Experimental Study On The Effects Of Alcohol Fuel Properties On The Low Temperature Combustion Performance Of Diesel Engines

Diesel engine combustion produces a large amount of nitrogen oxides and soot,which seriously affects the ecological environment.The overuse of petroleum resources has also led to a shortage of global energy.Using alternative fuels and exhaust gas recirculation technology(EGR)has a significant influence on the thermal efficiency of the engine.Due to its mature production process and high oxygen content,ethanol received widespread attention.But the miscibility of ethanol/diesel blending is poor.And n-propanol has better miscibility than ethanol,but is limited by the higher production cost.n-Butanol can achieve better miscibility with diesel and controllable production cost,which has become a hot spot in diesel engine research in recent years.This paper mainly studies the ethanol/n-propanol/n-butanol/diesel fuel blends combustion and emission characteristics.In this study,it was attempted to investigate the performance and emission of a modified single-cylinder slectrically controlled high pressure common rail diesel engine,and the four tested fuels included a mixture of 20% ethanol and 80% diesel(E20),20% n-propanol and 80% diesel(Pr20),20% n-butanol and 80% diesel(Bu20),pure diesel(D100).The effects of the combustion and emission characteristics of the diesel engine were investigated under different EGR rate,load and speed conditions.Firstly,under the condition of low EGR rate,the blended alcohol fuel will decrease the CA50 value,and increase the maximum cylinder pressure and the maximum heat release rate,and the heat release will be more concentrated,and the indicated thermal efficiency increase,but indicated mean effective pressure will be reduced.The CO emissions and THC emissions will be reduced,but NOx emissions and SOOT emissions will be increased.Under the condition of high EGR rate,the blended alcohol fuel is more likely to cause misfire,and the NOx emissions and SOOT emissions will be decreased.When the EGR rate is greater than 35%,all fuels break the trade-off relationship between NOx and SOOT emissions.Then,with the increase of engine load,all of the CA50 value increase,and the maximum cylinder pressure and the indicated mean effective pressure increase,and the indicated thermal efficiency first increase and then decrease,while the coefficient of variation decreases,and working stability is improved.The CO emissions and SOOT emissions of the four test fuels first decrease and then increase,while the NOx emissions first increase and then decrease.With the increase of engine speed,all fuels decrease the NOx emissions.Under high engine speed and high load,THC emissions decrease for all four test fuels.In summary,in this paper,the combustion and emission characteristics of the blended alcohol fuels are explored from different perspectives of EGR rate,engine speed and engine load,which provide a preliminary theoretical analysis for the extensive application of the blended alcohol fuels,and lay a certain experimental foundation for further in-depth research in the future.