Application of quantitative monochrome calibrated schlieren technique in highly-loaded turbine cascade test

As the load of the turbine components of aircraft engines continuously increases, shock loss becomes the dominant factor of turbine stage loss and has become a hot topic. Schlieren technique is one of the few effective experimental methods to observe and study shock wave and, thus, has been widely used. Nevertheless, limited by camera accuracy and computer image processing technology, quantitative schlieren analysis methods were difficult to achieve in engineering applications. Fortunately, several quantitative schlieren methods have been developed with the help of new digital technology. Applying schlieren technique to the highly-loaded turbine cascade test is of great significance to the study of shock wave in highly-loaded turbine cascades. In this paper, the results of quantitative density field and shock intensity and loss in the cascade are obtained by using a double reflection type monochrome schlieren device. The boundary condition of density field is obtained by pressure test, and MATLAB software is used as image processing calculation tool. The quantitative results of this paper prove the feasibility of applying quantitative schlieren method to highly-loaded turbine cascade tests. Also, the implemented image processing method and density boundary condition acquisition method are suitable and convenient for cascade flow and shock measurement tests.