A wind-tunnel investigation of the stalling performance of two compressor cascades of different aspect ratios at low speed

Abstract

Two compressor cascades of aspect ratio 2.10 and 4.83 were tested up to the stall point in a working section with solid side walls. A change in aspect ratio was obtained by changing the blade chord only. The blade section profile was the 10C4/30C50, staggered at 36 degrees with a space-chord ratio of 0.88, and there was no tip clearance. Reynolds number similarity was maintained but its value was kept above a "critical" value. Substantial difference in performance is indicated between the two aspect ratios. The high aspect ratio cascade gives more deflection at the mid-span near stall, but stalls first. The long chord, low aspect ratio blade stalls gently whilst a classical type of sudden stall occurs at the other aspect ratio. Higher pressure rise coefficient is observed at the high aspect ratio, increasing slightly with incidence up to the stall point. Substantially higher spanwise contraction is evident with the low aspect ratio. The order of magnitude of the increase in axial velocity for both cascades is remarkably high. Further tests show that the wall stall, which is present at each incidence, is different in the two cases. It appears that the flow near the wall in the long chord blade rotates further in the passage and the stall near the end wall is more along the blade than along the wall. In the case of the short chord, the separation areas along the blade and the wall are approximately equal. The results for the overall performance are generally consistent with compressor work.