A steam engine is a device that produces mechanical energy through the use of water vapor. In particular, thermal energy is transformed into mechanical energy by means of steam. Heat is typically produced by burning fossil fuels, particularly coal, but it can also come from wood, hydrocarbons or nuclear reactions.
From a more physical point of view we can define a steam engine as a machine capable of converting the heat energy of steam into physical work. It is a conversion between two types of energy.
How does a steam engine work?
The basic operation of a steam engine is based on heating water to obtain steam and taking advantage of steam pressure to drive a mechanical mechanism. The mechanical mechanism is basically an alternative or rotary engine depending on the application of the steam engine.
An essential part of the system that includes the steam engine is the steam generator, or the boiler. In the boiler water vapor is obtained by administering heat to liquid water. The steam is then sent to the engine, which can be of two basic types: alternative or rotary. Alternative engines are used in locomotion machines. Rotary type motors are used to drive turbines.
In the alternative engine, steam moves the actuating valves that allow the two sides of each piston to explode. Each motor rotation has two active phases. In internal combustion thermal engines there is generally an expansion every 4 phases ( 4-stroke engine).
From the second half of 1800 almost all steam engines used two, three and even four cylinders in series for double and triple expansion engines.
In particular, the triple expansion solution was universally adopted by all ships in the second half of the 800 and the first 900. For example, the Titanic ocean liner was equipped with two triple expansion steam engines, one for each of the two four-cylinder side propellers, one high pressure, one intermediate pressure and two low pressure. In the place of the central propeller was connected to a steam turbine driven by very low pressure steam discharged from the two alternative engines.
Only the turbine solution (adopted starting with military ships since 1905) would have completely supplanted in marine alternative engines before being replaced by internal combustion engines and gas turbines. Steam turbines remain in use especially in power plants as a driving force for the operation of three-phase alternators.
In fact, in traditional applications, today the steam engine has been almost completely replaced by the internal combustion engine. Regarding the steam engine, the thermal engine is more compact and powerful and does not require the preheating phase to put the boiler under pressure.
What was the first steam engine?
The first commercial steam engine was a water pump, developed in 1698 by Thomas Savery. Savery used condensation steam to create a vacuum that raised the water from below and then used vapor pressure to raise it further.
Small engines were effective, although larger models were problematic. They had a limited elevation height and were prone to boiler explosions. Savery's engine was used in mines, pumping stations and water supply to hydraulic wheels that operated textile machinery. Savery's steam engine was low cost. Bento de Moura Portugal introduced an improvement to the construction of Savery "so that it is able to function on its own". It continued to be manufactured until the end of the 18th century. It was still known that an engine was running in 1820.
Later the first piston steam engine appeared: The first commercially successful engine that could transmit continuous power to a machine was the atmospheric engine, invented by Thomas Newcomen around 1712. Newcomen improved Savery's steam pump, using a piston like Papin proposed.
Papin steam machines
It was not until the end of the 18th century that there were no reliable and efficient steam engines when the first serious attempts at naval propulsion were carried out using steam. In 1707 the French inventor Denis Papin designed a ship, moved by the force of steam, with the intention of making the crossing from Kassel, in Germany, to London.
Denis Papin did in medical studies in Angers. He previously worked with Christian Huygens in Leiden, where he tries to develop an air pump. In 1679 he invented the pressure cooker, at the time of deposit, the patent with the words present here digester makes a lot of digestible amount of food, including hard meat. After working for some time with Robert Boyle, he returned later with Huygens in 1680. After a stay in Venice as director of practices at the 'Ambrosio Sarrotti Academy, and then at the Royal Society of London, he was appointed professor of mathematics in Marburg
At this point, from the experience of the pressure cooker, Papin builds his first steam engine: a steamboat in 1707. But this magnificent invention involved many controversies for the boatmen who threatened to destroy the ship. Papin later returned to England, where, despite new research, resources are declining.
Last review: February 28, 2020