THE 5 MAIN TYPES OF STEAM ENGINES - TECHNOLOGY - 2025

The different types of steam engines have undergone many changes throughout history and technology has continually allowed them to evolve in a remarkable way.

Essentially, steam engines are external combustion engines that convert the thermal energy of water vapor into mechanical energy. They have been used to power pumps, locomotives, ships and tractors, being at the time essential for the Industrial Revolution. Currently they are used for the generation of electrical energy using steam turbines.

A steam engine consists of a boiler that is used to boil water and produce steam. The steam expands and pushes a piston or turbine, the movement of which does the work of turning the wheels or driving other machinery.

The first steam engine was devised by Heron of Alexandria in the 1st century and was called Eolipila. It consisted of a hollow sphere connected to a boiler to which two curved tubes were attached. The sphere was filled with water that was boiled, causing the steam to be expelled through the tubes at high speed, making the ball spin.

Although the eolipila did not have a practical purpose, it undoubtedly represents the first implementation of steam as a source of propulsion.

Heron's Aeolipian

However, most systems that use steam can be divided into two types: piston machines and steam turbines.

Main types of steam engines

1- Plunger machines

Plunger machines use pressurized steam. Through double-acting pistons, pressurized steam enters alternately on each side while on the other it is released or sent to a condenser.

The energy is absorbed by a slide bar sealed against the escape of steam. This rod, in turn, drives a connecting rod connected to a crank to convert the reciprocating motion into rotary motion.

In addition, another crank is used to drive the valve gear, usually through a mechanism that allows reversal of the rotary movement.

When using a pair of double acting pistons, the crank advance is offset by a 90 degree angle. This ensures that the motor will always run, no matter what position the crank is in.

2- Multiple expansion motors

Another type of steam engine uses several single-acting cylinders that progressively increase in diameter and movement. High pressure steam from the boiler is used to drive the first piston of smaller diameter down.

In the upward movement, the partially expanded steam is driven into a second cylinder that is beginning its downward movement. This generates a further expansion of the relatively high pressure released in the first chamber.

Also, the intermediate chamber discharges to the final chamber, which in turn is released to a condenser. A modification of this type of engine incorporates two smaller pistons in the last chamber.

The development of this type of engine was important for its use in steam ships, since the condenser, when recovering a little of the power, again converted the steam into water for its reuse in the boiler.

Terrestrial steam engines could exhaust much of their steam and be refilled from a fresh water tower, but at sea this was not possible.

Before and during World War II, the expansion engine was used in marine vehicles that did not need to go at high speed. However, when more speed was required, it was replaced by the steam turbine.

3- Uniflow or uniform flow motor

Another type of piston machine is the uniflow or uniform flow motor. This type of engine uses steam that only flows in one direction in each half of the cylinder.

Thermal efficiency is achieved by having a temperature gradient across the cylinder. Steam always enters the hot ends of the cylinder and exits through openings in the center of the cooler.

This results in a reduction in the relative heating and cooling of the cylinder walls.

In uniflow engines, the inlet of steam is usually controlled by poppet valves (which function similarly to those used in internal combustion engines) that are actuated by a camshaft.

Inlet valves open to admit steam when minimum expansion volume is reached at the beginning of movement.

At a specific moment during the turn of the crank, the steam enters and the cap inlet closes, allowing the continuous expansion of the steam, actuating the piston.

At the end of the stroke, the piston will discover a ring of exhaust holes around the center of the cylinder.

These holes are connected to the condenser, lowering the pressure in the chamber causing a quick release. The continuous rotation of the crank is what moves the piston.

4- Steam turbines

High-power steam turbines use a series of rotating discs that contain a kind of propeller-type blades on their outer edge. These movable discs or rotors alternate with stationary rings or stators, attached to the turbine structure to redirect the steam flow.

Due to the high speed of operation, such turbines are normally connected to a reduction gear to drive another mechanism such as a ship's propeller.

Steam turbines are more durable and require less maintenance than piston machines. They also produce smoother rotational forces on their output shaft, which contributes to lower maintenance requirements and less wear.

The main use of steam turbines is in electricity generating stations where their high speed of operation is an advantage and their relative volume is not a disadvantage.

They are also used in marine applications, powering large vessels and submarines. Virtually all nuclear power plants generate electricity by heating water and feeding steam turbines.

5- Propulsion engines

There is an underwater propulsion engine that uses high-pressure steam to draw water through an intake at the front and expel it at high speed at the rear.

When the steam condenses on the water, it creates a shock wave that expels the water from behind.

To improve engine efficiency, the engine draws in air through a vent in front of the steam jet, which creates air bubbles and changes the way the steam mixes with the water.

References

1. Marshall Brain (2017). "How Steam Engines Work". Retrieved June 14, 2017 at science.howstuffworks.com.
2. New World Encyclopedia (2015). "Steam engine". Retrieved on June 14, 2017 at newworldencyclopedia.org.
3. SOS Children (2008-2009). "Steam engine". Retrieved on June 14, 2017 at cs.mcgill.ca.
4. Woodford, Chris (2017). "Steam engines". Retrieved on June 14, 2017 at explainthatstuff.com.