THERMODYNAMIC ANALYSIS OF DIESEL ENGINE USING PRODUCER GAS AS SECONDARY FUEL

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1 HEFAT th Iteratioal Coferece o Heat Trasfer, Fluid Mechaics ad Thermodyamics July 2014 Orlado, Florida THERMODYNAMIC ANALYSIS OF DIESEL ENGINE USING PRODUCER GAS AS SECONDARY FUEL Vivek Kumar Gaba*, AimeshDewaga, ShubhakarBhowmick (*Correspodig author) Departmet of Mechaical Egieerig, Natioal Istitute of Techology Raipur Raipur(CG),492010, Idia, vgaba.mech@itrr.ac.i ABSTRACT The proposed work reports a combustio model for a dual fuel CI egie for Diesel cycle ad Dual cycle. The work the aalytically eamies the performace of a CI egie with the miimum use of diesel as primary fuel, with producer gas as secodary fuel. The performace has bee aalysed for work output ad thermal efficiecy. The combustio model has bee developed for ideal diesel egie, diesel-producer gas egie with diesel as primary fuel. The combustio models have bee simulated usig MATLAB codes. The specificatios of a stadard CI egie have bee used for umerical calculatios. The equatio of state i each process i the cycles has bee critically aalysed based o laws of thermodyamics. The performace aalysis shows that, i a diesel-producer gas egie, thermal efficiecy icreases ad work doe decreases as the percetage of diesel supplied durig combustio process decreases. Also, the additio of producer gas i a dual-fuel (Diesel-Producer gas) egie allows the egie to ru over a lower rage of maimum temperature of the cycle which reduces the chaces of No formatio. NOMENCLATURE D L m air m f P R T U V y δq du δw [m] [m] [mole] [mole] [N/m 2 ] [J/g-mol-K] [K] [m 3 ] [-] [-] Bore diameter of cylider Stroke legth Mass of air Mass of fuel Pressure Uiversal gas costat Temperature Absolute Iteral Eergy Volume Fractio of diesel coverted i each divisio Fractio of diesel bured i costat volume cycle Heat trasfer Chage i Iteral Eergy Work trasfer Special characters st [-] act [-] [-] Subscripts -1 fd fp INTRODUCTION Stoichiometric air-fuel ratio Actual air-fuel ratio Equivalece ratio After th divisio Before th divisio For Diesel fuel For Producer gas Compressio igitio (CI) egies are importat compoets of the trasportatio ad eergy sectors of the world. O daily basis millios of uits are used due to which the emissio of CI egies is a importat coceruder pollutio cotrol. I case of CI egies, it is madatoryto characterize ad model each of the processes relevat to the fuel ijectio ad combustio iside the combustio chamber. Although CI egies are desiged to operate o less refied distillate tha gasolie, yet these egies are more efficiet at covertig fuel eergy cotet ito work output compared to spark igitio egie. CI egies also have fewer overall emissios tha spark igitio egies. Depletig fuel reserves ad icreasig emissio levels have forced researchers to look for alterative/reewable eergy sources. The preset work proposes the combustio characteristics of oe such combiatio of alterative fuel i form of diesel ad producer gas. Modellig of miture formatio ad combustio processes of the proposed fuel miture is a very useful tool to aalyse ad predict the performace of reciprocatig iteral combustio egies. I [1], costat eddy diffusivity ad a oe-step chemical reactio has bee developed to study the flame propagatio i a Spark Igitio (SI) egie at 1600 ad 4200 rpm uder rich fuel 694

2 coditios usig oe ad two zoe thermodyamic models. The thermodyamic models have bee compared with 1-D model for average miture temperature, the temperatures of the bured ad ubured gases ad the flame surface area ad idicate that the oe-dimesioal model predictios are very sesitive to the eddy diffusivity ad reactio rate data whereas the two-zoe thermodyamic model predicts, first, a mootoically icreasig flame surface area with time ad, the, a mootoically decreasig surface area.fuel evolutio is modelled by studyig the spray atomizatio, peetratio, air etraimet, ad evaporatio; the air motio; ad the igitio delay accordig to [2]. The model cosists of aalytical ad semi-empirical sub models for all the above metioed pheomea.typical emphasis is laid o spray behaviour durig the atomizatio process as well as after the impigemet agaist the walls. I [3], the problems associated with the coversio of a direct-ijectio diesel egie to dual-fuel operatio have bee addressed. The effects of chages i differet operatig parameters such as ilet temperature ad pilot liquid fuel quatity ad quality o kock-free performace limit are studied, usig propae, methae ad hydroge ad their bleds. The importace of volumetric efficiecy i form of a measure of the effectiveess of a air pumpig system is reported i [4]. The results from multidimesioal umerical simulatios are reported i [5] i a effort to optimize the performace of a fuel-lea-bur, homogeeous charge, atural gas spark-igitio iteral combustio (IC) egie. The desig ad operatioal variables of ilet - ehaust system are observed i [6] to be decisive i determiig overall egie performace. I [7], developmet of a complete cycle model has bee attempted by preparig a source code for determiig complete cycle performace characteristics, ad ehaust emissios of diesel egies. A emissio model based o the chemical equilibrium ad kietics of NO has also bee proposed to calculate the pollutat cocetratios withi each zoe ad the whole of the cylider. I [8] i-cylider pressure, beig a importat parameter i study of the ICE combustio, has bee ivestigated by itroducig heat release fuctio ad a empirical coversio of efficiecy factor ito the model. For the oidatio of represetative surrogate compoets of a typical multi-compoet automotive fuel,use of reduced chemical kietic mechaisms have bee reported i [9] where i the results show that the multi-compoet combustio model yields reliable performace for combustio predictios, as well as computatioal efficiecy improvemets. The performace aalysis carried out i [10] observes that i a diesel-producer gas CI egie, thermal efficiecy icreases with icrease i the percetage of diesel supplied durig costat volume process with isigificat effect o work output. The isigificace of the quatity of producer gas burt durig costat volume process o thermal efficiecy for fied quatity of diesel is also reported.i aother work [11], the combustio of Rapeseed Methyl Ester (RME), has bee reported usig a chemical model prepared by supplemetig the eistig detailed mechaism of methyl butaoate (MB) ester oidatio by sub-mechaisms for C 7 H 16 ad C 7 H 8 O to represet combustio of RME, C 19 H 34 O 2 or C 19 H 36 O 2. ANALYSIS METHODOLOGY The preset work deals with simulatio of diesel egie workig o dual fuel usig MATLAB codes. Simulatio has bee carried out i the followig steps: Step-1 Developmet of relatioship betwee temperature ad absolute iteral eergy. Step-2 Modelig of ideal dual diesel cycle. Step-3 Modelig of Producer gas fuel ad diesel fuel dual cycle A real sigle cylider dual fuel egie specificatio (Table 1) has bee used for all calculatios. TABLE 1: Specificatio of Egie Egie Type 4 Stroke diesel fuel egie Stroke 125mm Bore 105mm Number of cyliders 1 Combustio system direct ijectio Compressio ratio 17.5 RPM 2500 Assumptios i Combustio Modelig: 1. A ideal diesel cycle is cosidered for the aalysis. 2. Thermodyamic properties are assumed uiform throughout the combustio chamber volume. The gaseous miture behaves as a ideal gas. 3. The combustio process results i complete combustio. 4. To simplify the combustio process, the itermediate steps of chemical kietics are ot cosidered. 5. The combustio products are limited to water vapor, carbo dioide ad iert itroge gas. Figure 1Ideal Diesel Egie Goverig Equatios The goverig equatios for the cycle (fig1) are aalyzed separately oe by oe as give below. 695

3 A charge of pure air ad producer gas is compressed isetropically from state 1 to state 2 ad after compressio the pressure ad temperature icreases ad which are calculated by applyig first law of thermodyamics. The whole compressio process is assumed to be divided ito N umber of small steps where, dv V V (1) 1 ( varies from 1 to N) From first law of thermodyamics, du=δq δw, where du is the chage i iteral eergy after very small chage i volume durig the process, δq is the heat trasfer which is zero durig isetropic compressio process ad dw=p.dv.i this case it is the work doe by the system durig th iterval P + P- 1 ( V V - 1) 2 Hece equatio (1) yields, - (2) P +P-1 UT -U0 - UT-1 -U 0 = - (V -V -1 ) 2 For iterative solutio techique, the above equatio assumes the form as give below f ( U ) = éu ( T )-U ( 0) ù- éu ( T -1 )-U ( 0) ù ë û ë û P + P + -1 V -V 2 ( -1) where, P - 1, V - 1, T - 1 are the pressure, volume, ad temperature before th iterval ad are kow apriori; P, V ad T are the pressure, volume ad temperature after the th iterval durig the compressio stroke. From equatio of state V 1 T P = - P (5) - 1 V T - 1 The solutio of equatio (4) is obtaied umerically assumig the value of T 1 so that f(u)=0. By repeatig the same process the pressure ad temperature at the ed of compressio ca also be calculated.for the combustio process (i.e. process 2-3 ad process 3-4), the iteral eergy values at differet temperatures for these gaseous compoets preset i air ad alterative fuel were obtaied from stadard data [12]. A empirical relatioship betwee temperature ad absolute iteral eergy for differet gaseous compoets that are preset i air ad producer gas is obtaied by plottig absolute iteral eergy values at differet temperatures ad fittig 5 th degree polyomial curve usig curve fittig algorithm i MATLAB ad the correlatios obtaied are show i Table- III.Geeral combustio equatio for bled of Producer gas ad Diesel is give i equatio (6), i which m fd ad m fp are the total umber of moles of diesel &Producer gas respectively. m fd C 12 H 26 + m air [0.79N O 2] + m fp[a 1 CO + a 2 CH 4+ a 3 H 2+ a 4 CO 2+ a 5 N 2+ a 6 O 2] = B 1 CO 2+ B 2 H2 O [ m air +a 5 m fp ] N 2 (3) (4) (6) Here a s are the mole fractios of differet compoets presets i the producer gas. Assume that m f moles of diesel fuel are supplied from time t 1 to t 2 secods after compressio ad this iterval is divided ito a large umber of itervals i.e. T,so that i dttime dm fd g-moles of fuel are supplied i each iterval.therefore, m dm (7) fd T fd It is also assumed that i each iterval mole fractio of total moles of diesel preset is bured.before combustio i 1 st iterval the moles of diesel preset aredm fd. After combustio i 1 st iterval the moles of diesel preset are [(1-) dm fd ].So,amout of diesel fuel bured i th iterval is 1 (1 ) dmfd 1 (1 ) dmfd So, total umber of moles of air required for complete combustio is give by mair ì ï æpv öü í 170 mfd ï ýb ç è RT ø act = ïî ïþ (9) { b } act Similarly, equivalece ratio, f is give by f = b st bact (8) (10) bst ca be calculated by takig the value of molecular weight of air ad producer gas. Usig Eq. (6-10), the moles for differet compositio of gaseous miture preset before ad after each small step ca be foud out for both costat volume combustio (process 2-3) ad costat pressure combustio (process 3-4)ca be evaluated from the TABLE-II ad TABLE- III respectively, for th step.the process 4-5 of isetropic epasio is simulated i a similar maer as process 1-2. PROCESSING OF RESULTS The proposed umerical model usig Eq. (1-10), is simulated usig MATLAB codes. For solvig the model, each coordiate of the cycle has bee calculated alog with the work doe ad thermal efficiecy for differet equivalece ratio o dual cycle. The result obtaied are plotted i Fig. 2, 3 ad 4. For each process the umber of divisio take is 100 ad for simplicity the percetage of diesel bured at costat volume is assumed to be 50% (i.e. y = 0.5). A sigle cylider 4 stroke direct ijectio dual fuel egie is used for all calculatios. Table-I gives the complete specificatio of the egie uder cosideratio. The values of pressure, volume, ad temperature at the begiig of compressio process are take as N/m 2 (P 1), m 3 (V 1 ), 300K (T 1 ) respectively. TRENDS AND RESULTS It is observed from the variatio of efficiecy with equivalece ratio plotted i Fig. 2 that the efficiecy decreases as 696

4 icreases ad it is also clear from the Fig. 2, that efficiecy is higher whe the percetage of diesel is less (or i other words percetageproducer gas is high) due to homogeous miture of producer gas ad air prepared before the combustio. Figure 4 Plot of maimum temperature after combustio at various equivalece ratio, Figure 2Variatio of efficiecy for differet percetage of diesel fuel used i combustio with The variatio i work output with is plotted i Fig. 3 ad it is observed that work doe is maimum for pure diesel i all rage of, reaso beig the higher calorific value of diesel compared to producer gas. CONCLUSION From the results ad discussios preseted i the precedig sectio followig importat coclusios are draw. I. The thermal efficiecy of a pure diesel egie as well as of dual fuel egie (producer gas ad diesel) decreases with the equivalece ratio. The decreasig tred is obvious also sice icrease i equivalece ratio implies rich miture. II. The maimum cycle temperature is higher for pure diesel amogst all the combiatio of dual fuel whe egie rus o richer miture. So it ca be cocluded that by usig producer gas, good efficiecy ca be achieved alogwith lower value of maimum temperature which costraisno formatio temperature. III. A sharp icrease i work output is observed as the equivalece ratio icreases due to more fuel ijectio. REFERENCES Figure 3 Plot of work doe at differet percetage of diesel fuel used i combustio with I fig 4, it is further observed that pure diesel, whe rus o leaer miture i.e. < 1, themaimum temperatureattaied i the cycle is less compared with other cases whe it rus o dual fuel but it icreases whe the egie rus o richer miture i.e. >1 which causes the formatio of NO. [1] J. I. Ramos, Comparisos betwee thermodyamic ad oe dimesioal combustio models of spark-igitio egies, Departmet of Mechaical Egieerig, Caregie-Melto Uiversity. Pittsburgh, Pesylvaia, 15213, USA, [2] F. Payri ad J. Beajes, A pheomeological combustio model for direct ijectio, compressio igitio Egies, Departmet of Thermal Egies, Polytechic Uiversity of Valecia Apdo, 22012,46071, Valecia, Spai, [3] Z. Liu ad G. A. Karim, Kock characteristics of Dual-Fuel egies Fuelled with Hydroge Fuel, J. Hydroge Eergy, Vol. 20, pp , [4] G. De Nicolao, R. Scattolii ad C. Siviero, Modelig the Volumetric efficiecy of IC Egies: Parametric, No Parametric ad Neural techiques, PII: S (96) , Vol. 4, No. 10, pp , Pavia, [5] D. Zhag ad S. Ii. Frakel, A Numerical Study of atural gas combustio i a lea bur egie, PII: SOOl6-2361(98)0@048-9 Fuel Vol. 77, No. 12, pp , Thermal Sciece ad 697

5 Propulsio Ceter, School of Mechaical Egieerig, Purdue Uiversity,1998. [6] U. Kesgi, Study o the desig of ilet ad ehaust system of a statioary iteral combustio egie, Departmet of Naval Architecture, Yildiz Techical Uiversity, TR , Besiktas, Istabul, Turkey, , [7] Z. Sahi, O. Durgu, Multi-zoe combustio modelig for the predictio of diesel egie cycles ad egie performace parameters, Karadeiz Techical Uiversity, Trabzo, Turkey, , [8] Y. She, J. Bedford, I. S. Wichma, Thermodyamic modelig of direct ijectio methaol fueled egies, Applied Thermal Egieerig, 29, , Michiga State Uiversity, USA, [9] Y. Ra, R. D. Reitz, A combustio model for IC egie combustio simulatios with multi-compoet fuels, Egie Research Ceter, Uiversity of Wiscosi-Madiso, [10] D. Ghosh, Combustio modelig of Hydroge aided Diesel- Producer gas dual fuel compressio igitio egie, Birla Istitute of Techology, Mesra , Rachi, [11] V. I. Golovitchev ad J. Yag, The costructio of the combustio models for RME Bio-diesel fuel for ICE applicatio,departmet of Applied Mechaics, Chalmers Uiversity of Techology, S , Goteborg, Sweede,2009. [12] TABLE II: Number of moles for differet compoets (for costat volume process) Compoets th iterval before combustio th iterval after combustio 1 (1 ) 1 (1 ) DIESEL (1 )dm dm CO y ( 1) 1 m 1 a y 1 1 m a y ( 1) CH 4 1 m 1 a y ( 1) H 2 1 m 1 a 12 ( 1) 1 1 (1 )() dm y 1 1 m a y 1 1 m a (1 ) dm CO 2 y ( 1) + m 1 (a + a ) + a m y + 1 m (a + a ) + a m O m + a m y ( 1) m 1 (0.5a + 2a + 0.5a ) 18.5 ( 1) 1 1 (1 )() dm 0.21m + a m y 1 m (0.5a + 2a + 0.5a ) (1 ) dm N m + a m 0.79m + a m 698

6 TABLE III: Number of moles for differet compoets (for costat pressure process) Compoets th iterval before combustio th iterval after combustio 1 (1 ) 1 (1 ) DIESEL (1 ) dm dm CO ( 1) 1 1 m (1 y) a 1 1 m (1 y) a CH 4 ( 1) 1 1 m (1 y) a 1 1 m (1 y) a 12 (1 + 1) 12 (1 + ) CO (1 )() dm + y + (1 y) ( 1) (a 1 + a ) + a 1 + y + 1 (1 )() dm (1 y) 1 (a + a ) + a m m 0.21m + a m (1 y) ( 1) m 1 (0.5a + 2a ) 0.21m + a m (1 y) 1 m (0.5a + 2a ) O (1 + 1) 1 1 (1 )() dm 18.5 (1 + ) 1 1 (1 )() dm 0.5a m 0.5a m N m + a m 0.79m + a m 699