Study On Combustion And Emission Characteristics Of Diesel/Gasoline/Isopropanol Blended Fuel

In recent years,exhaust gas recirculation(EGR)has become an important technical means to achieve clean combustion.By introducing EGR,the oxygen concentration in the cylinder is reduced,the combustion speed is slowed down,and the combustion temperature in the cylinder is lowered,thereby achieving lower NOx emissions;However,there are problems such as a decrease in thermal efficiency,a deterioration in fuel economy,and an increase in HC and CO emissions.Adding isopropanol with higher oxygen content to diesel fuel can make combustion more complete and reduce soot emission,but it will reduce the low calorific value of fuel.The addition of gasoline with high calorific value and high evaporability in diesel fuel can improve the calorific value of the fuel,improve its atomization quality,and reduce the particulate matter emissions of the diesel engine.Based on the above ideas,two kinds of diesel/gasoline/isopropanol blends(D70G20P10and D70G10P20)were prepared by using pure diesel as the base fuel(D100)and gasoline and isopropanol as the blend fuel according to volume ratio.Firstly,the effects of gasoline and isopropanol on the physical and chemical properties of the blended fuel were studied.Then,the engine performance tests were carried out on a four-cylinder high-pressure common rail diesel engine equipped with EGR.The effects of three fuels on the combustion and emission characteristics of the engine were compared and studied.The research results show that:(1)Compared with D100,the kinematic viscosity,density,cetane number,distillation range,cold filter point and low calorific value of the D70G20P10 and D70G10P20 mixed fuels are all reduced.(2)The injection strategy of the engine under the entire load condition is pilot injection and main injection.Under the same load and EGR rate,compared with D100,the D70G20P10 and D70G10P20 mixed fuels have longer retardation period and shorter combustion duration;the peak combustion pressure and peak combustion temperature of the mixed fuel are slightly higher than D100;at medium and small loads,The peak heat release rate of the mixed fuel is higher than D100,and at high load,the peak heat release rate of the three fuels is not much different.(3)With the increase of engine load,the pilot injection duration of D100,D70G20P10and D70G10P20 fuels decreases,the main injection duration increases,the retardation period shortens,the combustion duration increases,the in-cylinder combustion pressure and the instantaneous heat release rate and the average temperature in the cylinder increase.Under the same speed and load,with the increase of EGR rate,the retardation period of the three fuels increases,and the peak in-cylinder pressure,peak heat release rate and peak combustion temperature decrease.(4)As the engine load increases,The NO_X and soot emissions of the D100,D70G20P10and D70G10P20 fuels increased.As the EGR rate increases,the soot emissions of the three fuels increase slightly,and the emissions of NO_X reduced significantly.(5)Compared with D100,the amount of soot of D70G20P10 and D70G10P20 mixed fuels decreased,the number concentration and the volume concentration of ultrafine particles of D70G20P10 and D70G10P20 mixed fuels decreased significantly,and the emission of NO_X increased.As the EGR rate increases,the number and volume concentration of ultrafine particles increase.