热离子转换器中添加氧的研究
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摘要
添加并控制电极间隙内氧的含量对提高热离子转换器(TIC)的能量转换效率和功率密度具有关键作用,因此本文针对TIC中氧的不同添加途径及其对转换性能的影响进行系统研究。吸附氧后的电极在吸附Cs后的功函数较单吸附Cs更低,从而提高了TIC的输出功率密度和转换效率。TIC中氧的添加途径主要有两种:一是利用蒸气源添加,即直接将氧或氧化物以气态的形式添加至电极间隙内;二是利用接收极添加,即通过释放接收极上氧化物的氧或活性过渡金属材料内溶解的氧为电极间隙内供氧。对比分析认为,采用活性金属作为接收极能得到性能更优异、可靠性更高、寿命更长的TIC,因此选择或设计一种新型的接收极材料可作为含氧TIC的一个发展方向。
The addition and control of oxygen content in electrode gap plays a key role in improving the energy conversion efficiency and power density of thermionic converter(TIC). Therefore, the different methods to add oxygen, as well as their effects on the output performance of TIC were systematically investigated. The work function of the electrodes that co-adsorbed oxygen and cesium is lower than that only adsorbed cesium, thus the output power density and conversion efficiency would be improved. There are mainly two ways to supply oxygen to TIC. One is to add oxygen or oxides directly into the electrode gap in the form of vapor phase by using steam source. Another is to provide oxygen by releasing it from oxide or oxygen-sensitive metal of the collector. By the comparison, it can be concluded that the TIC with oxygen-sensitive metal collectors has better performance with high reliability and long service lifetime. Therefore, selecting or designing a special material for collectors is considered to be a development direction of oxygenated TIC.
The addition and control of oxygen content in electrode gap plays a key role in improving the energy conversion efficiency and power density of thermionic converter(TIC). Therefore, the different methods to add oxygen, as well as their effects on the output performance of TIC were systematically investigated. The work function of the electrodes that co-adsorbed oxygen and cesium is lower than that only adsorbed cesium, thus the output power density and conversion efficiency would be improved. There are mainly two ways to supply oxygen to TIC. One is to add oxygen or oxides directly into the electrode gap in the form of vapor phase by using steam source. Another is to provide oxygen by releasing it from oxide or oxygen-sensitive metal of the collector. By the comparison, it can be concluded that the TIC with oxygen-sensitive metal collectors has better performance with high reliability and long service lifetime. Therefore, selecting or designing a special material for collectors is considered to be a development direction of oxygenated TIC.
引文
[1] EL-GENK M S, MOMOZAKI Y. An experimental investigation of the performance of a thermionic converter with planar molybdenum electrodes for low temperature applications[J]. Energy Conversion and Management, 2002, 43: 911-936.
[2] PARAMONOV D V, EL-GENK M S. Effect of oxygen on the operation of a single-cell thermionic fuel element[J]. Journal of Nuclear Materials, 1998, 256: 218-228.
[3] DESPLAT J L, HATCH G L, RASOR N S. Oxygen dispenser for thermionics[J]. Energy Conversion Engineering Conference, 1990, 2: 316-321.
[4] LEVINE J D, GELHAUS F E. Oxygen as a beneficial additive in cesium thermionic energy converters[J]. Journal of Applied Physics, 1967, 38(2): 892-893.
[5] KOBYAKOV V P. Effectiveness of the use of oxygen-containing niobium in thermionic energy converters[J]. Technical Physics, 1998, 43(8): 997-1 003.
[6] KOBYAKOV V P, KALANDARISHVILI A G. Increase in the power of arc cesium-oxygen thermionic converters with tungsten electrodes at elevated emitter temperatures[J]. Technical Physics, 2003, 48(2): 199-204.
[7] KOBYAKOV V P, KALANDARISHVILI A G. Performance of thermionic energy converters with oxygen-containing emitter and collector[J]. Technical Physics, 2004, 49(6): 775-778.
[8] UEBBING J J, JAMES L W. Behavior of cesium oxide as a low work-function coating[J]. Journal of Applied Physics, 1970, 41(11): 4 505-4 516.
[9] CHEN J M. Mechanism of work-function reduction by oxygen adsorption[J]. Journal of Applied Physics, 1970, 41(12): 5 008-5 011.
[10] DESPLAT J. Evaluation of oxygen-dispensing collectors for thermionics[J]. Space Technology & Application International Forum, 1999, 458: 1 452-1,457.
[11] DESPLAT J L. Recent developments in oxygenated thermionic converters[J]. Functionally Graded Materials, 1996: 639-646.
[12] GELLER C B, MURRAY C S, RILEY D R, et al. Final report of the high efficiency thermionics (HET-Ⅳ) and converter advancement (CAP) programs[R]. Pittsburgh, PA: Westinghouse Bettis, 1995.
[13] FUKUDA R, KASUGA Y, KATO K, et al. Development of the oxygenated thermionic energy converters utilizing the sputtered metal oxides as a collector[J]. Space Technology & Application International Forum, 1999, 458: 1 444-1 451.
[14] FUKUDA R, KASUGA Y, KATOH K. Development of refractory metal oxide collector materials and their thermionic converter performance[J]. Functionally Graded Materials, 1997: 647-654.
[15] YARYGIN V I. Electrode materials for thermionic converters for different types of power systems[D]. Obninsk: Physics and Power-Engineering Institute, 1999.
[16] YARYGIN V I, SIDELNIKOV V N, MIRONOV V S. Energy conversion options for NASA’s space nuclear power systems initiative-underestimated capability of thermionics[M]. Rhode Island: American Institute of Aeronautics and Astronautics, 2004: 1-9.
[17] YARYGIN D V, MIRONOV V S, SOLOV′EV N P, et al. High-output thermionic converter based on a metal-oxygen system on the collector[J]. Atomic Energy, 2000, 89(1): 546-554.
[2] PARAMONOV D V, EL-GENK M S. Effect of oxygen on the operation of a single-cell thermionic fuel element[J]. Journal of Nuclear Materials, 1998, 256: 218-228.
[3] DESPLAT J L, HATCH G L, RASOR N S. Oxygen dispenser for thermionics[J]. Energy Conversion Engineering Conference, 1990, 2: 316-321.
[4] LEVINE J D, GELHAUS F E. Oxygen as a beneficial additive in cesium thermionic energy converters[J]. Journal of Applied Physics, 1967, 38(2): 892-893.
[5] KOBYAKOV V P. Effectiveness of the use of oxygen-containing niobium in thermionic energy converters[J]. Technical Physics, 1998, 43(8): 997-1 003.
[6] KOBYAKOV V P, KALANDARISHVILI A G. Increase in the power of arc cesium-oxygen thermionic converters with tungsten electrodes at elevated emitter temperatures[J]. Technical Physics, 2003, 48(2): 199-204.
[7] KOBYAKOV V P, KALANDARISHVILI A G. Performance of thermionic energy converters with oxygen-containing emitter and collector[J]. Technical Physics, 2004, 49(6): 775-778.
[8] UEBBING J J, JAMES L W. Behavior of cesium oxide as a low work-function coating[J]. Journal of Applied Physics, 1970, 41(11): 4 505-4 516.
[9] CHEN J M. Mechanism of work-function reduction by oxygen adsorption[J]. Journal of Applied Physics, 1970, 41(12): 5 008-5 011.
[10] DESPLAT J. Evaluation of oxygen-dispensing collectors for thermionics[J]. Space Technology & Application International Forum, 1999, 458: 1 452-1,457.
[11] DESPLAT J L. Recent developments in oxygenated thermionic converters[J]. Functionally Graded Materials, 1996: 639-646.
[12] GELLER C B, MURRAY C S, RILEY D R, et al. Final report of the high efficiency thermionics (HET-Ⅳ) and converter advancement (CAP) programs[R]. Pittsburgh, PA: Westinghouse Bettis, 1995.
[13] FUKUDA R, KASUGA Y, KATO K, et al. Development of the oxygenated thermionic energy converters utilizing the sputtered metal oxides as a collector[J]. Space Technology & Application International Forum, 1999, 458: 1 444-1 451.
[14] FUKUDA R, KASUGA Y, KATOH K. Development of refractory metal oxide collector materials and their thermionic converter performance[J]. Functionally Graded Materials, 1997: 647-654.
[15] YARYGIN V I. Electrode materials for thermionic converters for different types of power systems[D]. Obninsk: Physics and Power-Engineering Institute, 1999.
[16] YARYGIN V I, SIDELNIKOV V N, MIRONOV V S. Energy conversion options for NASA’s space nuclear power systems initiative-underestimated capability of thermionics[M]. Rhode Island: American Institute of Aeronautics and Astronautics, 2004: 1-9.
[17] YARYGIN D V, MIRONOV V S, SOLOV′EV N P, et al. High-output thermionic converter based on a metal-oxygen system on the collector[J]. Atomic Energy, 2000, 89(1): 546-554.