Page 265 - Steam Turbines Design, Applications, and Rerating

244 Chapter Thirteen

Figure 13.1 Dependence of the efficiency η of a control stage on the
blade height h, at constant U/c o .(η o = reference efficiency; U =
peripheral speed; c o = steam velocity.) (Asea Brown-Boveri, Baden,
Switzerland)
cost of the turbine and generator. This will be intuitively evident from
Tables 13.1 and 13.2.
The high-speed steam turbine is making inroads into both the low-
power range, where it is competing with the reciprocating steam
engine that previously dominated this field, and into the high-power
range where a new series of machines are providing an alternative to
the traditional low-speed sets.
Geared turbosets require less space so that costs for foundations and
buildings are reduced.
However, gear units are not limited to steam turbine-generator sets.
Thousands are in service as speed increasers, or step-up gears between
electric motor drivers and turbocompressors. Most of these incorporate