Measurements of secondary flow in an MHD channel with inlet swirl using echo planar imaging
The measurement of the secondary flow distribution in a Magneto-hydrodynamic (MHD) channel is very important for understanding the characteristic of the power generator. However, the measurement of that was difficult using other conventional technique. Therefore, the authors studied the adaptability of Echo Planar Imaging(EPI) of which the measurement time is the shortest in Magnetic Resonance Imaging(MRI) through the numerical analysis. The secondary flow with a swirl of 5MWth MHD channel in Hokkaido University was analyzed. The MR signal is measured as an induced electromotive force caused by the magnetization. When Flow Encoding Pulse (FEP) is applied, phase shift {Delta}{phi} proportional to the velocity is obtained. In the flow velocity measurement in the cross section, the relationship is shown with {Delta}{phi}={alpha}v{sub y} + {beta}v{sub z}, where {alpha} and {beta} are constants determined by FEP, and v{sub y} and v{sub z} are the y and z component of velocity, respectively. The flow velocity distribution in the cross section can be measured by changing values of {alpha} and {beta}, and measuring the MR signal twice. When the MHD flow is measured by EPI, the most important affect is MHD induced magnetic field. Therefore, the MHD induced magnetic field, the flow velocity distribution, and other values were evaluated by using the 3-D MHD computer code developed by the Argonne National Laboratory, Illinois, USA. The numerical phantom was set from these values, and the measurement of the flow velocity distribution by EPI was analyzed. It was assumed that white noise which is the amount of 5% of MR signal's variance acted as a transmission system noise. Dynamic range of the A/D converter was assumed to be 12bit. All data acquisition times were 1.5ms. The average error of an analytical result was 13.1%. It was confirmed that the error by the MHD induced magnetic field did not greatly affect, and the EPI is very powerful tool to measure a secondary flow.
- Research Organization:
- Hokkaido Univ., Sapporo (JP)
- OSTI ID:
- 20000338
- 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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