The paper presents detailed measurements of the incompressible flow at the exit of a large-scale 90-degree curved diffuser with strong curvature and significant stream-wise variation in the cross-section aspect ratio. The diffuser flow path approximates the so-called fish-tail diffuser utilized on small gas turbine engines for the transition between the centrifugal impeller and the combustion chamber. Five variations of the inlet boundary layer are considered. The results provide insight into several aspects of the diffuser flow including: the effect of flow turning on diffusion performance; the dominant structures influencing the flow development in the diffuser; and the effect of the inlet boundary layer integral parameters on the diffusion performance and the exit velocity field. The three-dimensional velocity distribution at the diffuser exit is found to be sensitive to circumferentially uniform alterations to the inlet boundary layer. In contrast, circumferential variations in the inlet boundary layer are observed to have only secondary effects on the velocity field at the diffuser exit. The static pressure recovery is observed to be comparable to the published performance of conical diffusers with equivalent included angle and area ratios. Furthermore, both the static pressure recovery and the total pressure losses are observed to be relatively insensitive to variations in the inlet boundary layer. The physical mechanisms dominating the flow development in the diffuser are discussed in light of these observations.

1.
Blair, L. W., and Russo, C. J., 1980, “Compact Diffusers for Centrifugal Compressors,” AIAA-80-1077, presented at the AIAA/SAE/ASME 16th Joint Propulsion Conference.
2.
Cutler, A. D., and Johnston, J. P., 1981, “The Effects of Inlet Conditions on the Performance of Straight-Walled Diffusers at Low Subsonic Mach Numbers–A Review,” Stanford University Report PD-26.
3.
Dolan, F. X., and Runstadler, P. W., 1973, “Pressure Recovery Performance of Conical Diffusers at High Subsonic Mach Numbers,” NASA Contractor Report 2299.
4.
Fox
R. W.
, and
Kline
S. J.
,
1962
, “
Flow Regimes in Curved Subsonic Diffusers
,”
ASME Journal of Basic Engineering
, Vol.
84
, pp.
303
316
.
5.
Kenny, D. P., 1968, “A Novel Low Cost Diffuser for High Performance Centrifugal Compressors,” ASME 68-GT-38.
6.
Klein
A.
,
1981
, “
REVIEW: Effects of Inlet Conditions on Conical-Diffuser Performance
,”
ASME JOURNAL OF FLUIDS ENGINEERING
, Vol.
103
, pp.
250
257
.
7.
McMillan, O. J., 1982, “Mean-Flow Measurements of the Flow Field Diffusing Bend,” NASA Contractor Report 3634.
8.
Moffat
R. J.
,
1982
, “
Contributions to the Theory of Single-Sample Uncertainty Analysis
,”
ASME JOURNAL OF FLUIDS ENGINEERING
, Vol.
104
, pp.
250
260
.
9.
Parsons
D. J.
, and
Hill
P. G.
,
1973
, “
Effects of Curvature on Two-Dimensional Diffuser Flow
,”
ASME JOURNAL OF FLUIDS ENGINEERING
, Vol.
95
, pp.
349
360
.
10.
Reeves, G. B., 1977, “Design and Performance of Selected Pipe-Type Diffusers,” ASME-77-GT-104.
11.
Sagi
C. J.
, and
Johnston
J. P.
,
1967
, “
The Design and Performance of Two-Dimensional, Curved Diffusers
,”
ASME Journal of Basic Engineering
, Vol.
89
, pp.
715
731
.
12.
Saroch, M. F., 1996, “Contributions to the Study of Turbomachinery Aerodynamics, Part I: Design of a Fish-Tail Diffuser Test Section, Part II: Computations of the Effects of AVDR on Transonic Turbine Cascades,” Masters thesis, Department of Mechanical and Aerospace Engineering, Carleton University.
13.
Wellborn, S. R., Reichert, B. A., and Okiishi, T. H., 1992, “An Experimental Investigation of the Flow in a Diffusing S-Duct,” AIAA-92-3622 presented at the AIAA/SAE/ASME/ASEE 28th Joint Propulsion Conference.
This content is only available via PDF.
You do not currently have access to this content.