Since the Industrial Revolution, human technology has advanced rapidly, and our daily lives are filled with machines powered by engines. This article explains what engines are, what they are, and how they are used in real life, and introduces the differences between internal and external combustion engines.
In 1776 AD, the course of human history changed. Engineer James Watt invented the world’s first commercial steam engine, marking the beginning of the Industrial Revolution. Since then, human technology has advanced rapidly. Today, we drive home in our cars, watch the news on TV, and learn that we’ve launched a spacecraft. While many of us know that this mechanical civilization is powered by engines, it’s not always easy to answer exactly which engines are used in our daily lives. In fact, there are so many different types of engines and so many different applications that it’s hard to know them all. In this article, I’ll introduce you to what an engine is, the different types of engines based on their characteristics, and how they function and are used in real life.
First of all, the dictionary defines an engine as “a device that converts heat energy, electrical energy, or hydraulic energy into mechanical power; a heat engine that utilizes mainly heat energy.” Virtually any mechanical device that moves is an engine. There are many different ways to categorize engines, the most common of which is based on the location of the fuel-burning part of the engine, which divides them into internal and external combustion engines.
First, an external combustion engine is one in which the combustion engine is located outside the engine. Because the combustion engine is external, the size of the engine is larger, and the energy from the fuel is lost while it is transferred to the engine, resulting in lower fuel efficiency. However, the larger engine can generate more mechanical power, and with sufficient oxygen supply, complete combustion is possible, reducing emissions. They can also run on a wide variety of fuels and are still used in many parts of the world. The first example of an external combustion engine was the steam engine, but steam turbines and Stirling engines have since taken over.
The principle of a steam turbine, one of the most common external combustion engines in use today, is simple. Hot, high-pressure steam from a combustion chamber turns rotating blades attached to an axle to generate mechanical power. Because steam turbines can recycle steam, the pressure and temperature exerted on the engine are lower than in other engines that use gas or gasoline. They also don’t need to convert reciprocating motion into rotating motion, so they can turn quickly and are often used where great power is needed, such as in ships or power plants. Steam turbines, in particular, are used in warships and merchant ships and are responsible for 80% of the world’s electricity production.
The Stirling engine is designed to run continuously, with two cylinders alternating between heating and cooling. The engine can theoretically run without fuel as long as there is a temperature difference of more than two degrees. They have low noise and vibration, and can also use energy sources such as geothermal or solar power, making them ideal for use in submarines, as a cooling system, or as a heat recycling device.
Internal combustion engines have the combustion chamber located inside the engine, which allows for miniaturization and is more fuel efficient than external combustion engines. Internal combustion engines can be categorized into piston, rotary, and injection propulsion.
Piston engines are similar in principle to Stirling engines, but they work by repeatedly expanding and compressing inside a single cylinder. Gasoline engines compress gasoline and oxygen in a cylinder and explode it with an electric spark to move a piston, while diesel engines operate through the spontaneous combustion of compressed air and fuel. Gasoline engines are easier to maintain and are commonly used in passenger vehicles, while diesel engines are more energy efficient and are used in commercial vehicles and small boats.
A classic example of rotary motion is the gas turbine, which works similarly to a steam turbine but can be lightweight and is often used in airplane jet engines and helicopter propellers.
Finally, jet propulsion is used in rockets. Rockets use fuel and oxidizer injected into an enclosed space, which is then exploded, and the resulting hot, high-pressure exhaust gases are blasted out of a nozzle to create momentum. Rockets are similar to jet engines, but they don’t require an additional oxygen supply, which is why they’re often used in spacecraft and missiles.
So far, we’ve explained the basic characteristics of engines, their classification according to their driving principle, and their real-world applications. Engines can be broadly categorized into external combustion engines and internal combustion engines, each of which is utilized in various fields depending on their advantages and characteristics. Even today, more than 200 years after the invention of the engine, the development of new fuels and high-efficiency, eco-friendly engines continues, making our lives more convenient.
