A highly supercharged gas-
turbine generation
system include a gas
turbine power
plant that is supercharged to a high
inlet pressure, preferably over about 1.15 pressure ratio and preferably includes a
transmission system with refrigerated transformers for increased output. The gas
turbine power
plant includes a precompressor that supercharges to a design pressure ratio of about 1.20 to 10, with a preferred pressure ratio of about 2. For high supercharging pressures, a pressure-
reducer is located downstream of the gas turbine to maintain turbine outlet pressure that is close to the
inlet pressure. The pressure-
reducer is preferably an expander, but can alternatively be an orifice. A torque-limiting
coupling on the shaft between the gas turbine and the generator prevents transient overload of the shaft. Capacity of the gas turbine
plant is preferably controlled by varying supercharging pressure. The expander preferably has variable-
pitch blades to allow efficient variation of turbine outlet pressure. For combined-cycle embodiments, a heat-
recovery steam generator (HRSG) may be placed between the gas turbine and a downstream expander. For highest
combined cycle output, a single-pressure
steam system with high
inlet temperature to the HRSG is preferred. The high temperature is preferably provided by supplemental firing between the gas turbine and the HRSG. An expander may be inserted between the supplemental firing and the HRSG to further improve
cycle efficiency and to reduce pressure in the HRSG. For retrofit applications with limited supercharging, a
refrigeration system for generator cooling may be added to increase generator output to match that available from the supercharged gas turbine.