Potassium D-line 'blue' wing absorption coefficient under combustion-fired MHD conditions

A model is proposed for the absorption coefficient of the far 'blue' wing of the potassium D-line under combustion-fired magnetohydrodynamic (MHD) conditions. Such a model is important because of the need to measure potassium seed atom densities on large-scale MHD facilities. The model was developed using experimental emission profiles on a 20 cm diameter oil-fired, simulated MHD flow. A two parameter model, constructed of a sum of power laws matched to a Voigt profile in the near blue wing, fits the 730 to 760 nm region well with a power law exponent of -1.07 matched to the Voigt at 764.6 nm. Emission absorption measurements on coal-fired MHD flows with diameters of 33 and 76 cm using this model compared well to chemical equilibrium calculation predictions. The model should allow accurate measurements of seed atom density irrespective of the flow dimensions and geometry using two wavelength wing emission absorption measurements, a technique suitable for real-time monitoring. Such measurements should then provide a useful indirect measure of the electron density which is a critical parameter for analyzing MHD power generation.