Experimental study of the mean reaction rates in a turbulent premixed flame

Abstract

Abstract—A detailed experimental study of a turbulent premixed flame above a Bunsen burner is presented. First the mean velocity field and the turbulence field within the flame have been studied by L.D.A., including measurements of turbulent length scales. Secondly the flame is studied with quantitative planar imaging. These images lead to the knowledge of the mean and fluctuating progress variable, as well as length scales of the fluctuating field and the "flamelet length by unit surface area". The experimental results are discussed with respect to already existing measurements and theories. For the present turbulent flame, which can be classified as a "wrinkled flame" throughout most of the flow field, there is found a clear but slight influence of combustion on the turbulence kinetic energy. As determined from experiments the turbulent length scale increases when crossing the flame. The measurements of flamelet length by unit surface area has enabled us to directly obtain the mean reaction rate, because the local flamelet velocity has been found, in the mean, close to the laminar burning velocity within ± 5%. Existing models for calculating the mean reaction rate have been compared with these measurements, and it is found that the Eddy Break Up Model, or the Cant and Bray Model are in agreement, nearly equally well, with the experimental findings.