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.