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TECHNICAL PAPERS

An Empirical Prediction Method for Secondary Losses in Turbines—Part I: A New Loss Breakdown Scheme and Penetration Depth Correlation

[+] Author and Article Information
M. W. Benner1

National Research Council of Canada, Institute for Aerospace Research, Ottawa, ON K1A 0R6, Canadamichael.benner@nrc-cnrc.gc.ca

S. A. Sjolander

Department of Mechanical and Aerospace Engineering, Carleton University, Ottawa, ON K1S 5B6 Canada

S. H. Moustapha

 Pratt and Whitney Canada, Ltd., Longueuil, PQ, J4G 1A1 Canada

To maintain a given airfoil loading while increasing the chord requires a proportional increase in the airfoil spacing.

1

Author to whom correspondence should be addressed.

J. Turbomach 128(2), 273-280 (Feb 01, 2005) (8 pages) doi:10.1115/1.2162593 History: Received October 01, 2004; Revised February 01, 2005

Despite its wide use in meanline analyses, the conventional loss breakdown scheme is based on a number of assumptions that are known to be physically unsatisfactory. One of these assumptions states that the loss generated in the airfoil surface boundary layers is uniform across the span. The loss results at high positive incidence presented in a previous paper (Benner, M. W., Sjolander, S. A., and Moustapha, S. H., 2004, ASME Paper No. GT2004-53786.) indicate that this assumption causes the conventional scheme to produce erroneous values of the secondary loss component. A new empirical prediction method for secondary losses in turbines has been developed, and it is based on a new loss breakdown scheme. In the first part of this two-part paper, the new loss breakdown scheme is presented. Using data from the current authors’ off-design cascade loss measurements, it is shown that the secondary losses obtained with the new scheme produce a trend with incidence that is physically more reasonable. Unlike the conventional loss breakdown scheme, the new scheme requires a correlation for the spanwise penetration depth of the passage vortex separation line at the trailing edge. One such correlation exists (Sharma, O. P., and Butler, T. L., 1987, ASME J. Turbomach., 109, pp. 229–236.); however, it was based on a small database. An improved correlation for penetration distance has been developed from a considerably larger database, and it is detailed in this paper.

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Copyright © 2006 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Cascade geometry and measurement locations

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Figure 2

Loss decomposition using the conventional loss breakdown scheme for (a) LS3, (b) LS2 (reproduced from Benner (2))

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Figure 3

Suction surface definition for the new loss breakdown scheme

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Figure 4

Loss decomposition using the new loss breakdown scheme for (a) LS3, (b) LS2

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Figure 5

Comparison of the mixed-out secondary losses at off-design incidence for LS2 and LS3 as obtained from the new loss breakdown scheme

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Figure 6

Evaluation of the penetration depth correlation of Sharma and Butler

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Figure 7

Evaluation of the new penetration depth correlation

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