An airflow control system for a combined cycle power generation system according to an embodiment includes: a compressor component of a gas turbine system for generating an excess flow of air; a mixing area for receiving an exhaust gas stream produced by the gas turbine system; and an air extraction system for extracting at least a portion of the excess flow of air generated by the compressor component of the gas turbine system to provide bypass air, and for diverting the bypass air into the mixing area to reduce a temperature of the exhaust gas stream; wherein the reduced temperature exhaust gas stream is provided to a heat recovery steam generator.