High-Power-Density High-Efficiency Carbon Nanotube Thermo-Acoustic (TA) Projectors
Abstract
High-Power-Density High-Efficiency Carbon Nanotube Thermo-Acoustic (TA) ProjectorsProposing team: Shashank Priya, (Virginia Tech);"" Ali Aliev (University of Texas at Dallas); JohnBlottman, Nathanael Mayo (NUWCDIVNPT)Executive Summary: There is a need for low-fr""equency, broad-bandwidth, efficient and compactsonar projectors that can be embedded in the hull of an unmanned sea vehicle (USV) o""r in theouter coating of a surface combatant or submarine as a conformal array. In past few years,researchers from Virginia Tech ("VT) and the University of Texas at Dallas (UTD) together withthe NUWCDIVNPT have provided the demonstration and basic fundamental foundation forthermoacoustic (TA) sound generation in air and underwater. This program builds upon theproposing team~s progress and" aims at answering the fundamental physics, materials science, andmechanical design questions that will allow transition of TA proj"ectors.We have developed an extensive experimental data base for open and closed systems for differentthermodynamic regimes. A new measurement system has been developed at VT forcharacterization of acoustic performance of TA device over wide range of frequency" under varyingpower and loading conditions. Using this measurement system, vibrational characterization of TAdevice in both air an"d water medium was conducted and a relationship between the generatedacoustic sound pressure and vibration modes has been establish"ed. Further, we have also developedunderwater experimental setup for quantifying the acoustic performance under varying drivecondi"tions and using data from this system initiated the development of thermoacoustic and vibroacousticfinite element model. The unique" feature of TA transducer is synchronization of variousphysical effects (vibration dynamics, thermal transport, and molecular dynam"ics) for achievinghigh acoustic pressure. A sinusoidal voltage input injects heat into the encapsulated argon mediumthrough Carbon Nanotube Tube (CNT) sheet (which has no thermal mass). This sinusoidal heatingof nearby medium by CNT sheet generates the thermoacoustic pressure wave which drives the endplates resulting in sound pressure wave generation in surrounding fluid domain. Since the" inputpower is converted into acoustic pressure through different intermediate steps, we propose todevelop a multilayer model in o"rder to include all the physical effects. This model captures thesteps leading to conversion of electrical energy into acoustical energy through the following steps:(i) an electrical input with wide range of frequency drives the CNT sheet resulting in pressurew"ithin the closed system, (ii) internal pressure acts as the driving force for vibrating theencapsulated TA projector, and (iii) vib"rating plate generates acoustic pressure wave in outer fluidmedium. This comprehensive vibro-thermo-acoustic model will provide the fundamentalfoundation needed for parametric understanding of the TA performance in terms of power densityand efficiency. Model va"lidation through systematic experimentation will be next task in theprogram. In conjunction, we will initiate the development of mo""lecular dynamics (MD) theory tounderstand the thermal interaction between CNT and Argon. In second and third year of theprogram, t"he focus will be in incorporating higher molecular density gases and fluids with phasetransitions in the low temperature regime to further improve the efficiency of system. Experimentalprototype TA transducers will be built and tested at VT. The third year focus in the program willbe on conducting testing at NUWC on the packaged thermoacoustic sound transduction at highapplied power densities in low frequency region. Based upon the test results both vibro-thermoacousticmodels and MD simulations will be refined to predict the performance with higherprecision. New device structure based upon the improved models will be fabricated and providedto N"UWC for validation.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 05, 2017
- Source ID
- N000141712520
Entities
People
- Shashank Priya
Organizations
- Office of Naval Research
- United States Navy
- Virginia Tech