Squish effect of piston crown on the turbulent heat transfer in reciprocating engine

An axisymmetric two-dimensional computer program employing the Large Eddy Simulation (LES) and SIMPLE-C method coupled with preconditioned conjugate gradient methods is applied to the turbulent flows in the compression-expansion strokes for various combustion chamber geometries under realistic engine conditions. The squish area percent of piston crown is changed (SQ = 0 percent for flat piston model, SQ = 46 percent for shallow bowl piston model and SQ = 76 percent for deep bowl piston model) under engine speeds (500 to approximately 1,500 rpm) for the purpose of investigating the heat transfer performance. Comparison was made of present heat flux results and earlier experimental and numerical results. It is shown that the numerical method can predict the turbulence with reasonable accuracy. The results show that the configuration of piston crown for squish area percent can obviously enlarge the surface heat flux of wall boundaries in reciprocating engines.