Flame stabilization modes in a cavity-based scramjet combustor with different fuel injection ratios
Weiguang Cai, Shu Zheng, Jiajian Zhu, Zhao Li, Ran Sui, Qiang Lu
Abstract
The impact of the upstream and downstream fuel injection ratio on the flame stabilization combustion modes in a cavity-based scramjet was investigated. Three different injection schemes with global equivalence ratio of 0.73 were comparatively researched. The kerosene injection ratios in upstream and downstream regions were 3:1, 1:1, and 1:4. Three typical flame stabilization modes and a transition combustion mode were identified by using multispectral imaging, high-speed framing of CH* chemiluminescence, and wall pressure measurement. The experimental results showed that the cavity shear layer stabilization mode occurred in a combustor with 75% fuel upstream injection ratio. When the fuel upstream and downstream injection ratio was 1:1, the cavity-jet-wake stabilization mode and cavity-assisted shear layer-jet-wake stabilization mode occurred alternately. The proportion of stable combustion area increased by 43.36% and 35.87% compared with the fuel upstream injection ratio of 75% and 20%, respectively. The peak CH* signal region with cavity-jet-wake stabilization mode occurred at the slope of the back edge of cavity and the downstream platform of the cavity. The peak CH* signal region with the cavity-assisted shear layer-jet-wake stabilization mode occurred simultaneously at the shear layer and the slope of the back edge of cavity. With decrease in the fuel upstream injection ratio to 20%, the flame stabilized in the jet-wake. The time-resolved flame temperatures in the case when fuel was injected equally in the upstream and downstream regions were 45 and 221 K higher than those in the cases with ratios of 3:1 and 1:4. The cavity-jet-wake stabilization mode was more beneficial to the operation of the scramjet engine.