The question “Steam engines – what’s that?” was a question already raised in the classic black and white German film “Feuerzangenbowle” (“The Punch Bowl”), which was set in the late 19th century. In the second half of the 18th century, a new era was set in motion, the dawn of industrialisation. The Scottish inventor, James Watt (1736-1819), improved past inventions and registered his design as a patent in 1769. He continuously perfected his steam engine model and is considered to be the man who discovered the potential of harnessing steam expansion. If energy can be obtained from “water and fire”, energy which can run boats.
At the start of the 19th century, whole factories were kitted out with a central steam engine. This powered individual machines via transmissions.
The water in the boiler is heated by fire, this generates steam and because it is trapped in the boiler pressure builds up. Steam can pass, however, to the cylinder (blue dotted lines) via the slide valves.
In the second diagram the steam passes to the left side of the cylinder, pushing the piston to the right. At the same time the exhaust steam from previous stroke is directed, by the other port on the slide valve, out into the atmosphere, having done its work (green dotted line).
Just before the piston reaches the end of its move, on the extreme right, the slide valve cuts off the steam from the boiler. This is the point where the crank is at the limit of its movement and is known as „top-dead-centre„ or „bottom-dead-centre„, referring to the two possible geometric positions. The flywheel carries the crank over this critical position by the energy it has stored from previous power strokes.
The slide valve continues to move in the same direction this time opening the inlet port to admit steam to the right hand side of the piston, again pushing the piston but now to the left, exhausting the steam through the left hand port. The whole cycle restarts when the „dead centre„ is reached once more.