An Experimental Evaluation of the BLM Model of the Scalar Field in Turbulent Premixed Flames

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Abstract
An experimental evaluation of the BLM model of the scalar field in premixed turbulent flames is presented. Experimental measurements of probability density functions (pdfs) of the flame passage times, autocorrelations and spectra were made in open V-shaped and stagnation point flames by monitoring the Mie scattering of the laser beam by a dense oil aerosol which evaporates on passage through a flame front. These results are compared with predictions derived from the model using two a priori pdfs: the exponential and gamma two distributions. The product pdfs are self-similar and well described by the gamma two distribution. The reactant pdfs are also self-similar but are better represented by the exponential distribution except at small passage times. Comparisons between experimental and theoretical autocorrelations show the gamma two predictions to be more successful. The modeling of the low fequency region of the scalar spectra is also improved. Calculations of the integral time scale based on measured crossing frequencies using the gamma two model lead to significantly improved agreement with experimental values. The predicted distribution of the integral time scale, however, is in conflict with the experimental results. The two flame geometries give substantially the same results.