Abstract: A novel and improved system for cooling and reducing combustion noise in a gas turbine combustor is disclosed. The system includes a flow sleeve for a gas turbine combustor comprising a tubular portion and a conical portion, with a plurality of flow straighteners extending radially inward and between the tubular and conical portions and a plurality of rows of cooling holes extending about the flow sleeve, and an aft ring secured to the outlet end of the conical portion, where the aft ring includes an overlapping piston ring that is able to expand or contract in diameter. A combustion liner extends through the flow sleeve and engages an inlet of a transition duct while the piston ring of the flow sleeve also engages the transition duct to form a seal.