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TECHNOLOGUE

The Adaptable Gas Turbine

Whether creating electricity or moving planes, this engine continues to inspire innovation

Lee S. Langston

2013-07TechLangstonFB.jpgClick to Enlarge ImageTurbines have been around for a long time—windmills and water wheels are early examples. The name comes from the Latin turbo, meaning vortex, and thus the defining property of a turbine is that a fluid or gas turns the blades of a rotor, which is attached to a shaft that can perform useful work. Hydrocarbon-fueled turbines, however, are one of the youngest energy conversion devices: Their first use in either generating electricity or powering jet aircraft flight took place in 1939. Through the efforts of many thousands of engineers in the intervening 70 years or so, such gas turbines have come to dominate aircraft propulsion and, with their now-unmatched thermal efficiency and low cost, are the superstars of electric power plants. With energy a central concern in modern society, gas turbine technology continues to be innovative.

Power Conversion

Much of my efforts as a mechanical engineer, both in industry and academia, have been guided by the first law of thermodynamics (stated in the principle of the conservation of energy): Energy is neither created nor destroyed, but can be changed in form. The “changed in form” part of the law is what many mechanical engineers do, as they research and develop energy conversion devices. An example of this conversion is transforming heat (say, from the combustion of a hydrocarbon fuel) into motive power (such as a jet powered airplane) or electricity. Devices that perform this transformation are called prime movers.

The major modern-day prime movers convert heat supplied by nuclear or chemical reactions into useful forms of energy. The gas turbine, co-invented by Hans von Ohain, Frank Whittle and the engineers at the Swiss firm Brown, Boveri & Cie, succeeded the steam engine, realized in 1769 by Thomas Newcomen and James Watt; the spark ignition engine of Nikolaus Otto from 1876; the compression ignition engine of Rudolf Diesel from 1884 and the steam turbine of Charles Parsons from 1897.

The name gas turbine is somewhat misleading, for it implies a simple turbine that uses gas as a working fluid. Actually, a gas turbine has a compressor to draw in and compress gas (usually air), a combustor (or burner) to add combustive fuel (usually a hydrocarbon liquid or gas) to heat the compressed gas, and a turbine (or expander) to extract power from the hot gas flow with its rotation of the turbine blades.

Because the origin of the gas turbine lies in both the electric power field and aviation, there has been a profusion of other names for the gas turbine. For land and marine applications the gas turbine moniker is most common, but it is also called a combustion turbine, a turboshaft engine and sometimes a gas turbine engine. For aviation applications it is usually called a jet engine, and various other names (depending on the particular aviation configuration or application) such as jet turbine engine, turbojet, turbofan, fanjet and turboprop or prop jet (if it is used to drive a propeller). The compressor-combustor-turbine part of the gas turbine is commonly called the gas generator.




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