Time Resolved Investigations of an Axial Compressor With Casing Treatment: Part 1 — Experiment

Abstract

A casing treatment with axial and radial skewed slots ending in a plenum chamber has experimentally been investigated at a highly subsonic axial compressor stage. The aim was to investigate the physical phenomenon of this treatment family that is responsible for the stabilization of the blade passage flow and the drop in efficiency mostly observed. The experimentally gained performance results of this configuration showed an extension of the operating range by approximately 50%, while the efficiency for design conditions is reduced by 1.4%. Apart from this, operating points at part load conditions have been observed nearly without any loss in efficiency. The detailed flow analysis is performed by means of results from a 3D pneumatic probe with temperature sensor and a dynamic total pressure probe. The focus of the investigations is on the incidence flow to the compressor rotor, the tip clearance vortex flow in combination with the wall stall separation region and the blade stall due to suction side separation. The casing treatment configuration is investigated with a special interest in detecting those effects which have an impact on the stability and the compressor overall efficiency, including the interaction of the rotor and the stator flow fields.

Improvement of Moderately Loaded Transonic Axial Compressor Performance Using Low Porosity Bend Skewed Casing Treatment

“…Casing treatment or placing a porous casing around the rotor tip is in effect a technique to control the casing boundary layers and thus delay the occurrence of the instabilities. This fact has been confirmed by several investigators [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”

“…It was concluded from the above studies that an angle of skew of +45 ∘ would be most beneficial. Emmrich et al [15][16][17] carried out numerical and experimental analysis of a single stage subsonic compressor coupled with skewed casing treatment with a porosity of 67%. The slots were inclined to the axial direction by 15 ∘ and to the radial by 45 ∘ in the direction of rotation.…”

The challenge of stereo PIV measurements in the tip gap of a transonic compressor rotor with casing treatment

“…A large number of numerical simulations can be found in the literature (e.g. Hathaway 2002, Zhu and Chu 2005, Emmrich et al 2007 discussing compressor performance as well as aerodynamic effects. In order to validate the numerical models applied for CFD, the demands on accuracy and spatial resolution for non-intrusive laser-based flow diagnostics are steadily increasing to match the continuous improvement of numerical simulation tools.…”

Effect of Rotor Tip Casing Treatment on the Performance and Stall Margin of a Transonic Axial Compressor Stage

“…Emmrich et al [1] have investigated a highly subsonic axial compressor stage with casing treatment both experimentally and numerically for understanding the flow physics. Effect of casing treatment with axial and radial skewed slots for a high subsonic axial compressor stage, improved stall margin but with slight loss in efficiency.…”

“…This revealed that in casing treatment delays vortex break down and helps in moving surge line to lower mass flows rates. Wilke and Kau [3] have shown that cavities or slots can successfully reduce the detrimental three-dimensional flow phenomena Fig.1 casing treatment slot on rotor tip region of a compressor blade [1] originating at the rotor tip gap. But the authors did not observe same effect at different design speeds with the tip in nearly subsonic conditions.…”