US Patent 8483931 Active pattern factor control for gas turbine engines

A method of actively controlling pattern factor in a gas turbine engine includes the steps of issuing fuel into a combustion chamber of a gas turbine engine through one or more circumferentially disposed fuel injectors, determining an initial circumferential pattern factor in the combustion chamber, and adjusting fuel flow through one or more selected fuel injectors based on the initial circumferential pattern factor, to yield a modified circumferential pattern factor in the combustion chamber. The step of determining the circumferential pattern factor can include the steps of detecting a chemiluminescent signature within the combustor, correlating the chemiluminescent signature to an equivalence ratio, and computing the initial circumferential pattern factor based on the equivalence ratio. Alternatively, the step of determining the circumferential pattern factor can include the steps of measuring temperatures at a plurality of circumferential positions at the combustor exit and computing the initial circumferential pattern factor based on the measured temperatures.