Evaluation of the main operating parameters of a homogeneous charge compression ignition engine for performance optimization

Abstract

Homogeneous charge compression ignition engines require a smart control system to regulate the input quantities of the engine in various operational conditions. Achieving an optimum combustion needs an appropriate system response for different engine loads and speeds according to the power acquired from the engine, as well as the amounts of emissions present in the exhaust. Therefore, performing a set of experimental tests together with numerical simulations in a wide range of conditions facilitates calibration of the input parameters of the engine. In this study, the effects of the thermodynamic parameters and the thermokinetic parameters on the engine output in the preliminary design stage were obtained at different speeds to determine the optimum exhaust emissions, the optimum combustion timing and the ranges of misfiring and knock, using multiple-zone thermodynamic modelling. On the assumption that the simulation cycle is closed, the probability density function was used to determine the initial conditions for the temperature and the residual gas from the previous cycle mass distribution in each area inside the cylinder. The results obtained proved that the kinetic properties of the mixture due to the effects of the the air-to-fuel ratio, the percentage of exhaust gas recirculation and the percentage of reformer gas have dominant effects on the output in comparison with the thermodynamic parameters such as the intake pressure and the intake temperature. At low speeds, exhaust gas recirculation retards combustion and delays engine knock. At higher engine speeds, the reformer gas advances combustion and improves misfiring.