Effect of back pressure on the ignition delay period of a diesel spray impinging on a glow plug hot surface in a spherical combustion chamber

Ignition delay period (ID) is a key indicator for defining safe operating boundaries and evaluating combustion controllability during hot surface ignition. Back pressure is one of the most important parameters affecting the ID in hot surface ignition, and the rising back pressure shortens the ID. This study investigated diesel spray impingement ignition on a glow plug hot surface in a spherical combustion chamber with an exit channel. This study combined both experimental testing and three-dimensional numerical Large-eddy Simulations (LES) methods to investigate the diesel spray impingement ignition process on a glow plug hot surface under different back pressures. The results show that the ignition delay period of the hot surface ignition process was divided into three stages, i.e., flow, evaporation, and chemical stages, according to the local evolution of Reynolds number, evaporation rate, CH 2 O, and OH. When back pressure increased from 1 bar to 6 bar, ID duration decreased from 12.1 ms to 3.6 ms (reduction was 70.2% relative to the 1 bar). When back pressure increased from 1 to 9 bar, ID decreased to 2.9 ms (76.0% relative to the 1 bar). Furthermore, relative to the operation condition of back pressure = 1 bar, the chemical stage duration decreased by 85.2% at 6 bar and 88.9% at 9 bar. Meanwhile, both the flow and evaporation stages showed fewer reductions. Thus, the chemical stage causes the most important effect on the ID compared to other stages in the hot surface ignition process. Therefore, these results indicate that shortening the chemical stage is useful to reduce the ID duration and benefit the ignition process of the hot surface ignition.