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Evaporating Cross Flow Spray Jets In Gas-Solid Circulating Fluidized Bed, Tong Hoon Lee

Dissertations

Three-phase flow of solid-gas suspension with liquid spray is found in many industrial applications, including fluidized catalytic cracking in petroleum refinery process, and wet scrubbing process. This dissertation study is aimed to understand the gas-solid-liquid three-phase flow structure, phase interactions and transport in a gas-solid circulating fluidized bed where an evaporating cross-flow liquid spray jet from a rectangular nozzle with a fan angle is injected. The investigation is based on both numerical and experimental approaches. The numerical study is for detailed field descriptions of the flow structure, phase interaction and distributions whereas the experimental study is for simulation validations. The …

Direct Numerical Simulations And Experimental Investigation Of Dielectrophoresis, Arun Thankamony John-Kadaksham

Dissertations

This dissertation deals with the numerical and experimental studies of the phenomenon of dielectrophoresis, i.e., the motion of neutral particles in nonuniform electric fields. Dielectrophoresis is the translatory motion of neutral particles suspended in a dielectric medium when they are subjected to an external nonuniform electric field. The translatory motion occurs because a force called the dielectrophoretic force, which depends on the spatial variation of the electric field, acts on the particles. As the generation of force involves no moving parts and the particles can be moved without touching them, dielectrophoresis can be used in many applications, including manipulation and …

Simulation Of Creep In Nickel Based Single Crystal Superalloys, Yunhong Pang

Dissertations

Nickel based single crystal Superalloys are finding wide spread use in high temperature gas turbines and other similar applications because of their superior high-temperature strength and creep properties as compared to the other materials. This is due to two factors: solid solution and precipitation strengthening of the gamma (γ) and gamma prime (γ') phases, and the elimination of grain boundaries. Creep of Nickel based single crystal Superalloys are caused by two primary mechanisms, dislocation creep and diffusion creep. Several factors that affect the creep life of Nickel based single crystal Superalloys are the specific microstructure, stress, temperature and rafting. Also, …

Gas Fluidization Of Nanoparticles, Qun Yu

Dissertations

The primary objective of this study is to perform a systematic investigation on the gas fluidization of various nanoparticle agglomerates. Firstly, the gas fluidization characteristics and regime classifications without any additional external force fields are identified using both experimental measurements and modeling. Secondly, the effect of introducing certain external force fields on nanoparticle fluidization is experimentally investigated. Two external force fields were applied: sound waves from a loud speaker (acoustic assistance) and in-bed magnets that were excited by an external oscillating magnetic field (magnetic assistance). Thirdly, exploratory experimental research on the use of nanoparticle agglomerates as a granular filtration media …

Experimental Technique For Studying High-Temperature Phase Equilibria In Reactive Molten Metal Based Systems, Alexandre Ermoline

Dissertations

The general objective of this work is to develop an experimental technique for studying the high-temperature phase compositions and phase equilibria in molten metal-based binary and ternary systems, such as Zr-O-N, B-N-O, Al-O, and others. A specific material system of Zr-O-N was selected for studying and testing this technique.

The information about the high-temperature phase equilibria in reactive metal-based systems is scarce and their studying is difficult because of chemical reactions occurring between samples and essentially any container materials, and causing contamination of the system.

Containerless microgravity experiments for studying equilibria in molten metal-gas systems were designed to be conducted …

Computational Studies Of Viscoelastic Multiphase Flows, Shriram B. Pillapakkam

Dissertations

A finite element code based on the level set method is developed for performing two and three dimensional direct numerical simulations (DNS) of viscoelastic two-phase flow problems. The Oldroyd-B constitutive equation is used to model the viscoelastic liquid. The code is used to study transient and steady state shapes of Newtonian and viscoelastic drops in simple shear and buoyancy driven flows. The roles of the governing dimensionless parameters: Capillary number (Ca), Deborah Number (De) and the polymer concentration parameter c, in determining deformation of drops and bubbles, are also analyzed.

The numerical code permits us to vary Ca, De and …

Investigation Of Static And Dynamic Enhancement Of Laminar Natural Convection Cooling Of Electronics, Laurie Ann Florio

Dissertations

With the proliferation of consumer electronics devices and the increasingly demanding thermal control requirements for such devices, more effective and efficient means of cooling electronics are needed. The feasibility of three alternative approaches to enhancing pure natural convection cooling of electronics is investigated in the current research. The three static or dynamic methods investigated are alternate cross-flow passages, the strategic placement of transversely oscillating plates near the heat sources and a combined method using both the cross-flow passages and the strategically placed oscillating plates. These cooling methods are intended to operate in the regime for which natural convection cooling is …

The Design Of Adjustable Spherical Mechanisms Using Plane-To-Sphere And Sphere-To-Plane Projections, Wen-Tzong Lee

Dissertations

The spherical mechanism is a particular type of spatial mechanism. Due to the orientation of its joint axes and the curvature of its links, the workspaces of spherical mechanisms (whether line segments, closed loops or area regions) are spherical in curvature. This characteristic of spherical mechanisms makes them quite effective and practical in motion path and function generation applications requiring spherical rigid body kinematics.

Although there are design methods available for spherical mechanisms, most of these methods do not consider the design of a single adjustable spherical mechanism. With an adjustable spherical mechanism, the user could for example, relocate the …

3-D Numerical Simulation Of Reactive Extrusion And Its Application To Polymerization Of Ε-Caprolactone In Co-Rotating Twin-Screw Extruders, Linjie Zhu

Dissertations

A 3-D numerical simulation model was proposed to predict the polymerization of ε-caprolactone in fully-filled conveying elements and kneading blocks of co-rotating twin-screw extruders, in which the kinetics equation for polymerization is coupled with continuity equation, momentum equation, and energy equation. With the 3-D model, parametric studies have been carried out to investigate the effects of screw configurations, screw diameter, operational conditions, values of heat from reaction, initiator concentration, and heat transfer conditions at barrel surface upon the polymerization progress. Two simulation models for the polymerization in the partially-filled channels were developed based on the conveying mechanisms of the reaction …

Effect Of Fullerene Containing Lubricants On Wear Resistance Of Machine Components In Boundary Lubrication, Andriy Titov

Dissertations

Fullerenes, a new form of carbon nanomaterials, possess unique physical and mechanical properties that make their use as additives to liquid lubricants potentially beneficial. The goal of this study was to investigate the effect of fullerene containing lubricants on wear resistance of steel-bronze couples operating under boundary lubrication conditions. A mathematical model of deformed asperity contact was built to calculate real contact area and real contact pressure. Computer controlled wear friction testing methodology and equipment were designed, developed and implemented for obtaining reliable and objective experimental data. In addition, optical and scanning electron microscopy and standard surface texture analysis were …

Migration Of An Intruder Particle In A Boundary Driven Shear Flow, Jian Liu

Dissertations

This study reports on three-dimensional, discrete element simulations of a single large spherical intruder in a Couette shear flow composed of uniform sized particles. The simulation results are useful in providing a numerical reproduction of the experiments for size segregation and mixing. This in turn has a major importance in many industries which are concerned with handling of particles and powders, such as pharmaceutical manufacturing, agriculture, chemical and mineral processing.

Discrete element simulations are carried out using the "soft sphere" model of Walton, et. al., which provides a method for obtaining the information at a macroscopic level from multi-body collisions …

Vibration-Induced Densification Of Granule Materials, Ninghua Zhang

Dissertations

Physical experiments as well as discrete element simulations of vibration are carried out. The use of different amplitudes and frequencies are applied in the experiments to facilitate the observation of densification trends with mono-disperse acrylic spheres and multi-disperse polyethylene pellets. For mono-disperse acrylic spheres, four densification trends are found at different vibration conditions, and attaining the "maximum density" is closely related to the combination of vibration frequency and amplitude, in agreement with experiments in the literature. For multi-disperse polyethylene pellets, there is a substantial increase in solids fraction due to the effects of particle shape and surface friction. Computer simulations …

Dielectrophoretic Manipulation Of Biological And Non-Biological Analytes In A Microfluidic Channel, Dawn J. Bennett

Dissertations

Micro-total-analytical systems (μTASs) for analyzing chemical/biological substances are now used across a wide variety of applications ranging from biological warfare agent detection to the healthcare industry. The first step in the operation of a μTAS consists of concentrating and separating the analytes of interest from the background matrix and positioning them into selected locations for subsequent analysis. The use of ac electric fields was demonstrated to have promising potential for a μTAS because the application of an ac field suppresses undesirable electrolytic effects in the liquid. The main purpose of this work is to study micro-scale phenomena in a flowing …

Theoretical And Experimental Studies Of The Field-Induced Phenomena In Flowing Suspensions, Nikolai Markarian

Dissertations

The present work describes results of experimental and theoretical studies of the behavior of dilute suspensions subject to high gradient AC electric fields. When a spatially non-uniform electric field is applied to a suspension, in which the particles and the suspending fluid have different dielectric permittivities andlor conductivities, the particles migrate towards the regions of high or low electric field strengths depending on the sign of their polarization. This phenomenon, referred to as dielectrophoresis, has found numerous applications for the control and manipulation of the particle motions.

Presented in Chapter 3 are the results of studying the field -induced motion …

Acoustical Characterization And Parameter Optimization Of Polymeric Noise Control Materials, Emile N. Homsi

Dissertations

The sound transmission loss (STL) characteristics of polymer-based materials are considered. Analytical models that predict, characterize and optimize the STL of polymeric materials, with respect to physical parameters that affect performance, are developed for single layer panel configuration and adapted for layered panel construction with homogenous core. An optimum set of material parameters is selected and translated into practical applications for validation.

Sound attenuating thermoplastic materials designed to be used as barrier systems in the automotive and consumer industries have certain acoustical characteristics that vary in function of the stiffness and density of the selected material. The validity and applicability …

Numerical And Experimental Investigation Of Dry Particle Coating, Ajit Mujumdar

Dissertations

Dry particle coating is an emerging field in the industries that deal with particulate products and powder processing. Compared to the widely reported experimental studies of the dry particle coating, the theoretical modeling of such processes is found to be less comprehensive. The work presented in this thesis is an attempt to fill this gap.

The first part of the dissertation aims at the numerical investigation of the hybridization system (Nara Machinery, Tokyo, Japan). The flow behavior of different materials processed in this device is analyzed using three-dimensional Discrete Element Method (DEM) as well as the computational fluid dynamics (CFD) …

Evaporating Crossflow Sprays In Gas-Solid Flows, Guangliang Liu

Dissertations

Injection of evaporating sprays into gas-solid flows is encountered in many engineering processes such as energy production industry and chemical industry. The phenomenon involves phase change, three-phase interactions, heat and mass transfer. All of these characteristics control the process efficiency, pollutant production and product quality. However, very limited studies are available on the evaporating spray jets in gas-solid flows, especially on the spray evaporation rate within a gas-solid medium. A combined study of experiments and theoretical analysis has been carried out here to investigate the fundamental mechanism of evaporating Crossflow spray jets in gas-solid flows.

In this study, in addition …

Destructive Disassembly Of Bolts And Screws Using Impact, Kyung Geun Pak

Dissertations

Disassembly, the process of separating parts or components at the end of their useful life is complex due to a variety of fastener shapes and variability in their damage during use. As a natural solution, mechanical impact has been suggested as a cost-effective method for destructive disassembly of joining elements.

The objective of this research is to improve the efficiency of impact disassembly process by studying the characteristics of elastic waves caused by impact. This research presents a new method for increasing the shear stress applied on the bolt head without increasing the energy input invested on launching striker. The …

Concurrent Evaporating Spray Jets In Dilute Gas-Solid Pipe Flows, Xiaohua Wang

Dissertations

Evaporating spray jets into gas-solids suspensions are encountered in many industrial applications. The rapid evaporation of spray jets has significant effects on the gas-solids mixing near the jet nozzle regions, including non-uniform solids concentration dilution, gas/solids temperature reduction, and gas/solids velocity acceleration. Furthermore, the jet structure is altered by the change of solids loading, jet mass flow rate and initial droplet size distribution. These interactions of gas, solids and evaporating droplets dominate the process efficiency and product quality. There is an urgent need for exploring fundamental mechanisms of the multi-phase interactions with heat and mass transfer as there are few …

Development Of Icejet-Based Surface Processing Technology, Dimitri V. Shishkin

Dissertations

The objective of the proposed work is to acquire knowledge needed for the development and deployment of manufacturing processes utilizing the enormous technological potential of water ice. Material removal by blasting with ice media such as particles, pellets and slugs was investigated. The ice media was accelerated by entrainment in a fluid stream (air, steam, liquid water, supercritical C0₂), impact of rotating blades, fluid expansion, etc. The ice-airjet has to replace sand blasting and the ice-waterjet has to replace the abrasive waterjet. Based on these results, technical approaches for surface processing and machining will be improved. A primary …

Numerical Simulation Of Mechanofusion System For Dry Particle Coating Process, Wenliang Chen

Dissertations

A numerical simulation of the Meclianofusion device for dry particle coating is carried out using Discrete Element Method (DEM) technique. In dry particle coating, tiny sub-micron guest particles are coated onto larger micron sized host particles by using mechanical forces, which the Mechanofusion device provides. It consists of a rotating cylindrical chamber that contains the powder mixture, a stationary inner piece (which has a cylindrical surface at the end), and a fixed scraper blade, which prevents powder from caking against the chamber wall. The simulation studies are performed on two scales: system scale to investigate the particle-particle and particle system …

Experimental And Numerical Study Of Flow Characteristics And Segregation In Flow Enhanced Systems, Gregory James

Dissertations

In the study of granular materials, two major topics of importance are powder flow enhancement mechanisms and the flow characterization. This dissertation is involved with both of these topics. With respect to the powder flow enhancement, this study involves investigation of two types of flow enhancement methods. The first flow enhancement method examined is a novel method called the Magnetically Assisted Powder Flow (MAPF) method. In the MAPF, small magnetic particles and powders are placed in a test hopper. A mesh is placed at the bottom of the hopper to hold the magnetic particles while the powder is discharged through …

Computation And Control Of Flow-Induced Noise Behind A Circular Cylinder Using An Acoustic Analogy Approach, Sirivit Taechajedcadarungsri

Dissertations

The computational aeroacoustics (CAA) research, which focuses on predicting acoustics by means of advanced numerical techniques, has recently gained a great deal of progress. In most applications, the prediction of both the sound source and its far-field propagation is necessary as required by regulations. Recently, powerful computers and reliable algorithms have allowed the prediction of far-field noise through the use of Computational Fluid Dynamics (CFD) data as near-field sound sources. One of the most useful analytical methods, used for the computation of noise, is Lighthill's acoustic analogy. The latter will be used in the present study.

Lighthill's acoustic analogy, combined …

Buckling Of Composite Conical Shells Under Combined Axial Compression, External Pressure, And Bending, Youngjin Chung

Dissertations

Conical shells are extensively used in space crafts, robots, shelters, domes, tanks, and in machinery or devices (e.g. as Belleville washers). Thus, the design of minimum weight, maximum strength, stiffened conical (and cylindrical) shells under combined loads has long been of interest to designers. The objective of this study is to improve the strength of conical shells and reduce the weight of the structure. Buckling of composite conical shells subjected to combined axial loading, external pressure, and bending is investigated using energy and finite element methods. The conical shells have single and multiple layers, different cone angle, length, and radius. …

Integration Of E-Business Strategy For Multi-Lifecycle Production Systems, Yanchun Luo

Dissertations

Internet use has grown exponentially on the last few years becoming a global communication and business resource. Internet-based business, or e-Business will truly affect every sector of the economy in ways that today we can only imagine. The manufacturing sector will be at the forefront of this change. This doctoral dissertation provides a scientific framework and a set of novel decision support tools for evaluating, modeling, and optimizing the overall performance of e-Business integrated multi-lifecycle production systems. The characteristics of this framework include environmental lifecycle study, environmental performance metrics, hyper-network model of integrated e-supply chain networks, fuzzy multi-objective optimization method, …

Parametric Study Of Heavy Metal Partitioning In A Pilot Scale Incinerator Burning Simulated Municipal Solid Waste, Sukrut S. Thipse

Dissertations

Incineration is a combustion process used to convert toxic waste to benign gases and residue in presence of excess air. The products of the incineration process are bottom ash, fly ash and the flue gas. Most of the metal-based phases formed in incineration are toxic and their emissions need to be strictly controlled. Therefore, behavior of metal species during incineration must be well understood. Such understanding is possible based on the experimental identification of the metal phases formed in the waste combustion and determination of their concentration in various incineration products.

A pilot-scale incinerator of 140,000 Btu/hr capacity was constructed, …

Force And Effort Analysis Of Unfastening Actions In Disassembly Processes, Manuela Sonnenberg

Dissertations

Fastening is the process of connecting one or more parts together with the aid of fastening elements. Unfastening, the reverse of fastening, is the process of separating components from each other by removing or detaching fastening elements. So far, the unfastening process is not well understood, and the analysis about it is not very extensive.

However, the need for disassembly is currently increasing. First, parts have to be taken apart for service and repair, and secondly, for the recycling process. Therefore, there is a need to consider unfastening during the design process in order to enable efficient disassemblies.

The purpose …

Numerical Stimulation Of Stress-Induced Crystallization Of Injection Molded Semicrystalline Thermoplastics, Jianxin Guo

Dissertations

Injection molded semicrystalline plastic products exhibit variable morphology along their thickness directions. The processing conditions have a significant effect on the crystallinity distribution in the final parts. However, because of the lack of sound theoretical models for stress-induced crystallization kinetics in thermoplastics, simulations of the injection molding process of semicrystalline plastics with the consideration of stress-induced crystallization have been scarce.

A stress-induced crystallization model for semicrystalline plastics is proposed based on the theory that stress induced orientation of polymer chains increase the melting temperature of the plastics, and hence, the supercooling which is the driving force for crystallization. By assuming …

Numerical Modeling And Optimization Of Waterjet Based Surface Decontamination, Konstantin Babets

Dissertations

The mission of this study is to investigate the high-pressure waterjet based surface decontamination. Our specific objective is to develop a practical procedure for selection of process conditions at given constraints and available knowledge. This investigation is expected to improve information processing in the course of material decontamination and assist in the implementation of the waterjet decontamination technology into practice. The development of a realistic procedure for processing of a chaotic and non-accurate information constitutes the main accomplishment of this study.

The research involved acquisition of representative information about removal of brittle, elastic and viscous deposits. As a result an …

Electro-Magnetic Control Of Cylinder Wake, Zhihua Chen

Dissertations

The objective of this dissertation is to develop open and closed-loop control algorithms for manipulating wake flows past a solid cylinder in an electrically low-conducting fluid (e.g. seawater). The intent is to avoid both vortex shedding and flow separation from the body. It is desired to reduce the mean drag significantly and prevent the lift from becoming non-zero at all times. This is achieved through the introduction of a Lorentz force in the azimuthal direction generated by an array of permanent magnets and electrodes located on the solid structure. The array of actuators offers the advantage of making the Lorentz …