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Research studies have suggested that changes to the ignition system are required to generate a more robust flame kernel in order to secure the ignition process for the future advanced high efficiency spark-ignition (SI) engines. In a typical inductive ignition system, the spark discharge is initiated by a transient high-power electrical breakdown and sustained by a relatively low-power glow process. The electrical breakdown is characterized as a capacitive discharge process with a small quantity of energy coming mainly from the gap parasitic capacitor. Enhancement of the breakdown is a potential avenue effectively for extending the lean limit of SI engine. In this work, the effect of high-power capacitive spark discharge on the early flame kernel growth of premixed methane-air mixtures is investigated through electrical probing and optical diagnosis.

The present work investigates the efficacy of distributed electrical discharge to increase the ignition volume by means of multipole spark discharge and radio frequency (RF) corona discharge. A range of ignition strategies are implemented to evaluate the efficacy of distributed ignition. The multipole spark igniter design has multiple high-voltage electrodes in close proximity to each other. This distributed spark ignition concept has the ability to generate multiple flame kernels either simultaneously or in a staggered mode. A novel elastic breakdown ignition strategy in responsive distribution (eBIRD) high frequency discharge is also implemented via the multipole igniter. The RF corona discharge is generated through an in-house developed ignition system. A form of distributed ignition is initiated along the streamer filaments.