Off-Design Transition and Separation Behavior of a CDA Cascade

Abstract

The design of modern axial flow compressor blade sections as well as the code validation require experimental information about the transition and separation behavior of blade surface boundary layers. The experience has shown in the past that such information has to be obtained on the whole surface and not only by point measurements because both transition and separation may be of a three-dimensional nature even in a straight cascade. Therefore, a new visualization technique based on Liquid Crystals (LC), showing the adiabatic wall temperature, has been developed. With this method, transition, local separation, and complete separation can be detected. Design and off-design data of a subsonic (M1 = 0.62) Controlled Diffusion Airfoil (CDA) compressor cascade measured in a wind tunnel are presented. The LC results are supplemented by ink-injection tests and overall performance data.