Cooling system of ring segment and gas turbine

A cooling system of ring segment that is formed from a plurality of segment bodies that are arranged in the circumferential direction to form a ring shape, and that cools a ring segment of a gas turbine that is arranged in a casing so that the inner peripheral surface of each segment body is kept a fixed distance from the tip of a turbine blades,

• wherein the segment body comprising:
• a collision plate that has a small hole that causes cooling air that is supplied from outside of the casing to be blown out and performs impingement cooling of the main body of the segment body;
• a cooling space that is enclosed by the collision plate and the main body of the segment body;
• a first cavity that, among the side end portions of the segment body along the rotation direction of the rotating shaft, is arranged in the axial direction of the rotating shaft along at least one side end portion, and receives from the cooling space the cooling air after the impingement cooling;
• and
• a first cooling passage, of which one end communicates with the first cavity, and the other end blows out the cooling air from an opening that is arranged in the side end portions into combustion gas;
• wherein the openings of the first cooling passages being arranged so that the arrangement pitch of the openings becomes smaller or the opening area of the openings becomes larger on the upstream in the flow direction of the combustion gas than the openings on the downstream, and are arranged so that the arrangement pitch of the openings becomes larger or the opening area of the openings becomes smaller on the downstream in the flow direction of the combustion gas than the openings on the upstream.