Abstract
The designers of radial turbomachinery need detailed information on the impact of the side chamber flow on axial thrust and torque. A previous paper investigated centripetal flow through narrow rotor–stator cavities and compared axial thrust, rotor torque and radial pressure distribution to the case without through-flow. Consequently, this paper extends the investigated range to centrifugal through-flow as it may occur in the hub side chamber of radial turbomachinery. The chosen operating conditions are representative of high-pressure centrifugal compressors used in, for example, carbon capture and storage applications as well as hydrogen compression. To date, only the Reynolds number range up to Re=2·107 has been investigated for centrifugal through-flow. This paper extends the range to Reynolds numbers of Re=2·108 and reports results of experimental and numerical investigations. It focuses on the radial pressure distribution in the rotor–stator cavity and shows the influence of the Reynolds number, cavity width and centrifugal mass flow rate. It therefore extends the range of available valid data that can be used to design radial turbomachinery. Additionally, this analysis compares the results to data and models from scientific literature, showing that in the higher Reynolds number range, a new correlation is required. Finally, the analysis of velocity profiles and wall shear delineates the switch from purely radial outflow in the cavity to outflow on the rotor and inflow on the stator at high Reynolds numbers in comparison to the results reported by others for Reynolds numbers up to Re=2·107.
Highlights
IntroductionDuring the design phase of radial turbomachinery, axial thrust on the rotor must be known with sufficient precision to select axial bearings and ensure reliable operation
During the design phase of radial turbomachinery, axial thrust on the rotor must be known with sufficient precision to select axial bearings and ensure reliable operation.disc friction torque is needed to estimate machine performance
The authors showed the influence of centripetal through-flow on rotor–stator cavity flow at high Reynolds numbers up to Re = 2 · 108
Summary
During the design phase of radial turbomachinery, axial thrust on the rotor must be known with sufficient precision to select axial bearings and ensure reliable operation. The test rig superposed centrifugal through-flow on the turbulent rotor–stator cavity flow to investigate its effects on the radial distribution of pressure and the torque needed to drive the disc This test rig was able to reach Reynolds numbers up to Re = 8 · 106 and operated at small and large axial clearances to analyse the flow structures with merged and separated boundary layers. Using the 17 power law for boundary layer velocity profiles and the empirical Blasius relation for shear stress on surfaces, they developed an approximate model for the radial pressure distribution and disc torque increase caused by centrifugal through-flow for the case of large cavity widths This paper compares their model predictions with measurements recorded in the authors’ test rig. This paper compares their measurements and simulation results to those presented here
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