Digital Commons Network^™

Hydrodynamic Wave Contributions To Combustion Instability In Rockets, Esam M. T. Abu-Irshaid

Doctoral Dissertations

Experimental measurements suggest that a new source of instability in rocket motors is due to hydrodynamic disturbances. These disturbances, if ignored, could impact our assessment of rocket motor performance. In this work, the corresponding problem of hydrodynamic instability is considered. A mathematical model for these disturbances is carried out by perturbing the continuity and momentum equations. A one dimensional model which represents the wave disturbances in time and space is implemented to quantify the amplification rate, in time or space, and the wave amplitude. The only available measurements of these disturbances arise in cold flow experiments that simulate the gas …

The Thermophysical Roll Of Nanoparticles In Nanofluidic Heat And Mass Transport, Chan Hee Chon

Doctoral Dissertations

Nanofluids are colloids that consist of a base fluid and nanometer sized metallic particles, which serve to improve the heat and mass transport characteristics of nanofluids over those of the base fluid. Many researchers, attracted to the highly enhanced thermal conductivity, have studied nanofluids, and yet have never been able to reveal the basic mechanisms of their characteristic improvements. This present work thus seeks to gain an understanding of the role of nanoparticles in nanofluidic heat and mass transport characteristics through three experimental measurements: 1) thermal conductivity measurement, 2) thermophoretic motion measurement, and 3) evaporation measurement.

Using thermal conductivity, thermophoresis, …

The Stability Analysis Of Linear Dynamical Systems With Time-Delays, Ajeet Ganesh Kamath

Doctoral Dissertations

Time-delay systems, which are also sometimes known as hereditary systems or systems with memory, aftereffects or time-lag, represent a class of infinite-dimensional systems, and are used to describe, among other types of systems, propagation and transport phenomena, population dynamics, economic systems, communication net- works and neural network models. A key method for the stability analysis of time- delay dynamical systems is the Lyapunov’s second method, applied to functional differential equations. Specifically, stability of a given linear time-delay dynamical system is typically shown using a Lyapunov-Krasovskii functional, which involves a quadratic part and an integral part. The quadratic part is usually …

Analysis And Control Of Nonnegative Systems, Jayanthy Ramakrishnan

Doctoral Dissertations

Nonnegative systems are dynamical systems with nonnegative states for random non- negative initial conditions. A subclass of nonnegative systems are compartmental systems characterized by conservation laws.Nonnegative and compartmental systems have widespread applications in biological systems, medical systems, thermodynamic systems, network systems, economic systems, etc.

In this dissertation we have investigated the applications of nonnegative systems in biological and network systems. The specific focus in biological systems has been in the area of pharmacokinetics and we have addressed the consensus problem in network systems. We have specifically focused on the time-delay present in compartmental systems and have investigated the behavior of …

Cooling Of Qps Modular Coils Using Embedded Copper Tubes, Shankar Narasimhaswami

Masters Theses

In an era of insatiable appetite for energy, mankind is challenged to develop a sustainable, safe and clean means of energy production, which would virtually eliminate the existing dependence on fossil fuels. In this regard, Nuclear Fusion technology would give man a quantum leap to mark a near end to the long-term energy concerns and redefine the basis of energy production on earth and elsewhere. This explanation holds rationale on two principal elements 1-Abundant supply of cheap fusion fuel and 2-Surpassingly superior energy production efficiency.

But, as every boon comes with a ‘But’, the criticality of technology is that fusion …

A Parametric Study Of Water Vapor Condensation In Supersonic Nozzle Flow Fields, Todd Branson Vanpelt

Masters Theses

Combustion driven hypersonic and supersonic wind tunnels are impaired in their flight simulation abilities by the condensation of water vapor introduced into the test stream by the burning byproducts of air and hydrocarbon fuels. The purpose of this study is to evaluate the abilities of a condensation model to predict the beginning axial locations of vapor changing into liquid droplets and study the correlations with initial combustion chamber conditions. A test matrix with different fuels, chamber pressure, and equivalence ratio was applied to the FIRACON model written by Erickson, et al. [7] using the dimensions of the NASA Langley …

A Theory For Modified Conservation Principles Optimization Of Cfd Algorithm Fidelity, Sunil Sahu

Doctoral Dissertations

A theory is developed in one and two space dimensions that successfully predicts optimal algorithm constructions for the convection operator intrinsic to unsteady Navier- Stokes (NS) problem statements. The analysis statement is parameterized via a Taylor series (TS) modification to the parent NS conservation principles statements. Phase velocity and amplification factor error analyses are enabled via weak form discretized implementations assembled at the generic node. The parameterized error statement is then resolved into a Taylor series expansion in non-dimensional wave number space, admitting identifications that progressively annihilate lowest order error terms. The theory computational implementation is via a Galerkin weak …

Modal Analysis Of A Helicopter Wing-Pylon Structure Using Flexible Multibody Dynamics, Naresh Nilkanth Khude

Masters Theses

With the new software tools being developed for simulation of flexible multibody systems it is possible to develop the models with various missiles and launchers and study their dynamic behavior in the design stages. In most of the flexible multibody models, the flexibility modal data is obtained from the corresponding detailed finite element model.

This thesis presents the flexible multibody model development of the simplified wing- pylon structure using the Craig-Bampton approach. Since the Craig-Bampton method of Component Mode Synthesis is used, the component finite element models are developed separately without inclusion of the local joint details. This approach is …

Flow And Heat Transfer In A 2-D Channel Partially Filled With Porous Medium, Srinivas Kuppa

Masters Theses

Graphite foam, developed by the Oak Ridge National Laboratory, has shown excellent thermal properties and has potential applications for compact heat exchangers. The flow and heat transfer characteristics of a 2-D channel partially filled with graphite foam as the porous medium are determined. A steady, incompressible and constant-property water flow is modeled using the commercial software COMSOL^â. Flow is uniform at the inlet and the base of the foam is subjected to a constant heat flux boundary condition. The permeability( 7x10^-8 to 1.4x10^-6 m²)and the dimensionless height of the porous block are varied. Heat …

Accelerated Poisoning Of Diesel Oxidation Catalysts By Zinc Dialkyldithiophosphate-Derived Phosphorus, Scott Joseph Eaton

Masters Theses

The phosphorus poisoning of diesel oxidation catalysts (DOCs) by the lube-oil additive zinc dialkyldithiophosphate (ZDDP) is investigated in the present study. A 517 cc single-cylinder, naturally aspirated direct-injection diesel engine is used to accelerate the phosphorus poisoning of DOCs by artificially increasing the ZDDP consumption to approximately 700 times of that found during normal engine operation. Three methods of accelerating the ZDDP consumption rate are investigated, which have been shown in previous literature to cause phosphorus poisoning. These include the injection of high concentration ZDDP-doped lube-oil blended with diesel fuel though the fuel injector as well as injecting ZDDP-doped lube-oil …

Characterizing Monolithic Lean Nox Trap Catalysts Using A Bench-Flow Reactor, Hakyong Kim

Masters Theses

The performance of EmeraChem Lean NO_x Trap (LNT) catalysts with company proprietary washcoat formulation has been investigated using a bench-flow reactor (BFR). The washcoat composition consists of Pt, the precious metal component (PM), and two NO_x storage media of Ba and K, supported on g-Al₂O₃ washcoat.

A series of isothermal absorption experiments was carried out at different temperatures and gas hourly space velocities (GHSVs) in order to investigate the effect of temperature and GHSV on the nitrogen oxides (NO_x) trapping capacity of EmeraChem LNT catalysts. The NO_x storage capacity exhibits a “volcano-type” …

Development Of A Potentially Accurate And Efficient Les Cfd Algorithm To Predict Heat And Mass Transport In Inhabited Spaces, Marcel Andre Grubert

Doctoral Dissertations

During the last decades many advances have been made in the prediction of turbulent flow behavior, due largely to new achievements in the field of computational fluid dynamics (CFD). For many years the Reynolds-averaged Navier-Stokes (RaNS) approach, which employs time-averaging, has been the work-horse of the industry in predicting turbulent flow in real-world applications. Although the accuracy of those turbulent flows and the details in flow structure are mostly limited due to its empirical modeling approach, the RaNS based algorithms are able to achieve solutions in relative short amounts of computational time using relatively coarse meshes.

But with increased computational …

High Performance Control Of A Transmission Based Servo Actuator System, Renbin Zhou

Doctoral Dissertations

High performance actuation is a key factor in the industrial robot area. The transmission based servo actuator system (TBA) is a new type of robot actuator with a brushless DC servo motor and a three speed discrete variable transmission (DVT). The proposed TBA design can match the performance of a typical hydraulic actuator with compact size and weight.

The TBA is a typical hybrid dynamic system consisting of three continuous dynamic systems and a discrete state controller. This dissertation addresses the fundamental problems associated with the TBA system control from a hybrid system point of view.

A detailed dynamic model …

Design Of A Single Axle Regenerative Brake System For A 2005 Thru-The-Road Hybrid Electric Chevrolet Equinox, John William Miller

Masters Theses

The University of Tennessee through its mechanical engineering department is participating in an advanced vehicle design competition, Challenge X, sponsored by the Department of Energy and General Motors. Participants are challenged with redesigning a 2005 Chevrolet Equinox that will minimize energy consumption and reduce emissions while maintaining the stock performance, safety, and utility of the vehicle. The overall vehicle architecture and control system for Tennessee's vehicle entry is described while focus is given to the design of the single axle series regenerative braking system. A series regenerative braking system provides a means of capturing the kinetic energy otherwise lost in …

Design Of A Catalyst System With Periodic Flow Reversal For Lean Burn Natural Gas Engines, Balaji Ramamurthy

Masters Theses

The objective of this research is to accomplish methane conversion from lean burn natural gas engines. As methane conversion requires high temperatures, the concept of PFR (Periodic Flow Reversal) is used. The PFR is a heat trap that performs active heat recovery in addition to the heat retention capability of monolith solids. Cyclically alternating the direction of exhaust flow produces a thermal wave along the center of the catalyst thereby elevating the temperature above the engine exhaust temperature. The PFR loop is developed connecting catalyst canisters with a Four-Way Single Diversion Valve (FWSDV) using a set of pipes and pipe …

Modeling Of Tapered Corrugated Graphite-Foam Heat Exchangers, Abdoulaye Sy

Masters Theses

Practical applications of compact heat exchangers, using low-permeability (1.4e-10 m²) high-conductivity (150 W/m-K) graphite-foam for heat transfer enhancement, are often limited by the excessive pressure-drop.

In an earlier study, Norton (2003), using straight-cut corrugations through the entire height of the graphite-foam heat exchanger, identified minimal pressure-drop configurations. For these optimal configurations, pressure-drop reductions of nearly two orders of magnitude were achieved when compared to a full block of graphite foam. With a constant heat flux (12 W/cm²) boundary, the high thermal conductivity of the foam has resulted in heat transfer values that are two orders of …

Grasping Strategies For A Dexterous Hand During Teleoperation, Prem Sagar Chidambaram

Masters Theses

Telerobotics is an interdisciplinary branch of engineering that deals with the control of robots at a distance in a manner that entails the intuition and the physical involvement of the operator controlling the robot. The end of the robotic manipulator consists of a device called an end effector that is used to hold the tools. Most telerobotic systems employ a simple single degree of freedom end effector called a parallel jaw gripper. Since such end effectors have just one degree of freedom and hence limited dexterity, it is essential to develop special fixtures to be attached to the tool …

First And Second Law Analyses Of Conventional And Advanced Combustion Modes, Christopher Robert Hamilton

Masters Theses

The objective of this paper was to perform first and second law analyses of conventional and advanced combustion modes. The data to be analyzed came from two computer models. The first model simulated a modified Mercedes diesel engine operating in the conventional mode, and the second simulated operation in the advanced combustion mode.

Each model was constructed using geometric measurements from the experimental engine setup. Experimental data were used to correlate the output from the models with that of the actual engine. Once each model was deemed valid, its output was subjected to a first and second law analysis.

In …