NASA STTR 2001-II Solicitation

SMALL BUSINESS CONCERN (SBC):		RESEARCH INSTITUTION (RI):
NAME:	Techsburg, Inc.	NAME:	Virginia Polytechnic Institute
ADDRESS:	2901 Prosperity Road	ADDRESS:	460 Turner Street, Suite 306
CITY:	Blacksburg	CITY:	Blacksburg
STATE/ZIP:	VA   24060 -3636	STATE/ZIP:	VA   24061 -0249
PHONE:	(540 ) 961 -4401	PHONE:	(540 ) 231 -5283

PRINCIPAL INVESTIGATOR/ PROJECT MANAGER:	Sarah Stitzel  Techsburg, Inc.

TECHNICAL ABSTRACT (LIMIT 200 WORDS)
Techsburg, Inc. and the Vibrations and Acoustics Laboratory at Virginia Tech (VAL) are proposing an innovative flow control scheme for fan rotors designed to simultaneously increase fan loading and efficiency while reducing fan radiated noise. The technology uses optimized blowing to prevent flow separation and significantly reduce the downstream wake size. A Phase I STTR proved the feasibility of using suction surface blowing jets to produce a sound power reduction on the order of 7dB and a reduction in losses of 60%. This research will combine an optimized flow control design with alternating blowing concepts. Using alternating blowing with an acoustic liner to attenuate the broadband noise will allow us to maximize the noise reduction and minimize the required mass flow.
The amount of work produced by a single compression stage is limited by the amount of diffusion that can occur without large-scale flow separation. Viscous losses within the separated region not only result in an efficiency penalty but also create a large wake behind each of the rotor blades that interact with the downstream exit guide vanes and stators. Left untreated, fan exhaust noise from this interaction is the most dominant perceived noise at takeoff and landing. By using flow control to eliminate separation and the rotor wake, both efficiency gains and noise reduction can be achieved.

POTENTIAL COMMERCIAL APPLICATION(S) (LIMIT 200 WORDS)
In reaction to the growing community noise problems that exist near many airports, FAR 36 Stage 3 noise requirements recently implemented will require that older low bypass ratio engines be retro fitted with hushkits or replaced with high bypass ratio engines. Beyond Stage 3 noise requirements, more stringent Stage 4 requirements will follow with an anticipated additional required reduction of 5-10 dB over Stage 3 levels. For high bypass ratio engines currently in use, fan noise dominates the total noise on approach and takeoff. Future ultra high bypass ratio turbofan engines will have an even greater fan tonal noise component at lower frequencies. The shorter inlet ducts relative to the size of the fan and the lower BPFs expected for these engines will make traditional passive liner technology less effective for attenuating the fan tones. Because of these difficulties, the proposed flow control system will be very attractive to industry looking for solutions to meet the increasingly strict noise regulations. If successful, the proposed technology will not only provide solutions for excessive fan noise but will also improve engine performance and reduce weight. Each of these benefits alone would make improved flow control methods a viable technology for industry.