Page 158 - Handbook of Energy Engineering Calculations

FIGURE 17 Steam turbine, electric generator, and gas turbine fit
into one compact building when all three machines are arranged on a
single shaft. Net result: Reduced site footprint and civil-engineering
work. (Power.)

Having the gas turbine, steam turbine, and generator all on one shaft

simplifies plant design and operation, and may lower first costs. When used
for large reheat cycles, as shown here, separate high-pressure (h-p),
intermediate-pressure (i-p), and low-pressure (l-p) turbine elements are all on

the same shaft as the gas turbine and generator. Modern high-technology
combined-cycle single-shaft units deliver a simple-cycle net efficiency of
38.5 percent for a combine-cycle net efficiency of 58 percent on a lower
heating value (LHV) basis.
The second important gas-turbine development worth noting is the dual-

fueled turbine located at the intersection of both gas and oil pipelines. Being
able to use either fuel gives the gas turbine greater opportunity to increase its