The single-zone numerical model of homogeneous charge compression ignition engine performance

Abstract

Abstract.The single-zone model of methane-air mixture combustion in the Homogeneous Charge Compression Ignition engine was developed. First modeling efforts resulted in the selection of the detailed kinetic reaction mechanism, most appropriate for the conditions of the HCCI process. Then, the model was completed so as to simulate the performance of the fourstroke engine and was coupled by physically reasonable adjusting functions. Validation of calculations against experimental data showed acceptable agreement. IntroductionHomogeneous Charge Compression Ignition (HCCI) is currently under widespread investigation. To limit the speed of combustion, lean mixtures are used. If the mixture is too rich, the pressure rises too rapid and generates knock-related problems. On the other side, lean equivalence ratios of the fuel/air mixture inducted into the cylinder provide low nitric oxides (NO x ) and particulate emissions, low fuel consumption. The HCCI process seems promising when running the engine using gas as fuel, especially using natural gas.However, several problems with the HCCI combustion concept reappear throughout the majority of investigations -two combustion control aspects. First, the ignition event and the ignition timing are not controlled. Second, the rate of heat release is not controlled too. It occurs due to insufficient understanding of HCCI technology. In conjunction with extensive experimental researches, computational models provide a good basis for exploring the HCCI combustion phenomena. Yet a direct numerical simulation of fluid mechanics combined with the detailed chemical kinetic model is computationally complex. The typical method of the solution of the problem is simplification either in fluid mechanics or in the chemistry part of the model. An example of the latter approach is the singlezone model, developed in Volgograd State Technical University. The simulation of chemical kinetics is based on the law of mass action and the Arrhenius rate expression. This approach enables one to explore numerically the influence of the inlet air-fuel ratio, the initial mixture temperature and the incylinder pressure on the ignition timing that is directly dependent on the pre-flame chemical reactions.In this paper, we present the investigation arranged as follows. The first section is the development of the first stage of the ignition event model -self ignition in the constant volume adiabatic reactor. The results obtained made it possible to choose the most acceptable kinetic reaction mechanism of methane burning. The second section is the development of the one-zone numerical model of the HCCI running process incorporating the kinetic model mentioned above. The third -the analyses of the preliminary results of the study, related to the validation of the model predictions against