Radial Inflow Into the Downstream Cavity of a Compressor Stator Well

Abstract

The subject of the interaction between the mainstream annulus flow and seal flows is now receiving increased attention as a result of concerted attempts to further improve compressor performance. In an axial compressor the use of a shroud on a stator blade row necessitates a trench and results in two such regions of interaction at the upstream and downstream stator well cavities with flow limited by a labyrinth seal. The upstream stator well cavity, with its superposed radial outflow, has received some attention and possess similarities with the cavity downstream of nozzle guide vanes in axial turbines, which have received considerable interest. The downstream compressor stator well cavity has, however, been less extensively studied. Here the flow is dominated by inflow into the cavity. This inflow is driven by the pressure gradient across the blade row and hence the pressure gradient between the upstream and downstream cavities. This paper presents preliminary pressure measurements from a high-speed two-stage research compressor. The experimental results are compared with two and three-dimensional CFD models. In order to gain confidence with CFD for compressor stator wells, the case of inflow into a rotor-stator disc wheelspace has been revisited; validating a commercial code, Fluent, for a wide range of flow conditions. This code has then been used to predict the detailed flow structure for the conditions in the experimental research compressor.