What Is Steam Engine?- Overview, Parts, and Working

Heat water to its boiling point and it changes from being a liquid to become the gas or water vapor we know as steam. When water becomes steam its volume increases about 1,600 times, that expansion is full of energy.

An engine is a machine that converts energy into mechanical force or motion that can turn pistons and wheels. The purpose of an engine is to provide power, a steam engine provides mechanical power by using the energy of steam.

Steam engines were the first successful engines invented and were the driving force behind the industrial revolution. They have been used to power the first trains, ships, factories, and even cars.

And while steam engines were definitely important in the past, they also now have a new future in supplying us with power with geothermal energy sources.

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.

How Does a Steam Engine Work?

To understand a basic steam engine, let’s take the example of the steam engine found in an old steam locomotive like the one depicted. The basic parts of the steam engine in a locomotive would be a boiler, slide valve, cylinder, steam reservoir, piston, and a drive wheel.

When heated, water turns to an invisible vapor known as steam. The volume of water expands as it turns to steam inside the boiler, creating a high pressure. The expansion of steam pushes the pistons that connect to the driving wheels that operate the locomotive.

1. Coal or oil are the fuels used for heating the water (coal is shown in the diagram). Coal is carried in the tender of the locomotive and is hand-shoveled by the fireman into the firebox. Water is carried in the tender in a tank surrounding the coal. The water passes to the locomotive through a device called an injector.
2. By spreading the coal evenly throughout the firebox, the fireman creates a level fire above the grates. Air flows up through the grates allowing the coal to burn hotter. The hot gases released from the coal flow forward through a series of flues or tubes to the front of the locomotive.
3. Water surrounds the outside of the firebox. Heat from the burning coal turns water to steam, which rises to the top of the boiler. The area surrounding the firebox and tubes is the “steam generator” of the locomotive.
4. Steam gathers at the steam dome, the highest point in the boiler. The engineer uses the throttle to regulate the amount of steam being sent to the pistons. A throttle lever in the cab opens and closes the throttle valve in the steam dome.
5. Steam passes to the piston valves which control admission of steam to the cylinders. Once in the piston, the steam expands, pushing it in the opposite direction. At the end of the piston stroke, an exhaust port opens, allowing the steam to escape. Then the process is reversed and repeated in the opposite direction. Steam is admitted to either side of the piston so that it is always under power. A lever in the cab allows the engineer to control the action of the piston valves (direction of locomotive movement, and timing).
6. The pistons push or pull the rods connected to the drive wheels, providing the force needed to move the locomotive.
7. The steam is exhausted through a nozzle and up through the smokebox into the stack. This action produces the “chuff chuff” sound heard when the locomotive is moving. A draft or vacuum results, in pulling air through the firebox grates to induce combustion of the coal. Both exhausted steam and coal smoke travel up through the stack.

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.

Steam Engines Today

It may be surprising to know that 95 percent of nuclear power plants use steam engines to generate power. Yes, the radioactive fuel rods in a nuclear power plant are used just like coal in a steam locomotive to boil water and create steam energy.

However, the disposal of spent radioactive fuel rods, the vulnerability of the nuclear power plants to earthquakes and other issues leaves the public and the environment at great risk.

Geothermal power is power generated using steam produced by heat emanating from the molten core of the earth. Geothermal power plants are relatively green technology.

Kaldara Green Energy, a Norwegian/Icelandic manufacturer of geothermal electrical power production equipment, has been the major innovator in the field.

Solar thermal power plants can also use steam turbines to generate their power.

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