Analysis of turbulence in diesel spray using time-resolved PIV

A turbulent characteristic in diesel sprays were investigated to gain more insight into its effect on spray structure and microscopic mixing. Non-evaporating diesel sprays were injected into inert constant volume vessel. Time-resolved PIV technique using a combination of a high-speed video camera and a CW green laser was applied to investigate the velocity distribution in the sprays. Experiments were conducted for ambient density ranging from 10.0 kg/m³ to 30.0 kg/m³. Besides, fuel injection pressure representative of fuel injection pressure was changed from 40 to 140 MPa. The analyses of velocity field, vorticity and integral length scale showed that large scale vortices play a significant role in the formation of heterogeneous branch-like structure, but fuel injection pressure and ambient density give less impact on the macroscopic eddy scale and spray structure. Turbulent mixing on relatively-small scale was assessed based on the vorticity and turbulence intensity. The result demonstrated that streamwise velocity is one of the primary factors affecting the small-scale mixing.