Four Stroke Engine

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Engine working

Four stroke configuration


Four-stroke cycle (or Otto cycle)
1. Intake
2. Compression
3. Power
4. Exhaust
As their name implies, operation of four stroke internal combustion engines have four basic steps that repeat with every two revolutions of the engine: 1. Intake
o Combustible mixtures are emplaced in the combustion chamber 2. Compression
o The mixtures are placed under pressure
3. Power
o The mixture is burnt, almost invariably a deflagration, although a few systems involve detonation. The hot mixture is expanded, pressing on and moving parts of the engine and performing useful work. 4. Exhaust

o The cooled combustion products are exhausted into the atmosphere Many engines overlap these steps in time; jet engines do all steps simultaneously at different parts of the engines.

[edit] Combustion

All internal combustion engines depend on the exothermic chemical process of combustion: the reaction of a fuel, typically with oxygen from the air (though it is possible to inject nitrous oxide in order to do more of the same thing and gain a power boost). The combustion process typically results in the production of a great quantity of heat, as well as the production of steam and carbon dioxide and other chemicals at very high temperature; the temperature reached is determined by the chemical make up of the fuel and oxidisers (see stoichiometry). The most common modern fuels are made up of hydrocarbons and are derived mostly from fossil fuels (petroleum). Fossil fuels include diesel fuel, gasoline and petroleum gas, and the rarer use of propane. Except for the fuel delivery components, most internal combustion engines that are designed for gasoline use can run on natural gas or liquefied petroleum gases without major modifications. Large diesels can run with air mixed with gases and a pilot diesel fuel ignition injection. Liquid and gaseous biofuels, such as ethanol...
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