COOLING DEVICE, COMBUSTOR, AND GAS TURBINE

PROBLEM TO BE SOLVED: To cool a cylindrical flow path in which a high temperature fluid flows when necessary, without requiring temperature monitoring.SOLUTION: This cooling device includes a cover member 2 for covering an outer periphery of an outer peripheral wall of a tail pipe 133 in which the high temperature fluid flows in an axis S direction to open/close a flow of cooling air to the outer peripheral wall of the tail pipe 133. The cooling device opens the flow of cooling air to the tail pipe 133 side by a position change with the cover member 2 according to thermal expansion of the tail pipe 133 itself in the axis S direction due to a high temperature time of combustion gas flowing in the tail pipe 133, and closes the flow of cooling air to the tail pipe 133 side by a position change with the cover member 2 according to contraction of the tail pipe 133 itself in the axis S direction due to a low temperature time of combustion gas flowing in the tail pipe 133.