Fundamental Characteristics of Laser Breakdown Assisted Long Distance Discharge Ignition

Towards the realization of lean combustion, a new ignition method called laser breakdown-assisted long-distance discharge ignition (LBALDI) has been developed. This method is expected to realize volumetric ignition by extending the initial flame kernel via the generation of a long discharge, thereby improving the lean combustion limit. In this study, the fundamental characteristics of LBALDI such as the influence of fuel on the ignition of long discharge were investigated. Conventional spark ignition (SI) and LBALDI in which the electrode distances were 1 min and 8mm, respectively, were compared using a constant volume vessel with a window for flame imaging based on the schlieren method. It was determined that the extension in the ignition limit using LBALDI was more pronounced in a lean propane and rich methane premixture compared to a rich propane and lean methane premixture, respectively. These combinations correspond to premixtures with a Lewis number larger than unity for the deficient reactant. This behavior is attributed to the generation of large initial plasma for LBALDI compared to SI.