Investigation Of Thermoacoustic Instability In Sequential Combustor During First Stage Lean Blow-Off
PROCEEDINGS OF THE COMBUSTION INSTITUTE(2021)
摘要
The pressing need to increase the operational and fuel flexibility of gas turbines has recently led to the development of new combustor architectures such as constant-pressure-sequential-combustion systems. In this context, we investigated the thermoacoustic instabilities near the lean blow-off limit of the first stage in a generic sequential combustor. High-speed OH chemiluminescence was employed to visualize the leanpremixed first stage swirled flame and the second stage autoignition flame, and piezo-sensors were used to record the acoustic pressure around the first-stage blow-off condition. The study identified two dominant frequencies in the pressure signals: one at 144Hz when flames in both stages existed in the combustor and the other at 84Hz after the blow-off of the first stage flame. A calculation of the acoustic modes of the sequential combustor, using a Helmholtz solver, revealed that these two frequencies both corresponded to the second eigenmode of the combustion chamber. The sequence of thermoacoustic events associated with the first stage flame blow-off was unraveled for this generic setup, and this analysis could support interpreting the corresponding complex spectral signature in case such an event would occur in a practical system. ? 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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关键词
Sequential Combustion, High speed chemilumilesence, Thermoacoustic, Lean blow-off, Autoignition
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