Session: 31-07 Compressor Stability and Loss Mechanisms

Paper Number: 153215

A Unified Framework for Compressor Stall Inception 

This paper presents a first-of-a-kind description of compressor rotating stall inception that explains the two different routes to stall that have been reported in the literature over the past three decades. A low-order dynamic system model, an actuator disk analysis, is shown to capture the two transient, stall inception behaviors, namely the initially linear growth of small amplitude, long length scale (on order of compressor circumference), sinusoidal perturbations, versus short length scale (on order of a blade pitch) velocity disturbances with non-linear and faster growth. The analysis demonstrates that
the two distinctly different processes are on a continuum of compressor dynamic behaviour and can be captured by the same unifying framework. The features of these qualitatively different processes, including the different length and time scales, are revealed without explicit modeling of the blades. The differentiator for the two behaviors is shown to be the slope of the compressor pressure rise characteristic at flows below that corresponding to the peak pressure rise. Small (defined in the paper) positive slopes to the left of the peak lead to growth of the long length scale, sinusoidal perturbations into fully developed rotating stall cells. Cases with large (defined in the paper) slopes, lead to the more rapid evolution of short length
scale, non-sinusoidal disturbances, into stall cells. The actuator disk simulations indicate the two types of transient fluid motions described bound a range of stall inception behaviors, including combinations of the two, that depend on compressor pressure rise characteristic slope. Data from compressor experiments and full annulus, unsteady Reynolds-averaged Navier-Stokes simulations are used to connect the shapes of radially varying compressor characteristics, in the rotating stall regime, to flow features including blade leading edge and corner separations. Finally, the experiments and full annulus computations
confirm the results derived from the low-order model and establish that it captures well the transient flows and physical mechanisms of rotating stall inception.

Presenting Author: Sam Grimshaw Whittle Laboratory, University of Cambridge

Presenting Author Biography: Sam is the Mitsubishi Heavy Industries (MHI) Senior Research Fellow at Girton College, University of Cambridge. He works at the Whittle Laboratory on technologies which will help to decarbonise future power and propulsion.

Authors:

Sam Grimshaw Whittle Laboratory, University of Cambridge
Graham Pullan Whittle Laboratory, University of Cambridge
Edward Greitzer Department of Aeronautics and Astronautics, Massachusetts Institute of Technology
Zoltan Spakovszky Department of Aeronautics and Astronautics, Massachusetts Institute of Technology