What is the term used for air that is mixed with natural gas in the burner?

The term that accurately describes air mixed with natural gas in the burner is primary air. In the context of gas combustion, primary air is the air that is needed to facilitate the burning of the gas. This mixture is crucial for achieving efficient combustion, as it provides the necessary oxygen for the gas to ignite and burn properly.

Primary air is introduced directly into the burner along with the natural gas, ensuring that an appropriate ratio of fuel to air is achieved. This mixture is essential for producing a clean flame, which maximizes energy output while minimizing harmful emissions.

In contrast, combustion air generally refers to all the air involved in the combustion process, including both primary air and any additional air needed for complete combustion. Secondary air refers to air that may be introduced after the combustion process has started, often for improving combustion efficiency or reducing emissions. Excess air signifies additional air supplied beyond what is necessary for complete combustion, usually intended for safety and efficiency but not specifically for mixing with the gas in the burner itself.