Air-cooled swirlerhead
A combustor for a gas turbine engine is disclosed which is able to operate with high combustion efficiency, and low nitrous oxide emissions during gas turbine operations. The combustor consists of a can-type configuration which combusts fuel premixed with air and delivers the hot gases to a turbine. Fuel is premixed with air through a swirler and is delivered to the combustor with a high degree of swirl motion about a central axis. This swirling mixture of reactants is conveyed downstream through a flow path that expands; the mixture reacts, and establishes an upstream central recirculation flow along the central axis. A cooling assembly is located on the swirler co-linear with the central axis in which cooler air is conveyed into the prechamber between the recirculation flow and the swirler surface.
1. A combustor for combusting a mixture of fuel and air, the combustor comprising:
a swirler for receiving a flow of air and a flow of fuel, the fuel and air being mixed together under the influence of the swirler, the swirler imparting a swirling flow to the fuel/air mixture, the swirler having a central channel therethrough;
a prechamber in fluid communication with the swirler for receiving the swirling fuel/air mixture, the prechamber being a cylindrical member defining a central axis, the prechamber imparting an axial flow to the swirling fuel/air mixture in a downstream direction along the central axis, thereby creating a vortex flow of the fuel/air mixture having a low pressure region along the central axis; and
a combustion chamber in fluid communication with and downstream of the prechamber, the combustion chamber having a greater flow area than a flow area of the prechamber, thereby permitting the vortex to expand radially and create a recirculation flow in which combustion products from combustion of the fuel/air within the combustion chamber are drawn upstream along the central axis back into the prechamber,
a cooling assembly received in the channel, the cooling assembly defining an axis that is co-linear with the central axis of the prechamber, the cooling assembly in fluid communication with a source of air that is cooler than the recirculation flow and directing the cooler air in a downstream direction into the prechamber thereby creating a cooling flow.
2. The combustor of claim 1 , further comprising a recuperator generating recuperated air and in fluid communication with said cooling assembly.
3. The combustor of claim 1 , wherein the cooling assembly is formed of a first material and the swirler is formed of a second material different from the first material.
4. The combustor of claim 3 , wherein the first material has a first coefficient of thermal expansion and the second material has a second coefficient of thermal expansion different from the first coefficient of thermal expansion.
5. The combustor of claim 1 , wherein the cooling flow and the recirculation flow interact to form a stagnation plane in between the swirler and the recirculation flow.
6. The combustor of claim 1 , wherein the swirler includes an inner side facing the prechamber, wherein the cooling assembly is approximately flush with the inner side.
7. The combustor of claim 6 , wherein the swirler includes a plurality of flow guides on the inner side, the flow guides defining flow paths between adjacent flow guides, wherein the cooling assembly is upstream of the flow guides.
8. The combustor of claim 6 , wherein the cooling assembly includes a perforated shield covering the central channel.
9. The combustor of claim 8 , wherein the perforated shield includes a plurality of nozzles.
10. The combustor of claim 8 , wherein the shield is coupled to a mounting member that is fixedly mounted to the swirler.
11. A method of combusting fuel and air in a gas turbine engine, the method comprising:
premixing fuel and air to a relatively uniform mixture adjacent a swirler surface at a front end portion of a combustor;
injecting the fuel/air mixture into a prechamber cylinder of the combustor in a swirling motion about a centerline of the prechamber, thereby creating a vortex flow having swirling and axial motion, the vortex flow having a low pressure region at the centerline;
conveying the vortex flow axially in a downstream direction into a combustion cylinder having greater flow area than a flow area of the prechamber;
expanding the vortex flow into the combustion chamber, wherein chemical reaction of the fuel and air occurs to form hot products of combustion;
as a result of said expansion, forming a recirculation flow at the centerline wherein the hot products are drawn upstream into the prechamber; and
conveying air through the swirler at the centerline in a downstream direction into the prechamber, said conveyed air being cooler than the recirculation flow.
12. The method of claim 11 , as a result of conveying said air, forming a stagnation plane between the swirler surface and the recirculation flow.
13. The method of claim 11 , wherein conveying said air further comprises conveying air through a plurality of nozzles into the prechamber.