EXPERIMENTAL-STUDY OF THE MEAN REACTION-RATES IN A TURBULENT PREMIXEDFLAME

A detailed experimental study of a turbulent premixed flame above a Bu nsen burner is presented. First the mean velocity field and the turbul ence field within the flame have been studied by L.D.A., including mea surements of turbulent length scales. Secondly the flame is studied wi th quantitative planar imaging. These images lead to the knowledge of the mean and fluctuating progress variable, as well as length scales o f the fluctuating held and the ''flamelet length by unit surface area' '. The experimental results are discussed with respect to already exis ting measurements and theories. For the present turbulent flame, which can be classified as a ''wrinkled flame'' throughout most of the flow held, there is found a clear but slight influence of combustion on th e turbulence kinetic energy. As determined from experiments the turbul ent length scale increases when crossing the flame. The measurements o f flamelet length by unit surface area has enabled us to directly obta in the mean reaction rate, because the local flamelet velocity has bee n 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.