Abstract
This paper studies the effect of internozzle spacing on the lean blow-off of a linear combustor array. The combustor’s lean operability limit did not have a monotonic relationship with internozzle spacing; the configuration with the intermediate nozzle spacing was the most stable. Simultaneous multi-kHz repetition-rate OH planar laser–induced fluorescence (OH-PLIF) and stereoscopic particle image velocimetry (S-PIV) measurements were used to examine the fluid and flame kinematics during the transient blow-off process. Although the blow-off process of any individual nozzle—wherein local extinction led to mixing of cold fluid into the central recirculation zone (CRZ), leading to further extinction—was similar regardless of the internozzle spacing, the presence of adjacent flames influenced both the global and local kinematics. Cross-nozzle flame transport through convection of burning fluid was found to help stabilize the flames in the multinozzle configurations, but could not explain the improved stability of the intermediate spacing case. Furthermore, the intermediate spacing configuration was able to sustain attached flames with greater fluid dynamic strain rate than the other configurations, indicating that it was more resistant to local extinction, ultimately leading to total blow-off. The configuration with the intermediate nozzle spacing had the largest CRZ. A Damköhler number based on the CRZ axial length and bulk velocity at blow-off was relatively constant across the configurations, indicating that a large CRZ provides robustness against the blow-off process. These results demonstrate the complex interplay between fluid dynamics, geometry, and stability of combustion systems.
Published Version
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