Handbook of Turbomachinery Second Edition Revised - Ventech!

Figure 49 Modal diameters of a low-pressure turbine disk.
blading modifications and have been used to assess the potential payback
for such changes. In a number of cases, the need to replace worn or eroded
airfoils and the nature of the replacement have been established by the use
of three-dimensional CFD studies.
Prior to the early 1990s, flow analysis was performed primarily with
axisymmetric flow field computer programs (one-dimensional and later twodimensional
models). However, in the final stages of the LP turbine, the flow
undergoes a phase change because of steam expansion and is significantly
three-dimensional (Fig.51). Furthermore, this nonequilibrium phasechange
produces vapor subcooling (supersaturation), which can locally alter the
velocity triangles in the critical area near the leading edges of fixed as well as
rotating blades.
Copyright © 2003 Marcel Dekker, Inc.