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Handbook of Turbomachinery Second Edition Revised - Ventech!

Handbook of Turbomachinery Second Edition Revised - Ventech!

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Figure 15h Cross-section <strong>of</strong> a typical axial flow turbopump.<br />

stator row accepts the rotor’s outlet flow, diffuses that flow to convert<br />

kinetic energy into static head, and turns the flow field so that its direction<br />

matches the inlet direction requirement <strong>of</strong> the next rotor. Thus, the stator<br />

row removes most <strong>of</strong> the swirl from the rotor outlet flow field, and this swirl<br />

energy is converted to static head as efficiently as possible. This pattern is<br />

repeated in the subsequent stages <strong>of</strong> the pump. Although it is not apparent<br />

from the figure, each <strong>of</strong> the seven axial stages is <strong>of</strong> identical hydrodynamic<br />

design. Thus, each stage contributes approximately 1/7 <strong>of</strong> the total pump<br />

head rise (less the inducer head rise). The final axial stage delivers the<br />

pumped flow through a radial diffuser and into a discharge volute that are<br />

identical in character with those to be found in centrifugal pumps.<br />

The axial-flow pump and centrifugal pump operate on exactly the<br />

same physical principles. However, differences in their geometry make them<br />

substantially different in their detailed performance characteristics. The<br />

remainder <strong>of</strong> this section will highlight the factors that distinguish axial-flow<br />

pumps from their centrifugal-flow cousins.<br />

The most obvious physical difference between the centrifugal and axial<br />

configurations can be seen from a study <strong>of</strong> Fig. 15(h) and 15. It will be noted<br />

that, for a given machine overall diameter, the inlet flow area <strong>of</strong> the axial<br />

pump is substantially larger than that <strong>of</strong> the centrifugal pump. This leads us<br />

to a first conclusion that, for a given size class <strong>of</strong> pump, the flow rates<br />

Copyright © 2003 Marcel Dekker, Inc.

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