Penetration Characteristics of Pulsed Injection into Supersonic Crossflow
Penetration Characteristics of Pulsed Injection into Supersonic Crossflow
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DOI：
10.2514/6.2010-6645
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发表时间：
2010-07
期刊：
影响因子：
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通讯作者：
T. Kouchi;Keita Sasaya;Junya Watanabe;H. Shibayama;G. Masuya
中科院分区：
文献类型：
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作者：
T. Kouchi;Keita Sasaya;Junya Watanabe;H. Shibayama;G. Masuya
该报告通过实验和数值研究了脉冲喷射进入超音速横流的穿透特性。实验中，我们将脉冲上升时间为250 μs、脉冲宽度为750 μs的氦气注入马赫数为2马赫的超音速横流空气中。一百张时间序列纹影图像捕获了脉冲射流运动并研究了其穿透性能。图像显示，在一定的喷射压力值下，喷射压力上升阶段的脉冲射流穿透力高于喷射压力下降阶段的喷射穿透力。注入空气的二维非定常 RANS 模拟很好地捕捉了实验中观察到的射流穿透趋势。他们揭示了脉冲射流穿透的滞后现象是由于脉冲射流产生的向上流动，就像一个向喷射壁倾斜的段塞一样。在段塞前面产生反向旋转的涡流对并引起向上的流动。向上的水流在向下游流动时使射流形状变形。结果，脉冲射流穿透的滞后现象发生在脉动频率低于 5 kHz 的低区域。脉冲射流中涡对的大小和强度很大程度上取决于脉动频率。每个脉冲周期都会产生涡环，脉动频率高于10 kHz。与脉冲模式峰值喷射压力下的稳定模式相比，它们显着增加了射流穿透力并促进了喷射物与横流空气的混合。对于进一步更高的脉动频率，射流穿透力随着脉动频率的增加而迅速下降。穿透高度接近一个脉冲周期内平均喷射压力稳定模式下的穿透高度，因为相邻涡环之间的间隔变得接近，削弱了向上流动。
This report experimentally and numerically investigated the penetration characteristics of the pulsed injection into a supersonic crossflow. In the experiment, we injected helium gas with the pulse rise time of 250 μs and the pulse width of 750 μs into Mach 2 supersonic crossflow-air. One hundred time-series schlieren images captured the pulsed jet motion and investigated its penetration performance. The images revealed the pulsed jet penetration in a rising phase of injection pressure was higher than that in a declining phase of injection pressure at a certain value of injection pressure. Two-dimensional unsteady RANS simulations injecting air well captured the trends on the jet penetration observed in the experiment. They revealed the hysteresis of pulsed jet penetration was owing to the upward flow produced by the pulsed jet like a slug which inclined toward the injection wall. A counter-rotating vortex pair was generated in front of the slug and induced the upward flow. The upward flow deformed the jet shapes as it traveled downstream. As the result, the hysteresis of pulsed jet penetration occurred in a low regime of pulsation frequency below 5 kHz. The size and strength of vortex pair in the pulsed jet were greatly depended on the pulsation frequency. The vortex rings was generated in each pulse cycle with the pulsation frequency above 10 kHz. They remarkably increased the jet penetration and promoted mixing of the injectant with crossflow-air, compared with the steady mode at the peak injection pressure of the pulse mode. For further higher pulsation frequency, the jet penetration rapidly decreased with increasing the pulsation frequency. The penetration height approached to that in the steady mode of the average injection pressure in a pulse cycle, because an interval between the neighboring vortex rings became close to weaken the upward flow.