Flame Stability and Characterization of Swirl-Stabilized Flames. Annual Report January 1, 1987-December 31, 1987

摘要

The objectives of the program are to (i) characterize liftoff, flame blowout limits and other properties of swirl stabilized flames, (ii) to identify the underlying physical mechanism governing blowout, and (iii) to incorporate this understanding into useful models and scaling relations to improve gas burners. Using a well-controlled swirl stabilized flame experiment, laser velocimetry, laser sheet flow visualization, and laser Rayleigh scattering diagnostics were used. Fuel-air mixing was visualized and a simple scaling analysis explained why swirl shortens the flame by a factor of five. The analysis explains four trends that were measured. Effects of burner size sealing, Reynolds number and swirl were explained. Three swirl flame blowout limits were identified; comparison with bluff body flames is in progress. The blowout limits of coflowing jet flames were quantified in a joint effort with Sandia Labs, showing that even small coflow velocities have large effects on flame blowout. A theoretical formulation explains the measurements. Results of a 'flip' experiment demonstrate the validity of the present approach. A 3 D digital imaging method has been developed to visualize the blowout process.