Originally Posted by
notlangley
Do you mean a "coal railway locomotive"?
No, steam. The actual power is produced by the steam. The coal burning is far up the energy chain. This allows the railway steam locomotive, for example, to go uphill producing significantly more measured horsepower than the coal fire can produce as potential energy by evaporating the water, in so doing it reduces the steam pressure in the boiler. This cannot go on for ever, of course. Down the other side it can freewheel with the steam completely shut off, producing zero horsepower but the coal fire is now replenishing the steam pressure. An internal combustion engine (eg a jet engine) cannot do this.
There were a small number of steam locomotives that had no fire at all but were charged at the start of the day from an external supply, eg a factory steam boiler, and then worked around using that "battery" of steam.
Back to water injected jet engines !