Numerical research on micro diesel spray characteristics under ultra-high injection pressure by Large Eddy Simulation (LES)

Abstract

The Large Eddy Simulation model was introduced to study the micro spray characteristics under ultra-high injection pressure (>220MPa). EFS8400 spray test platform was set up to verify the accuracy of the numerical model. The mechanisms of micro spray characteristics were studied intensively under different injection pressures (180MPa, 240MPa) and nozzle diameters (0.1mm, 0.16mm). The results indicated that the micro turbulence vortex structures can be captured, especially in the liquid spray core area. Large Eddy Simulation model combined with the small grid size of 0.25mm show a huge advantage in studying the micro spray characteristics under ultra-high injection pressure; The turbulence vorticity and spray velocity for injection pressure of 240MPa are more intensive than that of 180MPa, and also the ultra-high injection pressure can contribute to strong turbulence disturbance between spray and surrounding air, which is helpful to improve the quality of spray; The spray velocity field extended wider for the diameter of 0.16mm, and also the values of velocity in the spray center is higher than that of the diameter of 0.1mm; The entrainment vortex appeared at the edge of the large velocity gradient between spray and surrounding air, and the higher velocity gradient for ultra-high injection pressure (240MPa) between the spray and air is easier to increase the generation of entrainment vortex in the downstream of the spray, which can significantly increase the quality of spray and atomization.