Abstract Flame stabilization with cavity-strut injection of ethylene in a single-side expansion scramjet combustor is experimentally investigated in a Mach 2.1 supersonic flow. Two cavity geometries with different length-to-depth ratios of 3.2 and 4.5 and two injection schemes with different injection distances upstream the cavity are used to compare their combustion characteristics in this study. Flame dynamics with different cavity geometries and injection schemes are visualized comprehensively using high-speed imaging and static pressure measurements. Two different combustion stabilization modes are recognized, including the jet wake mode and the cavity shear layer mode. The transition process between the two modes is also observed in the experiments. Flame oscillations are often accompanied by the transition of the combustion modes. It is indicated that although increasing the cavity length-to-depth ratio can strengthen the exchange of momentum and heat to promote combustion, it also leads to intensified flame oscillations. When the injection distance upstream of the cavity increases, the flame oscillations become more intense, and the total heat release from the combustor decreases accordingly. In order to obtain a robust combustion process, it is suggested that the flame should be stabilized in the cavity shear layer mode and the mode transition should be suppressed to some extent.

中文翻译：

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不同腔长深比单侧膨胀超燃冲压燃烧室火焰稳定实验研究

摘要 在马赫 2.1 的超音速流动中，实验研究了单侧膨胀超燃冲压发动机燃烧室中腔撑杆喷射乙烯的火焰稳定。在本研究中，使用具有 3.2 和 4.5 不同长深比的两种空腔几何形状以及在空腔上游具有不同喷射距离的两种喷射方案来比较它们的燃烧特性。使用高速成像和静压测量全面可视化具有不同腔体几何形状和注入方案的火焰动力学。识别出两种不同的燃烧稳定模式，包括喷射尾流模式和腔体剪切层模式。实验中也观察到了两种模式之间的转变过程。火焰振荡通常伴随着燃烧模式的转变。结果表明，虽然增大空腔长深比可以加强动量和热量的交换以促进燃烧，但也会导致火焰振荡加剧。随着腔体上游喷射距离的增加，火焰振荡变得更加强烈，燃烧室的总放热量相应减少。为了获得稳健的燃烧过程，建议将火焰稳定在腔剪切层模式下，并在一定程度上抑制模式转变。燃烧室的总放热量相应减少。为了获得稳健的燃烧过程，建议将火焰稳定在腔剪切层模式下，并在一定程度上抑制模式转变。燃烧室的总放热量相应减少。为了获得稳健的燃烧过程，建议将火焰稳定在腔剪切层模式下，并在一定程度上抑制模式转变。