c. Construction. Turbines operate at speeds ranging from approximately
8000 to 60,000 rpm, depending on engine size. These high rotational speeds
induce highstress factors, which must be overcome for safe and efficient
operation. The turbine is constructed of a disk and blades, each of which is
carefully balanced and weighed. The blades (sometimes called buckets) are
attached to the disk by a fir tree design. This design provides for different
rates of expansion between blade and disk. The blades are attached axially by
fasteners or rivets. Turbine blades can be open at the ends or constructed to
form a shroud. Turbine temperature must be monitored closely during operation.
To exceed the maximum operating temperature could result in changing the temper
of the blades. This condition can change the pitch of the blades and render
the engine less efficient and dangerous to operate.
d. Exhaust. The exhaust gases pass radially outward through the
recouperator core into a collection plenum that is connected to the vehicle