Research Papers

Some Lessons Learned

[+] Author and Article Information
N. A. Cumpsty

 Imperial College, London, UK SW7 2AZ

Radial mixing is given some emphasis here because it was an exceptional period of intellectual competition carried out with great openness and courtesy. Those involved recall it as a stimulating and enjoyable episode a quarter century later.

Describing the experiments as in error is deliberately provocative. However, the interpretation of the experimental results and the assessment of what geometric features of the rig were important were certainly in error. Arguably so too was the CFD modeling, since no one bothered, or was able, to include the clearance gap in their calculations.

J. Turbomach 132(4), 041018 (May 11, 2010) (7 pages) doi:10.1115/1.4001222 History: Received July 26, 2009; Revised July 27, 2009; Published May 11, 2010; Online May 11, 2010

This paper looks at some familiar results, concepts, and ideas in a different way, drawing out some common unifying threads. The topics addressed are one-, two-, and three-dimensions; axisymmetry and its breakdown; gaps and leakage paths; and computation fluid dynamics (CFD) and the limitation of perfection. Certain overlapping issues come up in each of the topic areas.

Copyright © 2010 by American Society of Mechanical Engineers
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Figure 1

Two-dimensional representation, blade-to-blade surface of revolution on the left, and meridional (throughflow) plane on the right

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Figure 2

Surface flow visualization (upper two pictures), and CFD (lower two pictures) for a compressor blade (left) and stationary endwall (right) at zero incidence (7)

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Figure 3

Idealized stage characteristics for a three-stage, high-speed compressor

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Figure 4

Blade tip stagger for random variation in stagger without gas loads: (a) for flow unstarted, (b) for an intermediate condition, and (c) for flow started. Note different scale for (b) (13)

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Figure 5

Efficiency versus normalized flow rate for a supersonic rotor having small levels of misstagger (13)

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Figure 6

CFD and measurement of pressure ratio for NASA Rotor 37. The numbers provide a key to the authors of the different codes used (15)

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Figure 7

Variation in rotor hub leakage and its effect on stagnation pressure ratio across the rotor (16). Reduced gap and nominal gap refer to zero net flow from the gap; other cases are for net outflow.

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Figure 8

Computed flow in NASA Rotor 35 showing leakage flow entering hub separation region (16)




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