VELOCITY AND SCALAR CHARACTERISTICS OF PREMIXED TURBULENT FLAMES STABILIZED BY WEAK SWIRL

Velocity and scalar statistics of premixed flames stabilized in a novel weak-swirl burner have been studied under a broad range of mixture and turbulence conditions. The nonreacting flows are also investigated to determine the influence of weak-swirl on isotropic turbulence. Deduced from the data are the flame speeds, combustion induced flow acceleration, flame generated turbulence, and flame crossing frequencies. They are compared with previous results obtained in other flame configurations. Three series of experiments are conducted to investigate the evolution of velocity statistics with decreasing equivalence ratios. Under very lean conditions (phi = 0.6), the velocity profiles have no characteristic features and are not very different from the corresponding nonreacting profiles. An indicator parameter, K-T, derived from fundamental mixture and flow properties is developed to estimate the relative influences of the turbulence stretch and the mean aerodynamic stretch on combustion induced flow acceleration. The analysis shows that intense turbulence and bulk stretch (i.e., large values of K-T) can obscure and counteract the dynamic effects of combustion.