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Handbook of Turbomachinery Second Edition Revised - Ventech!

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Figure 25 Percentage stage reactions <strong>of</strong> nuclear steam turbines.<br />

centrifugal forces on the steam flow. If this was not done, too much flow<br />

would migrate to the blade tips and reduce stage efficiency. Bowed blades,<br />

for a given mean diameter reaction, increase the base section reaction and<br />

reduce the tip reaction [104].<br />

Flow Through a Stage (Velocity Triangles)<br />

‘‘Velocity triangles’’ for an impulse stage are shown in Fig. 26. This vector<br />

representation is an important tool used to understand the flow <strong>of</strong> steam<br />

through real turbine stages. The stationary blades (or nozzles) accelerate the<br />

flow by altering the flow area and turn the flow toward the rotating blades.<br />

The velocity <strong>of</strong> steam leaving the stationary blade, V1, is approximately<br />

equal to the theoretical steam velocity V0, which would be the velocity <strong>of</strong> the<br />

Copyright © 2003 Marcel Dekker, Inc.

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