The Effects of Wake-Passing Unsteadiness Over a Highly Loaded Compressor-Like Flat Plate

Abstract

The present study is concerned with wake-induced unsteady effects in axial-compressor blade rows. The goal is to exploit these effects in order to design high-lift blades without increasing the profile loss, as has been achieved for low-pressure turbine blades. In the first part of this paper, the experimental means and the computational fluid dynamics tools are described. The rig features a flat plate that can be subjected to different velocity distributions representative of the suction side of a real compressor blade. Cylindrical bars mounted on a moving system simulate the incoming wakes from the upstream blade row in the compressor. Results are presented for steady flow and for unsteady compressor-like conditions. In all cases, the separation bubble of the steady flow is suppressed by the turbulence that is induced in the boundary layer by the wakes at approximately 10% of the suction side. Its reappearance is then delayed by a region of stable laminar-like flow and low loss due to the so-called calming effect that follows the wake-induced patch. The paper describes these phenomena in detail for one particular pressure distribution. It is then shown that it should be possible to increase the lift by 35% while keeping the same level of loss as the initial conventional pressure distribution of the study.