Luftbränslemängd

Luftbränslemängd, often translated as air-fuel ratio (AFR), is a fundamental concept in internal combustion engines and combustion processes. It refers to the mass ratio of air to fuel present in a combustion mixture. This ratio is critical for efficient and complete combustion, as well as for controlling engine performance and emissions.

There are generally three types of air-fuel ratios: stoichiometric, rich, and lean. A stoichiometric AFR is the ideal ratio where all the fuel can be completely burned by the available oxygen in the air. For gasoline, this ratio is approximately 14.7:1 by mass. A rich mixture has more fuel than is needed for complete combustion, meaning there is less air relative to fuel. Conversely, a lean mixture has less fuel than is needed for complete combustion, with more air relative to fuel.

Engine control units (ECUs) in modern vehicles constantly monitor and adjust the air-fuel mixture to optimize performance, fuel economy, and emissions based on various operating conditions such as engine load, temperature, and speed. Sensors like oxygen sensors (lambda sensors) provide feedback to the ECU about the exhaust gas composition, allowing for precise adjustments to the AFR. Deviations from the optimal AFR can lead to reduced power, increased fuel consumption, and higher levels of harmful emissions like carbon monoxide, hydrocarbons, and nitrogen oxides. Understanding and controlling the air-fuel mixture is therefore paramount in engine design and tuning.