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.
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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.
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.
The locomotives were built by Renault and had Pescara free-piston engines as gas generators. Each gas generator consisted of a horizontal, single cylinder, two-stroke diesel engine with opposed pistons. It had no crankshaft and the pistons were returned after each power stroke by compression and expansion of air in a separate cylinder. The exhaust from the diesel engine powered the gas-turbine which drove the wheels through a two-speed gearbox and propeller shafts.
Turbine power was considered for railway traction in the former Czechoslovakia. Two turbine-powered prototypes were built, designated TL 659.001 and .002, featuring C-C wheel arrangement, 3200 hp (2.4 MW) main turbine, helper turbine and Tatra 111 helper diesel engine. The first prototype was finished in February 1958 and was scheduled to be exhibited at Expo '58. This was aborted, because it wasn't ready in time. The first out-of-factory tests were conducted in March 1959 on the Plzeň–Cheb–Sokolov line. On May 15, 1959, the first prototype pulled its heaviest train, 6486 metric tons, but the turbine caught fire only a day later. The engine was never restored and eventually scrapped. The second prototype was built with lessons learned from the first prototype. It left the factory in March 1960 and was the only turbine locomotive to pass the tests for regular service on tracks of the former ČSD. This engine was tried near Kolín and Plzeň with mixed results. This engine was taken out of service in April 1966 and sold to University of Žilina as an educational instrument. The locomotive was scrapped some time later.
Although these experiments had mixed results, they were the most powerful locomotives with purely mechanical powertrain in the world and also the most powerful independent-traction locomotives in Czechoslovakia.
The Power gas locomotive was built by Gotaverken. It had a vertical, five cylinder, two-stroke diesel engine with opposed pistons. There was a single crankshaft connected to both upper and lower pistons. The exhaust from the diesel engine powered the gas turbine which drove the wheels through reduction gearing, jack shaft and side rods.
The free-piston engine was patented in 1934 by Raul Pateras Pescara (1890–1966). He was an Argentinian, who worked in Spain and France, and was prominent in helicopter development in the 1919s.
In the 1940s and 1950s research was done, in both the USA and UK, aimed at building gas turbine locomotives which could run on pulverized coal. The main problem was to avoid erosion of the turbine blades by particles of ash. Some bench testing was done but the projects were abandoned before any complete locomotives were built. The sources for the following information are Robertson [1] and Sampson.[2]
In the USA, the plan was to use a gas turbine similar to an oil-fuelled one and to remove ash particles with filters. Details of the US research (done in 1946) were passed to Britain's London, Midland and Scottish Railway.
On 23 December 1952 the UK Ministry of Fuel and Power placed an order for a coal-fired gas turbine locomotive to be used on British Railways. The locomotive was to be built by the North British Locomotive Company and the turbine would be supplied by C. A. Parsons and Company.
According to Sampson, the plan was to use indirect heating. The pulverized coal would be burned in a combustion chamber and the hot gases passed to a heat exchanger. Here, the heat would be transferred to a separate body of compressed air which would power the turbine. Essentially, it would have been a hot air engine using a turbine instead of a piston.
Robertson shows a diagram which confirms Sampson's information but also refers to problems with erosion of turbine blades by ash. This is strange because, with a conventional shell and tube heat exchanger, there would be no risk of ash entering the turbine circuit.
Working cycle
There were two separate, but linked, circuits - the combustion circuit and the turbine circuit.
Specification
The locomotive was never built but the specification was as follows:
The projected output was:
The transmission was to be mechanical, via a two-speed gearbox, giving a high speed for passenger working and a lower speed for freight. The tractive effort figures, quoted above, look suspiciously high for the specified speeds. It seems more likely that the figures quoted are for starting tractive effort and maximum speed in high gear and low gear respectively.
There is a model of the proposed locomotive at Glasgow Museum of Transport and some records are held at the National Railway Museum.
The British Rail GT3 was a much simpler machine consisting essentially of a standard oil-fired gas turbine mounted on a standard steam locomotive chassis, built as a demonstrator by English Electric in 1961. Its almost crude simplicity enabled it to avoid much of the unreliability which had plagued the complex experimental GTELs 18000 and 18100 in earlier years, but it nevertheless failed to be competitive against conventional traction and was scrapped.
Talk at the London Science Museum 12th April 1995 by J.R.Bolter Copyright the Newcomen Society