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Hub AI
Compound locomotive AI simulator
(@Compound locomotive_simulator)
Hub AI
Compound locomotive AI simulator
(@Compound locomotive_simulator)
Compound locomotive
A compound locomotive is a steam locomotive which is powered by a compound engine, a type of steam engine where steam is expanded in two or more stages. The locomotive was only one application of compounding. Two and three stages were used in ships, for example.
Compounding became popular for railway locomotives from the early 1880s and by the 1890s were becoming common. Large numbers were constructed, mostly two- and four-cylinder compounds, in Germany, Austria, Hungary, and the United States. It declined in popularity due to a perceived increased maintenance requirement. Nonetheless, compound Mallets were built by the Norfolk and Western Railway up to 1952 and continued to be designed and built in France until the end of steam in the 1970's. French compound engines became highly developed, eventually incorporating reheaters between the high and low pressure stages as well as the initial use of superheaters, ultimately achieving the highest power-to-weight ratio and highest horsepower to fire grate-area ratio of any steam locomotives ever built.
In the usual arrangement for a compound engine the steam is first expanded in one or two high-pressure (HP) cylinders, then having given up some heat and lost some pressure, it exhausts into a larger-volume low-pressure (LP) cylinder, (or two, - or more), thus extending the expansion part of the thermodynamic cycle. The cylinders can be said to work in "series" as opposed to the normal arrangement of a simple-expansion locomotive where they work in "parallel". In order to balance piston thrusts of a compound, the HP:LP cylinder volume ratio has to be carefully determined, usually by increasing the LP cylinder diameter and/or by lengthening the stroke. In non-condensing engines, the HP:LP volume ratio is usually 1:2.25. On geared locomotives, cylinder volumes can be kept more or less identical by increasing LP piston speed. Compound may refer to any multiple-expansion engine. Added insight comes with the terms double, triple, quadruple. At least three triple-expansion locomotives were built; A vertical boiler, high- pressure 0-4-0 made by Greenwood & Batley in 1878, a 2-2-2 converted from a double expansion locomotive by Francis Webb of the London and North Western Railway and an experimental 4-8-0, named the L.F.Loree, which was built by the American Locomotive Company and the Delaware & Hudson Railroad in 1933.
The main benefits sought from compounding are reduced fuel and water consumption plus higher power/weight ratio due to more expansion in the cylinder before the exhaust valve opens, which gives a higher efficiency; additional advantages include smoother torque and in many cases, superior riding qualities with consequent less wear on the track and running gear. Where heavy grades and low axle loads were combined, the compound locomotive was often deemed to be the most viable solution.
Even more than other locomotives, designing a compound locomotive demands a firm grasp of thermo- and fluid dynamics. A lack of these led to many less-than-optimal designs, especially in the early years of the 20th century. Compound designs' long steam cycle made them particularly sensitive to temperature-drop and condensation of the steam during its lengthy passage. In rebuilding older locomotives from 1929 onwards, André Chapelon was able to inexpensively obtain what seemed almost "magical" improvements in power and economy by improving flow through the steam circuit, at the same time putting in a larger superheater to increase the initial steam temperature and delay condensation in the LP cylinders.
To prevent severe condensation taking place, the L.N.E.R. applied resuperheat to their water-tube boilered No. 10,000 to make up for inadequate HP superheat. The Paris-Orleans Railway designed a demonstrator 2-12-0 locomotive, No. 160-A1 (tested 1948-51), with resuperheat between HP and LP stages. They also fitted steam jackets to both HP/LP cylinders for what was believed by Chapelon to be the first time for a compound locomotive. Resuperheating was also by Porta on his prototype 4-8-0 rebuild: 'La Argentina' (tested around the same time in Argentina).
Proponents of simple expansion argue that use of early cut-off in the cylinder thus expanding small quantities of steam at each piston stroke obviates the need for the complication and initial expense of compounding and indeed multi-cylinder single expansion – this is an ongoing debate.
There are many configurations, but two basic types can be defined, according to how HP and LP piston strokes are phased and hence whether the HP exhaust is able to pass directly from HP to LP (Woolf compounds) or whether pressure fluctuations necessitate an intermediate "buffer" space in the form of a steam chest or pipe known as a receiver (receiver compounds).
Compound locomotive
A compound locomotive is a steam locomotive which is powered by a compound engine, a type of steam engine where steam is expanded in two or more stages. The locomotive was only one application of compounding. Two and three stages were used in ships, for example.
Compounding became popular for railway locomotives from the early 1880s and by the 1890s were becoming common. Large numbers were constructed, mostly two- and four-cylinder compounds, in Germany, Austria, Hungary, and the United States. It declined in popularity due to a perceived increased maintenance requirement. Nonetheless, compound Mallets were built by the Norfolk and Western Railway up to 1952 and continued to be designed and built in France until the end of steam in the 1970's. French compound engines became highly developed, eventually incorporating reheaters between the high and low pressure stages as well as the initial use of superheaters, ultimately achieving the highest power-to-weight ratio and highest horsepower to fire grate-area ratio of any steam locomotives ever built.
In the usual arrangement for a compound engine the steam is first expanded in one or two high-pressure (HP) cylinders, then having given up some heat and lost some pressure, it exhausts into a larger-volume low-pressure (LP) cylinder, (or two, - or more), thus extending the expansion part of the thermodynamic cycle. The cylinders can be said to work in "series" as opposed to the normal arrangement of a simple-expansion locomotive where they work in "parallel". In order to balance piston thrusts of a compound, the HP:LP cylinder volume ratio has to be carefully determined, usually by increasing the LP cylinder diameter and/or by lengthening the stroke. In non-condensing engines, the HP:LP volume ratio is usually 1:2.25. On geared locomotives, cylinder volumes can be kept more or less identical by increasing LP piston speed. Compound may refer to any multiple-expansion engine. Added insight comes with the terms double, triple, quadruple. At least three triple-expansion locomotives were built; A vertical boiler, high- pressure 0-4-0 made by Greenwood & Batley in 1878, a 2-2-2 converted from a double expansion locomotive by Francis Webb of the London and North Western Railway and an experimental 4-8-0, named the L.F.Loree, which was built by the American Locomotive Company and the Delaware & Hudson Railroad in 1933.
The main benefits sought from compounding are reduced fuel and water consumption plus higher power/weight ratio due to more expansion in the cylinder before the exhaust valve opens, which gives a higher efficiency; additional advantages include smoother torque and in many cases, superior riding qualities with consequent less wear on the track and running gear. Where heavy grades and low axle loads were combined, the compound locomotive was often deemed to be the most viable solution.
Even more than other locomotives, designing a compound locomotive demands a firm grasp of thermo- and fluid dynamics. A lack of these led to many less-than-optimal designs, especially in the early years of the 20th century. Compound designs' long steam cycle made them particularly sensitive to temperature-drop and condensation of the steam during its lengthy passage. In rebuilding older locomotives from 1929 onwards, André Chapelon was able to inexpensively obtain what seemed almost "magical" improvements in power and economy by improving flow through the steam circuit, at the same time putting in a larger superheater to increase the initial steam temperature and delay condensation in the LP cylinders.
To prevent severe condensation taking place, the L.N.E.R. applied resuperheat to their water-tube boilered No. 10,000 to make up for inadequate HP superheat. The Paris-Orleans Railway designed a demonstrator 2-12-0 locomotive, No. 160-A1 (tested 1948-51), with resuperheat between HP and LP stages. They also fitted steam jackets to both HP/LP cylinders for what was believed by Chapelon to be the first time for a compound locomotive. Resuperheating was also by Porta on his prototype 4-8-0 rebuild: 'La Argentina' (tested around the same time in Argentina).
Proponents of simple expansion argue that use of early cut-off in the cylinder thus expanding small quantities of steam at each piston stroke obviates the need for the complication and initial expense of compounding and indeed multi-cylinder single expansion – this is an ongoing debate.
There are many configurations, but two basic types can be defined, according to how HP and LP piston strokes are phased and hence whether the HP exhaust is able to pass directly from HP to LP (Woolf compounds) or whether pressure fluctuations necessitate an intermediate "buffer" space in the form of a steam chest or pipe known as a receiver (receiver compounds).