An entrained-flow type plasma discharge device based on a triple-electrode structure for engine ignition in a supersonic airflow environment

Plasma ignition technology faces the challenge of reduced arc stability or even flameout in the supersonic airflow environment. Although plasma ignition technology has improved the physical and chemical processes of fuel through special electrical, thermal, and chemical effects during the discharge process, the poor stability of the discharge arc in the supersonic flow field and the coupling between discharge arc and flow field have yet to be completely understood, which limits its development. This paper proposes a plasma igniter with a composite configuration that combines triple-electrode collaborative operation and an entrained-flow device. Electric arc is generated in a supersonic environment through the combined effect of three electrodes, and the flow field distribution in the reflux zone is optimized by introducing an external supersonic airflow with an entrained-flow device, which significantly improves the ability of the arc to resist shear airflow force and enhances arc stability. A multimodal diagnostic approach, combining high-speed imaging, electrical parameter diagnostics, and numerical simulations, was employed to investigate the effects of electrode spacing, entrained-flow hole location, and internal/external airflow on discharge characteristics. Active control over arc length, morphology, and internal flow field structure of the igniter was achieved through coordinated optimization of electrode spacing and entrained-flow hole location. This significantly enhances the discharge arc-fuel mixing efficiency, which is critical for reliable ignition in extreme environments, such as supersonic combustors.