Characterization of the flow field and stratification effects of fuel spray in a visualization engine using DPIV and entropy analysis

The objective of this study was to analyze the spray characteristics according to the injection duration under ambient pressure conditions and the injection timing in the visualization engine. In order to investigate spray behavior, the spray velocity is obtained through the PIV method a useful optical diagnostics technology and the vorticity calculated from the spray velocity component. These results elucidated the relationship between vorticity and entropy which plays an important role in the diffusion process for early injection and the stratification process for late injection cases. In addition, the homogeneous diffusion rate of spray was quantified using the entropy analysis based on Boltzmann's statistical thermodynamics. Using these methods, it was found that the homogeneous mixture distribution is more effective as a momentum dissipation of surrounding air than that of the spray concentration to increase the injection timing. It is found that the homogenous diffusion rate increased as the injection timing moved to the early intake stroke process, and BTDC 60° was the most efficient injection timing for the stratified mixture formation during the compression stroke.