Performance of Compressor Blade Rows in a Sloping Flowpath

Abstract

In an effort to reduce engine length and weight it is desirable in some applications, such as high bypass ratio turbofan engines, to introduce compressor stages into a downward sloping flowpath. In this “mixed flow” compressor the airfoil orientation with respect to the flowpath becomes important to ensure good performance. The performance of cascades and compressor stages with sloping walls is presented. Three methods of introducing blading into the flowpath were evaluated. It is shown that by canting the blading to be normal to the flow direction, no penalty in performance is incurred compared to the performance of a typical axial compressor with cylindrical flowpath. Test results are compared with predictions based on intrablade analysis and a wall boundary layer calculation. Qualitatively good agreement is obtained except for the case when the blading is swept with respect to the flow direction. Need for further investigtion of three dimensional internal viscous flows is indicated.