Measurements and Analysis of Alternating Flow Patterns in a Multinozzle Combustor

Abstract

In some cases, a multinozzle combustor may exhibit flowfields in which individual nozzles hold two distinct flow or flame shapes in an alternating pattern. This study presents flowfield measurements for nonreacting and reacting flows in a rectangular combustor with two adjacent swirl-stabilizing nozzles at varying internozzle spacing. During tests of the wider nozzle spacings, with a reacting flow fueled by propane, there are differences between the flows of the two nozzles. Planar laser-induced fluorescence of the OH molecule (OH PLIF) shows that the flame remains anchored in the shear layer. Thus, the flame from one nozzle penetrates into the combustor, whereas the other flame is anchored close to, and almost parallel with, the dome wall. When the fuel is changed to methane, the asymmetry between the two nozzles is removed; therefore, the combustion properties, in addition to nozzle design, have an effect on the presence of this alternating flow pattern. A hypothesis based on turbulent opposed jets is presented to explain this change in the flowfields. When the nozzle design, flow, or combustion characteristics cause the shear layers of the adjacent nozzles to become sufficiently opposite in direction, the two flows can no longer mix. Instead, one shear layer goes underneath the other, which results in the differing flow features of the adjacent nozzles.