Multi-Dimensional Modeling of Turbulent Premixed Charge Combustion 920589
Existing models of combustion for multi-dimensional engine flow calculations have problems that limit their usefulness for investigating combustion dependent engine design issues. An alternative model has been formulated that is applicable to premixed charge combustion in engines. The model is robust enough to treat combustion in the bulk and near wall flow regions, and includes a mechanism for flame quenching at the wall. Combustion is represented in terms of separate entrainment and burn-up processes, which is similar to the two zone models commonly used in engine cycle simulations.
Calculations have been performed of one-dimensional radial flame propagation in a cylindrical chamber, which is initially filled with a homogeneous fuel-air mixture. Deficiencies in existing combustion models have been demonstrated for this case. The performance of the new combustion model was assessed by studying flame propagation over a range of initial gas conditions typical of engines. The results show that the model gives a physically plausible representation of flame behaviour for all conditions considered. Good agreement is obtained with engine measurements of flame speed. Flame quench distances are within the range expected to occur in engines, as given by prior experimental studies presented in the literature.
Further calculations were performed of two-dimensional flame propagation in a pancake geometry combustion chamber. Tangential quenching at the head and piston surfaces gives the flame front a concave shape as it progresses towards the liner. Overall, the calculations demonstrate that the new model shows great potential for providing an accurate representation of turbulent combustion in practical engine geometries. This provides motivation for future development and validation of the model.
