Combustor arrangement having arranged in an upstream to downstream flow sequence a radial swirler, pre-chamber with a convergent portion and a combustion chamber
A combustor for a gas turbine engine having a central axis about which is arranged in flow sequence a radial swirler, a pre-chamber partly defined by a wall and a combustion chamber. The radial swirler has a base plate having an annular array of vanes and fuel injectors arranged to direct an air/fuel mixture radially inwardly and tangentially to create a vortex that flows through the pre-chamber and into the combustion chamber. The pre-chamber has a portion which is convergent in a downstream direction.
1. A combustor for a gas turbine engine, the combustor comprising:
a central axis about which are arranged in an upstream to downstream flow sequence
a radial swirler,
a pre-chamber partly defined by a wall and
a combustion chamber,
wherein the radial swirler comprises a base plate having an annular array of vanes and fuel injectors arranged to deliver an air/fuel mixture radially inwardly and tangentially to an inlet of the pre-chamber to create a vortex that flows through the pre-chamber to an outlet of the pre-chamber and then into the combustion chamber,
wherein a fuel comprises a mixture having a hydrogen gas content, wherein the hydrogen gas content is at least 5% by volume of the fuel,
wherein the base plate comprises a pilot surface which faces the pre-chamber and bounds an upstream axial extent of the pre-chamber,
wherein the pre-chamber has a portion which is convergent in a downstream direction and is configured to accelerate the air/fuel mixture to a velocity effective to prevent flashback of a flame from the combustion chamber into the radial swirler, and
wherein the pre-chamber has an inlet area and an outlet area and a ratio of the inlet area to the outlet area is between 1.45 and 1.70.
2. The combustor as claimed in claim 1 ,
wherein the pre-chamber is generally frustro-conical.
3. The combustor as claimed in claim 1 ,
wherein the pre-chamber has straight walls in an axial aspect.
4. The combustor as claimed in claim 1 ,
wherein the pre-chamber has curved walls in an axial aspect.
5. The combustor as claimed in claim 1 ,
wherein the pre-chamber has an axial length (L) and an effective inlet diameter (D), a ratio of the axial length to effective inlet diameter is between 0.45 and 0.55.
6. The combustor as claimed in claim 1 ,
wherein the portion extends over an entire axial length of the pre-chamber.
7. The combustor as claimed in claim 5 ,
wherein a rate of change of area of the portion of the pre-chamber is variable.
8. The combustor as claimed in claim 5 ,
wherein the rate of change of area of the convergent portion of the pre-chamber is constant.
9. The combustor as claimed in claim 5 ,
wherein the pre-chamber has at least a first portion and a second portion arranged in downstream flow sequence between the inlet and the outlet, the rate of change of area increases over the first portion and decreases over the second portion.
10. The combustor as claimed in claim 9 ,
wherein the first portion extends greater than 0.5 L from the inlet of the pre-chamber.
11. The combustor as claimed in claim 9 ,
wherein the pre-chamber has a third portion downstream of the second portion, the third portion is parallel or divergent.
12. The combustor as claimed in claim 1 ,
wherein the vortex has a swirl number between 0.3 and 0.8.
13. The combustor as claimed in claim 12 ,
wherein the swirl number is between 0.3 and 0.5.
14. The combustor as claimed in claim 1 ,
wherein the hydrogen gas content is up to 80% by volume.
15. The combustor as claimed in claim 1 ,
wherein the hydrogen gas content is in a range of 5-40% by volume.