Gasoline direct injection(GDI)engine is widely used in the passenger vehicle market due to its excellent performance,but its particulate emissions problem has not been completely resolved since it was applied.Some researches indicated that oxygenated fuels such as alcohol fuel could play a positive role in reducing particulate emissions.So ethanol is selected as the research object in this paper to study what impacts there will be on the GDI particulate emissions character when changing ethanol-gasoline blend.In order to make the research more comprehensive,this paper applied two research methods: visual optical measurement and bench test.In this paper,the main conclusions are as follows:1.A visualization constant volume combustion bomb platform was built to simulate the in-cylinder combustion process of the real GDI engine.The optical platform could be used to study what effects there will be on the in-cylinder particle transient generation process when the ethanol-gasoline blend was changed.The simulation of in-cylinder high temperature and high pressure environment is achieved by the use of acetylene combustion.In order to improve the accuracy,this paper applied forward illumination light extinction to study spray and in-cylinder particle transient generation process.At the same time,the monitoring of transient combustion process is achieved by natural flame luminosity.2.A GDI engine test bench was built to explore GDI engine’s exhaust particulate emissions characteristic impact of ethanol-gasoline blend.The test bench was applied with a second-level exhaust dilution system,and the analysis of diluted particulate’s mass concentration,number concentration and size distribution was done by a engine exhaust particle sizer.3.It could be found in the visual spray test that spray cone angle would get smaller,the spray penetration was bigger with the increase of ethanol-gasoline blend in the low temperature environment.Also spray cone angle would get bigger or essentially unchanged,the spray penetration was smaller or essentially unchanged with the increase of ethanol-gasoline blend in the high temperature environment.4.This paper studied the in-cylinder transient combustion process by applying natural flame luminosity.It could be found that ignition delay reduced slightly,flame speed was higher,low temperature reaction time and combustion duration was shorter when the ethanol-gasoline blend was higher.Also when the ethanol-gasoline blend got higher,the flame would glow earlier,the peak natural flame luminosity would be higher.While the natural flame luminosity decreased faster when ethanol-gasoline blend got higher.5.This paper also studied the in-cylinder particle transient generation process though applying forward illumination light extinction.It could be found that particle would appear earlier when ethanol-gasoline blend got higher.At the same time,when ethanol-gasoline blend was higher,peak particle transient mass would be higher and particle’s oxidation rate could be higher too.6.This paper did some research on the engine test bench,some conclusions are as follows:i.In the idle and low-speed small-duty operating condition,ethanol-gasoline blend have no significant effect on particulate emissions reduction.Because when the environment’s temperature was low,the spray quality was lower,the particle’s oxidation rate was not high enough.So the particulate emissions were even higher when the GDI engine was running higher ethanol content fuel in some operating conditions.ii.In the most operating conditions whose lamada was set at 1,the increase of ethanol-gasoline blend showed a remarkable effect on accumulation particulate emissions reduction.iii.The increase of ethanol-gasoline blend showed a remarkable effect on particulate emissions reduction when the engine worked on large torque operating conditions.Even the GDI engine worked on rich mixture,the exhaust particulate emissions would not show a significant change when the engine was running on E30. |