Engineering Commons^™

Durability Enhancement Of Anion Exchange Membrane Based Fuel Cells (Aemfcs) And Water Electrolyzers (Aemels) By Understanding Degradation Mechanisms, Noor Ui Hassan

Theses and Dissertations

The past several years have seen remarkable progress in renewable energy sources such as solar and wind, showing excellent efficiency and significant cost reduction. The intermittent nature of renewable resources requires them to be integrated with energy storage systems that can hold or convert this excess energy into other forms. Though batteries have been the most popular, it is also possible to store the energy as chemicals and fuels, such as hydrogen (H₂). Hydrogen generation from water electrolysis has been receiving significant attention in recent years. Among the existing water electrolysis technologies, anion exchange membrane electrolyzers (AEMELs) are …

A Multi Physics Integrated Solution For A High-Pressure Stage Turbine Efficiency And Durability, Sanjay Chopra

Theses and Dissertations

World electricity demand is projected to grow at an annual rate of ~ 2.1% to year 2040₁. EIA projects nearly 50% increase in world energy usage by 2050 led by growth in Asia.[28];[29]. It is predicted that the global electricity demand grows at approximately 1.6 % per year from approximately 2008 and forecasted to approximately 2035, twice the rate of primary energy demand. This raises electricity's usage in total final energy consumption from approximately 19% in 2018 to approximately 24% in 2040. Electricity demand growth is set to be particularly strong in developing economies. .[28];[29];[38] As an enabler, to meet …

Analysis Of Distortion Transfer And Generation Through A Fan And A Compressor Using Full-Annulus Unsteady Rans And Harmonic Balance Approaches, Daniel Robert Soderquist

Theses and Dissertations

Understanding distortion transfer and generation through fan and compressor blade rows is able to assist in blade design and performance prediction. Using full annulus unsteady RANS simulations, the effects of distortion as it passes through the rotor of a transonic fan at five radial locations (10%, 30%, 50%, 70%, and 90% span) are analyzed. The inlet distortion profile is a 90-degree sector with a 15% total pressure deficit. Fourier distortion descriptors are used in this study to quantitatively describe distortion transfer and generation. Results are presented and compared for three operating points (near-stall, design, and choke). These results are used …

Suitability Of The Kalina Cycle For Power Conversion From Pressurized Water Reactors, Jack Ryan Webster

Theses and Dissertations

The primary objective of this work is to determine the Kalina cycle's suitability for thermal power conversion from a pressurized water reactor. Several previous papers have examined this application, but these either lack proof of concept or make unfeasible assumptions. This work expands current knowledge by simulating the Kalina cycle and comparing it to current pressurized water reactor Rankine cycles in order to identify which is more efficient. Prerequisite to the modeling is a simulation tool capable of modeling the thermodynamics of ammonia/water mixtures. Instead of using an existing program, a new one called Clearwater is used. This tool is …

Mitigating Transients And Azeotropes During Natural Gas Processing, Edris Ebrahimzadeh

Theses and Dissertations

Cryogenic carbon capture process can be used to efficiently eliminate CO2 emissions from fossil-fueled power plants. The energy-storing embodiment of cryogenic carbon capture (ES-CCC) integrates energy storage with cryogenic carbon capture and uses natural gas as a refrigerant. ES-CCC captures CO2 from slowly varying or steady-state sources even as it absorbs and replaces large amounts of energy on the grid for energy storage. These large transients occur in the LNG generation as the process moves through energy storing to energy recovery operations. Additionally, raw natural gas often includes CO2 that forms an azeotrope with ethane. Breaking this azeotrope and separating …

Efficiency Evaluation Of A Magnetically Driven Multiple Disk Centrifugal Blood Pump, Kayla H. Moody

Theses and Dissertations

Heart failure is expected to ail over 8 million people in America by 2030 leaving many in need of cardiac replacement. To accommodate this large volume of people, ventricular assist devices (VADs) are necessary to provide mechanical circulatory support. Current VADs exhibit issues such as thrombosis and hemolysis caused by large local pressure drops and turbulent flow within the pump. Multiple disk centrifugal pumps (MDCPs) use shearing and centrifugal forces to produce laminar flow patterns and eliminate large pressure drops within the pump which greatly reduce risks that are in current VADs. The MDCP has a shaft drive system (SDS) …

Bus Route Operational Efficiency Evaluation In Milwaukee County, Ebtesam Hazbavi

Theses and Dissertations

ABSTRACT

BUS ROUTE OPERATIONAL EFFICIENCY EVALUATION IN MILWAUKEE COUNTY

by

Ebtesam Hazbavi

The University of Wisconsin-Milwaukee, 2015

Under the Supervision of Professor Yue Liu

Public transit systems are expanding in the majority of cities in the United States due to the increasing numbers of people who use public transportation as their main commute facility. Evaluating the efficiency of public transit systems results in providing better services for the residents on one hand and reduces the unnecessary costs on the other hand.

In this research, the efficiencies of bus routes options in County are evaluated. After reviewing different literature, Fuzzy AHP …

Design And Comparison Of Si-Based And Sic-Based Three-Phase Pv Inverters, Wei Fu

Theses and Dissertations

The opportunities for both power density and efficiency improvements of photovoltaic (PV) inverter have come with the development of commercially available wide bandgap (WBG) devices such as Gallium Nitride (GaN), and Silicon Carbide (SiC).

In this thesis, how the replacement of Silicon (Si) Insulated Gate Bipolar Transistor (IGBT), with SiC Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) affects the power density and efficiency of a solar inverter implementation is presented. The focus is on achieving a minimum volume of the output filter which meet the current harmonic performance of IEEE standard, while meeting the thermal constraint of the semiconductor device. Efficiency improvements …

Quantum Efficiency Enhancement For Gan Based Light-Emitting Diodes And Vertical Cavity Surface-Emitting Lasers, Fan Zhang

Theses and Dissertations

This thesis explores the improvement of quantum efficiencies for InGaN/GaN heterostructures and their applications in light-emitting diodes (LEDs) and vertical cavity surface-emitting lasers (VCSELs). Different growth approaches and structural designs were investigated to identify and address the major factors limiting the efficiency. (1) Hot electron overflow and asymmetrical electron/hole injection were found to be the dominant reasons for efficiency degradation in nitride LEDs at high injection; (2) delta p-doped InGaN quantum barriers were employed to improve hole concentration inside the active region and therefore improve hole injection without sacrificing the layer quality; (3) InGaN active regions based on InGaN multiple …

Thermodynamic Kinetics And Efficiency Analysis Of Methyl Viologen, Chang Chen

Theses and Dissertations

Methyl Viologen (MV) is an electron mediator that has great possibilities to be used with an electrode system in which the electrode system provides electrons towards reducing MV species. MV has three redox states and they can be converted to each other via redox reactions on the surface of the electrode. The concentration of the three species of MV was related to the voltage potential applied to the system through a thermodynamic model. With the thermodynamic model the concentration of the three species can be predicted with different applied voltage potentials towards providing guidance for controlling the redox state of …

Growth And Characterization Of Non-Polar Gan Materials And Investigation Of Efficiency Droop In Ingan Light Emitting Diodes, Xianfeng Ni

Theses and Dissertations

General lighting with InGaN light emitting diodes (LEDs) as light sources is of particular interest in terms of energy savings and related environmental benefits due to high lighting efficiency, long lifetime, and Hg-free nature. Incandescent and fluorescent light sources are used for general lighting almost everywhere. But their lighting efficiency is very limited: only 20-30 lm/W for incandescent lighting bulb, approximately 100 lm/W for fluorescent lighting. State-of-the-art InGaN LEDs with a luminous efficacy of over 200 lm/W at room temperature have been reported. However, the goal of replacing the incandescent and fluorescent lights with InGaN LEDs is still elusive since …

Payback Information: It's Effect On Home Buyers Regarding Energy Efficiency, Steven E. Sparti

Theses and Dissertations

This study was conducted to find out how payback analysis would affect consumer decision making with regards to home energy efficient upgrade packages. Three different home plans were obtained from a local builder and seven different energy efficient packages were created. Using Hot2000 the heating and cooling loads were calculated for each building, with each energy efficient package, in each of the four major cardinal directions. The averages were taken and the payback information was calculated. The payback information included the increased cost of the package, the increase in the mortgage payment, the annual savings from heating and cooling bills, …

A Computational Study Of Axial Compressor Rotor Casing Treatments And Stator Land Seals, Charles C. Cates

Theses and Dissertations

As fuel prices soar ever higher, aircraft manufacturers and their airline customers demand that the next generation of engines used on their aircraft push the limits of efficiency and capability. This study consists of a computational examination of two currently accepted methods of axial compressor performance improvement in terms of surge margin and efficiency, rotor casing treatments and stator land seals.ADPAC and Fluent CFD solvers were used in the analysis of circumferential groove casing treatments and two types of stator seals, one typical of a front stage stator and one typical of a rear stage stator. The computational solutions and …

Optimizing The Efficiency Of A Multi-Stage Axial-Flow Compressor: An Application Of Stage-Wise Optimization, Shawn A. Miller

Theses and Dissertations

The development of jet engines has become an integral part of maintaining air superiority. In order to achieve the most advanced engine, research has turned to traditional optimization methods to aid in creating new engine designs. To develop simplified mathematical models representative of the engine, the engine can be separated into its components. A jet engine has three major elements, the compressor, combustion chamber and turbine. This research attempts to make an initial analysis of a two stage compressor to determine values of blade angles and spacing to chord ratios for both stages that produce the highest possible efficiency for …