COMPARISONS OF COMPUTED AND MEASURED PREMIXED CHARGE ENGINE COMBUSTION

Comparisons are presented of computed and measured cylinder pressure in a reciprocating engine with a pancake combustion chamber and premixed propane/air charges. Engine operating conditions range over volumetric efficiency of 30-60%; equivalence ratio of 0. 87-1. 1; and rpm of 1000-1500. The computations start from the actual spark times and simulate the growth of the flame kernel into a fully developed turbulent flame by taking into account the increasing influence of turbulent eddies on the growing flame kernel. A k- epsilon submodel is used for turbulence. The species conversion submodel assumes that the species (C//3H//8, O//2, H//2O, CO//2, CO, H//2, and N//2) concentrations approach their local thermodynamic equilibrium values with a characteristic conversion time that is a combination of a turbulent mixing time and a chemical conversion time in laminar propane-air flames.