Variation of Dominant Instability Mode with Fuel Configuration in an Inverted Coaxial Injector

Abstract

We explore the steady and unsteady flame properties of a coaxial jet flame in a moderate pressure combustor with a single shear coaxial injector. Significant flame structure modifications are observed in H2/O2 and CH4/O2 flames at fuel lean conditions over a range of pressure conditions varying from near-atmospheric to about 8 atm. The different stages of flame evolution in H2/O2 flames correspond very well with the different phases of pressure cycles. CH4/O2 flames have a different structure and evolution process as compared to that of H2/O2 flames and also exhibit higher instability limits. The critical equivalence ratio, separating steady and unsteady operation, increases with increase in pressure.