Master of Science / Department of Mechanical and Nuclear Engineering / Mohammad H. Hosni / Byron W. Jones / In 2010, over 786 million passengers flew on commercial flights in the United States according to the Bureau of Transportation Statistics (2011). With the average flight length over 1300 miles for domestic flights, this amounts to billions of hours spent aboard airliners by passengers each year. During these flights, diseases and other harmful contaminates, some malicious, can spread throughout aircraft cabins, harming passengers. Aircraft ventilation systems are designed to remove these harmful contaminates as quickly as possible to minimize spread in cabin air. Disruptions to the design airflow pattern can hinder the effectiveness of contamination removal efforts. A common form of this airflow disruption is longitudinal air movement through cabin aisles. To examine the effect of contaminate transport down aircraft aisles by a moving body, a motorized beverage cart is past by a contamination source as it traverses the length of the cabin aisle. An experimental study is performed in a mockup Boeing 767 cabin section consisting of eleven rows with seven seats per row. Carbon Dioxide (CO2) tracer gas is injected at a constant flow rate at a location of interest until concentrations in the cabin reach steady state. Ventilation equipment and flow rates representative of an actual aircraft are used for all experiments. Seats in the mockup are occupied by thermal manikins to simulate passenger heat load. A motorized beverage cart traverses the length of the cabin aisle passing by the injection location. The concentrations of tracer gas displaced by the cart are measured at locations throughout the cabin. Comparing these measurements to baseline readings taken with no cart movement, a map of the degree to which contaminant transport is affected by the beverage cart is calculated. The cabin mockup is supplied by 100% outdoor air through actual Boeing supply ductwork and linear diffusers along the cabin length above the aisles. The CO2 level is measured in the inlet air, measurement locations in the cabin, and exhaust air using nondispersive infrared (NDIR) sensors. Measured results are reported for all (54) seat locations downstream of the cart traverse/injection location for an injection location near the rear of the cabin. Analogous measurements are also conducted examining the effect of variations in cart speed and modified injection location. It was found the beverage cart movement had an effect of up to a 35% increase in tracer gas concentration relative to the local steady state concentration for several seat locations adjacent to the aisle. This increased concentration continued for only a few minutes in all cases, but was generally less than the steady state exposure one row closer to the injection location. Moving in the lateral direction away from the aisle, the variance in tracer gas concentration due to the cart movement diminished quickly. The significance of increased concentration for such short periods of time in comparison to the length of actual commercial flights may require further biological analysis. The data showed general tracer gas concentration increases due to cart movement in a small section of the cabin mockup which could warrant further analysis, but increases were generally insignificant when considering entire flight contamination exposure levels.

Master of Science / Department of Mechanical and Nuclear Engineering / Steve Eckels / A new three dimensional transient human finger model was developed to predict the risk of frostbite in humans at different environmental conditions. The shape of the finger model was similar to that of a real human finger. Finite Element Techniques were used to build the finger model. Smith’s Model (1991) energy balance equations were used to calculate the temperatures in the current finger model. The current 3D finger model was validated against the experimental data of Wilson (1976) and Santee (1990). The model agreed well with the Wilson experiments and with the cold test in Santee experiments. The comparison indicates that the current finger model can be used to adequately predict the human finger responses in different environments. The current finger model was then tested in temperatures of 0, -10, -20, -25 and -30 oC and with different airspeeds 0, 3 and 6.8 m/s to assess the risk of frostbite in humans. Three resistances 0, 0.4 and 0.8 clo were used on the finger model to obtain responses in different environmental conditions. From the experimental results, an expression for safe glove resistance required to prevent frostbite in known temperatures was calculated. Also, the temperatures up to which a glove with known thermal resistance value can protect a human finger from frostbite was also computed.

Master of Science / Department of Mechanical and Nuclear Engineering / Steven Eckels and Mohammad Hosni / This research presents results from experimental and numerical investigations of two-phase flow pattern analysis in a staggered tube bundle. Shell-side boiling tube bundles are used in a variety of industries from nuclear power plants to industrial evaporators. Fluid flow patterns in tube bundles affect pressure drop, boiling characteristics, and tube vibration. R-134a was the working fluid in both the experimental and computational fluid dynamics (CFD) analysis for this research. Smooth and enhanced staggered tube bundles were studied experimentally using a 1.167 pitch to diameter ratio. The experimental tube bundles and CFD geometry consist of 20 tubes with five tubes per pass. High speed video was recorded during the experimental bundle boiling. Bundle conditions ranged in mass fluxes from 10-35 kg/m[superscript]2.s and inlet qualities from 0-70% with a fixed heat flux. Classification of the flow patterns from these videos was performed using flow pattern definitions from literature. Examples of smooth and enhanced bundle boiling high speed videos are given through still images. The flow patterns are plotted and compared with an existing flow pattern map. Good agreement was found for the enhanced tube bundle while large discrepancies exist for the smooth tube bundle. The CFD simulations were performed without heat transfer with non-symmetrical boundary conditions at the side walls, simulating rectangular bundles used in this and other research. The two-phase volume of fluid method was used to construct vapor interfaces and measure vapor volume fraction. A probability density function technique was applied to the results to determine flow patterns from the simulations using statistical parameters. Flow patterns were plotted on an adiabatic flow pattern map from literature and excellent agreement is found between the two. The agreement between simulation results and experimental data from literature emphasizes the use of numerical techniques for tube bundle design.

Master of Science / Department of Mechanical Engineering / Donald L. Fenton / This project was done to determine the effectiveness of different methods of mitigating the effects of an ammonia release through a pressure relief device in an ammonia refrigeration system. Several methods were considered, and five were selected for further study. The methods chosen for further study were discharge into a tank containing standing water, discharge into the atmosphere, discharge into a flare, discharge into a wet scrubber, and an emergency pressure control system. Discharge into a tank containing standing water is the most common method in existence today but several people in the ammonia refrigeration industry have questioned its reliability. The methods were compared based on a quantitative risk analysis, combining failure rates of each system with ammonia dispersion modeling and the monetized health effects of a system’s failure to contain an ammonia release. It was determined that the release height had a greater influence on the downwind cost impact than any other variable, including weather conditions and release from multiple sources. The discharge into a tank containing standing water was determined to have the lowest failure rate, while the flare system was found to be the most effective in terms of relative overall release consequent cost. The emergency pressure control system is now required by the codes, and any of the other mitigation systems would be very effective when used in conjunction with the emergency pressure control system.

Master of Science / Department of Mechanical and Nuclear Engineering / Warren N. White / Mechanical systems play an integral part in our everyday lives. A subset of these systems can be described as underactuated; the defining characteristic of underactuated mechanical systems is that they have fewer control inputs than degrees of freedom. Airplanes, rockets, helicopters, overhead crane loads, surface vessels, and underwater vehicles are all examples of such systems. The control challenges associated with these systems arise from both the underactuation of the control input and the nonlinear nature of the dynamic equations describing the system’s motion. In this work, a control method for stabilization and tracking based on Lyapunov stability theory is presented. The remarkable result of this tracking controller development is that we arrive at three matching equations that are (with the exception of ) identical to matching equations developed for stabilization as shown in White et al. (2006, 2007, 2008). Asymptotic stabilization of the tracking errors (s) is not obtained. However, the norm of s (||s||) will decrease until an ultimate bound is reached, then it will stay within this bound. A lemma is provided for estimating this bound and it is shown that the magnitude of the bound depends upon the eigenvalues and norms of certain matrices in the Lyapunov formulation. Three examples are presented to illustrate the effectiveness of the direct Lyapunov approach. Two examples of holonomic systems are presented. The first is an inverted pendulum cart which is used to illustrate the formulations performance to tracking a desired path on the cart position or actuated axis. The second example is a ball and beam system in which a desired path is tracked by the ball or unactuated axis. The tracking control technique is also applied to an example of a nonholonomic system, a rolling wheel. The control technique is applied in two alternate manners. Finally, the controller is implemented on a laboratory inverted pendulum cart system in hard real time. A desired trajectory for the cart position is tracked and the control law is used to define the desired pendulum trajectory.

Doctor of Philosophy / Department of Mechanical and Nuclear Engineering / Kirby S. Chapman / This work includes a thermodynamic analysis of a large-bore two-stroke cycle engine air management system, resulting in the development of new software, for the purpose of analyzing: 1) the cylinder-to-cylinder distribution of charge air, 2) pollutant emission concentrations, and 3) energy availability to the turbocharger turbine. During the course of the thermodynamic analysis, four new algorithms were developed: 1. Charge Air Integrated Manifold Engine Numerical Simulation (CAIMENS), 2. Turbocharged-Reciprocating Engine Compressor Simulation (T-RECS) Nitrogen Oxide Kinetic Model, 3. T-RECS Carbon Monoxide Kinetic Model, and 4. Exhaust Manifold Design Software (EMDS). The EMDS, which integrates the three previously developed algorithms, can forecast pulsation and possible unbalanced air delivery and interference within the intake system and simulates energy release and pollutant emission formation during and just after the combustion event. Specifically, the EMDS outputs a transient spatial and temporal distribution of pressure and temperature within the engine exhaust stream. Beyond the development of the four engine characterization algorithms, an air flow balancer (AFB) was designed using data from the CAIMENS algorithm. This AFB as part of an overall Active Air Control system was used to balance the cylinder-to-cylinder distribution of air by the engine air management system and reduce total engine pollutant emission production.

Robotic microassembly is a process to leverage intelligent micro-robotic technologies to manipulate and assemble three-dimensional complex micro-electromechanical systems (MEMS) from a set of simple-functional microparts or subsystems. As the development of micro and nano-technologies has progressed in recent years, complex and highly integrated micro-devices are required. Microassembly will certainly play an important role in the fabrication of the next generation of MEMS devices. This work provides advances in robotic microassembly of complex three-dimensional MEMS devices. The following key technologies in robotic microassembly are studied in this research: (i) the design of micro-fasteners with high accuracy, high mechanical strength, and reliable electrical connection, (ii) the development of a microassembly strategy that permits the manipulation of microparts with multiple degrees of freedom (DOFs) and high accuracy, (iii) fully automated microassembly based on computer vision, (iv) micro-force sensor design for microassembly. An adhesive mechanical micro-fastener is developed to assemble micro-devices. Hybrid microassembly strategy, which consists of pick-and-place and pushing-based manipulations, is employed to assemble three-dimensional micro-devices with high flexibility and high accuracy. Novel three-dimensional rotary MEMS mirrors have been successfully assembled using the proposed micro-fastener and manipulation strategy. Fully automatic pick-and-place microassembly is successfully developed based on visual servo control. A vision-based contact sensor is developed and applied to automatic micro-joining tasks. Experimental results show that automatic microassembly has achieved sub-micron accuracy, high efficiency, and high success rate. This work has provided an effective approach to construct the next generation of MEMS devices with high performance, high efficiency, and low cost.

Experiments were conducted to compare mixing and combustion of natural gas jets from round and elliptical nozzle holes in an optically accessible combustion bomb. A flame ionization detector was used to measure the concentration fields of the two jet types. Pressure data, combustion imaging, and hydrocarbon measurements of exhaust gas were used to compare the ignition delay, heat release, and combustion efficiency of the two nozzles. Concentration measurements indicated that the elliptical nozzle produced jets with smaller rich core regions and lower peak concentrations at all conditions. Firing tests indicated that the two nozzles produced equivalent ignition delays. Peak heat release rates were higher for the round nozzle, while the elliptical nozzle produced smoother transitions from premixed to diffusion burning. Combustion efficiency was slightly higher for the round nozzle. Results indicate that elliptical nozzles could potentially lower NOx and particulate emissions, but further experiments are required to test this hypothesis.

Two formal design methodologies, biomimetic design and the Theory of Inventive Problem Solving, TRIZ, were applied to the redesign of a Proton Exchange Membrane (PEM) fuel cell. Proof of concept prototyping was performed on two of the concepts for water management. The liquid water collection with strategically placed wicks concept demonstrated the potential benefits for a fuel cell. Conversely, the periodic flow direction reversal concepts might cause a potential reduction water removal from a fuel cell. The causes of this water removal reduction remain unclear. In additional, three of the concepts generated with biomimetic design were further studied and demonstrated to stimulate more creative ideas in the thermal and water management of fuel cells. The biomimetic design and the TRIZ methodologies were successfully applied to fuel cells and provided different perspectives to the redesign of fuel cells. The methodologies should continue to be used to improve fuel cells.

In this thesis, a methodology for rigid body dynamic modeling and control design is presented for a 6 degree-of-freedom (DOF) parallel-kinematic-mechanism-based reconfigurable meso-milling machine tool (RmMT) with submicron tracking accuracy requirement. The dynamic modeling of the parallel kinematic mechanism (PKM) is formulated using the Lagrangian method with the application of principle of energy equivalence and coordinate transformations to separate the mechanism into serial sub-systems. The rigid body gyroscopic force is also modeled using this approach and its effect as a disturbance is analyzed and compensated. The contour errors for both position and orientation are formulated to increase machining accuracy. The dynamic model of the system is linearized through feedback linearization and the contour error based feedback control law is formulated using the convex combination design approach to satisfy a set of design specifications simultaneously. The dynamic model and its control methodology are simulated and verified within the MATLAB Simulink environment.