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

Figure 3.1 shows working blades of turbines and various methods
of attaching them to the disks.
Of the dismountable bracings the most widely used is the one
with the "tree" lock (Fig. 3.1a). This is a union in which the
material of both the lock part of the blade and the disk is used
well; the small dimensions of the lock along the cii.cumference of
the disk enable the placement of a large number of blades on the
crown. Thanks to the free fit of the blade shaft in the groove of
the disk, the possibility of additional thermal stresses occuring
in the disk is reduced (due to the freedom of thermal strains).
Centrifugal force presses the blade shaft to the projection of the
disks all along the supporting surfaces; thus the blade is selfaligning
and a high degree of uniformity in load distribution is
ensured. These advantages of a "tree" lock are achieved by a high
degree of purity and precision in its manufacture (the disk grooves
are processed by drawing; the blade locks are obtained by accurate
milling or stretching with subsequent polishing). The free fit of
the blades facilitates their Installation.
Other types of dismountable bracings include cylindrical
(Fig. 3.1b) and forced locks (Fig. 3.1c). Iowever, these bracings
are inot widely used.
Fig. 3.2. Moving blades ol' a Fig. 3.3. Metal-ceramic inserts
turbine with bandage webs. in turbine housing to reduce the
radial gap between housing and
blade ends (on working revolutions).
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