Wet Active Chevron Nozzle for Controllable Jet Noise Reduction

NASA’s Langley Research Center researchers have developed a novel noise reduction system for jet engines. Aircraft jet engine noise is a major issue for airports, the communities near airports, and, of course, for the jet engine designers. Even with the use of recent high-bypass-ratio jet engine designs, noise continues to be a major concern. The present innovation represents a significant advancement to the concept of using mechanically fixed chevrons on the trailing edge of jet engine nozzles to reduce noise. While the effect of chevrons on noise reduction is well known, commercial implementation has been limited. Unfortunately, the turbulence created with the chevrons, while useful for reducing noise upon takeoff, serves to reduce efficiency during cruising. The present innovation is a simple noise reduction system with effects similar to that of chevrons, yet it is active and controllable to maximize noise reduction while maintaining efficiency.