A system for supplying a working fluid to a combustor (16) includes a fuel nozzle and a combustion chamber (40) downstream from the fuel nozzle. A flow sleeve (50) circumferentially surrounds the combustion chamber (40), and fuel injectors (60) provide fluid communication to the combustion chamber (40). A distribution manifold (62) circumferentially surrounds the fuel injectors (60) and defines an annular plenum (64). A fluid passage (66) through the distribution manifold (62) provides fluid communication through the distribution manifold (62). A radial cross-sectional area (70) of the annular plenum (64) varies around the flow sleeve (50). A method for supplying a working fluid to a combustor (16) includes flowing a working fluid through a combustion chamber (40), diverting a portion of the working fluid (24) through a distribution manifold (62) that circumferentially surrounds fuel injectors (60) circumferentially arranged around the combustion chamber (40), and changing at least one of a pressure or flow rate of the diverted portion of the working fluid.