Combustor and gas turbine

A combustor configured to generate a combustion gas by combusting a mixture of a fuel and a compressed gas, the combustor comprising:

• a plurality of fuel nozzles extending in parallel to each other, wherein each of the plurality of fuel nozzles is configured to inject fuel toward a first side in a direction of a respective axis of each of the plurality of fuel nozzles;
• and
• a pipe plate having a plurality of air holes that are formed in the pipe plate, wherein a respective tip end portion of each of the plurality of fuel nozzles is inserted into a respective air hole of the plurality of air holes, and the respective tip end portion of each of the plurality of fuel nozzles has
• a tip end surface formed at a first side of the respective tip end portion and the fuel is injected from an opening at the tip end surface,
• a single step surface formed at a second side of the respective tip end portion and having an annular shape that is expanded from a tip end outer peripheral surface to a radial outer edge in a radial direction relative to the direction of the respective axis, and
• an upstream side outer peripheral surface connected to the radial outer edge of the single step surface, wherein the tip end surface faces the first side in the direction of the respective axis,
• wherein the respective air hole of the plurality of air holes has an inner diameter that is larger than an outer diameter of the tip end surface of the respective tip end portion of each of the plurality of fuel nozzles, the respective air hole of the plurality of air holes being extended in the direction of the respective axis of each of the plurality of fuel nozzles,
• wherein, for the respective tip end portion of each of the plurality of fuel nozzles, the annular shape of the single step surface is centered on the respective nozzle-axis of each of the plurality of fuel nozzles,
• wherein, for the respective tip end portion of each of the plurality of fuel nozzles, the single step surface is located inside the respective air hole,
• wherein, for the respective tip end portion of each of the plurality of fuel nozzles, the outer diameter of the tip end surface is smaller than an outer diameter of the tip end outer peripheral surface at the single step surface, and
• wherein, around the respective tip end portion of each of the plurality of fuel nozzles, an air flow is introduced into the respective air hole of the plurality of air holes along the upstream side outer peripheral surface of the respective tip end portion of each of the plurality of fuel nozzles.