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Air–fuel ratio (AFR) is the mass ratio of air to a solid, liquid, or gaseous fuel present in a combustion process. The combustion may take place in a controlled manner such as in an internal combustion engine or industrial furnace, or may result in an explosion (e.g., a dust explosion). The air–fuel ratio determines whether a mixture is ...
Lean-burn refers to the burning of fuel with an excess of air in an internal combustion engine. In lean-burn engines the air–fuel ratio may be as lean as 65:1 (by mass). The air / fuel ratio needed to stoichiometrically combust gasoline, by contrast, is 14.64:1. The excess of air in a lean-burn engine emits far less hydrocarbons.
(The fuel-air ratio (FAR) is the reciprocal of the air-fuel ratio (AFR).) λ is the air-fuel equivalence ratio, and λ=1 means that it is assumed that the fuel and the oxidising agent (oxygen in air) are present in exactly the correct proportions so that they are both fully consumed in the reaction.
Any mixture of methane and air will therefore lie on the straight line between pure methane and pure air – this is shown as the blue air-line. The upper and lower flammability limits of methane in air are located on this line, as shown (labelled UEL and LEL, respectively). The stoichiometric combustion of methane is: CH 4 + 2O 2 → CO 2 + 2H ...
A stratified charge can allow for slightly higher compression ratios without "knock," and leaner air/fuel ratio than in conventional internal combustion engines. Conventionally, a four-stroke (petrol or gasoline) Otto cycle engine is fueled by drawing a mixture of air and fuel into the combustion chamber during the intake stroke
Whereas flame velocity is generally used for a fuel, a related term is explosive velocity, which is the same relationship measured for an explosive. Combustion engineers differentiate between the laminar flame speed and turbulent flame speed. Flame speed is typically measured in m/s, cm/s, etc. The physical phenomena of combustion can be found.
If you've been having trouble with any of the connections or words in Friday's puzzle, you're not alone and these hints should definitely help you out. Plus, I'll reveal the answers further down ...
A high-octane-rated fuel, such as liquefied petroleum gas (LPG), has an overall lower power output at the typical 10:1 compression ratio of an engine design optimized for gasoline fuel. An engine tuned for LPG fuel via higher compression ratios (typically 12:1) improves the power output.