Application of non-axisymmetric endwall contouring in compressor intermediate duct with a large radius change to length ratio

In order to explore the application potential of non-axisymmetric endwall contouring (NAEC) in the compressor intermediate duct (CID) with a large radius change to length ratio, the aerodynamic characteristic of this type of compressor intermediate duct has been numerically studied in the present work, and the effect of the non-axisymmetric endwall contouring on the hub of the compressor intermediate duct has been investigated in terms of flow and throttle characteristics. The results show that, the flow loss and outlet flow distortion of the compressor intermediate duct are mainly originated from the corner separation of the strut. With the increase of the flow rate, the flow loss and outlet flow distortion are enhanced, which is opposite to the change of the strut corner separation. On this basis, this study has proposed a novel approach for non-axisymmetric endwall contouring using trigonometric functions. By adjusting the curvature of the hub contour near the strut and modifying the axial pressure gradient, this method can effectively reduce the intensity of the corner separation around the strut. Moreover, the implementation of such a non-axisymmetric endwall contouring does not compromise the decreasing trend of the total pressure recovery coefficient with increasing flow rate. Within a wide range of large flow rates (with the relative flow rate not lower than 0.6) in the compressor intermediate duct, this method can successfully attenuate the intensity of secondary flows within the compressor intermediate duct, reduce flow losses, and improve both the flow uniformity at the exit as well as the overall performance of the compressor intermediate duct.