Handbook of Turbomachinery Second Edition Revised - Ventech!

Table 3(a) Steps in a Three-Dimensional Thermal Analysis
Step 1 Step 2 Step 3 Step 4
Obtain CAD
model
Generate 3D mesh
using
appropriate
mesher (Note:
The mesh
should be fine
enough to suit
the
requirements of
stress and
vibration
analyses to
follow.)
Apply appropriate
transient
boundary
conditions (Use
worst BCs
applicable
during cyclic
operation)
Perform transient
thermal analysis
& determine
worst
temperature
gradient and
regions of max.
temp. for stress
analysis
may result in changing the airfoil count or the struts in the system so that
excitation is avoided at critical operating speeds. The results of vibration
analysis permit the generation of a Campbell diagram (Fig. 15), which
portrays the natural frequencies of the blade as a function of speed (rpm or
percent of maximum). Centrifugal forces tend to raise the natural
frequencies while increasing temperatures tend to reduce them due to
Table 3(b) Steps in a Three-Dimensional Stress and Vibration Analysis
Step 1 Step 2 Step 3 Step 4
Refine mesh used
for thermal
analysis if
necessary, to
suit
requirements
for stress and
vibration
analyses.
Copyright © 2003 Marcel Dekker, Inc.
Interpolate from
results of
thermal analysis
to impose
temperatures at
all points on
newly generated
mesh.
Apply appropriate
BCs applicable
to stress
analysis.
Include body
forces as
necessary and
perform stress
analysis.
Determine
worst stress
location.
Generate modal
shapes and
perform
vibration
analysis by
using the same
mesh.