Velocimetry measurements of unstart in an inlet-isolator model in Mach 5 flow
Velocimetry measurements of unstart in an inlet-isolator model in Mach 5 flow
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DOI：
10.2514/1.j050037
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发表时间：
2010-09
期刊：
影响因子：
2.5
通讯作者：
J. Wagner;K. Yuceil;N. Clemens
中科院分区：
文献类型：
--
作者：
J. Wagner;K. Yuceil;N. Clemens
利用粒子图像测速技术和快速响应壁面压力测量技术，对落地式进气道隔离段模型在马赫数为5的气流中的不起动动力学进行了实验研究。进气道压缩采用6度斜坡，隔离器是一个高25.4 mm、宽50.8 mm、长242.3 mm的矩形直管道。不起动是从超燃冲压发动机模式（在隔离段内完全超音速）通过偏转隔离段下游端的机动襟翼来启动的。在襟翼完全放下的情况下，启动流场的粒子图像测速数据捕捉到了隔离段边界层和初始进气道反射激波系统的特性。在未启动过程中，未启动激波系统通过进气道隔离段向上游传播。粒子图像测速数据揭示了一个复杂的，三维的流动结构，强烈依赖于粘性机制。特别是，未起动激波系统向上游传播，并引起明显的边界层分离。侧视粒子图像测速数据表明，最强的分离在不启动的位置与初始入口激波的冲击位置，因为它反映了隔离。例如，在未起动的中间，未起动激波系统与顶棚边界层的大量分离有关，顶棚边界层开始于第一次进口激波反射撞击顶棚的地方。在进口激波反射冲击位置处分离增加的观察结果可能是由于这些位置处的附面层受到较大的逆压梯度的影响，从而使它们更容易分离。在不起动过程中，在底板和顶板附近形成大范围的分离流，反向流速度高达约0.4U ∞。这些分离的亚音速流区似乎延伸到隔离段出口，形成一条通道，隔离段出口边界条件可通过该通道与上游连通。平面粒子图像测速数据显示，不启动过程开始于隔离段侧壁边界层的分离。总体而言，未启动流结构是高度三维的。
The dynamics of unstart in a floor-mounted inlet-isolator model in a Mach 5 flow are investigated experimentally using particle image velocimetry and fast-response wall pressure measurements. The inlet compression is obtained with a 6-deg ramp and the isolator is a rectangular straight duct that is 25.4 mm high by 50.8 mm wide by 242.3 mm long. Unstart is initiated from the scramjet mode (fully supersonic in the isolator) by deflecting a motorized flap at the downstream end of the isolator. With the flap fully down, the particle image velocimetry data of the started flow capture the characteristics of the isolator boundary layers and the initial inlet reflected shock system. During unstart, the unstart shock system propagates upstream through the inlet-isolator. The particle image velocimetry data reveal a complex, three-dimensional flow structure that is strongly dependent on viscous mechanisms. Particularly, the unstart shock system propagates upstream and induces significant boundary-layer separation. Side-view particle image velocimetry data show that the locations of strongest separation during unstart correlate with the impingement locations of the initial inlet shock as it reflects down the isolator. For example, in the middle of unstart, the unstart shock system is associated with massive separation of the ceiling boundary layer that begins where the first inlet shock reflection impinges on the ceiling. The observation that separation increases at the inlet shock reflection impingement locations is likely due to the fact that the boundary layers in these locations are subject to larger adverse pressure gradients, thus making them more susceptible to separation. During the unstart process, large regions of separated flow form near the floor and ceiling with reverse flow velocities up to about 0.4U ∞ . These regions of separated, subsonic flow appear to extend to the isolator exit, creating a path by which the isolator exit boundary condition can be communicated upstream. Plan-view particle image velocimetry data show the unstart process begins with separation of the isolator sidewall boundary layers. Overall, the unstart flow structure is highly three-dimensional.