Promoting Jet-Induced Detonation Initiation via Electrode Breakdown Discharge

The initiation of detonation is a critical yet challenging task for pulse and rotating detonation engines. Conventional approaches often rely on nanosecond repetitively pulsed discharges to generate nonequilibrium plasma for ignition assistance, but the complexity and high cost of the required power supplies limit practical applications. In this work, we experimentally investigate a simplified method using ordinary electrode breakdown discharge to produce an arc plasma that promotes jet-induced detonation initiation. Two ignition strategies are compared under the same total energy: dual-spark-plug ignition (energy concentrated at the jet tube head) and single-spark-plug coupled with electrode discharge (energy split between the jet tube head and an electrode pair placed near the detonation chamber inlet). High-speed schlieren measurements are performed to capture the dynamic flame evolution and shock wave structures. The results show that the electrode-discharge approach dramatically increases the detonation success rate from 13.33% to 66.67% over 30 repeated runs. The electrode discharge is found to occur after the emerging flame has already covered the electrodes. Therefore, the promoting mechanism is attributed not to the high temperature or free radicals generated in the already-burned products, but rather to the discharge-induced shock wave. This shock wave interacts with the corner expansion waves generated by the sudden area expansion, thereby delaying the unsteady decay of the leading shock and promoting re-initiation. This study provides the first experimental evidence that ordinary electrode breakdown discharge promotes jet-induced detonation via a shock-wave reinforcement mechanism. The findings enable a low-cost, compact plasma-assisted initiation strategy for practical detonation engines.