Background and History

The internal combustion engine is one of the most important inventions in modern history. The need for more efficient transportation and machines that could produce movement were some of the reasons this machine came into existence. It functions by burning fuel and turning it into rotational motion, but to understand how it does this, one needs to learn about its predecessor, the external combustion engine, more commonly known as the steam engine. There are few inventions that have had a bigger influence in society than the steam engine, this artifact created by Thomas Savery, initially used to remove water from flooded mines in 1698 (Palermo, 2014), quickly became the heart of the industrial revolution that changed the world forever. Utilizing the steam generated by boiling water lead the world to mass production in factories, locomotives and mines, and opened the doors to millions to inventions that are still used today. The steam engine is known as an external combustion engine because the burning of the fuel, in this case fuel occurs outside the chamber where the power is generated (Palermo, 2014). The fact that locomotives changed the way people looked at transportation, it led  many inventors creating similar engines that burned fuel inside rather than outside in order to fit it inside smaller vehicles that could be used to transport families without the need of tracks, but while most were inefficient or too complex to be useful, in 1876, German engineer Nikolaus Otto (see Figure 1) created an engine that  burned fuel inside and functioned using a 4-stroke process Otto himself had come up with (“Internal Combustion Engine”, 2018). This new engine is known as the first modern internal combustion engine and its 4-stroke process is used to this day. Although there have been many changes and many new sub-types of this engine have been created, the concept has remained the same since its creation.

Parts and Components

The IC (internal combustion) engine is composed of many parts, each with its own function, but all necessary to produce motion using the combustion process. These parts (see Figures 2 & 3) can be paired up in order to understand the process better:

• Piston and cylinder: The piston is a solid cylindrical object that slides in an out of a slightly bigger cylindrical hole called the cylinder. In the space that gets formed in between the top of the piston and the end of the cylinder, the process of combustion occurs, this place is also known as the combustion chamber. The piston is connected to a rotating piece called the crankshaft by a connecting rod.
• Intake and exhaust valves: Inside the combustion chamber there are two valves that open and close as the piston goes up and down. One of them called the intake valve, allows a mixture of air and fuel into the chamber. The other, called the exhaust valve, allows the gas that is produced after the fuel has burned to leave the combustion chamber.
• Spark plug: The spark plug is a small piece in between the two valves. When the intake valve lets fuel into the chamber and the piston is all the way up, this small plug fires a spark that makes the fuel explode and as a result of this explosion the piston is pushed all the way down and then back up to repeat the process.
• Crankshaft: The crankshaft is a rotating piece that connects to the piston. As the piston is pushed up and down by the burning of fuel (combustion) it makes the crankshaft spin and therefore creating rotational motion that can be used to move the machine it’s powering.

How it Works

            Although the part descriptions and pictures give a pretty basic idea of how the engine works, it’s useful to know what combustion in four-strokes mean. The technical definition of combustion is to burn something, but in IC engine terms, it’s the process of burning fuel in the combustion chamber, the IC engine does this process in 4 strokes or steps known as intake, compression, power and exhaust (Figure 4). First the air-fuel mixture comes through the intake valve as the piston comes down (intake), then the piston comes up, decreasing the volume of the chamber and thus increasing the pressure (compression). The spark plugs then makes the fuel explode making the piston come down (power). When the piston is all the way down, the exhaust valve opens and lets the gas from the explosion leave. The piston then comes back on top pushing the gasses out and leaving it at the start position to redo the process (exhaust).

Figure 4: Four-stroke cycle engine with labeled parts, 2007, retrieved from Encyclopedia Britannica.

 

IC Engines in the Modern World

            The internal combustion engine is the most popular type of engine in the modern world, found in automobiles, motorcycles, and even lawnmowers, this machine powers many artifacts used around the world every single day. However, not all IC engines are the same type, with the biggest differences being the power output and size. The two main subtypes are the inline engines and the V engines (see Figure 5); while some of the lesser known include the boxer and the W engines. They all function the same way, but they are built different to benefit the type of machine they are powering. The first thing to remember is that an engine block contains cylinders, and as mentioned earlier, the motion or power is made thanks to the combustion that takes place inside these cylinders. Therefore, the more cylinders the engine block contains, the more power it could produce. However, it also means that it’s going to take up more space and weigh more.

Inline Engines

                The inline engines are the simplest and the first type of IC engines used in vehicles. The reason they are called inline is because the cylinders are in an upright position, next to each other in a straight line. This simple concept is what powers most of the simple daily drive cars, it’s efficient and it’s simple to fix. The number of cylinders determines what type of engine it is. For example, a motorcycle or a lawnmower only requires 2 cylinders to function, which means, if it uses an inline engine, it will be called an inline-2. If a car uses a 6-cylinder inline engine, people will refer to it as inline-six, i6 or straight-six. However, as cars got bigger, so did the need for more powerful engines. Adding more cylinders would mean increasing the length, meaning powerful cars would need to be extremely long. This problem was solved with the invention of the V-type engine.

V-Type Engines

            The way to optimize the space wasted by the straight line of cylinders, was a simple but revolutionary idea. Instead of having all the cylinders at a 90-degree angle, it would save space if half were reclined a certain angle and the other half were reclined the opposite way the same angle, creating 2 lines that look like a V when looked through the front. This reduced the size of engines to almost half, which meant more cylinders could be fit in. Nowadays, muscle cars and trucks use this type of engine for its power, however it’s also more expensive than an inline and much harder to fix and maintain, the extra cylinders also mean it burns more fuel, which is why economy cars prefer the inline. Naming this type of engines is the same way as it was for the inline, just add the number of cylinders at the end. For example, an 8-cylinder one would be called a V8. There is also a W-type engine which is basically two V engines combined in order to create unreal power, an example is the W16 engine which is found only on the fastest cars in the world, such as the Bugatti Veyron and Chiron. The Boxer engine is just a V-type engine in which the cylinders are placed at 180-degree angles, making them horizontal or flat, they save a lot more space inside a car, and provide more stability, but are also harder to maintain.

The Future of IC Engines

            The internal combustion engine is still the most used and manufactured engine in the automotive world, however, while it’s lasted over 150 years, the end might be near for this iconic invention. Electric cars have been on the rise for a while and with more brands starting to replace the conventional gas engine for an electric one, it looks like we’re just a couple of decades away from looking back at IC engines as ancient machines, the same way we look at the steam engine these days. However, all the history that came along with it and the massive number of iconic cars it gave us, will forever be remembered and honored as the golden era of the automotive industry.

References

Brain, M., & Hall-Geisler, K. (2000, April 5) “How Car Engines Work”
HowStuffWorks.com. Retrieved from https://auto.howstuffworks.com/engine.htm

Palermo, E. (2014, March 14). Who Invented the Steam Engine?. LiveScience.com. Retrieved from https://www.livescience.com/44186-who-invented-the-steam-engine.html

The Editors of Encyclopedia Britannica. (1998, July 20). Nikolaus Otto. Encyclopedia Britannica. Retrieved from https://www.britannica.com/biography/Nikolaus-Otto

Micu, A. (2019, June 7). Types of Engines and How They Work. ZmcScience.com. Retrieved from https://www.zmescience.com/science/types-of-engines/

Engine block image. FastTime Motorworks. Retrieved from https://shop.fasttimesmotorworks.com/products/dart-sbc-shp-engine-block

Engine cylinder diagram with labels. Pinterest.  Retrieved from https://www.pinterest.com/pin/70016969190763125/

Engine cylinder configuration diagram. (2012, September 17). Retrieved from http://www.procarcare.com/icarumba/resourcecenter/encyclopedia/icar_resourcecenter_encyclopedia_engine1.asp

Lafayette, C. & Cromer, O. (2019, August 20). Gasoline Engine. Encyclopedia Britannica. Retrieved from https://www.britannica.com/technology/gasoline-engine