Effects of reynolds number on the flow of air through a cascade of compressor blades

Abstract

The experimental work consisted of the separate testing of three cascades of axial-flow compressor blades of camber angles 20 deg, 30 deg and 40 deg respectively. Measurements were made of the distribution of static pressure over the central cross-section of the middle blade of each cascade, together with traverses of static pressure, total head and angle of flow at inlet and outlet to each cascade in the plane of the central cross-section. The tests covered a range of actual Reynolds number from 3 x 10power4 to 5 x 10power5, based on the inlet air velocity and the blade chord, and also a range of inlet air angle α1, from 35 deg to 60 deg. In the tests there were numerous cases of laminar boundary-layer separation at low Reynolds numbers and a few cases of turbulent separation at higher Reynolds numbers. These occurred on the convex surfaces of the blades. There were also a few cases of laminar separation from the concave surfaces of the blades. The results show the effect of Reynolds number, blade camber, and inlet air angle on cascade performance. The type of pressure distribution likely to give good performance over a wide range of Reynolds number is discussed.