The structure analysis of diesel free spray with phase change~(Effect of viscosity change of vapor-phase fuel on the structure of diesel free spray)

In this study, the purpose is placed in analysis the structure of diesel spray and, especially, making clear the mixture formation process in the evaporative diesel spray. The liquid fuel was injected from a single-hole nozzle (1/d = 1.0 mm/0.2 mm) into a constant-volume vessel possessing phenomena visualization under high pressure and temperature field. As for measurement method, in order to investigate liquid and vapor-phase of injected spray, exciplex fluorescence method was applied in the evaporative fuel spray. And the interested view region in injected spray is the downstream spray. For the minute investigation of spray flow, the liquid and vapor-phase region is taken with 35 mm still camera and CCD camera, respectively. As a result, for the case of evaporative fuel spray, as the non-evaporating that, in the region of liquid-phase fuel, it could be found that there are very small droplets in the spray outside and larger droplets in the spray tip because of droplets classification effected by Stokes number(stk). And, in this study, from the 2- dimensional analysis results of heterogeneous distribution in inner spray, the 3-dimensional analysis was tried by using the setoff of incident laser beam from spray center axis. Finally, in order to quantify mixture state change of vapor- phase region of injected spray, in this study, image analysis was carried out based on the entropy of statistical thermodynamics.