Hybrid algorithm for three-dimensional flame chemiluminescence tomography based on imaging overexposure compensation

Abstract

Flame tomography of chemiluminescence is a necessary combustion diagnostic technique that provides instantaneous 3D information on flame structure and excited species concentrations. During combustion diagnostics, imaging overexposure always causes missing information, which obviously decreases the accuracy in further reconstructions. In order to compensate imaging overexposure, a hybrid algorithm combining weight correction and Tikhonov's regularization is proposed in this paper. The intensity of the overexposure region can be estimated via the accumulation of weight coefficients. Meanwhile, Tikhonov's regularization is utilized to ameliorate the quality of reconstruction. The numerical simulation quantitatively evaluates the performance of the hybrid algorithm. Additionally, an experiment system consisting of 12 cameras was established to reconstruct the 3D combustion structure of axisymmetric flame with different exposure time settings. This work further investigates dynamic nonaxisymmetric propane diffusion flame. The obtained results show that the hybrid algorithm can effectively reveal the flame structure less influenced by imaging overexposure and achieve better results.

Arbitrary position 3D tomography for practical application in combustion diagnostics

“…Work has previously been done looking into tomographic reconstructions with a restricted field of view [25] and overexposure compensation [26]. In cases where optical access has to be achieved in practical apparatus, the geometry would rarely allow for the in-plane-half-circle camera arrangements that has been used in most previous experimental measurements or mirror arrangements using dual or quad scopes [10,27].…”