DEVELOPMENT OF A HYBRID LAGRANGIAN-EULERIAN MODEL TO DESCRIBE SPARK-IGNITION PROCESSES AT ENGINE-LIKE TURBULENT FLOW CONDITIONS

摘要

With the engine technology moving towards more challenging (highly dilute and boosted) operation, spark-ignition processes play a key role in determining flame propagation and completeness of the combustion process. On the computational side, there is plenty of spark-ignition models available in literature and validated under conventional, stoichiometric SI operation. Nevertheless, these models need to be expanded and developed on more physical grounds since at challenging operation they are not truly predictive. This paper reports on the development of a dedicated model for the spark-ignition event at non-quiescent, engine-like conditions, performed in the commercial CFD code CONVERGE. The developed methodology leverages previous findings that have expanded the use and improved the accuracy of Eulerian-type energy deposition models. In this work, the Eulerian energy deposition is coupled at every computational time-step with a Lagrangian-type evolution of the spark channel. Typical features such as spark channel elongation, stretch, attachment to the electrodes are properly described to deliver realistic energy deposition along the channel during the entire ignition process. The numerical results are validated against schlieren images from an optical constant volume chamber and show the improvement in the simulation of the spark channel during the entire ignition event, with respect to the most commonly used energy deposition approach. Further development pathways are discussed to provide more physics-based features from the developed ignition model in the future.