Gas turbine locomotive

A Gas turbine locomotive is a locomotive powered by a gas turbine. The majority of gas turbine locomotives have had electric transmission but mechanical transmission has also been used, particularly in the early days. The advantage of using gas turbines is that they have very high power-to-bulk and power-to-weight ratios. The disadvantage is that gas turbines generally have lower thermal efficiency than diesel engines, especially when running at less than full load.

Where electric transmission is used, the engine is usually a single-shaft machine in which one turbine drives both the compressor and the output shaft.

With mechanical transmission, the power turbine must be capable of starting from rest, so a more complex arrangement is necessary. One option is a two-shaft machine, with separate turbines to drive the compressor and the output shaft. Another is to use a separate gas generator, which may be of either rotary or piston type.

Examples of gas turbine-mechanical locomotives:

See Gas turbine for the early history of gas turbine development.

A gas turbine locomotive was patented in 1861 by Marc Antoine Francois Mennons (British patent no. 1633).

The drawings in Mennons' patent show a locomotive of 0-4-2 wheel arrangement with a cylindrical casing resembling a boiler. At the front of the casing is the compressor, which Mennons calls a ventilator. This supplies air to a firebox and the hot gases from the firebox drive a turbine at the back of the casing. The exhaust from the turbine then travels forwards through ducts to preheat the incoming air. The turbine drives the compressor through gearing and an external shaft. There is additional gearing to a jackshaft which drives the wheels through side rods. The fuel is solid (presumably coal, coke or wood) and there is a fuel bunker at the rear.

There is no evidence that the locomotive was actually built but the design includes the essential features of gas turbine locomotives built in the 20th century, including compressor, combustion chamber, turbine and air pre-heater.

Work leading to the emergence of the gas turbine locomotive began in France and Sweden in the 1920s but the first locomotive did not appear until 1933. These early experiments used piston engines as gas generators. This idea has not been widely adopted, but it might be worth re-visiting. High fuel consumption was a major factor in the decline of conventional gas-turbine locomotives and the use of a piston engine as a gas generator would probably give better fuel economy than a turbine-type compressor, especially when running at less than full load.

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