Abstract
The flow in a linear compressor cascade with tip gap is simulated using a wall-resolved compressible Large-Eddy Simulation. The cascade is based on the Virginia Tech Low Speed Cascade Wind Tunnel. The Reynolds number based on the chord is 3.88 x 10⁵ and the Mach number is 0.07. The gap considered in this study is 4.0 mm (2.9% of axial chord). An aerodynamic analysis of the tip-leakage flow allow us identifying the main mechanisms responsible for the development and the convection of the tip-leakage vortex downstream of the cascade. A region of high turbulence and vorticity levels is located along an ellipse that borders the top of the tip-leakage vortex. The influence of the airfoil suction side boundary layer development on the tip-leakage vortex is highlighted by tripping the flow. A tripped boundary layer induces a stronger and larger tip-leakage vortex that tends to move further away from the airfoil suction side and from the endwall compared with an untripped flow. The boundary layer turbulent state influences the tip-leakage flow development.
Highlights
The required tip clearance between rotating rows and fixed parts in a turbomachine is responsible for a leakage flow, excessively difficult to measure (Stauter, 1992) or to simulate (Tyacke et al, 2019)
Probes 1 to 4 are located respectively at X =ca 1⁄4 0:5, X =ca 1⁄4 0:6, X =ca 1⁄4 0:7 and X =ca 1⁄4 0:8. We focused on this particular zone because it may be one of the major noise source related to tip-leakage flow, according to Koch et al (Koch et al, 2020)
A first compressible wall-resolved Large-Eddy Simulation (LES) of a linear compressor cascade with tip gap has been achieved in order to investigate the aerodynamic mechanisms responsible for the tip-leakage vortex (TLV) formation and its behavior as it is convected downstream
Summary
The required tip clearance between rotating rows and fixed parts in a turbomachine is responsible for a leakage flow, excessively difficult to measure (Stauter, 1992) or to simulate (Tyacke et al, 2019). This tip-clearance flow generates complex vortical structures (Storer and Cumpsty, 1991) that interact with the main-stream flow yielding substantial losses (Denton, 1993). It is associated with unsteady mechanisms that may drive stall inception and noise emissions (Kameier and Neise, 1997). The same configuration is considered in the present work to investigate the main mechanisms associated with the tip-leakage vortex (TLV) and the influence of the airfoil suction side boundary layer development on its convection and dissipation downstream
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