Fuel injector, combustor, and gas turbine

A fuel injector comprising:

• an upstream plate;
• a downstream plate installed at a downstream side of the upstream plate and disposed so as to face the upstream plate;
• a cylindrical member formed like a cylinder having upstream and downstream opening ends, and in which a plenum is defined by the upstream plate disposed at the upstream opening end of the cylindrical member and the downstream plate disposed at the downstream opening end of the cylindrical member;
• a fuel tube configured to introduce a fuel gas into the plenum;
• a premix tube formed like a tube having upstream and downstream opening ends and extending so as to pass through the upstream plate and the downstream plate and the plenum, and having a fuel hole for introducing the fuel gas supplied into the plenum, the fuel gas being mixed with air introduced from the upstream opening end of the premix tube;
• and
• a cooling air introduction pipe configured to introduce cooling air into the downstream plate,
• wherein the downstream plate includes:
• an air inlet into which the cooling air is introduced from the cooling air introduction pipe;
• a cooling flow path extending in a direction along a surface of the downstream plate from the air inlet so as to avoid the premix tube;
• a first plate portion having a first surface facing the upstream plate;
• and
• a second plate portion on an upstream side of the first plate portion, the second plate portion including a second surface bonded to the first surface, and the second plate portion including the cooling flow path;
• wherein the cooling flow path is formed as a groove recessed from the second surface toward the upstream plate side, and
• wherein the cooling flow path is configured to avoid communicating with the plenum via the second plate portion.