扩压叶栅剪敏液晶试验与图像处理

基于剪敏液晶涂层(SSLCC)材料的光学特性,发展了适合于内流场狭小空间环境下的SSLCC边界层流动显示技术:设计并加工了微型摄像头-发光二极管(LED)组合式图像采集设备解决拍摄光路问题;基于二维SSLCC图像与三维模型的空间映射关系,建立了真实模型的三维重构方法;通过SSLCC图像光谱Hue色相值转化,实现了液晶图像信息的定量分析。以西北工业大学高亚声速平面叶栅风洞为平台,开展了某扩压叶栅吸力面边界层流态的剪敏液晶流动显示试验。结果表明:所发展的剪敏液晶显示技术可进行叶栅内流场边界层的流态测量;所建立的图像处理方法可为边界层流动特征的辨识及其特征位置确定提供技术支撑;在来流马赫数为0.12、攻角为0°的条件下,叶片吸力面边界层沿流向依次经历了层流边界层分离、再附着及转捩为湍流状态的过程,且边界层的发展受叶栅角区分离流动影响,造成其前缘分离区减小,再附着点和边界层转捩位置向前缘移动。

Experimental research on diffuser cascade using shear-sensitive liquid crystal and image processing

Based on the optical properties of shear-sensitive liquid crystal coating (SSLCC),a boundary layer visualization technology is developed in narrow space of wind tunnel.A mirco camera-LED combined image acquisition device is designed and processed to achieve the SSLCC image.A three-dimensional image reconstruction method is proposed based on the mapping relation between SSLCC image and the three-dimensional model.The information of the SSLCC image is analyzed quantitatively based on Hue value transformation of the SSLCC image.Based on the high subsonic linear cascade wind tunnel in Northwestern Polytechnical University,an experimental study is carried out on the boundary layer of a diffuser cascade using SSLCC.The results show that the boundary layer visualization technology developed in this paper can be used forboundary layer measurement of the linear cascade.The method proposed can provide technical support for the identification of the boundary layer characteristics and the determination of the feature location.At Mach number 0.12 and angle of attack 0°,the boundary layer on the suction side of the blade goes through a process of separation,reattachment and transition,the boundary layer is affected by the cascade corner separation flow,the separated region is reduced,and the location of reattachment and transition move towards the leading edge.