What does "excess air" refer to in the context of combustion?

In the context of combustion, "excess air" refers to the additional air supplied to the combustion process beyond what is theoretically required to completely burn the fuel. This additional air, while it may seem counterintuitive, serves to ensure that combustion is more complete and efficient. When a fuel burns, it ideally requires a certain amount of oxygen; however, in practical applications, adding more air can help to ensure that all the fuel is consumed, reducing the production of harmful emissions such as carbon monoxide and unburned hydrocarbons.

The presence of excess air can therefore improve combustion efficiency by maintaining an optimal temperature and supporting complete oxidation of the fuel. This is particularly important in systems like boilers or furnaces, where controlled combustion is essential for both efficiency and environmental considerations. A well-adjusted amount of excess air can lead to lower emissions and better energy utilization, contributing to overall combustion efficiency.