Comprehensive optical diagnostics for flame behavior and soot emission response to a non-equilibrium plasma

Abstract

This study reported comprehensive optical diagnostics for flame behavior and soot emission under directly coupling of the plasma with the flame at specific heights. The morphometric parameters of unstable flames under the direct plasma coupling were quantified. We also proposed an optical method to eliminate plasma luminescence from the field of view to extract flame intensity. At the same discharge height, with the increase of discharge frequency, the flame height decreased, while the flame horizontal extension distance and deflection angle increased. The relationships between flame morphologic and electrical parameters were obtained. The experimental results suggested a one-to-one correspondence between plasma action and flame deflection or shortening. When the plasma interacted with the flame, the overall temperature and soot emission of the flame decreased compared with that without plasma. At the same discharge height, the flame temperature and soot decreased further with the increase of discharge frequency. The soot emission changed more remarkably with the discharge frequency for higher discharge heights. With the increase of voltage, the flame temperature and soot increased at the lower discharge heights. The analysis of the experiment data demonstrated that the variation of soot emission was caused by the cooperation of multiple factors.