Effect of gravity on stability of a swirl flame of a premixed methane-air mixture

Stability of a swirl flame of a premixed methane-air mixture under various gravity conditions is studied. Charts of stable combustion at normal and reverse gravity in the coordinates of the flow velocity and equivalence ratio. It is shown that the limits of stable combustion remain unchanged regardless of using a swirler with and without the central body, but the flame geometries are different. Swirlers are found to produce a minor effect on the flame blowout conditions, especially under the normal gravity condition. It is demonstrated that a swirler allows obtaining a rich lifted flame under the normal gravity condition and a lean lifted flame under the reverse gravity condition. It is found that dilution of the mixture with the fuel leads to expansion of the boundary of combustion stability under the reverse gravity condition as compared to the situation under the normal gravity condition.