GAS TURBINE COMBUSTOR SYSTEM

A double pipe 60A of an embodiment includes: an outer pipe 70; an inner pipe 80 inserted through an interior of the outer pipe 70 to make high-temperature carbon dioxide flow therethrough; and an opening 72 of the outer pipe 70 which introduces low-temperature carbon dioxide to an annular passage 61 between the outer pipe 70 and the inner pipe 80. The double pipe 60A further includes: an inner pipe protruding part 91 protruding from an outer peripheral surface of the inner pipe 80 to a radial outside; and an outer pipe protruding part 92 protruding from an inner peripheral surface of the outer pipe 70 to a radial inside, the outer pipe protruding part 92 having a fitting groove 93 fitted to the inner pipe protruding part 91 and penetrating in an axial direction.