Abstract: The distribution of air within the combustor liner that participates in combustion reactions is pivotal for the design of gas turbine combustors. To address this, a novel Computational Fluid Dynamics (CFD)-based methodology has been developed to quantitatively assess the distribution of air that is consumed by combustion. This approach involves the derivation of spatial and temporal transport equations for the air mixture fraction and the oxygen mass fraction across each air stream within the combustor liner. These equations are then integrated with an LES-FGM solver, specifically tailored for the simulation of turbulent spray combustion within gas turbine combustors. By analyzing the simulation outcomes, both the airflow rate and the proportion of air involved in combustion for each stream can be determined. The method was validated using a conventional swirling combustor, demonstrating its ability to effectively monitor the air mixture fraction and oxygen mass fraction within individual air streams. The method also provided the proportion of air consumed by combustion in each stream and its spatial distribution. The combustion air distribution derived from these simulations aligns with the established design principles of conventional swirling combustors, confirming the effectiveness of this approach for evaluating gas turbine combustors.