Time Resolved Investigations of an Axial Compressor With Casing Treatment: Part 2 — Simulation

Abstract

A casing treatment with axial and radial skewed slots ending in a plenum chamber has numerically been investigated at a highly subsonic axial compressor stage. The aim was to understand the physical phenomena of this treatment family that are responsible for the stabilization of the blade passage flow and the drop in efficiency mostly observed. Unsteady 3D Reynolds-averaged simulations were performed with the commercial CFD Code TASCflow 2.12. The closure problem was faced with a standard k-ε high Reynolds turbulence model and a logarithmic wall function. Two configurations with solid casing and casing treatment were investigated at the operating points with maximum efficiency and on the stability line. The experimentally gained performance results of this configuration show an extension of the operating range of approximately 50% based on the operating range at nominal speed, while the efficiency for design conditions falls by 1.4%. Apart from this, measurements at part load conditions show operating points without any loss in efficiency. The numerical simulations predict this efficiency drop as well. The detailed analysis is performed for the solid casing and casing treatment configuration at the operating point on the stability line. Influences of the incidence flow, the tip clearance vortex and the blade suction side separation were investigated. Special interest is directed towards the interaction of the casing treatment with the blade passage flow field and a detailed analysis of the flow inside the casing treatment, the effect of the plenum chamber and the interaction with the treatment slot flow is performed.

Numerical investigation on the effect of a plenum chamber with slot-type casing treatment on the performance of an axial transonic compressor

“…The SMI for all 19 the CTs except for SP-4 is nearly equivalent with one another, which is consistent with the experimental conclusion for specific blade rotation speeds in Osborn et al 16 and Takata and Tsukuda. 17 From the overall performance comparisons, the plenum chamber can improve the compressor overall performance at the design point as CTs is implemented.…”

Computational Study of the Effects of Protruding Studs Casing Treatment on the Performance of an Axial Transonic Turbofan

“…The mechanism introduced by these casing treatments consists of fluid from low momentum regions near the blade tip being driven upstream of the blade and into the main flow region through the slots. Similar forms of casing treatment were used by Yu et al [21] and Emmrich et al [22,23]. A common finding of their work was that, due to a redistribution of the flow throughout the duct, the location where stall occurred changed from near the casing to a location near the hub.…”

“…23 displays isosurfaces of ν created for both stud cases in similar fashion as that created for the baseline case inFigure 5.18a. It is observed that now the low momentum region near the casing, as encased by the isosurface, extends from the blade flow passage, through the stator vanes, and all the way to the outlet plane.…”

“…23 Forward-looking-aft view of isosurfaces of ν at near stall conditions using Studs 1 25 Recirculation on suction side of stator blades near casing for near stall conditions.…”

Momentum Transportation Analysis in Axial-slot Casing Treatment for Axial Compressors

“…Nowadays, more and more studies are performed by computational fluid dynamics (CFD). Some mechanisms of casing treatment have been proposed (Emmrich et al, 2007;Lu et al, 2009;Muller et al, 2008). After several decades of research, casing treatment has been used in various compressors.…”