Zoom link: https://kaust.zoom.us/j/99385577571

Abstract

This dissertation investigates the characteristics of elongated spark discharge to extend lean limits and improve ignition kernel development in ultra-lean mixtures. The elongated spark concept—where a spark is generated at the shortest interelectrode gap and then elongated by an external force—achieves longer spark lengths at lower applied voltages.

Spark elongation was also investigated by adjusting the interelectrode gap in pin-to-pin and pin-to-disk electrical configurations. The interelectrode gap was systematically varied to investigate its influence on ignition performance. Results showed that increasing the interelectrode gap extended lean limits and accelerated ignition kernel development. For CH₄/air and C₃H₈/air mixtures with longer interelectrode gaps, a larger ignition kernel formed near the cathode due to spark-generated radicals (O, H, and OH) via electron impact reactions. High-speed jets enhanced spark elongation, facilitated flame propagation, and extended lean limits in pin-to-disk electrical configuration. These findings demonstrate fundamental knowledge for improving ignition systems under ultralean conditions, offering insights into practical applications for advanced ignition systems.

To develop a flexible ignition system from engine operating conditions, a magnetically rotating spark plug was introduced as a self-elongating ignition method. The spark is initially generated at the shortest gap and elongates along a slanted geometry due to the Lorentz force acting on the spark channel. Parametric studies were conducted to optimize the slanted geometry. The magnetically rotating spark successfully achieved a 12-mm spark length, resulting in an extended lean ignition limit.

Biography

Sun Ho Park obtained his BS and MS in Mechanical Engineering at Pukyong National University (South Korea). He joined the Plasma Assisted Combustion Laboratory at CERP in 2020 as a PhD student in Mechanical Engineering program in the PSE division. His current research focuses on the fundamental characteristics of elongated spark ignition.