Time-Space Trajectory of Unsteady Jet into Supersonic Crossflow Using High-Speed Framing Schlieren Images
Time-Space Trajectory of Unsteady Jet into Supersonic Crossflow Using High-Speed Framing Schlieren Images
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DOI：
10.2514/6.2009-7316
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发表时间：
2009-10
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影响因子：
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通讯作者：
T. Kouchi;T. Hoshino;Keita Sasaya;G. Masuya
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文献类型：
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作者：
T. Kouchi;T. Hoshino;Keita Sasaya;G. Masuya
超音速横向射流流场对于超燃冲压发动机超音速燃烧室具有重要作用。超音速导致非定常测量的困难，因为流动中的特征时间很短。缺乏时间序列数据使得燃烧器的开发变得困难。为了研究射流非定常运动，高速分幅相机以 250 kHz 采样率拍摄了 100 张连续的超音速横向射流流场纹影图像。主流马赫数为2.0，喷射物为氦气，模拟燃料氢。这项工作揭示了密度加权射流与横流速度比（吹气比：r）和喷射器直径（D）对射流边界运动的影响。新提出的基于 Sobel 空间滤波器的图像处理可以有效地从时间序列纹影图像中跟踪射流边界。 2700个样本数据给出了射流边界的概率密度函数（PDF）。 PDF 分布表明射流穿透力对 rD 空间中的 r 和 D 都不敏感。然而，即使在 rD 空间中，射流扩散对 r 和 D 都很敏感。这是由于喷射器近场产生的压缩效应。将时间序列射流边界重新映射为时空射流轨迹表明，射流中大涡流的对流速度对r和D不敏感，恒定为460 m/s。该地图为我们提供了有关射流运动的另一个重要信息：射流中高穿透涡流形成的周期。时空射流轨迹的频谱分析研究了横向射流中高穿透涡流的脱落频率。结果，我们发现高穿透涡流发生在相对不同的频率。在超音速横向喷射的远场中，喷流不稳定性的特定放大频率可能不存在。
Supersonic transverse jet flow-field has an important role for supersonic combustor in scramjet engines. Supersonic speed induces the difficulty in unsteady measurements, because characteristics time is very short in the flow. Lacks of time-series data make the combustor difficult to develop. To investigate the jet unsteady motion, high-speed framing camera captured 100 successive schlieren images of the supersonic transverse jet flow-field with 250 kHz sampling rate. The mainstream Mach number was 2.0 and the injectant was helium gas, simulating fuel hydrogen. This work revealed the effects of density-weighted jetto-crossflow velocity ratio (blowing ratio: r) and the injector diameter (D) on the motion of the jet boundary. Newly suggested image processing, based on the Sobel spatial filter, efficiently tracked the jet boundary from the time-series schlieren images. 2700 sample data gave the probability density function (PDF) of the jet boundary. The PDF distributions indicated the jet penetration was insensitive to both r and D in rD space. The jet spreading, however, was sensitive to both r and D even in rD space. This was due the compressibility effect generated at the near field of injector. Remapping the time-series jet boundary as the time-space jet trajectory indicated the convective velocity of the large eddies in the jet was insensitive to r and D. It was constant of 460 m/s. The map gave us another important information on the jet motion: cycle of high-penetrated eddy formation in the jet. Spectrum analysis of the time-space jet trajectory investigated the shedding frequencies of highpenetrated eddy in the transverse jet. As the results, we find out that the high-penetrated eddy occurred at comparatively various frequencies. The specific amplified frequency of the jet instability probably did not exist at the far field of supersonic transverse injection.