Fuel injector, combustor, and gas turbine
An injector includes: an upstream support plate into which a fuel gas is to be introduced and which has a shape of a tapered cylinder with a diameter which enlarges; a downstream support plate that defines a plenum at an inner side along with the upstream support plate; and premixing tubes, each of which is supported by the upstream support plate and the downstream support plate and is configured to introduce air. The premixing tubes are disposed in circular rows at equal intervals in a circumferential direction, and portions of the premixing tubes which are located in the plenum include fuel introducing holes.
1. A fuel injector configured to introduce a fuel gas and air from an upstream side in a direction of an axis and to inject a premixed gas of the fuel gas and the air from a downstream side, the fuel injector comprising:
a fuel delivery tube configured to introduce the fuel gas;
an upstream support plate at the upstream side, the upstream support plate being connected with the fuel delivery tube;
a downstream support plate at the downstream side of the upstream support plate;
a plenum having outer limits defined by an end of the fuel delivery tube, the upstream support plate and the downstream support plate; and
premixing tubes configured to introduce the air from the upstream side, to be supplied with the fuel gas from the plenum, to inject the premixed gas from the downstream side, and to be supported on the upstream support plate and the downstream support plate,
wherein the upstream support plate has a shape whose diameter gradually with a diameter which enlarges toward the downstream side in the direction of the axis such that a diameter of the plenum also enlarges toward the downstream side in the direction of the axis, and
wherein the premixing tubes extend straight from an upstream end configured to introduce the air to a downstream end configured to inject the premixed gas.
2. The fuel injector according to claim 1 , wherein an interior of the upstream support plate has a hollow shape.
3. The fuel injector according to claim 1 , wherein the upstream support plate has the shape of a tapered tube.
4. The fuel injector according to claim 1 , wherein lengths of the premixing tubes in the direction of the axis are shortened toward an outer side in a radial direction.
5. The fuel injector according to claim 1 , wherein a length of the plenum in each row in the direction of the axis is configured such that a flow velocity of the fuel gas circulating in circumferential spaces between the premixing tubes in a radial direction is constant.
6. The fuel injector according to claim 1 , further comprising a fuel guide configured to be fixed to an upstream side face of the downstream support plate in the plenum, and configured to guide the fuel gas toward an outer side in a radial direction.
7. The fuel injector according to claim 1 , wherein each of the premixing tubes has a same cross-sectional shape.
8. The fuel injector according to claim 6 , wherein the fuel guide has a conical shape.
9. The fuel injector according to claim 1 , wherein the premixing tubes protrude toward an outer side of the plenum relative to at least one of the upstream support plate and the downstream support plate in the direction of the axis.
10. The fuel injector according to claim 9 , wherein the downstream sides of the premixing tubes protrude relative to the downstream support plate, and the premixing tubes are fixed such that the upstream sides of the premixing tubes are flush with the upstream support plate without protruding from the upstream support plate.