Abstract:

In this paper， the turbulent flame propagation speed model is used to describe spark ignition （SI） combustion. For a single self-ignition point， the turbulent flame propagation speed model is still used， the sum of the equivalent turbulent flame speed of all self-ignition points is considered as the total equivalent turbulent flame speed， which is used to describe compression ignition combustion and then a spark-assisted compression ignition （SACI） quasi-dimensional combustion model is established. The air and external exhaust gas recirculation （EGR） dilution SACI based on this model is studied， and the simulation and experimental results match well. The calculation shows that the flame propagation speed of SACI is higher than that of SI， which increases with ignition advanced.， with the flame propagation speed of external EGR dilution lower than that of air dilution. Delaying ignition or increasing external EGR can lead to an increase in the peak area of the flame front， a slowing down of the decay rate and a weakening of the isovolumetric combustion. The thermal efficiency of air dilution is higher when the dilution ratio is comparable， but the exhaust aftertreatment of external EGR dilution is easier.

Key words: spark-assisted compression ignition （SACI）, turbulent flame propagation speed model, spark-assisted compression ignition quasi-dimensional combustion model, total equivalent turbulent flame speed, external exhaust gas recirculation