This paper studies the effect of inter-nozzle spacing on the lean blowoff performance in a combustor consisting of a linear array of five interacting nozzles. Simultaneous 5/10 kHz repetition-rate OH planar laser induced fluorescence (PLIF) and stereoscopic particle image velocimetry (S-PIV) are used to examine the hydrodynamics and the nozzle-nozzle interaction during the transient process of flame liftoff and reattachment. The combustor's lean operability limit did not have a monotonic relationship with inter-nozzle spacing; the two-nozzle configuration was more stable than the one-nozzle configuration, which was more stable than the five-nozzle configuration. The OH-PLIF images showed that the blowoff process of any individual nozzle was similar to that for a single bluff-body stabilized flame, though the presence of adjacent flame may enhance the stability limit through cross-nozzle flame transport. However, the increases in strain rate and weakening of recirculation zones dominated the stability enhancement from the cross-nozzle flame transport when the operating nozzles further increased from two to five. In all configurations, blow-off occurred at a relatively constant Damkohler number when the ratio of the recirculation zone length to bulk velocity was used as the fluid time scale.
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