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Abstract
Thermal characteristics of coswirling flames with various axial and angular inlet momentum distributions are investigated in this experimental study. The heat loading, the Reynolds number, and the overall equivalence ratio were held constant while the swirl and flow distribution were systematically varied between the two air jets. Turbulent temperatures were measured with a fine-wire thermocouple in the recirculation zone, shear mixing, and postcombustion regions. A digital compensation technique was used to increase the maximum thermocouple frequency limit from approximately 50 Hz to over 1.5 kHz. The total swirl number and the total equivalence ratio were insufficient in characterizing thermal effects in these flames. Additional governing parameters are presented, which more accurately describe behavior in coannular burners. These parameters account for the swirl number in each jet, the relative jet strength, and the local stoichiometry at the inlet of the burner.
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This work is supported by the Carderock Divison of the Naval Surface Warfare Center, the South Carolina Energy Research and Development Center, and the University of Maryland. Special appreciation is given to Dr. Horace Russell for his initiative and encouragement. The authors would also like to acknowledge Drs. Robert Kiang and Earl Quandt for fruitful discussions, and Messrs. Richard Metrey and Richard Messalle and Dr. Stuart Jessup for their support.