Junhua Zhang , Xin Hui , Xin Xue , Lei Li , Jianchen Wang , Chih-Jen Sung
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引用次数: 0
Abstract
Centrally-staged combustors, characterized by a center pilot flame surrounded by an annual main stage flame, are widely used in modern aeroengines to achieve low NOx emissions. However, due to the premixed combustion of the main stage, centrally-staged combustors are prone to combustion instability. This paper experimentally investigates the bifurcation behaviors and nonlinear dynamics of combustion instabilities in a centrally-staged swirl-stabilized combustor fueled by aviation kerosene fuel. The current study reveals that the swirling flame transitions from a stable state to a limit-cycle oscillation state either by increasing the overall equivalence ratio of the dome or by decreasing the fuel split ratio. This transition manifests as a supercritical Hopf bifurcation and is essentially governed by the main stage equivalence ratio. Synchronization between pressure and heat release rate fluctuations is found to occur when the main stage equivalence ratio surpasses a threshold, resulting in large-amplitude oscillations and ultra-harmonics that stem from nonlinear interactions. Bispectral mode decomposition is further employed to elucidate the nonlinear triadic interactions of the thermoacoustic system, successfully revealing the interaction routes among different modes. This analysis indicates that the triadic mode interactions predominately occur in the main flame region, while the pilot flame region is insignificant as long as the oscillation amplitude remains low. These findings provide a deeper understanding of the combustion instability in stratified swirling flames in general and contribute to the development of better strategies for controlling combustion instability in centrally-staged combustors in particular.
期刊介绍:
Applied Energy serves as a platform for sharing innovations, research, development, and demonstrations in energy conversion, conservation, and sustainable energy systems. The journal covers topics such as optimal energy resource use, environmental pollutant mitigation, and energy process analysis. It welcomes original papers, review articles, technical notes, and letters to the editor. Authors are encouraged to submit manuscripts that bridge the gap between research, development, and implementation. The journal addresses a wide spectrum of topics, including fossil and renewable energy technologies, energy economics, and environmental impacts. Applied Energy also explores modeling and forecasting, conservation strategies, and the social and economic implications of energy policies, including climate change mitigation. It is complemented by the open-access journal Advances in Applied Energy.