燃油喷雾撞击高温壁面的形态特征研究

The high reinforcement of internal combustion engine leads to the rise of wall temperature, and fuel spray impingement is inevitable. The impact of fuel spray on high temperature wall has an important effect on the formation of mixture, and then affects the combustion process and soot emission. In this paper, the morphological characteristics of diesel spray impinging on high temperature wall surface were studied by backlight method on flow constant volume vessel. The influences of injection pressure, background pressure and wall temperature on the spray characteristics of near wall surface were analyzed. The results show that: The higher the injection pressure is, the earlier the wall-jet vortex appears. Moreover, it has obvious promoting effect on the increase of spreading radius and entrainment height. Increasing background pressure leads to delay of spray impingement time. Both the spread radius and the entrainment height are decreasing. The influence of back pressure on the spread radius is greater than that on the entrainment height. The hotter the wall temperature, the earlier the wall-jet vortex appears. The spread radius and entrainment height of fuel spray impingement increase. But when the wall temperature reaches Leidenfrost temperature, wall heat transfer mode changes. The spread radius and entrainment height decrease suddenly. According to the concept of contribution index introduced, the research shows that the change of injection pressure has the largest contribution index to entrainment height. The empirical formulae of spreading radius and entrainment height under the wall temperature are fitted based on the research law.