Steam Turbines and Gas Expanders

Turbines utilize the expansion of steam or a gas to deliver power to a rotating shaft. Salient features of such equipment are 

TABLE 4.2. Checklist for Selection of Motors Motor Data 

Type of motor (cage, wound-rotor, synchronous, or lc). 

Time rating (continuous, short-timc, intermittent). 

Class of insulation Armature.. . Field.. . Rotor of w-r motor.. . 

Full- or reduced-voltage or part-winding starting (ac). 

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Turboexpanders are expansion turbines, rotating maehines similar to steam turbines. Commonly, the terms expansion turbines and turboexpanders speeifieally exelude steam turbines and eombustion gas turbines. Turboexpanders (Figure 1-1) ean also be eharaeterized as modern rotating deviees that eonvert the pressure energy of a gas or vapor stream into meehanieal work as the gas or vapor expands through the turbine. If ehilling the gas or vapor stream is the main... 

A detailed design for the compressors would be required to determine the inlet and outlet velocities for the steam in the steam turbine, and the tail gas in the tail-gas expander. In this process, tail-gas expansion typically provides about 80% of the required energy with an efficiency in the production of shaft energy of less than 25%. 

The gas turbine power plant which has revolutioni2ed aviation derives basically from the steam turbine adapted to a different working fluid. The difference is cmcial with respect to fuel because steam can be generated by any heat source, whereas the gas turbine requires a fuel that efficiently produces a very hot gas stream and is also compatible with the turbine itself. The hot gas stream results from converting chemical energy in fuel directly and continuously by combustion in compressed air. It is expanded in a turbine to produce useful work in the form of jet thmst or shaft power. 

Radial fit bolts are a special feature used in all types of turbomachinery. They are of increasing importance to users that are both reliability-minded and concerned about life-cycle costs. The radial fit coupling bolt was originally developed for coupling steam turbine shafts by Pilgrim International in Oldham, UK. It is equally useful to coupling other equipment, including, of course, hot gas expander shafts. 

A train that generates only eleetrieity from the hot flue gas is ealled a Total Power Generation (TPG) train. A TPG train eonsists of a power reeovery expander, gear, generator, and sometimes a steam turbine (Figure 6-39). The valve arrangement for a TPG train requires speeial attention beeause the train operation and the proeess operation are independent. 

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