Impeller Stall Induced by Reverse Propagation of Non-Uniform Flow
Abstract
In the case of centrifugal compressors, minor non-uniform flow
upstream of the impeller is induced by an asymmetrical
configuration in the circumferential direction at the compressor
suction casing. This non-uniform flow is transmitted to the
impeller discharge, but this minor non-uniform flow does not
usually cause an adverse effect on the impeller stage
performance. However, we found this is amplified at the return
channel due to flow separation at reduced flows (depending on
return channel geometry), and the amplified non-uniform flow
did induce impeller stall by reverse propagation from the return
channel to the impeller.
These non-uniform flows caused a significant operating range
reduction for a large flow coefficient impeller. The
aerodynamics issues were mitigated using CFD analysis
techniques, and eventually confirmed by the compressor
performance during shop performance testing.
The OEM conducted the CFD analyses using two (2) return
channel geometries with several CFD models to verify the
effect of the return channel geometry on impeller stall and to
Copyright© 2018 by Turbomachinery Laboratory, Texas A&M Engineering Experiment Station
confirm the most suitable CFD modeling method for stall
evaluation. Shop performance tests utilizing both return
channel geometries were conducted and compared to the CFD
analyses. These studies were conducted while collaborating
with the end-user. The steady CFD calculation was conducted
with frozen rotor interface between full annulus impeller and
stator parts. The modeling of diffuser and return channel was
varied as follows:
(1) 1-pitch model for the return channel with mixing plane at
diffuser
(2) Full-annulus model for the return channel with a mixing
plane at the diffuser
(3) Full-annulus model for the return channel without a mixing
plane at the diffuser
From the above studies and the shop performance testing, it
was confirmed that the proposed CFD modeling method could
simulate the measurements taken during the shop performance
tests and that the CFD modeling meth
Description
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Citation
Iwamoto, Shinji; Shoji, Yoshiaki; Yoneda, Keizo; Nakaniwa, Akihiro; Barrington, Bryan (2018). Impeller Stall Induced by Reverse Propagation of Non-Uniform Flow. Turbomachinery Laboratory, Texas A&M Engineering Experiment Station. Available electronically from https : / /hdl .handle .net /1969 .1 /172503.