Abstract
This present work is aimed at providing detailed understanding of the flow mechanisms in a highly loaded centrifugal compressor with different diffusers. Performance comparison between compressor stages with pipe diffuser and wedge diffuser was conducted by a validated flow solver. Stage with pipe diffuser achieved a better performance above 80 % rotating speed but a worse performance at lower rotating speeds near surge. Four operating points including the design point were analyzed in detail. The inherent diffuser leading edge of pipe diffuser could create a better operating condition for the downstream diffusion, which reduced the possibility of flow separation in discrete passages at design rotating speed. At 60 % rotating speed operating point, there was a large negative incidence angle. The sharp leading edge of pipe diffuser could largely accommodate this negative incidence as comparison of the round leading edge of wedge diffuser. As a result, a better performance was achieved in the pipe diffuser. At 60 % rotating speed near surge, performance of the pipe diffuser dropped below wedge diffuser. Total pressure loss of pipe diffuser exceeded that of the wedge diffuser due to the larger friction loss near wall at throat and ineffective static pressure recovery.
Funding statement: The work was financially supported by the National Natural Science Foundation of China (Project No: 51606187). This support is greatly appreciated.
Nomenclature
- A
area
- B
blockage
- R
radius
- D
diameter
- L
throat length
- N
number of pipes
- V
absolute velocity
- Cp
static pressure recovery coefficient, Cp=(ps – ps, ref)/(pt, ref – ps, ref)
- Cp,o
total pressure loss coefficient, Cp,o=(pt, ref – pt)/(pt, ref – ps, ref)
- CD
discharge coefficient, CD=Aeff/Ageo=1-B
- m
mass flow
- mchoke
choke mass flow
vorticity
resultant vorticity,
- θ
half of the divergence angle
- π
total to total pressure ratio
- Subscripts
- 1
impeller inlet
- 2
impeller outlet
- 3
diffuser leading edge
- 4
start of diffuser throat
- 4’
end of diffuser throat
- 5
diffuser passage outlet
- 6
diffuser outlet
- s
static
- t
total
- r
radial coordinate
- θ
tangential coordinate
- z
axial coordinate
- th
throat
- ref
reference (at impeller exit station 2)
- eff
effective
- Abbreviation
- LE
leading edge
- PS
pressure side
- SS
suction side
- OP
operating point
- CFD
computational fluid dynamics
References
1. Krain H. Review of centrifugal compressor’s application and development. ASME J Turbomach. 2005;127:25–34.10.1115/GT2003-38971Search in Google Scholar
2. Vrana JC, “Diffuser for centrifugal compressor”, U.S. Patent No. 1967/3333762, 1967.Search in Google Scholar
3. Kenny DP. A novel low-cost diffuser for high-performance centrifugal compressors. ASME J Eng Power. 1967;91:37–47.10.1115/1.3574671Search in Google Scholar
4. Blair LW, Russo CJ, “Compact diffusers for centrifugal compressors”, AIAA/SAE/ASME 16th Joint Propulsion Conference, Hartford Connecticut USA, June 30 -July 2, 1980, AIAA Paper No. 80-1077.10.2514/6.1980-1077Search in Google Scholar
5. Yaras MI. Effects of inlet conditions on the flow in a fishtail curved diffuser with strong curvature. ASME J Fluids Eng. 1996;118:772–78.10.1115/1.2835508Search in Google Scholar
6. Yaras MI. Flow measurements in a fishtail diffuser with strong curvature. ASME J Fluids Eng. 1999;121:410–17.10.1115/1.2822223Search in Google Scholar
7. Yaras MI, Orsi P, “Measurements of the effects of periodic inflow unsteadiness on the aerodynamics of a fishtail diffuser”, ASME Turbo Expo, Amsterdam Netherlands, June 3-6, 2002, ASME Paper No. GT2002-30455.10.1115/GT2002-30455Search in Google Scholar
8. Bourgeois JA, Robert JM, Roberts D, Savory E, Zhang C, “Experimental and numerical investigation of an aero-engine centrifugal compressor”, ASME Turbo Expo, Orlando USA, June 8-12, 2009, ASME Paper No. GT2009-59808.10.1115/GT2009-59808Search in Google Scholar
9. Kunte R, Jeschke P, Smythe C, “Experimental investigation of a truncated pipe diffuser with a tandem deswirler in a centrifugal compressor stage”, ASME Turbo Expo, Copenhagen Denmark, June 11-15, 2012, ASME Paper No. GT2012-68449.10.1115/GT2012-68449Search in Google Scholar
10. Kunte R, Schwarz P, Wilkosz B, Jeschke P, Smythe C, “Experimental and numerical investigation of tip clearance and bleed effects in a centrifugal compressor stage with pipe diffuser”, ASME Turbo Expo, Vancouver Canada, June 6-10, 2011, ASME Paper No. GT2011-45128.10.1115/GT2011-45128Search in Google Scholar
11. Zachau U, Buescher C, “Experimental investigation of a centrifugal compressor stage with focus on the flow in the pipe diffuser supported by particle image velocimetry(PIV) measurements”, ASME Turbo Expo, Berlin Germany, June 9-13, 2008, ASME Paper No. GT2008-51538.10.1115/GT2008-51538Search in Google Scholar
12. Zachau U, Niehuis R, “Experiential investigation of the flow in the pipe diffuser of a centrifugal compressor stage under selected parameter variations”, ASME Turbo Expo, Orlando USA, June 8-12, 2009, ASME Paper No. GT2009-59320.10.1115/GT2009-59320Search in Google Scholar
13. Grates DR, Jeschke P, Niehuis R, “Numerical investigation of the unsteady flow inside a centrifugal compressor stage with pipe diffuser”, ASME Turbo Expo, San Antonio USA, June 3-7, 2013, ASME Paper No. GT2013-95465.10.1115/1.4024873Search in Google Scholar
14. Gould KA, Tan CS, Macrorie M, “Characterization of unsteady impeller-blade loading in a centrifugal compressor with a discrete-passage diffuser”, ASME Turbo Expo, Montreal Canada, May 14-17, 2007, ASME Paper No. GT2007-28002.10.1115/GT2007-28002Search in Google Scholar
15. Peeters M, Sleiman M, “A numerical investigation of the unsteady flow in centrifugal stages”, ASME Turbo Expo, Munich Germany, May 8-11, 2000, ASME Paper No. GT2000-426.10.1115/2000-GT-0426Search in Google Scholar
16. Sugimoto T, Kawanishi T, Kumamaru H, Tohbe Y, “Performance investigation into supersonic diffuser for a high pressure centrifugal compressor”, ASME Turbo Expo, Dusseldorf Germany, June 16-20 2014, ASME Paper No. GT2014-25104.10.1115/GT2014-25104Search in Google Scholar
17. Skoch GJ, Prahst PS, Wernet MW, Wood JR, Strazisar AJ, “Laser anemometer measurements of the flow field in a 4:1 pressure ratio centrifugal impeller”, Technical Report ARLTR-1448, Army Research Laboratory, Lewis Research Center, U.S., 1997.10.1115/97-GT-342Search in Google Scholar
18. McKain TF, Holbrook GJ, “Coordinates for a high performance 4:1 pressure ratio centrifugal compressor”, NASA Contractor Report 204134, Detroit Diesel Allison, Indianapolis, Indiana, 1997.Search in Google Scholar
19. Han G, Lu XG, Zhao SF, Yang CW, Zhu JQ. Parametric studies of pipe diffuser on performance of a highly loaded centrifugal compressor. ASME, J Eng Gas Turbines Power. 2014;136:122604-1–122604-10.10.1115/1.4027867Search in Google Scholar
20. Marsan A, Trebinjac I, Coste S, Leroy G, “Numerical investigation of the flow in a radial vaned diffuser without and with aspiration”, ASME Turbo Expo, Copenhagen Denmark, June 11-15, 2012, ASME Paper No. GT2012-68610.10.1115/GT2012-68610Search in Google Scholar
21. Yang H, Nuernberger D, Nicke V, Weber A, “Numerical investigation of casing treatment mechanisms with a conservative mixed-cell approach”, ASME Turbo Expo, Atlanta USA, June 16-19, 2003, ASME Paper No. GT2003-38483.10.1115/GT2003-38483Search in Google Scholar
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