Mixing efficiency estimation by probe discharge spectroscopy

Abstract

Summary form is given. This work considers the dynamics of long filamentary pulse discharge generated along the contact zone of two co-flown gases [1], basically: hydrocarbon fuel and oxidizer. The effect of the mixing actuation in compressible flow is observed because of the gas dynamic instability arisen after the discharge generation. The mixing efficiency is examined qualitatively by means of Probe Discharge Breakdown Spectroscopy. An adequate measurement of the mixing efficiency is principally important for this study. The best way for that is to know the concentrations of main components and their spatial distribution. The idea is to realize breakdown of the so-called “probe” discharge that has much less power than the main one at some delay after the main breakdown and to analyze the spectrum of this probe discharge. The temporal resolution of this method is equal to the duration of probe discharge luminescence - <; 1 us - it is reasonably small. The spatial resolution is determined by the collecting optical system and can be no more than lxd=3x1mm. It is a little bit worse than spatial resolution of the LBF [2] method but it still seems satisfactory for mixing efficiency estimation. Spectroscopic observations were carried out by means of high luminosity monochromator combined with ANDOR DU420 spectroscopic camera. Dispersion of this system is 0.5 Å/pixel and spectral resolution is about 2.5 Å. Spectrum of the main discharge (E1=1.5J) contains high intensity continuous emission that arises due to high temperature within the main discharge channel. Power release in probe discharge is measured as low as E2=0.03J per pulse. Probe discharge spectrum was measured at variation of the delay time between main and probe discharge and the probe discharge location. It was found that spectrum of the probe discharge doesn't contain CN at all without preceding breakdown of the main discharge. If main discharge isapplied for mixing, the CN emission arises in spectrum of the probe discharge. Its intensity grows with growth of the probe discharge delay that means increasing of the CO2 concentration. It is also seen that intensity of the N2 bands tends to reduce, when disturbances reach the measurements region.