Abstract
In this paper, the results gained by applying various impingement models to the cylinder and flat plate were analyzed in comparison with the experimental data to study spray/wall interaction phenomena.
In the present calculation, to begin with, the behavior of spray injected normally to the wall was analyzed using three different impingement models ; Naber and Reitz model (NR model), Watkins and Wang model (WW model) and Park and Watkins model (PW model). The results obtained from these models were compared with experimental data from Katsura et al. The results indicated that PW model was in better agreement with experimental data than the NR and WW models.
Also, for spray injected at 30deg, the result of three models were compared with experimental data from Fujimoto et al. The results showed that the NR model over-predicted the penetration in the radial direction because this model was based on the inviscid jet analogy. The WW model did not predict the radius and height of the wall spray effectively. It might be thought that this discrepancy was due to the lack of consideration of spray film velocity occurred at impingement site. The result of the PW model agreed with the experimental data as time elapsed. In particular, a height of the spray droplets was predicted more closely to the experimental data than the other two models. The results of the PW model in which the spray droplets were distributed densely around the edge of droplet distribution shaped in a circle had an agreement with the experimental data of Fujimoto et al. Therefore, it was concluded that the PW model performed better than the NR and WW models for predi! ction of spray behavior.
The numerical calculation using the PW model performed to the cylinder similar to the real shape of DI engine. The results showed that vortex strength near the wall in the cylinder was stronger than that in the case of flat plate. Contrary to the flat plat, an existence of the side wall in the cylinder caused the tangential velocity component to be reduced and the normal velocity component to be increased.
The flow tends to rotate the inside of cylinder going upward to the right side wall of cylinder gradually as time passes. Also, the results showed that as the spray angle increases, the gas velocity distribution and the tumble flow seemed to be formed widely. It was concluded that an increase in the tumble flow and the size of vortex causes the spray droplets and the gas flow to be mixed strongly.