The steam engine was a major invention of the 18th century that powered industries, railroads, and ships, contributed to the Industrial Revolution, and profoundly changed the world. In this article, we will introduce the history of the steam engine and its basic principles of operation, and discuss its profound impact on the Industrial Revolution and modern civilization.
What is a Steam Engine?
A steam engine is a heat engine that performs mechanical work by burning a fuel (such as coal, wood, or gas) to release the heat energy it contains.
In a steam engine, the fuel combustion process and the water boiler that produces the steam are located outside the body of the engine, so a steam engine is also a type of external combustion engine.
Who Invented the Steam Engine?
The origin of the steam engine is attributed to the British inventor Thomas Newcomen, who in 1712 invented the world's first practical steam engine, which is also known as the atmospheric engine. The emergence of the atmospheric engine laid an important foundation for the technical launch of subsequent steam engines.
After this, the Scottish engineer James Watt made a major improvement to steam in the late 18th century, introducing a separate condenser to condense the steam separately from the cylinder in this steam engine improvement. This key innovation dramatically improved efficiency and made the steam engine more reliable and cost-effective, leading to its widespread use in a wide range of industries.
The invention and development of the steam engine was made possible by the efforts of a number of inventors throughout history, each of whom contributed in their own way. While Thomas Newcomen and James Watt played key roles in the invention of the steam engine, the concept of steam power was explored by earlier inventors and engineers, including Hero of Alexandria in the first century and Thomas Savery in the late 17th century. These early contributions provided a solid foundation for later inventors to develop and improve the steam engine technology, which was continually refined.
How Does a Steam Engine Work?
A steam engine consists of a number of key components that interact with each other to ensure the proper functioning of the steam engine. In the following section, we will first explain some of the common key components of a steam engine:
-Boiler:
The boiler is a tank filled with water, which is heated by the combustion of fuel to produce high pressure steam. This high pressure steam is the power source of the steam engine, and the energy required to move the piston is provided by the boiler.
-Cylinder and Piston:
The Cylinder is a hollow container in which the piston is a movable cylindrical part, and the piston is tightly embedded in the cylinder. Steam generated in the Boiler is introduced into the Cylinder, where it then pushes the piston back and forth, converting the energy of the steam into mechanical motion.
-Connecting Rod and Crankshaft:
Together, the Connecting Rod and Crankshaft are the key components of the engine that convert the reciprocating motion of the piston into the rotating motion of the flywheel. The Connecting Rod is a long metal rod connected to the piston at one end and to the crankshaft at the other. The crankshaft is a metal shaft with eccentric journals, designed to minimize engine vibration and ensure smooth engine operation.
-Flywheel:
A flywheel is a large, heavy disk, usually made of steel or cast iron, that is fixed to the crankshaft of a steam engine. The flywheel is responsible for storing and releasing the kinetic energy of rotational motion in a steam engine.
-Slide Valve / Valve Gear:
The flow of steam in and out of the cylinders is controlled by valves that open and close to allow steam to enter and exit the cylinders at the proper time.
-Condenser:
Condensers are generally box or tube shaped structures. In some types of steam engines, a condenser is used to condense the exhaust steam into liquid water, which is then returned to the boiler to be reheated into steam. This component improves the efficiency of the engine by reducing energy losses.
-Governor:
The Governor usually consists of a rotating shaft and a regulating lever, and is used to automatically adjust the amount of steam entering the cylinder to control the engine speed and maintain a stable engine speed.
After understanding these common main components of a steam engine, let's bring some of them into the common example of a steam locomotive in order to more visually understand the principles associated with the workings of a steam engine.
Steam is produced when water is heated, and as the water turns into steam, the corresponding volume expands in the boiler, creating high pressure. The high pressure steam pushes a piston in a cylinder that is connected to the drive wheel, which enables the steam locomotive to run steadily. This is a rough summary of the operating principle of a steam locomotive, and we will describe the entire operating process in detail below:
1. Coal, which is used to heat the water in the steam locomotive, is stored in the coal and water wagons of the locomotive, and the stoker will use a shovel to shovel the coal into the firebox. At the same time water was stored as well in the coal water car, in a tank around the coal pile, and the water would be conveyed to the locomotive by means of a device known as a water filler.
2. Inside the firebox, the coal is spread evenly and forms a flat firebed above the grate. Air flows upward through the grate to make the coal burn more fully, and the hot gases produced by the combustion enter the front of the locomotive through a series of pipes.
3. The heat from the burning coal converts the water into steam, which rises to the top of the boiler.
4. The steam slowly gathers in the steam ladle, the highest point of the boiler, and the driver can control the opening and closing of the throttle valve in the ladle by means of the throttle lever in the cab, thus regulating the amount of steam delivered to the piston.
5. After the steam enters the steam distribution valve, the steam distribution valve will control the steam entering the cylinder. After the steam is delivered to the piston, the expanding steam pushes the piston in the opposite direction. At the end of the piston's stroke, the exhaust port opens, allowing the steam to be discharged, and the process is then repeated in the opposite direction. Steam enters the piston alternately on both sides of the piston, so that the piston is always in a state of operation, and the driver in the cab controls the direction of travel of the steam locomotive and the timing of the steam distribution valve by means of an operating lever.
6. The piston pushes or pulls the connecting rod connected to the flywheel under the action of steam to provide the steam locomotive with the necessary power for operation.
7. Steam will finally be discharged from the cylinder through the nozzle, into the smoke box and up through the chimney of the steam locomotive to the outside world, this process also produces the steam locomotive running when the “giggling” sound. At the same time, the process of discharging steam will also form part of the vacuum and pumping force to make the air is sucked into the firebox to promote the combustion of coal. This process of exhausting smoke and extracting air enables the steam locomotive to achieve stable combustion and a continuous supply of steam, allowing the locomotive to run steadily.
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