Effect of an electric field on the nitrogen oxide emission and structure of a laminar propane diffusion flame

Abstract

The effect of an electric field E on the structure and nitrogen oxide NOx emission of an individual laminar propane diffusion flame is experimentally investigated. The current-voltage characteristics of the flame, its deformation, the fuel-air ratio and the NOx emission are determined for positive and negative burner polarities. A reduction in NOx emission (up to 30% with respect to the emission index) is demonstrated in the case of negative burner polarity. A cause-and-effect relationship between the processes in the flame is proposed: the presence in the flame of positively charged ions and soot particles; the motion of the ions in the E field and the onset of an induced electrohydrodynamic flow directed towards the negatively charged burner; the retention and increase in the concentration of soot particles in the lower region of the flame, which leads to an increase in soot particle radiation and hence to a decrease in the temperature of the flame front and a corresponding reduction in NOx emission. The electrohydrodynamic aspects of the problem are subjected to a qualitative analysis.