Numerical simulation of the effects of combustion chamber geometry on nonroad diesel engine performance

Abstract

Combustion chamber geometry is very important for the performance of diesel engine, especially for the nonroad diesel engine with low fuel injection pressure. To decrease the experimental work, the CAE technique, such as computational fluid dynamics (CFD), was used to design the combustion chamber of a nonroad diesel engine. In order to investigate the effects of combustion chamber geometry on mixture formation and combustion quality and then choose a relatively better combustion chamber design scheme, many combustion chambers with different shapes at a constant compression ratio are designed and numerically investigated by CFD simulation. In this paper, three typical combustion chamber shapes were exhibited. The simulation results show that combustion quality is significantly affected by the reentrant diameter and transition radius in dumbbell-shaped combustion chamber of nonroad diesel engine. The obvious wall impingement of fuel spray occurs in combustion chamber with a smaller diameter/depth ratio, which leads to uneven air-fuel mixture and some fuel-dense regions. There exists an optimum chamber B, which possesses a better swirl intensity retention, stronger squish and higher turbulence kinetic energy, contributing to a better combustion situation and a good compromise between the soot and NOx emissions. Engine experiment valid the result.