Handbook of Turbomachinery Second Edition Revised - Ventech!

Figure 34 Cross-section view of three turbine stages.
together, or cylindrical ‘‘wires’’ or rods inserted through a hole (usually in a
forged boss) in each blade foil [32, 33].
In order to add mechanical damping, some wire or rod-type lashing
wires are left loose in their holes, and there are also some shroud-type
connections that merely abut each other and are not permanently attached.
Continuous connections must make some provision to accommodate
thermal expansion of the connection. Shrouds and lacing wires sometimes
are introduced to decrease vibratory stresses, but can act as ‘‘crud traps.’’
Blades are connected at the root to the rotor or disk by several
configurationsasshowninFig.32.Thebladerootsmaybeofthe‘‘serrated’’
or ‘‘fir-tree’’ configuration, inserted into individual axial slots in the disk or
a similar serrated or T-shape, inserted into a continuous circumferential slot
in the disk (this requires a special insertion gap), or may comprise one or
several flat ‘‘fingers’’ fitting into circumferential slots in the disk and secured
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