Phenomenological 0-Dimensional Combustion Model for Spark-Ignition Natural Gas Engine Equipped with Pre-Chamber

摘要

3D CFD (Computational Fluid Dynamics) is widely used as a useful design tool because of its efficiency in engine development. In contrast, the computational time in 3D CFD with chemical reaction calculations is much longer than the 0D/1D CAD (Computer Aided Design) tools. Computational time reduction in engine combustion tools is necessary for more efficient engine development. The objective in this research is to develop a phenomenological 0D combustion model for a spark ignition engine. We especially focused on a spark ignition pre-chamber-type gas engine which has a spark plug in the pre-chamber. The combustion process in a pre-chambertype gas engine is complicated and difficult to be modeled. Therefore, in the presented work, the combustion process and heat release rate is analyzed in detail. The proposed methodology consists of three major processes. Firstly, turbulence in the pre-chamber is generated by compressed gas flow from the main chamber during the compression stroke. Secondly, the heat release rate generated by a torch jet which flows from the pre-chamber into the main chamber is modeled using gas jet theory. It describes gas entrainment flow around the nozzle. Thirdly, the heat release rate generated by flame propagation in the pre- and main chambers is modeled using the turbulent flame speed and flame surface area. Finally, the model is validated with available experimental data and good agreements with the measured heat release rate, and the cylinder pressure history was obtained. The calculation between intake valve closing timing and exhaust valve opening timing was finished in a few seconds. Our model greatly reduced the computational time compared to the 3D CFD combustion model.