Dual/scram-mode combustion limits of ethylene and surrogate endothermically-cracked hydrocarbon fuels at Mach 8 equivalent high-enthalpy conditions
Dual/scram-mode combustion limits of ethylene and surrogate endothermically-cracked hydrocarbon fuels at Mach 8 equivalent high-enthalpy conditions
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DOI：
10.1016/j.proci.2020.07.003
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发表时间：
2020-08
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影响因子：
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通讯作者：
Will O. Landsberg;Tristan Vanyai;T. Mcintyre;A. Veeraragavan
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作者：
Will O. Landsberg;Tristan Vanyai;T. Mcintyre;A. Veeraragavan
本文研究了在马赫数为8的超燃冲压发动机燃烧室中碳氢燃料的紧急停堆/双模态燃烧极限。飞行等效流通过反射激波风洞输送到轴对称空腔燃烧室。研究了两种超燃冲压发动机燃料：乙烯和代表吸热裂解正十二烷的替代混合物。燃烧模式进行了检查，通过静压传感器，并通过化学发光成像，平面激光诱导荧光（PLIF）的OH燃烧自由基在燃烧室排气羽流。乙烯燃料的实验发展了在减少燃料条件下的超燃冲压模式燃烧，经历了激波占主导地位的流场。OH PLIF诊断表明，这种燃烧模式形成了燃烧产物的环状结构，主要是轴对称地靠近燃烧室壁。增加燃料锚定燃烧下游的燃料喷射器，同时进一步增加煽动双模式燃烧。在这种模式下，亚音速燃烧区联合收割机与超音速核心回流相结合，以允许在遇到显著增加的压力的情况下向上游传送信息。光学诊断表明，广泛的不对称，不稳定的燃烧功能。代表吸热裂解的正十二烷的替代混合物经历了从无燃烧（光学确认）到在临界加燃料速率下充分发展的双模燃烧的快速开始。OH PLIF信号和化学发光的这种燃料是弱于可比的乙烯的情况下，表明潜在的燃烧途径的差异。
This paper examines the scram/dual-mode combustion limits of hydrocabon fuels within a Mach 8, scramjet combustor. Flight-equivalent flows were delivered to the axisymmetric, cavity combustor via a reflected shock tunnel. Two scramjet fuels were examined: ethylene and a surrogate mixture representing endothermically cracked n-dodecane. Combustion modes were examined via static pressure sensors and through both chemiluminescence imaging, and planar laser induced fluorescence (PLIF) of the OH combustion radical in the combustor exhaust plume. Ethylene-fuelled experiments developed scram-mode combustion under reduced fuelling conditions, experiencing shock wave dominated flowfields. OH PLIF diagnostics indicated such combustion modes developed a ring-like structure of combustion products, primarily axisymmetrically adjacent to the combustor wall. Increased fuelling anchored combustion downstream of the fuel injector, while further increases instigated dual-mode combustion. In this mode, subsonic combustion regions combine with the supersonic coreflow to permit the transfer of information upstream with substantially increased pressure encountered. Optical diagnostics indicate broadly asymmetric, unsteady combustion features. The surrogate mixture representing endothermically cracked n-dodecane experienced rapid onset from no-combustion (optically confirmed) to fully developed dual-mode combustion at critical fuelling rates. OH PLIF signals and chemiluminescence of this fuel were weaker than comparable ethylene cases, indicating potential differences in combustion pathways.