Master of Science, The Ohio State University, 2020, Mechanical Engineering

The Ohio State EcoCAR team is a student project team at The Ohio State University providing real-world engineering experience and learning opportunities to engineering students. The EcoCAR Mobility Challenge is sponsored by the U.S. Department of Energy, General Motors, and The Mathworks and challenges twelve universities across the United States and Canada to redesign and reengineer a 2019 Chevrolet Blazer into a hybrid-electric vehicle. The goal of the competition is for students to develop and implement technologies to reduce the vehicle's environmental impact while maintaining performance and to enhance the vehicle with connected and automated technologies for a future in the mobility-as-a-service market. The transition from conventional to hybrid vehicle requires the addition of several hybrid powertrain components, including electric motors, power inverters, and a high voltage battery. These new components have thermal cooling requirements and require the integration of a dedicated thermal management system to prevent components from overheating and to maintain optimal operating temperature. This work models the thermal systems of the internal combustion engine and hybrid powertrain components to provide estimates for component temperatures during steady-state operation and predetermined drive cycles. The GT-Suite modeling software package from Gamma Technologies was chosen to model the two thermal systems because of its extensive library of pre-validated automotive grade component models. This library allowed component models to be built quickly and without extensive data collection. The thermal system models were integrated with a full-vehicle model of the OSU EcoCAR team's vehicle in Simulink. This work seeks to provide a reasonable approximation of the integrated thermal systems in the OSU EcoCAR vehicle, with provisions to update and calibrate the model in the future. The model provides both steady-state and drive cycle feedb (open full item for complete abstract)

Committee: Shawn Midlam-Mohler (Advisor); Giorgio Rizzoni (Committee Member) Subjects: Engineering; Mechanical Engineering

Master of Science, The Ohio State University, 2016, Mechanical Engineering

This research investigates the design and implementation of a light-duty truck's thermal management system control strategy developed from model-based techniques. To give robust durability and improve fuel economy, the control strategy must stabilize the dynamics of the engine operating temperatures, while also minimizing the energy consumed by the system. First, a detailed plant model is obtained by applying first principle physics (conservation laws) to model the thermal management system from its key components. The component models are combined to accurately predict the flow rates and temperatures of the system. The thermal system model is fed by a vehicle drivetrain mechanical model that calculates the heat rejection to the thermal model through a backward-looking approach. The nonlinear model is calibrated on supplier data and validated using experimental data recorded by a vehicle data acquisition system. Information from the engine control unit, flow rates, and temperatures were previously recorded for various driving profiles while the vehicle operated on a chassis dynamometer according to standard test procedure. The model accurately predicts the temperature dynamics of the system during transient operations of fully-warm drive cycles. Specifically, the Environmental Protection Agency's Federal Test Procedure for a highway drive cycle was used to test the model validity. The validated model provides a benchmark for comparing new controllers to the baseline thermal management control. Next, a model-based control strategy is developed to operate the thermal management system for tracking the desired fluid temperatures and limit the usage of the radiator fan, hence saving energy. In order to do so, the full system architecture was simplified using heat transfer analysis before utilizing an order-reduced, physical model that is linearized analytically. The reduced, linear plant models are then used to design a feedback controller by applying the Se (open full item for complete abstract)

Committee: Marcello Canova PhD (Advisor); Lisa Fiorentini PhD (Committee Member) Subjects: Automotive Engineering; Mechanical Engineering

Master of Science in Engineering (MSEgr), Wright State University, 2015, Renewable and Clean Energy

A statistical based verification and validation process is applied to the transient modeling of a shell and tube heat exchanger. A generic model of a heat exchanger was developed based on first principles as a sub-system of a larger thermal system model. This model was originally created without any experimental data, as it was not readily available. To provide the data necessary to apply the validation process, a thermal emulator was designed and built that allowed control of all system inputs to the heat exchanger, while also providing the instrumentation to record all required data. A wide test matrix was chosen to fully encompass the expected operational envelope of the heat exchanger. Focus on the collection of experimental data was the minimization of uncertainty, as these uncertainties were amplified once they were propagated through the validation process. The validation process encompasses the completion of sensitivity and uncertainty analyses, uncertainty propagation, verification, and validation. Once these steps were completed using a set of non-ideal experimental data, uncertainty in the transient heat exchanger model is quantified. This manuscript proposes a way to complete the validation process without replicate data sets by utilizing known information about the physical process. At the completion of the process, both uncertainties and model form error are quantified for the system outputs and a statistical validation metric is applied. These outputs help to define whether or not the model captures the physical process to a satisfactory degree while also highlighting avenues for improvement if the uncertainty is deemed too large for the intended application.

Committee: Rory Roberts Ph.D. (Advisor); Scott Thomas Ph.D. (Committee Member); J. Mitch Wolff Ph.D. (Committee Member) Subjects: Engineering; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2013, Mechanical Engineering

A crucial step towards the large-scale introduction of plug-in hybrid electric vehicles (PHEVs) in the market is to reduce the cost of their energy storage systems. One of the goals of U.S Department of Energy (DOE) Vehicle Technologies Program for hybrid electric systems is to, by 2014, reduce the production cost of Li-ion batteries by nearly 70 percent from 2009 costs. Currently, battery cycle- and calendar-life represents one of the greatest uncertainties in the total life-cycle cost of advanced energy storage devices. Batteries are inherently subject to aging. Aging is the reduction in performance, availability, reliability, and life span of a system or component. The generation of long-term predictions describing the evolution of the aging in time for the purpose of predicting the Remaining Useful Life (RUL) of a system may be understood as Prognosis. The field of battery prognosis has seen progress with respect to model based and data driven algorithms to model aging and estimate RUL of battery cells. However, in advanced battery systems, cells are interconnected and aging propagates. The aging propagation from one cell to others exhibits itself in a reduced system life. Propagation of aging has a profound effect on the accuracy of battery systems state of health (SOH) assessment and prognosis. This thesis proposes a systematic methodology for modeling the propagation of aging in advanced battery systems. The modeling approach is such that it is able to predict battery pack aging, thermal, and electrical dynamics under actual PHEV operation, and includes consideration of random variability of the cells, electrical topology and thermal management. The modeling approach is based on the interaction between dynamic system models and dynamic models of aging propagation. The system level SOH is assessed based on knowledge of individual cells SOH, electrical topology and voltage equalization approach. The proposed methodology is used to develop a computational model- (open full item for complete abstract)

Committee: Giorgio Rizzoni (Advisor); Simona Onori (Advisor); Yann Guezennec (Committee Member); Manoj Srinivasan (Committee Member); Zhang Wei (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2022, Mechanical Engineering

Global regulatory targets for reducing CO2 emissions along with the customer demand is driving the automotive sector towards energy efficient transportation. Powertrain electrification offers great potential to improve the fuel economy due to the extra control flexibility compared to vehicles with a single power source. The benefits of the electrification can be significantly reduced when auxiliaries such as the vehicle climate control system directly competes with the powertrain for battery energy, reducing the range and energy efficiency. Connected and Automated Vehicles (CAVs) can increase the energy savings by allowing to switch from instantaneous optimization to predictive optimization by leveraging information from advanced navigation systems, Vehicle-to-Infrastructure (V2I) and Vehicle-to-Vehicle (V2V) communication. In this work, two energy optimization problems for CAVs are studied. First is to jointly optimize the vehicle and powertrain dynamics and the second is to optimize the vehicle climate control system. The focus of this work is to combine the Dynamic Programming (DP), Approximate Dynamic Programming (ADP) and perturbation theory based approaches to solve the energy optimization problems with variations in external inputs and parameters that affects the plant model, objective function or constraints. To this end, mathematical methods are used to develop two novel algorithms that compensates for mismatches between nominal and estimated parameters. The first approach develops a cost correction scheme to evaluate the sensitivity of the value function to parameters, with the ultimate goal of correcting the original optimization problem online with the observed parameters. Two case-studies are considered with variations in vehicle payload and auxiliary power load. Second, a novel algorithm for solving dynamic optimization problem is developed to apply closed-loop corrections to solution of the original optimization problem without the need to (open full item for complete abstract)

Committee: Marcello Canova (Advisor); Abhishek Gupta (Committee Member); Stephanie Stockar (Committee Member) Subjects: Engineering; Mechanical Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2021, Mechanical Engineering

Indoor thermal comfort in residential buildings is usually achieved by tenants manually adjusting fixed temperature set-points; this is known as a ‘static' method. Prior research has explored automated control of thermal comfort based on the concept of a Predicted Mean Vote (PMV) index, which has been developed to provide a model of perceived human comfort. However, one of the dominant contributions to this index, the Mean Radiant Temperature (MRT), effectively the mean radiant temperature of the surrounding interior surfaces, has either been: 1) inaccurately assumed to be the same as indoor air temperature; and/or 2) costly to implement due to the need for numerous additional sensors. Research is posed to leverage prior work in automatically estimating the R-values of walls and ceilings using a combination of smart WiFi thermostat, building geometry, and historical energy consumption [51] to estimate the MRT with accuracy and thus provide a means to control for comfort, rather than temperature alone. In order to assess the energy saving potential of comfort control for any residence, a machine learning model of the indoor temperature based upon a NARX Neural Network is employed. This model leverages historical thermostat and weather data to develop a means to dynamically predict the interior temperature. With a developed model, it is possible to simulate different temperature set-points on indoor temperature, and thus identify the optimal set-point temperature at all times needed to maintain a reasonable comfort condition. Application of this ideal temperature set-point for minimum human comfort to historical weather data and indoor weather conditions can yield an estimate for minimum cooling energy. The initial results showed cooling energy savings in excess of 83% and 95%, respectively, for high- and low-efficiency residences. Based on this research, it is proposed that the approach to estimate MRT can be used to calculate a more accurate PMV value and a better r (open full item for complete abstract)

Committee: Timothy Reissman (Committee Chair); Rajen Rajendran (Committee Member); Andrew Chiasson (Committee Member); Kevin Hallinan (Committee Co-Chair) Subjects: Energy; Mechanical Engineering

Master of Science, The Ohio State University, 2021, Electrical and Computer Engineering

The Ohio State EcoCAR team is a student project team at The Ohio State University that competes in the Advanced Vehicle Technology Competition series sponsored by Argonne National Laboratories, General Motors, and Mathworks. The current iteration, the EcoCAR Mobility Challenge, challenges 11 universities to reengineer a 2019 Chevrolet Blazer into a hybrid-electric vehicle with added autonomous functionalities. The goal of this competition is to provide students an opportunity to gain real-world engineering experience while they work to decrease the vehicle's environmental impact and increase the autonomous capabilities of the vehicle. The competition series spans over a four-year design cycle that consists of simulation/modelling, vehicle propulsion and autonomous integration, and vehicle calibration/optimization. To convert the Blazer into a hybrid-electric vehicle, the addition of high voltage components like electric motors, inverters, and battery packs is necessary. When adding high voltage components like electric motors though, the thermal management strategy of these components becomes an important design factor that must be considered. Thermal management strategies can consist of integrating thermal loops into the vehicle to physically remove heat from these components, but these strategies can also consist of control-based methods. To prevent a rear electric motor overheating issue like the team experienced in the EcoCAR 3 competition series, a focus was put on developing an adaptive torque control strategy to limit torque requests based on motor temperature. This work discusses the development process for this adaptive torque control strategy. A thermal model was first adapted to fit the EcoCAR Mobility Challenge application to estimate the temperatures of the motor winding, rotor, and stator core/housing. Unknown motor parameters had to be found for the EcoCAR motor using an optimization and error calculation MATLAB script, and the α parameter for p (open full item for complete abstract)

Committee: Shawn Midlam-Mohler Dr. (Advisor); Giorgio Rizzoni Dr. (Committee Member) Subjects: Automotive Engineering; Electrical Engineering

Master of Science (M.S.), University of Dayton, 2021, Materials Engineering

VO2 is a type of phase change material (PCM) that can switch between a metallic state and a semiconducting state at a temperature of around 68 °C. This produces a large change in electrical resistance (almost three orders of magnitude) and large optical changes. Since this phase change occurs close to room temperature, VO2 has a large number of potential applications, such as thermally activated switches, optical modulators and optical limiters. Due to the multiple oxidation states of vanadium, VO2 thin films are typically difficult to produce. Traditionally, they are produced by reactive physical vapor deposition on heated substrates. In our research group, we have developed a different method where VO2 thin films are fabricated by thermal oxidation of PVD-deposited metallic vanadium films. Due to the high reactivity of vanadium, even small changes in the oxidation conditions will result in significant variations in the oxide films. In this thesis, we have examined the uniformity of VO2 films using stylus profiling, SEM, and 4-point probe measurements. The thickness expansion of the films due to oxidation was calculated and verified against experimental data. We also characterized the temperature profile inside the oxidation furnace. In addition, following an approach similar to the thermal oxidation of silicon, a vanadium oxidation model combining multiple oxidation states has been proposed and developed.

Committee: Andrew Sarangan Ph.D., M.A., P.E. (Advisor); Terrence Murray Ph.D. (Committee Member); Christopher Muratore Ph.D. (Committee Member); Robert Wilkens Ph.D., P.E. (Other); Eddy Rojas Ph.D., M.A., P.E. (Other) Subjects: Engineering; Materials Science; Optics

Master of Science in Mechanical Engineering (MSME), Wright State University, 2019, Mechanical Engineering

Lubrication is provided to the gear trains in automotive and aerospace transmission systems to prevent mechanical contact through the formation of a full lubricant film, which in turn removes heat generated at the gear contact surfaces. When debris blocks the inlet nozzle, the flow of lubricant is restricted and mechanical components experience lubrication starvation. Under starved lubrication the temperatures of the contact surfaces become elevated which can lead to the formation of a weld between them, a catastrophic failure mode called scuffing. For spur gears, the occurrence of scuffing is due to high sliding in the vicinity of the root or tip, where the shear thinning effect decreases the lubrication film thickness. This lubricant depletion increases the contact pressure and frictional heat flux beyond a critical limit, resulting in weld formation. The weld is immediately torn apart by the continuous relative motion of the components, causing extreme damage to the tooth surfaces. The objective of this study is to characterize the tribological behavior of high sliding gear contacts under starved lubrication. This is achieved through numerical flow simulations which utilize a generalized Reynolds equation with a non-Newtonian flow coefficient, and incorporate the dependence of lubricant viscosity on pressure and temperature. In order to study the effects of lubrication starvation a film fraction parameter is used in the Reynolds equation, removing the need for measured or assumed inlet lubrication geometry. This work presents a parametric study of engineering surface profiles under different operating conditions to show an asymptotic relationship between flash temperature and the severity of the lubrication starvation, supported by an analysis of pressure, film fraction parameter, friction coefficient, and power loss. The results of these investigations justify further numerical and experimental studies of scuffing failure for gear contacts.

Committee: Sheng Li Ph.D. (Advisor); Harok Bae Ph.D. (Committee Member); Ahsan Mian Ph.D. (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2019, Electrical and Computer Engineering

Electric power grids are currently undergoing a major transition from large centralized power stations to distributed generation in which small and flexible facilities produce power closer to where it is needed. This move towards a decentralized delivery of energy is driven by a combination of economic, technological and environmental factors. In recent years, the cost of renewable energy in the form wind turbines and solar PV has dropped dramatically due to advances in manufacturing and material science, leading to their rapid deployment across the US. To supplement the intermittent nature of wind and solar energy, there is a growing need for small, highly controllable sources such as natural gas turbines. With the fracking boom in the US, there is currently abundant natural gas to use for this purpose. The resulting proliferation of many small energy producers creates technical problems such as voltage and frequency control that can be addressed with battery storage, whose cost is also dropping. These factors are leading to a move away from large energy production facilities that require too much initial investment. Also, a distributed supply is more efficient and reliable. The threat of global climate change is creating pressure to increase the integration of distributed generation and information technology is now capable of managing a greater number of energy producers, utilizing a vast supply of information to predict supplies and demand and to determine optimal dispatching of energy. The move towards a higher percentage of renewable energy creates many interesting technical issues, many of which are due to the lack of control over the renewable resources. Energy dispatching between multiple sources, some controllable and some not, and multiple loads leads to a need for dispatching strategies that maximize the percentage of the load that is met with renewable energy. A growing aspect of this energy dispatch is a stream of information about energy demand, w (open full item for complete abstract)

Committee: Malcolm Daniels Dr. (Advisor) Subjects: Electrical Engineering; Energy; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2019, Physics

Despite nearly forty years of investigation, the theoretical understanding of the nature of the quantum Hall transition remains largely inadequate in its explanatory power of the critical and universal behavior of the transition. The nonperturbative nature of the transition, along with the difficultly of theoretically handling disorder makes it one of the most challenging problems in condensed matter physics. Two of the best tools for investigating the quantum Hall transition are network models, such as the Chalker-Coddington (CC) network model, and supersymmetry (SUSY) to handle the disorder averages. Despite assuming a particular model for the disorder, necessary for a quantum Hall state to be achieved, namely weak smoothly varying disorder, the effective field theory obtained in the limit of large conductivity is the same nonlinear $\sigma$ model (NL$\sigma$M) that Pruisken derived for short ranged, Gaussian white noise disorder, implying some universality with respect to the model of disorder. Furthermore, the CC network model is easily modified to accommodate other types of quantum Hall effects, the spin and thermal Hall effects. In this thesis we will use the CC network and supersymmetry to derive the NL$\sigma$M for a variety of quantum Hall transitions. Chapter two takes a bit of a pedagogical approach to the standard CC model and subsequent derivation of the NL$\sigma$M using supersymmetry. Chapter three justifies the necessary changes to the CC model so that it can model the spin and thermal Hall effects. We then use supersymmetry to derive the NL$\sigma$M for the spin and thermal Hall effects. Finally, in chapter four we will look at a hybrid network that describes a standard Hall insulator in contact with a spin Hall insulator on the other side. Again, we will use SUSY to derive the NL$\sigma$M that describes the quantum Hall transition

Committee: Ilya Gruzberg (Advisor); Yuanming Lu (Committee Member); Chris Hirata (Committee Member); Lemberger Tom (Committee Member) Subjects: Physics

Master of Science in Mechanical Engineering (MSME), Wright State University, 2019, Mechanical Engineering

Usually power take off (PTO) with a two-spool turbofan engine has been accomplished via the high pressure (HP) shaft and bleed air from the high-pressure compressor (HPC). The PTO is used to run various aircraft components such as generators and hydraulic pumps, which also produce waste heat. To better understand the coupled transient nature of balancing engine thrust, power take off and thermal management, a transient variable cycle three stream turbofan engine model has been developed to investigate the integrated behavior. The model incorporates many dynamic features including a third-stream heat exchanger as a heat sink for thermal management and HP/LP shaft PTO. This paper describes a method of controlling HPC surge margin and maintaining the desired thrust while extracting power using both the HP and LP spools. The transient interactions as both PTO and 3rd stream heat rejection are simultaneously applied to the transient variable cycle engine model utilizing different control effectors were investigated. The rate of transient heat rejection was found to impact surge margin. Rapidly applied heat loads caused larger surge margin transients than heat loads applied more gradually despite the same maximum heat rejection. Optimal PTO profiles between the LP and HP shaft to minimize the amount of fuel used for a given PTO amount and flight envelope were also investigated. Finally, a notional mission was simulated with varying flight parameters and dynamic PTO based on optimal PTO profiles along with heat generation and afterburner. The controls were found to be sufficient to successfully run the mission however such simplified controls could induce numerical instabilities in certain mission profiles. This shows that while these simple controls are sufficient for these notional test runs more sophisticated controls will be necessary for a proper generic engine model.

Committee: Rory Roberts Ph.D. (Committee Chair); George Huang Ph.D. (Committee Member); Mitch Wolff Ph.D. (Committee Member) Subjects: Aerospace Engineering; Engineering; Mechanical Engineering; Systems Design

Master of Science, The Ohio State University, 2017, Mechanical Engineering

As fuel efficiency and emissions requirements continue to rise, auto manufacturers are continuously striving to adopt new technologies to help reach these goals. With methods such as turbocharging, direct fuel injection, variable valve actuation, and engine stop-start now common in mass production vehicles, the next step forward could be in waste heat recovery. In most vehicles today, more than 60 percent of fuel energy is lost to waste heat in the cooling system and exhaust. The higher temperature heat energy in the exhaust can be recovered using an Organic Rankine Cycle (ORC). Past research on ORC's focused on creating highly detailed models for performance prediction or controlling extremely simple models. Neither of these options are ideal for use in operating a real system. The detailed model is too slow and the controls based on the simple model are not accurate enough to predict what the real system will do. This thesis takes a highly detailed model and uses model order reduction to create a reduced order model which retains most of the prediction accuracy of the full model but is now smaller and faster. This new reduced model has been used with feedforward and feedback controls, but it also has the potential to be used in advanced model based controls such as model predictive control (MPC).

Committee: Marcello Canova Ph.D. (Advisor); Giorgio Rizzoni Ph.D. (Committee Member) Subjects: Mechanical Engineering

Master of Science, University of Akron, 2017, Electrical Engineering

With the advent of high power density motors in applications such as electric vehicles, the need for an effective thermal analysis of motors is further warranted to ensure their efficient and reliable operation. While existing Lumped Parameter Thermal Models (LPTMs) provide a convenient method for the thermal evaluation of motor designs, they provide a single, average temperature of the various regions of the motor without data on the temperature variation in the axial direction. LPTMs are a convenient reduced finite-element method to analyze the thermal performance of electric motors based on their design parameters and operating conditions. In this thesis the thermal analysis of a Permanent Magnet Assisted Synchronous Reluctance Motor (PMa-SynRM) is conducted by proposing two LPTMs: 1. Radial Lumped Parameter Thermal Model (R-LPTM). 2. Axial Lumped Parameter Thermal Model (A-LPTM). The R-LPTM adopts an existing approach considered for the thermal modeling of interior rotor configurations with the key contribution being the modeling of the unique rotor configuration of the PMa-SynRM under study. In this approach, the individual geometries of the motor are modeled as single nodes, the voltages of which correspond to the average temperature for the respective machine part. The A-LPTM introduces a novel thermal model by employing the Finite Volume Method (FVM). While the R-LPTM models heat flow only in the radial direction due to the lamination structure of the stator and the rotor regions, the extension of this approach to the axially thermally shorted conductor coil sides, the magnets and the shaft results in a relative oversimplication of the heat transfer in these regions. While equivalent lumped thermal resistances model axial heat flow in these regions in the R-LPTM, by employing the FVM in the A-LPTM a higher resolution of axial temperature data is determined by providing a more accurate method of radial and axial heat flow modeling in these re (open full item for complete abstract)

Committee: Seungdeog Choi (Advisor); Guo-Xiang Wang (Committee Member); Malik Elbuluk (Committee Member); Jin Kocsis (Committee Member) Subjects: Electrical Engineering

Master of Science in Mechanical Engineering (MSME), Wright State University, 2016, Mechanical Engineering

Many technological advances are expected to increase the capabilities of the future aircraft, both civilian and military. These improvements come in many forms such as new wing or fuselage shapes to improve lift or decrease drag. Other improvements are internal. One of these areas is the inclusion of advanced electronic systems for various roles. These changes affect a wide range of aircraft systems including, but not limited to avionics, power generation and thermal management. While these modifications promise to increase aircraft capabilities such as its range, payload or other key performance parameters, there are some significant drawbacks. One drawback is the thermal and power requirements needed to meet these needs. This problem will only be amplified by the addition of a High Energy Pulsed System (HEPS). This improvement, along with existing electronic systems that could be featured on next generation aircraft could cause a significant thermal load on an aircraft, where heat dissipation is already a problem. HEPS of this sort generate excessive amounts of heat during operation, creating an aircraft integration problem that might overwhelm the vehicles thermal management systems. Using the innovative solution of cryogenically cooling the HEPS, the proposed system would use Liquefied Natural Gas (LNG) as the system's primary coolant. In order to accomplish this, preliminary studies were carried out which indicated that the cryogenic cooling system for a HEPS could possibly be of a reasonable size for an aircraft application. Following this, detailed MatLab/Simulink models were made of the required cryogenic components so that they could be integrated into a T2T model to analyze the vehicle level effects of the LNG system. An initial aircraft integrated LNG HEPS system was designed and the results showed the HEPS was cooled and the rest of the aircraft also received a cooling effect. Further studies have enhanced that effect and attempted to accomplish the same (open full item for complete abstract)

Committee: Rory Roberts Ph.D. (Advisor); Mitch Wolff Ph.D. (Advisor); Ed Alyanak Ph.D. (Committee Member); Scott Thomas Ph.D. (Committee Member) Subjects: Aerospace Engineering; Engineering; Mechanical Engineering

Master of Science, The Ohio State University, 2014, Electrical and Computer Engineering

This thesis is concerned with issues observed with the variable frequency drive, VFD, traction inverter used in the Buckeye Bullet 3 as it performed during the 2013 race season and the work done to improve said drive for the 2014 season. The thesis will begin with an introduction to the Buckeye Bullet racing program discussing the history of the project as well as the goals for the current vehicle. From there, an overview of electric vehicle powertrains will discuss on-board energy storage, DC to AC energy conversion and the basic principals of permanent magnet electric motors. After the powertrain overview the paper will move into the details of the primary topic of research, the thermal dynamics of the solid state-devices used to create the VFD. This chapter will walk through the development of the thermal model as well as the algorithms used for balanced, three phase, DC to AC energy conversion. With a brief discussion one PWM comparator logic and modulating waveform shape, the chapter moves into the details of the Simulink model used and concludes with the result thereof. Topics considered less important than the thermal dynamics of the solid-state devices are grouped into a chapter of ”Secondary Drive Improvements”. These topics are Start Up Voltage Limit, Electromagnetic Noise, VFD Case Sealing, and finally a Motor Model. The thesis concludes with a summary of work and thoughts regarding future work that would benefit the Buckeye Bullet in years to come.

Committee: Giorgio Rizzoni (Advisor); Longya Xu (Committee Member) Subjects: Electrical Engineering

Master of Sciences, Case Western Reserve University, 2014, EMC - Mechanical Engineering

The thermal characteristics of microinverters on dual-axis trackers operating under real-world conditions were analyzed using a statistical analytical approach. 24 microinverters connected to 8 different brands of photovoltaic (PV) modules were analyzed from July through October 2013 at the Solar Durability and Lifetime Extension (SDLE) SunFarm at Case Western Reserve University (latitude 41.50, longitude -81.640). Exploratory data analysis shows that the microinverters’ temperature is strongly correlated with ambient temperature and PV module temperature, and moderately correlated with irradiance and AC power. Ambient temperature is the influencing factor under conditions of low irradiance in morning hours, when the irradiance is below 60W/m2. Noontime data analysis reveals that the microinverters thermal behavior is more strongly influenced by PV module temperature than AC power. Using a Euclidean distance measuring principle and average linkage criteria, a hierarchical clustering technique was also applied to noontime microinverter temperature data to group the similarly behaved microinverters. Microinverter temperature clustering shows that the clustering groups are more strongly influenced by PV module temperature than AC power. A linear regression model was developed to predict the temperature of the microinverters connected to different brands PV modules. The predictive model is a function of ambient temperature, PV module temperature, irradiance, AC power data, and the interaction between power, irradiance and module temperature. The difference between actual microinverter and predicted microinverter temperature lies between 0.40C to 1.60C at a 95% confidence interval.

Committee: Alexis Abramson (Committee Chair); Roger French (Committee Member); Joseph Prahl (Committee Member); Yifan Xu (Committee Member) Subjects: Mechanical Engineering

Master of Science (MS), Wright State University, 2009, Chemistry

The synthesis and characterization of hyperbranched poly(arylene ether)s with tailored degrees of branching has been explored via an A2+B3 approach. The reactivity of the individual electrophilic sites towards nucleophilic aromatic substitution, NAS, of the BB'B” monomers 4, 3', 5'-trifluorophenyl sulfone, 1 and 4, 3', 5'-trifluoro benzophenone, 2 were studied. The concentration, temperature and solvent conditions had an effect on the degree of branching, DB, in 1 and 2 and were probed via 13C and 19F NMR spectroscopy as well as a series of model reactions employing p-cresol 16, which acts as the nucleophile. Soluble, branched, poly (arylene ether)s, with controlled degrees of branching were prepared by performing the polycondensation reactions at higher temperatures with 1 leading to relatively higher DB values than 2. The glass transition, Tg and thermal stability of the soluble polymers increased as the degree of branching increased. Tg ranged from 126 °C to 177 °C, while 5% weight loss temperatures ranged from 372 °C to 514 °C under nitrogen and from 229 °C to 510 °C in air.

Committee: Eric Fossum PhD (Advisor); Kenneth Turnbull PhD (Committee Member); David Dolson PhD (Committee Member); Joseph F. Thomas, Jr. Phd (Other) Subjects: Chemistry

PhD, University of Cincinnati, 2009, Engineering : Mechanical Engineering

In order to reduce computational resources and time required for thermal design/analysis of large-scale systems, heat transfer processes in complex electronics packages need to be represented by suitably formulated simple models instead of conducting CFD (Computational Fluid Dynamics)-based analysis using detailed models. Relative to a detailed model, a simplified mathematical model for a complex electronics package offers many orders of reduction in computational resources. When used in a system-level environment, it is necessary that the simplified model accurately predict the thermal behavior for various local boundary conditions on the package. Therefore, it is important that these reduced-order models be boundary-condition-independent. An immediate need for accurate boundary-condition-independent (BCI) reduced-order models (ROM) exists in the area of thermal design and analysis of communication systems such as routers and switches. These systems use optical transceivers for data and tele-communication. These transceivers are sensitive to the surrounding temperatures, and their failure due to overheating results in down-time of the communication network. Heat transfer analysis of detailed models of these transceivers results in consumption of a large amount of computational resources, while analysis with geometrically-simplified models leads to inaccurate results. The current work identifies two methodologies for developing BCI ROMs for opto-electronic transceiver packages. The first methodology is the well-established DELPHI (DEvelopment of Libraries of PHysical models for an Integrated design) Methodology. In this method, the package is represented by a network of optimized thermal resistances. In the present study, the DELPHI Methodology is extended to develop BCI ROMs for an optical transceiver called Small Form-factor Pluggable package (SFP) which contains four heat-generating sources. A detailed CFD model of the SFP is developed and validated using natur (open full item for complete abstract)

Committee: Urmila Ghia PhD (Committee Chair); Karman Ghia PhD (Committee Member); Milind Jog PhD (Committee Member) Subjects: Engineering; Mathematics; Mechanical Engineering

MS, University of Cincinnati, 2006, Engineering : Mechanical Engineering

The thesis is broadly divided into three major parts. In the first part, thermal imaging is used to experimentally measure temperature and a numerical model is developed to predict the thermal heating of a sample exposed to 3rd generation synchrotron X-ray beams. In this study we have experimentally measured heating by the beam using infrared imaging and used these measurements along with a theoretical numerical model to help understand the heating process. Specifically, the temperature rise of 1mm and 2mm glass spheres (sample surrogates) exposed to an intense X-ray beam and cooled in a uniform flow of nitrogen gas at two different flow rates is modeled, analyzed, and experimentally tested in an actual synchrotron beam. The heat transfer including external convection and internal heat conduction, was theoretically modeled using computational fluid dynamics (CFD) to predict the temperature variation in the interior and on the surface of the sphere when subjected to the X-ray beam. In the next part a heated disk cooled in a uniform stream of air is numerically investigated. Finite Volume Method (FMV) is used to study the effect of orientation of disk and imposed boundary conditions on the local and average heat transfer coefficients. Also a Nusselt number (Nu) correlation is developed, in terms of Reynolds (Re) and Prandtl number (Pr), for predicting forced convective heat transfer over isothermal or isoflux circular disk geometry at low Reynolds numbers (Re) in the range 10 to 150.Three different orientations of the disk are studied, where the disk orientation with respect to the flow is: a) parallel; b) inclined at 45; c) normal. Finally, in the last part the biocrystal along with the mother liquor is modeled as a short cylinder (i.e. disk). Both local “spot” heating and full heating of the crystal are considered. Two analytical models are developed that depicts the temperature variation within the crystal. A 1-D analytical solution is developed by treating the sam (open full item for complete abstract)

Committee: Dr. Michael Kazmierczak (Advisor) Subjects: Engineering, Mechanical