A new approach to the correlation of turbulent burning velocity data

TLDR: In this article, a new approach to the correlation of turbulent burning velocity data is presented, which basically stems from the fact that detailed measurements of turbulence, using wire meshes and perforated discs as generators of isotropic turbulence, show a unique trend when the ratio of Kolmogorov microscale η to lateral macroscale L is plotted against the r.m.s.

Abstract: The present investigation highlights a new approach to the correlation of turbulent burning velocity data, which basically stems from the fact that detailed measurements of turbulence, using wire meshes and perforated discs as generators of isotropic turbulence, show a unique trend when the ratio of Kolmogorov microscale η to lateral macroscale L is plotted against the r.m.s. turbulent velocity u ′. For weak turbulence, the data obtained for different generators telescoped into a single curve, whereas for strong turbulence distinct demarcations could be detected for different grids. This cardinal finding was further pursued apropos of turbulent burning velocity data. Systematic measurements were carried out in cold flows using a hot-wire anemometer and a real time wave analyzer from which the requisite intensity and scales of turbulence were deduced. Subsequently burning velocity data for methane-air mixtures burning in an open burner were obtained by analyzing densitometrically the direct photographs of flames. Analysis reveals that two correlations are adequate for interpreting the data obtained. When turbulence intensity is low, the ratio of turbulent to laminar burning velocity S T /S L depends only on η/L in much the same fashion as u ′/S L while for large intensities, u ′/S L turns out to be an additional parameter besides η/L. When this analysis is extended to the data of other investigators, the forms of the correlating equations remain the same as in the present work but require different empirical constants. To sum up, it may be said that for weak turbulence η/L alone is adequate as a correlating parameter, while for strong turbulence both u ′/S L and η/L must be considered.