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Articles 2401 - 2430 of 3234
Full-Text Articles in Mechanical Engineering
Feasibility Study Of T700 Rotorcraft Engine Rotor Supported By Hybrid Air Foil Bearings, Mahesh Kumar Varrey
Feasibility Study Of T700 Rotorcraft Engine Rotor Supported By Hybrid Air Foil Bearings, Mahesh Kumar Varrey
Mechanical and Aerospace Engineering Theses - Archive
A potential solution towards light weighted and simple structured turbomachinery lies in elimination of oil-lubrication system. These promising benefits of oil-free turbomachinery have demanded extensive research in the field of small turbomachinery, leading to the development of different types of oil free bearings. Air foil bearings (AFBs) are one of the oil-free bearings with many advantages over others. AFBs have simple construction, greater service life and reduced maintenance. Their superior dynamic performance compared to traditional rigid surface bearings is an added advantage. Implementation of these foil bearings in the rotorcraft propulsion system decreases the total weight of the engine setup, …
Analysis Of Laminated Tubular Structure Under Torsion, Thana Chomtid
Analysis Of Laminated Tubular Structure Under Torsion, Thana Chomtid
Mechanical and Aerospace Engineering Theses - Archive
Laminated composite shells in particular are prominent in bearing various types of loads and are hence used in many engineering structures. The analysis of laminated composites is quite complicated since the material behavior is anisotropic, which gets further intensified in the analysis of complex structures like tubular structures. Finite element method is a useful method for evaluating and conducting the behavior of thin laminated tubular structure subjected to torsion. In this study, the behavior of shear stress versus angle along the laminated tubular structure cross section was conducted in varies radius ratio which are 1, 0.8, 0.6, 0.4, and 0.2 …
Static And Dynamic Calibration Of A Multi-Component Sidewall Force Balance For A Transonic Ludwieg Tube Wind Tunnel, Michael Gerard Werling
Static And Dynamic Calibration Of A Multi-Component Sidewall Force Balance For A Transonic Ludwieg Tube Wind Tunnel, Michael Gerard Werling
Mechanical and Aerospace Engineering Theses - Archive
Experimentation involving transonic flow requires replicating not only the Mach number but also the Reynolds number. Improper matching of the Reynolds number affects the interaction between the shocks and boundary layer on the surface of an airfoil, moving the position of the shock and altering the downstream flow field. Both Mach and Reynolds numbers have a large influence on the lift and drag characteristics of airfoils, amongst other aerodynamic effects, within the transonic regime of flight. A strain-based, multi-component, sidewall force balance was purchased in 1989 specifically for the transonic Ludwieg tunnel at the University of Texas-Arlington, but proper calibration …
Evaporative Cooling Performance Of A Brazed Microporous Coating On An Aluminum Surface, Ryan M. King
Evaporative Cooling Performance Of A Brazed Microporous Coating On An Aluminum Surface, Ryan M. King
Mechanical and Aerospace Engineering Theses - Archive
The effect of an aluminum microporous coating on evaporative cooling performance was studied using distilled water as the working fluid. The aluminum microporous coating was fabricated by brazing aluminum particles to an aluminum substrate. Microporous coating thicknesses of 175 µm ± 20 µm, 270 µm ± 20 µm, and 900 µm ± 90 µm, and average aluminum particle sizes of 27 µm, 70 µm and 114 µm were used in a parametric study to determine the optimum aluminum microporous coating. A hot water treatment maximized the wickability of the microporous coating. Wickability was measured by vertical dipping of the coating. …
Algebraic Solution To The Planar Rigid Body Impact Problem, Drew Morgan
Algebraic Solution To The Planar Rigid Body Impact Problem, Drew Morgan
Mechanical and Aerospace Engineering Theses - Archive
For systems of rigid bodies that undergo impacts, a series of closed-form equations are developed to solve for post-impact velocities which simulate a real-world (energy-consistent) interaction. The analysis is based in the impulse domain, and requires that the surface interaction be characterizable by Coulomb friction and an energetic coefficient of restitution. No iteration, optimization, or numerical methods are used.
Performance Optimization Of Multi-Core Processors Using Core Hopping - Thermal And Structural, Sunil Lingampalli
Performance Optimization Of Multi-Core Processors Using Core Hopping - Thermal And Structural, Sunil Lingampalli
Mechanical and Aerospace Engineering Theses - Archive
As the work load on the single core processor increases, it's processing speed increases resulting in increased power densities and die temperatures. The increase in die temperature results in decreased performance and reliability and increased leakage currents and cooling costs. In order to decrease the work load and the cooling cost on the single core processor, multi-core processors have been implemented. Multicore Processors also known as Chip Multi Processors (CMP's) are the processors which contain two or more independent cores on a chip. In CMPs, if one core reaches its critical temperature, the workload is transferred to the other. This …
Estimation Of Aircraft States And Wind Exposure In Aerial Refueling, Je Hyeon Lee
Estimation Of Aircraft States And Wind Exposure In Aerial Refueling, Je Hyeon Lee
Mechanical and Aerospace Engineering Dissertations - Archive
When a tanker and receiver aircraft fly in tight formation in an aerial refueling operation, they are exposed to various sources of wind with varying magnitude and direction. The tanker and the receiver aircraft experience prevailing wind and turbulence. The receiver aircraft is also subject to an additional wind field induced by the wake of the tanker.The receiver aircraft is required to fly in a precise trajectory relative to the tanker. Especially, the receiver aircraft should stay at a position with small tolerances for the fuel transfer operation while the tanker aircraft flies straight level and makes constant altitude turns. …
Fabrication Of Micropatterns On 3d Surfaces And Generation Of Linked Zno Nanowires, Hui Wang
Fabrication Of Micropatterns On 3d Surfaces And Generation Of Linked Zno Nanowires, Hui Wang
Mechanical and Aerospace Engineering Dissertations - Archive
Conventional lithographic approaches are good at fabricating structures on the top surfaces of substrates. They are not suited for 3D surface patterning due to the fact that vertical radiation exposure is employed to transfer patterns. In the meanwhile, patterns generated on 3D surfaces, such as the vertical sidewalls of silicon channels and the irregular surfaces of glass micropipettes may provide valuable applications in microfluidics, 3D circuits, bioengineering and so on. In this work, we developed new approaches to produce metal micropatterns on the vertical sidewalls of silicon channels as well as to fabricate two separated metal microlines on the tips …
Development Of An Experimental And Analytical Model Of An Active Cooling Method For High-Power Three-Dimensional Integrated Circuit (3d-Ic) Utilizing A Multidimensional Configured Thermoelectric Modules, Huy Phan
Mechanical and Aerospace Engineering Dissertations - Archive
An increase in demand for more functionality and capacity of microelectronic components within the same logistic footprint drives the growth of three-dimensional integrated circuit (3D-IC) packaging technologies in recent years. However, the reduction in size and an increase in transistors density also intensified the heat flux of stacked-dice, which introduces many thermal challenges at both the package and cooling levels. Traditional passive cooling system such as forced air convection cooling, phase change materials and passive or active heat sinks will become inadequate to cool future processors and cannot accommodate the demand of future sub-ambient cooling of 3D-ICs. Within the past …
Hybrid Dynamic Simulation For Performance Optimization Of Legged Mechanisms, Daniel Montrallo Flickinger
Hybrid Dynamic Simulation For Performance Optimization Of Legged Mechanisms, Daniel Montrallo Flickinger
Mechanical and Aerospace Engineering Dissertations - Archive
Agile locomotion is needed for mobile robots to efficiently navigate challenging terrain. The ability of an agile legged mobile robot to abruptly change trajectory allows it toquickly react to obstacles and successfully operate in environments usually more suited forlegged animals. The research presented herein aims to increase the agility and performanceof legged robots.Using hybrid dynamic simulation, novel methods are developed to model the inter-action of a legged robot with the ground. In considering robot agility, an accurate model ofthe events that occur while in contact is needed. Methods are developed to model groundinteraction where oblique angled impacts occur, and to …
Design And Modeling Techniques For Cooling Of Telecommunication Systems, Naveen Kannan
Design And Modeling Techniques For Cooling Of Telecommunication Systems, Naveen Kannan
Mechanical and Aerospace Engineering Theses - Archive
Conventional data centers are extremely large buildings that have complex power distribution and cooling systems. These traditional brick and mortar data centers employ relatively expensive cooling systems and are inefficient. It has in turn led to an increase in construction and operational costs. These inefficiencies of traditional data centers can be overcome by partitioning the server load into modular sections which can be deployed, powered and cooled depending on availability and requirement. Furthermore, improvements in efficiency and operational costs can be achieved by employing "free cooling" to cool the IT equipment. Free cooling involves the introduction of outside air through …
Design Optimization Of A Wind Turbine Blade, Bharath Koratagere Srinivasa Raju
Design Optimization Of A Wind Turbine Blade, Bharath Koratagere Srinivasa Raju
Mechanical and Aerospace Engineering Theses - Archive
This work focuses on designing a blade of 45 meters in length that produces a power of 1.6 MW. The design of the blade was done using the Blade Element Momentum theory and the Prandtl's tip loss factor was used. The aerodynamic loads and differential power at are tabulated and plotted.The finite element method for analysis of the blade is used. As the chord lengths vary decreasingly along the blade radii in order to use the simple beam theory the breath and height of the blade is considered as a function of the chord length, hence the analysis is done …
Filling Of Methane/Air Mixture In A Tube For Pulse Detonation Engines, Shravani Dwarakapally
Filling Of Methane/Air Mixture In A Tube For Pulse Detonation Engines, Shravani Dwarakapally
Mechanical and Aerospace Engineering Theses - Archive
In pulse detonation engines, filling is a time consuming process; reducing these times will help to increase the frequency. The filling of a detonation tube, 1 m long tube with an internal diameter of 101.6 mm, closed at one end and opened at the other, was studied using the unsteady flow solver methane and air nominally at STP· Three cases were examined: (i) a 25.4 mm diameter port at the center of the closed end, (ii) nine ports of 25.4 mm diameter, one at the center of the closed end and eight distributed in two diametrically opposite rows, equally, four …
Control Of Airship Motion In The Presence Of Wind, Jatuporn Nakpiam
Control Of Airship Motion In The Presence Of Wind, Jatuporn Nakpiam
Mechanical and Aerospace Engineering Theses - Archive
This research effort develops a guidance and control system for a small airship to fly through assigned waypoints in the three dimensional space with a desired speed in the presence of wind and wind gust. In the control system development and validation, a simulation environment based on the nonlinear 6-DOF model of an airship, including the effect of the wind, is used. The airship has five control variables, the main thrust, the main thrust angle, the tail thrust, elevator and rudder deflections. The effectiveness of the elevator and rudder degrades as the speed of the airship decreases. The controller design …
On The Advantages Of E100 Over Gasoline In Down-Sized, Turbo-Charged, Direct-Injected, Variable Valve Actuated, And Stoichiometric S.I. Engines, Alberto A. Boretti
On The Advantages Of E100 Over Gasoline In Down-Sized, Turbo-Charged, Direct-Injected, Variable Valve Actuated, And Stoichiometric S.I. Engines, Alberto A. Boretti
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Current flexi fuel gasoline and ethanol engines have efficiencies generally lower than dedicated gasoline engines. Considering ethanol has a few advantages with reference to gasoline, namely the higher-octane number and the larger heat of vaporization, the paper explores the potentials of dedicated pure ethanol engines using the most advanced techniques available for gasoline engines, specifically direct injection, turbo charging and variable valve actuation. Computations are performed with state-of-the-art, well validated, engine and vehicle performance simulations packages, generally accepted to produce accurate results targeting major trends in engine developments. the higher compression ratio and the higher boost permitted by ethanol allows …
Use Of Bio-Ethanol And Bio-Diesel The Key Solution For A More Sustainable Road Transport, Alberto Boretti
Use Of Bio-Ethanol And Bio-Diesel The Key Solution For A More Sustainable Road Transport, Alberto Boretti
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Life Cycle Analysis (LCA) of alternative transportation fuels clearly shows the advantages of reducing the use of nonrenewable fossil fuels vs. renewable biologic novel fuels to reduce the emissions of carbon dioxide. Being based on the natural recycle of carbon dioxide through the use of renewable energy sources, use of these renewable fuels does not imply depletion of natural resources and is therefore sustainable in the long term. Renewable fuels and advanced internal combustion engines and powertrains are the technologies that in addition to be the most likely to produce benefits in term of carbon balance and fossil fuel saving, …
Ductile Mode Material Removal Of Ceramics And Semiconductors, Deepak Ravindra
Ductile Mode Material Removal Of Ceramics And Semiconductors, Deepak Ravindra
Dissertations
Ceramics and semiconductors are hard, strong, inert and lightweight. They also have good optical properties, wide energy bandgap and high maximum current density. This combination of properties makes them ideal candidates for tribological, semiconductor, MEMS and optoelectronic applications respectively. Manufacturing these materials without causing surface and subsurface damage is extremely challenging due to their high hardness, brittle characteristics and poor machinability. However, ductile regime machining of these materials is possible due to the high-pressure phase transformation occurring in the material caused by the high compressive stresses induced by the single point diamond tool tip. In this study, to further augment …
Parametric Analysis Of A Detonation-Type Turbofan, Yashwanth M. Swamy
Parametric Analysis Of A Detonation-Type Turbofan, Yashwanth M. Swamy
Mechanical and Aerospace Engineering Theses - Archive
A new type of turbofan which detonates a fuel-air mixture was theoretically found to perform better than a conventional turbofan. A continuous detonation process is described and considered inside the core of the turbofan. The detonation-type turbofan needs certain modifications to detonate the fuel-air mixture at the core of the turbofan, namely, an annular detonation chamber to achieve continuous detonation. A parametric analysis of the new detonation-type turbofan was developed and used to calculate the performance parameters.
Study Of Turbulence-Chemistry Interaction In Hypersonic Turbulent Boundary Layers, Lian Duan, M. Pino Martín
Study Of Turbulence-Chemistry Interaction In Hypersonic Turbulent Boundary Layers, Lian Duan, M. Pino Martín
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Studies of the turbulence-chemistry interaction (TCI) are performed in hypersonic turbulent boundary layers using direct numerical simulation (DNS) flow fields under typical hypersonic conditions representative of blunt-body and slender-body hypersonic vehicles, with super catalytic and noncatalytic wall conditions in pure air. Nondimensional governing parameters, 'interaction' Damk̈ohler number and relative heat release, are proposed to measure the influence of TCI on flow composition and temperature. Both a priori and posteriori studies are performed to assess the effect of TCI on chemical production rates and mean and turbulence flow characteristics. In addition, an effective approach (called PDF-TS) to estimate the intensity of …
Use Of Bio Ethanol The Key Solution For A More Sustainable Road Transport, Alberto A. Boretti
Use Of Bio Ethanol The Key Solution For A More Sustainable Road Transport, Alberto A. Boretti
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Life Cycle Analysis (LCA) of alternative transportation fuels clearly shows the advantages of reducing the use of nonrenewable fossil fuels vs. renewable synthetic and biologic novel fuels to reduce the emissions of carbon dioxide. Being based on the natural or synthetic recycle of carbon dioxide through the use of renewable energy sources, use of these renewable fuels does not imply depletion of natural resources and is therefore sustainable in the long term. Renewable fuels and advanced internal combustion engines and powertrains are the technologies that in addition to be the most likely to produce benefits in term of carbon balance …
Alternative Crankshaft Mechanisms And Kinetic Energy Recovery Systems For Improved Fuel Economy Of Passenger Cars, Alberto A. Boretti, Joseph Scalzo, Houshang Masudi
Alternative Crankshaft Mechanisms And Kinetic Energy Recovery Systems For Improved Fuel Economy Of Passenger Cars, Alberto A. Boretti, Joseph Scalzo, Houshang Masudi
Mechanical and Aerospace Engineering Faculty Research & Creative Works
The paper presents a novel design of a variable compression ratio advanced spark ignition engine that also permits an expansion ratio that may differ from the compression ratio therefore generating an Atkinson cycle effect. the stroke ratio and the ratio of maximum to minimum in-cylinder volumes may change with load and speed to provide the best fuel conversion efficiency. the variable ratio of maximum to minimum in-cylinder volumes also improves the full load power output of the engine. Brake specific fuel consumption maps are computed for a gasoline engine 2 Liters, in-line four, turbocharged and direct injection showings significant fuel …
Numerical Study Of Drop Formation From Dripping To Jetting, Allouah Kadjo
Numerical Study Of Drop Formation From Dripping To Jetting, Allouah Kadjo
Mechanical and Aerospace Engineering Theses - Archive
The formation of liquid droplet from a capillary tube has been examined using numerical simulations. The dimensions of the capillary tube and the flow velocity have been varied to observe the regimes of drop formation. There are three main regimes of drop formation, which are the periodic dripping, the dripping faucet and the jetting regimes. The mechanism of drop formation changes from one regime to another and involves different parameters. A particular emphasis has been placed on the velocity limits between the different regimes and the critical role played by instabilities in the generation of satellite drops. The algorithm used …
Numerical Modeling Of A Parallel Plate Electrowetting-On-Dielectric (Ewod) Device, Kevin Tully
Numerical Modeling Of A Parallel Plate Electrowetting-On-Dielectric (Ewod) Device, Kevin Tully
Mechanical and Aerospace Engineering Theses - Archive
Numerical modeling and simulations have been performed in this study that focuses on modeling the fluid dynamics of an Electrowetting-on-Dielectric (EWOD) device. The case to be modeled in the present study is a droplet cutting problem where a droplet is sandwiched between two plates of Teflon and an electrical actuation will cause the droplet to cut or split into two smaller droplets. A finite difference method has been used to solve the Navier-Stokes equations, along with the continuity equation. An algorithm used for tracking the free surface is the Volume of Fluid (VOF) method. Along with using the VOF method …
Ultra-Abrupt Tapered Fiber Mach-Zehnder Interferometer Sensors, B. Li, J. Lan, W. Sumei, L. Zhou, Hai Xiao, Hai-Lung Tsai
Ultra-Abrupt Tapered Fiber Mach-Zehnder Interferometer Sensors, B. Li, J. Lan, W. Sumei, L. Zhou, Hai Xiao, Hai-Lung Tsai
Electrical and Computer Engineering Faculty Research & Creative Works
A fiber inline Mach-Zehnder interferometer (MZI) consisting of ultra-abrupt fiber tapers was fabricated through a new fusion-splicing method. By fusion-splicing, the taper diameter-length ratio is around 1:1, which is much greater than those (1:10) made by stretching. The proposed fabrication method is very low cost, 1/20-1/50 of those of LPFG pair MZI sensors. The fabricated MZIs are applied to measure refractive index, temperature and rotation angle changes. The temperature sensitivity of the MZI at a length of 30 mm is 0.061 nm/°C from 30-350 °C. The proposed MZI is also used to measure rotation angles ranging from 0° to 0.55°; …
Heat Transfer In Triangular Ducts With Axial Conduction,Containing Porous Medium, Abhishek Banerjee
Heat Transfer In Triangular Ducts With Axial Conduction,Containing Porous Medium, Abhishek Banerjee
Mechanical and Aerospace Engineering Theses - Archive
The objective of this study is to find a numerical solution for the velocity and temperature field in a duct of triangular cross-section area. A fully saturated porous medium is considered to be present in the duct. The study reports the contribution of axial conduction in heat transfer to flow passing through triangular porous passages. The terms in x-direction are retained in the energy equation due to the presence of axial conduction. Also, because of the geometrical asymmetry, non-orthogonal boundary conditions can exist and thus make the determination of heat transfer more difficult. The problem under consideration uses H2 boundary …
Nonlinear Finite Element Analysis Of Columns, Rajkiran Muppavarapu
Nonlinear Finite Element Analysis Of Columns, Rajkiran Muppavarapu
Mechanical and Aerospace Engineering Theses - Archive
In many engineering applications structural components are considered to be beams or columns subjected to a range of external loads such as dead weight, wind, temperature changes etc.In this work a mathematical model has been developed for a sports lighting tower considering it to be a cantilever beam with large deformation. The concept of non-linear P-Delta analysis is applied to the column. Using this model, a tower analysis tool was developed in MATLAB. Using this tool various design alternatives can be examined to evaluate their suitability to a particular task.A number of example problems from the available literature were solved …
Stable Reference Trajectory Modification For Handling Actuator Failure In Control Systems, Ifeolu Olalekan Ogunleye
Stable Reference Trajectory Modification For Handling Actuator Failure In Control Systems, Ifeolu Olalekan Ogunleye
Mechanical and Aerospace Engineering Theses - Archive
The issue of rapidly reconfiguring the reference trajectory under unanticipated actuator failures in order to regain lost performance or aircraft handling qualities is explored. The failures detected in real-time are compensated for by ensuring the input to the system reflects current system conditions. This thesis will also show that only the general structure of the failed system component is needed to achieve successful failure detection and reference trajectory reconfiguration. This approach allows the nominal control structure to remain unchanged in the presence of change flight and system conditions. Acceptable system performance is recovered by detecting the actuator failures in real-time. …
Experimental Flow Visualization For Corrugated Airfoils At Low Reynolds Number Including Development Of A Pitch And Plunge Fixture, Jeremy Ryan Sparks
Experimental Flow Visualization For Corrugated Airfoils At Low Reynolds Number Including Development Of A Pitch And Plunge Fixture, Jeremy Ryan Sparks
University of Kentucky Master's Theses
Micro Air Vehicles (MAV’s) have small size and extreme maneuverability which makes them ideal for surveillance. Propulsion mechanisms include propellers, rotors, and flapping airfoils. Flapping motions, along with biologically-inspired wing profiles, are of interest due to their use of natural physics. Corrugated airfoil structures appears to have poor aerodynamic performance at higher Reynolds numbers, but serve well at Re<10,000. Understanding flow structures around corrugated profiles and comparing them to a standard airfoil will aid in understanding how these corrugated profiles perform well and have been adopted by some of nature’s most acrobatic flyers. Motivation for this investigation is to compare static flow visualizations of corrugated profiles to a standard National Advisory Committee for Aeronautics (NACA) airfoil from low to high angles of attack and further observe flow structure development of a pitching and plunging flat plate at a Re<10,000 and a Strouhal number relevant to natural fliers. The static visualization was conducted at Re=1,000 with a NACA 0012 airfoil and two corrugated models. The Pitch and Plunge Fixture (PPF) developed was constructed by simplifying flapping wings as a two degree of freedom motion in plunge (translation) and pitch (rotation). Results obtained from the PPF were compared with a numerical simulation.
Development Of A Heat Transfer Test Rig For Finding Heat Transfer Characteristics Of Liquid Methane, Sergio Flores
Development Of A Heat Transfer Test Rig For Finding Heat Transfer Characteristics Of Liquid Methane, Sergio Flores
Open Access Theses & Dissertations
Most large scale rocket engines use a regeneratively cooled system to cool the rocket engine using either the rocket fuel or oxidizer. The use of liquid methane as a rocket fuel is an emerging technology proving to have several advantages over current rocket fuels. However, liquid methane is lacking the extensive research as a rocket fuel compared to highly used rocket fuels like liquid hydrogen. A heat transfer test rig was built with the goal to characterize the heat transfer characteristics of liquid methane as it passes through a heated channel. The development of the test rig underwent considerations designed …
Design And Cfd Optimization Of Methane Regenerative Cooled Rocket Nozzles, Christopher Linn Bradford
Design And Cfd Optimization Of Methane Regenerative Cooled Rocket Nozzles, Christopher Linn Bradford
Open Access Theses & Dissertations
Liquid rocket engines benefit in life cycle from the active regenerative cooling method which passes the fuel as the coolant through channels surrounding the combustion chamber. These channels are designed and optimized using structural considerations as well as heat transfer theory, then CFD simulations with the software FLUENT are performed for the final analysis. The difficulty in using methane as the fuel/coolant is addressed, and requires the use of the ideal gas numerical model in preliminary CFD simulations. Comparison to real gas numerical models is made, and results also given for one channel design. The techniques utilized herein allow the …