Unsteady Study on the Effects of Matching Characteristic of Tandem Cascade on the Performance and Flow at Large Angle of Attack

Abstract

To investigate the effects of matching characteristics of tandem cascade on the performance and flow at large angle of attack, the unsteady numerical simulation has been implemented. The influences of different turning angle ratio (TR) and chord length ratio (CR) of two blades and the relative angle of attack of rear blade (Delta) are analyzed. The numerical results indicated that the tandem cascade can obtain overall performance improvement including higher static pressure ratio and lower total pressure loss with the matching parameters in the range of TR=3~5, CR=0.5~1.2, and Delta=-15°~-5°. The separation on the front blade has more prominent impact than that on the rear blade, so the performance improvement of tandem cascade is significantly dependent on the reduction of front-blade separation and loss. Regarding the rear blade, the gap injection effect can periodically control the separation. Temporal and spatial analysis of the flow field shows that the optimal-performance cases generally have much smaller wake loss for both two blades, but the unsteady characteristics of the wake loss is more apparent than that of the poor performance cases.