Mechanical Engineering Commons^™

Performance Of Self-Excited Energy Harvesters With Tip Bodies Of Non-Circular Cross Section Shapes, Joan Manuel Gomez

Dissertations and Theses

An experimental study on the performance of self-excited energy harvesters with non-circular tip body shapes has been performed. The two tip body shapes analyzed correspond to a half cylinder and a square cross section. Experiments are carried out in the wind tunnel to record the voltage output of the harvesters at different free stream velocities. The presence of the aeroelastic galloping instability was detected by the behavior of the transversal tip displacement of the harvester as well as the coupling of the motion and shedding frequency from the bluff body. The effect of tip mass, free stream turbulence, tip body …

Chemical Structure And Dynamics In Laminar Flame Propagation, Mohsen Ayoobi

LSU Doctoral Dissertations

The objective of this dissertation is to investigate fundamental aspects of premixed flame structures as well as flame dynamics that arise due to conjugate heat transfer in narrow channels. Laminar premixed combustion simulations in narrow 2D channels show that conjugate heat transfer allows for combustion of mixtures at small scales that are not flammable at normal conditions. To investigate the impact of conjugate heat transfer, preheated 1D cases with premixed H2/Air fuel are simulated for a wide range of operating conditions based on inlet temperature and equivalence ratio. For post-processing, Chemical Explosive Mode Analysis (CEMA, an eigen-analysis technique) is used …

Physics And Applications Of A Pdms Based Centrifugal Microfluidic System, Ziliang Cai

LSU Doctoral Dissertations

The objective of this research work is to develop a centrifugal microfluidic system for general purposes based on microfabrication technologies including SU-8 photolithography, polydimethylsiloxane (PDMS) casting. The main contribution of this research is to integrate a flyball governor system into the polymer based centrifugal microfluidic platform. A series of function units are developed based on this unique mechanism. In the first part, three pinch valve systems were designed and tested. The first one is based on the magnetic force and the second one is on the basis of spring force and the last one is a membrane valve. All valving …

Correlation Of Csk2sb Photocathode Lifetime With Antimony Thickness, M. A. Mamun, C. Hernandez-Garcia, M. Poelker, A. A. Elmustafa

Mechanical & Aerospace Engineering Faculty Publications

CsK₂Sb photocathodes with quantum efficiency on the order of 10% at 532 nm, and lifetime greater than 90 days at low voltage, were successfully manufactured via co-deposition of alkali species emanating from an effusion source. Photocathodes were characterized as a function of antimony layer thickness and alkali consumption, inside a vacuum chamber that was initially baked, but frequently vented without re-baking. Photocathode lifetime measured at low voltage is correlated with the antimony layer thickness. Photocathodes manufactured with comparatively thick antimony layers exhibited the best lifetime. We speculate that the antimony layer serves as a reservoir, or sponge, for …

Fabrication And Characterization Of Miniaturized Components Based On Extruded Ceramic-Filled Polymer Blends, Khurshida Sharmin

LSU Doctoral Dissertations

The objective of this work is to develop an improved manufacturing process for microstructured ceramic components that is based on co-extrusion. Co-extrusion of structured feedrods holds promise for development of multi-layered, functionally graded and/or textured structures. However, it requires a polymer binder that is difficult to remove before structures can be sintered to full density. A two-step debinding is introduced to eliminate debinding defects that are commonly observed in thermal debinding (TD). Cracking is a major issue due to a lack of pore spaces for outgassing of pyrolysis products in traditional TD. In two-step debinding, a soluble binder is removed …

On The Role Of Surface Roughness In Elastohydrodynamic Lubrication Of Tribological Components, Mohammad Masjedi

LSU Doctoral Dissertations

The present dissertation investigates the effect of surface roughness in the elastohydrodynamic lubrication (EHL). Since many essential components of the machinery such as gears, rolling element bearings, cam-followers, and heavily loaded journal bearings operate under the mixed EHL condition, and given the fact that nearly all engineering surfaces are rough to some extent, there is a need for an extensive research which can realistically quantify the effect of the surface roughness in such applications. We thus seek to develop an applied engineering approach for the treatment of the mixed EHL for prediction of the performance of machinery. Both line-contact and …

Heat Transfer And Film Cooling On A Gas Turbine Blade And Shroud, Onieluan Tamunobere

LSU Doctoral Dissertations

At a fixed pressure ratio, the thermodynamic efficiency and net power output of a gas turbine engine increases with an increase in the turbine inlet temperature. Cooling is necessary because of the thermal limits of the engine materials. This research studies through experimentation, the heat transfer and cooling of critical gas turbine components including the shroud and blade tip. In the first phase, the shroud heat transfer behavior and the effectiveness of shroud cooling under the conditions of rotation is undertaken in a single stage turbine at a design rotation speed of 550 rpm, at off-design speeds and for varying …

Numerical Studies Of Liquid-Liquid Segmented Flows In Square Microchannels Using A Front-Tracking Algorithm, Eamonn Daire Walker

LSU Doctoral Dissertations

Liquid-liquid segmented flows in a square microchannel are investigated numerically using a hybrid front-tracking/front-capturing method. The code is found to be well-adapted to a large range of flow parameters, but droplet flows are limited by poor accuracy at Laplace number above 100 – 1000 and plug flows are limited by the code’s current inability to adequately model the flow in thin films at low capillary numbers. A Schwarz-Aitken acceleration technique is investigated as a means to reduce computation time, but is found not to be advantageous compared to the parallel multigrid formulation of the code. Numerical simulations are divided into …

On The Thermally Induced Failure Of Rolling Element Bearings, Jafar Takabi

LSU Doctoral Dissertations

This dissertation is devoted to the investigation of thermally induced seizure of rolling element bearings. A comprehensive thermal model of the rolling element bearings is developed which can predict the operating temperature of the bearing components in a wide range of operating conditions. The validity of this thermal model is verified by comparing the simulation results with a set of experiments. The results of simulations reveal that the rotational speed, oil viscosity and cooling rate of the housing have a significant influence on the operating temperature of the rolling bearings. To provide detailed information about all of the contact forces …

Challenges Towards Structural Integrity And Performance Improvement Of Welded Structures, Mohammad Washim Dewan

LSU Doctoral Dissertations

Welding is a fabrication process that joint materials, is extensively utilized in almost every field of metal constructions. Heterogeneity in mechanical properties, metallurgical and geometrical defects, post-weld residual stresses and distortion due to non-linear welding processes are prime concerns for performance reduction and failures of welded structures. Consequently, structural integrity analysis and performance improvement of weld joints are important issues that must be considered for structural safety and durability under loading. In this study, an extensive experimental program and analysis were undertaken on the challenges towards structural integrity analysis and performance improvement of different welded joints. Two widely used welding …

Heat Transfer Study Of Porous Media With A Temperature Jump Condition, Pravin Kumar

LSU Master's Theses

Conjugate heat transfer in a porous media is investigated with a temperature jump condition obtained from kinetic gas theory. The temperature jump appears alongside flow boundary condition when the pressure is low, and considered to be in non-continuum regime. This investigation focuses on both one-dimensional and two-dimensional porous media models. The length scale of the pores is 100 microns. The temperature is ambient, and the pressure is low enough to reach the slip-flow regime. The thermal behavior of porous media is investigated using a slot model with a gas trapped between two solid blocks. Aluminum oxide and air are considered …

Superconducting Magnetic Energy Storage Unit For Damping Enhancement Of A Wind Farm Generation System, Embaiya Salih, Stefan Lachowicz, Octavian Bass, Daryoush Habibi

Research outputs 2014 to 2021

A superconducting magnetic energy storage (SMES) system containsa high inducting coil and combines with power conversion system can act as a constant source of direct current. SMES unit connected to a power system is able to absorb and store both active and reactive power from this system and to inject these powers into the power system in the demand periods. These injected powers are controlled by changing both the duty cycle of the dc-dc chopper switches and its operation modes. This paper presents an efficient design based on an SMES unit controlled by the artificial neural network (ANN) to improve …

A Review Of Locomotion Systems For Capsule Endoscopy, Lejie Liu,, Shahrzad Towfighian, Amine Hila

Mechanical Engineering Faculty Scholarship

Wireless capsule endoscopy for gastrointestinal (GI) tract is a modern technology that has the potential to replace conventional endoscopy techniques. Capsule endoscopy is a pill-shaped device embedded with a camera, a coin battery, and a data transfer. Without a locomotion system, this capsule endoscopy can only passively travel inside the GI tract via natural peristalsis, thus causing several disadvantages such as inability to control and stop, and risk of capsule retention. Therefore, a locomotion system needs to be added to optimize the current capsule endoscopy. This review summarizes the state-of-the-art locomotion methods along with the desired locomotion features such as …

A Cylindrical Triboelectric Energy Harvester For Capsule Endoscopes, Lejie Liu, Shahrzad Towfighian, Zhanpeng Jin

Mechanical Engineering Faculty Scholarship

Capsule endoscopy is a new technology that has the potential to replace conventional endoscopy in the near future due to its non-invasive nature. A major limitation for their functionality is the limited battery life. We have investigated a triboelectric energyharvester inside a capsule endoscope that can generate power from natural contractions of gastrointestinal (GI) tract. The periodic contacts and separations of two triboelectric materials inside the capsule endoscope create an alternating current that can be used to charge the capsule endoscope battery, which is used for imaging the GI tract. This study presents an analytical closed form solution for the …

Buckling Instability Of Crown Sealing, J. O. Marston, Mohammad M. Mansoor, Tadd T. Truscott, S. T. Thoroddsen

Mechanical and Aerospace Engineering Faculty Publications

Despite the scholarly fascination with water entry of spheres for well over a century,¹ we present a new observation, namely, the crown-buckling instability. This instability is characterized by striations appearing near the top of the crown walls just prior to the surface seal, as shown in Fig. 1(a). The crown wall collapses inward due to the pressure differential across the wall created by the moving air in the wake of the sphere and surface tension within the crown. Since the rate of collapse is faster than that at which fluid drains out from the neck region, fluid collects into …

High Regression Rate Hybrid Rocket Fuel Grains With Helical Port Structures, Stephen A. Whitmore, Sean D. Walker, Daniel P. Merkley, Mansour Sobbi

Mechanical and Aerospace Engineering Faculty Publications

Results froma development campaign, where modern additive manufacturing methods are used to fabricate hybrid rocket fuel grains with embedded helical ports, are presented. The fuel grains were constructed from acrlyonitrile butadiene styrene using commercially available three-dimensional printer feedstockmaterial.Gaseous oxygen is used as the oxidizer for this test campaign.When compared to cylindrical fuel ports, significant increases in fuel regression rates were observed, and these increases in regression rate diminished with time as the helical fuel port burns to become progressivelymore cylindrical. Comparisons to the helical pipe flow skin friction correlation developed by Mishra and Gupta indicate that increased skin friction only …

Matryoshka Cavity, Randy Craig Hurd, T. Fanning, Zhao Pan, C. Maybey, Kyle G. Bodily, Kip Schafer Hacking, Nathan B. Spiers, Tadd T. Truscott

Mechanical and Aerospace Engineering Faculty Publications

When a water droplet impacts a free surface with sufficient velocity, the momentum transfer results in the formation of a hemispherical cavity expanding radially from the point of impact.¹ This cavity continues to expand until the kinetic energy is completely converted to potential energy (Fig. 1(a)).² Pumphrey and Elmore equated the potential energy of this subsurface cavity with the kinetic energy of the impacting droplet, concluding that the magnitude of the cavity radius is proportional to impact velocity and droplet diameter.³

Experimental Validation Data For Cfd Of Mixed Convection On A Vertical Flat Plate, Blake W. Lance, Jeff R. Harris, Barton L. Smith

Mechanical and Aerospace Engineering Faculty Publications

Model validation for Computational Fluid Dynamics(CFD), where experimental data and model outputs are com-pared, is a key tool for assessing model uncertainty. In this work, mixed convection is studied experimentally for the purpose of providing validation data for CFD models with a high level of completeness. Experiments are performed in a facility built specifically for validation with a vertical, flat,heated wall. Data were acquired for both buoyancy-aided and buoyancy-opposed flows. Measured boundary conditions include as-built geometry, inflow mean and fluctuating velocity profiles, and inflow and wall temperatures. Additionally, room air temperature, pressure, and relative humidity are measured to provide fluid …

The Study Of Frequency-Scan Photothermal Reflectance Technique For Thermal Diffusivity Measurement, Zilong Hua, Heng Ban, David H. Hurley

Mechanical and Aerospace Engineering Faculty Publications

A frequency scan photothermal reflectance technique to measure thermal diffusivity of bulk samples is studied in this manuscript. Similar to general photothermal reflectance methods, an intensity-modulated heating laser and a constant intensity probe laser are used to determine the surface temperature response under sinusoidal heating. The approach involves fixing the distance between the heating and probe laser spots, recording the phase lag of reflected probe laser intensity with respect to the heating laser frequency modulation, and extracting thermal diffusivity using the phase lag–(frequency)^1/2 relation. The experimental validation is performed on three samples (SiO₂, CaF₂, and …

Spacecraft Attitude Control Using Magnetic Actuators, Karthik Mysore Srinivasa

Dissertations, Master's Theses and Master's Reports - Open

This report presents a study on the problem of spacecraft attitude control using magnetic actuators. Several existing approaches are reviewed and one control strategy is implemented and simulated. A time-varying feedback control law achieving inertial pointing for magnetically actuated spacecraft is implemented. The report explains the modeling of the spacecraft rigid body dynamics, kinematics and attitude control in detail.

Besides the fact that control laws have been established for stabilization around local equilibrium, this report presents the results of a control law that yields a generic, global solution for attitude stabilization of a magnetically actuated spacecraft. The report also involves …

Optical Access Engine Setup And Validation, Jiongxun (Justin) Zhang

Dissertations, Master's Theses and Master's Reports - Open

The optical access engine integrated with the diagnostic and optical measurement techniques is a great platform for engine research because it provides clear visual access to the combustion chamber inside the engines. An optical access engine customized based on a 4-cylinder spark ignited direct injection (SIDI) production engine is located in the Advanced Power Systems Laboratories (APS LABS) at Michigan Technological University. This optical access engine inside the test cell has been set up for different engine research.

In this report, two SAE papers in engine research utilizing the optical access engine are reviewed to gain basic understanding of the …

Development And Validation Of A Radtherm Model To Predict Exhaust System Behavior For A Hybrid Xm1124 Hmmwv, Souman Haldar

Dissertations, Master's Theses and Master's Reports - Open

Accurately predicting component temperatures, and the influence various subsystems have on each other prior to hardware development and testing is an important aspect of the vehicle development process. In this report, a 1-D thermal model is used for predicting the behavior of the exhaust system and underbody area of prototype Hybrid Electric HMMWV XM1124. This prototype vehicle is designed to be capable of exporting up to 15 kW of electrical power to a micro-grid or similar operation. However, in this project instead of exporting power to a micro-grid, 6.5 kW of power was used to charge the batteries and increase …

Modelling And Control Of Combustion Phasing Of An Rcci Engine, Kaveh Khodadadi Sadabadi

Dissertations, Master's Theses and Master's Reports - Open

Reactivity controlled compression ignition (RCCI) is a novel combustion strategy introduced to achieve near-zero NOx and soot emissions while maintaining diesel-like efficiencies. Meanwhile, precise control of combustion phasing is a key in realization of high fuel conversion efficiency as well as meeting stringent emission standards. Model-based control of RCCI combustion phasing is a great tool for real-time control during transient operation of the engine, which requires a computationally efficient combustion model that encompasses factors such as, injection timings, fuel blend composition and reactivity. In this thesis, physics-based models are developed to predict the combustion metrics of an RCCI engine. A …

Structural Analysis Of Integration Of A Non-Cylindrical Cng Fuel Tank, Prathamesh Prashant Deshpande

Dissertations, Master's Theses and Master's Reports - Open

The purpose of this study is to computationally model and analyze the vehicle frame which is mounted with a non-conventional, non-cylindrical compressed natural gas (CNG) fuel tank. Integration of this tank in the vehicle underbody will resolve the issue of reduced storage space which is observed in a conventional CNG powered vehicle. This research will ultimately result in making CNG a good alternative to gasoline and reducing the increasing dependency on a single fuel. This tank will be developed in two phases: phase I design of the tank will be a standard rectangular outer box shape with Schwarz P-surface inner …

Mechanical Characterization Of Bamboo And Glass Fiber Biocomposite Laminates, Matthew Siniawski

Mechanical Engineering Faculty Works

Single-ply biocomposite laminates were fabricated with two different woven fabrics and a bio-based resin using a wet layup technique at room temperature. A highly elastic, stockinette weave bamboo fiber fabric and a thicker, inelastic plain weave bamboo fabric were both investigated. The elastic fabric was pre-strained at 25% intervals, ranging from 0-100% of its original length. Samples made with E-Glass and S-Glass, two common glass fiber reinforcements, were also fabricated using the bioresin as benchmarks. The ultimate strength and modulus of elasticity characteristics of the composites were determined using the ASTM D3039/ D3039M-08 standard test method for determining the tensile …

Thermographic Investigation Of Laser Metal Deposition, Sreekar Karnati

Masters Theses

"Laser metal deposition as an additive manufacturing technique has been proven to possess the capability for fabricating complex, intricate geometries and excellent material properties through material deposition. Accurate manufacture of such geometric features would require precise control over the material deposition process. The need of the hour are process monitoring and analyses mechanisms that are crucial in ascertaining the occurrence of the intended actions during deposition while also serving as effective learning tools. The current work involved developing and incorporating an Infra-Red (IR) camera as a process monitoring tool for laser metal deposition. Using the IR camera the thermal dynamics …

Laser Surface And Sub-Surface Repair During Metal Additive Manufacturing, Prudvi Teja Ravi

Masters Theses

"This study examines the use of laser surface treatment to repair surface and subsurface defects. Numerical analysis was performed on laser surface melting using Gaussian heat distribution equations to analyze the depth of the melt pool created by the phenomena. Concurrently, a process map was developed with a planned set of experiments by varying the ranges of laser power and travel speed to determine the dimensions of the melt pool across the gamut. The data generated from both the process studies and the numerical analysis was then used to determine the ideal operating ranges of the process parameters to repair …

Generation And Validation Of Optimal Topologies For Solid Freeform Fabrication, Purnajyoti Bhaumik

Masters Theses

"The study of fabricating topologically optimized parts is presented hereafter. The mapping of topology optimization results for Standard Tessellation Language (STL) writing would enable the solid freeform fabrication of lightweight mechanisms. Aerospace leaders such as NASA, Boeing, Airbus, European Aeronautic Defense And Space Company (EADS), and GE Aero invest in topology optimization research for the production of lightweight materials. Certain concepts such as microstructural homogenization, discretization, and mapping are reviewed and presented in the context of topology optimization. Future biomedical applications of solid freeform fabrication such as organ printing stand to save millions of lives through the robust development of …

Freeze-Form Extrusion Fabrication Of Boron Carbide, Aaron Scott Thornton

Masters Theses

"Boron carbide is a safe, alternative to beryllium as a material for aerospace structures since it is also light-weight and exhibits high strength. This paper discusses a study of the Freeze-form Extrusion Fabrication (FEF) process to fabricate parts from boron carbide. Process parameters and hardware were modified to fabricate boron carbide specimens free of printed defects. Four-point bending tests were performed to measure the flexural strength of fabricated specimens. Observations of the presence of voids caused by ice crystals in fabricated parts led to further development and characterization of the boron carbide paste used with the FEF process. Additives were …

Freeform Extrusion Fabrication Of Titanium Fiber Reinforced 13-93 Bioactive Glass Scaffolds, Albin Thomas

Masters Theses

"Although implants made with bioactive glass have shown promising results for bone repair, their application in repairing load-bearing long bones is limited due to their poor mechanical properties as compared to human bones. This thesis study is on freeform extrusion fabrication of silicate based 13-93 bioactive glass scaffolds reinforced with titanium fibers. A composite paste was prepared with 13-93 bioactive glass filled with titanium fibers (~16 µm in diameter and aspect ratio of ~250) having 0.1 to 0.4 vol. % of the bioactive glass scaffold. This paste was then filled into a syringe manually, and then extruded through a nozzle …