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Research Papers

Experiments and Computations on Large Tip Clearance Effects in a Linear Cascade

[+] Author and Article Information
Richard Williams, David Gregory-Smith, Grant Ingram

 University of Durham, South Road, Durham DH1 3LE, UK

Li He1

 University of Durham, South Road, Durham DH1 3LE, UK

1

Present address: Department of Engineering Science, Oxford University.

J. Turbomach 132(2), 021018 (Jan 20, 2010) (10 pages) doi:10.1115/1.3104611 History: Received October 14, 2008; Revised November 18, 2008; Published January 20, 2010; Online January 20, 2010

Large tip clearances typically in the region of 6% exist in the high pressure (HP) stages of compressors of industrial gas turbines. Due to the relatively short annulus height and significant blockage, the tip clearance flow accounts for the largest proportion of loss in the HP. Therefore increasing the understanding of such flows will allow for improvements in design of such compressors, increasing efficiency, stability, and the operating range. Experimental and computational techniques have been used to increase the physical understanding of the tip clearance flows through varying clearances in a linear cascade of controlled-diffusion blades. This paper shows two unexpected results. First the loss does not increase with clearances greater than 4% and second there is an increase in blade loading toward the tip above 2% clearance. It appears that the loss production mechanisms of the pressure driven tip clearance jet do not increase as the clearance is increased to large values. The increase in blade force is attributed to the effect of the strong tip clearance vortex, which does not move across the blade passage to the pressure surface, as is often observed for high stagger blading. These results may be significant for the design of HP compressors for industrial gas turbines.

Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 3

Cascade inlet conditions

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Figure 4

0% TC, 1.2Cx, experimental loss (Cpo)

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Figure 5

1% TC, 1.2Cx, experimental loss (Cpo)

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Figure 6

2% TC, 1.2Cx, experimental loss (Cpo)

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Figure 7

6% TC, 1.2Cx, experimental loss (Cpo)

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Figure 8

Pitch mass averaged yaw 1.2Cx

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Figure 9

Pitch mass averaged Cpo1.2Cx

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Figure 10

Blade pressure coefficient (Cp) at 50% span

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Figure 11

Blade pressure coefficient (Cp) at 95% span

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Figure 12

Blade pressure coefficient (Cp) at 98% span

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Figure 13

Blade force coefficient

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Figure 14

Total blade force versus TC, CFD, and experimental data

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Figure 15

Example of mesh for 6% TC at 0.9Cx

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Figure 16

Example mesh for k-plane

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Figure 17

0% TC, 1.2Cx, CFD loss (Cpo)

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Figure 18

1% TC, 1.2Cx, CFD loss (Cpo)

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Figure 19

2% TC, 1.2Cx, CFD loss (Cpo)

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Figure 20

6% TC, 1.2Cx, CFD loss (Cpo)

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Figure 21

CFD study, 1.2Cx CFD yaw angle with varying TC

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Figure 22

CFD study, 1.2Cx CFD total pressure loss with varying TC

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Figure 23

CFD study, increase in loss through cascade

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Figure 24

Mass flow rate per passage

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Figure 25

CFD study, blade force coefficient 6% tip clearance

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Figure 26

CFD study, 6% TC Cpo loss contour plots

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Figure 27

CFD, 6% TC, blade pressure profile

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