The combustion engine is an invention which can stand equally alongside any of mankind's most remarkable
achievements, as both a humanitarian milestone and a technological hammer blow. It's a machine which has
brought power and mobility to uncountable billions of people all over this planet, enabled industries to
blossom, nations to grow, and communication to flourish internationally.
Rough History of the Combustion Engine
The first recorded mention of a machine resembling a piston-cylinder-crankshaft mechanism - the
mechanism which makes up the moving parts of an internal combustion engine - is in Al-Jazari's
imaginatively named 'Book of Knowledge of Ingenious Mechanical Devices', way back in 1206. Although it
wasn't quite the same as a modern combustion engine assembly, his invention incorporated a crankshaft and
a connecting rod; ideas which are central to modern internal combustion engines. The machine Al-Jazari
described may have already been invented by the Han Chinese, but Al-Jazari's is certainly the earliest
recording of it.
Piston based machines and crankshafts continued to be used during the Islamic Golden Age, an age of
significant technological achievements and crowded by scientific discoveries. They were mainly used for
pumping water, almost exclusively as parts of irrigation systems. The concept didn't really catch on in
Europe, despite being reinvented by Leonardo Da Vinci in 1509. It wasn't until Sir Samuel Morland, an
English aristocrat with time on his hands, used gunpowder to drive water pumps by creating a vacuum with
an explosion in 1675, that the concept of the internal combustion engine became inevitable. The concept of
harnessing small explosions and turning the energy into rotational or lateral force appeared in all manner
of objects after Morland's innovation. In 1780 a toy gun was produced which ignited hydrogen and air
inside what was effectively a modern cylinder, in which the projectile acted as the piston. This idea was
developed by the Swiss engineer Francois Isaac de Rivaz into an identifiable internal combustion engine.
Throughout the 19th century engine patents were applied for left, right and centre, and in 1838 William
Barnet designed the first cylinder engine which used compression assisted ignition. The compression inside
the cylinder was the key concept which had been missing from the internal combustion engine, and once
in-cylinder compression was invented subsequent developments and other uses for it started to propagate.
By 1870, the first internal combustion engine was put on a hand cart -inventing the car. By the end of
that decade Karl Benz had been building the engines industriously, and in 1892 Rudolf Diesel had built his
first engine, burning coal dust - this was the beginning of the diesel's ascension. The use of the
cylinder and the importance of in-cylinder compression had now become ubiquitous, and the power and
potential of internal combustion was recognised.
How Does Internal Combustion Work?
Internal combustion works by harnessing the energy released in small controlled explosions, and
converting that energy into lateral and, eventually, rotational force.
The explosions occur inside the engine - hence 'internal combustion'. It's caused by the ignition of
fuel inside a cylinder. Usually the fuel is petrol or diesel, in which case the ignition is either cause
by a spark plug or by compression and very high temperatures. The explosion of the fuel pushes the piston
down the cylinder with a lot of force. The piston is attached to a crankshaft, which is made to rotate as
the piston moves down the cylinder. The fumes left in the cylinder by the explosion are then removed by
the exhaust, and the process begins again. The process of internal combustion can be broken down into four
primary stages.
- Intake
The fuel is introduced into the cylinder, often as a fine spray. This happens during the piston's downstroke, which helps to suck the gas into the cylinder. It only takes a tiny bit of fuel to create the necessary energy conversion.
- Compression
The fuel is compressed in the upstroke of the cylinder which makes it more volatile, and therefore provides a more powerful explosion. It's the compression which defines the diesel engine; diesel fuel is ignited by compression alone.
- Combustion
This stage is the ignition itself. In a petrol engine, the fuel is ignited by a sparkplug when the piston is at the top of its cycle. In a diesel no sparkplug is required, and the compression by the piston is enough to ignite the fuel mixture.
- Exhaust
The residual gases caused by the combustion are forced out of the cylinder, at least in part by the upstroke of the cylinder.
The cycle then repeats itself, and could theoretically continue forever providing there was enough fuel.
A petrol engine requires a battery to power the sparkplugs, a diesel does not. (In fact, a diesel engine
car would probably run just fine without a battery - they are added by diesel manufacturers to power
luxuries, not essentials.) The four stages described above are known as the Otto cycle - or the
four-stroke combustion cycle. There are two-, five- and six-stroke variants, but they all work along
similar principles and the four-stroke is by some distance the most common type of car engine.
Important Parts in a Combustion Engine
Below is a list of some of the more important parts of the internal combustion engine, and some
information about each. It's arranged alphabetically, and it's not a comprehensive list of engine
components. Some engines will use different parts for different jobs, and there are many different
designs, which means that not all the components below will be used by all engines, and not all engine
components are represented below.
- Connecting Rod - The connecting rod - or 'conrod' sometimes - is attached to the piston and connects it to the crankshaft below it, transferring the energy from the cylinder.
- Coolant - The coolant lines the cylinder preventing too much heat escaping from the cylinder into the surrounding mechanics, and preventing the cylinders themselves from overheating. The coolant is often a mineral or castor oil.
- Crankshaft - The Crankshaft in an engine is the component which converts the linear motion created by the pistons into the rotational motion which turns the wheels.
- Cylinder Head - This is where the valves are usually located, and the sparkplug if it's a petrol engine. It contains the combustion chamber; the actual space where the fuel is ignited.
- Engine Block - Increasingly made from aluminium, the engine block is a complicated system of bored holes for the pistons.
- Exhaust Port - The exhaust port is the channel, usually in the cylinder head, through which the exhaust fumes leave the cylinder after the combustion of the fuel mixture.
- Exhaust Valve - The exhaust valve covers and blocks the exhaust port until the right time during the ignition cycle: after the combustion and before the next load of fuel is injected into the cylinder.
- Flywheel - The flywheel is a rotating disk attached to the crankshaft, and it's used to steady its rotation. Thanks to its ability to store kinetic energy, it can maintain the rotation of the crankshaft between the surges in power caused by the combustion.
- Intake Port - The intake port is the channel through which the fuel enters the cylinder. It's usually found in the cylinder head.
- Intake Valve - This valve allows or blocks the movement of fuel into the cylinder. It covers the intake port except when the fuel is to be injected into the cylinder. The intake valve is the subject of much design and improvement, and there are many different ways fuel is introduced to the cylinder across engine designs.
- Oil Sump - The oil sump forms the lower enclosure of a combustion engine, and its purpose is to feed the lubricating systems in the engine.
- Camshaft - The camshaft is a rod which runs the length of the cylinder bank. On the rod are several egg-shaped lobes - called cams. The cams sit above the valves and rotate on the rod; when the pointed end of the cam makes contact with the valve, the cam forces the valve open.
- Piston - The piston is the lump of metal inside the cylinder which travels up and down, transferring the energy of the combustion into the rotational motion of the camshaft. It's made airtight with the cylinder by piston rings, so that no energy can escape.
- Rod Bearing - The rod bearing is the articulated joint which permits the rotational movement of the crankshaft on the end of the connecting rod.
- Spark Plug / Glow Plug - The sparkplug is not present in the diesel engine, because its purpose is to ignite fuel in the cylinder; a different principle from a diesel engine. Glow plugs are used in diesels occasionally to warm the air before it is forced into the cylinder to assist cold starts.