自点火氢燃料超燃火焰形成与传播过程数值模拟及分析

Numerical Simulation on Flame Formation and Propagation of Hydrogen Fueled Scramjet with Auto-ignition

针对氢燃料超燃冲压发动机燃烧室内的燃烧细节,采用数值方法研究了喷注初期不同喷注位置及当量比下超燃燃烧室氢燃料自点火火焰形成与传播过程,结合OH、HO_(2)自由基与温度分布分析了点火燃烧过程的火焰精细流场结构。结果表明:凹腔下游喷孔距凹腔后缘较近时,若喷注压力超过2 MPa,会发生下游火焰通过回流区卷入凹腔的现象;凹腔内喷注会在凹腔剪切层前沿形成稳定反应面,造成反应区分离;喷注压力相同时,上游布置喷孔燃烧室出口氧耗率更高,总压恢复系数降低,而在喷注位置相同时,随喷注压力的升高,燃烧室出口氧耗率提高,总压恢复系数降低;喷注当量比不同会影响火焰的稳定位置与结构,在当量比较低时氢气燃烧主要发生在凹腔、剪切层及燃烧室下游,在当量比较高时则发生在燃烧室下游。

In response to combustion details of hydrogen fueled scramjet combustor,the numerical simulation method was used to investigate the formation and propagation of hydrogen flame with auto-ignition in a scramjet combustor with different injection positions and equivalence ratios during the initial injection stage.The fine flow field structure of flame in the ignition combustion process was analyzed by combination with the distribution of OH,HO_(2) radicals,and temperature.The results show that when the downstream nozzle of the cavity is close to the rear edge of the cavity,if the injection pressure exceeds 2 MPa,the downstream flame will be drawn into the cavity through the recirculation area;The arrangement of nozzle in the cavity will form a stable reaction surface at the front of the cavity shear layer,resulting in the separation of the reaction zone;With the injection pressure is the same and the nozzle is arranged upstream,the oxygen consumption rate at the outlet of the combustor will be higher and the total pressure recovery coefficient will be lower,while the injection position is the same,the oxygen consumption rate at the outlet of combustion chamber increases with the increase of injection pressure,and the total pressure recovery coefficient decreases;Different injection equivalence ratio will not affect the stable position and structure of the flame,with lower equivalence ratio,hydrogen combustion mainly occurs in the cavity,shear layer and downstream of the combustor,while with higher global equivalence ratio,it occurs downstream of the combustor.