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Handbook of Turbomachinery Second Edition Revised - Ventech!

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Figure 10 Conical diffuser performance chart. (Replotted from Ref. 8).<br />

This can be used to calculate the diffuser loss when compressibility is not<br />

important. If the Mach number at the inlet to the diffuser is above 0.2–0.3,<br />

this can be used as a starting guess, and the actual value can be determined<br />

by iteration. The diffuser recovery is a function <strong>of</strong> the inlet Mach number,<br />

blockage, and geometry (straight, curved, conical, or annular); it is critical<br />

to use the correct diffuser performance chart when estimating diffuser<br />

recovery.<br />

Exit Losses<br />

Exit losses are quite simple. If the kinetic energy <strong>of</strong> the flow exiting the<br />

diffuser is used in following stages, or contributes to thrust, the exit losses<br />

are zero. If, however, the diffuser discharge energy is not utilized, the exit<br />

loss is the exit kinetic energy <strong>of</strong> the flow. For this case,<br />

Dp 0 exit ¼ p0 dis pdis ð39Þ<br />

Nondimensional Parameters<br />

Turbine performance is dependent on rotational speed, size, working fluid,<br />

enthalpy drop or head, and flow rate. To make comparisons between<br />

Copyright © 2003 Marcel Dekker, Inc.

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