Visualization Of Spray And Combustion Characteristics Of Diesel/PODE Mixture In Constant Volume Projectile And Optical Engine

Energy saving and environmental protection have always been the two main themes of engines.Diesel engines are widely used in transportation,agriculture,engineering machinery,and military fields because of their low speed,high torque,and good stability.However,their high particulate emissions limit the diesel engine’s development and application.Using oxygen-containing fuel as an alternative fuel or additive for diesel is an important way to reduce particulate emissions and achieve efficient and clean combustion in the cylinder.Polyoxymethylene dimethyl ethers(PODE)is an oxygen-containing fuel with a high cetane number,high oxygen content,no C-C bond.As an alternative fuel for diesel,it can reduce particulate emissions.When PODE is mixed with diesel,there is no need for diesel changes to the oil system and other structures.In this test,0~#diesel and PODE were selected as test fuels,and PODE was blended with0~#diesel to prepare diesel/PODE mixed fuel in volume ratios of 0%,20%,50%and 100%,respectively,which are denoted as D100,P20,P50 and P100.Based on the constant volume bomb test platform and optical engine test platform,the mixed fuel constant volume bomb spray,constant volume bomb combustion and engine in-cylinder combustion tests were performed at 100MPa,120MPa and 140MPa injection pressures.The effects of fuel characteristics on spray and combustion rules under different injection strategies are compared and analyzed.The specific results are as follows:(1)In the constant volume bomb spray characteristic test,added with PODE,the spray penetration distance,the spray cone angle and the spray area are all smaller,the atomization effect was not improved.Increasing the injection pressure can improve the atomization effect.The higher the PODE ratio,the less obvious the improvement effect.(2)In the constant volume bomb combustion characteristic test,the higher the PODE ratio,the shorter the ignition delay period of the fuel;increasing the injection pressure can shorten the ignition delay period;the higher the PODE ratio,the less the amount of soot generated,and the less self-luminous intensity of the fuel flame.Fuel injection pressure affects D100 and P20 soot generation,and has little effect on P50 and P100 soot generation.(3)In the optical engine combustion test with increasing PODE ratio,heat release rate of the fuel,the peak cylinder pressure and cylinder temperatures are decreased,shortening the ignition delay period.The peak cylinder pressure of P20 and D100 can be increased by varying the injection pressure and the injection time.When the fuel starts to ignite,the flame temperature is higher,soot formation is less,the flame temperature is lower in the middle and late stages of combustion,and soot formation is higher;the higher the PODE ratio,the less soot formation,increasing the injection pressure and the earlier injection can reduce the D100soot generation.Increasing injection pressure can reduce P20 soot generation.Increasing injection pressure and early fuel injection have no significant effect on P50 and P100 soot generation.The addition of PODE can shorten the duration of the combustion flame,make the heat release more concentrated,reduce the heat release in the later period,and have a positive significance for improving the thermal efficiency of the engine.