LDA Analysis of High Injection Pressure Diesel Fuel Spray and Entrainment Air Flow

Droplet velocities in a diesel fuel spray before and after impinging on a wall as well as air movement around the spray are measured at room temperature and pressure. The range of fuel injection pressure is from 101 MPa to 139 MPa. The diagnostic equipment is a Laser Doppler Velocimetry with Burst Spectrum Analyzer (LDV-BSA).The results show that the droplet velocities of such a high pressure diesel fuel spray spread in a wide range (about 0-250m/s), so it is necessary to use the ensemble average for describing the velocity variation with time and space. After injection, the velocity reaches its peak value rapidly then attenuates gradually. When the spray impinges on the wall, the average velocity of the rebounded droplets is obviously reduced and the rebounded angle of most droplets is smaller than 30 degree when the incident angle is 70 degree. In the near field zone, the air entrainment in spray jet appears to be lower than that in gaseous one.