A combustor having an ion transport membrane therein and an adjustable swirler, which is mechanically connected at an inlet of a combustion zone of the combustor; a combustion system comprising the combustor, a feedback control system adapted to adjust swirler blades of the combustor based on a compositional variation of a fuel stream, and a plurality of feedback control systems to control operational variables within the combustor for an efficient oxy-combustion; and a process for combusting a fuel stream via the combustion system. Various embodiments of the combustor, the combustion system, and the process for combusting the fuel stream are disclosed.