Handbook of Turbomachinery Second Edition Revised - Ventech!

operating regimes; if a problem seems to arise at these off-design conditions,
another design of the blades and flow passages is prescribed and the routine
just described is repeated until a satisfactory compromise is found. Another
design point may have to be selected to resolve a problem.
The design process is thus seen to require accurate thermodynamic and
aerodynamic calculations in order to determine the changes in the flow
properties produced by each blade row. These calculations should be based
on the fundamental laws of motion, the Navier–Stokes equations, whenever
possible. In one form or another, these equations, which are reviewed in
Chapter 2, provide askeleton for the necessary design calculations.
Many of the computing techniques that are necessary to cope with
even the time-steady and inviscous forms of these equations are often not
readily available and recourse to other procedures is required. Any
treatment of compressor design methods must therefore make assumptions
about what computing resources are available to the designer. The kind and
the quality of any correlated experimental compressor data accessible must
also be presumed. (Many of the data used by current manufacturers of
compressors were obtained at their own expense and are often not generally
available.)
For the present purpose, it seemed reasonable to believe that the
greatest value of this chapter would obtain if it had two goals: first, to
describe and appraise the important design problems, and second, to
identify some of the better techniques that have been developed for
executing the calculations needed for compressor design.
The object of this chapter, therefore, is to select calculation procedures
for executing the aerodynamic design and development of those compressors
indicated in the opening paragraph. NASA SP [1] Lakshminarayana [2]
and Serovy [3] should be consulted for a more extensive review of the
fundamental aerodynamics of compressor design. Serovy [3] is especially
useful, because it contains a valuable bibliography concerning many aspects
of this subject.
Frequent distinctions are made between axial and centrifugal
compressors. We note at this time that the former are essentially curved
diffusers. The latter depend on centrifugal force for producing a significant
part of the increase in pressure.
The text first calls attention to important operating regimes that are
revealed by typical performance curves, or maps, of compressors. The
applicable equations of thermodynamics and aerodynamics are introduced
and discussed. Causes of energy degradation and inefficiences are examined.
The phenomena of choked flow and shock waves associated with
compressible flow are studied. Methods of selecting the magnitude of the
Copyright © 2003 Marcel Dekker, Inc.