NASA SBIR 2004 Solicitation

SMALL BUSINESS CONCERN (Name, E-mail, Mail Address, City/State/Zip, Phone)
Technology in Blacksburg, Inc.
2901 Prosperity Rd.
Blacksburg, VA 24060-6644
(540)961-4401

PRINCIPAL INVESTIGATOR/PROJECT MANAGER (Name, E-mail, Mail Address, City/State/Zip, Phone)
Jason M Anderson
janderson@techsburg.com
2901 Prosperity Rd.
Blacksburg, VA 24060-6644
(540)961-4401

TECHNICAL ABSTRACT (LIMIT 200 WORDS)
Techsburg is teaming with the Vibration and Acoustics Laboratory of Virginia Tech to propose a non-linear analytical tool for designing Herschel-Quincke (HQ) waveguide arrays for the purpose of attenuating upstream-propagating shock waves in a transonic turbofan engine inlet. Techsburg will be receiving endorsement and support for this research from the Goodrich Company who owns the HQ waveguide array concept. Thus far linear acoustic modeling has been used to design HQ waveguide arrays that have experimentally proven to be successful in attenuating far-field sound radiation from subsonic ducted fans. However, the large transonic turbofan engines used in most civil aviation aircraft today produce large amplitude bow shocks upstream of the fan rotor that nonlinearly scatter energy from the dominant BPF circumferential mode near the fan rotor to primarily lower engine order circumferential modes at the duct entrance, which produces the "buzz-saw" far-field acoustic signature. The non-linear design tool developed by Techsburg/Virginia Tech in Phase I will be used to design an optimal HQ waveguide array in Phase II that will be placed near the fan with the intention of attenuating the BPF circumferential mode in order to reduce scattered energy into lower engine orders that cause far-field "buzz-saw" noise.

POTENTIAL NASA COMMERCIAL APPLICATIONS (LIMIT 100 WORDS)
The nonlinear model of the interaction between upstream propagating shock waves from a transonic turbofan aero engine and Herschel-Quincke waveguide arrays that Techsburg proposes for this Phase I research program can be utilized by NASA as an acoustic analysis and design tool for commercial transonic turbofan aero engines. This computer model could also be used for the analysis of other innovative passive and active noise control devices placed in intake ducts supersonic ducted fans. NASA could also couple the results of this in-duct nonlinear acoustic propagation model to far-field prediction codes such as the finite element based Eversman code.

POTENTIAL NON-NASA COMMERCIAL APPLICATIONS (LIMIT 100 WORDS)
Due to shock propagation in transonic turbofan engines, analysis and design of intake duct acoustic treatment requires nonlinear analysis. The nonlinear model of the interaction between upstream propagating shock waves from a transonic turbofan aero engine and Herschel-Quincke (HQ) waveguide arrays that Techsburg proposes for this Phase I research program serves this need for turbofan aero engine manufacturers. The HQ array technique is a particularly promising passive noise control technique owned by the Goodrich company, who like other engine manufactures currently desires a nonlinear analysis and design tool for innovative noise control technology.