The steam engine is a reciprocating power machine, which converts the energy of steam into mechanical work. The appearance of the steam engine caused the industrial revolution in the18th century. Until the beginning of the 20th century, it was still the most important prime mover in the world, and then it gradually gave way to internal combustion engines and steam turbines.
From the end of 16 to the end of 17, the British mining industry, especially coal mines, has developed to a considerable scale, and it is difficult to meet the requirements of pumping groundwater only by manpower and animal power, and there are abundant and cheap coal as fuel on site. The needs of reality have prompted many people in Britain, such as Papan, savery and newcomen, to devote themselves to the exploration and experiment of "lifting water by firepower".
The world's first practical steam pump made in savery won the British patent named "Friends of Miners" on 1698. He first filled an egg-shaped container with steam, then closed the steam inlet valve and sprayed cold water outside the container to condense the steam in the container to form a vacuum. Open the water inlet valve, and the water at the bottom of the mine is sucked into the container through the water inlet pipe under the action of atmospheric pressure; Close the water inlet valve, reopen the steam inlet valve, and use steam pressure to press the water in the container out through the drain valve. When the water in the container is drained and filled with steam, close the steam inlet valve and drain valve, and spray water again to condense the steam. In this way, the two egg-shaped containers work alternately and can continuously drain water.
The pumps in savery rely on vacuum suction to pump water, and the pumping depth cannot exceed six meters. In order to pump water from a mine tens of meters deep, it is necessary to install a water pump in the depth of the mine and use high steam pressure to pump water to the ground, which is undoubtedly difficult and dangerous at that time.
Newcomen and his assistant Cali invented the atmospheric steam engine in 1705 to drive the independent water pump, which is called the newcomen atmospheric steam engine. This kind of steam engine was first popularized in Britain, then in continental Europe, and its modified products were still being manufactured until the beginning of19th century. The thermal efficiency of newcomen atmospheric steam engine is very low, which is mainly due to the fact that after steam enters the cylinder, it condenses on the cylinder wall that has just been cooled by water and loses a lot of heat. It is only promoted in coal-producing areas with low coal prices.
1764, British instrument repairman Watt noticed this shortcoming when repairing the newcomen steam engine model for Glasgow University, and invented the steam engine with the condenser separated from the cylinder wall in 1765, and obtained the British patent in 1769. In the early days, Watt's steam engine still used the balance bar and pull rod mechanism to drive the water pump. In order to remove the condensate and air from the condenser, Watt installed an air pump. He also installed an interlayer on the outer wall of the cylinder and heated the cylinder wall with steam to reduce condensation loss.
1782 or so, Watt further improved the machine and completed two important inventions: in the middle of the active cold working stroke, the steam inlet valve was closed to make the steam expand to do work and improve the thermal efficiency; Make the steam do work on both sides of the piston (double-acting) to improve the output power. At this time, the piston has to pull down the lever and push up the lever, and the fan-shaped balance bar and zipper are no longer applicable, so Watt invented the parallelogram mechanism. Watt also applied crank-connecting rod mechanism to steam engine at the end of 18.
Watt's creative work made the steam engine develop rapidly. He turned the machine that can only carry water into a widely used steam engine, which doubled the thermal efficiency and greatly reduced the coal consumption. So Watt was the main inventor of the steam engine.
/kloc-Since the late 8th century, steam engines have been widely used not only in mining, but also in smelting, textile, machinery manufacturing and other industries. It has increased the textile output in Britain by five times (from 1766 to 1789) in more than 20 years, provided a large number of consumer goods for the market, accelerated the accumulation of funds and put forward urgent requirements for the transportation industry.
The experiment of using steam engine as propulsion power on ships began in 1776. After continuous improvement, Fulton, USA made the first practical open-wheel propulsion steam engine ship "clermont". Since then, steam engines have been used as propulsion power on ships for more than one hundred years.
180 1 year, Trevithick of England put forward the concept of movable steam engine. 1803, this kind of movable steam engine using railway tracks first appeared in coal mining area, which is the prototype of locomotive. Stephenson of Britain improved the locomotive continuously, and created the "rocket" steam locomotive in 1829. The locomotive is towing a carriage with 30 passengers at a speed of 46 km/h, which has attracted the attention of all countries and created the railway era.
At the end of 19, with the rise of electric power application, steam engines were once used as the main power machinery of power stations. /kloc-in 0/900, there was a steam engine power station with a single unit power of 5 MW in new york, USA.
The development of steam engines reached its peak in the early 20th century. It has the advantages of constant torque, variable speed, reversibility, reliable operation and convenient manufacture and maintenance, and is widely used in various fields such as power stations, factories, locomotives and ships, especially on ships.