Laboratory-scale burner seeded with potassium for calibration of potassium emission/absorption instruments

摘要

In magnetohydrodynamic (MHD) power systems, potassium may be used to enhance the electrical conductivity of the high temperature products of combustion. In order to better evaluate the performance of MHD generators, it is desirable to be able to measure the distribution of the electrical conductivity of the gases throughout the channel through which the hot gases are passing. One such system is based on the emission/absorption spectra of potassium as a function of temperature. Diagnostic instruments, based on the emission/absorption characteristics of potassium in a flame or plasma require calibration in known temperature and potassium concentration conditions. A laboratory-scale hydrogen/oxygen burner which is seeded with gaseous potassium has been designed, fabricated, and operated for the purpose of providing a calibration facility for the potassium emission/absorption spectrographic (PE/AS) instrument. A nickel block was machined appropriately to provide separate flows of oxygen, hydrogen, and potassium vapor in a hot nitrogen stream mixed with hydrogen. A potassium evaporator was designed and fabricated to allow hot nitrogen gas to bubble through hot molten potassium to provide a known mass fraction of potassium to the resultant flame. The vapor pressure variation of the potassium with temperature was used to predict the amount of potassium carried to the flame by assuming that the hot nitrogen stream resulted in a saturated mixture as it bubbled through the heated molten potassium. Operational aspects as well as safety considerations in the operation of this burner are described. 10 refs., 1 fig.