Steam locomotive performance
A factor that limits steam locomotive performance is the rate at which fuel is fed into the fire. In the early 20th century some locomotives became so large, that the fireman could not shovel coal fast enough.
In the United States, various steam-powered mechanical stokers became standard equipment and were adopted and used elsewhere including Australia and South Africa.
Introducing cold water into a boiler reduces power, and from the 1920s a variety of heaters was incorporated. The most common type for locomotives was the exhaust steam feed-water heater that piped some of the exhaust through small tanks mounted on top of the boiler or smoke-box or elsewhere into the tender tank; the warm water then had to be delivered to the boiler by a small auxiliary steam pump.
Steam engines use of live steam and exhaust steam injectors also assists in the pre-heating of boiler feed water to a small degree, though there is no efficiency advantage to live steam injectors.
The locomotives consume vast quantities of water because they operate on an open cycle, expelling their steam immediately after a single use rather than recycling it in a closed loop as stationary and marine steam engines do.
Water was a constant logistical problem, and in some desert areas condensing engines were devised. These engines had huge radiators in their tenders and instead of exhausting steam out of the funnel it was captured and passed back to the tender and condensed.
The cylinder lubricating oil was removed from the exhausted steam to avoid a phenomenon known as priming, a condition caused by foaming in the boiler which would allow water to be carried into the cylinders causing damage because of its incompressibility.
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