Studying Piston Cavity Geometry Effect on Direct Injection Diesel Engine Performance and Emissions with Numerical Simulation

Increasing environmental concerns in recent decades has caused a significant attention to pollutants emission and the ways to control them. Piston cavity diameter and dept effects on direct injection diesel engine performance and emissions were studied in this research. AVL FIRE 3D CFD software was used for engine cycle simulation in this studying. By applying the combustion, turbulence and pollution equations, the direct injection diesel engine closed cycle has simulated numerically. After mesh independency analyzing and simulation results validation with experimental data, the engine simulation was done for four different piston bowl geometries and the results such as incylinder pressure, heat release rate, temperature and emissions. Then the results were compared for all geometries. The results shown that there is less wet wall for geometry 4 that has large diameter and low dept and it can be concluded that incylinder mixing process and combustion for this geometry is better and it has good performance and low emission in comparison to other one. Also the results shown that nitrogen oxide emission reduced by reducing the diameter and increasing the depth of the piston bowl, but it increase unburned hydrocarbons, carbon monoxide and soot emissions.