Study on the electrical response of small ethanol‐air diffusion flame under the uniform electric field

Abstract

Ethanol is a renewable alternative fuel in many application areas. The external electric field is applied to assist the small ethanol diffusion flame in this study. The electrical response of flame under the uniform electric field is discussed. A reduced chemical mechanism of ethanol is used to establish a numerical model corresponding to the experimental system. The characteristics of current-electric field strength, equivalent resistance, distribution of charged species, velocity field, and reaction rate are studied. The results show that the electric field brings significant effects on the combustion and electrical characteristics of flame. As the electric field strength increases, the current through the circuit and the equivalent resistance of the flame show a three-stage variation. The current increases first (0-40 kV/m), then stabilizes (40-70 kV/m) and then continues to increase (70-100 kV/m) with the increase of the electric field strength. It shows that the flame has certain electric resistance characteristic. The number density of charged species in the flame increases, and the distributions of charged species tend to move upstream by the effect of electric field. When the electric field strength is high as 100 kV/m, the charged species density increases by 10%. Meantime, the gas velocity near the flame front is accelerated and the chemical reaction rate also increases by the effect of electric field. When the electric field strength reaches 100 kV/m, the corresponding reaction rate and the corresponding flow velocity are increased by about 40% and 20%, respectively, compared with those without electric field. The calculated ionic wind velocity increases greatly with the electric field strength and shows a nearly linear increasing trend. The combined effects of the enhanced ionic wind effect, the intensified chemi-ionization process, and the increase of the concentration of charged species are considered as the main reason for the effect of electric field.