0
TECHNICAL PAPERS

Numerical Investigation of the Effect of Different Back Sweep Angle and Exducer Width on the Impeller Outlet Flow Pattern of a Centrifugal Compressor With Vaneless Diffuser

[+] Author and Article Information
A. Hildebrandt

LTH, Lund Institute of Technology, Department of Energy Sciences, P.O. Box 118, 22100 Lund, Swedenandre.hildebrandt@de.manturbo.com

M. Genrup

LTH, Lund Institute of Technology, Department of Energy Sciences, P.O. Box 118, 22100 Lund, Sweden

J. Turbomach 129(2), 421-433 (Aug 09, 2006) (13 pages) doi:10.1115/1.2447873 History: Received June 17, 2006; Revised August 09, 2006

This paper presents a numerical investigation of the effect of different back sweep angles and exducer widths on the steady-state impeller outlet flow pattern of a centrifugal compressor with a vaneless diffuser. The investigations have been performed with commercial computational fluid dynamics (CFD) and in-house programmed one-dimensional (1D) codes. CFD calculations aim to investigate how flow pattern from the impeller is quantitatively influenced by compressor geometry parameters; thereby, the location of wake and its magnitude (flow angle and relative velocity magnitude) are analyzed. Results show that the increased back sweep impeller provides a more uniform flow pattern in terms of velocity and flow deviation angle distribution, and offers better potential for the diffusion process inside a vaneless (or vaned) diffuser. Secondary flux fraction and flow deviation angle from CFD simulation are implemented into the 1D two-zone program to improve 1D prediction results.

Copyright © 2007 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 4

(Left) Difference in relative velocity between the grid of 200,000 cells and 85,000 cells; (right) difference in relative velocity between the grid of 250,000 cells and 375,000 cells; N=0.8Ndes, m=1.8kg∕s

Grahic Jump Location
Figure 5

Calculated total efficiency distribution at impeller outlet at N=0.8Ndes; (left) m=2.24kg∕s; (right) m=1.549kg∕s

Grahic Jump Location
Figure 6

Diffuser absolute velocity distribution at N=0.8Ndes, m=1.80kg∕s: (left) radial position at r∕r2=1.015; (right) radial position at r∕r2=1.075

Grahic Jump Location
Figure 7

Impeller total efficiency and total pressure

Grahic Jump Location
Figure 8

Impeller static exit pressure and mass averaged slip factor

Grahic Jump Location
Figure 3

Relative velocity at impeller outlet: (top) Aachen measurements by Ziegler (4); (bottom) LTH calculations at N=0.8Ndes, m=1.8kg∕s, numerical results mirrored

Grahic Jump Location
Figure 2

Validation of total efficiency and total pressure ratio (impeller and 345mm diffuser), measurements reproduced from Ziegler (4)

Grahic Jump Location
Figure 1

Structured multi-block mesh of impeller, trailing, and leading edge details (complete vaneless diffuser not shown here)

Grahic Jump Location
Figure 13

Impeller relative flow diffusion: (left) 38@1000 (m=1.767kg∕s), (middle) 45@1000 (m=1.780kg∕s), and (right) 45@0925 (m=1.782kg∕s)

Grahic Jump Location
Figure 14

Mass flow distribution at impeller exit: (top) 45@0925, m=1.559kg∕s; (middle) 38@0925, m=1.556kg∕s; (bottom) 38@1000, m=1.549kg∕s

Grahic Jump Location
Figure 15

Absolute deviation of relative flow angle: (top) 45@0925, m=1.559kg∕s, (middle) 38@0925, m=1.556kg∕s, (bottom) 38@1000, m=1.549kg∕s

Grahic Jump Location
Figure 16

CFD post-processed data: mass averaged primary flow deviation (left) and secondary mass flux- and -area fraction (right)

Grahic Jump Location
Figure 17

1D impeller performance prediction without “tuning”: (thick lines) 45deg impeller, (thin lines) 38deg impeller, (solid line) 1.00 width, (dashed line) 0.925 width, (dotted line) 1.075 width

Grahic Jump Location
Figure 18

1D impeller performance prediction with “matched secondary flux”: (thick lines) 45deg impeller, (thin lines) 38deg impeller, (solid line) 1.00 width, (dashed line) 0.925 width, (dotted line) 1.075 width

Grahic Jump Location
Figure 19

(Left) ε-χ correlation from CFD: (right) ε-χ correlation from 1D program

Grahic Jump Location
Figure 20

1D impeller performance prediction tuned with ε and deviation flow angle distribution: (thick lines) 45deg impeller, (thin lines) 38deg impeller, (solid line) 1.00 width, (dashed line) 0.925 width, (dotted line) 1.075 width

Grahic Jump Location
Figure 21

Hub- and shroud angle distribution and meridional contour

Grahic Jump Location
Figure 9

Impeller swirl and static efficiency (impeller and 200mm diffuser)

Grahic Jump Location
Figure 10

Static pressure and static pressure recovery factor (200mm diffuser)

Grahic Jump Location
Figure 11

Relative deviation of relative flow angle (left) and relative deviation of relative velocity (right). Top: 38@1000, m=1.767kg∕s, second from top: 45@1000, m=1.780kg∕s, bottom: 45@0925, m=1.782kg∕s.

Grahic Jump Location
Figure 12

Impeller relative flow diffusion: (left) 38@1000 (m=2.237kg∕s), (middle) 45@1000 (m=2.248kg∕s), and (right) 45@0925 (m=2.235kg∕s)

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In