喜歡就充值下載吧。。資源目錄里展示的文件全都有，，請放心下載，，有疑問咨詢QQ:1064457796或者1304139763 ==================== 喜歡就充值下載吧。。資源目錄里展示的文件全都有，，請放心下載，，有疑問咨詢QQ:1064457796或者1304139763 ==================== Open Access Journal Journal of Power Technologies 92(1)(2012)5567journal homepage:papers.itc.pw.edu.plEffect of hydrogen-diesel quantity variation on brake thermal efficiency of adual fuelled diesel engineBiplab K.Debnath,Ujjwal K.Saha,Niranjan SahooDepartment of Mechanical Engineering,Indian Institute of Technology GuwahatiGuwahati-781039,Assam,IndiaAbstractThe twenty first century could well see the rise of hydrogen as a gaseous fuel,due to it being bothenvironment friendly and having a huge energy potential.In this paper,experiments are performedin a compression ignition diesel engine with dual fuel mode.Diesel and hydrogen are used as pilotliquid and primary gaseous fuel,respectively.The objective of this study is to find out the specificcomposition of diesel and hydrogen for maximum brake thermal efficiency at five different loadingconditions(20%,40%,60%,80%and 100%of full load)individually on the basis of maximum dieselsubstitution rate.At the same time,the effects on brake specific fuel consumption,brake specificenergy consumption,volumetric efficiency and exhaust gas temperature are also observed at variousliquid gaseous fuel compositions for all the five loadings.Furthermore,second law analysis is carriedout to optimize the dual fuel engine run.It is seen that a diesel engine can be run efficiently inhydrogen-diesel dual fuel mode if the diesel to hydrogen ratio is kept at 40:60.Keywords:Diesel Engine,Diesel Replacement Ratio,Hydrogen,Dual Fuel,Efficiency,Second Law1.IntroductionThe use of conventional fossil fuels has reacheda perceived crisis point.A number of reasons areresponsible for this,such as finite reserves of whatare non-renewable energy sources and the damagefossil fuels cause to the environment 1.There-fore,researchers around the world are exploringevery option to find suitable alternatives to re-place fossil fuels,whether partially or fully 2.Some of the alternative fuels that have been usedto replace petroleum-based fuels include vegetableCorresponding authorEmail addresses:d.biplabiitg.ernet.in(BiplabK.Debnath),sahaiiitg.ernet.in(Ujjwal K.Saha),shockiitg.ernet.in(Niranjan Sahoo)oils,alcohols,liquefied petroleum gas(LPG),liq-uefied natural gas(LNG),compressed natural gas(CNG),bio gas,producer gas,hydrogen etc.Inthis context,hydrogen(H2),a non-carboniferousand non-toxic gaseous fuel,has attracted greatinterest and has huge potential.H2is only oneof many possible alternative fuels that can be de-rived from various natural resources.Others in-clude:coal,oil shale and uranium or renewableresources based on solar energy.H2can be com-mercially formed from electrolysis of water andby coal gasification;thermo-chemical decompo-sition of water and solar photo-electrolysis,al-though these are still in the developmental stageat present 3.The energy required to ignite H2is very low and thus its usage in spark ignitionJournal of Power Technologies 92(1)(2012)5567(SI)engines is not suitable.Again,in compres-sion ignition(CI)engines,H2will not auto ignitedue to its high auto ignition temperature(858 K).Therefore the dual fuel mode appears the bestway to utilize H2in internal combustion(IC)en-gines 4.The dual fuel environment can be cre-ated by initially using a small amount of diesel(as pilot fuel)to launch the combustion and thensupplying H2(as primary fuel)to deliver the restamount of energy to run the cycle.Regardingpower output,hydrogen enhances the mixturesenergy density at lean conditions during a dualfuel run by increasing the hydrogen-to-carbon ra-tio,and thereby improves torque at the wide openthrottle condition 5.H2can be supplied in theengine by carburation,manifold or port injectionor by cylinder injection 6,7.However,the injec-tion of H2in the intake manifold or port requires aminor modification in the engine and offers a bet-ter power output than carburetion 810.Theexperimental works of Yi et al.11 establishedthat intake port injection delivers higher efficiencythan in-cylinder injection at different equivalenceratios too.Varde and Frame figured out that the brakethermal efficiency(bth)of H2diesel dual fuel modeis primarily dependent upon the amount of H2added.The larger the amount of H2,the higherthe value of bthis 3,12.It has been seen in H2diesel dual fuel mode that 90%enriched H2giveshigher efficiency than 30%at 70%load,but can-not complete the load range beyond that due toknocking problems 3.However,bthwas foundto drop when the amount of H2is less than orequal to 5%.In their analysis,an extremely leanair H2mixture restricts the flame to propagatefaster,which lowers H2combustion efficiency 12.However,experimental works done later,with H2diesel dual fuel mode,do not prove this drop inbthwith H2addition as mentioned above 13.According to Shudo et al.hydrogen combus-tion causes higher cooling loss to the combustionchamber wall than hydrocarbon combustion,be-cause of its higher burning velocity and shorterquenching distance 14.A study performed byWang and Zhang indicates that the introductionof hydrogen into the diesel engine causes the en-ergy release rate to increase at the early stagesof combustion,which increases the indicated effi-ciency 15.This is also the reason for the low-ered exhaust temperature.According to them,for fixed H2supply at 50%,75%and 100%load,H2replaces 13.4%,10.1%and 8.4%energy respec-tively with high diffusive speed and high energyrelease rate.The practice of normal and heavy exhaust gasrecirculation(EGR)in H2diesel dual fuel modeis found to lower power production and fuel con-sumption 16.Increases in compression ratio(CR)for H2fuelled diesel engine improves power,efficiency,peak pressure,peak heat release rateand emission of oxides of carbon,but increasesNOxemission 17.A study of injection timingvariation shown that advancing injection timingalthough provides favorable emission reduction,but makes engine operation more inefficient andunstable 18.Sahoo et al.performed an experi-mental study on syngas diesel dual fuel mode forH2:CO ratio of 100:0 at 20%,40%,60%,80%and100%of full load at maximum possible supply ofhydrogen until knocking 19.The study revealsthat at 80%load,the engine offers a maximum19.75%brake thermal efficiency at a maximum72.3%diesel replacement ratio.A few researchers4,20 have studied the variation of H2-dieselquantity for constant diesel supply at each loadto improve the brake power(BP).The increasein the supply of H2in inlet manifold causes a re-duction in the air flow to the engine.As a result,the volumetric efficiency(vol)and consequentlythe bthof the engine reduces.Therefore,thereis scope to study and understand engine perfor-mance by varying both H2and diesel supply whilemaintaining constant BP at each load condition.In light of this fact,the objective of the presentstudy is to determine the best composition of H2-diesel for maximum bthby varying the quantity offuel(pilot and primary)and maintaining constantspeed and BP at each of the five load conditionscorrespondingly.Some of the important physicaland thermodynamic properties of diesel and H2are shown in Table 1.The load conditions selectedare 20%,40%,60%,80%and 100%of full load.As reported by Sahoo et al.19,the maximum 56 Journal of Power Technologies 92(1)(2012)5567Table 1:Properties of H2and diesel 19PropertiesDieselHydrogenChemical compositionC12H26H2Density?kgm3?8500.085Calorific value?MJkg?42119.81Cetane number4555Auto-ignition temperature(K)553858Stoichiometric air fuel ratio14.9234.3Energy density?MJNm3?2.822.87diesel replacement ratios during a dual fuel runare considered as 26%,42%,58%,72%and 44%atthe aforementioned loads respectively.Other per-formance parameters studied alongside are brakespecific fuel consumption(BSFC),brake specificenergy consumption(BSEC),voland exhaust gastemperature(EGT).In order to endorse the ex-perimental results and analysis,the Second Lawanalysis is performed to provide histograms of cal-culated availability of fuel,cooling water,exhaustgas,availability destruction and exergy efficiency.In this way,the present experimental and analyt-ical studies will establish the optimized quantityof H2-diesel composition for best efficiency at con-stant power at each load.2.Experimental setupThe experiments are carried out in a KirloskarTV1 CI diesel engine installed at the Centrefor Energy of the Indian Institute of Technol-ogy(IIT),Guwahati,India.Figure 1 shows aschematic diagram of the engine test bed.Theoriginal engine specifications are shown in Table 2.The engine loading is performed by an eddy cur-rent type dynamometer.The liquid fuel is sup-plied to the engine from the fuel tank through afuel pump and injector.The fuel injection sys-tem of the engine consists of an injection nozzlewith three holes of 0.3 mm diameter with a 120spray angle.A U-tube type manometer is used toquantity the head difference of air flow to the en-gine,while allowing the intake air to pass throughan orifice meter.The engine block and cylinderhead are surrounded by a cooling jacket throughwhich water flows to cool the engine.To mea-sure the specific heat of exhaust gas,a calorime-ter of counter flow pipe-in pipe heat exchanger isalso provided.Temperature measurement is per-formed by K-type thermocouples,which are fittedat relevant positions 21.In order to convert the diesel engine test bedinto dual fuel mode,some additional equipmentis installed in the setup.These include:hydro-gen gas cylinder with regulator,coriolis mass flowmeter,flame trap with fine tuning regulator,nonreturn valve(NRV)and gas carburetor.The cori-olis mass flow meter measures the mass flow rateof hydrogen;while the flame trap and the NRV areused to prevent fire hazards due to accidental en-gine backfire.In the dual fuel mode H2is suppliedto the engine by the induction method.In thismethod,H2mixes with the intake air in the inletmanifold outside the cylinder.A gas carburetor16 is fixed in the intake manifold of the engineto provide the H2supply.The liquid fuel supplyis controlled through a fuel cut offvalve for vari-ous diesel fuel replacement ratios by a lever-armarrangement,as shown in Fig.2.3.Experimental procedureTable 3 illustrates the designed experimental ma-trix of the H2-diesel test at different loads.Ini-tially,the engine is allowed to run on diesel atno load condition for a few minutes to attaina steady state.The cooling water supplies forthe engine and calorimeter are set to 270 and 57 Journal of Power Technologies 92(1)(2012)5567Table 2:Diesel engine specification 21ParameterSpecificationEngine typeKirloskar TV1General detailsSingle cylinder,four stroke diesel,water cooled,compression ignitionBore and stroke87.5110 mmCompression ratio17.5:1Rated output5.2 kW(7 BHP)1500 rpmAir boxWith orifice meter and manometerDynamometerEddy current loading unit,016 kgFuel injection opening205 bar 23BTDC staticCalorimeter typePipe in pipe arrangementRotameterFor water flow measurementTable 3:The experimental matrixLoadDiesel replacement ratioEngine operation20%10,20,26Speed:40%10,20,30,40,42150050 RPM60%10,20,30,40,50,58Injection timing:80%10,20,30,40,50,60,70,7223BTDC100%10,20,30,40,44Figure 1:Schematic diagram of the setup80 liters per hour,as per the engine provider in-structions.Thereafter,the load is gradually in-creased to 3.2 kg(20%load)and the engine is al-lowed to run until it reaches a steady state.Then,the inlet and outlet temperatures of engine cool-ing water,calorimeter cooling water and exhaustgas are measured.Water head difference,dieselFigure 2:Adjustable lever arm arrangementflow rate and engine speed are also recorded.Theadjustable lever arm is then rotated to press thefuel cut offvalve,which will reduce the fuel supplyand speed.The lever arm is then fixed at a point wherediesel supply is reduced by 10%.At this pointH2(99.99%purity)is allowed to flow from thehigh pressure cylinder to the flame trap,throughthe coriolis mass flow meter.At the outlet of theflame trap,one fine tuning regulator is connectedto control H2flow accurately and is delivered tothe intake manifold through the NRV and gas car-58 Journal of Power Technologies 92(1)(2012)5567buretor.The added supply of chemical energy inthe form of H2in the cylinder is converted into me-chanical energy after combustion.This increasesthe speed and BP of the engine.The quantity ofH2is adjusted precisely to return the engine speedand BP to its previous value,recorded during thepure diesel run.The pressure of the H2outlet isnot allowed to exceed 1.2 bar.After the enginereaches a steady state,the values of temperatures,water manometer head and mass flow of H2fromcoriolis flow meter are recorded.The H2supply isthen stopped and the adjustable lever depressedfurther to reduce the diesel fuel supply by 20%.At this point,H2supply is initiated and the pro-cedure is repeated.Once the data of all the fuel replacement ratiosare recorded,the engine is restored to its dieselmode.The load is increased by the eddy currentdynamometer,and the measurement procedurefor all the diesel replacement ratios are repeatedat that load.The maximum fuel replacement ra-tios(shown in Table 3)for five loading conditions(20%,40%,60%,80%and 100%of full load)aretaken from the work reported by Sahoo et al.19.Finally,the H2supply is stopped completely,andthe engine is allowed to run at“no load condition”prior to complete shutdown.4.Analysis procedureAfter collecting the data sets at each diesel re-placement ratio and for each load,the dependentparameters are calculated according to the follow-ing equations 22,23.The diesel replacement ratio(Z)is given byZ=md mpd md 100%(1)The brake power can be written asBP=2 3.142 N W r60000(2)The brake thermal efficiency for diesel mode ismeasured as(bth)diesel=BP md LHVd 100%(3)The brake thermal efficiency for dual fuel modeis given by(bth)dual=BP mpd LHVpd+mh LHVh 100%(4)The brake specific fuel consumption for dualfuel mode is computed fromBSFC=mpd+mhBP!3600(5)The brake specific energy consumption for dualfuel mode is given byBSEC=mpd LHVpd+mh LHVhBP(6)The volumetric efficiency can be computedfromvol=ma?kgs?3600?3.1424?D2 L Nn 60 K a 100%(7)5.Thermodynamic analysisThe results of the hydrogen-diesel dual-fuel ex-periment are analyzed using the Law of Ther-modynamics.It provides significant informationregarding the appropriate distribution of energysupplied by fuel in different parts of the engine24.Also,the energy that is utilized or destroyedis quantified through availability analysis.Thisanalysis,finally,gives the exact amount of hy-drogen and diesel composition which should bemaintained to extract the maximum amount ofenergy from the fuel energy supplied.Hence,the“First Law(Energy)”along with the“Second Law(Exergy)”study of the engine is described in thefollowing section with correct equations.5.1.Energy analysisAccording to the First Law of thermodynamics,the energy supplied in a system is conserved inits different processes and components 25.In aCI engine,the fuel energy supplied(Qi)is trans-ferred in its different processes,viz.Shaft power(Ps),Energy in cooling water(Qc),Energy in ex-haust gas(Qe)and Uncounted energy losses(Qu)59 Journal of Power Technologies 92(1)(2012)5567in the form of friction,radiation,heat transfer tothe surroundings,operating auxiliary equipments,etc.These different forms of energies are calcu-lated according to the following analytical expres-sions 26.The fuel energy supplied,i.e.,the energy inputcan be calculated as follows:(Qi)diesel=md3600 LHVd(8)(Qi)dual=mpd3600 LHVpd+mh3600 LHVh(9)The energy transferred into the shaft can bemeasured asPs=Brake power of the engine(10)The energy transferred into cooling water canbe computed asQC=mpd3600!Cpw(Two Twi)(11)The energy flow through exhaust gas can beestimated asQe=?me3600?Cpe(Tei Teo)(12)For a more precise thermodynamic analysis,thespecific heat of exhaust gas is calculated from theenergy balance of the exhaust gas calorimeter.Fi-nally,from the energy balance,the uncounted en-ergy losses can be estimated asQu=Qi(Ps+Qc+Qe)(13)5.2.Exergy analysisThe availability can be described as the abil-ity of the supplied energy to perform a usefulamount of work 27.In the CI engine the chem-ical availability of fuel(Ai)supplied is convertedinto different types of exergy,viz.,Shaft availabil-ity(As),Cooling water availability(Ac),Exhaustgas availability(Ae)and Destructed availability(Ad)in the form of friction,radiation,heat trans-fer to the surroundings,operating auxiliary equip-ments,etc.These forms of energies are calculatedaccording to the following analytical expressionsas described in the literature 2830.The chemical availability of the fuel supplied isgiven by(Ai)diesel=1.0338 md3600 LHVd(14)(Ai)dual=1.0338 mpd3600 LHVpd(15)+0.985 mh3600 LHVhThe availability transferred through the shaftis recorded asAs=Brake power of the engine(16)The cooling water availability can be measuredasAC=QC?mw3600?Cpw ln TwoTwi!(17)Exhaust gas availability can be calculated asAe=Qe+?mw3600?(18)To(Cpw ln ToTei!Re ln PoPe!)The exhaust gas constant(Re)is estimatedfrom the energy balance of the exhaust gascalorimeter and the products of complete com-bustion of the diesel fuel.The uncounted availability destruction is deter-mined from the availability balance asAd=Ai(As+Ace+Ae)(19)Therefore,the exergy efficiency(II)can be es-timated asII=1 DestructedavailabilityFuelavailability=1 AdAi(20)6.Results and discussionThe results and discussion part of this H2-dieseldual fuel experiment work is divided into two sec-tions;viz.,performance analysis and Second Lawanalysis.The performance analysis discusses bth 60 Journal of Power Technologies 92(1)(2012)5567 05101520251020304050607080Diesel Replacement(%)20%Load40%Load60%Load80%Load100%LoadFigure 3:Variation of brake thermal efficiency with dieselreplacement 0.20.40.60.81.01.21.41020304050607080Diesel Replacement(%)20%Load40%Load60%Load80%Load100%LoadFigure 4:Variation of brake specific fuel consumption withdiesel replacement,BSFC,BSEC,vol,EGT and a comparison ofmaximum brake thermal efficiencies for diesel anddual fuel modes.Later on,the Second Law anal-ysis shows the availabilities of fuel,cooling waterand exhaust gas,destroyed availability and exergyefficiency.6.1.Performance analysisThe effect of variation of H2-diesel quantity onbthfor the five loading conditions is shown inFig 3.Except for the 20%load,all other load-ing conditions show that an increase in H2quan-tity increases bth,but only up to a certain limit.This indicates that in the lower load region,H2cannot burn properly with diesel and results inpoor combustion efficiency.However,this con-dition improves with the increase in load.Themaximum value of bthobtained is around 20%at 0.640.660.680.700.721020304050607080Diesel Replacement(%)20%Load40%Load60%Load80%Load100%LoadFigure 5:Variation of volumetric efficiency with diesel re-placement 481216201020304050607080Diesel Replacement(%)20%Load40%Load60%Load80%Load100%LoadFigure 6:Variation of brake specific energy consumptionwith diesel replacement80%load condition for both 50%and 60%dieselreplacement ratio.Along with the increase in thebththere is also a reduction in BSFC encounteredwith the increase in load and H2substitution rate(except for the 20%load)which is exemplifiedin Fig.4.This is because with the increase inH2,the quantity of energy supply rate into thecylinder increases.Therefore,the total amountof fuel needed for the same BP is alleviated asfar as energy supply is concerned.However,af-ter a certain point of H2replacement,the enginemay not run more efficiently,resulting in a reduc-tion in bth.This is because of the large reductionin volumetric efficiency caused by a reduction ofair(or more precisely oxygen)accessibility insidethe cylinder.This can be clearly understood fromFig.5.The reduction in BSEC with the increase 61 Journal of Power Technologies 92(1)(2012)5567 1002003004005006007008009001020304050607080Diesel Replacement(%)20%Load40%Load60%Load80%Load100%LoadFigure 7:Variation of exhaust temperature with dieselreplacement 051015202520406080100Eng