What Is Steam Engine?- Overview, Parts and Working

What is a Steam Engine?

A steam engine is an engine that uses steam from boiling water to make it move. The steam pushes on the engine parts to make them move. Steam engines can power many kinds of machines including vehicles and electric generators.

Steam engines were used in mine pumps starting in the early 1700s century and were much improved by James Watt in the 1770s. They were very important during the Industrial Revolution where they replaced horses, windmills, and watermills to work machines.

The first steam engines were piston engines. The steam pressure pushed on a piston which made it move along a cylinder and so they had a reciprocal (back-and-forth) motion. This could move a pump directly or work a crank to turn a wheel and work a machine. They operated at low pressure and had to be very big to make a lot of power.

Steam engines were used in factories to work machines and in mines to move pumps. Later smaller engines were built that could move railway locomotives and steamboats.

The steam to power a steam engine is made in a boiler that heats water to make steam. In most places fire heats the boiler. Fuel for the fire may be wood, coal, or petroleum. Nuclear energy or solar energy may be used instead of fire. The steam coming out of the boiler applies the force on a piston.

A valve sends the steam to one end of the piston, then the other, to make it move backwards and forwards. The moving piston pushes and pulls the piston rod, crosshead and connecting rod, to turn wheels or drive other machinery. The heavy spinning flywheel smooths out the power from the piston. The governor controls the speed of the engine.

Today many steam engines are still at work. During the 20th century the pistons were replaced by turbines which spin like a windmill pushed by jets of steam. These turn faster with more energy efficiency than the original kinds of piston steam engines.

They are used in power plants to operate generators which make electricity. Steam turbines also power some ships. The boilers of steam turbines can be heated by many different types of fuel, even a nuclear reactor in some power stations and warships.

Who Invented the Steam Engine?

The Steam Engine was invented by Thomas Newcomen in 1712. He experimented for 10 years to develop the first truly successful steam engine to drive a pump to remove water from mines and developed a more efficient steam engine with a piston separating the condensing steam from the water.

In 1698 Thomas Savery patented a pump with hand-operated valves to raise water from mines by suction produced by condensing steam.

In 1765 James Watt greatly improved the Newcomen engine by adding a separate condenser to avoid heating and cooling the cylinder with each stroke. Watt then developed a new engine that rotated a shaft instead of providing the simple up-and-down motion of the pump, and he added many other improvements to produce a practical power plant.

steam engine

How Does a Steam Engine Work?

A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder.

This pushing force can be transformed, by a connecting rod and crank, into rotational force for work. The term “steam engine” is generally applied only to reciprocating engines as just described, not to the steam turbine.

Steam engines are external combustion engines, where the working fluid is separated from the combustion products. The ideal thermodynamic cycle used to analyze this process is called the Rankine cycle.

In general usage, the term steam engine can refer to either complete steam plants (including boilers etc.), such as railway steam locomotives and portable engines, or may refer to the piston or turbine machinery alone, as in the beam engine and stationary steam engine.

Parts of Steam Engine

  • Firebox: This is where the fuel is burned to create heat.
  • Boiler: Lindy uses a fire tube boiler. Hot gases produced in the firebox are pulled through a rack of tubes in the boiler. The tubes heat the water that surrounds them to produce steam. The steam collects in the steam dome on the top of the boiler.
  • Steam Dome: Inside the steam dome are the regulator valve, safety valve, and whistle. The regulator valve is attached to the throttle in the cab. The engineer uses the throttle to control the quantity of steam delivered to the cylinders. The whistle is a four-chime, 1925 Baldwin whistle which blows by the steam pressure. The safety valve opens to release steam when the pressure becomes too high.
  • Valves, Cylinders, and Pistons: The steam is converted to mechanical energy in the cylinders. Steam under pressure is passed through cylinder valves into a chamber and drives the piston. Lindy, like most locomotives, uses double-action cylinders. This achieves twice the power by alternately introducing steam on either side of the piston so the piston rod is both pushed and pulled, generating power on both strokes.
  • Rods: The piston is aligned in the cylinder by a crosshead running on a guide. The crosshead carries the small end of the connecting rod. The other end, the big end, transmits the power to the wheels with the crank pin. Lindy, like most locomotives, has more than one set of driving wheels to share the power generated by the double-action cylinders. Cranks on either side of the locomotive are offset by 90° to spread the power over a complete revolution of the wheels.
  • Smokebox: Spent steam is released from the cylinders through the blast pipe below the stack. This arrangement produces a reduction in pressure in the smokebox which draws the firebox gases through the boiler tubes. The harder the locomotive works, the more gas is drawn through the tubes, generating more steam.
  • The Stack: The spent steam from the blast pipe mixes with the gases from the boiler tubes and exits through the stack. The harder the locomotive works, the more gases and steam comes out the stack.
  • Cab: The train crew operates the engine from the cab. The fireman’s job is to make the steam by controlling the fire in the firebox and the water supply to the boiler. The engineer uses the steam by operating the throttle and monitors the steam pressure, fuel, and water.
  • Sand Dome: Dome contains sand to be utilized by the engineer by spraying in front or behind driving wheels for traction between the wheels and rail.

Application of Steam Engine

Steam engines were used in all sorts of applications including

  • Factories,
  • Mines,
  • Locomotives,
  • Steamboats.


What is a simple steam engine?

A steam engine is a heat engine that performs mechanical work using steam as its working fluid. 

What have steam engines been used for?

Steam engines were used to power train locomotives, steamboats, machines in factories, equipment in mines, and even automobiles before other kinds of engines were invented. Boiling water in a tea kettle produces steam. Steam can power a steam engine.

How efficient are steam engines?

Steam engines and turbines operate on the Rankine cycle which has a maximum Carnot efficiency of 63% for practical engines, with steam turbine power plants able to achieve efficiency in the mid 40% range.