Steam engine definition
An external combustion engine where water is converted to steam in a boiler outside the cylinder . The steam is then admitted to the cylinder where it expands against a piston . As the steam expands it cools and begins to condense . This mixture of water droplets and steam is forced out of the cylinder on the return stroke and into the condenser where the remaining steam is condensed into water. This water is forced into the boiler by a pump and the cycle is repeated. Steam engines have some notable drawbacks: slow warm up, freezing of the water system in cold weather, and contamination of the water by scale , oil, and sludge which can wreak havoc with the boiler, pumps, and condenser . But they also offer certain advantages: the potential for high fuel economy with low emissions, the ability to start from rest against a load so a clutch is not needed, and the torque developed is greatest at low rpm so in some applications a multiple-ratio gearbox is not necessary.