高超声速剪敏液晶强反光抑制摩阻预示

Suppressed strong reflection surface friction measurement by using shear sensitive liquid in hypersonic flow

  • 摘要: 在高空高速条件下,准确的摩阻预示对飞行器气动性能至关重要。虽然光学非接触剪敏液晶技术在摩阻测量中优势明显,但仍存在诸多制约因素。针对高超声速风洞试验中由模型姿态和曲率变化引起的剪敏液晶涂层摩阻测量图像过曝光问题,研究了液晶涂层的表面光学特性,开展了基于光度学原理的光学系统设计,优化了液晶涂层的镜面反射因子响应特性,实现了不损失色彩还原度的强反光效应抑制,消除了液晶彩色图像中的过曝光干扰,建立了可在单次试验过程中获取多迎角变化的模型表面摩阻测量方法。以常规高超声速风洞为平台,在实际来流马赫数为5.933条件下,开展了迎角分别为0°、4°和10°时的三角翼模型典型摩阻测量试验。结果表明:基于光度优化的剪敏液晶摩阻测量方法,能够在一次试验中获取不同模型姿态下的摩阻分布及边界层流态特征,试验效率比传统方法提升3倍甚至更高,扩宽了剪敏液晶涂层技术在风洞试验工程中的应用范围。

     

    Abstract: Precise surface friction measurement is important in hypersonic flight. Shear Sensitive Liquid Crystal (SSLC) coating technique is an advantage method. However, there are some unsolved problems. Strong reflection occurs when poses and curvature vary. To conquer the challenge, the optical property of SSLC is studied. A novel optics system is designed based on photometry. Specular reflection effect reduces with color reproduction retained. Overexposure phenomena fade away, so we can acquire multiple friction distribution results from the wind tunnel experiment at one time. Experiments were carried out in the hypersonic wind tunnel of China Academy of Aerospace Aerodynamics. The nominal Mach number is 5.933, and the Reynolds number per unit based on the free-stream conditions is 0.95 × 107 m−1. In the experiment, the friction resistance was investigated at angles of attack that ranged from 0° to 10°. Results show that the suggested method is able to obtain the friction measurement results while the attack angles change. Compared with traditional means, the efficiency is a threefold improvement. The application range has extended in hypersonic wind tunnel experiments.

     

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