Search Results

Computational Fluid Dynamics (CFD), as an effective analytical tool, has been applied at China North Engine Research Institute (CNERI) for combustion chamber design and combustion system optimization on a V8 heavy -duty diesel engine in order to meet increasingly stringent emission targets. The design of combustion system involves great number of parameteric optimizations such as the number of nozzle holes, the spray angle, the swirl ratio and the piston bowl shape. 3-D CFD was a convenient and cheap tool to explore the effects of all these parameters to the engine performance, compared with extensive hardware testing. 1-D modeling was used to set up boundary conditions at intake valve closure for 3-D CFD modeling during the closed-cycle. AVL FIRE software with a widely used combustion model, ECFM-3Z model, was used for 3-D simulation. Two sets of nozzle holes, four spray angles and three swirl levels were utilized and optimized under rated power.

Poppet-valve two-stroke gasoline engines can increase the specific power of their four-stroke counterparts with the same displacement and hence decrease fuel consumption. However, knock may occur at high loads. Therefore, the combustion with stratified lean mixture was proposed to decrease knock tendency and improve combustion stability in a poppet-valve two-stroke direct injection gasoline engine. The effect of intake pressure and split injection on fuel distribution, combustion and knock intensity in lean mixture conditions at high loads was simulated with a three-dimensional computational fluid dynamic software. Simulation results show that with the increase of intake pressure, the average fuel-air equivalent ratio in the cylinder decreases when the second injection ratio was fixed at 70% at a given amount of fuel in a cycle.