RESUMO

High pressure and split fuel injection have been equipped commonly in DI (direct injection) diesel engines, and fuel impingement to the combustion wall becomes a major spray behavior for controlling engine performance. However, there is little information concerning the velocity field of postimpingement spray. In this study, the velocity field of an impingement diesel spray was measured with time-resolved particle image velocimetry (PIV). To obtain a two-dimensional tomographic image, diesel spray was impinged to a slender bar instead of a flat wall. As a result, velocity distribution of the impingement diesel spray in time series was obtained for various impingement angles. According to sequential tomographic images of the postimpingement spray, a high-density spray cloud rolled up inside the postimpingement spray. It was caused by secondary breakup of the liquid film on the wall. By analyzing the mean velocity field of the postimpingement spray, substantial impingement mass seems to decrease with an increase of the inclination angle of the impingement disk. Moreover, it was found that there was high velocity and a low-turbulence sublayer near the wall in the postimpingement spray.