Studies on a self-excited closed cycle MHD generator for pulse power system
The authors have been proposing to use a closed cycle disk MHD generator as an alternative of an open cycle linear generator for applications to portable pulsed power supply because of its special advantages of durability and reliability. Steady state operation with applied magnetic field mode, magnet coil design and dynamic behavior of a disk type MHD generator in self-excited mode were studied numerically. One-dimensional numerical code based on MacCormack method were used. Thermal input to the disk channel was 40MW and working medium was argon seeded with potassium driven by the nonequilibrium plasma generator. At first, steady state solutions were obtained for both initial applied field of 0.7T and for full magnetic field 4T. For any load conditions examined, generator behaved quite stable and output current reaches its certain final value. Based on these steady state output current, they successfully designed suitable magnet coils. Current density was about 15A/mm{sup 2} . This value was quite reasonable and durable even for relatively long duration. With the designed magnet coils, dynamic behavior of the disk generator was studied. For transition from initial applied field mode to self-excited mode, switching was succeeded and there was no abnormal fluctuations in current trace. Noticeable instability did not develop in this period. However, in self-excited mode, the output current significantly increases and becomes much higher than the rated current of 1720A at B=4T after time=4sec., in spite of the fact that the output current increases steadily and very smoothly until that time. Sudden development of ionization instability was suggested from distributions of electron temperature and number density. They tried to limit excitation current to the magnet coils exactly to the designed value using bypass circuit to prevent from development of ionization instability. Then stable operation in the self-excited mode was successfully achieved. Further the authors confirmed the stable operation in SE mode without additional control when the value of initial applied field was increased to 4T. Further, if its value was higher than 2.5T, output current stably increased up to the designed value and converged to the designed operating conditions. Such a behavior was not completely clarified so far and they need to study further that how to reach and/or how to design stable operation in SE mode.
- Research Organization:
- Nagaoka Univ. of Technology (JP)
- OSTI ID:
- 20000325
- Resource Relation:
- Conference: 33rd Intersociety Energy Conversion Engineering Conference, Colorado Springs, CO (US), 08/02/1998--08/06/1998; Other Information: 1 CD-ROM. Operating system required: Windows 3.x; Windows95/NT; Macintosh; UNIX. All systems need 2X CD-ROM drive., PBD: 1998; Related Information: In: Proceedings of the 33. intersociety energy conversion engineering conference, by Anghaie, S. [ed.], [2800] pages.
- Country of Publication:
- United States
- Language:
- English
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