Time Resolved Experimental Investigations of an Axial Compressor With Casing Treatment

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.

Effect of Casing Treatment on the Type of Instability Inception in a High-Speed Axial Compressor

“…For the researches about the casing treatment, most of them focus on the overall performance to improve the stall margin and reduce the efficiency penalty by testing different forms of casing treatment, which includes circumferential groove [11][12][13], skewed slot with different shapes [11][12][13][14][15], self-recirculating casing treatment [16], SPS casing treatment [17]. On the other hand, some researches pay attention to the influence of casing treatment on detailed flow field, trying to explain how casing treatment delays the stall [18][19][20]. These studies indicate that the casing treatment can delay the occurrence of instability inception by inducing a recirculating path to reduce flow blockage at rotor tip.…”

Effect of axial skewed slot casing treatment in a transonic fan

“…axial slots which are skewed to the radial direction) has been studied by a number of researchers. [11][12][13][14][15][16][17] Greitzer et al 11 carried out experiments to investigate the effect of axial slots on the performance of two compressor rotor builds having different solidities. It was found that endwall casing treatment is only beneficial to the so called ''wall-stall'' compressor rotors, in which stall is initiated on the annulus wall.…”

“…Results showed that the effect of slots is the repositioning of the tip clearance vortex trajectory toward the trailing-edge of the blade passage and delaying the movement of the incoming-tip clearance flow interface to the leading-edge plane. Emmrich et al 16 experimentally investigated axial and radial skewed slots in a highly subsonic compressor stage. Approximately 50% operating range extension was obtained at the expense of about 1.4% reduction in the compressor efficiency.…”

Numerical simulation of unsteady tip clearance flow in an isolated axial compressor rotor blades row

“…This will allow higher thrust-to-weight ratios to be achieved, which is one of the main objectives of the aeroengine designers. Compact design of compressors means to reduce the number of stages, which in turn is associated with imposing more aerodynamic loads on each stage [1]. On the other hand, to consider tip clearances for the blades is inescapable.…”