On the Behavior of a Shear-Coaxial Jet, Spanning Sub- to Supercritical Pressures, with and without an Externally Imposed Transverse Acoustic Field
On the Behavior of a Shear-Coaxial Jet, Spanning Sub- to Supercritical Pressures, with and without an Externally Imposed Transverse Acoustic Field
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关于剪切同轴射流的行为，跨越亚临界压力，有和没有外部施加横向声场
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
D. Davis
中科院分区：
文献类型：
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作者：
D. Davis
摘要：过去，液体火箭发动机（LRE）经历过高频燃烧不稳定，这会在燃烧室中产生声场。声场与从喷射器喷出的流体射流相互作用，从而改变了射流的行为，与 LRE 稳定运行的行为相比。这种相互作用可能是导致燃烧不稳定的重要反馈机制。为了理解燃烧不稳定问题，有必要了解射流与声波的相互作用。根据过去对剪切同轴喷射器配置中液氧和氢推进剂组合的燃烧不稳定性研究，提出了外喷射与内喷射速度比大于约10的设计准则，以避免高频声燃烧不稳定性问题。然而，没有提供令人满意的物理解释。为了促进这种理解，在延伸至超临界状态的腔室压力下，对剪切同轴射流与高振幅非线性声场相互作用进行了冷流实验研究。液氮（LN2）从同轴喷射器的内管流出，而气态氮（GN2）从其环形区域流出。将注射器流体导入用气态氮加压的室中。声学激励由外部驱动器提供，能够提供高达 165 dB 的声场振幅。腔室的谐振模式决定了此处研究的两个频率，前两个模式约为 3 kHz 和 5.2 kHz。飞机的高速图像是用 Phantom CMOS 相机拍摄的。
Abstract : In the past, liquid rocket engines (LRE) have experienced high-frequency combustion instability, which impose an acoustic field in the combustion chamber. The acoustic field interacts with the fluid jets issuing from the injectors, thus altering the behavior of the jet compared to that of stable operation of the LRE. It is possible that this interaction could be a substantial feed back mechanism driving the combustion instability. In order to understand the problem of combustion instability, it is necessary to understand the interaction of the jet with the acoustic waves. From past combustion instability studies of the liquid oxygen and hydrogen propellant combination in a shear-coaxial injector configuration, a design guideline of outer-to-inner jet velocity ratio greater than about ten was proposed in order to avoid high-frequency acoustic combustion instability problems. However, no satisfactory physical explanation was provided. To promote this understanding, a cold-flow experimental investigation of a shear-coaxial jet interacting with a high-amplitude non-linear acoustic field was undertaken under chamber pressures extending into the supercritical regime. Liquid nitrogen (LN2) flowed from the inner tube of a coaxial injector while gaseous nitrogen (GN2) issued from its annular region. The injector fluids were directed into a chamber pressurized with gaseous nitrogen. The acoustic excitation was provided by an external driver capable of delivering acoustic field amplitudes up to 165 dB. The resonant modes of the chamber governed the two frequencies studied here, with the first two modes being about 3 and 5.2 kHz. High-speed images of the jet were taken with a Phantom CMOS camera.