Design, production and testing of a titanium exhaust duct for noise and weight reduction

Abstract

AbstractHelicopter exhausts are usually basic components not yet developed to achieve the best noise reduction performance. This needs to change to continue complying with ever more restrictive noise regulations. A more efficient acoustic design could be reached using a complex configuration with assembly of multiple walls and 3D optimized geometry. As the exhausts nozzle are usually built out of Ni based alloys, the weight of such a component would increase. Such an increase could have a negative effect on the payload of the aircraft. Due to high temperatures and pressures of gas stream, Cp Titanium is limited for this application but heat resistant titanium alloys such as Beta21S and Ti 6–2‐4–2 would be a good substitution material as it provides significant weight reduction and capacity to sustain further power increase of the Helicopter engines. An European Project named “HORTIA” was funded to demonstrate the feasibility of using Heat and Oxidation Resistant Titanium Alloys for exhaust ducts in a noise and weight reduction objective. Studies were conducted on these materials to evaluate their mechanical performances and resistance against corrosion at high temperature for a service application. A thermo‐mechanical simulation of stress and temperature fields validated the definition design of a new component in an acoustically efficient configuration. An analysis of forming and welding parameters led to the industrial manufacturing of a complete exhaust with techniques like Super‐Plastic Forming and Laser Beam Welding. Finally the nozzle was successfully tested on en engine test bed for endurance and acoustic performance.