Ion-current fluctuations recorded with a cylindrical electrostatic probe passing premixed flames

Abstract

The ion-current fluctuation recorded with a cylindrical, electrostatic probe traversing a premixed flame has been studied. The experiments were performed by moving the probe across a rectangular or circular-nozzle burner flame. Effects of the ion-denesity distribution on the ion-current fluctuation were estimated by analyzing the phenomena near the probe on the basis of the continuum probe theory, and the deviation of the ion current was shown to increase with the ion-density gradient. By comparing the maximum ion currents to the probe traversing the flame in different directions, the deviation was found to decrease with increasing probe velocity. It was estimated to be less than 15% if the probe was used in the range of probe velocities higher than 3 m/sec. An analysis was made for inferring the ion-current fluctuations to be recorded with the probe being passed through flames of known configuration. The results showed that the ion-current fluctuation of an inclined or curved flame could be inferred fairly well on the basis of the fluctuation derived from a plane flame parallel to the probe axis.