Improvement of Flame Complex Permittivity Model Considering Positive Ions and Electrons

The complex permittivity of flame includes relative permittivity and conductivity, which is an important electrical characteristic parameter to reflect the information of combustion process. The complex permittivity of flame can be measured by electrical capacitance tomography (ECT) and electrical probe. In this paper, the motion of positive ions and electrons in the electric field are both considered, and the expression of the flame complex permittivity under the effect of positive ions and electrons is derived. The numerical values of the flame relative permittivity and conductivity without ions and with ions are obtained by theoretical calculation at different frequency. The relative permittivity and conductivity of the flame at flame core area and outer flame area were measured by the electric probe method. The experimental results verify the rationality of the new flame complex permittivity expression. The study in this paper can provide a theoretical basis for flame ECT detection.