Experimental study on the ignition in a scramjet with a self-designed water plasma ignitor

In this paper, aiming at the problematic situation of igniting and improving combustion efficiency in a supersonic combustor , a self-designed water plasma ignitor is designed for ignition in supersonic combustors. For the self-designed water plasma ignitor, deionized water is selected as the coolant. During the ignitor operation, the water coolant cools the cathode and evaporates. Steam is ionized between the cathode and anode , generating a water plasma jet that is injected into the combustor for ignition. The self-designed ignitor has the advantages of long-time operation, repeatable startup, convenient coolant portability, and a low water consumption rate. The temperature of the water plasma jet exceeds 3500 K. The calculation of ignition delay time indicates that OH, H, and other free radicals in water plasma can significantly shorten the ignition delay time of kerosene and extend the ignition equivalence ratio limitation. The ignition experimental study was conducted using the water plasma ignitor in a thin strut equipped supersonic combustor whose design point corresponds to the cruise condition at a Mach number of 6. In the ignition experiment, a flame, which is self-sustaining, was established after the ignitor was activated for approximately 682 ms. The feasibility of the water plasma ignitor in a supersonic combustor has been verified. • A novel water plasma ignitor for a supersonic combustor was designed. • The ignitor operational characteristics and ignition feasibility were experimentally validated. • The development characteristics, OH distribution, and composition of water plasma jets were explored. • The effect of water plasma components on ignition delay time and ignition limits of kerosene was analyzed.