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| A '''steam engine''' is a ] that makes use of the ] that exists as pressure in ], converting it to mechanical ]. Steam engines were used in ]s, ] trains and ], and were essential to the ]. They are still used for electrical power generation. | A '''steam engine''' is a ] that makes use of the ] that exists as pressure in ], converting it to mechanical ]. Steam engines were used in ]s, ] trains and ], and were essential to the ]. They are still used for electrical power generation. | ||
| A steam engine needs a boiler to boil ] to produce steam under pressure. Any ] source can be used, but the most common is a ] or ] ]. The steam is allowed to expand by pushing against a piston or turbine, whose motion is used to do work. | A steam engine needs a boiler to boil ] to produce steam under pressure. Any ] source can be used, but the most common is a ] or ] ]. The steam is allowed to expand by pushing against a piston or turbine, whose motion is used to do work. | ||
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| The first steam device, the ''aeolipile'', was invented by ], a ], in the ] AD, but used only as a toy. ], a French physicist, built a working model of a steam engine after observing steam escaping from his ] in about ]. Early industrial steam engines were designed by ] (]), ] (]), and ] (]), each of whom added new refinements. | The first steam device, the ''aeolipile'', was invented by ], a ], in the ] AD, but used only as a toy. ], a French physicist, built a working model of a steam engine after observing steam escaping from his ] in about ]. Early industrial steam engines were designed by ] (]), ] (]), and ] (]), each of whom added new refinements. | ||
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| Steam engines are of various types but most are ] or ] devices. | Steam engines are of various types but most are ] or ] devices. | ||
| ] demonstrated the first functional self-propelled steam vehicle, his "steam wagon", in ]. Arguably, this was the first ]. Steam engine powered automobiles continued to compete with other motive systems into the early decades of the ]. However | |||
| ⚫ | On ], ] at the ] in ], the first self-propelling steam engine or steam locomotive built by ] was first demonstrated. | ||
| ⚫ | steam engines are less favored for automobiles, which are generally powered by ]s, because steam requires at least thirty seconds (in a flash boiler) or so to develop pressure. | ||
| ⚫ | On ], ] at the ] in ], the first self-propelling ] steam engine or steam locomotive built by ] was first demonstrated. | ||
| The strength of the steam engine for modern purposes is in its ability to convert raw heat into mechanical work. Unlike the internal combustion engine, the steam engine is not particular about the source of heat. | The strength of the steam engine for modern purposes is in its ability to convert raw heat into mechanical work. Unlike the internal combustion engine, the steam engine is not particular about the source of heat. | ||
Revision as of 17:37, 5 December 2003
A steam engine is a heat engine that makes use of the potential energy that exists as pressure in steam, converting it to mechanical work. Steam engines were used in pumps, locomotive trains and steam ships, and were essential to the Industrial Revolution. They are still used for electrical power generation.
A steam engine needs a boiler to boil water to produce steam under pressure. Any heat source can be used, but the most common is a wood or coal fire. The steam is allowed to expand by pushing against a piston or turbine, whose motion is used to do work.
The first steam device, the aeolipile, was invented by Heron of Alexandria, a Greek, in the 1st century AD, but used only as a toy. Denis Papin, a French physicist, built a working model of a steam engine after observing steam escaping from his pressure cooker in about 1679. Early industrial steam engines were designed by Thomas Savery (1698), Thomas Newcomen (1712), and James Watt (1769), each of whom added new refinements.
Early engines worked by the vacuum of condensing steam, whereas later types (such as steam locomotives, used the power of expanding steam.
Steam engines are of various types but most are reciprocal piston or turbine devices.
Nicolas-Joseph Cugnot demonstrated the first functional self-propelled steam vehicle, his "steam wagon", in 1769. Arguably, this was the first automobile. Steam engine powered automobiles continued to compete with other motive systems into the early decades of the 20th century. However steam engines are less favored for automobiles, which are generally powered by internal combustion engines, because steam requires at least thirty seconds (in a flash boiler) or so to develop pressure.
On February 21, 1804 at the Pen-y-Darren ironworks in Wales, the first self-propelling railway steam engine or steam locomotive built by Richard Trevithick was first demonstrated.
The strength of the steam engine for modern purposes is in its ability to convert raw heat into mechanical work. Unlike the internal combustion engine, the steam engine is not particular about the source of heat.
A steam engine exhausting to atmosphere will have an efficiency (including the boiler) of 5% but with the addition of a condenser the efficiency is greatly improved to 25% or better. A power station with exhaust reheat, etc. will achieve 30% efficiency.
One source of inefficiency is that the condenser causes losses by being somewhat hotter than the outside world. Thus any closed-cycle engine will always be somewhat less efficient than any open-cycle engine, because of condenser losses.
Most notably, without the use of a steam engine nuclear energy could not be harnessed for useful work, as a nuclear reactor does not directly generate either mechanical work or electrical energy - the reactor itself simply heats water. It is the steam engine which converts the heat energy into useful work.
Also see
- Newcomen steam engine
- Watt steam engine
- Steam Locomotive for details of steam powered railway 'engines'