Investigation of flame-generated turbulence in premixed flames at low and high burning velocities

Abstract

Knowledge of the dependence of turbulent flame velocity on such parameters as fuel properties, turbulent fluctuations, and length scales is of central importance for industrial applications such as combustion in motors, gas turbine combustors, and domestic burners. Two unanswered questions concern how aerodynamic turbulence influence the reaction and/or flame speed and how the reaction intensity influences the aerodynamic turbulence values. The reaction velocity has been measured in a stagnation point flame, the turbulence intensities and length scales before and after the flame front being recorded by an LDV system. Laminar burning velocity was varied by using different concentrations of methane-hydrogen-air mixtures. The results show under certain conditions an immense increase in turbulent fluctuations in and after the flame front, measured using conditioned and unconditioned LDV techniques. These measurements indicate that turbulence is produced in the flame front, the extent of turbulence depending on the incoming laminar burning velocity, which was varied over a comparatively wide range. Some results are illustrated by tomographic pictures, which clearly show the increase of turbulence and turbulent flame front structure in dependence on laminar burning velocity.