One Step Reaction Rate Model for Application of HCCI Combustion on Energy Efficient and Environment Friendly Thermal Engines

摘要

To reduce the number of tests during engine tuning phases, a model with a very short computational time to simulate Diesel homogeneous combustion (Homogeneous Charge Compression Ignition HCCI) is needed. Therefore, the goal of this study is to provide the engine manufacturers with a simple physical combustion model to assist engine tuning and engine management system optimization, with the aim of predicting in-cylinder pressure evolutions and mean effective pressure (IMEP). A reduced model driven by to two state variables: the temperature and the mass fraction of burning fuel in the combustion chamber, is described in this paper. The chemistry is modeled by a global degradation reaction where the reaction rate coefficient, usually modeled through the Arrhenius law is driven in this approach by a global function Ω(T). This global function takes into account the slow dynamic of the cool flame and the fast dynamic of the main ignition and the transition between the two stages. A drawback of the global approach is the introduction of some new parameters which need to be correlated to give reliable results; this has required an important and large parametric study to calibrate the reaction rate coefficient. The proposed model validated for an engine running with premium diesel fuel is then autonomous, meaning that the model parameters are function of the engine operating conditions only. The results show that this type of model can be useful to describe the ignition delay time of HCCI combustion and the rate of heat release, with very short computational times around two seconds. Model against experimental data shows overall satisfactory agreements in terms of in-cylinder pressure and of mean effective pressure (IMEP).