同向剪切气流对GDI发动机燃烧室壁面油膜的影响

Effects of Same Direction Shear Flow on Fuel Film of GDI Engine Combustion Chamber Wall

利用激光诱导荧光法(LIF)和数值模拟方法研究了GDI发动机中异型壁面油膜形成与演变过程机理。首先,在燃烧室模拟装置上利用LIF方法研究了气流运动对38°喷油条件下壁面油膜形成与演变过程的影响;随后,对壁面油膜的形成与演变过程进行了数值模拟。研究结果显示:静态喷油条件下,燃油自然蒸发对壁面油膜的弥散作用有限;38°侧向喷油时,在同向剪切气流作用下,壁面油膜厚度、油膜残存百分数随喷油过程的进行有明显的波动现象,并且随气流强度的增加,壁面油膜形成量减少幅度增加,说明同向剪切气流对减少油膜形成、促进油膜弥散具有重要作用。

The purpose of this paper is to use laser induced fluorescence （LIF） and numerical simulation method to study the mechanism of fuel film formation and evolution on GDI engine shaped wall. Firstly, in combustion chamber simulation device, the effect of air movement on the wall film formation and evolution under 38° injection conditions was studied using LIF. Subsequently, based on these simulation device and test conditions, the wall fuel film formation and evolution were studied using numerical simulation. Using 38°lateral fuel injection, under the action of same direction shear flow, the wall film thickness and the percentage residue of the film have a significant wave phenomena during the fuel injection process. Furthermore, with the increasing of flow intensity, the rate of reduction of the amount of fuel film formation increases. In conclusion, the results imply that the same direction shear flow plays an important role in the reduction of fuel film forma- tion and the improvement of fuel film diffusion.