A novel non-embedded, adjustable, and flexible shape memory alloy actuator for variable-area exhaust nozzle actuation

The actuator is a fundamental component for a variable-area exhaust nozzle. Conventional actuators for variable-area exhaust nozzles are hydraulic actuators and electric motors. However, they are heavy, large, and structurally complex. Shape memory alloys (SMAs) are light, small, structurally simple, and have unique advantages not found in conventional actuators. However, SMA actuators occupy a large space in the radial direction and cannot be fixed to surfaces with different radii of curvature. Moreover, once designed, the actuating displacement of the actuator cannot be adjusted. To solve this problem, this study develops a novel non-embedded, adjustable, and flexible SMA actuator for variable-area exhaust nozzle actuation. An analytical model is presented to predict mechanical performance. Subsequently, experiments of this flexible SMA actuator are conducted to study the mechanical performance. A proof-of-concept, variable-area exhaust nozzle of the aeroengine is designed, fabricated, and tested to obtain the properties of the exhaust nozzle that are actuated by the flexible SMA actuator. In the experiments, the movement trajectory of the exhaust nozzle is captured using an image recognition technique, and the area changes of the exhaust nozzle are calculated. The results show that the actuator is flexible and can be bent at any angle from -90° to +90°. The actuating displacement of the flexible SMA actuator can be adjusted by increasing or decreasing the number of hinged units. In addition, the area change of the exhaust nozzle is 64.4%, exceeding the largest area change of 40% in previous studies on SMA-actuated exhaust nozzles.