Coil systems for measuring electrical conductivity in MHD combustion flows. Final report
An instrument system for measuring electrical conductivity, sigma, was tested in a copper-walled magnetohydrodynamic (MHD) combustion duct at Stanford University; these tests were preceded by simulation tests at Utah State University in an electrolyte-filled aluminum duct. The system consisted of an immersible two-coil, magnetic-induction probe, a pneumatically actuated traversing apparatus, provision for gas cooling, and signal conditioning and readout devices. Operation of the probe was based on the fact that sinusoidal power supplied to the primary coil created a magnetic dipole field that induced eddy currents in the surrounding medium; the sigma-dependent eddy-current magnitudes were detected and measured by the probe's secondary sensing coil. After the influence of nearby highly conducting walls (10/sup 6/mho/m) was essentially eliminated, the system could measure sigma(approximately 10 mho/m) in electrolytes with a maximum error of 10%. However, the tests in a seeded MHD combustion flow at Stanford were not successfully completed due to complexities associated with the cooling and traversing apparatus and due to funding and facility-scheduling priorities. Consequently, in an effort to simplify the measurement technique, a theoretical study was made of an instrument having the primary and secondary sensing coils embedded in an insulator wall adjacent to the conducting fluid. A two-coil system was tested using a uniformly conducting electrolyte and the disagreement between theory and experiment was less than 15%. The theory predicts that extra sensing coils can be used to obtain a conductivity profile. Although it has not yet been tested in an MHD flow, the wall-mounted coil system is attractive because coil cooling would be simplified, traversing would be unnecessary, the technique is non-intrusive, and the measurement readout would be continuous.
- Research Organization:
- Utah State Univ., Logan (USA). Dept. of Mechanical Engineering
- OSTI ID:
- 5073162
- Report Number(s):
- EPRI-AF-569
- Country of Publication:
- United States
- Language:
- English
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