Influence of soot self-absorption on simultaneous 3D temperature and soot volume fraction measurements in turbulent flames

Optical investigations of turbulent sooting flames present multiple challenges, one of which is soot self-absorption (SSA), where part of the radiation signal is absorbed by the flame itself before reaching the detector. The present paper adapts an approach from the literature applied to a laminar axisymmetric flame to correct effects of SSA in a turbulent non-axisymmetric flame using a commercially available tomographic reconstruction algorithm. As a proof of concept, the method is first applied to a flame phantom with a soot volume fraction distribution similar to a typical laminar diffusion flame. Neglecting SSA resulted in overestimation of soot volume fraction and underestimation of temperature, consistent with findings from other researchers. The trend was also observed in the turbulent flame. However, especially for the soot volume fraction, local effects due to the complex geometry and high gradients of soot concentration and temperature can result in errors on the order of 30% and higher. Thus, it is crucial to consider SSA effects in turbulent flames with high local soot concentrations, which can be effectively addressed through the proposed approach.