The Influence Of Additives On The Ignition Delay And Combustion Of Gasoline,Designed For Gasoline Compressed Ignition Engines

Over the last few years,people paid increasingly attention to energy and environmental problems.Stringent environmental regulations and the impact of electrification pose serious challenges on the traditional internal combustion engines,it's necessary to develop new combustion models which are clean and highly efficient.The gasoline Partially Premixed Compression Ignition(PPCI)was one of the most prospective combustion models,in PPCI,the air and fuel was partially mixed before ignition,compared with traditional diesel engines,a higher thermal efficiency and extremely lower SOOT emission could be achieved.The difficulties of spontaneous ignition must be solved to realize gasoline PPCI combustion model when the engine was underload.Intake heating was the most effective method,however,it's challengeable to realize and will reduce the economics and safety of the engine.In this study,the gasoline's self-ignition performance was improved by adding additives,to achieve stable gasoline PPCI combustion without intake heating.In this paper,the experiments was carried out to study the influence of temperature,pressure,concentration and additives on the ignition delay times of gasoline.What's more,the results can be used to the validity and applicability of the chemical kinetics mechanism of gasoline,so as to select the chemical kinetic mechanism suitable for gasoline auto-ignition combustion which will be used in the subsequent research of three-dimensional combustion simulation.The measurements indicated that:keeping the equivalence ratio a constant,the logarithm of the ignition delay times was linear with the reciprocal of the temperature;changing the pressure only would result in a set of approximately parallel straight lines;and the impacts of equivalence ratio on ignition delay depend on temperatures.Adding DTBP or PODE to gasoline could improve the auto-ignition performance,to ensure gasoline ignition under lower inlet air temperature.The more mass the additives,the lower inlet air temperature the gasoline self-ignition.A three-dimensional CFD model of gasoline PPCI was established based on a single-cylinder,coupled with chemical kinetic mechanism by the engine simulation software CONVERGE,and the study of gasoline compression ignition combustion was carried out.Firstly,the PPCI combustion with pure gasoline was studied.The results show that,under rated engine speed and low load condition,when the fuel injection advance angle was20°CA,the temperature of intake air should be heated to 65°C to achieve normal ignition,however,by adjusting the injection timing,a better effect could be achieved when the temperature of intake air is 55°C.Then the PPCI combustion with PODE-gasoline was simulated.Adding 10%PODE to gasoline to realize PPCI combustion without heating intake air,and the SOOT emission was much lower than original diesel engine under the premise of similar power.But when the addition ratio exceeded 20%,the NO_X emission would be slightly higher than the original machine.Finally,the two-stage injection strategy was proposed to optimize the process of combustion:comprehensively considering combustion and emissions performance,30%mass fraction of post-spray+10°CA injection interval was better,compared with the original diesel engine,the IMEP increased by 0.8%,NO_X and SOOT emissions decreased by 9.0%and 72.3%,respectively.