A mapping of the viscous flow behavior in a controlled diffusion compressor cascade using laser doppler velocimetry and preliminary evaluation of codes for the prediction of stall

Abstract

Detailed measurements were made at M=0.25 and Re sub c = 700000 of the flow through a linear compressor cascade of controlled diffusion (CD) blading using a two-component argon-ion laser doppler velocimeter system. The measurements included mapping of the inviscid flow in the passage between two adjacent blades, boundary layer surveys, and wake surveys. Viscous flow phenomena such as a laminar separation region with reattachment on the suction surface, and laminar to turbulent transition on the pressure surface were resolved, and the viscous growth to the trailing edge was defined for three inlet angles from design incidence to near stall. Numerical calculations to predict the flow were carried out using a fully developed boundary layer code, a strongly interactive viscous inviscid code and a Navier Stokes code. It was shown that the common weakness of numerical predictors was in the modelling of transition and turbulence. The documented data can be used generally to calibrate compressor cascade analysis codes and thus enable reliable predictions of stall.