NASA SBIR 00-1 SOLICITATION

FORM 9B - PROJECT SUMMARY


PROPOSAL NUMBER 00-1 02.02-8547 (Chron: 001454 )
PROJECT TITLE
Reduction of Aft Fan Radiation Using Herschel-Quincke Resonators



TECHNICAL ABSTRACT (LIMIT 200 WORDS)
Technology in Blacksburg and the Vibration and Acoustics Laboratories at Virginia Tech propose using hybrid Herschel-Quincke (HQ) resonators as a method to control aft fan noise radiated from turbofan engines. The noise control mechanism of the HQ tube system is as follows: as noise propagates through a duct past the entrance of a HQ resonator, some of the acoustic energy enters the HQ resonator while the remaining acoustic energy propagates down the duct. The sound waves in the resonator recombine with the duct acoustic waves at the tube exit. The fact that the waves in the HQ resonator travel a distance different than those in the duct results in a phase shift between the resonator and duct waves. Noise attenuation occurs at frequencies for which the recombining HQ resonator and duct waves are out of phase. Classical HQ resonators are passive devices with no moving parts whose noise attenuation characteristics are functions of the resonatorís length and cross-sectional area. For fan noise control applications the geometry of the HQ resonators are optimized to attenuate frequency at the blade passing frequency. Hybrid HQ resonators could be developed with variable geometry and used in conjunction with adaptive control to optimize their effectiveness over a wide range of engine operating conditions.



POTENTIAL COMMERCIAL APPLICATIONS
The technology proposed here has potential for commercialization among engine makers for both future engines and retrofits to existing engines. As regulations continue to become stricter, an increasing number of engines will be forced out of service prematurely if they are not capable of meeting the new restrictions. Consequently, a huge market exists for retrofit technology that will allow these engines to meet future regulations. The consensus among the industry sponsors is that HQ resonator technology could be an attractive augmentation of traditional absorptive linings because of its simplicity compared to active control alternatives. Furthermore, HQ resonators will have minimal effect on engine performance as compared to existing hush kits.



NAME AND ADDRESS OF PRINCIPAL INVESTIGATOR (Name, Organization Name, Mail Address, City/State/Zip)
Jonathan Fleming
Technology in Blacksburg, Inc
1861 Pratt Drive; Suite 2040
Blacksburg , VA   24060 - 6371



NAME AND ADDRESS OF OFFEROR (Firm Name, Mail Address, City/State/Zip)
Technology in Blacksburg, Inc
1861 Pratt Drive; Suite 2040
Blacksburg , VA   24060 - 6371