HOW AN INTERNAL COMBUSTION ENGINE WORKS

Our world is full of wonderful and amazing stuff. Some of these wonders are around us but we do not seem to notice. One funny thing is, some of these things are things we use day in, day out. I am sure some ideas are already coming to mind about what I am talking about!

In our daily activities, we encounter a series of devices and equipment that by all means make life easier and make our activities smooth. One of these awesome gifts of science is the automobile. Quite recently, science has gifted us with series of automobiles that can be referred to as “auto” in all sense of the word; the driverless vehicles, but that’s not the point of discuss for today. Today I want to talk about the internal combustion engine, something that has been a part of human history for a long time.

^{[Wikipedia Creative Common Image]Source:
Internal combustion engine pistons of partial cross-sectional view}

THE INTERNAL COMBUSTION ENGINE
To eliminate ambiguity, I would like to define the internal combustion engine in the simplest way possible. Let’s do it one word after the other;

INTERNAL is defined by merriam-webster dictionary as ”existing or situated within the limits of a surface of something”

COMBUSTION is defined by oxford dictionaries as the process of burning something or a rapid combustion of a substance with oxygen, involving production of heat and light.

ENGINE as defined by Wikipedia is a machine designed to convert one form of energy into mechanical energy.

Putting these three definitions together, you would agree with me that an internal combustion engine is

a machine that converts energy gotten from burning something within itself into mechanical energy!

I think I did well on that one.

In more professional terms, an internal combustion engine is a heat engine in which combustion of fuels occur and the energy derived therein is harnessed as mechanical energy and used for useful work. Typically, an internal combustion engine is fed with a fuel which is ignited and made to burn in the engine. The energy released by burning the fuel is then used as work.

The internal combustion engine is usually referred to as a heat engine based on the fact that heat energy is generated during its operation. Internal combustion engines are found in quite a number of machines that we use today, some of which include; the automobile (of course), motorcycle, generators, aircraft, lawnmowers, leaf blowers, outboard motors, etc.

You would agree with me that the fact that we have internal combustion engines means that there are external combustion engines in which the combustion occurs externally such as steam engines and the likes.

CLASSIFICATION

Internal combustion engines can be classified based on different parameters as follows:

• based on the orientation. It can be classified into: reciprocating and rotary engines (wankel)

• based on the number of strokes, classification include: two stroke, four stroke, six stroke

• based on the type of ignition: compression ignition and spark ignition

• based on the combustion method: intermittent and continuous combustion

• based on the type of fuel used: petrol, diesel, gas

HOW THE INTERNAL COMBUSTION ENGINE WORKS

Of all classifications, the most common form of the internal combustion engine is the reciprocating engine. For the sake of this post, I would be explaining the internal combustion engine using the four stroke reciprocating engine.

COMPONENTS
The component parts of the reciprocating engine include:

• The cylinder: this is more or less the chamber in which the combustion process takes place. It is the central working part of the engine. The cylinder houses the piston and is the space within which the piston travels.
  The number of cylinders in an engine can vary from 1 to 16 or even more depending on the application.

• The piston: the piston is located inside the cylinder and is made gas tight by attaching some rings around it. The piston moves up and down within the cylinder. Its main purpose is to transfer the force exerted by the energy released by combustion of the fuel in the cylinder to the crank shaft via the piston rod.

• The connecting rod: as the name implies, it connects the piston to the crank shaft.

• The crankshaft: the crankshaft is the component that receives the force exerted by the piston and converts the reciprocating motion to rotary motion. The crankshaft is attached to the connecting rod.

• The flywheel: this component is a wheel attached to the crank and serves the purpose of storing the rotational energy generated. This energy is stored so that it would be used to perform a function in the cycle of operation of the engine. It also performs the function of balancing the system and also to smoothen out the power delivery over each rotation of the crank.

• The valves: the valves are a pair of equally important components of the engine. They are of two types; the intake valves that open to allow the introduction of the working fluid into the combustion chamber and the exhaust valves which open to allow the combustion products escape from the cylinder. These valves work (open and close) in rhythm with the position of the piston in the cylinder. The opening and closing of these valves are facilitated by cam shaft movement

WORKING CYCLE

Bringing all these components together and attaching some other auxiliaries, the engine works in a repeated cycle.
Recall the classification based on number of strokes?

The different configurations of the internal combustion engine complete the cycle based on the number of strokes they have. In order words, the four stroke engine completes four strokes in one cycle of operation while the two stroke engine does it in just two strokes. By strokes I mean the upward or downward movement of the piston.

As stated earlier, I would explain the working cycle using the four stroke engine. Each stroke occurs as follows:

• STROKE 1(downward movement of the piston): this stroke is known as the intake, induction or suction stroke. At this point, the intake valve is open and the fuel (or compressed air for diesel engines) is introduced into the cylinder. The fuel is usually referred to as “charge” and it fills the space due to the vacuum created as a result of downward movement of the piston.

• STROKE 2 (upward movement of the piston): this stroke is known as the compression stroke and as the name implies, the piston moves upward to compress the charge that has been introduced during the intake stroke. At this point, both the intake and exhaust valves are closed.

• STROKE 3 (piston moving downward): at the point when the piston is just about moving downward, a spark (or a jet of fuel for diesel engines) is introduced to the compressed charge and the charge explodes and the energy released forces the piston downwards. This stroke is also known as the power stroke because this is the stroke that involves the release of energy which drives the engine.

• STROKE 4 (piston moving upward): this stroke is also called the exhaust stroke because this stroke involves the opening of the exhaust valve and the combustion products (exhaust) are pushed out as a result of the upward movement of the piston.

In one sentence, this is how the four stroke internal combustion engine works;

The piston sucks in fuel mixed with air, and then compresses it, the compressed fuel is ignited and it explodes thereby pushing the piston down the cylinder. The piston then returns upward one more time thereby expelling the burnt gases.
At this point, the cycle starts over from the beginning. (cool isn’t it?)

Although there are a lot of systems attached to the engine to ensure its continuous operation, the illustration given above applies to the basic operation of the internal combustion engine. Take an automobile vehicle for instance, the engine is supported by the lubrication system which is intended to ensure smooth movement between two mating parts in the engine and to also eliminate the ignition system which is saddled with the function of ensuring the provision of spark into the combustion chamber when required, the cooling system which ensures the temperature of the engine is maintained at the level required. And a number of other systems that ensure communication between man and machine (isn’t technology awesome?)

CONCLUSION
Internal combustion engines find application in the automobile industry, the power generation industry, the aviation industry and a host of others. The involvement of these engines in the advancement of technology over time cannot be over emphasized and I would like to name them man’s best engine.

REFERENCES
intenal combustion engines | internal combustion engine | how car engines work | I.C.E