High Turning Compressor Tandem Cascade for High Subsonic Flows - Part 2: Numerical and Experimental Investigations

Abstract

A high turning, supercritical tandem cascade with contracting endwalls was designed in part 1 of the present paper. Part 2 deals with a detailed evaluation of numerical flow simulations at the design Mach number 0.89 and an o -design (flight idle) Mach number 0.6 as well as experimental and numerical investigations at a lower Mach number 0.175. Flight idle performance could be obtained at this speed by adapting the endwall contraction for missing compressibility e ects. In order to ensure reasonable assessment, the tandem cascade was consistently compared to a conventional cascade which was designed as a reference with identical inlet Mach number and similar turning. The numerical midspan results indicate an advantage to exist for the tandem design at the higher (supercritical) Mach number, an advantage that disappears at the lower (subcritical) Mach number. O -design results are confirmed by the experimental investigations where the tandem shows higher turning, slightly higher losses and a better behavior at high incidences. Besides midspan performance, an insight is given to endwall flow features of tandem cascades. An important result is revealed by spanwise wake measurements showing the secondary flow losses of the tandem cascade to be considerably lower than the corresponding losses of the reference cascade, at least at subcritical Mach numbers. Unfortunately, this finding cannot be reproduced by RANS simulations due to an overprediction of secondary flow.