Characterization of Nonpremixed Turbulent Bluff-Body Burner Flames. Annual Report, January-December 1990

摘要

Sampling probe species concentration measurements in unconfined bluff-body stabilized flames showed that Blockage Ratio (BR) did not increase the NOx emissions. However, at high BR, confinement increased NOx emissions by a factor of two. CH/CH4 imaging data in unconfined and confined bluff-body flames were obtained. It was shown that the flame regime responds to the recirculation zone fuel concentration. The knowledge was used to predict the flame regime map. CH/CH4 data along with previous Mie scattering results show that the extended stability of the confined flame is due to the presence of a wall recirculation zone. High-resolution imaging measurements of CH in a lifted, turbulent-jet flame showed that the reaction zone consists of high CH regions separated by lower CH regions. These observations are consistent with the distributed reaction zone model. The axisymmetric vortex dynamic model was completed, validated and applied to a ten-to-one diameter ratio bluff-body. Results showed that the flow has significant large-scale vortex shedding at velocity ratios from .67 to .8, and has vortex shedding interspaced with lull periods above this velocity ratio. This behavior will have implications relative to flame stability, turndown and emissions.