Lean mixture意思

"Lean mixture" is a term used in the context of combustion, particularly in internal combustion engines (ICEs) and gas turbines. It refers to a mixture of air and fuel where there is less fuel than there is air. This results in a fuel-lean mixture, meaning there is less fuel present per unit of air than in a stoichiometric mixture or a rich mixture.

In an internal combustion engine, the air-fuel mixture is ignited and burns to produce energy. The stoichiometric mixture is the ideal ratio of air to fuel for complete combustion, where all the fuel is burned and produces the maximum possible amount of energy. A lean mixture, on the other hand, has less fuel than the stoichiometric mixture, which can result in less complete combustion and potentially lower efficiency. However, lean mixtures can also offer benefits such as reduced fuel consumption and lower emissions, especially of carbon monoxide (CO) and hydrocarbons (HC).

Lean mixtures are often used in modern engine designs to improve fuel economy and reduce emissions. They can be controlled by the engine management system, which adjusts the fuel injection timing and amount to achieve the desired air-fuel ratio. Lean burn engines are particularly common in gasoline direct injection (GDI) systems and are also used in diesel engines, where they can help to reduce soot emissions through the use of exhaust gas recirculation (EGR).

In the context of gas turbines, lean mixtures are also used to improve efficiency and reduce emissions. Gas turbines can operate with very lean mixtures, which can help to increase their thermal efficiency and reduce the need for expensive and complex after-treatment systems. However, lean mixtures can also be more prone to combustion instability and may require advanced control systems to maintain stable operation.