Three-dimensional modeling of the instantaneous temperature distribution in a turbulent flame using a multidirectional interferometer

We have reconstructed a three-dimensional instantaneous temperature distribution inside the turbulent flame of a propane-air premix burner using multidirectional holographic interferograms by constructing a geometric model of the three-dimensional isothermal surfaces, and have read out the temperature values. To reconstruct this asymmetric temperature field, interference fringe data were acquired using an eight-directional Twyman-Green interferometer surrounding the object flame, and all data were simultaneously acquired. A ruby laser was used to obtain clear fringe patterns. The temperature distribution was reconstructed from the refractive index distribution, obtained from the fringe patterns, by a computed tomography technique using a convolution reconstruction algorithm. Isothermal profiles were calculated in horizontal cross sections from the temperature data. All of the multiple isotherms in each horizontal section were approximated with polygons and then stacked vertically to form polyhedra in a solid model format, having side facets with the corresponding isothermal values. Models, not only of the initial isothermal solids, but also of the solids resulting from multiple Boolean operations on them, were reconstructed to show the distribution in detail. This development will be of help in studying the local instantaneous structure of turbulent flames. (c) 2007 Society of Photo-Optical Instrumentation Engineers.