Shape memory alloy actuation system for variable area fan nozzle
A variable area fan nozzle comprising an array of hinged rigid petals and a petal actuation system in which the principle of actuation is realized by changes in shape (i.e., deformation) of the actuators rather than by movement of cooperating mechanical parts. Because these actuators have no rotating or sliding mechanical components, wear and associated maintenance are reduced. Each deformable actuator has a portion made of shape memory alloy that has been trained to change shape in a specific manner when heated to a temperature above a transition temperature. In addition, each shape memory alloy actuator is shaped to act as a fairing to reduce aerodynamic drag.
1. A variable area fan nozzle comprising:
a support member having a curved shape;
first and second petals disposed adjacent to each other at different circumferential positions along the curved shape of said support member with a gap separating respective edges of said first and second petals, said first and second petals being coupled to said support member in a manner that allows each of said first and second petals to deflect inwardly or outwardly, wherein a width of said gap varies as said first and second petal deflect inwardly or outwardly and
a first actuator comprising a first portion that spans said gap, and second and third portions connected to said first portion and respectively attached to marginal portions along said edges of said first and second petals, wherein said first portion is made of shape memory alloy having a characteristic that it undergoes a first shape change when its temperature is increased from below to above a transition temperature, wherein said first actuator is arranged to cause said first and second petals to deflect when said first portion of said first actuator undergoes said first shape change.
2. The variable area fan nozzle as recited in claim 1 , wherein said first and second petals deflect outward when said first portion of said first actuator undergoes said first shape change.
3. The variable area fan nozzle as recited in claim 1 , wherein said first and second petals deflect inward when said first portion of said first actuator undergoes said first shape change.
4. The variable area fan nozzle as recited in claim 1 , wherein said first portion of said first actuator has a V-shaped cross section.
5. The variable area fan nozzle as recited in claim 1 , further comprising a second actuator comprising a first portion that spans said gap, and second and third portions connected to said first portion of said second actuator and respectively attached to said first and second petals, wherein:
said first portion of said second actuator is made of shape memory alloy having the characteristic that it undergoes a second shape change when its temperature is increased from below to above a transition temperature;
said second actuator is arranged to deflect said first and second petals inward when said first portion of said second actuator undergoes said second shape change; and
said first actuator is arranged to deflect said first and second petals outward when said first portion of said first actuator undergoes said first shape change.
6. The variable area fan nozzle as recited in claim 1 , wherein said shape memory alloy has a further characteristic that it undergoes a second shape change when its temperature is decreased from above to below said transition temperature, wherein said first actuator will deflect said first and second petals outward when said first portion of said first actuator undergoes one of said first and second shape changes and inward when said first portion of said first actuator undergoes other of said first and second shape changes.
7. The variable area fan nozzle as recited in claim 1 , further comprising means for heating said first portion of said first actuator.
8. The variable area fan nozzle as recited in claim 1 , further comprising a heating coil thermally coupled to a surface of said first portion of said first actuator.
9. The variable area fan nozzle as recited in claim 1 , further comprising a seal made of elastomeric material, said seal comprising a portion that spans said gap between said first and second petals.
10. The variable area fan nozzle as recited in claim 1 , comprising left and right fan nozzle assemblies, wherein each of said left and right fan nozzle assemblies comprises a respective support member having a curved shape, respective first and second petals arranged as recited in claim 1 , and a respective first actuator which changes shape as recited in claim 1 .
11. A variable area fan nozzle comprising:
a support member having a curved shape;
a plurality of petals which are circumferentially distributed along said support member and have edges with gaps therebetween and movable inwardly or outwardly for varying an exit or throat area of the nozzle and varying a width of said gaps; and
a first plurality of petal deflection actuators attached to said petals, wherein each petal deflection actuator of said first plurality comprises shape memory alloy that changes shape when its temperature is increased from below to above a transition temperature, which shape changes in said first plurality of petal deflection actuators cause said petals to deflect,
wherein each petal of said plurality is connected to an adjacent petal of said plurality by a respective one of said petal deflection actuators that spans the gap therebetween.
12. The variable area fan nozzle as recited in claim 11 , further comprising a second plurality of petal deflection actuators attached to said petals, wherein each petal deflection actuator of said second plurality comprises shape memory alloy that changes shape when its temperature is increased from below to above a transition temperature, the shape changes in said first plurality of petal deflection actuators causing said petals to deflect outward and the shape changes of said second plurality of petal deflection actuators causing said petals to deflect inward.
13. The variable area fan nozzle as recited in claim 11 , wherein the shape memory alloy also changes shape when its temperature is decreased from above to below said transition temperature, and wherein said petals deflect outward when said petal deflection actuators of said first plurality change shape as a result of increasing temperature and said petals deflect inward when said petal deflection actuators of said first plurality change shape as a result of decreasing temperature.
14. The variable area fan nozzle as recited in claim 11 , wherein the shape memory alloy also changes shape when its temperature is decreased from above to below said transition temperature, and wherein said petals deflect inward when said petal deflection actuators of said first plurality change shape as a result of increasing temperature and said petals deflect outward when said petal deflection actuators of said first plurality change shape as a result of decreasing temperature.
15. An apparatus installed on an aircraft, comprising:
a sleeve or duct having a trailing lip area comprising a support member having a curved shape;
a plurality of petals which are circumferentially distributed along said support member with gaps therebetween and movable inwardly or outwardly for varying an exit or throat area of the nozzle and varying a width of said gaps;
a plurality of deformable elements distributed in said gaps, each deformable element comprising shape memory alloy that changes shape when heated to a temperature above a transition temperature;
a plurality of electric heaters thermally coupled to respective surfaces of said deformable elements; and
a computer system programmed to control the supply of electrical power to said electric heaters.
16. The apparatus as recited in claim 15 , further comprising one or more sensors for generating position feedback signals representing the current positions of said petals, wherein said computer system is programmed to provide electrical pulses to said electric heaters to change or maintain the shapes of said deformable elements, the number of pulses being dependent on the results of a comparison of target position data representing target positions of said petals and position feedback data derived from said position feedback signals.
17. The apparatus as recited in claim 15 , wherein one of said deformable elements comprises a first portion attached to a marginal portion along an edge of one of said petals and a second portion attached to a marginal portion along an edge of another petal adjacent to said one petal.