Open rotor gas turbine engine with adaptive turbine clearance control system and method

A method of actively controlling rotor tip clearance in a gas turbine engine disposed in a nacelle, the gas turbine engine including an open rotor propulsion system, a compressor section, a combustion section, a turbine section having a rotor stage, and a turbine case clearance control segment disposed radially outside of the rotor stage, the method comprising:

• providing a turbine active clearance control system that includes a first valve, a heat exchanger, and a second valve, wherein the first valve is disposed upstream of and in fluid communication with the heat exchanger and the second valve;
• using the first valve to receive an exterior air flow extracted from an exterior of the nacelle, and to provide the exterior air flow to a heat exchanger, or to the second valve, or to both;
• wherein the heat exchanger is configured to permit heat transfer within the heat exchanger between the exterior air flow provided to the heat exchanger and a compressor bleed flow extracted from the compressor section and provided to the heat exchanger to produce a flow of conditioned air;
• using the second valve to receive the exterior air flow from the first valve and to receive the flow of conditioned air from the heat exchanger;
• and
• operating the turbine active clearance control system in a heating mode or in a cooling mode, wherein the heating mode includes controlling the second valve to provide the flow of conditioned air, or a combined air flow that includes the flow of conditioned air and the exterior air flow from the first valve, to the turbine case clearance control segment, the turbine active clearance control system including a turbine segment valve, the turbine segment valve configured to vary the flow of conditioned air, the combined air flow or the exterior air flow provided to the turbine case clearance control segment.