Performance of Rotating Cascades under the Inlet-Distortions : 2nd Report, Performance under the Circumferential Distortions

Abstract

Experimental investigations of rotating cascades operating under circumferential inlet-distortion flows are described. Systematic measurements of flow fields near a rotating cascade are made and attenuation of the distorted flows is evaluated quantitatively. Then, transfer of distorted velocity profiles through a cascade and unsteady responses of flow angles behind a cascade are calculated with an aid of a linear theory. Circumferential inlet-distortions are attenuated by a cascade at both the design and the off-design points, and the attenuation ratios diminish with an increase in the number of distortions and with a decrease in flow rates, but the rotational speed has a little influence on the attenuation effect. Attenuation ratios at the design and the off-design points under various operational parameters can be represented uniquely by the use of a reduced frequency. Transfer of distorted velocity profiles can be obtained from the actuator disk model and unsteady changes in relative outlet flow angles agree relatively well with theoretical ones ca1cu1ated from unsteady cascade theory on thin airfoils.