On turbulent burning velocities of V-shaped turbulent premixed flames with circular fractal turbulence generators

Abstract

The characteristics of turbulent burning velocities of V-shaped turbulent flames are experimentally investigated by varying the shape parameters of cross- and square-type circular fractal turbulence generators (FTG). For both type FTGs, the thickness reduction ratio, Rt, of 0.4, 0.6, 0.8, and 1.0, and the blockage ratios, σ, of 30 and 50% are used. The characteristics of non-reacting turbulent flows such as the mean flow velocity, U¯, velocity fluctuation, u′, and integral length scale, L, are measured using a hot-wire anemometer while the progress variable of reacting flows is evaluated using OH-PLIF images. The turbulent premixed flames are distributed in the Borghi-Peters diagram from the wrinkled flamelet regime to the thin reaction zone regime, depending on the shape parameters of the FTG. The local displacement speed, ST,LD, and the local consumption speed, ST,LC, are evaluated using the measured data of turbulent reacting and non-reacting flows. ST,LD and ST,LC are found to increase with increasing σ and decreasing Rt, and hence, the averaged ST,LD, and ST,LC can be expressed as a function of u′/SL and/or L/δL. Correlations between ST or u′ and the FTG shape parameters (Rt and σ) are also proposed, which can be used to control and predict ST and u′ for fundamental studies and industrial applications.