Turbulent Premixed LPG/air Flames Structures in Double Swirl Burner

In practical gas turbine combustors, swirlers are used for enhancing the flame stabilization by recirculating the hot gas with fresh air-fuel mixture. Moreover the double swirl arrangement in combustor enables more mixing and stratification compared to single stage swirl. Therefore it is crucial to observe the flame structures for different geometrical and operating conditions. The current study focuses on the flame structures and interactions generated by various swirler configurations. A double swirl-stabilized bluff body burner was used in this experimental study, and swirlers with low (S = 0.45) and medium (S = 0.89) swirl numbers were employed to observe the varied flame structures. The bluff body configuration which stabilizes the flame by anchoring, also used along with swirlers. To qualitatively evaluate flame shape and heat release rate, the simultaneous OH* and CH* chemiluminescence measurements technique was used and time averaged direct photographic images and Abel-inversion of OH*/CH* chemiluminescence images were presented. Initially, the pilot and main flames were examined separately in order to gain better understanding of their behaviour. In second set of experiments the pilot flame with only air at outer flow and main flame with only air at inner flow, are studied to understand the mixing dynamics of pilot and main flame. The pilot and main flames individually stabilized with the two shear layers and the flame structures for both the flames changes drastically for different operating and geometrical conditions. Finally, one premixed flame with the same equivalence ratio at both the inner and outer, as well as one stratified flame with distinct equivalence ratios at both the inner and outer are investigated. © 2022, American Institute of Aeronautics and Astronautics Inc.. All rights reserved