Pilot burner assembly with pilot-air supply

1. A pilot burner assembly for a combustion volume of a gas turbine engine, the pilot burner assembly comprising:

a pilot burner having a generally cylindrical body disposed about a longitudinal axis of the pilot burner and comprising a burner face disposed to face the combustion volume, the burner face having a plurality of pilot-fuel injection holes adapted to provide a pilot-fuel to the combustion volume for combustion;

a first fuel supply line being a pilot-fuel supply line fluidly connected to the plurality of the pilot-fuel injection holes and adapted to provide the pilot-fuel to the plurality of the pilot-fuel injection holes;

a pilot-air supply line adapted to provide a pilot-air to the pilot burner and wherein the pilot-air is supplied to the combustion volume through the burner face; and

a premixing chamber, wherein the premixing chamber is fluidly connected to the pilot-fuel supply line to receive the pilot-fuel, and is further fluidly connected to the pilot-air supply line to receive the pilot-air, wherein the premixing chamber is arranged to form a pilot mixture of pilot-fuel/pilot-air premix within the premixing chamber before the pilot mixture is supplied to the combustion volume and wherein the premixing chamber has an outlet fluidly connected to the plurality of the pilot-fuel injection holes to provide the pilot-fuel/pilot-air premix to the combustion volume for combustion,

a second fuel supply line to supply a main-fuel to a main swirler to generate a main mixture of main-fuel/main-air arranged to enter the combustion volume through the swirler, wherein the pilot mixture of pilot-fuel/pilot-air formed within the premixing chamber is formed separate from the main mixture of main-fuel/main-air generated by the swirler,

wherein the outlet of the premixing chamber is defined by a conduit extending between the premixing chamber and the burner face,

wherein the premixing chamber is in the body of the pilot burner, and wherein the pilot mixture of the pilot-fuel/pilot-air premix is conveyed by way of the conduit to be ejected from the plurality of pilot-fuel injection holes in the burner face into the combustion volume, wherein the pilot mixture of the pilot-fuel/pilot-air premix being ejected from the plurality of pilot-fuel holes is arranged to mix with the main mixture of main-fuel/main-air entering through the main swirler to form a combined mixture of the pilot mixture and the main mixture in the combustion volume.

2. The pilot burner assembly according to claim 1 , wherein the pilot-air supply line is fluidly connected to the pilot-fuel supply line for providing the pilot-air into the pilot-fuel supply line to form a pilot-fuel/pilot-air premix within the pilot-fuel supply line, and wherein the plurality of the pilot-fuel injection holes are adapted to provide the pilot-fuel/pilot-air premix to the combustion volume for combustion.

3. The pilot burner assembly according to claim 1 , wherein the burner face comprises a plurality of pilot-air injection holes fluidly connected to the pilot-air supply line and adapted to provide the pilot-air to the combustion volume.

4. The pilot burner assembly according to claim 3 , wherein the plurality of the pilot-fuel injection holes are arranged on the burner face circumferentially around a longitudinal axis of the pilot burner, and wherein the plurality of the pilot-air injection holes are arranged circumferentially around the longitudinal axis.

5. The pilot burner assembly according to claim 4 , wherein the plurality of the pilot-fuel injection holes and the plurality of the pilot-air injection holes are congruently arranged around the longitudinal axis and wherein the plurality of the pilot-fuel injection holes and the plurality of the pilot-air injection holes are alternately placed on the burner face.

6. The pilot burner assembly according to claim 4 , wherein the pilot burner assembly comprises a lip overhanging axially above an annular region of the burner face such that an annular pocket is formed axially between the burner face and the lip, wherein the annular region of the burner face is positioned radially outward with respect to the longitudinal axis and wherein the pilot-fuel injection holes and the plurality of the pilot-air injection holes are positioned within the annular region of the burner face.

7. The pilot burner assembly according to claim 6 , further comprising:

a radial swirler adapted to generate a swirling mix of a main-fuel and air entering the combustion volume through the main swirler, the radial swirler comprising:

an annular base plate having a radially inner edge; and

a plurality of swirler vanes disposed on the annular base plate arranged circumferentially spaced apart and extending radially around the longitudinal axis of the pilot burner, wherein the swirler vanes include radially inner thin ends and wherein the radially inner thin ends are set back from the radially inner edge of the annular base plate thereby to define an annular ledge on the annular base plate immediately radially outward of the radially inner edge of the annular base plate; and

wherein the lip is formed of the annular ledge of the annular base plate.

8. The pilot burner assembly according to claim 3 , wherein a size of the plurality of the pilot-air injection holes is smaller than a size of the plurality of the pilot-fuel injection holes.

9. The pilot burner assembly according to claim 1 , further comprising: a pilot-air valve adapted to control a flow of the pilot-air in the pilot-air supply line towards the pilot burner.

10. The pilot burner assembly according to claim 9 , further comprising: a control unit adapted to direct the pilot-air valve to control the flow of the pilot-air in the pilot-air supply line towards the pilot burner such that the pilot-fuel and the pilot-air are provided to the combustion volume in a desired ratio of the pilot-fuel and the pilot-air.

11. A gas turbine engine comprising:

at least one pilot burner assembly, the at least one pilot burner assembly according to claim 1 .

12. A gas turbine engine according to claim 11

wherein the main swirler is a radial swirler comprising an annular array of swirler vanes arranged circumferentially spaced around an annular base plate so as to form, between adjacent swirler vanes, slots, wherein the pilot burner assembly is generally surrounded by the radial swirler.