Performance of an Otto engine with volumetric efficiency Rahim Ebrahimi

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1 Perormance o an Otto engine with olumetric eiciency Rahim Ebrahimi Department o Agriculture Machine Mechanic, Shahrekor Unierity, P.O. Box 5, Shahrekor, Iran Rahim.Ebrahimi@gmail.com Abtract: In thi paper, the perormance o an Otto engine i ealuate uner ariable olumetric eiciency. Finitetime thermoynamic i ue to erie the relation between power output an thermal eiciency at ierent compreion ratio an olumetric eiciency or an air-tanar Otto cycle. The eect o the olumetric eiciency on the irreerible cycle perormance i igniicant. It wa oun that the eect o olumetric eiciency on the cycle perormance i obiou, an they houl be coniere in practice cycle analyi. The concluion o thi inetigation are o importance when coniering the eign o actual Otto engine. [Journal o American Science ;6(:7-]. (ISSN: 55-. Keywor: Volumetric eiciency; Irreeribility; Analyi; Perormance; Otto cycle Nomenclature B contant relate to heat traner c p peciic heat at contant preure c peciic heat at contant olume mep riction mean eectie preure Q in heat ae to the working lui Q out heat rejecte by the working lui Q LHV lower heating alue o the uel R air air contant o the working lui m& ma low rate o the uel m& t ma low rate o the air uel mixture ma m air uel ratio N r c T P out engine pee compreion ratio temperature power output o the cycle V olume o the ga in the cyliner Greek ymbol c compreion eiciency com combution eiciency e expanion eiciency th thermal eiciency o the cycle γ ρ air olumetric eiciency peciic heat ratio inlet air enity equialence ratio Subcript,,, tate point toichiometric conition. Introuction A tuy o ga cycle a the moel o internal combution engine i ueul or illutrating ome o the important parameter inluencing engine perormance. In the lat two ecae, by uing inite time thermoynamic theory, many optimization tuie bae on ariou perormance criteria hae been carrie out or enoreerible an irreerible heat engine moel [Chen et al., ; Ge et al., 8; Ebrahimi, 9a]. Lior an Ruy (988 conucte an aailability analyi o an ieal Otto cycle with intantaneou burning o the uel. Orlo an Berry (99 euce the power an eiciency upper limit or internal-combution engine. They erie the maximum work or power an the correponing eiciency boun. Angulo-Brown et al. (996 examine the perormance o an irreerible air-tanar Otto cycle by taking into account the inite-time eolution o the cycle compreion an power troke an gathering the global loe in a iipation term repreente by a riction orce linear with the piton mean elocity. Chen et al. (998 erie the relation between the net power an the eiciency o the Otto-cycle with heat-traner lo. Chen et al., ( etermine the characteritic o power an eiciency or Otto cycle with heat traner an riction loe. Ficher an Homan ( conclue that a quantitatie imulation o an Otto-engine behaior can be accurately achiee by a imple Noiko moel with heat leak. Ozoyal (6 gae the ali range o the heat traner lo parameter o the Otto an ieel cycle with conieration o the heat lo a a percentage o the uel energy. Rocha-Matinez et al. (6 preente a impliie irreerible Otto-cycle moel with luctuation in the combution heat. Parlak an Sahin (6 eine the internal 7 eitor@americancience.org

2 irreeribility by uing entropy prouction an analyze the eect o the internal irreeribility on the perormance o the irreerible reciprocating heat engine cycle. Abu-Naa et al. (7 tuie on thermoynamic analyi o park ignition engine. They implemente a theoretical moel o Otto cycle, with a working lui coniting o ariou ga mixture. Ge et al., (8 analyze the perormance o an air tanar Otto cycle. In the irreerible cycle moel, the non-linear relation between the peciic heat o the working lui an it temperature, the riction lo compute accoring to the mean elocity o the piton, the internal irreeribility ecribe by uing the compreion an expanion eiciencie, an the heat traner lo are coniere. Ebrahimi (a, b, c etermine the characteritic o power an eiciency or Otto cycle with engine pee, equialence ratio an combution eiciency. A can be een in the releant literature, the inetigation o the eect o olumetric eiciency on perormance o Otto cycle oe not appear to hae been publihe. Thereore, the objectie o thi tuy i to examine the eect o the olumetric eiciency on perormance o air tanar Otto cycle.. Cycle moel An air-tanar Otto cycle moel i hown in igure. Proce i a reerible aiabatic compreion, while proce i an irreerible aiabatic proce that take into account the internal irreeribility in the real compreion proce. The heat aition i an iochoric proce. Proce i a reerible aiabatic expanion, while i an irreerible aiabatic proce that take into account the internal irreeribility in the real expanion proce. The heat rejection i an iochoric proce. From the contant olume proce, the heat ae to the working lui i Qin mc & t ( T T ( The total energy o the uel per econ input into the engine can be gien by: (Heywoo, 988 Quel comm& QLHV ( The heat lo through the cyliner wall i gien in the ollowing linear expreion (Chen et al., 8, Ebrahimi, 9b Qht mb & t ( T + T ( Since the total energy o the eliere uel Q uel i aume to be the um o the heat ae to the working lui Q an the heat leakage Q, in ( Qin Quel Qht comm& QLHV mb & t T + T ( The intake ytem -the air ilter, carburetor, an throttle plate, intake maniol, intake port, intake ale- retrict the amount o air which an engine o ht gien iplacement can inuct. The parameter ue to meaure the eectiene o an engine inuction proce i the olumetric eiciency. It i eine a the olume low rate o air into the intake ytem iie by the rate at which olume i iplace by the piton: m& a (5 ρairvn The relation between an m&, between an m& t are eine a (Heywoo, 988: ρairvn m& (6 ( ma m an ρ airvn m& t + (7 ( ma m P Preure Volume V Figure. P V iagram or the air tanar Otto cycle The compreion ratio, r c, i eine a: rc V V (8 For the procee an, one ha T Tr γ c (9 T Tr γ c ( For the two reerible aiabatic procee an, the compreion an expanion eiciencie can be eine a (Chen,, Ebrahimi, c: c ( T T ( T T ( e ( T T ( T T ( Subtituting equation ( into equation (9 yiel: γ T ( r c + c T ( c Combining equation (, (, (6 an ( gie: 8 eitor@americancience.org

3 Q ( m m ( m m γ + c ( air ( γ c( Rair ( γ + B c com LHV a + a + T r R B T ( Subtituting equation ( an ( into equation ( yiel: γ ( erc e+ Q ( m m + ( m m γ c ( air ( γ c( Rair ( γ + B c com LHV a a + T r + R B T (5 The ata o total motore riction mean eectie preure or eeral our troke cycle, our cyliner park ignition engine between 85 an cm iplacement, at wie open throttle, a a unction o engine pee (Ab Alla, are well correlate by an equation o the orm: mep N +.8N (6 Thereore, the lot power ue to riction i mepv N p ri (7 VN ( N +.9N Auming an ieal, non-reacting ga with peciic heat, the net actual power output o the Otto cycle engine can be written a: Potto Qin Qout pri ρ airvnr air + ( γ ( ma m γ rc + c T c c comqlhv( ma m + ( ma m + γ (8 T ( rc + c ( Rair ( γ B c( Rair ( γ + B γ ( erc + e ( VN N N The thermal eiciency o the Otto cycle engine i expree by th Potto Qin (9 where Q i: in in t ρ VNR air air ( Q mc & T T + c ( γ ( ma m Q ( m m ( m m γ + c ( air ( γ ( c com LHV a + a + T r R B Rair ( γ + B γ T ( rc + c Notice that both power an eiciency are conex unction o the compreion ratio.. Numerical example an icuion A it can be clearly een rom Eq. (8 an (9, the thermal eiciency an the power output o the Otto cycle are epenent on the olumetric eiciency. In orer to illutrate the eect o thi parameter, the relation between the power output an the compreion ratio, between the thermal eiciency an the compreion ratio, an the optimal relation between power output an the eiciency o the cycle preente in igure. The alue o the contant an the parameter ue in thi example are ummarize in Table. Table. Contant an parameter ue in the numerical example [Heywoo, 988; Ebrahimi, 9b; Chen et al., 8; Ge et al., 8] bore troke mm contant relate to heat.7 kj kg K traner lower heating alue o the uel kj kg air uel ratio at toichiometric.685 conition engine pee rpm compreion ratio 7 intake temperature K compreion eiciency.97 expanion eiciency.97 combution eiciency % olumetric eiciency 6 % peciic heat ratio. equialence ratio Figure - how the eect o the olumetric eiciency on the cycle perormance with heat reitance, internal irreeribility an riction loe. From thee igure, it can be oun that the olumetric eiciency play important role on the perormance o the Otto engine. It i clearly een that the eect o olumetric eiciency on the perormance o the cycle i relate to compreion 9 eitor@americancience.org

4 ratio. They relect the perormance characteritic o a real irreerible Otto cycle engine. The power output eru compreion ratio characteritic an the thermal eiciency eru compreion ratio characteritic are approximately parabolic like cure. It houl be note that the heat ae an the heat rejecte by the working lui increae a the olumetric eiciency increae. It can alo be een that the cure o power output eru thermal eiciency are loop hape a i common to almot all real heat engine (Ebrahimi, 9b. Power output (kw 6% % 6 Compreion ratio Figure. Eect o olumetric eiciency on the ariation o the power output with compreion ratio Reerring to Fig. an, it can be conclue that, throughout the compreion ratio range, the power output an thermal eiciency increae with the increaing olumetric eiciency. Thi can be attribute to the act that the ierence between heat ae an heat rejecte increae with the increaing olumetric eiciency. Thi i conitent with the practical working olumetric eiciency o park ignition engine (Heywoo, 988. From thee igure, it can be reulte that the maximum power output an the maximum thermal eiciency increae about 69.6% an % when olumetric eiciency increae %. The reult alo reeale that the optimal compreion ratio correponing to maximum thermal eiciency point an the working range o the cycle increae a the olumetric eiciency increae. In other wor, the optimal compreion ratio correponing to maximum thermal eiciency point an the working range o the cycle increae about 5% an 5.% when olumetric eiciency increae %. While the optimal compreion ratio correponing to 8% maximum power output point remain contant with the increaing olumetric eiciency. Thermal eiciency (% % 8% 6% 6 Compreion ratio Figure. Eect o olumetric eiciency on the ariation o the thermal eiciency with compreion ratio Power output (kw % 8% 6% Thermal eiciency (% Figure. Eect o olumetric eiciency on the ariation o the power output with thermal eiciency Reerring to Fig., it can be een that the power output at maximum thermal eiciency an the thermal eiciency at maximum power output improe when the olumetric eiciency increae. In other wor, the power output at maximum thermal eiciency an the thermal eiciency at maximum power output increae about 5.% an 8.7% when olumetric eiciency increae %. eitor@americancience.org

5 -Concluion In thi paper, the eect o olumetric eiciency on the perormance o an Otto cycle uring the inite time are inetigate. The general concluion rawn rom the reult o thi work are a ollow: Throughout the compreion ratio range, the power output an thermal eiciency increae with the increaing olumetric eiciency. The optimal compreion ratio correponing to maximum thermal eiciency point an the working range o the cycle increae a the olumetric eiciency increae. While the optimal compreion ratio correponing to maximum power output point remain contant with the increaing olumetric eiciency. The power output at maximum thermal eiciency an the thermal eiciency at maximum power output improe when the olumetric eiciency increae. The reult o thi inetigation are o importance when coniering the eign o actual Otto engine. Reerence. Abu-Naa E, Al-Hinti I, Akah B, Al-Sarkhi A. Thermoynamic analyi o park-ignition engine uing a ga mixture moel or the working lui. International Journal o Energy Reearch 7;: 6.. Ab Alla GH. Computer imulation o a our troke park ignition engine. Energy Conerion & Management ;:-6.. Angulo-Brown F, Rocha-Martinez JA, Naarrete-Gonzalez TD. A non-enoreerible Otto cycle moel: improing power output an eiciency. Journal o Phyic D: Applie Phyic, 996;9:8 8.. Chen L, Wu C, Sun F, Wu C. Heat traner eect on the net work output an eiciency characteritic or an air tanar Otto-cycle. Energy Coner Manage 998;9(7: Chen L, Zheng T, Sun F, Wu C. The power an eiciency characteritic or an irreerible Otto cycle. Int J Ambient Energy ;(: Chen L, Ge Y, Sun F. Uniie thermoynamic ecription an optimization or a cla o irreerible reciprocating heat engine cycle. Proc IMechE Part D: J Automobile Engineering 8;: Chen L, Sun F, Wu C. The optimal perormance o an irreerible Dual-cycle. Applie Energy ;79(:. 8. Ebrahimi R. Eect o cut-o ratio on perormance o an irreerible Dual cycle. Journal o American Science 9a;5(: Ebrahimi R. Thermoynamic imulation o perormance o an enoreerible Dual cycle with ariable peciic heat ratio o working lui. Journal o American Science 9b;5(5: Ebrahimi R. Eect o gaoline-air equialence ratio on perormance o an Otto engine, Journal o American Science a;6(:-5.. Ebrahimi R. Theoretical tuy o combution eiciency in an Otto engine, Journal o American Science b;6(:-6.. Ebrahimi R. Engine pee eect on the characteritic perormance o Otto engine, Journal o American Science c;6(:- 8.. Ficher A, Homan KH. Can a quantitatie imulation o an Otto engine be accurately renere by a imple Noiko moel with a heat leak? J Non-Equil Thermoy ;9(:9 8.. Ge Y, Chen L, Sun F. Finite time thermoynamic moeling an analyi o an irreerible Otto cycle. Applie Energy 8;85(7: Heywoo JB. Internal combution engine unamental. New York: McGraw-Hill; Lior N, Ruy GL. Secon-law analyi o an ieal Otto cycle. Energy Coner Manage 988;8:7. 7. Orlo VN, Berry RS. Power an eiciency limit or internal-combution engine ia metho o inite-time thermoynamic. J Appl Phy 99;7(:7. 8. Ozoyal OA. Heat lo a percentage o uel energy in air tanar Otto an ieel cycle. Energy Con Manage 6;7(7 8: Parlak A, Sahin B. Perormance optimization o reciprocating heat engine cycle with internal irreeribility. J. Energy Int., 6;79(: 5.. Rocha-Matinez JA, Naarrete-Gonzalez TD, Paia-Miller CG, et al.. A impliie irreerible Otto-engine moel with luctuation in the combution heat. Int J Ambient Energy 6;7(:8 9. /8/9 eitor@americancience.org

Journal o Aerian Siene ;6( obution heat. Parlak and Sahin (6 deined the internal irreeribility by uing entropy prodution and analyzed the eet o the in

Journal o Aerian Siene ;6( obution heat. Parlak and Sahin (6 deined the internal irreeribility by uing entropy prodution and analyzed the eet o the in Journal o Aerian Siene ;6( Perorane o an Otto engine with oluetri eiieny Rahi Ebrahii, Daood Ghanbarian, Mahoud Reza Tadayon. Departent o Agriulture Mahine Mehani, Shahrekord Unierity, P.O. Box 5, Shahrekord,