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Research Papers

# Rotating Stall Observations in a High Speed Compressor—Part II: Numerical Study

[+] Author and Article Information
J. Dodds

Rolls-Royce,
Derby DE24 8BJ, UK
e-mail: John.dodds@rolls-royce.com

M. Vahdati

Imperial College,
London SW7 2AZ, UK
e-mail: m.vahdati@imperial.ac.uk

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 8, 2014; final manuscript received July 29, 2014; published online November 18, 2014. Editor: Ronald Bunker.

J. Turbomach 137(5), 051003 (May 01, 2015) (10 pages) Paper No: TURBO-14-1124; doi: 10.1115/1.4028558 History: Received July 08, 2014; Revised July 29, 2014; Online November 18, 2014

## Abstract

In this two-part paper the phenomenon of part span rotating stall is studied. The objective is to improve understanding of the physics by which stable and persistent rotating stall occurs within high speed axial flow compressors. This phenomenon is studied both experimentally (Part I) and numerically (Part II). The experimental observations reported in Part I are now explored through the use of 3D unsteady Reynolds-averaged Navier–Stokes (RANS) simulation. The objective is to both validate the computational model and, where possible, explore some physical aspects of the phenomena. Unsteady simulations are presented, performed at a fixed speed with the three rows of variable stator vanes adjusted to deliberately mismatch the front stages and provoke stall. Two families of rotating stall are identified by the model, consistent with experimental observations from Part I. The first family of rotating stall originates from hub corner separations developing on the stage 1 stator vanes. These gradually coalesce into a multicell rotating stall pattern confined to the hub region of the stator and its downstream rotor. The second family originates from regions of blockage associated with tip clearance flow over the stage 1 rotor blade. These also coalesce into a multicell rotating stall pattern of shorter length scale confined to the leading edge tip region. Some features of each of these two patterns are then explored as the variable stator vanes (VSVs) are mismatched further, pushing each region deeper into stall. The numerical predictions show a credible match with the experimental findings of Part I. This suggests that a RANS modeling approach is sufficient to capture some important aspects of part span rotating stall behavior.

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## Figures

Fig. 1

A schematic view of (a) the test compressor and (b) the unsteady computational domain

Fig. 2

Operating map for the test compressor

Fig. 3

Mean line assessment to “rank” the stalling effect of each configuration at a fixed inlet flow function

Fig. 4

Case A—total pressure profile

Fig. 5

Steady CFD for case A—mid passage entropy function

Fig. 6

Transient solution at S1 trailing edge, when vanes are moved from case Z to case A

Fig. 7

Transient solution at S1 trailing edge, 10% span, when vanes are moved from case Z to case A

Fig. 8

Transient solution at S1 trailing edge, when vanes are moved from case A to case D*

Fig. 9

Transient solution at S1 trailing edge, 10% span, when vanes are moved from case A to case D* (VSV adjustment denoted by solid black line)

Fig. 10

Spatial modes observed as stall forms

Fig. 11

Spatial modes (Stator 1)—case D*

Fig. 12

Axial velocity field at 20% span—case D*

Fig. 13

Case D*—distribution of 5th mode (hub and casing)

Fig. 14

Casing distribution case D* of stalling mode—comparison with experiment

Fig. 15

Transient solution at R1 leading edge, 99% span, when vanes are moved from case Z to case A

Fig. 16

Spatial modes (Rotor 1)—case A final

Fig. 17

Case A isosurface of λ2 for R1

Fig. 18

Rotor 1 inlet mass flow during calculation

Fig. 19

Transient solution at R1 leading edge, (a) 99% span and (b) 80% span, when vanes are moved from case A to case G

Fig. 20

Case G solution (a) axial velocity at IGV/R1 sliding plane and (b) isosurface of λ2 parameter

Fig. 21

Spatial modes (Rotor 1)—case G final

Fig. 22

Case G—distribution of 12th mode

Fig. 23

Axial distribution of case G stalling mode—comparison with experiment

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