Simulation of mild auto-ignition initiated by a hot spot

Abstract

Mild auto-ignition initiated by a hot spot in the unburnt gas ahead of a lean hydrogen-air flame is studied using onedimensional (1D) direct numerical simulation (DNS). The impact of thermal boundary layer thickness and position of the hot spot on pressure oscillations in the domain as well as on the wall heat flux is investigated. The interaction of the sparkignited flame with the auto-ignitive front generated from the hot spot produces large pressure oscillations in the domain. A significant increase in the wall heat flux is observed when the autoignitive front quenches at the wall. The thermal boundary layer thickness has a negligible impact on these phenomena for the studied flames. Furthermore, the pressure oscillations appear only resulting in the fluctuations of the wall heat flux, and the significant increase in the wall heat flux appears primarily due to the quenching of the auto-ignitive front at the wall.