This paper presents experimental study on self-excited combustion instability characteristics of premixed low-swirl flames in a multi-nozzle can combustor with counter-swirl and co-swirl arrays. Experiments were carried out over a wide range of inlet velocity from 4 m/s to 15.5 m/s and equivalence ratio from 0.5 to 0.85. Phase-locked OH planar laser-induced fluorescence was employed to measure flame shape and identify heat release rate. Four operation regions: stable combustion region, unstable combustion region, flashback region and extinguish region are observed for both array burners. The stable operating window for counter-swirl array is wider compared to the co-swirl array. Pressure fluctuation amplitude for co-swirl burner is larger than the counter-swirl arrangement at the same operating condition. In the unstable combustion region, the counter-swirl flames trigger the 2L mode of the combustion system while co-swirl flames incite three longitudinal modes with the highest amplitude near 3L. Rayleigh index distribution reveals neighboring flame interaction results in thermoacoustic coupling for multi-nozzle flames. Additionally, for counter-swirl array, thermoacoustic couplings in flame base region and shear region are also the main reasons for inducing self-excited combustion instabilities. For co-swirl array, the instability driving zones also locate at the lip region and the tail of center flame.
Experimental Study on Instability Characteristics of Low-Swirl Flames in a Multi-Nozzle Combustor With Different Swirling Arrays
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Liu, W, Ge, B, Tian, Y, Zang, S, Weng, S, Li, M, & Xu, W. "Experimental Study on Instability Characteristics of Low-Swirl Flames in a Multi-Nozzle Combustor With Different Swirling Arrays." Proceedings of the ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. Volume 4A: Combustion, Fuels and Emissions. Seoul, South Korea. June 13–17, 2016. V04AT04A042. ASME. https://doi.org/10.1115/GT2016-56714
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