Effect of air-assistant on ignition and flame-holding characteristics in a cavity-strut based combustor

Abstract

For promoting the expansion of pilot flame in high-subsonic flows, radial flame-holders are commonly introduced to combine with the pilot flame-holder, which may inversely bring about issues to the pilot ignition and flame stability. To simultaneously obtain satisfactory ignition and flame-propagation performance, a novel air-assistant design is proposed for the cavity-strut based combustor. Furthermore, comparison experiments are conducted under ambient pressure to investigate the influence of air-assistant on combustor characteristics. The discrepancies are experimentally explored in terms of lean ignition, blowout, and combustion characteristics in three cavity-based combustors accompanied with numerical flow fields. The results indicate that the air-assistant design can widen the ignitable space for ignition, extend the flammable Mach number, and decrease the lean ignition and blowout fuel/air ratio by 18.6% and 17.9% respectively. The air-assistant method can also accelerate the kernel generation and flamelet growth and suppress the flame quenching in the cavity-strut structure, which enhances the flame stability in either strut-stabilizing or cavity-stabilizing mechanism. The introduction of air-assistant regulates the flame structure and eventually increases the temperature rise of combustor by 250–350 K within the full range of operating fuel/air ratio. Moreover, the temperature distribution altered by air-assisting is more suitable for engineering combustors with higher requirements on circumferential flame propagation.