Experimental Study And Numerical Simulation On Spray Characteristics Of Diesel-gasoline Blends

With the increasing attention to environmental protection,reducing pollutant emissions and fuel consumption has become one of the important challenges facing the diesel engine field.The quality of fuel atomization directly affects the energy-saving and emission reduction of the engine.In this study,based on the physical and chemical characteristics of diesel-gasoline blends,the effect of fuel properties,injection pressure,fuel injection pulse width and ambient pressure on spray characteristics of diesel-gasoline blends were studied,using a high-pressure common rail constant volume test system.In addition,the influence of the structure of the needle valve and the angle of nozzle hole on the transient flow inside the orifice and spray characteristics was analyzed by using computational fluid dynamics software.(1)The test results show that as the increase of the volume fraction of gasoline,the spray cone angle of diesel-gasoline blends gradually increases,the spray tip penetration decreases,the spray projection area increases,the distribution curve of atomized droplet size number is shifted to the direction of small particles,the proportion of droplets with small particle size increases,the Sauter mean diameter decreases,and the atomized quality significantly improves Increasing injection pressure and ambient pressure can increase spray cone Angle and spray projection area,reduce the Sauter mean diameter,and promote fuel atomization With the increase of injection pulse width,the spray development time becomes longer,the spray tip penetration increases,the spray cone angle decreases first and then is basically similar,the spray area decreases first and then increases,and the Sauter mean diameter increases.(2)The simulation results show that,compared with the single-cone needle valve,the mass flow of the outlet of the double-cone needle valve is larger,the pressure gradient distribution and the velocity distribution in the nozzle are more uniform,the maximum velocity inside the nozzle and the velocity at the outlet of the nozzle are higher,the turbulent kinetic energy is larger,and the gas phase volume fraction is smaller.Double-cone needlevalve is adopted to improve the effective flow section at the entrance of pressure chamber,reduce throttling loss and increase fuel flow rate.Compared with the single-cone needle valve,when using the double-cone needle valve,the maximum velocity of spray core zone is higher,the spray tip penetration is larger,the Sauter mean diameter is reduced.With the increase of orifice inclination angle,the fuel flow direction changes less,the energy loss decreases,the mass flow at the orifice outlet increases,the flow velocity increases,the turbulent kinetic energy increases,and the cavitation decreases,the spray tip penetration gradually increases,the Sauter mean diameter gradually decreases,the maximum velocity of spray core zone increases,and the fuel atomization quality improves.