Adaptive Nozzle Technology for Mitigation of High Speed Jet Exhaust Noise

ABSTRACT: Noise alleviation for tactical jet aircraft is critical for community acceptance of military operations. While new fixed-geometry engine nozzles can mitigate noise, adaptive concepts can adjust to multiple flight conditions and reduce noise without compromising other performance metrics. Recent work by the proposing team has identified first-generation actuation devices that can enable such a"smart nozzle"capability using novel mechanical designs and rapidly maturing Shape Memory Alloy (SMA) materials. However, these designs must be tailored to meet the needs for high actuation force, constrained volume and weight, and harsh operating environment typical of takeoff conditions. This effort will build on prior work on subscale SMA-actuated systems to demonstrate key elements of an adaptive smart nozzle that will combine active flow mixing with area variation. Implementation will feature novel mechanisms and recently-developed SMA materials that provide the required force, displacement, and temperature capability. Phase I will entail analysis and design activities as well as benchtop and wind tunnel testing to demonstrate individual elements at subscale. This will lay the foundation lead for aeroacoustic testing of an integrated demonstrator in Phase II and for eventual use in Air Force systems to alleviate noise while maintaining or enhancing thrust performance and reducing fuel burn. BENEFIT: By providing highly innovative concepts for propulsion system components for tactical, the proposed effort will directly support critical Air Force goals including noise reduction, maximization of engine performance. This will in particular support the noise alleviation, fuel burn reduction, and performance enhancement goals the ongoing Air Force ADVENT project. The chief technical output of the effort will be demonstration of enabling technology for variable geometry devices to replace the promising but limited current generation of fixed-geometry nozzle designs. In addition, the integrated aero/thermo/elastic models of actuator performance and aerostructural behavior to be developed will assist the development of concurrent engineering tools for analysis and design of smart-materials-based propulsion flow control systems.