| Spray structure and its spatial distribution have a significant influence on the combustion and emission characteristics of diesel engine. Spray impingement phenomenon has been one of the focus of the internal combustion engine research. In recent years, many combustion systems used spray impingement to optimize the mixture formation was developed. Based on the perspective of reducing the spray liquid core volume and improving spray spatial distribution, this paper explores the effect of spray impingement in ultra-near wall on fuel spray spatial distribution structure and atomization by using the three CFD simulation analysis software Star-CD.Firstly, the simplified model of ultra-near wall spray impingement is established The simulation research about the characteristics of spray impingement under different incident angels, different nozzle hole diameters and different back pressure is carried out using Star-CD software. The results show that the penetration distance increases with reduction of the incident angle and decreases as the nozzle hole diameter increases. With the increasing of ambient temperature and back pressure, the penetration distance and the maximum velocity along the wall decrease.Secondly, based on the idea of the geometry of the surface of the impact, the model of multi-piece orientation sleeve and the multi-prismatic orientation sleeve is established respectively. The comparison between simulation results of the two orientation sleeve and the free spray is carried out.It turned out that:(1) Spray divergence angle of free spray is small, which results the fuel distribution is relatively concentrated and the air entrainment quantity is small. At the same time, the liquid core located in the center of the spray is not destroyed, so the atomization effect is worse. There are large-diameter droplet both around root and head of the spray.(2)Compared to free spray, the penetration of multi-piece spray is decrease while the spray divergence angle, maximum width and the spread area are all increase. Because the liquid core is destroyed, the distribution range of multi-piece spray is widespread. However, there are still large-diameter droplet around root and head of the spray.(3)Penetration of the multi-prismatic spray decreases further. Due to the impact to orientation edge, the spray split into two bunch of spray, which results the increase of spray divergence angle and spray maximum width.However, because of the loss of penetration, the spread area of the multi-prismatic spray shows a little change. The droplets atomization effect of multi-prismatic spray is favorable, and the distribution of droplets is homogenous. The large-diameter droplets only located around the root of multi-prismatic spray. |
