Stability of slag in turbulent MHD boundary layers
Slag formation on MHD channel walls from the direct combustion of coal has proven to be an asset to channel performance and duration. Over hot electrode walls, the slag forms a thin, viscous liquid layer, driven by pressure and shear forces generated in the gas boundary layer. At a given location in the channel, the slag thickness obviously depends upon the balance between rate of slag deposition and rate of slag removal. Deposition normally occurs from the vapor phase and liquid drops of slag mixed in the gas stream, produced in the combustion chamber. Slag removal occurs through liquid layer flow and in addition, through vaporization and entrainment. Wettability, or surface bonding, is also critical for slag layer formation on the electrode and insulator surfaces. The ability to predict, quantitatively, the rate of slag removal caused by one or more of these mechanisms will enable the designer to estimate slag replenishment rates necessary to maintain the required protective layer over the electrodes. Stickler and DeSaro have analyzed the slag replenishment problem with emphasis on deposition rates and flow transport processes. Pressure and shear instabilities at the slag-gas interface are studied to determine whether slag entrainment does occur as a result of these instabilities. Extensive information concerning the stability of liquid layers in subsonic and supersonic turbulent gas streams was obtained and is applied to the slag-boundary layer phenomena. It is shown that entrainment does occur for subsonic flows but that the slag layer is stable in supersonic flows.
- Research Organization:
- Sandia Labs., Albuquerque, N.Mex. (USA)
- DOE Contract Number:
- EY-76-C-04-0789 r
- OSTI ID:
- 7364537
- Report Number(s):
- SAND-76-5021
- Country of Publication:
- United States
- Language:
- English
Similar Records
Stability of slag in turbulent MHD boundary layers
Numerical codes for MHD flows. Quarterly technical progress report, October--December 1976