Impact of leakage inlet swirl angle in a rotor-stator cavity on flow pattern, radial pressure distribution and frictional torque in a wide circumferential Reynolds number range

Authors

Tilman Raphael Schröder - University of Duisburg-Essen
Hans Josef Dohmen - University of Duisburg-Essen
Dieter Brillert - University of Duisburg-Essen
Friedrich Karl Benra - University of Duisburg-Essen

Abstract

In side-chambers of radial turbomachinery, which form rotor-stator cavities, complex flow patterns develop that contribute substantially to axial thrust on the shaft as well as frictional torque on the rotor. Moreover, leakage flow through the side-chambers may occur in both centripetal as well as centrifugal direction, which significantly influences the rotor-stator cavity flow and has to be carefully considered in the design process: Precise correlations quantifying the effects of rotor-stator cavity flow are needed for the design of reliable and highly efficient turbomachines. In this paper, centripetal leakage flow with and without pre-swirl in rotor-stator cavities is investigated experimentally as well as numerically, combining the experimental results from two test rigs: A hydraulic test rig covering the Reynolds number range 4⋅10^5≤Re≤3⋅10^6 and a test rig for gaseous rotor-stator cavity flow which is operated at Reynolds numbers 2⋅10^7≤Re≤2⋅10^8. These ranges cover the operating range of hydraulic as well as thermal turbomachinery. The influence of circumferential Reynolds number, axial gap width and centripetal through-flow on radial pressure distribution, axial thrust and frictional torque is presented, with through-flow being characterised by its mass flow rate and swirl angle at the inlet. The results present a comprehensive insight into the flow in rotor-stator cavities with superposed centripetal through-flow and provide an extended database to aid the turbomachinery design process.