Analysis On The Flow In The Intersecting Hole Nozzle Of Diesel Engines

As the crisis of energy demand becomes globally and emission regulations for diesel engine becoming more seriously, it enhances the difficulty of development of the diesel engine. The diesel nozzle is the most important component of diesel injection system, as the last link of the injection process. The spray quality is largely determined by the performance of nozzle. It has important influence on the performance of the diesel engine. Fuel injection pressure takes more significant role in improving the effect of atomization quality, but high injection pressure often accompanies seal difficulty, increase of power consumption, the reduction of reliability. In order to solve these problems, the intersecting hole nozzle has been developed, according to adjust the geometric structure of diesel nozzle to improve atomization, burning and emissions under lower injection pressure.With the mixed multi-phase flow model of Eulerian and cavitation flow model, the gas and liquid two-phase flow in the intersecting hole nozzle was simulated. The influences of injection pressure, back pressure, cross angles nozzle, inlet rounded radius of nozzle orifice, geometry characteristics of children holes, the intersecting hole nozzle with disturbed area and dissymmetrical intersecting hole nozzle were analyzed. This study also analyze the influences of mass flow and averaged kinetic turbulent energy.The results show that the geometry of the intersecting hole nozzle restrain the cavity flow. Increasing the injection pressure and back pressure can improve turbulent kinetic energy of the nozzle exit, improve the atomization effect, and the former effects more apparently. Increasing the cross angle, the exit velocity of liquid fuel will decrease, we can design the reasonable penetration according to this principle and then to avoid the spray and the collision of cylinder wall and piston top. Inlet rounded radius of nozzle orifice can improve the stability of the flow in the hole. When the whole inlet circulation area is nearly to the exit circulation area, the cavitation will occur. With the disturbed area, it can increase the perturbation in the hole and change the distribution of exit turbulent kinetic energy, and then optimize the atomization effect. Although the dissymmetrical intersecting hole nozzle and symmetrical intersecting hole nozzle have similar fluent distribution rule, they have different magnitude.This study of intersecting hole nozzle simulation enrich the knowledge of the nozzle geometry structure which impacts on the internal flow characteristic, and it will be helpful for the new geometric structure design and the optimization of the nozzle hole.