Application of steam engine principle

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.

A steam engine needs a boiler to boil water to produce high-pressure steam. This kind of boiler can use wood, coal, oil or natural gas or even combustible garbage as heat source. The expansion of steam pushes the piston to do work.

The first steam engine in the world was invented by Greek mathematician Herod of Alexandria in the 1 th century, which was the embryonic form of the steam engine. [2]

About 1679, the French physicist Dennis Papan made the working model of the first steam engine after observing the steam escaping from his pressure cooker. Contemporary Samuel Moran also put forward the idea of steam engine. [2]

Thomas Seville made an early industrial steam engine in 1698, and Thomas Newcomen made an early industrial steam engine in 17 12. They all made their own contributions to the development of steam engines.

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 need of reality urges many people, such as Savili and newcomen in Britain, to devote themselves to the exploration and experiment of "lifting water by fire".

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. Newcomen's steam engine introduced steam into the cylinder, then closed the valve and injected cold water into the cylinder, which caused a vacuum when the steam condensed. Air pressure on the other side of the piston pushes the piston. Insert a pole deep into the mine to drive the water pump. The motion of the piston of the steam engine is transmitted to the piston of the pump through this rod, and the water is pumped out of the well. 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.

Watt gradually discovered the defects of this steam engine by using scientific theory. 1765 invented the steam engine with the condenser separated from the cylinder wall, and 1769 obtained the British patent. From 1765 to 1790, he made a series of inventions, such as separate condenser, cylinder external insulation layer, piston lubricated with oil, planetary gear, parallel linkage mechanism, centrifugal governor, throttle valve, pressure gauge and so on. , make the efficiency of the steam engine to more than three times that of the original newcomen machine, and finally invented the industrial steam engine.

The first big improvement is to separate the cylinder from the condensing cylinder through the valve. Watt invented this improvement in Birmingham. This improvement has improved the efficiency of the steam engine. The next improvement is the automatic operation of the valve. 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.

These early vacuum steam engines had limited efficiency, but were relatively safe, because their pressure was relatively low, and the machines contracted inward instead of exploding outward to prevent material damage. Their efficiency is limited by external air pressure, cylinder deformation, combustion and boiling efficiency and condensation capacity. The theoretical maximum efficiency is limited by the relatively low boiling temperature of water at ordinary atmospheric pressure. The use of high temperature and high pressure steam greatly improves the efficiency of steam engines. But this kind of steam engine is much more dangerous than vacuum steam engine. The explosion of boilers and machines caused many serious accidents. The safety valve has brought great improvement here. When the pressure is too high, the safety valve deflates and depressurizes. But the real guarantee of safety only depends on the experience and safety rules of construction, operation and maintenance.

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. Therefore, Watt is a reformer of 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.

/kloc-in 0/800, Trevithick of England designed a high-pressure steam engine, which can be installed on a larger car body. 1803, he used it to propel motorcycles running on circular tracks, find people who like novelty and charge them. This is the prototype of the locomotive. Stephen Sun of Britain constantly improved the locomotive 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, so it was widely used in power stations, factories, locomotives, ships and other fields, especially in warships, and became the only prime Mover at that time.

In terms of land transportation, people began to develop a means of transportation that uses steam engines to drive vehicles to move quickly. The world's first steam engine train was exhibited by Richard Travisk of Wales on February 26th, 1984. George stephenson (178 1- 1848) took the lead in achieving breakthrough results.

Stephenson, the son of a coal miner, was familiar with the steam engine used to pump water in the mine since he was a child, and later decided to engage in the invention and creation of transportation tools.

18 14, the first steam locomotive "Brazer" developed by him (named after Prussian general Brazer, who helped Britain fight against Napoleon's army) was successfully put into trial operation.

1On September 27th, 825, Stephen Sun personally drove the Voyager steam locomotive designed and manufactured by him in cooperation with others on the newly laid railway, and achieved success. The application of the steam engine in the transportation industry has enabled mankind to enter the "train age" and rapidly expanded the scope of human activities.

Stephenson successfully commissioned Brazer locomotive in 18 14, but it also exposed many problems, such as too much noise and strong vibration, and the steam engine may explode at any time. When the train started, smoke billowed, and sparks splashed when the wheels rubbed the rails; The man sitting in the car was covered in smoke and knocked unconscious. The flame of the steam engine scorched all the trees nearby.

However, Stephenson is not discouraged, but keeps improving. He installed damping springs under the carriage, used wrought iron instead of pig iron as the rail material, laid pebbles under the sleepers, increased the number of wheels in the front and carriage, and installed a steam engine in the front to reduce the damage in dangerous situations.

By 1825, when Stephenson tried to run Voyager, the situation improved considerably. Voyager is towing six coal trucks and 20 carriages full of passengers, with a load of 90 tons and a speed of 15 miles per hour. This spectacular scene attracted many people to watch. There are people on both sides of the railway; Others rode horses and walked in front of the train with red flags. With the sound of the train, it announced the arrival of the railway era to the whole world.

1829, Stephenson successfully trial-produced a more advanced "rocket" locomotive.

(The above contents of Stephen Sun and the Steam Locomotive are from the history textbook published by Beijing Normal University. )

Means of transport

1769, Nikolai Joseph Juno demonstrated the feasibility of the automatic steam car for the first time with his "steam car". This car is the first car. This car is not very useful as a means of transportation, but it is good for towing farm tools.

Until the early 20th century, steam engine cars could still compete with other driving modes. Most cars today are driven by internal combustion engines. The biggest disadvantage of a steam engine car is that it takes at least 30 seconds to get enough pressure.