Study On Spray Characteristics Of GDI Injector Fueled With Ethanol Under Ultra-high Injection Pressure

With the rapidly growing issue of air pollution,limitations on the kinds and the amounts of pollutants that cars may give off are becoming stricter.This is obviously a challenging time for gasoline direct injection?GDI?engines to cut down the emission sources of pollutants.Ultra-high pressure injection and using ethanol are considered as important technical routes,and it is necessary to systematically study the development,fragmentation and atomization of the spray under ultra-high injection pressure,so as to explore the potential of this new technology.This paper analyzed the macroscopic and microscopic characteristics of ethanol spray of GDI injector under 100 bar to 600 bar injection pressure by using schlieren testing system,phase Doppler analyzer?PDA?and AVL FIRE.As injection pressure increased,so did the penetration distance of SW region,SC region and R_penetraion value.Under ultra-high injection pressure,due to severe disturbance,the oil beam was circular passivated,the penetration growth rate significantly reduced when injection pressure continued to rise.Ultra-high injection pressure will not significantly increase fuel impingement.However,the wet wall phenomenon can get worse when impingement happens.R_area value can be reduced and the distribution of ethanol spray can be improved under ultra-high injection pressure.The particle velocity became larger,and the spray motion diffusion enhanced as injection pressure increased.Serious particle deformation in spray head caused PDA measurement regional gap under ultra-high injection pressure.The number of particles in Sheet stripping region can be increased effectively,so did wave crest stripping region and Catastrophic region,it also promoted the breakup of large size droplets and increased the proportion of small droplets.That maximum frequency range of particle size was 4-6?m,showed ultra-high pressure injection could limit further fragmentation of small droplets which particle size below 8?m.When the longitudinal distance of spray measurement position increased,D32 showed an increasing trend.When the transverse distance between the measuring positions increased,the droplet size increased,the velocity component in the LDA1 direction decreased greatly,and the LDA4 direction velocity component increased.The spray simulation model was established by AVL FIRE software,and the accuracy of the model was verified based on the test results.Simulation results showed the rangeability of droplet LDA1 measured in the spray head area was smaller than that of the microscopic test result,which indicated that the PDA system cannot measure the non-spherical droplets in the spray head accurately,which will cause some errors to the measurement results.Along with the spray development,the droplets in the front of spray will appear small droplets mass.With the injection pressure increased,the proportion of the area of small droplets mass became larger,which increased interfacial area.In a word,ultra-high pressure GDI injector can effectively accelerate the crushing of ethanol spray,inhibit the formation of large particle droplets,increase the proportion of ethanol fuel evaporation,and improve the quality of mixed gas.