Enhancement of blowout limit in a Mach 2.92 cavity-based scramjet combustor by a gliding arc discharge

Plasma-assisted combustion (PAC) has shown excellent performance in the ignition and combustion en-hancement of scramjet combustors. A multi-channel gliding arc (MCGA) plasma placed on the sidewall surface of a scramjet combustor was employed to enhance combustion near the flame blowout limit (BL) in a C2H4-fueled and cavity-based model scramjet combustor. Wall static pressure measurements, simultaneous 10 kHz CH * chemiluminescence imaging from the top and side views, optical emission spectroscopy, and dis-charge waveform measurements were used to elucidate the combustion physics throughout the PAC events. For the current cavity configuration and fueling condition, a general estimate of the flame BL in a rich-fuel environment was provided, in which a fuel flow rate (FFR) was 7.5 g/s. Once the FFR was exceeded, the flame was unstable and blown out, whereas the MCGA plasma demonstrated an excellent flame stabilization ability. The flame BL of the scramjet combustor in the presence of the MCGA plasma has an increase of & SIM;29%. Two PAC processes, including enhancement mode and re-ignition mode, were distinguished to play a vital role in extending the flame BL. The two PAC processes showed that the spark-type discharge generated by the MCGA could ignite the local fuel-rich mixture and increase the flame BL. The local ignition is dom-inated by the continuous accumulation of the massive flame kernels with the local fuel-rich mixture, as well as more heat and species exchanges.& COPY; 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.