Variable cam exhaust nozzle
View Patent ↗An exhaust nozzle includes an exhaust duct with an outlet and a row of radial apertures upstream therefrom. A radial frame surrounds the duct upstream from the apertures. A row of flaps are hinged to the frame to selectively cover and uncover the apertures for controlling exhaust flow discharged therethrough. An arcuate unison bar surrounds the duct adjacent to the frame and includes circumferentially spaced apart cam followers engaging corresponding cams affixed to the flaps. An actuator is joined to the bar for selective rotation thereof between opposite first and second directions to pivot open and closed the flaps atop the apertures.
1. A gas turbine engine exhaust nozzle comprising:
an exhaust duct having an outlet at an aft end thereof for discharging exhaust flow, and including a row of radial apertures spaced upstream from said outlet;
a radial frame extending circumferentially around said duct and spaced forward from said apertures;
a plurality of flaps hinged at upstream ends thereof to said frame to selectively cover and uncover said apertures for controlling exhaust flow discharge therethrough, and each flap including a cam extending radially outwardly therefrom for radial and axial movement therewith as said flap pivots;
an arcuate unison bar mounted circumferentially around said duct adjacent to said frame, and including a plurality of cam followers spaced circumferentially apart in radial engagement with corresponding ones of said cams affixed to said flaps; and
an actuator joined to said bar for selectively rotating said bar in a first direction to pivot open said flaps, and in an opposite second direction to pivot closed said flaps to cover said apertures.
2. A nozzle according to claim 1 wherein each of said cams comprises a ramp extending circumferentially along said flap, and varies in radial height from low to high, with low cam height permitting said flaps to pivot open radially outwardly, and high cam height pivoting closed said flaps radially inwardly.
3. A nozzle according to claim 2 wherein said unison bar is mounted to said duct by a plurality of guide rollers spaced circumferentially apart.
4. A nozzle according to claim 3 wherein said ramp twists between said low and high cam heights to maintain said ramp parallel with said cam follower as said flaps pivot between open and closed positions.
5. A nozzle according to claim 4 wherein each of said cams is arcuate in section between said flap and ramp to minimize differential axial movement between said ramp and corresponding cam follower.
6. A nozzle according to claim 3 wherein said cams include an up-step at the base of said ramp at said low cam height, and a down-step at the top of said ramp at said high cam height.
7. A nozzle according to claim 3 wherein said cam follower is mounted in said unison bar circumferentially between a pair of said guide rollers.
8. A nozzle according to claim 7 further comprising a plurality of longitudinal frames extending aft from said radial frame on opposite circumferential sides of corresponding ones of said flaps, and said guide rollers are mounted to said longitudinal frames.
9. A nozzle according to claim 8 wherein said unison bar includes a plurality of circumferential slots extending axially therethrough receiving corresponding ones of said guide rollers to permit circumferential rotation of said unison bar with radial retention.
10. A nozzle according to claim 9 wherein said unison bar includes a U-shaped cross section having two legs, and said guide rollers and said cam follower extend axially across said legs.
11. A nozzle according to claim 3 wherein said actuator is joined to a proximal end of said bar and is substantially parallel therewith for rotation thereof.
12. A nozzle according to claim 3 wherein said actuator includes an output rod joined in parallel with said unison bar, and is configured to extend said rod to rotate said bar in said first direction, and to retract said rod to rotate said bar in said second direction.
13. A nozzle according to claim 3 further comprising a plurality of springs mounted between respective ones of said flaps and radial frame to pull said flaps radially outwardly.
14. A nozzle according to claim 3 further comprising an outer duct surrounding said exhaust duct to form a bypass channel extending aft from said apertures and terminating at an auxiliary outlet.
15. A gas turbine engine exhaust nozzle comprising:
an exhaust duct having an outlet at an aft end thereof for discharging exhaust flow, and including a row of radial apertures spaced upstream from said outlet;
a radial frame extending circumferentially around said duct and spaced forward from said apertures;
a plurality of flaps each pivotally joined to said radial frame by a pair of hinges to selectively cover and uncover said apertures for controlling exhaust flow discharge therethrough, and each flap including a cam extending radially outwardly therefrom for radial and axial movement therewith as said flap pivots;
an arcuate unison bar mounted circumferentially around said duct adjacent to said frame, and including a plurality of cam rollers spaced circumferentially apart in radial engagement with corresponding ones of said cams affixed to said flaps; and
an actuator joined to said bar for selectively rotating said bar in a first direction to pivot open said flaps, and in an opposite second direction to pivot closed said flaps to cover said apertures.
16. A nozzle according to claim 15 wherein said actuator includes an output rod joined in parallel with said unison bar, and is configured to extend said rod to rotate said bar in said first direction, and to retract said rod to rotate said bar in said second direction.
17. A nozzle according to claim 16 wherein:
said unison bar is mounted to said duct by a plurality of guide rollers spaced circumferentially apart; and
said unison bar includes a U-shaped cross section having two legs, and said guide rollers and said cam rollers extend axially across said legs.
18. A nozzle according to claim 17 wherein each of said cams comprises a ramp extending circumferentially along said flap, and varies in radial height from low to high, with low cam height permitting said flaps to pivot open radially outwardly, and high cam height pivoting closed said flaps radially inwardly.
19. A nozzle according to claim 18 wherein said cams include an up-step at the base of said ramp at said low cam height, and a down-step at the top of said ramp at said high cam height.
20. A nozzle according to claim 19 further comprising a plurality of longitudinal frames extending aft from said radial frame on opposite circumferential sides of corresponding ones of said flaps, and said guide rollers are mounted to said longitudinal frames.
21. A nozzle according to claim 20 wherein said unison bar includes a plurality of circumferential slots extending axially therethrough receiving corresponding ones of said guide rollers to permit circumferential rotation of said unison bar with radial retention.
22. A nozzle according to claim 21 wherein said ramp twists between said low and high cam heights to maintain said ramp parallel with said cam roller as said flaps pivot between open and closed positions.
23. A nozzle according to claim 22 wherein each of said cams is arcuate in section between said flap and ramp to minimize differential axial movement between said ramp and corresponding cam roller.
24. A nozzle according to claim 23 further comprising a plurality of springs mounted between respective ones of said flaps and radial frame to pull said flaps radially outwardly.