Mechanical Engineering Commons^™

A Theoretical Study On Integration And Optimization Of Gas Turbine Problems With Solar Energy System, Ahmad M. Abubaker

Theses and Dissertations--Mechanical Engineering

Gas Turbine (GT) power plants suffer from sensitivity to ambient-air temperatures, high fuel consumption, and a high amount of waste heat dumped into the ambient. Various solutions were proposed to solve these drawbacks, which could simultaneously solve at most two problems, usually at the expense of the third. For instance, inlet-air cooling can reduce ambient-air temperatures but will result in increased fuel consumption. However, in this work, a novel cascaded system was integrated into a combined cycle, capable of simultaneously solving all the aforementioned GT drawbacks. Parabolic trough collectors were used to preheat the air at the combustion chamber inlet …

Modeling Thin Layers In Material Response Solvers, Christen Setters

Theses and Dissertations--Mechanical Engineering

Thermal Protection Systems (TPS) are a necessary component for atmospheric entry. Most TPS contain thin layers of various materials such as ceramic coatings, pore sealers and bonding agents. When modeling TPS, these thin layers are often neglected due to the difference in scale between the TPS (centimeters) and the thin layers (micrometers). In this study, a volume-averaging flux-conservation method is implemented in the governing equations of a finite volume material response code. The model proposes the addition of a volume and area fraction coefficient which utilizes a weighted-averaging between the amount of thin layer and heat shield material in a …

Electromagnetic Formation Control Using Frequency Multiplexing, Zahra Abbasi

Theses and Dissertations--Mechanical Engineering

This dissertation addresses control of relative positions and orientations of formation flying satellites using magnetic interactions. Electromagnetic formation flight (EMFF) is implemented, in which each satellite is equipped with a set of electromagnetic coils to generate an electromagnetic field. Traditional EMFF technique applies DC magnetic fields which lead to a nonlinear and highly coupled formation dynamics that allow for only position or orientation control of the satellites. We present a new frequency multiplexing method, which is a technique that uses multi-frequency sinusoidal controls, to approximately decouple the formation dynamics and to provide enough controls for both position and orientation control. …

Redesigning Products To Optimize Sustainable Performance In Multi-Generational Closed-Loop Production For Advancing The Circular Economy, Buddhika Minendra Hapuwatte

Theses and Dissertations--Mechanical Engineering

Sustainable manufacturing and the circular economy concepts promote efficient and effective resource use to minimize the adverse economic, environmental, and social impacts of alarmingly increasing consumption rates. Product design is the key to implement these transformations in manufacturing. However, the currently available sustainable and circular design methods are not comprehensive and inadequate—especially for multi-generational products. Therefore, designing sustainable products optimized for circular and closed-loop production systems is a challenging task. The 6Rs concept introduced ‘Redesign’ to modify a product’s engineering specifications and allow sustainable utilization of the end-of-use resources from previous generations, thus closing the production loop. Therefore, the objective …

Waste Heat Recovery Of Industrial Regenerative Thermal Oxidizer (Rto), A Case Study, James Trimpe Jr.

Theses and Dissertations--Mechanical Engineering

Industrial processes that utilize and release hazardous compounds into the atmosphere are required to break down those compounds before exhausting them from their facilities. An industry-recognized method to break down those hazardous compounds is through thermal oxidation. Thermal oxidation is a process where the compounds are exposed to their auto-ignition temperature in an oxygen-rich environment and combust. The output of thermal oxidation is carbon dioxide, water vapor, and heat. Thermal oxidizers are equipment that performs the thermal oxidation process. The heat output from thermal oxidizers is wasted if directly exhausted into the atmosphere. Regenerative thermal oxidizers (RTOs) use the waste …

Cell And Biofilm Adhesion Strength Quantified By The Laser Spallation Technique Yields A Novel Biocompatibility Metric, The Adhesion Index, James Boyd

Theses and Dissertations--Mechanical Engineering

Implant associated infections are one of the leading causes of hospital acquired infections in the United States. Medical orthopedic implant devices are designed to improve adhesion of relevant cells within our body. In the case of orthopedic implants, osteoblast cells will adhere and allow for proper integration with the body’s bones. However, virulent bacteria will also adhere onto medical implants and proliferate into biofilms. Bacterial biofilms become extremely difficult to eradicate clinically as antibiotics are not as effective, resulting in severe infections or loss of implant. The aim of this research is to quantify the adhesion strength differential between relevant …

Localization Of Stationary Source Of Floor Vibration Using The Steered Response Power Method, Mohammad Royvaran

Theses and Dissertations--Civil Engineering

If the generated vibration in a building exceeds the acceptable limit design for a floor system, it is necessary to identify the source of vibration, a process known as localization. The objective of this study is the localization of stationary vibration sources, and the approach used is the steered response power (SRP) method. This method has already been shown to work well for wireless and acoustical applications to locate transmitter and sound sources, respectively. To the writer’s knowledge, this study is the first application of the SRP method to locate vibration sources using floor vibration measurements. However, because waves behave …

Additive Manufacturing In Personalized Medicine: Patient-Customized Solid Dose Medicines, And Patient-Customized Wound Care Device, Amir Najarzadeh

Theses and Dissertations--Mechanical Engineering

Personalized Medicine - from a one-size fits all to a tailored approach is the future in pharmaceutical therapeutics and medical applications. The aim of this study is demonstrate additive manufacturing in two personalized medicine applications: 1. Patient- customized solid dose medicines, and 2. Patient-customized wound care device. The aim of the first application is to develop an inexpensive and accurate method to design and fabricate patient-customized tablets. Particularly this paper focuses on fabricating and dose controlling of patient-customized extended release prednisolone-poly(vinyle alcohole) PVA. Dry-Blending, Wet Granulation, Extrusion, Spherionization, Hot melt extrusion (HME) was adopted to produce drug loaded prednisolone-PVA filaments …

Toward Intelligent Welding By Building Its Digital Twin, Qiyue Wang

Theses and Dissertations--Electrical and Computer Engineering

To meet the increasing requirements for production on individualization, efficiency and quality, traditional manufacturing processes are evolving to smart manufacturing with the support from the information technology advancements including cyber-physical systems (CPS), Internet of Things (IoT), big industrial data, and artificial intelligence (AI). The pre-requirement for integrating with these advanced information technologies is to digitalize manufacturing processes such that they can be analyzed, controlled, and interacted with other digitalized components. Digital twin is developed as a general framework to do that by building the digital replicas for the physical entities. This work takes welding manufacturing as the case study to …

Measurements Of Wind Turbine Wake Evolution And Trajectory During Morning Boundary Layer Transition And Under Wake Steering Conditions Via Unmanned Aerial Vehicles, Stewart Nelson

Theses and Dissertations--Mechanical Engineering

In July of 2019, a flight campaign was conducted using semi-autonomous Unmanned Aerial Vehicles (UAVs) at the Port Alma Kruger Energy wind farm in Ontario, Canada, to study various aspects of wind turbine wake evolution. Horizontal transects across the wakes were measured using modified fixed-wing aircraft fitted with a five-hole probe to measure the wind velocity vector. Reference boundary layer conditions were measured by an octocopter with an assortment of mounted sensors flying vertical profiles upstream of the turbines. Three experiments were conducted during the campaign, which consisted of a study on wake behavior during the morning boundary layer transition, …

Kinetics Of Elementary Reactions In Graphene Oxidation And Kinetics Of Oh* In Hydrogen Flames, Siamak Mahmoudi

Theses and Dissertations--Mechanical Engineering

Due to diverse applications of graphene, a kinetic mechanism describing rates of elementary reactions is extremely useful. To achieve that goal the elementary reactions need to be detected and their rates need to be determined. In this work the objectives are to use first-principle tools to find those reactions and analyze their paths in the context of graphene oxidation. Density functional theory (DFT) calculations provide the best approximation to the Schr\"{o}dinger equation, which is not feasible to solve analytically for large molecules like graphene. We have performed these calculations to find stable configurations (geometry optimization) and minimum energy paths between …

Evaluation Of Radiative Conductivity Inside A Porous Media With The Effect Of Participating Medium Based On Microscale Imaging, Mingping Zheng

Theses and Dissertations--Mechanical Engineering

Space vehicles will experience high loads of heat while entering the planetary atmosphere. At such high temperature, radiation becomes the dominant mode of heat transfer. Since the atmospheric entry environment is nearly impossible to duplicate in a laboratory environment, a numerical model to evaluate thermal performance of the thermal protection system was established. The model simulates the radiative heat transfer process in highly porous media, and the process also takes into account the influence of the participating media. An iterative approach and periodic boundary conditions are used to solve The unbalanced heat flux problem. CT scanned microscale Fiberform and artificial …

Prediction Of Noise Emissions Using Panel Contribution Analysis Supplemented With Scale Modeling, Gong Cheng

Theses and Dissertations--Mechanical Engineering

Panel contribution analysis (PCA) can be used to predict machinery noise emissions, component contributions, and to assess the impact of sound reduction treatments. PCA is a measurement approach that is advantageous for complex machinery that is not easily modeled using conventional numerical analysis approaches. In this research, PCA is combined with scale modeling in order to speed up the necessary measurement work. Moreover, the method can be applied to much larger machinery and noise emissions can be assessed prior to locating and installing the equipment. This eliminates the necessity to use voluminous anechoic chambers.

The machinery is first discretized into …

Viscoelasticity Of Ptfe-Based Face Seals, Bo Tan

Theses and Dissertations--Mechanical Engineering

PTFE-based materials are widely used in areas of tribology, particularly in seal and bearing applications because of their outstanding self-lubricating properties. Often in dynamic seal applications there is a need for ultra-low mechanical friction loss between the sealing surfaces. Due to its extremely low friction coefficient, there is interest in employing Polytetrafluoroethylene (PTFE) materials in such applications. One challenging aspect of employing PTFE is that these materials are viscoelastic and plastic. This dissertation concentrates on the modeling of viscoelastic material response when used as mechanical face seals with a focus on PTFE-based materials. First, the viscoelastic characteristics are measured through …

Balancing Trade-Offs In One-Stage Production With Processing Time Uncertainty, Jingjing You

Theses and Dissertations--Mechanical Engineering

Stochastic production scheduling faces three challenges, first the inconsistencies among key performance indicators (KPIs), second the trade-offs between the expected return and the risk for a portfolio of KPIs, and third the uncertainty in processing times. Based on two inconsistent KPIs of total completion time (TCT) and variance of completion times (VCT), we propose our trade-off balancing (ToB) heuristic for one-stage production scheduling. Through comprehensive case studies, we show that our ToB heuristic with preference =0.0:0.1:1.0 efficiently and effectively addresses the three challenges. Moreover, our trade-off balancing scheme can be generalized to balance a number of …

Tailoring Texture, Microstructure, And Shape Memory Behavior Of Niti Alloys Fabricated By L-Pbf-Am, Sayed Ehsan Saghaian N.E.

Theses and Dissertations--Mechanical Engineering

Laser Powder Bed Fusion (L-PBF) is one of the most promising Additive Manufacturing (AM) methods to fabricate near net-shape metallic materials for a wide range of applications such as patient-specific medical devices, functionally graded materials, and complex structures. NiTi shape memory alloys (SMAs) are of great interest due to a combination of unique features, such as superelasticity, shape memory effect, high ductility, work output, corrosion resistance, and biocompatibility that could be employed in many applications in automotive, aerospace, and biomedical industries. Due to the difficulties with traditional machining and forming of NiTi components, the ability to fabricate complex parts, tailor …

Use Of Microscale Hydrophobic Surface Features For Integration Of 3d Cell Culture Into Multi-Functional Microfluidic Devices, Soroosh Torabi

Theses and Dissertations--Mechanical Engineering

3D cell culture and microfluidics both represent powerful tools for replicating critical components of the cell microenvironment; however, challenges involved in integration of the two and compatibility with standard tissue culture protocols still represent a steep barrier to widespread adoption. Here we demonstrate the use of engineered surface roughness in the form of microfluidic channels to integrate 3D cell-laden hydrogels and microfluidic fluid delivery. When a liquid hydrogel precursor solution is pipetted onto a surface containing open microfluidic channels, the solid/liquid/air interface becomes pinned at sharp edges such that the hydrogel forms the “fourth wall” of the channels upon solidification. …

Multiscale Finite Element Modeling Of Active Contraction In Striated Muscle, Charles Kurtis Mann

Theses and Dissertations--Mechanical Engineering

Greater than one in three American adults have at least one type of cardiovascular disease, a major cause of morbidity. Computational cardiac mechanics has become an important part of the research effort to understand the heart’s response to mechanical stimuli and as an extension, disease progression and potential therapies. To this end, the present work aims to extend these efforts by implementing a cell level contractile model in which active stress generation in muscle tissue is driven by half-sarcomere mechanics. This is accomplished by enhancing the MyoSim model of actin and myosin in order to produce a multiscale model. This …

Study Of Stress-Based Fiber Reorientation Law In A Finite Element Model Of Cardiac Tissue, Alexus Lori Rockward

Theses and Dissertations--Mechanical Engineering

Myofiber organization in the heart plays an important role in achieving and maintaining physiological cardiac function. In many cardiac disease states, myofibers and particularly cardiomyocytes are disorganized in chaotic patterns, a phenotype known broadly as myocardial disarray. In familial hypertrophic cardiomyopathy (HCM), this disorganization in the form of myocyte disarray is thought to contribute to impaired cardiac function and the development of arrhythmia during disease progression. However, the mechanisms regarding fiber reorientation in the heart are yet still unclear, and few adaptative laws have been created to explore these mechanisms. A stretch-based law was developed with the aim of achieving …

Experimental Investigation Of Image Distortion In A Mach 6 Hypersonic Flow, Ricky W. Green Ii

Theses and Dissertations--Mechanical Engineering

The image distortion that is inherently present when imaging through a flow field at hypersonic speeds was investigated. The original problem involves observation of the outside world from the inside an aircraft moving at hypersonic speeds. For this work, a Mach 6 hypersonic wind tunnel at Wright Patterson Air Force Base (WPAFB) was used and optical patterns were imaged with and without flow field characteristics. Two test campaigns were scheduled to conduct experiments that would provide answers to the proposed problem of the effect on observable aberrations through flow fields.

During the first test campaign, October 2017, optical patterns were …

Effective Modulus Of Cracked Bodies: A Finite Element Analysis, Alan Thomas Varughese

Theses and Dissertations--Mechanical Engineering

This thesis considers how cracks in an elastic body can alter the body’s elastic properties. In the present study the elastic property of note is the elastic or young’s modulus. It is desired to investigate to what extent the number and orientation of cracks can cause a reduction in the elastic modulus. Because of the complex nature of the elastic fields resulting from multiple cracks interacting together in a finite geometry an analytical solution is not possible or considered. Rather the Finite Element Method is used to determine the elastic response to a body with many cracks. This provides a …

Structural Optimization Of Space Transit Vehicle Concept, Hercules, James Philip Rogers

Theses and Dissertations--Mechanical Engineering

STRUCTURAL OPTIMIZATION OF SPACE TRANSIT VEHICLE CONCEPT, HERCULES:

A COMPARATIVE STUDY OF STRUCTURAL OPTIONS

Hercules is a vehicle concept developed by NASA Langley's Vehicle Analysis Branch to satisfy the need for sustainable transit between Earth, the moon, and Mars. Hercules features unprecedented abort capabilities and mission flexibility to aid in NASA's Mars campaign. By utilizing modern software to perform structural analysis and optimization for a large selection of stiffened panel concepts, beam concepts, and materials trends in the structural optimization emerge. These trends will be invaluable for the design of future spacecraft needed to fulfill similar roles.

The structural optimization …