A tests.-1. The The tests presented were work carried contains out according new studies, to whicha specified are a methodologycontinuation ofincluding the authors’ authorial research pro areafile of related engine to tests. alternative The presented fuels. work contains new studies, whichThe are main a continuation results can of be the summarized authors' research as follows: area related to alternative fuels. The main results can be summarized as follows: The analysis of experimental data indicates differences in the operation of the miniature jet engine •  Theif it runs analysis on neat of experimental Jet A-1 or on data HEFA indicates blends, differenceswhich shows in especially the operation in fuel of consumption the miniature and jet engineCO emission. if it runs Fuel on consumption neat Jet A- and1 or CO on emission HEFA blends, for HEFA which blends shows are lower especially than inJet fuel A-1. consumptionHEFA blends and have CO a higher emission. calorific Fuel valueconsumption and lower and density CO emission compared for HEFA to neat blends jet fuel. are lower than Jet A-1. HEFA blends have a higher calorific value and lower density compared to neat jet fuel.  No significant variations in the turbine temperature and CO2 emissions on all engine operating states for tested fuels.  Significant differences for tested fuels are obtained for NOx emissions. HEFA component, for both camelina and used cooking oil, added to aviation fuel increases NOx emissions.

Author Contributions: Conceptualization, B.G. and T.B.; methodology, B.G and T.B.; investigation, B.G.; data curation, B.G and T.B.; writing—original draft preparation, B.G. and T.B.; writing—review and editing, A.J. and T.S.; visualization, T.B.; supervision, A.J.; resources, B.G., T.B. and T.S.

Funding: This research was funded by the Ministry of Science and Higher for the project financed within the framework of the statutory activity (decision no 4111/E-282/S/2017).

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

Abbreviations

Symbol Definition Units CO2 carbon dioxide % K thrust N Cf fuel consumption g/s T4 turbine temperature oC TSFC thrust-specific fuel consumptions kg/Nh O2 oxigen % EI CO emission index of carbon monoxide g/kgfuel EI CO2 emission index of carbon dioxide g/kgfuel EI NOx emission index of nitrogen oxides g/kgfuel

Energies 2020, 13, 1277 10 of 12

No significant variations in the turbine temperature and CO emissions on all engine operating • 2 states for tested fuels.

Significant differences for tested fuels are obtained for NOx emissions. HEFA component, for both • camelina and used cooking oil, added to aviation fuel increases NOx emissions.

Author Contributions: Conceptualization, B.G. and T.B.; methodology, B.G. and T.B.; investigation, B.G.; data curation, B.G. and T.B.; writing—original draft preparation, B.G. and T.B.; writing—review and editing, A.J. and T.S.; visualization, T.B.; supervision, A.J.; resources, B.G., T.B. and T.S. All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by the Ministry of Science and Higher Education for the project financed within the framework of the statutory activity (decision no 4111/E-282/S/2017). Conflicts of Interest: The authors declare no conflict of interest.

Abbreviations

Symbol Definition Units CO2 carbon dioxide % K thrust N Cf fuel consumption g/s T4 turbine temperature ◦C TSFC thrust-specific fuel consumptions kg/Nh O2 oxigen % EI CO emission index of carbon monoxide g/kgfuel EI CO2 emission index of carbon dioxide g/kgfuel EI NOx emission index of nitrogen oxides g/kgfuel

References

1. Intergovernmental Panel on Climate Change (IPPC), Fourth Assessment Report, “Climate Change 2007: Mitigation of Climate Change”. Available online: https://archive.ipcc.ch/publications_and_data/publications_ ipcc_fourth_assessment_report_wg3_report_mitigation_of_climate_change.htm (accessed on 12 November 2019). 2. Lee, D.; Fahey, D.W.; Forster, P.M.; Newton, P.J.; Wit, R.C.N.; Lim, L.L.; Owen, B.; Sausen, R. Aviation and global climate change in the 21st century. Atmos. Environ. 2009, 43, 3520–3537. [CrossRef] 3. Fact Sheet. Climate Change & CORSIA. IATA. 2018. Available online: https://www.iata.org/en/iata- repository/pressroom/fact-sheets/fact-sheet---climate-change/ (accessed on 2 December 2019). 4. ASTM D7566. Standard Specification for Aviation Turbine Fuel Containing Synthesized Hydrocarbons; ASTM International: West Conshohocken, PA, USA, 2019. 5. Gutiérrez-Antonio, C.; Gómez-Castro, F.I.; de Lira-Flores, J.A.; Hernández, S. A review on the production processes of renewable jet fuel. Renew. Sustain. Rev. 2017, 79, 709–729. [CrossRef] 6. Rahmes, T.F.; Kinder, J.D.; Henry, T.M.; Crenfeldt, G.; Leduc, G.F.; Zombanakis, G.P.; Abe, Y.; Lambert, D.M.; Lewis, C.; Juenger, J.A.; et al. Sustainable Bio-derived Synthetic Paraffinic (Bio-SPK) Jet Fuel Flight and Engine Tests Program Results. In Proceedings of the 9th AIAA Aviation Technology, Integration and Operations Conference, Hilton Head, SC, USA, 21–23 September 2009. [CrossRef] 7. ASTM D1655. Standard Specification for Aviation Turbine Fuels; ASTM International: West Conshohocken, PA, USA, 2019. 8. Bolszo, C.D.; McDonell, V.G. Emissions optimization of a fired . Proc. Combust. Inst. 2009, 32, 2949–2956. [CrossRef] 9. Chen, L.; Zhang, Z.; Lu, Y.; Zhang, C.; Zhang, X.; Zhang, C.; Roskilly, A.P. Experimental study of the gaseous and particulate matter emissions from a gas turbine burning butyl butyrate and ethanol blends. Appl. Energy 2017, 195, 693–701. [CrossRef] 10. Chong, C.T.; Hochgreb, S. Spray flame structure of rapeseed biodiesel and Jet A-1 fuel. Fuel 2014, 115, 551–558. [CrossRef] Energies 2020, 13, 1277 11 of 12

11. Chuck, C.J.; Donnelly, J. The compatibility of potential bioderived fuels with Jet A-1 aviation kerosene. Appl. Energy 2014, 118, 83–91. [CrossRef] 12. Dzi˛egielewski,W.; Gawron, B.; Kulczycki, A. Low Temperature Properties of Fuel Blends of Kerosene and Fame Type Used to Supply Turbine Engines in Marine and Other Non-Aeronautical Applications. Pol. Marit. Res. 2015, 22, 101–105. 13. Gawron, B.; Białecki, T.; Dzi˛egielewski,W.; Ka´zmierczak, U. Performance and emission characteristic of miniature turbojet engine fed Jet A–1/alcohol blend. J. Kones 2016, 23, 123–129. [CrossRef] 14. Badami, M.; Nuccio, P.; Pastrone, D.; Signoretto, A. Performance of a small-scale turbojet engine fed with traditional and alternative fuels. Energy Convers. Manag. 2014, 82, 219–228. [CrossRef] 15. Hui, X.; Kumar, K.; Sung, C.J.; Edwards, T.; Gardner, D. Experimental studies on the combustion characteristics of alternative jet fuels. Fuel 2012, 98, 176–182. [CrossRef] 16. Gaspar, R.M.P.; Sousa, M.M. Impact of alternative fuels on the operational and environmental performance of a small turbofan engine. Energy Convers. Manag. 2016, 130, 81–90. [CrossRef] 17. Won, S.H.; Veloo, P.S.; Dooley, S.; Santner, J.; Haas, F.M.; Ju, Y.; Dryer, F.L. Predicting the global combustion behaviors of petroleum-derived and alternative jet fuels by simple fuel property measurements. Fuel 2016, 168, 34–46. [CrossRef] 18. Xue, X.; Hui, X.; Singh, P.; Sung, C.J. Soot formation in non-premixed counterflow flames of conventional and alternative jet fuels. Fuel 2017, 210, 343–351. [CrossRef] 19. Allen, C.; Valco, D.; Toulson, E.; Edwards, T.; Lee, T. Ignition behavior and surrogate modeling of JP-8 and of camelina and tallow hydrotreated renewable jet fuels at low temperatures. Combust. Flame 2013, 160, 232–239. [CrossRef] 20. Buffi, M.; Valera-Medina, A.; Marsh, R.; Pugh, D.; Giles, A.; Runyon, J.; Chiaramonti, D. Emissions characterization tests for hydrotreated renewable jet fuel from used cooking oil and its blends. Appl. Energy 2017, 201, 84–93. [CrossRef] 21. Gawron, B.; Białecki, T. Impact of a Jet A-1/HEFA blend on the performance and emission characteristics of a miniature turbojet engine. Int. J. Environ. Sci. Technol. 2018, 15, 1501–1508. [CrossRef] 22. Hashimoto, N.; Nishida, H.; Ozawa, Y. Fundamental combustion characteristics of Jatropha oil as for gas turbines. Fuel 2014, 126, 194–201. [CrossRef] 23. Liu, Y.C.; Savas, A.J.; Avedisian, C.T. The spherically symmetric droplet burning characteristics of Jet-A and biofuels derived from camelina and tallow. Fuel 2013, 108, 824–832. [CrossRef] 24. Shila, J.J.; Johnson, M.E. Estimation and comparison of particle number emission factors for petroleum-based and camelina blends used in a TFE-109 Turbofan Engine. In Proceedings of the 54th AIAA Sciences Meeting, San Diego, CA, USA, 4–8 January 2016. 25. Zhang, C.; Hui, X.; Lin, Y.; Sung, C.J. Recent development in studies of alternative jet fuel combustion: Progress, challenges, and opportunities. Renew. Sustain. Energy Rev. 2016, 54, 120–138. [CrossRef] 26. Yang, J.; Xin, Z.; He, Q.; Corscadden, K.; Niu, H. An overview on performance characteristics of bio-jet fuels. Fuel 2019, 237, 916–936. [CrossRef] 27. Gawron, B.; Białecki, T. The laboratory test rig with miniature jet engine to research aviation fuels combustion process. J. Konbin 2015, 36, 79–90. [CrossRef] 28. Gawron, B.; Białecki, T. Measurement of exhaust gas emissions from miniature turbojet engine. Combust. Engines 2016, 167, 58–63. 29. SAE Aerospace Recommended Practice 1256. Procedure for the Continuous Sampling and Measurement of Gaseous Emissions from Aircraft Turbine Engines; SAE International: Warrendale, PA, USA, 2011. 30. Gawron, B.; Białecki, T.; Górniak, A.; Janicka, A.; Zawi´slak,M. An innovative method for exhaust gases toxicity evaluation in the miniature turbojet engine. Aircr. Eng. Aerosp. Technol. 2017, 89, 757–763. [CrossRef] Energies 2020, 13, 1277 12 of 12

31. Gawron, B.; Białecki, T.; Janicka, A.; Górniak, A.; Zawi´slak,M. Exhaust toxicity evaluation in a gas turbine engine fueled by aviation fuel containing synthesized hydrocarbons. Aircr. Eng. Aerosp. Technol. 2020, 92, 60–66. [CrossRef] 32. Janicka, A.; Zawi´slak,M.; Zaczy´nska,E.; Czarny, A.; Górniak, A.; Gawron, B.; Białecki, T. Exhausts toxicity investigation of turbojet engine, fed with conventional and biofuel, performed with aid of BAT-CELL method. Toxicol. Lett. 2017, 280, 202. [CrossRef]

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