氢气引导乙烯火焰非定常燃烧过程

基于脉冲燃烧直连式试验台，开展了超燃冲压发动机氢气引导乙烯火焰的非定常燃烧过程研究。燃烧室入口条件为马赫数2、总温950 K和总压1.0 MPa。试验过程分为4个阶段：冷流、引导氢气单独燃烧、引导氢气点燃乙烯、乙烯单独燃烧。基于高频壁面压力测量和火焰荧光高速摄影，获得了代表性测点的压力时间曲线及燃烧室内火焰发展历程，提取了压力平均值、振荡幅度和频率、着火时间及反应位置等重要信息，分析了不同燃烧阶段的非定常特性。试验结果表明：在氢气单独燃烧阶段，非定常特性源于凹槽后斜坡区域氢气反应强度的变化。在氢气点燃乙烯阶段，非定常特性由氢气和乙烯火焰的“交接”引起。在乙烯单独燃烧阶段，非定常特性由燃烧和超声速流动之间的耦合引起。

Unsteady combustion process of ethylene flame with pilot hydrogen

Unsteady supersonic combustion process of hydrogen piloted ethylene flame in a scramjet combustor was carried out based on a direct-connected facility. The results were obtained under the inflow conditions of Mach number 2, total temperature 950 K and total pressure 1.0 MPa respectively. Ambient ethylene was used as the main fuel and ignited by pilot hydrogen. The whole experimental process could be divided into four periods: cold flow without combustion, hydrogen combustion alone, ethylene igniting by hydrogen, ethylene combustion alone. The curves of wall pressure with time and combustion development processes at five important locations in the combustor were gained through high frequency pressure transducers and flame photographs. Some insight information, including the wall pressure average value, oscillation extent and frequency, ignition time and location, were picked out. Then the unsteady combustion characteristics in different periods were analyzed and discussed. The unsteadiness came from the change of acting intensity at cavity aft-step in period of hydrogen combustion alone. The transfer between hydrogen and ethylene produced unsteady combustion in period of ethylene igniting by hydrogen. In period of ethylene combustion alone, the unsteadiness emerged from the coupling of flow and combustion.