What is the air that passes through the combustion chamber in excess of that required for complete combustion known as?

The term for the air that passes through the combustion chamber in excess of what is necessary for complete combustion is known as "excess air." This concept is crucial in the context of combustion processes because, while the stoichiometric (or theoretical) amount of air is required for optimal combustion efficiency, operational conditions often demand more air to ensure that the fuel burns completely.

Using excess air helps to reduce the formation of harmful byproducts, such as carbon monoxide and unburned hydrocarbons, thereby producing a cleaner burn. However, too much excess air can lead to a decrease in thermal efficiency since the additional air can carry away more heat.

The other terms listed describe different aspects of combustion but do not specifically refer to this excess. Draft air relates to the air drawn into the system due to pressure differences, pre-mixed air refers to air mixed with fuel before entering the combustion chamber, and combustion enhancement air suggests an active role in improving combustion characteristics rather than simply being in excess. Understanding the role of excess air helps in optimizing combustion processes for efficiency and emissions control.