氏名　Pattana Intani
学位の種類　博士（工学）
学位記番号　博甲第566号
学位授与の日付　平成22年12月31日
学位論文題目　Novel Concept of AC MHD Power Generation　（新たな交流MHD発電の概念）
論文審査委員
　主査　教授　原田　信弘
　副査　教授　大石　潔
　副査　教授　江　偉華
　副査　准教授　菊池　崇志
　副査　筑波大学・大学院システム情報工学研究科准教授　藤野　貴康

• 論文目次
• 論文要旨
• 論文審査の結果の要旨

［平成22（2010）年度博士論文題名一覧］ ［博士論文題名一覧］に戻る．

Contents
Title　Page
Abstract　p.I
Acknowledgements　p.III
List of Figures　p.VII
List of Tables　p.X
Chapter 1.　Introduction　p.1
　1.1　Principle of MHD Generation　p.2
　1.2　MHD System　p.3
　1.2.1　Open Cycle HMD System　p.3
　1.2.2　Closed Cycle MHD Generation　p.4
　1.2.3　Further Research of MHD generator　p.5
　1.2.4　Advantages of MHD Generation　p.6
　1.2.5　Conclusions　p.6
　1.3　Overview of Liquid Metal MHD Power MHD Systems　p.6
　1.3.1　The Separator Cycle　p.7
　1.3.2　The Two-phase Genetor Cycle　p.8
　1.3.3　Solar Applications　p.10
　1.3.4　Open-Cycle LMMHD　p.11
　1.3.5　The OMACON Cycle　p.12
　1.3.6　Conclusions　p.13
　1.4　Thesis Background　p.14
　1.5　Purposes of Thesis　p.15
　1.6　Scopes of Thesis　p.16
　References　p.18
Chapter 2.　Field Equations and Finite element Approximations　p.20
　2.1　Basic of an AC MHD Generations　p.21
　2.1　Theroy and Model of Consideration　p.22
　2.2.1　Analytical Formulation　p.22
　2.2.2　Finite Element Formulation　p.24
　2.3　Element Equation　p.25
　2.3.1　Higher-order Finite Elements　p.25
　2.3.2　Numerical Intgegration　p.26
　2.4　Calculation of Some Terms in Field Equation　p.27
　2.5　Power Flow in an AC MHD Generator　p.29
　References　p.31
Chapter 3.　Fundamental of an AC MHD Generation　p.32
　3.1　Introduction　p.33
　3.2　Model of Consideration　p.34
　3.3　Numerical Results and Discussions　p.35
　3.4　Conclusions　p.49
　References
Chapter 4.　An AC MHD Generation with a Double-sided Exciting Winding　p.51
　4.1　Introduction　p.52
　4.2　Model of Consideration　p.52
　4.3　Numerical Results and Discussions　p.53
　4.4　Conclusions　p.63
　References
Chapter 5.　Disk AC MHD Generation with a Single-sided Exciting Winding　p.65
　5.1　Introduction　p.66
　5.2　Model of Consideration　p.66
　5.3　Numerical Results and Discussions　p.68
　5.4　Conclusions　p.75
　References　p.76
Chapter 6.　Disk AC MHD Generation with a Double-sided Exciting Winding　p.77
　6.1　Introduction　p.78
　6.2　Model of Consideration　p.78
　6.3　Numerical Results and Discussions　p.80
　6.4　Conclusions　p.90
　References　p.91
Chapter 7.　Conclusions　p.92
7.1　Conclusions　p.93
　7.1.1　Linear AC MHD Generator　p.93
　7.1.2　Disk AC MHD Generator　p.95
7.2　Conparison of AC MHD with Conventional Generators　p.96
7.3　Limitations of an AC MHD generator　p.97

　The necessity of having an effective energy work is rapidly increasing alongside the implementation of energy technology. Finding an appropriate renewable energy has becoming increasingly important today’s. Furthermore, new technology that uses magnetrohydrodynamics （MHD）to generate the electrical energy has emerged. MHD generator was effectively utilize to generate electrical energy because of its simple structure and could directly convert thermal and/or kinetic energy into electrical energy. MHD generator can produce high power density with low environmental load to reduce the CO2 emission. However, conventional MHD generators have inherent disadvantages such requirement of inverter system in order to connect to the power grid and poor durability due to electrode erosion by arcing.

　From the above points of view, novel AC MHD power generation concept is proposed for directly generating an AC power without inverter system and with durable electrode system. This concept performs under the interaction between traveling magnetic field and motion of electrically conducting fluid. Performance and optimal operating point of the AC MHD generator have been studied numerically by using finite element method. Both linear- and disk-type configurations are examined with both single- and double-side exciting winging for each configuration. The working fluid acts as conductor flowing along the channel. The channel walls act as insulator to separate stator winding and working fluid. The stator winding was designed as the coils on top and bottom of the channel, produce traveling magnetic field by means of time harmonics function in the same direction with conducting fluid. The interactions between the conducting fluid and the traveling magnetic field were evaluated by Maxwell’s equations and Ohm’s law based on the method of finite-elements. Interactions between the traveling magnetic field and the conducting fluid were obtained by the distribution of a magnetic field in the channel based on the slip conditions. The performance of the generator was considered by the relationship of active power, reactive power, mechanical power, power dissipation and electrical efficiency as a function of the slip values. The optimal operating point of the generator was obtained by a maximum active power. Moreover, the maximum active power of the generator was varied by adjusting magnetic Reynolds number, electrical conductivity and height of the channel.

　The numerical simulations ensure the possibility to produce an AC power by a linear MHD generator with a single-sided exciting winding. The top and bottom stator winding were defined as exciting winding and inductive coil, respectively. The distribution of a magnetic field was deviated by the magnetic Reynolds number and slip values. The inductive magnetic flux density on the conducting surface depends on the magnetic Reynolds number. However, the maximum active power was reduced by increasing the magnetic Reynolds number and the slip value. The optimized value of active power is suggested with small slip value s<0. Reactive power was reduced by decreasing the slip value and increasing the magnetic Reynolds number. Mechanical power, power dissipation and electrical efficiency of the generator are functions of slip conditions in terms of 1-s, s and 1/（1-s）, respectively.

　In addition, performance of an AC MHD generator has been developed by using a double-sided exciting winding. The top and bottom stator winding generate traveling magnetic field, and serve as inductive coils at the same time. The stator windings were parallel with power supply and electrical load. Therefore, the electrical power from interaction between traveling magnetic fieldand conduction fluid are returned to electrical load by the top and bottom stator winding. The results were compared with a single-sided exciting winding. We found that reactive power of a double-sided exciting winding is lower than a single-sided exciting winding, should be compensatedby connecting capacitors at the input and output terminal. Furthermore, power density of the generator is higher than a single-sided exciting winding because exciting field was increased.

　The AC MHD concept has been applied to a disk channel with a single- and a double-sided excitingwinding. The numerical results show that the performance of a double-sided exciting winding is higher than a single-sided exciting winding. The optimized electrical conductivity for σ=5×10^5 S/m was used for application in slit channel and small magnetic Reynolds number.

　In conclusion, an AC MHD generator is an attractive concept. It can be operated at high temperatures. Moreover, it has no need inverters and electrodes. The generator has no moving mechanical parts, its design is not limited by the mechanical strength of rotating parts. The active power of an AC MHD generator can be increased by increasing fluid velocity. Furthermore, Numerical simulations have been conducted for investigating on optimum performance of the AC MHD generator by means of a single-and double-sided exciting winding. Configurations for a linear and a disk type under constant channel length and fluid velocity were studied. Disk type AC MHD generator showed a better performance compared with the linear one.

　本論文は、「Novel Concept of AC MHD Power Generation」（新たな交流MHD発電の概念）と題して、第7章から構成されている。

　第1章では、MHD発電機の原理と分類、液体金属を利用するMHD発電について述べ、さらに本研究の背景として、通常の電磁誘導を用いた回転発電機や通常の直流MHD発電機での問題点を指摘し、これまでの研究のレビューを行い、本研究の目的と位置付けを明確にしている。

　第2章では、研究対象としている交流MHD発電機の特性を知るための電磁界と導電性流体の運動に関する基礎方程式を提示し、数値解析手法として2次の有限要素法を適用することによって、精度高く磁気ベクトルポテンシャル、磁束密度、電力の流れが解析できることを述べている。

　第3章では、交流MHD発電の基本的な特性を把握するために、励磁電流と出力電流とを分離できる片側励磁交流MHDについて、その発電特性を解析している。その結果、発電チャネル近傍の磁気ベクトルポテンシャルと磁束密度の2次元分布を明らかにし、励磁電流を変化させることで出力電力を直接制御できること、また発電機の性能評価として重要な機械的パワー、パワー損失および電気変換効率が印加磁界の位相速度と作動流体速度とのスリップと磁気レイノルズ数によって表されることを明らかにしている。

　第4章では、高い発電性能が予想される両側励磁交流MHD発電機の性能解析を行っている。この発電機では、発電チャネル両側の固定子コイルが、下流に進行する磁界を印加すると共に、誘導負荷コイルとなって電気出力を取り出すことができる。両側励磁発電機内の現象を明らかにし、スリップに関して最適な動作点について考察し、これらの結果を片側励磁発電機の場合と比較して両側励磁発電機の特徴を明らかにしている。

　第5章では、ディスク形交流MHD発電機を提案し、その発電チャネル近傍の磁気ベクトルポテンシャルと磁束密度の2次元分布を明らかにし、さらにスリップに対するこの発電機の諸特性を明らかにしている。

　第6章では、両側励磁のディスク形交流MHD発電機の発電性能を解析し、出力有効電力がスリップに依存し、有効電力を最大にする最適スリップ条件があることを示している。さらにこの出力有効電力は作動流体の導電率、磁気レイノルズ数、および発電チャネル高さにも依存することを明らかにしている。

　第7章では、各章の結論を総括し、片側励磁と両側励磁発電機の特性および直線形とディスク形発電機の特性の相違を明らかにし、交流MHD発電機の応用可能性とその限界を示している。

　以上のように、本論文は電磁流体力学を基礎とした交流MHD発電機の基本的性質と発電性能を有限要素法による数値解析によって解析・考察し、高効率発電システムへの応用の可能性を明らかにした。よって、本論文は工学上及び工業上貢献するところが大きく、博士（工学）の学位論文として十分な価値を有するものと認める。