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Variable Amplitude Passive Aircraft Vibration and Noise Reduction
Navy SBIR 2016.1 - Topic N161-021 NAVAIR - Ms. Donna Attick - [email protected] Opens: January 11, 2016 - Closes: February 17, 2016 N161-021 TITLE: Variable Amplitude Passive Aircraft Vibration and Noise Reduction TECHNOLOGY AREA(S): Air Platform, Human Systems ACQUISITION PROGRAM: PMA 231 E-2D Advanced Hawkeye Program Office OBJECTIVE: Develop an improved tuned vibration reduction solution for application to propeller excited high vibration levels in Navy turboprop aircraft. DESCRIPTION: Many current and emerging Navy turboprop aircraft experience high vibration and noise levels in crew spaces. This results in crew fatigue and reduced work effectiveness, and is particularly objectionable in the E-2D aircraft. The addition of aerial refueling capability for the E-2D will significantly lengthen mission duration, making this vibration and noise level issue even more detrimental to crew effectiveness. The key frequencies of the propellers are the first four blade pass frequencies. These frequencies are very stable over the entire flight envelope. Prior studies looked at tuned mass dampers (Ref 1) (TMDs) and tuned vibration absorbers (Ref 2) (TVAs), which have shown great promise to reduce tonal noise in such aircraft applications. Shock waves from turboprop blade tips impact the nearby fuselage structure and inject significant vibration energy into the aircraft structure at the blade pass frequency and harmonics. Navy aircraft structures have low vibration damping characteristics, as compared to commercial aircraft. There is also relatively little sound barrier and sound absorption treatment in military aircraft due to the weight and cost of such treatments. This vibration energy is able to pass through the fuselage structure and re-radiate into forward and aft crew spaces. TMDs have shown promise in addressing particular fuselage vibration modes in commercial aircraft. Commercial turboprop aircraft typically operate with variable rotation speed propellers. The drawback of TMDs are that the spring elements, typically made from viscoelastic materials, change stiffness and damping properties, and therefore tuning frequency, very significantly with temperature. Temperatures in the interior of commercial aircraft are typically held within a narrow range. This is somewhat less true in military applications. TVAs have shown promise in Navy turboprop aircraft vibration reduction applications. They typically have very stable, or invariant, frequency tuning, regardless of temperature and other atmospheric property variations. This is a most favorable property, since many Navy turboprop aircraft have very stable propeller turning rates over the flight envelope. A drawback of TVA use is that they tend to have a narrowly limited vibration amplitude range of application. Higher than design installed vibration levels can result in mass elements grounding out, or vibration behavior going non-linear, resulting in a loss of vibration reduction performance. A vibration reduction treatment is desired, addressing the above stated design drawback to the current TVA vibration reduction solution. The developed TVA treatment concept should be capable of being "tuned" to a given attachment location, with a particular attachment location impedance, and baseline vibration level at a specified frequency of interest. The desired solution should maintain tuning frequency, but modulate TVA mass response amplitude, so that it does not respond in a nonlinear fashion or "ground out" by having the damper mass contact the TVA bracket, or the aircraft structure, and either damage it or lose effectiveness, at the range of responses seen at a particular attachment location. Of primary interest is an innovative design approach to address this linearity and response amplitude limit issue, in such a way as to allow ready manufacture of one, or a small number of TVA models, to address a range of attachment location vibration properties. PHASE I: Demonstrate vibration reduction effectiveness of TVA concepts on laboratory structures that show the above described design properties. A successful demonstration will show the following features. A) Demonstrate a TVA concept(s) vibration reduction treatment that can be tuned to a stable, amplitude-independent response frequency (installed). B) Demonstrate that the TVA concept(s) shows good vibration reduction over a large response dynamic range. C) Demonstrate that the TVA concept will allow adjustment to change the allowable dynamic range. PHASE II: Develop the TVA concept demonstrated in Phase I into a prototype vibration reduction treatment that can reasonably, and safely be mounted to an aircraft structure. Note that specific installation location concerns and possible attached aircraft structure durability concerns would exist with or without the improved TVA design changes of this SBIR topic. It is intended that these concerns would be addressed during the production damping treatment design phase, and are outside the scope of this effort. The successful prototype will demonstrate the following features: A) Demonstrate pure tone vibration reduction effectiveness with simulated excitations on an aircraft structure provided by the Navy. B) Demonstrate pure tone vibration reduction effectiveness of prototypes on an aircraft structure under representative propeller induced loading. C) Demonstrate that the prototype is adjustable to the vibration dynamic range occurring at a number of attachment locations, with only minor "tuning" adjustment, but no parts changes. D) Show that the design features of the TVA prototype(s) are likely to show good performance* over the very wide range of temperature and environmental conditions encountered by Navy military aircraft. Good performance would be that attachment of the prototype damper results in vibration of the base structure during test excitation that is not higher than response of the base structure when a traditional TVA is attached, measured at the design frequency, and has regions or conditions where base structure vibration is reduced as compared to a traditional TVA of similar properties. E) What is reasonably safe? TVA prototypes must not require use of materials or design features that outgas harmful vapors, or that cannot be made durable enough for application to military aircraft in harsh operating conditions. Materials must be ones with stable properties over a 10 � 20 year life. PHASE III DUAL USE APPLICATIONS: Finalize the most promising TVA prototype into a manufacturable vibration reduction solution suitable to be applied to US Navy turboprop aircraft. This is the culmination of the Phase I and II efforts into a transitioned product which will be further validated in operational testing conducted in this Phase III effort. TVA vibration reduction solutions that are found to be effective for US Navy aircraft applications are very likely to have other viable applications to DoD and commercial aircraft, ground vehicles and machinery damping applications. Commercial aircraft, vehicles and machinery with stable vibration frequencies would similarly benefit by a treatment that can reduce local vibration levels. Vibration affects durability of fragile parts, such as circuitry, and customer perception of quality. REFERENCES: 1. Halvorsen, W. G. & Emborg, U. (1989). Interior Noise Control in the Saab 340 Aircraft. Society of Automotive Engineers, SAE Technical Paper Series Paper # 891080, General Aviation Aircraft Meeting and Exposition. Retrieved from http://papers.sae.org/8 2. Rustighi, E., Brennan, M. & Mace, B. (2005). A shape memory alloy adaptive tuned vibration absorber: design and implementation. Institute of Physics Publishing, Journal of Smart Materials and Structures, 14, 19-28. Retrieved from http://iopscience.iop.org/0964-1726/14/1/002/pdf/0964-1726_14_1_002.pdf 3. Sun, J.Q., Jolly, M.R. & Norris, M.A. (1995). Passive, Adaptive and Active Tuned Vibration Absorbers�A Survey. ASME. J. Mech. Des. 117(B), 234-242. doi:10.1115/1.2836462. Retrieved from http://mechanicaldesign.asmedigitalcollection.asme.org/article. 4. Vonflotow, A., Beard, A. & Bailey, D; (1994). Adaptive tuned vibration absorbers: Tuning laws, tracking agility, sizing, and physical implementations. Institute of Noise Control Engineers (INCE). NoiseCon94, Fort Lauderdale FL, 18, 437-454. Retrieved KEYWORDS: tuned vibration absorbers; tuned mass dampers; vibration reduction; passive dampers; Durability; Noise Control Technologies TPOC-1: 301-757-2306 TPOC-2: 301-995-1860 Questions may also be submitted through DoD SBIR/STTR SITIS website.
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