This is Part 1 of a two-part paper considering the performance of radial diffusers for use in a high-performance centrifugal compressor. Part 1 reports on discrete-passage diffusers (shown in Fig. 1) while Part 2 describes a test of a straight-channel diffuser designed for equivalent duty. Two builds of discrete-passage diffuser were tested, with 30 and 38 separate passages. Both the 30 and 38 passage diffusers investigated showed comparable range of unstalled operation and similar level of overall diffuser pressure recovery. The paper concentrates on the influence of inlet flow conditions on the pressure recovery and operating range of radial diffusers for centrifugal compressor stages. The flow conditions examined include diffuser inlet Mach number, flow angle, blockage, and axial flow nonuniformity. The investigation was carried out in a specially built test facility, designed to provide a controlled inlet flow field to the test diffusers. The facility can provide a wide range of diffuser inlet velocity profile distortion and skew with Mach numbers up to unity and flow angles of 63 to 75 deg from the radial direction. The consequences of different averaging methods for the inlet total pressure distributions, which are needed in the definition of diffuser pressure recovery coefficient for nonuniform diffuser inlet conditions, were also assessed. The overall diffuser pressure recovery coefficient, based on suitably averaged inlet total pressure, was found to correlate well with the momentum-averaged flow angle into the diffuser. Furthermore, the pressure recovery coefficient was found to be essentially independent of the axial distortion at diffuser inlet, and the Mach number, over the wide flow range (from maximum flow to the beginning of flow instabilities) investigated. It is thus shown that the generally accepted sensitivity of diffuser pressure recovery performance to inlet flow distortion and boundary layer blockage can be largely attributed to inappropriate quantification of the average dynamic pressure at diffuser inlet. Use of an inlet dynamic pressure based on availability or mass-averaging in combination with definition of inlet flow angle based on mass average of the radial and tangential velocity at diffuser inlet removes this sensitivity. [S0889-504X(00)00101-X]

Issue Section:
Technical Papers
Keywords:
compressors, subsonic flow, channel flow, Mach number, pressure
Topics:
Diffusers, Flow (Dynamics), Pressure, Mach number, Compressors
1.
Deniz
,
S.
,
Greitzer
,
E. M.
, and
Cumpsty
,
N. A.
,
2000
, “
Effects of Inlet Flow Field Conditions on the Performance of Centrifugal Compressor Diffusers: Part 2—Straight-Channel Diffuser
,”
ASME J. Turbomach.
,
122
, pp.
11
–
21
.
2.
Japikse, D., 1996, “Centrifugal Compressor Design and Performance,” Concepts ETI, Inc., Norwich, VT.
3.
Japikse, D., 1984, “Turbomachinery Diffuser Design Technology,” The Design Technology Series (DTS-1), Concepts ETI, Inc., Norwich, VT.
4.
Japikse, D., 1987, “The Technology of Centrifugal Compressors: A Design Approach and New Goals for Research,” Flow in Centrifugal Compressors. Von Karman Institute, Lecture Notes.
5.
Hunziker
,
R.
, and
Gyarmathy
,
G.
,
1994
, “
The Operational Stability of a Centrifugal Compressor and Its Dependence on the Characteristics of the Subcomponents
,”
ASME J. Turbomach.
,
116
, pp.
250
–
259
.
6.
Elder
,
R. L.
, and
Gill
,
M. E.
,
1985
, “
A Discussion of the Factors Affecting Surge in Centrifugal Compressors
,”
ASME J. Eng. Gas Turbines Power
,
107
, pp.
499
–
506
.
7.
Inoue
,
M.
, and
Cumpsty
,
N. A.
,
1984
, “
Experimental Study of Centrifugal Impeller Discharge Flow in Vaneless and Vaned Diffusers
,”
ASME J. Eng. Gas Turbines Power
,
106
, pp.
455
–
467
.
8.
Haupt
,
U.
,
Seidel
,
U.
,
Abdelhamid
,
A. N.
, and
Rautenberg
,
M.
,
1988
, “
Unsteady Flow in a Centrifugal Compressor With Different Types of Vaned Diffusers
,”
ASME J. Turbomach.
,
110
, No.
3
, pp.
293
–
302
.
9.
Clements, W. W., 1987, “A Theoretical and Experimental Study of Diffusion Level, in Centrifugal Compressor Stages,” Dissertation. Faculty of Engineering, University of Belfast.
10.
Japikse, D., and Osborne, C., 1986, “Optimization of Industrial Centrifugal Compressors: Part 6B: Studies in Component Performance—Eight Design Cases From 1972 to 1982,” ASME Paper No. 86-GT-222.
11.
Stein, W., and Rautenberg, M., 1985, “Flow Measurements in Two Cambered Vane Diffusers With Different Passage Widths,” ASME Paper No. 85-GT-46.
12.
Kano
,
F.
,
Tazawa
,
N.
, and
Fukao
,
Y.
,
1982
, “
Aerodynamic Performance of Large Centrifugal Compressors
,”
ASME J. Eng. Power
,
104
,
No. 2
No. 2
.
13.
Rodgers, C., 1982. “The Performance of Centrifugal Compressor Channel Diffusers,” ASME Paper No. 82-GT-10.
14.
Yoshinaga
,
Y.
,
Gyobu
,
I.
,
Mishina
,
H.
,
Koseki
,
F.
, and
Hishida
,
N.
,
1980
, “
Aerodynamic Performance of a Centrifugal Compressor With Vaned Diffusers
,”
ASME J. Fluids Eng.
,
102
, pp.
486
–
493
.
15.
Kenny, D. P., 1972, “A Comparison of the Predicted and Measured Performance of High Pressure Ratio Centrifugal Compressor Diffusers,” ASME Paper No. 72-GT-54.
16.
Krain
,
H.
,
1981
, “
A Study on Centrifugal Impeller and Diffuser Flow
,”
ASME J. Eng. Power
,
103
, pp.
1
–
10
.
17.
Krain, H., 1984, “Experimental Observation of the Flow in Impellers and Diffusers,” Flow in Centrifugal Compressors, Von Karman Institute for Fluid Dynamics, Lecture Series No. 1984-07.
18.
Dawes
,
W. N.
,
1995
, “
A Simulation of the Unsteady Interaction of a Centrifugal Impeller With Its Vaned Diffuser: Flow Analysis
,”
ASME J. Turbomach.
,
117
, pp.
213
–
222
.
1.
Baghdadi
,
S.
, 1976, “The Effect of Rotor Blade Wakes on Centrifugal Compressor Diffuser Performance—A Comparative Experiment,” Centrifugal Compressor and Pump Stability, and Surge, ASME, New York, pp. 121–138:
2.
1977
,
ASME J. Fluids Eng.
,
99
, No.
1
, pp.
45
–
52
.
1.
Baghdadi
,
S.
, and
McDonald
,
A. T.
,
1975
, “
Performance of Three Radial Vaned Diffusers With Swirling Transonic Flow
,”
ASME J. Fluids Eng.
,
97
, pp.
155
–
173
.
2.
Casey, M. V., Eisele, K., Muggli, F. A., Gu¨lich, J., and Schachenmann, A., 1995, “Flow Analysis in a Pump Diffuser, Part 2: Validation of a CFD Code for Steady Flow,” Numerical Simulations in Turbomachinery, ASME FED-Vol. 227, pp. 135–143.
3.
Dalbert, P., Gyarmathy, G., and Sebestyen, A., 1993, “Flow Phenomena in a Vaned Diffuser of a Centrifugal Stage,” ASME Paper No. 93-GT-53.
4.
Teipel, I., Wiedermann, A., and Evers, W., 1992, “Viscous Flows in Centrifugal Compressor Diffusers at Transonic Mach Numbers,” ASME Paper No. 92-GT-48.
5.
Klein
,
A.
,
1981
, “
Review: Effects of Inlet Conditions on Conical-Diffuser Performance
,”
ASME J. Fluids Eng.
,
103
, pp.
250
–
257
.
6.
Al-Mudhafar, M. M., Ilyas, M., and Bhinder, F. S., 1982, “Investigation of Flows in Rectangular Diffusers With Inlet Flow Distortion,” ASME Paper No. 82-GT-67.
7.
Bhinder, F. S., Al-Mudhafar, M. M., and Ilyas, M., 1984, “Further Data on the Performance of a Rectangular Diffuser in Distorted Inlet Flows,” ASME Paper No. 84-GT-64.
8.
Wolf
,
S.
, and
Johnston
,
J. P.
,
1969
, “
Effects of Nonuniform Inlet Velocity Profiles on Flow Regimes and Performance in Two-Dimensional Diffusers
,”
ASME J. Basic Eng.
,
91
, pp.
462
–
474
.
9.
Masuda, H., Ariga, I., and Watanabe, I., 1971, “On the Behavior of Uniform Shear Flow in Diffusers and Its Effects on Diffusers Performance,” ASME J. Eng. Power, pp. 377–385.
10.
Runstadler, P. W. J., Dolan, F. X., and Dean, R. C. J., 1975, “Diffuser Data Book,” Technical Note TN-186, Create, Inc., Hanover, NH.
11.
Dutton
,
J. C.
,
Piemsomboon
,
P.
, and
Jenkins
,
P. E.
,
1986
, “
Flowfield and Performance Measurements in a Vaned Radial Diffuser
,”
ASME J. Fluids Eng.
,
108
, pp.
141
–
147
.
12.
Filipenco, V. G., 1991, “Experimental Investigation of Flow Distortion Effects on the Performance of Radial Discrete-Passage Diffusers,” MIT GTL Report No. 206. Sept., Cambridge, Massachusetts, Dissertation.
13.
Livesey
,
J. L.
, and
Hugh
,
T.
,
1966
, “
Suitable Mean Values in One-Dimensional Gas Dynamics
,”
J. Mech. Eng. Sci.
,
8
, No.
4
, pp.
374
–
383
.
14.
Mishina, H., and Nishida, H., 1984, “Effect of Relative Velocity Distribution on Efficiency and Exit Flow Angle,” ASME Paper No. 83-GT-74.
15.
Johnston, J. M., 1993, “Stall Onset Observations of a Discrete Passage Diffuser,” MIT GTL Report No. 217, April, Cambridge, MA, M. Sc. Thesis.
16.
Casey, M. V., Eisele, K., Zhang, Z., Gu¨lich, J., and Schachenmann. A., 1995, “Flow Analysis in a Pump Diffuser, Part 1: LDA and PTV Measurements of the Unsteady Flow,” Laser Anemometry, ASME FED-Vol. 229, pp. 89–100.
Copyright © 2000
 by ASME
You do not currently have access to this content.