Numerical Evaluation of Spark Assisted Cold Idle Operation in a Heavy-Duty Gasoline Compression Ignition Engine 2021-01-0410

Gasoline compression ignition (GCI) has been shown to offer benefits in the NOx-soot tradeoff over conventional diesel combustion while still achieving high fuel efficiency. However, due to gasoline’s low reactivity, it is challenging for GCI to attain robust ignition and stable combustion under cold operating conditions. Building on previous work to evaluate glow plug-assisted GCI combustion at cold idle, this work evaluates the use of a spark plug to assist combustion. The closed-cycle 3-D CFD model was validated against GCI test results at a compression ratio of 17.3 during extended cold idle operation under laboratory-controlled conditions. A market representative, ethanol-free, gasoline (RON92, E0) was used in both the experiment and the numerical analysis. Spark-assisted simulations were performed by incorporating an ignition model with the spark energy required for stable combustion at cold start. We also investigated the effects of spark plug orientation and spark timing on cold start performance. In particular, the flow field and fuel-air mixture formation in the region around the spark plug gap were closely monitored and analyzed to understand the implications on ignition and the ensuing combustion process.