Numerical Simulation Of Flow And Atomization Characteristics Of Diesel Engine Variable Section Injector

Diesel injectors are a key component of the fuel supply system,and research on injectors is becoming increasingly important.With new processing techniques and precise control techniques,some researchers have studied the structural parameters of the orifice.The performance of variable cross-section orifices is different from that of conventional nozzles under various injection conditions.It is of great significance to study the internal flow characteristics and spray atomization characteristics of variable-section nozzles.In this paper,FLUENT simulation is used to calculate the internal flow characteristics and outlet flow characteristics of different variable cross-section orifices under different injection conditions.Based on the internal flow field simulation calculation,the injection atomization is simulated and the injection characteristics and causes of different injection conditions are analyzed.The internal gas phase volume fraction,turbulent flow energy and flow velocity distribution of each nozzle at different incident pressures,back pressures and roughness are visually displayed through the cloud diagram.The gas phase volume fraction,turbulent flow energy and mass of each nozzle outlet are compared by the line graph.Flow rate and flow rate.(1)Increasing the incident pressure increases the cavity,and the inverted cone and the equal-diameter orifice are easily super-cavitated.The increase in back pressuresuppresses voids,and the low back pressure is equal to that of the elliptical orifice.The wall roughness has an inhibitory effect on the holes,and the super-cavitation of the equal-diameter nozzle holes is obvious.(2)Increasing the incident pressure enhances the turbulent flow energy in the orifice,and the pressure increases the flow energy of the elliptical orifice outlet to increase less.Increasing the internal pressure of the back pressure elliptical orifice will increase slightly.Increasing the roughness of the nozzle orifice is significantly enhanced.(3)Increasing the incident pressure can increase the outlet mass flow rate,and the positive cone and hyperbolic orifice have the largest mass flow rate.The increase in back pressure reduces the mass flow rate of the cone-shaped,elliptical,and equal-diameter orifices.The roughness flow rate of the tapered and hyperbolic nozzles is increased.Equal-diameter nozzles add roughness to increase mass flow rate.(4)The flow velocity in the hole increases as the incident pressure increases.The exit velocity: the elliptical orifice is the smallest,and the hyperbolic and positive cone orifices are the largest.The increase of back pressure reduces the flow velocity in the nozzle hole,and the outlet speed of the inverted cone type nozzle is the smallest under the large back pressure,and the positive cone type nozzle hole is the largest.The roughness is increased to significantly reduce the exit velocity of the equal diameter,inverted cone,and hyperbolic orifice.Elliptical orifices have a reduced roughness exit velocity.Based on the simulation calculation and result processing of the internal flow field of the variable section nozzle,the atomization of each nozzle of the nozzle was simulated.(1)The increase of inlet pressure can increase the spray penetration distance of each nozzle,and the spray SMD becomes smaller and smaller.The inlet pressure increases the positive taper type spray hole spray penetration distance;the reverse cone type and hyperbolic type nozzle hole atomization quality is the best.(2)The back pressure is increased,the spray penetration distance of each nozzle is reduced,the spray SMD is graduallyincreased,and the spray quality is decreased overall.The back pressure is increased,the spray width of the positive cone spray nozzle decreases linearly,and the penetration distance is the largest.The spray penetration distance of the inverted cone spray nozzle is the smallest;the reverse cone spray nozzle and the equal diameter spray nozzle atomization quality under high back pressure The drop is more,and the hyperbolic spray hole has the best atomization quality.(3)The wall surface of the nozzle is smoothed to increase the roughness,the spray penetration distance of each hole is reduced,and the spray SMD is reduced little.The rough wall surface can improve the atomization quality,but the effect is limited.