Handbook of Turbomachinery Second Edition Revised - Ventech!

Much of the complexity of turbomachinery flow fields is directly
influenced by flow-path and component geometry. Geometric considerations
include the curvature and shape of the flow-path end walls, the spacing
between blade rows, blade pitch, and stagger. Other aspects of flow-path
geometry include the configuration of the blade rows, such as the use of
tandem blades, splitter blades, midspan dampers, and tip treatments. Of
equal importance are the myriad details related to blade shape, such as
thickness distribution, camber, lean, bow, sweep, scallop, twist, aspect ratio,
solidity, hub-to-tip radius ratio, radii of the leading and trailing edges, fillet
size, and tip clearance height. Blade cooling devices are also of importance;
the size and position of cooling holes in the blade surface will affect the
primary gas-path flow.
Thus, the flow behavior in turbomachinery components is quite
complex and is highly influenced by the flow-path geometry. A thorough
understanding of the effects of component and flow-path geometry will
allow the designer to use the resulting flow behavior to advantage. To
achieve this understanding and to perform the analyses necessary to
optimize the highly complex flow behavior requires the use of advanced flow
modeling technology.
Flow in Compression System Devices
Turbomachinery compression systems for aero engine applications can
employ various combinations of axial and centrifugal components. In
typical turbofan engines, an axial fan is positioned upstream, followed by a
flow splitter, which separates core and bypass streams. A multistage axial
compressor is positioned downstream in the core and may be followed by a
centrifugal compressor. Turboprop and turboshaft applications often utilize
centrifugal compressors exclusively.
All configurations of compression systems are characterized by
complex, three-dimensional flows, with adverse pressure gradients that
can produce flow separations. In addition, rotation, relative shroud motion,
tip leakage flows, shocks, shock–boundary-layer interactions, blade–endwall
interactions, and blade-row interactions all contribute to the structure
of the compressor flow field. Details of flow behavior specific to both axial
and centrifugal compressors will be examined in the following sections.
Flow in Axial Fans and Compressors
Axial fans and axial compressors are similar in many general respects, both
being compression devices with flow paths having relatively small radius
Copyright © 2003 Marcel Dekker, Inc.