Study On Spark Induced Compression Ignition Combustion Process And Emission Characteristics Of Gasoline Engine

Spark induced compression ignition(SICI)combustion is a potential new combustion mode for gasoline engines.It can effectively expand the load range of HCCI combustion,effectively connect SI combustion and HCCI combustion,and achieve a smooth transition between the two combustion modes.In this study,a four-stroke single cylinder diesel engine was converted into an electronic controlled gasoline engine which can control ignition and fuel injection in the intake port.Then the engine experimental platform is built,including the design and processing of the engine fuel supply system,the design and processing of the engine cooling system,the design and debugging of the engine electronic control system and other related building work.In this paper,an experimental study on SICI combustion is carried out.Air-diluted SICI combustion and EGR-diluted theoretical air-fuel ratio SICI combustion are realized respectively by using air heater to heat intake air.The main conclusions of the experimental study are as follows:(1)There is a criteria for SICI combustion: double peaks in pressure rise rate curve,left concave of heat release rate curve.Increasing inlet temperature,decreasing engine speed and increasing engine load will all make the ignition advance angle boundary of air-diluted SICI combustion move backward,and SICI combustion is easier to achieve.(2)With the increase of ignition advance angle,the air-diluted SICI combustion phase is advanced,the combustion speed is accelerated,and the compression combustion ratio is increased.There is an optimum ignition advance angle at which the IMEP of air-diluted SICI combustion is the largest.With the increase of ignition advance angle,CO emissions almost remain unchanged?HC emissions and NOx emissions is increased.(3)With the increase of load,the ignition advance angle at which air-diluted SICI combustion is just happened decrease,the combustion phase advance,the maximum cylinder pressure and the peak pressure rise rate increase,the combustion duration decreases and the IMEP increases.As the load increases,CO and HC emissions decrease,NOx emissions increases.(4)With the increase of air-fuel ratio,the ignition advance angle at which air-diluted SICI combustion is just happened decrease and the combustion phase advance,the peak values of cylinder pressure,pressure rise rate and heat release rate of SICI combustion increase first and then decrease(with the exception of?=1.3);the IMEP of SICI combustion increases with the increase of air-fuel ratio.With the increase of air-fuel ratio,CO emissions of SICI combustion change irregularly,but remain in the range of 0.08%-0.10% volume fraction,HC emissions decrease first and then increase,and NOx emissions increase first and then decrease.(5)Compared with SI combustion,air-diluted SICI combustion has faster combustion speed,earlier combustion phase,and the load can reach the level near to SI combustion.Moreover,the fuel economy of air-diluted SICI combustion is better than that of SICI combustion.The CO and HC emission of air-diluted SICI combustion is better than that of SI combustion,but the NOx emission of air-diluted SICI combustion is higher than that of SI combustion.(6)Increasing load,decreasing EGR rate and decreasing engine speed will all make the ignition advance angle boundary of EGR-diluted theoretical air-fuel ratio SICI combustion move backward,and EGR-diluted theoretical air-fuel ratio SICI combustion is easier to achieve.(7)With the increase of ignition advance angle,EGR-diluted SICI combustion phase advance,cylinder pressure peak value increase,compression ignition ratio increase,heat release peak value increase,combustion duration decrease and IMEP increase.With the increase of ignition advance angle,the CO,HC and NOx emissions of EGR-diluted SICI combustion increases.(8)With the increase of EGR rate,the combustion phase of EGR-diluted SICI combustion is advanced,the peak pressure of cylinder increases,the peak pressure rise rate decreases,the heat release increases and the peak heat release rate decreases.With the increase of EGR rate,the combustion duration of EGR-diluted SICI combustion varies irregularly and the IMEP increases.With the increase of EGR rate,CO and HC emissions of EGR-diluted SICI combustion first increase and then decrease,and NOx emissions significantly decrease.(9)The load of air-diluted SICI combustion and EGR-diluted theoretical air-fuel ratio SICI combustion can reach the level of SI combustion,which can expand the load of HCCI combustion.The CO and HC emission of EGR-diluted theoretical air-fuel ratio SICI combustion is slightly higher than that of air-diluted SICI combustion,but the NOx emission is much lower than that of air-diluted SICI combustion.Moreover,EGR-diluted theoretical air-fuel ratio SICI combustion is more convenient to use three-way catalytic converter for exhaust post-treatment,and the combustion is cleaner..