Further Comparisons of Computed and Measured Divided-Chamber Engine Combustion

Combustion in a divided-chamber, stratified-charge engine is considered and flame and pressure results obtained with a two-dimensional, unsteady model are compared with corresponding engine data. The model is applied to eight engine conditions differing in speed, load and size of the prechamber orifice. The model employs one overall chemical reaction rate, the k-ε representation of turbulence, and a wall heat loss proportional to the heat release. The computed results are shown to be in good agreement with the experimental ones in spite of the complexity of the problem and the early stages of detailed model validation studies. They are also shown to compare somewhat better than earlier ones obtained with an ad-hoc jet turbulence model. Both studies prove the importance of the prechamber jet to the overall combustion process for the particular engine investigated. Since divided chamber configurations are considerably more complex than open chamber ones, the model should be applicable to a variety of engine designs. Current and past experience indicates the model should be particularly useful in combustion optimization studies, during engine development, as a means to interpret and extrapolate engine test data.