Design and Stress Analysis of Extraterrestrial ... - The Black Vault

In a number of cases a nondismountable rigid bracing of the
blades to the disk is accomplished by welding (Fig. 3.1d). Such
bracing has high strength characteristics. However, we must
correctly select blade and disk materials from the welding point of
view and also check the quality of the weld and the accuracy of the
blade installation before welding.
Blades can be attached to the disk by soldering with hightemperature
solder. With small turbine dimensions blades can be
cast together with the disks according to the models to be smelted.
To reduce gas overflows through the radial gap and increase turbine
efficiency, blades with bandage webs are used (Fig. 3.2). Bandage
webs increase the rigidity of the blade and improve its vibrational
character. However, they increase the stresses in the blade foil
from centrifugal forces. Sometimes with long blades bandaging
can be replaced by metal-ceramic inserts on the turbine housing
(Fig. 3.3), which, on working revolutions, enable the radial gap
between the turbine housing and the blade ends to be reduced to a
minimum..
Turbine disks and connection with the shaft
Turbine rotors operate at high circular velocities and working
temperatures. For these operating conditions, disk-type rotors
with one crown are usually used (two-crown disks are used sometimnes
in quiet turbines or in turbines with very short blades to reduce
weight).
In multistage turbines drum-disk rotors are used since lateral
stiffness in such turbines is high.
For reasops of strength, an attempt is made to make disks without
central openings (see "Stress Analysis of Disks"). When central
openings cannot be avoided, disks are strengthened by thickening
them near the openings.
227
)L