Abstract

Traveling-wave thermoacoustic electric generators convert heat energy into acoustic power and then into electrical power. In this work, a toroidal-topology traveling-wave thermoacoustic electric generator is developed. It consists of a traveling-wave thermoacoustic engine, two linear alternators connected in parallel, and sets of variable resistive/capacitive electric loads, in conjunction with accessories and instrumentation required for experimental investigation. The prototype is investigated mostly experimentally, with some theoretical and DeltaEC insights. The main variables are measured, namely the operating frequency of the complete system, the dynamic pressure, the hot side temperatures, the input/output voltages and currents, and the piston stroke. Then, different performance indices are estimated from these measurements, such as the gas parcels oscillating velocity, the different conversion efficiencies, the acoustic and electric output powers. Sustainable operation is achieved over a range of external resistive/capacitive loads at different imposed hot-side temperature, mean gas pressure, and heating rate. Three possible regions of operation are identified: a no-wave region, an operation region, and an over-stroke region. The results identify the two main efficiencies related to the transport of different powers, namely: the thermal-to-acoustic conversion efficiency and the acoustic-to-electric conversion efficiency. The individual factors that control each of them are identified and summarized. The results indicate how the mean gas pressure and the hot-side temperature affect the different key performance indices. For example, the mean gas pressure strongly affects the operating frequency that affects the acoustic matching between the engine and the alternator. Increasing the hot-side temperature improves the thermal-to-acoustic efficiency and extends the operating region into larger regions. The acoustic-to-electric conversion efficiency is controlled solely by the alternator parameter, the resistive/capacitive load combination and the operating frequency. It is observed that the range where the required onset temperature is low corresponds to operation at a large stroke but low current, leading to low electric power output. The study shows that the alternator can produce more current at smaller strokes by increasing the ratio between the Ohmic-to-mechanical-motion loss, which itself depends on the external load and the operating frequency. Two-dimensional contour plots of measured and estimated variables are plotted in the resistive/capacitive load domain in the operating regime, where they quantify the need for acoustic impedance matching for the startup of operation. Theoretical simulations on the performance of the linear alternator at specific strokes and frequencies are examined and compared to the experimental results. DeltaEC simulations are carried out and compared to the experimental measurements. The experimental and DeltaEC results show how different operating variables affect the TAE’s acoustic impedance output, the LA’s acoustic impedance input, and the acoustic impedance matching between them. This thesis identifies and summarizes the different mechanical, acoustic, and electric matching requirements in these devices that are required to either lower the required onset temperature, allow operation in a wide range of electric loads, maximize power output, or overall conversion efficiency. Conflicts between some of these factors are identified, and some practical solutions are suggested. Finally, the main lessons learned during TWTEG’s development are presented.

School

School of Sciences and Engineering

Department

Mechanical Engineering Department

Degree Name

MS in Mechanical Engineering

Graduation Date

Summer 9-6-2020

Submission Date

9-6-2020

First Advisor

Abdel-Rahman, Ehab

Committee Member 1

Abdel-Rahman, Ehab

Committee Member 2

Serag Eldin, Mohamed Amr

Committee Member 3

Essawey, Abdelmaged Hafez Ibrahim

Extent

369 p.

Document Type

Master's Thesis

Rights

The American University in Cairo grants authors of theses and dissertations a maximum embargo period of two years from the date of submission, upon request. After the embargo elapses, these documents are made available publicly. If you are the author of this thesis or dissertation, and would like to request an exceptional extension of the embargo period, please write to thesisadmin@aucegypt.edu

Institutional Review Board (IRB) Approval

Not necessary for this item

Comments

The main accomplishment and achievement of this work is to "design, integrate, build, operate, and investigate the first Traveling-Wave Thermoacoustic Electric Generator developed in Egypt". This could have not been completed without continuous support from many contributors. Mainly, all my advisors, Prof. Ehab Abdel-Rahman, Prof. Mohamed Amr Serag Eldin, and Dr. Abdelmaged H. Ibrahim Essawey provided continuous ongoing help, support, advice, and supervision during all the work steps of this strategic research project. Prof. Ehab Abdel-Rahman is a crucial person for such a successful project; his powerful support and management brings the best outcomes from available academic and financial resources. He is always able to find the most practical solutions to complex issues, even under the most challenging situations. I am proud to work under his supervision for several years since I joined the thermoacoustic research team at AUC. I am very thankful to Prof. Mohamed Amr Serag Eldin for his support and guidance. He always provides valuable and in-depth advice, which is critical in this multi-disciplinary research project. Dr. Abdelmaged is a role-model person and advisor. He dedicated most of his life to science, teaching and research activities. He continuously provides each member in the thermoacoustic research team with professional advice that promotes knowledge, experiences, skills, and values. His day-to-day supervision of this research work and technical direction of the thermoacoustic research team at AUC is very much appreciated. Moreover, I am thankful to Prof. Steven Garrett, Prof. Gregory W. Swift, Prof. Osama F.M. ElBahar, Prof. Doaa Khalil, and Prof. Helene Bailliet, as well as to Phillip Spoor, John Corey, and Gordon Reid from RIX Industries (previously Chart Industries/Q Drive) for their useful insights and valuable guidance. We communicated with each of them several times, and we received precious guidance and technical advice. Exceptional thanks are due towards current and previous team members: Dr. Islam Ramadan, Dr. Amr Taha, Eng. Mohamed Elhawary, Eng. Omar Ismail and Eng. Mohamed Ramadan for their continuous help and support during different phases of this research project. The support Dr. Islam Ramadan provided to DeltaEC simulations and debugging of the developed prototype was essential and critical. The help Eng. Omar provided with the data analysis part is very much appreciated. I am grateful to Eng. Sherif Hussein, who assisted in the designing, implementation, and debugging of many electric circuits used in the power electronics of the developed prototype. Eng. Abdel-Rahman Nassief assisted in building some of the electric circuits employed. Mr. Hany Mosaad provided significant assistance in all software employed in this work, including LabVIEW, Matlab, and Maple. This publication has been produced with the partial financial assistance of the European Union. The contents of this document are the sole responsibility of the authors and can under no circumstances be regarded as reflecting the position of the European Union. Partial funding to several aspects of this project at different times and phases was provided by the graduate studies department in the AUC and by the Academy of Scientific Research and Technology. Most of the components were manufactured in the workshop of the mechanical department in the AUC. I am sincerely grateful to Eng. Mohamed Bakr, the technical manager of the workshop, for his great support during different manufacturing processes. My thanks are extended to Eng. Abdullah Awad, the technical manager of Technology for Engineering and Industry, for manufacturing some critical parts in the developed prototype. Last but not least, from my sole heart and feelings, I am sincerely grateful to my family. Exceptional dedications are not enough to express my emotion towards my mother, Amina, especially for all the time she prays for me. Together, I cannot forget my father, Ali, may ALLAH have mercy on him, who passed away in 2012. My parents were my primary educators during my childhood, teenage, and youth years. Finally, I am grateful to the sincerity of my wife, Sally, for her continuous unrestrained support. She always pushes me toward better achievements. She still charges me with positive and beloved emotions.

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