Compression ratio optimization in dependence of an engine load

Transcription

1 Paer ID ICLSS6-187 ICLSS-6 ug.7-set.1,6, Kyoto, Jaan Comression ratio otimization in deendence of an engine load Bronisław Sendyka 1, Łukasz Smyka, Jacek Soczówka Cracow University of echnology Kraków, l. Jana Pawła II 7 el ax bsendyka@usk.k.edu.l 1 Prof. D.Sc., Ph. D, Eng. Bronisław Sendyka, Cracow University of echnology, IPSISS M. Sc., Eng. Łukasz Smyka, Cracow University of echnology, IMIP M. Sc., Eng. Jacek Soczówka, Cracow University of echnology, IPSISS 1.bstract. he first art of the aer includes general information about comression ratio adjustment in accordance with varying engine load. Scheme shows method of achieving variable comression ratio. ttached diagram shows load of comression ratio controlling and adjustment system in deendence of engine load. Block diagram shows controlling algorithm for variable comression ratio. Included lots show controlling system resonse time to knock combustion and the way that circuit adat to different conditions of an engine work. here is also introduced comarison of rogress of theoretical efficiency of variable comression ratio engine in gasoline and CNG gas fueling system. Last art includes conclusions of using comression ratio controlling system. here is also resented benefits from emloyment of variable comression ratio and ossibilities adatation of CR (ariable Comression Ratio) engine to alternative fueling (LPG, CNG). Keywords: variable comression ratio, theoretical efficiency, knock combustion. he influence of comression ratio on arameters of an engine. Because of using the comression ratio and high-ressure additional loading it is ossible to reduce fuel consumtion for about % in comare to traditional engines about the same arameters. Emission of toxic exhaust gases like, for instance HC, NOx, CO is also reduced. Created the engine CR according to idea "downsizing ossesses arameters of exloitation considerably larger of the caacity unit. Because of the minimize limiting outline and the same the need of more frequent working of engine in full loading and full oening of throttling valve, the losses of fill fall. he energy contains in fuel will be better exloitation if the comression ratio will be nearly limits value, in which the knock combustion just aear. he icture 1 shows the influence of use of different constructional solutions on fuel reduce ratio. he use of turbocomressor causes small fall of isolated fuel consumtion and the same growth of total efficiency. Economy ratio rise u to 1-1% in relation to engine without such device (9,1). However, the use of turbocharger with simultaneous variable comression ratio allows to save to 18-% of fuel. We can get the largest economies alying high ressure loading (above 1.5 bar) and variable comression ratio. ccording to investigations of the E [8] firm we can save to 5-% of fuel (fig. 1). 5 he reduction of fuel 15 consumtion 1 [%] Maximum ower from 1L of swet caacity ig.1. he comarison of maximum ower relation obtained from 1L of swet caacity in engines of variable construction. 5kW /L low sucking engine with constant comression ratio, 7kW /L- charged engine of constant comression ratio, 9kW /L engine charged of variable comression ratio, 1kW /L high charged engine of variable comression ratio.[9,17]. datable control system. he control system has been realized on the basis on single-circuit microcontroller. he alied solution makes 1

2 ossible to include taing, the rocessing and interretation of data with generating steering sequences for steing motor in one integrated circuit. he control system has been divided into functional blocks in deendence from executed roblems. On the lowest level there are measuring sensors (fig. no.1,,,4) taking arameters of algorithm master. cross analog to-digital converter (fig. no.5) the conversion of taken arameters be holds to binary figure. he master algorithm is included in microcontroller (the fig. no.7) in mould of rogram in low-level language, which takes the entrance arameters and the answer generates in figure of sequent of movement for steing motor. he initiation of the initiating arameters, the control of the microcontroller work as well as filing of data be holds with the hel of control - calibrate external terminal (in talked over solution of comuter) communicating with the microcontroller through serial connection. his terminal serves only to observation, equalization of running of rogrammer in hase of investigations and it is not required to correct work of device. Microcontroller is searated from executive unit by searate system (the fig. no.8) reventing enetration to microcontroller of disturbances and making rogrammer more indeendent from alied mechanical solutions. he steing motor is the executive joint with the control system turning cylinder of cylindrical transmission. he control system acts in real-time assuring the immediate change of working conditions with the hel of the established corrective algorithm. On fig. the line searated elements joint with engine mechanically (the entry and exit of the control system) from rogrammer which realizing the algorithm rogrammer. 4.he alying of the variable comression ratio. he described solution is based on the location of a crankshaft on an eccentric bearing. It also enables relatively ossible comaratively fast and straight change of arameters at small ower which is necessary to adjustment. he engine eccentric bearing is controlled by toothed gear, reduction worm gear and steing motor. hanks to alying worm gear one gained self-locking of the steering system. hat is why, the alying of reduction worm gear is used only to the change of the setting of eccentric bearing. he scheme of the work of described engine with the variable comression ratio is resented below, in icture. he basic signals to steering the system are delivered from sensors of rotational seed, underressure in the intake manifold and as well as knock combustion. he microrocessor on the ground of these signals steers the running of steing motor on the ground of the mas of comression ratio in deendence of the entrance arameters. ig.. he block scheme of control system of variable comression ratio: 1- steing motor, - worm gear, - gear transmission, 4- eccentric bearing, 5- sensor of knock combustion, 6- sensor of vacuum ressure, 7- sensor of osition of throttles valve, 8- rogrammer, 9- the sensor of rotational seed and osition of crankshaft.[17] he calculations of the torque necessary to control the value of grade of comression ratio for temorary ressure in combustion chamber even 5 [MPa] have been conducted. he value of torque changes in deendence of osition eccentric bearing. he course of function of torque steing motor is resented on fig.4. he engine loading has not got large values because of alying of worm gear. ig.. he block scheme of adatable control system: 1- inductive sensor of rotational seed of the crankshaft, - sensor of absolute ressure, - two-stage sensor of osition throttles valve, 4- sensor of knock combustion, 5- the analog-to-digital converter, 6- the external terminal control - calibration, 7- microcontroller, 8- electric searation, 9- the steing motor.

3 6 5 4 orque [Nm] he value of eccentric bearing [mm] ig.4. he torque witch is necessary to steer of the variable comression ratio in deendence from the value eccentric at temorary ressure in the chamber combustion 5 [MPa]. [17] he torque, which has to be to characterize the steing motor of CR (ariable Comression Ratio) arrangement for the steady setting of the eccentric bearing, equaling mm is resented in icture 5. he calculations were conducted acceting steady ressure in chamber combustion. he angle of turn of crankshaft is variable. In this case the value of temorary ressure in chamber combustion 5 [MPa] was adated. he loading of steering system changes similarly to the ressure course in chamber combustion. Maximum loading will occur in range of 5-1º[OWK] after DC. orque [Nm],9,8,7,6,5,4,,, ngle of rotation cranckshaft [OWK] ig.5. he course of the torque oerative on the control system CR in deendence from angle rotation crankshaft after o Dead Centre.[1], [17] 5.he theoretical efficiency engine in deendence from kind of fuel. s basic of selection arameters circulation we can accet foundation that ressure and temerature of factor in circulation shouldn t cross allowable values do i do. On the fig.6 introduced Otto cycle assumed for calculations of the theoretical efficiency. ig.6. he schema of the engine work according to Ottocycle (oints: HDE) [4] he schema of calculation theoretical efficiency (4): -comression ratio: ε [1] -the volume of chamber combustion. Point on fig.6 -the volume of chamber combustion. Point C on fig.6 C -the relation of ressures and temeratures during cycle: do c do a [] -the maximum ressure value in the cycle -the ressure in cylinder. Point on fig.6 do b [] do -the maximum temerature of the cycle -the temerature of the cycle in oint on fig.6 he comression ratio has to contain in range min D a b k ε to ε a [4] max D -the volume of cylinder in oint D on fig.6 -the volume of cylinder in oint on fig.6 Heat inut to cycle: BC BC + CD [5] -heat inut to the cycle at constant volume CD - heat inut to the cycle at constant ressure q C 1 [6]

4 he theoretical efficiency of the cycle: E E 1 η [7] -heat outut from the cycle (oints E-) E C -secific heat at constant volume E C ( ) [8] E -the temerature of the cycle in oint E - the temerature of the cycle in oint k- exonent of adiabate fter substitution we receive the attern of the theoretical efficiency of the cycle (4): 1 b k 1 [ a( ) 1] q a η [9] he score of theoretical efficiency for trile-fuel owered engine; etrol, LPG, CNG is comosed on fig no.7 in all mentioned fuels systems theoretical efficiency grows together with growing comression ratio. Because bigger octane s value of LPG, CNG fuels is advised to increase ressure ratio for this systems In multi-fuel solution, variable comression ratio system is factor which allows engine adatation for different kinds of fuel. heoretical efficiency,7,6,5,4,,, Comression ratio cng lg etrol ig.7. Comaring theoretical efficiency of engine which works with Otto cycle, owered by etrol, LPG.,CNG. [1], [4], [1], [17], [] Using variable comression ratio it is ossible to reduce fuel consumtion in comare to traditional engines with comarable arameters. It is ossible to reduce emission of toxic substances like : HC, NO, CO. Because smaller dimensions of variable comression engine, it works often with full load and with full oened throttle, refill loses are reduced as well. Energy contained in fuel will be better used when comression ratio will be close to border value of knocking combustion. 6.djustment of fueling system to cooerate with variable comression ratio. Nowadays it is common to create modern engines with downsizing rule (what means; to create small engine with arameters like bigger have). herefore best suitable fueling system for CR (variable comression ratio) engines is direct etrol injection to combustion chamber. With this kind of fueling system even heavy load engine will work on homogenic mixture, otimal using its arameters on board value of knocking combustion. By half load engine will switch to work on laminar mixture simultaneously comression ratio will increase to border value of knocking combustion. his kind of fueling system allows to reduce fuel consumtion and toxic emission. 7. Conclusions. - adjusting comression ratio to engine load conditions, theoretical efficiency of engine can be increased. - variable comression ratio alication results with significant fuel consumtion reduction (u to -5%) in comarison to basic low sucking engine with constant comression ratio - comression ratio adjustment to engine work conditions has significant influence on decrease in toxic emission - ossibility of using oor fuel mixture by half loaded engine. 8. References. [1] Bernhard Maciej, Dobrzyński Stanisław Silniki samochodowe, Wydawnictwo Komunikacji i Łączności, Warszawa 1988 [] Craig, Siva, Shulenberger rial Pistons- New ormat for Imlementing ariable Comression, Innovation Engineering Inc., Brisbane 4 [] Haraldson, Goran, unestal, Per, Johansson, Bengt, Hyvonen, Jari HCCI Combustion Phasing in a Multi Link Cylinder Engine Using ariable Comression Ratio SE echnical Paer, Powetrain and luid Systems Conference & Exhibition, San Diego [4] Maćkowski Jacek Obiegi czterosuwowych silników o załonie iskrowym Politechnika Śląska, Gliwice 1987 [5] Mendler, Charles and Gravel, Roland ariable Comression Ratio Engine SE echnical Paer Series, uture Car Congress, rlington [6] Mysłowski Janusz Doładowanie silników Wydawnictwo Komunikacji i Łączności, Warszawa [7] Pischinger, S. Ladungsbewegung und Gemischbildung bei Ottomotoren mit voll variabler entilsteuren, Wiener Motorensymosium, Wien 1 [8] Pishinger Stefan, Yaici I., Kurt, Schwaderla Markus, Habermann Knut ariable Comression in SI engines, ICE 1 [9]adeusz Rychter, ndrzej eodorczyk Modelowanie matematyczne roboczego cyklu silnika tłokowego Państwowe Wydawnictwo echniczne, Warszawa 199 [1] Benefits%and%challenges%of%CR.df [11] Saab. Informacja Prasowa, 6/ [1] Swaderla Markus, Haberman, Knut, Yaici, Kurt I., ariable Comression Ratio Design Solution for uel Economy Comcets, SE echnical Paer Series. SE World Congress, Detroit 4

5 [1] Sendyka Bronisław, Kudzia Sławomir, Cygnar Mariusz, he analysis of Power suly construction and burning rocess in engines with gasoline direct injection (GDI), Konmot-utorogres 4, Zakoane [14] Sendyka Bronisław, Soczówka Jacek, Increase in General Engine Efficiency Due to lication of a ariable Comression Ratio, Konmot-utorogres 4, Zakoane [15] Sendyka Bronisław, Soczówka Jacek, Recovery of Exhaust Gases Energy by Means of urbocomound, Comodia 4, Yokohama, Jaan [16] Wajand. Jan, Werner Jan, Silniki salinowe małej i średniej mocy, Wydawnictwo Naukowo-echniczne, Warszawa 1991 [17] [18] /deer_4/session7/4_deer b-relation of temeratures during cycle [ m ]- volume of chamber combustion. Point on fig.6 C [ m ]- volume of chamber combustion. Point C on fig.6 do [Ma]- the maximum ressure value in the cycle [Ma]- ressure in cylinder. Point on fig.6 do [ K]- maximum temerature of the cycle [ K]- temerature of the cycle in oint on fig.6 [ m ]- volume of cylinder in oint D on fig.6 D [ m ]- volume of cylinder in oint on fig.6 Nomenclature ε - comression ratio a- relation of ressures during cycle BC CD E [J] -heat inut to the cycle at constant volume [J]- heat inut to the cycle at constant ressure [J]- heat outut from the cycle C [J/kgK]- secific heat at constant volume E [ºK]- temerature of the cycle in oint E [ºK]- temerature of the cycle in oint k- exonent of adiabate η- theoretical efficiency 5