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Handbook of Turbomachinery Second Edition Revised - Ventech!

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Turbine Section Losses<br />

A survey <strong>of</strong> 31 steam path audits indicated that the average section<br />

efficiency deterioration was 12.5% for the HP, 9.1% for the IP, and 3% for<br />

the LP. Most <strong>of</strong> the total loss in these turbines was caused by either leakage<br />

(about 50% <strong>of</strong> the total) or surface roughness (about 36% <strong>of</strong> the total). The<br />

worst leakage losses were from (1) radial spill strips, tip seals, or shroud<br />

seals, (2) diaphragm packing or interstage shaft packing, (3) end packing or<br />

shaft packing, and (4) miscellaneous leakages such as midspan balance hole<br />

plugs, inner shell, and seal rings.<br />

Figures 13 and 14 show typical leakage paths in impulse and reaction<br />

designs, respectively. Losses from leakage steam reentry between the<br />

Figure 13 Steam leakage losses for an impulse stage design.<br />

Copyright © 2003 Marcel Dekker, Inc.

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