How The Heart of the Car Beats – The Internal Combustion Engine
As histories go, the creation of the internal combustion engine is attributed to a number of individuals, and if you delve into it, usually results in a long (somewhat boring) laundry list of names and achievements. However, while you’re here, let’s have a glance at some of the more prominent names. Keep in mind that one of the most important differences between today’s contemporary internal combustion engines and the earlier designs is the use of compression (specifically in-cylinder combustion). Let’s get to it!
1509: Leonardo da Vinci (Assassin’s Creed anyone?) described a compression-less engine.
1794: Fast forward almost 200 years before one of the first compression-less engines would be built by Robert Street and would dominate for nearly a century.
1876: Jump almost a century, and we meet Nikolaus Otto who together with Gottlieb Daimler and William Maybach developed the first practical 4-stroke cycle (which became known as the Otto cycle) engine using in-cylinder compression.
1879: Karl Benz developed a reliable 2-stroke engine based on Nikolaus Otto’s design and then designed and built his version of the 4-stroke engine which were used in the first automobiles in production.
1882: James Atkinson created the Atkinson cycle engine, a more efficient engine than the Otto version at the expense of power.
1896: Rudolf Diesel built and operated the first reliable diesel engine.
Through the tireless efforts of other inventors, these first engines were improved to become one of the most commonly used for power where mobility is required as in automobiles, heavy equipment and other portable machinery.
Now that we know where it came from, let’s have a look at the general principles of operation for an internal combustion engine. However, there are many types of internal combustion engines are beyond the scope of this article. Interested readers are advised to try this page for more information: http://www.newworldencyclopedia.org/entry/Internal_combustion_engine. What we aim to do in this article is establish the general workings to give us a better idea of how that highly advanced piece of machinery that powers your car works.
One of the most familiar types of internal combustion engines, used in everything from automobiles to lawnmowers, is the reciprocating, spark-ignited, four-stroke gasoline engine.
In these engines, the space where combustion occurs is called the cylinder. Cylinders can be arranged in one of four ways: 1) a single row where cylinders are vertical (in-line engine), 2) a double row where opposing cylinders converge in a V-shape (V-engine), 3) a double zigzag row where alternate pairs of cylinders converge in two Vs (W-engine), and 4) two horizontal, opposed rows (opposed, pancake, flat, or boxer engine). The top of the cylinder is closed by the head (a metal cover) bolted onto it and which is where the spark plug is located to provide ignition. Each cylinder has a piston which slides up and down. The bottom of the piston has a joint which is connected to the crankshaft where the reciprocating (up-down) motions of the pistons rotate the crankshaft which then turns the drive wheels of the vehicle. Your engine speed is the number of crankshaft revolutions per minute. Two other openings in the cylinders are the ports – the intake port allows the air-gas mixture to enter the chamber, and the exhaust port vents the products of combustion. The air-gas mixture ratio is regulated by the throttle which mixes the air at different ratios depending on the needs of the engine at that point.
All fine and good, you say! So what! How does all of this come together to produce energy? Well, let’s take a look.
All internal combustion engines use the exothermic chemical process of combustion to generate energy. Once successfully burnt, the combustion products, typically hot gases, have more available energy than the original unburnt air-gas mixture (which has higher chemical energy). This higher available energy is used by the piston in the engine to produce work which in turn is used to do something (e.g. turning the drive shaft of a car). For a four-stroke engine (the most common kind), a single cycle (comprising of the intake, compression, power, and exhaust strokes) takes place over 4 strokes of a piston, done in 2 engine revolutions. Engines with multiple cylinders will evenly stagger the cycles for to produce smooth operation, with each individual cylinders going through the full cycle in any two engine revolutions.
1. The intake/induction stroke: The intake port opens and the descending piston draws in the air-gas mixture.
2. At the bottom of the stroke, the intake port closes, and piston drives upwards on the compression stroke, compressing or forcing the air-gas mixture into the small space at the top of the cylinder. The higher the compression ratio (ratio of the volume of the cylinder when the cylinder is at the bottom to when the cylinder is at the top) the more powerful the engine and the more efficient.
3. Just before reaching the top, the spark plug fires, igniting the air-gas mixture which turns into hot, expanding gas that forces the piston downwards on the power stroke.
4. As the piston reaches the bottom again, the exhaust port opens, allowing the piston to force the results of combustion (mainly carbon dioxide, carbon monoxide, nitrogen oxides, and unburned hydrocarbons) on the upward exhaust stroke.
And that’s it! You now know a little bit about how the revving hunk of metal that powers your car works. I hope you enjoyed the read and that you learn something!