Compact swirl augmented afterburners for gas turbine engines
View Patent ↗An afterburner apparatus that utilizes a novel swirl generator for rapidly and efficiently atomizing, vaporizing, as necessary, and mixing a fuel and an oxidant. The swirl generator converts an oxidant flow into a turbulent, three-dimensional flowfield into which the fuel is introduced. The swirl generator effects a toroidal outer recirculation zone and a central recirculation zone, which is positioned within the outer recirculation zone. These recirculation zones are configured in a backward-flowing manner that carries heat and combustion byproducts upstream where they are employed to continuously ignite a combustible fuel/oxidizer mixture in adjacent shear layers. The recirculation zones accelerate flame propagation to allow afterburning to be completed in a relatively short length. Inherent with this swirl afterburner concept are design compactness, light weight, lower cost, smooth and efficient combustion, high thrust output, wide flammability limits, continuous operation at stoichiometric fuel/oxidizer mixture ratios, no combustion instabilities, and relatively low pressure losses.
1. An engine assembly comprising:
a gas turbine engine producing an exhaust flow; and
an afterburner apparatus coupled to the gas turbine engine, the afterburner apparatus including a combustor, a swirl generator and a variable area nozzle, the combustor having a combustor inlet, the swirl generator having an inlet housing, a swirl vane pack, a centerbody assembly, and a plurality of fuel injectors, the inlet housing being coupled to the combustor inlet, the inlet housing defining a hollow interior volume therein and serving as a conduit through which at least a portion of the exhaust flow is conducted, the hollow interior volume intersecting the combustor inlet at a dump step wherein the inlet housing has an inner dimension that is smaller than that of the combustor inlet, the swirl vane pack being disposed within the hollow interior volume and having a plurality of vanes, the vanes cooperating to change the velocity of the exhaust flow so that its velocity includes a substantial tangential velocity component, the centerbody assembly being coupled to the swirl vane pack and extending rearwardly therefrom, the plurality of fuel injectors being coupled to at least one of the inlet housing, the swirl vane pack and the centerbody assembly and dispensing a fuel therefrom;
wherein the swirl generator converts the exhaust flow received therein into a swirling, three-dimensional flowfield;
wherein a first portion of the flowfield flows over the dump step to form an outer recirculation zone;
wherein a second portion of the flowfield forms a central recirculation zone that is anchored by an aft end of the centerbody assembly;
wherein a first portion of the fuel mixes with the first portion of the flowfield to fuel the outer recirculation zone;
wherein a second portion of the fuel mixes with the second portion of the flowfield to fuel the central recirculation zone;
wherein a remaining portion of the fuel enters and fuels a core flow; and
wherein the variable area nozzle receives combustion byproducts produced in the combustor by combustion of the fuel and produces propulsive thrust in response thereto.
2. The engine assembly of claim 1 , wherein at least a portion of the fuel injectors are positioned to inject the fuel downstream of the swirl vane pack.
3. The engine assembly of claim 1 , wherein at least one of the fuel injectors is housed in the centerbody assembly.
4. The engine assembly of claim 3 , wherein the centerbody assembly includes at least one injection ring, the injection ring including a plurality of fuel injection sites that are spaced apart about a perimeter of the injection ring.
5. The engine assembly of claim 3 , wherein the at least one of the fuel injectors is coupled to an aft end of the centerbody assembly and is configured to inject fuel in a direction downstream of the centerbody assembly.
6. The engine assembly of claim 1 , wherein the plurality of fuel injectors include a plurality of fuel injection sites that are formed into at least a portion of the vanes of the swirl vane pack.
7. The engine assembly of claim 6 , wherein each vane includes a trailing edge and a lateral surface and wherein the fuel injection sites on a given vane are formed into at least one of the trailing edge and the lateral surface.
8. The engine assembly of claim 1 , wherein the centerbody assembly terminates at an aft bluff boat-tail body, the aft bluff boat-tail body being configured to augment flow separation of the exhaust flow.
9. The engine assembly of claim 8 , wherein the centerbody assembly includes an extendable centerbody cone.
10. The engine assembly of claim 1 , wherein the vanes of the swirl vane pack are selectively positionable at a first position and a second position.
11. The engine assembly of claim 10 , wherein the vanes are further selectively positionable to at least one position between the first and second positions.
12. The engine assembly of claim 10 , wherein the first position is an orientation of 0° so as not to swirl the exhaust flow when the afterburner apparatus is not being employed.
13. The engine assembly of claim 10 , wherein the second position is a non-zero orientation of the vanes that causes the exhaust flow to swirl.
14. The engine assembly of claim 10 , wherein the vanes have a flat profile.
15. The engine assembly of claim 1 , wherein the swirl generator further comprises at least one igniter, the igniter being coupled to one of the centerbody assembly, the inlet housing and the combustor, the igniter being operable for generating an ignition kernel that ignites the fuel/oxidizer mixture in the central recirculation zone.
16. The engine assembly of claim 15 , wherein the igniter is housed in the centerbody assembly.
17. The engine assembly of claim 16 , further comprising a second igniter coupled to the combustor at a location downstream of the dump step.
18. The engine assembly of claim 1 , wherein the inlet of the combustor includes a quarl expansion.
19. The engine assembly of claim 1 , wherein an inlet ramp is formed onto the inlet housing adjacent the dump step.
20. The engine assembly of claim 19 , wherein a plurality of circumferentially spaced apart injection sites are formed into the inlet ramp, the injection sites comprising at least a portion of the fuel injectors.
21. The engine assembly of claim 1 , wherein the vanes are configured to provide the swirl vane pack with a swirl number that is less than about 2.0.
22. The engine assembly of claim 1 , wherein the combustor is an expanding combustor.
23. An apparatus for providing propulsive power comprising:
a gas turbine engine producing an exhaust flow; and
an afterburner apparatus having a combustor, a swirl generator and a variable area nozzle, the swirl generator being associated with an aft end of the gas turbine engine, the swirl generator including a flow affecting means and a fueling means, the flow affecting means including a plurality of vanes, a centerbody having an aft end that terminates rearwardly of a root of the vanes and a dump step, the flow affecting means being operable for converting the exhaust flow into a three dimensional flowfield that includes a substantial tangential velocity component, the flow affecting means being further operable for effecting both a toroidal outer recirculation zone, which is anchored by the dump step, and a central recirculation zone that is disposed inwardly of the outer recirculation zone and anchored by the aft end of the centerbody, the fueling means being operable for fueling the outer and central recirculation zones and a core flow, the combustor being associated with an aft end of the swirl generator, the variable area nozzle being associated with an aft end of the combustor;
wherein heat and combustion byproducts produced during combustion are carried upstream by the outer and central recirculation zones where the heat and combustion byproducts are employed to continuously ignite a combustible fuel/oxidizer mixture in a shear layer adjacent each of the outer and central recirculation zones; and
wherein combustion by-products from the core flow are expelled through the variable area nozzle to produce thrust.