Experimental Study Of The Diesel Spray Impingement On Liquid Film

The early injection method has gradually become a hot topic among the advanced diesel combustion technologies, which plays an important role in improving the mixture process of the fuel and air. However, it is the decreasing of the cylinder pressure that leads to the impingement of the spray on the combustion chamber or the liner, increasing the emission of the unburned hydrocarbon(HC) and particulate matter. On one hand, the splashed lubricant caused by the impingement may mix with the fuel and be burned in the combustion chamber, which can change the combustion process and emission results. What's more, the deposited fuel on the liner can be delivered to the crankcase so as to dilute the oil, influencing the lubricity of the lubricant. By now, most research is concentrating on the impingement between the single, multiple droplets or the spray on the dry wall or the fuel film. Little study has been done on the interaction between the spray and lubricant film. In this paper, the main work consists of the construction of the spray impingement test rig, the atomization of the spray impingement research and the impingement between the spray and the dry wall, lubricant film and the diesel film under different working conditions.The spray impingement test rig in this paper is made up of the constant combustion chamber, fuel injection system, temperature and pressure control system, ECU system and the image acquisition system. Various parameters, such as the environmental pressure, environmental temperature, injection pressure, injection distance, impingement angle are all can be simulated and researched.The experimental spray atomization research was mainly done with the help of the high speed camera under different injection pressure, environmental pressure and impingement angle. The analysis can be done from the perspective of the dispersion diameter and entrainment height with the help of Image-Pro Plus and Matlab. According to the research results, the increasing environmental pressure can reduce the spray penetration distance on one side. However, the dispersion diameter and entrainment height under the lower environmental pressure is larger. Besides, the higher injection pressure can advance earlier impingement, while the high kinetic energy is beneficial for the atomization. Finally, the smaller impingement angle means better atomization.Finally, the impingement results of the spray on dry wall, lubricant film and diesel film have been researched and analyzed from the perspective of deposited fuel mass and the contour of the wall film thickness. According to the final results, more fuel adhered to the wall when spray impacts the dry wall, instead of the lubricant film. Besides, there is less fuel on the wall when the wall is inclined. The contour of the post-impingement film varies among the different wall conditions. When the spray impingements on the lubricant the shape of the film is more like a bowl. On the other hand, the results of the impingement on the dry wall are generally like a high boss. The results can be slightly different under different conditions.