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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 ).
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.
Where %O 2 is the percent O 2 by volume, dry basis, %CO 2 is the percent CO 2 by volume, dry basis, and 20.9 is the percent O 2 by volume in ambient air. The Fuel factor can be corrected for the amount of CO, by adding the percent CO on a dry basis to the CO 2, and subtracting half of the percent CO from the O 2. [2]
The fuel being burnt in the lean charge is therefore not 'knock' or octane restricted. This type of stratification therefore can utilise a wide variety of fuels; the specific energy output being dependent only on the calorific value of the fuel. A relatively rich air/fuel mixture is directed to the spark-plug using multi-hole injectors.
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Assume a two-stream problem having one portion of the boundary the fuel stream with fuel mass fraction =, and another portion of the boundary the oxidizer stream with oxidizer mass fraction =,. For example, if the oxidizer stream is air and the fuel stream contains only the fuel, then Y O , O = 0.232 {\displaystyle Y_{O,O}=0.232} and Y F , F ...
The high compression ratio in the auxiliary combustion chamber causes the auto-ignition of the homogeneous lean air-fuel mixture therein (no spark plug required); the burnt gas bursts - through some "transfer ports", just before the TDC - into the main combustion chamber triggering its auto-ignition.
Next, it is also a given that within that range of acceptable mixtures, there is only one ratio that is the ideal air-fuel ratio at that time, given the throttle position set by the pilot. In summary, it can be said that the ideal carburetor provides the correct air-fuel mixture ratio, as required by the engine, under all of its operating ...