Development of a 0D/1D Model System for the Cycle-to-Cycle Variation of High Tumble Spark Ignition Engines

Due to increasingly strict emission regulations, the demand for internal combustion engine performance has enhanced. Combustion stability is one of the main research focuses due to its impacts on the emission level. Moreover, the combustion instability becomes more significant under the lean combustion concept, which is an essential direction of internal combustion engine development. The combustion instability is represented as the cycle-to-cycle variation. This paper presents a quasi-dimensional model system for predicting the cycle-to-cycle variation in 0D/1D simulation. The modeling is based on the cause-and-effect chain of cycle-to-cycle variation of spark ignition engines, which is established through the flow field analysis of large eddy simulation results [1]. In the model system, varying parameters are turbulent kinetic energy, the distribution of air-to-fuel equivalence ratio, and the in-cylinder velocity field. The model system considers both the global and the local variations at the spark plug and includes several sub-models. The start of cyclic variation, i.e., the tumble variation and its effect on turbulent intensity, are solved based on the quasi-dimensional Turbulence Model [2]. The standard deviation of the air-to-fuel equivalence ratio distribution in the cylinder is modeled by the quasi-dimensional Homogenization Model [3] and is used to indicate the variation range of local lambda at the spark plug. The Initial Flame Growth Model is developed to consider the effects of local flow conditions at the spark plug on the early flame kernel propagation. As a result, the model system can calculate multiple cycles for one operation point in 0D/1D simulation to represent the cycle-to-cycle variation of spark ignition engines.