Measurement of Three-Dimensional Temperature Field of Flickering Premixed Flame with and without Coflow

Abstract

The three-dimensional (3D) temperature field of the flickering flame with and without coflow can be measured using the flame reaction technique combined with tomographic reconstruction. This combined experimental technique facilitates the non-intrusive measurement of the unsteady 3D temperature field of a premixed methane/air flame. The target flame visualization, which was achieved by the flame reaction of sodium in the supplied mists of sodium chloride solution and line-of-sight intensity images of the flame, was transformed into the temperature field using calibration with the sodium D-line reversal method combined with imaging from six CCD cameras located around the flame. The uncertainty in tomographic temperature measurement was confirmed for the steady axisymmetric flame under the influence of strong coflow. Tomographic temperature measurements were applied to the flickering flame with and without coflow, and the results were analyzed using proper orthogonal decomposition (POD) to understand the unsteady behavior of the temperature field of the flickering flame. The flickering energy was found to be dominant in the first two POD modes. Flame flickering with and without coflow was found to be dominant in the axisymmetric and non-axisymmetric modes, respectively. The characteristics of the flickering flame with and without coflow are discussed in this paper, based on spectrum analysis. The results suggest that the structure of the flickering flame is highly modified by the presence of even a small magnitude of coflow.