Numerical Simulation of Nonequilibrium Plasma-Assisted Ignition for Gasoline Engine

Lean combustion in gasoline engine can reduce nitrogen oxide emission and fuel consumption greatly. However, as the fuel-air ratio approaches the lean-burn limit, the energy required to initiate the combustion increases dramatically, and the flame propagation speed decreases substantially. To enhance the lean combustion and expand the lean-burn limit of a spark-ignition engine, a high-voltage nanosecond pulsed plasma is introduced to initiate the combustion of the engine. Discharge process and chemical reactions are calculated separately due to an essential difference in their timescales. The effect of discharge induced active particles on the ignition of the gasoline engine is studied, which shows that the ignition is primarily associated with the faster development of chain reaction due to O and O
₃
produced by the electron-impact dissociation in the discharge phase; these active particles can greatly shorten ignition delay time. The combustion enhancement for lean mixture is more pronounced than the stoichiometric gases, which indicates that the nonequilibrium plasma has a great potential to extend the lean-burn limit.