Dual-Modality Electrical Tomography for Flame Monitoring

Electrical capacitance tomography has been widely used in flame monitoring. In this paper, a dual-modality electrical tomography system was developed for imaging of flame admittivity distribution, including conductivity and permittivity distributions. An admittance measuring circuit was developed to obtain both resistance and capacitance of the flame impedance, and a Calderon method-based reconstruction algorithm was developed, which could be used to directly reconstruct the cross-sectional images of both conductivity and permittivity in the flame. The 2-D and 3-D phantoms were modeled in simulation to validate the feasibility of the developed system and algorithm. Experiments were carried out to monitor a Bunsen burner flame with varied air flow rates. Both simulation and experimental results were confirmed that the developed technique has not only reconstructed the cross-sectional distribution of admittivity in the flame but also revealed variations in flame admittivity with height. In addition, it was discovered that the conductivity and permittivity distributions in the flame were affected by the air flow rates. Therefore, the system can be used to monitor the conductivity and permittivity distributions in the flame and, hence, can further help study the combustion mechanism.