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Handbook of Turbomachinery Second Edition Revised - Ventech!

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pressure levels. As long as combustion chamber pressure targets continue to<br />

rise, and the desire for lighter vehicle tankage results in decreasing tank<br />

pressure budgets, the low-power hydraulic turbine drive concept will<br />

continue to be viable, especially for pump applications that involve highly<br />

reactive fluids.<br />

I would like to say a word regarding references outside this book for<br />

additional reading. The National Aeronautics and Space Administration<br />

publishes two documents that should satisfy most readers’ needs. The first is<br />

a special publication identified as NASA SP-8110 and is titled (appropriately<br />

enough) Liquid Rocket Engine Turbines 1. Besides touching on a<br />

variety <strong>of</strong> specialized considerations relating to design details, this document<br />

also presents a design method that is both simple and successful. The<br />

method consists <strong>of</strong> computing total fluid states at the inlet and exit <strong>of</strong> nozzle<br />

and blade rows, and modifying isentropic computations using lumped<br />

parameters known as loss coefficients. These loss coefficients account for the<br />

major mechanisms <strong>of</strong> nozzle and blade row losses. Considerable test data<br />

exist to substantiate them, and this method has been used to design quite a<br />

number <strong>of</strong> successful turbines for both production and research and<br />

development work. This method was introduced by H. D. Emmert.<br />

Incidentally, although Emmert’s method and data were originally intended<br />

for gas turbines, firsthand experience shows that they are also applicable to<br />

hydraulic turbines, where the designer substitutes the total liquid head for<br />

total enthalpy in the design procedure.<br />

The other reference that I heartily recommend is another NASA<br />

special publication. This one is identified as NASA SP-290, titled Turbine<br />

Design and Application 2. This document is a three-volume set. It is written<br />

by the Lewis Research Center and covers all major aspects <strong>of</strong> turbine<br />

technology in considerable detail. Most interesting to this author is the<br />

derivation <strong>of</strong> expressions that are analogous to Emmert’s loss coefficients.<br />

ROCKET PROPULSION SYSTEMS—PUMPING ELEMENTS<br />

This section begins our discussion <strong>of</strong> pumping elements in rocket propulsion<br />

systems. In this section, we will discuss the most common types <strong>of</strong> pumping<br />

devices used in rocket systems. These are the centrifugal pump, the axialflow<br />

pump, and the inducer. Our discussions will include areas in which the<br />

above three types <strong>of</strong> pumps are similar, areas in which they differ markedly,<br />

and examples <strong>of</strong> the applicability <strong>of</strong> each in rocket systems.<br />

Before we discuss the various pumping machinery in detail, a few<br />

general remarks regarding the rocket engine system and the pump’s role in<br />

that system are appropriate.<br />

Copyright © 2003 Marcel Dekker, Inc.

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