ice basics

Internal Combustion Engine Operation

All internal combustion engines depend on the chemical process of combustion and explosion, that is the reaction of a fuel with oxygen. See also: stoichiometry

The most common fuels in use today are made up of hydrocarbons and are derived from petroleum. These include the fuels known as diesel, gasoline and liquified petroleum gas. Some have theorized that in the future hydrogen might replace such fuels. The advantage of hydrogen is that its combustion produces only water (the chief disadvantage of using hydrogen is that presently no method exists for efficiently producing it in quantities sufficient to power internal combustion engines on a large scale).

Whatever the choice of fuel, all internal combustion engines rely on the effects of a controlled explosion, where a gaseous fuel reacts with oxygen. The explosion products (hot gases) have more kinetic energy than the original compressed fuel/air mixture (which had higher chemical energy). The kinetic energy is manifested as high temperature and pressure which can be translated into work.

All internal combustion engines must have a means of ignition to promote combustion. Most engines use either an electrical or a compression heating ignition system.

All internal combustion engines are heat engines and thus have a physical upper bound on their efficiency achieved only by the theoretical Carnot heat engine. A few internal-combustion engines that use rotary instead of linear piston motion are known as Wankel engines, Orbital engines or Quasiturbines.

Gasoline (or petrol) engine is a type of engine which is often used for automobiles, small mobile vehicles such as lawnmowers or motorcycles and outboard motors for boats.

To understand the basic idea behind how a reciprocating internal combustion engine works, it is helpful to have a good mental image of how "internal combustion" works. One good example is an old Revolutionary War cannon. You have probably seen these in movies, where the soldiers load the cannon with gun powder and a cannon ball and light it. That is internal combustion, but it is hard to imagine that having anything to do with engines.

Almost all cars currently use what is called a four-stroke combustion cycle to convert gasoline into motion. The four-stroke approach is also known as the Otto cycle, in honor of Nikolaus Otto, who invented it in 1867.

Intake stroke

Compression stroke

Combustion stroke

Exhaust stroke

Basic Engine Parts

Before explaining the operation of the four-stroke engine, some of the internal parts must be identified.

The piston travels up and down in a Reciprocating Motion. The force from the piston is then transferred to the Crankshaft through the connecting rod. The connecting rod converts the reciprocating motion of the piston, to the Rotating Motion at the crankshaft.

An internal combustion engine is essentially a thermodynamically controlled air pump. You pump air in, heat and process it to move a piston, rotor or fan blade to produce work. One of these items, attached to a crankshaft or axle transmits chemical and thermodynamic energy into kinetic energy or motion. After processing and use, the charge is then expelled.
Air is the working fluid of any internal combustion engine. The amount of air we are able to get into an engine is directly related to the amount of power the engine will produce.
An engine is a power source. Engines are used to convert potential energy into kinetic energy to do useful work, converting heat from fuel into the motion of your car.

Cylinder
The core of the engine is the cylinder. The piston moves up and down inside the cylinder. The engine described here has one cylinder. That is typical of most model engines, but some have more than one cylinder (four, six and eight cylinders are available)

Spark/Glow plug
The plug supplies the heat that ignites the air/fuel mixture so that combustion can occur.

Valves
The intake and exhaust valves open at the proper time to let in air and fuel and to let out exhaust. Note that both valves are closed during compression and combustion so that the combustion chamber is sealed.

Piston
A piston is a cylindrical piece of metal that moves up and down inside the cylinder. The fit and finish between it and the cylinder is very sensitive, the better the fit the better the engine. Two methods exist of ensuring this fit is good

Connecting rod
The connecting rod connects the piston to the crankshaft. It can rotate at both ends so that its angle can change as the piston moves and the crankshaft rotates. The connection to the crankshaft is called the big end, and the connection to the piston is called the little end. The inner part of the little end is a steel pin that goes through the piston, this pin is called the gudeon pin.

Crank shaft
The crank shaft turns the piston's up and down motion into circular motion.

The internal combustion engine principle has undergone no significant change to the basic design configuration, most modifications have been made to external components and or the location of the components.