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The American Workhorse

February 27, 2015

Born in the skies over Germany during World War II, it has become the machine that powers America.

Tinkerers in workshops before WWII had dreamed of using energy more efficiently than in the internal combustion engine.

Why use energy from a burning fuel to drive a piston a few short inches, when the burning fuel could be allowed to expand further so that more work could be extracted from the available energy.

Germany was the first to move the workshop model into a viable machine, that had the potential to alter the air war in Europe.

To more effectively use the energy from the expanding gases, the gasses were directed to flow through a series, or stages, of increasingly larger areas formed by buckets mounted on a shaft, where the expanding gasses forced the buckets to move, creating rotational motion of the buckets and shaft.

But this was not enough if the maximum amount of energy was to be extracted from the burning fuel. More oxygen was needed, which could be supplied by compressing the air before it entered the combustion chamber.

A compressor consisting of stages of rotating blades that became smaller with each stage as the volume of air was compressed, was built into the machine, and added in such a way that the rotating combustion section drove the compressor.

This basic gas turbine was the jet engine, where the thrust from the engine propelled the plane to which the jet engine was attached.

Jet engines powering airplanes had to be as light as possible.

Land-based versions could be bulkier, and built to deliver more power.

Gas Turbine Courtesy of General Electric

Gas Turbine Courtesy of General Electric

The first GE land-based versions in 1950 were built to generate electricity, by connecting the gas turbine to a generator, the same type of generator that steam turbines had been powering for half a century. See Growing Role of Gas Turbines in Power Generation.

In the 1960s, the exhaust from the gas turbine was used to generate steam for use in a steam turbine, resulting in the combined cycles power plant that increased efficiency to over 60%.

There were many more applications for which the gas turbine was preeminently suited.

The shaft from the gas turbine could be connected to many other mechanical devices such as pumps and compressors.

For example, gas turbines drive compressors on natural gas pipelines. Gas turbines drive pumps for injecting water into oil wells to enhance the recovery of oil. And, they drive the rotor blades on helicopters.

They can also use a variety of fuels, including oil, kerosine, syngas and natural gas.

Their varying configurations can be adapted for applications having special requirements.

For example, the aircraft jet engine, with its lighter weight, has been adapted to provide propulsion for ships, such as destroyers and frigates.

The aero derivative version has also been adopted to provide backup power generation because it can be brought to speed quickly to replace the lost power from wind and solar when the wind stops blowing and the sun stops shining.

Gas turbines are akin to the precision and delicacy of renowned swiss watches.

The tolerances are miniscule. Materials must be able to withstand very high temperatures. Machining must be delicate and precise. Minute air pathways are formed within buckets and blades so they can be cooled with air. Ceramics replace steel for extremely hot conditions, or are sprayed onto buckets to provide protection from heat and erosion. Wheels holding the buckets are shrunk fit onto the shaft. The rotor must be precisely balanced so as to prevent vibration. Forgings must be free of the slightest defect, or centrifugal forces can cause them to explode.

Gasoline and diesel engines still provide power for specific applications, but the gas turbine powers America on the land, on the ocean and in the air.

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2 Comments leave one →
  1. sandek1 permalink
    February 27, 2015 9:11 am

    Interesting article.

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