Revised Calderon Method of Annular ECT for Imaging Flashback Flame of a Bluff-Body Burner

In this article, an annular electrical capacitance tomography (ECT) sensor was designed, and a revised Calderon image reconstruction method was proposed for monitoring the flashback flame of a bluff-body burner. The central support of the bluff-body was used as the internal electrode of the sensor, and the external electrode array was fixed on the outer surface of the burner. The capacitance values of all pairs of electrodes, including the internal and external, composed a boundary capacitance matrix of the annular sensing field. The revised Calderon method was compared with the commonly used sensitivity matrix-based methods including the linear back projection (LBP) and Landweber methods for imaging the cross-sectional distribution of permittivity which is continuous in value. Simulation results show that the revised Calderon method is of higher image reconstruction quality than the LBP and Landweber methods. In the experiment, the designed annular ECT sensor and revised Calderon method were used to monitor the flame flashback phenomenon of the bluff-body burner. The experiment results not only monitored the occurrence of flame flashback, revealed the variations of flame flashback intensity and time with the fuel:air equivalent ratio, but also determined the boundary condition of flame flashback of the bluff-body burner. The proposed method provides a new approach for experimental study on the influencing factors of flame flashback, and thus can be applied to research on combustion stability and high-performance burner design.