Engineering Commons^™

Performance Improvements For Next Generation Falling Particle Receiver Systems, Nathan R. Schroeder

Mechanical Engineering ETDs

Falling particle receiver (FPR) systems are a rapidly developing technology for concentrating solar power applications. Solid particles are used as both the heat transfer fluid and thermal energy storage media. Through the direct solar irradiation of the solid particles, flux and temperature limitations of tube-bundle receives can be overcome leading to higher operating temperatures and energy conversion efficiencies. Particle residence time, curtain opacity, and curtain stability affect the performance of FPR designs. As the particles fall through the receiver the curtain accelerates, increasing its transmissivity thus decreasing the amount of energy absorbed. Multistage release trough structures catch and release the …

Prefilling Mylar Capacitor Edge Margins To Improve Capacitor Reliability And Size, Chase Kayser

Mechanical Engineering ETDs

Typical high-voltage, wound film-foil capacitors have large edge margins filled with air to prevent breakdown between foil electrodes. This arrangement is inefficient for energy density and leaves a volume where particulates may settle in an uncontrolled atmosphere. The reliability and size of high-voltage, wound film-foil capacitors could be improved by adding a material with higher breakdown strength into the edge margins. This will not only improve reliability and size but also act as a barrier to prevent foreign object debris (FOD), volatile organic compounds (VOCs), and water from damaging the capacitor’s performance. This paper will discuss the process of determining …

Polarity Effects Of Aluminium Nitride Thin Films And Morphological Characterization Of Molybdenum Thin Films, Aseem Poudyal

Mechanical Engineering ETDs

AlN (Aluminium Nitride) is a piezoelectric material that is often used in numerous applications as a transducer. C-axis crystal orientation control of AlN is very important as it corresponds to a high piezoelectric coefficient. Crystal orientation of sputtered AlN is strongly affected by its deposition parameters such as sputtering pressure, target to substrate distance, growth temperature, gas pressure and frequency/duty cycle in the case of pulsed DC sputtering. Crystal orientation of AlN depends on the energy of the sputtered atom and the mobility of the adatoms on the surface of the substrate. Varying the deposition parameters can alter the kinetic …

Target Control Of Networked Systems, Isaac S. Klickstein

Mechanical Engineering ETDs

The control of complex networks is an emerging field yet it has already garnered interest from across the scientific disciplines, from robotics to sociology. It has quickly been noticed that many of the classical techniques from controls engineering, while applicable, are not as illuminating as they were for single systems of relatively small dimension. Instead, properties borrowed from graph theory provide equivalent but more practical conditions to guarantee controllability, reachability, observability, and other typical properties of interest to the controls engineer when dealing with large networked systems. This manuscript covers three topics investigated in detail by the author: (i) the …

Emissivity Measurements Of Painted And Aerosol Deposited Thermographic Phosphors (Yag:Dy And Mfg:Mn), Wendy Flores-Brito

Mechanical Engineering ETDs

Combustion is one of the most difficult processes to model. Luminous flames are characteristically sooty, which creates a problem when modeling and calculating the combustion and heat transfer of the process; both of which are highly dependent on temperature and emissivity. Soot particle emissivity as well as gas contributions affect the heat transfer calculation and must be accounted for.

Thermographic phosphors (TP) are ceramic based phosphorescent materials that have a temperature dependent emission that can be exploited to obtain surface and gas temperature measurements, as well as 2D temperature maps. Emissivity knowledge is not needed to obtain temperature and is …

Qualitative Investigation Of Gaseous Hydrodynamic Mixing Model Efficacy And Associated Sensitivity, Caleb White

Mechanical Engineering ETDs

A mixing model analyzes the mixing of helium (He) and sulfur hexafluoride (SF₆) according to two classical gaseous equations of state (EOS), namely, Amagat’s Law and Dalton’s Law, undergoing planar traveling shocks in three dimensions (3D). Numerical simulations utilize the Sandia National Laboratories (SNL) shock hydrodynamic code CTH and other codes including the SNL thermochemical equilibrium code TIGER and the uncertainty qualification (UQ) and sensitivity analysis code DAKOTA. Comparison with experimental results show that none of the equations of state are able to accurately predict the properties of the shocked mixture; similar discrepancies have been observed in previous …

The Effect Of Including Pressure Within Cracks On Failure Times Of Cylinders Subjected To Internal Air Blast Loading, Molly M. Bailey

Mechanical Engineering ETDs

The importance of internal crack pressure on the extent of crack propagation is studied using both numerical and experimental results. Experimental data were obtained from shock tube testing of internally pressurized quasi-brittle hollow cylinders loaded to failure. Half of the samples were tested with an inserted membrane that transferred the shocked fluid load but prevented the fluid from entering the developing cracks. In the other cases, the membrane was removed allowing the fluid to enter the crack and assist development of fracture. A novel approach to modeling this complex structural response involving dynamic failure and fluid structure interaction is presented, …