Dual-fuel injector with a double pipe sleeve gaseus fuel flow path

A dual-fuel burning gas turbine combustor comprising:

• a liquid fuel and a gaseous fuel, in which a diffusive combustion burner that burns the liquid fuel and the gaseous fuel is placed at the center of the axis of the gas turbine combustor and
• a plurality of pre-mixing combustion burners that burns the liquid fuel and the gaseous fuel are placed on an outer circumferential side of the diffusive combustion burner, each pre-mixing combustion burner comprising:
• a liquid fuel nozzle through which the liquid fuel is supplied;
• a plurality of gaseous fuel spray holes through which the gaseous fuel is supplied;
• a plurality of air holes through which a combustion air is supplied;
• and
• a gaseous fuel flow path through which the gaseous fuel is supplied to the plurality of gaseous fuel spray holes, the fuel spray holes and the air holes are being placed on an outer circumferential side of the liquid fuel nozzle, and a pre-mixing chamber in which the gaseous fuel and the combustion air are mixed together;
• an end cover which is provided with the pre-mixing combustion burner at the downstream side thereof, and a flow path through which the gaseous fuel supplied from the gaseous fuel flow path configured to provide gaseous fuel flow, is formed within the end cover;
• and
• a double pipe sleeve which is attached to at a connected portion between the flow path disposed in the end cover and the gaseous fuel flow path disposed in the pre-mixing combustion burner;
• wherein, the double pipe sleeve which is provided with a cylindrical inner sleeve through which the gaseous fuel flows down from the flow path disposed in the end cover to a gaseous fuel flow path disposed in the pre-mixing combustion burner, an outer sleeve which is disposed to be concentric with the cylindrical inner sleeve positioned on an outer circumferential side of the cylindrical inner sleeve;
• the cylindrical inner sleeve and the outer sleeve of the double pipe sleeve both extend and overlap each other approximately between an upstream portion of the gaseous fuel flow path and a downstream portion of the gaseous fuel flow path;
• the outer sleeve of the double pipe sleeve has a first end that is attached to an inner wall surface of the pre-mixing combustion burner by a first welded portion approximately at the downstream portion of the gaseous fuel flow path;
• the cylindrical inner sleeve of the double pipe sleeve has a first end that is attached to a second end of the outer sleeve of the double pipe sleeve by a second welded portion at the upstream portion of the gaseous fuel flow path;
• and
• a circular spacing is formed between and enclosed by the cylindrical inner sleeve and the outer sleeve of the double pipe sleeve.