| Motorcycle plays a very important role in civilian daily life,especially for Asia.In China,India,Indonesia,Thailand,and Vietna m,their motorcycle number s make up over 60% of the passenger vehicle fleet and the total ownership go up to 319 millio n unt il 2018.Such a large operat ion frequency and ownership have caused a huge load to energy and environment.The effective way for relieving or solving abovement ioned problems are to improve the engine performance s.Cycle to cycle variat ion(CCV)is main limtt ing factor for improving engine performance s,and for engines of motorcycles used,because motorcycle engins a lmo st are single-cylinder and operate under a wider range of speed and load relat ive to cars,thus CCV occurs more frequent ly.In this work,the in-cylinder work progress of three displacement engines(125 ml,300 ml and 500 ml)are investigated by combining experiment and calculat ion in detail.The research content is divided into two parts,1)The effect of engine structure on CCV;2)The effect of intake fluctuat ion and chemical react ion on CCV.First part,the main results are as following: 1)The engine rig test was set,the engine operat ion parameters were measured as the boundary condit ions,and the emulat ional results were calibrated with experimental results;2)The experimental results show that that under low load(40%)as the speed increases,the CCV increases more quickly for large displacement engines.COVPmax increases by 12.5% when the spee d rises from 3000 rpm to 7000 rpm for 125 ml engine,while this increase rises to 127.3%for 500 ml engine.Under high loads,the influence of speed on CCV is reduced for all three engines,especially for 500 ml engine,COVPmax increases very gent ly when speed increases as abovement ioned;3)Combining experiment and simulat ion,how engine structure to affect CCV is analyzed in detail;4)The emulat ional result s show that the distance between flow and flame center are 16.8 mm,7.12 mm,6.98 mm respectively for 125 ml,300 ml and 500 ml,this is consistent with experimental result,and the important parameter reflected CCV is found.Second part,first ly the effects of intake fluntuat ion and chemical reaction on CCV are invest igated in detail by novelt y simulat ion set up.The main resulus are following: 1)In order to invest igate the effect of intake fluntaut ion on CCV,during simulation only intake pressure was changed(from cyclic intake pressure to cyclis average intake pressure),the results show that the maximum variat ion of in-cylinder presseure is3.5%,6% respect ively for average and transient intake pressure;2)in order to invest igate the effect of chemical react ion on CCV,during simulat ion only ignit io n process was changed(from normal ignit ion to misfire),the results show that the variat ion of flow field decreases 278.06% from normal ognit ion to misfire.In fact,whatever intake fluctuat ion or chemical reactio n,they contribute to engine CCV by affecting flow field’s motion.In this manuscriput,the source of CCV is deeply invest igated,the correlat ion between operated stabilit y and design parameters is also studied,this provides implicat ions for the development and design of motorcycle engines. |
