What does "excess air" refer to in gas turbine operations?

In gas turbine operations, "excess air" refers to the additional air supplied beyond the theoretical amount needed for complete combustion of the fuel. This concept is crucial in ensuring that combustion occurs efficiently and effectively; an adequate amount of air is necessary to completely burn the fuel, but beyond that theoretical requirement, excess air is introduced to ensure all fuel is consumed.

Using excess air helps achieve a more stable flame and reduces the production of carbon monoxide and unburned hydrocarbons, contributing to lower emissions. While having too little air can lead to incomplete combustion, having an appropriate level of excess air optimizes performance and enhances the overall reliability of the gas turbine system.

The other options discuss different aspects of combustion and air supply but do not accurately define excess air in the context of gas turbine operations. For example, the amount of air needed for complete combustion pertains to stoichiometric ratios, while unused air in the combustion chamber refers more to the efficiency of the combustion process and not the intentional addition of air beyond what is necessary.