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Full-Text Articles in Mechanical Engineering

Numerical Study Of Three-Dimensional Free Convection From Semi-Enclosed Geometry And Discontinuous Heat Sources, Aklilu T.G. Giorges Dec 1997

Numerical Study Of Three-Dimensional Free Convection From Semi-Enclosed Geometry And Discontinuous Heat Sources, Aklilu T.G. Giorges

Dissertations

Three-dimensional natural convection from three-by-three array of isoflux heat sources mounted on one vertical wall of semi-enclosed region has been numerically investigated. Detailed thermal information of this important engineering configuration is currently not available. The major objective of this study was to obtain this needed thermal and velocity information.

The semi-enclosed geometry can be viewed as a thin rectangular region with four closed and two open sides. The open surfaces are located at the top and adjacent side. For the fluid air, Pr = 0.71, the study covered a heat flux based Rayleigh number (Ra) range of (102 ≤ R ...


Automobile Air Bag Inflation System Based On Fast Combustion Reaction, Yacoob Tabani Oct 1997

Automobile Air Bag Inflation System Based On Fast Combustion Reaction, Yacoob Tabani

Dissertations

Current automobile air bag inflator technology is complex, expensive and environmentally unsafe. A new and novel air bag inflator based on fast combustion reactions of methane-oxygen mixtures has been developed and studied. The thermodynamics and mass flow parameters of this new inflator have been modeled and found to be in agreement with experimental results.

The performance of the fast combustion inflator was evaluated in terms of pressure-time relationships inside the inflator and in a receiving tank simulating an air bag as well as the temperature-time relationship in the tank.

In order to develop this fast combustion inflator, several critical issues ...


Electrocatalytic Control Of Exhaust Soot, Victor L. Callahan Oct 1997

Electrocatalytic Control Of Exhaust Soot, Victor L. Callahan

Dissertations

The feasibility of combining electrostatic precipitation and use of a catalytic wall in a straight tube reactor as a means of destroying soot particles was investigated. Enhanced particle diffusion to the wall by an applied electric field provided the means of particle capture for subsequent catalytic oxidation at the active surface in a small length tube.

Soot particles flowing in a gas stream are influenced by the following transport mechanisms: convective flux as a result of bulk flow, diffusion flux as a result of particle concentration or number density gradient, and an electrostatic flux from the coulombic attraction as charged ...


The Fatigue Problems Of Cracks Subjected To Obliquely Incident Stress Waves, I-Chung Weng May 1997

The Fatigue Problems Of Cracks Subjected To Obliquely Incident Stress Waves, I-Chung Weng

Dissertations

Catastrophic failure of aircraft and other structures are often caused by undetected cracks. Fracture mechanics has been developed to augment traditional static and fatigue design. In the static theory of fracture mechanics, extensive treatment has been given to the stress distribution around sharp cracks and notches under various loading conditions. Previous works on the problems of dynamic loadings are not accurate in dealing with singularities at high frequencies. The numerical solutions become unrealistic at high frequencies in many practical applications.

To address the need to obtain the stress intensity factor in high frequency dynamic loading situations, we studied the use ...


Particle Deposition From Turbulent Flow In A Divergent Channel, Wai-Ting Huang May 1997

Particle Deposition From Turbulent Flow In A Divergent Channel, Wai-Ting Huang

Dissertations

This dissertation presents a numerical analysis of particle deposition from a dilute gas-solid two-phase suspension in a divergent channel. The Lagrangian governing equations for particle motion include inertia force, viscous force, gravity force and image force from electrostatic charge on the particle. The incompressible two-dimensional turbulent flow field in a divergent channel is solved by employing a Κ-ε modeling technique with FIDAP finite element CFD software. A computational procedure is developed to incorporate the flow field into numerical simulation of particle trajectories from which the fraction of deposition is determined. Several divergent channels (half divergent angles of 0°, 7.5 ...


Modeling Of 3d Swept Volumes Using Sde/Sede Methods And Its Application To Five-Axis Nc Machining, Liping Wang May 1997

Modeling Of 3d Swept Volumes Using Sde/Sede Methods And Its Application To Five-Axis Nc Machining, Liping Wang

Dissertations

This research falls in two important areas in solid modeling and manufacturing automation: (1) swept-volume modeling; (2) computer-based NC (Numerically controled) machining simulation and verification. The swept volume is defined as the volume swept by an object undergoing an arbitrary motion. Modeling of 3D swept volumes includes the boundary computation and representation of a swept volume generated by a general object undergoing general motion in three dimensional space. The Sweep Differential Equation (SDE) and Sweep Envelope Differential Equation (SEDE) methods are two of the important swept volume modeling methods employed in this dissertation. They exploit differential equations to obtain the ...