An Investigation of Flame Stability in a Coaxial Combustor
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING
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An investigation of the flame stability of a coaxial dump combustor was made. A 6.0 inch diameter combustor was studied, and the inlet diameter was varied from 2.5 inch to 5.0 inch. Tests were carried out using pre-mixed ethyleneair and JP-4air. The inlet temperature levels were generally in the range 1000-1250 R the corresponding pressure was varied between approximately 10 and 40 psia. Inlet Mach numbers were typically in the range 0.2 to 0.9. The flame stability data were not collapsed by a conventional correlation. A new correlation parameter was derived by modelling the annular recirculation zone as an adiabatic stirred reactor using a one-step chemical reaction this parameter gave successful correlations. The dominant variable in flame stability was the inlet temperature. The effect of velocity on the lean limit was small. Some tests were performed with additional fuel injection directly into the recirculation zone, which yielded an estimate of the air mass flow fraction entrained into the recirculation zone. Finally, tests were performed using a transparent combustor it was observed that the combustion process was an oscillatory phenomenon. A review of the literature concerning the flame stability and aerodynamics of coaxial combustors is presented.
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