Development of a zero-dimensional turbulence model for a spark ignition engine

The necessity for the use of one-dimensional simulation is growing because cost and time required for hardware optimization and optimal calibration of engines based on experiment are increasing dramatically as engines are equipped with growing numbers of technologies. For one-dimensional simulation results to be more reliable, the accuracy and applicability of the combustion model of a one-dimensional simulation tool must be guaranteed. Because the combustion process in a spark ignition engine is driven by the turbulence, many of existing models focus on the prediction of mean turbulence intensity. Although many successes in the previous models can be found, the previous models contain a large number of adjustable constants or require information supplemented from three-dimensional computational fluid dynamics simulation results. For improved applicability of a model, the number of adjustable constants and inputs to the model must be kept as small as possible. Thus, in this study, a new zero-dimensional (0D) turbulence model was proposed that requires information on the basic characteristics of the engine geometry and has only one adjustable constant. The model was developed based on the energy cascade model with additional consideration of following aspects: loss of kinetic energy during the intake stroke, the effect of piston motion during the compression and the expansion stroke, modifications to correlations for integral length scale, geometric length scale, and production rate of turbulent kinetic energy. An adjustable constant to consider engine design which determines tumble strength was also introduced. The comparison of the simulation results with those of three-dimensional computational fluid dynamics confirmed that the developed model can predict the mean turbulence intensity without case-dependent adjustment of the model constant.