POTASSIUM D-LINE BLUE WING ABSORPTION-COEFFICIENT UNDER COMBUSTION-FIRED MAGNETOHYDRODYNAMIC CONDITIONS

A model is proposed for the adsorption 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 diam 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 730-760 nm region well with a power-law exponent of -1.07 matched to the Voigt at 764.6 nm. Using this model, emission absorption measurements on coal-fired MHD flows with diameters of 33 and 76 cm 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.