4.1 Gas turbine power plants
Gas-turbine power plants have evolved continuously since the first land-based installation by Brown Boveri Corporation at Neuchatel, Switzerland, in 1939, and the first aircraft engine turbines developed in Great Britain by Whittle and, in Germany, by von Ohain. Continuing applications of gas turbines for power generation did not occur until the 1950s, and large-scale deployment of this type of power plant was not popularized until the 1960s. Today there are over 115,000 MW of gas-turbine-type plants in U.S. commercial service, representing more than 2700 separate units. Unit sizes range from a few hundred kilowatts for special power-generation applications to the more commonly considered 20- to 270-MW units operated by electric utilities. Unit sizes continue to grow as higher temperatures, greater airflow, and innovative cycle technologies are incorporated into new power generators. The power-generation application uses two types of design: aeroderivative units modified from aircraft engines, and those especially designed for power-generation service. This distinction exists because gas turbines are available in numerous sizes that have been modified from existing aircraft engine types so that they will operate satisfactorily at constant speed for power generation. Contrasted to this type are gas turbines that have been mechanically designed for power generation to resemble steam turbines as “heavy-duty” designs, used mostly to generate electrical power, but sometimes to operate as mechanical drives, in the latter case frequently at variable speeds. The main applications prompting gas-turbine use are, first of all, aircraft engines and, a distant second, the power-generation application. Other uses for the gas turbine, such as marine propulsion and compressor or other mechanical load drive, use modifications of engines designed for the prime applications mentioned. Generally advances in technology to the state of the art are made in aircraft engines, then later transferred to heavy-duty designs.
During the early development phases of the 1940s and 1950s, gas turbines were largely inefficient compared to other prime movers, but in the case of aircraft had an advantageous output per unit weight and better high speed propulsive efficiency, while in the case of power generation had better unit cost and physical size per unit output. Technology was driven for many years to increase unit sizes and reduce unit costs. During the 1970s, gas turbines operating in combined cycles with steam turbines achieved superior efficiencies to those of other available power generation cycles and thus have broadened their application phases. The types of components employed in gas turbines fall into the general categories of compressors, turbines, and combustors, with particular emphasis on the packaging for power generation application and the materials in the hot gas path compatible with utility service.