Hybrid CFD/low-order modeling of nonlinear thermoacoustic oscillations
Hybrid CFD/low-order modeling of nonlinear thermoacoustic oscillations
复制标题
非线性热声振荡的混合 CFD/低阶建模
DOI：
10.1016/j.proci.2016.08.006
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
S. Jaensch
中科院分区：
文献类型：
--
作者：
S. Jaensch
本文提出并比较了层流预混火焰自激热声振荡的两种非线性时域模型。这两个模型是混合配方，火焰及其附近的反应流模拟解决，而声场建模与低阶模型，耦合到反应流模拟。首先，研究了基于完全可压缩Navier-Stokes方程的火焰模型。在这种情况下，火焰模拟通过入口边界处的特征波幅耦合到低阶模型。其次，火焰是解决了低马赫数反应流模拟。为了包括双向热声反馈，该火焰模型耦合到一个声学网络模型通过全局热释放速率和轴向速度的波动在一个参考位置的火焰上游。以腔室长度为分岔参数进行了分岔分析。两个模型都表现出复杂的非线性振荡，并且彼此吻合良好。因此，我们得出结论，耦合的线性声学模型和非线性火焰模型通过参考速度和全球热释放率是足够的，以准确地捕捉热声振荡的配置研究。这意味着最重要的非线性可以归因于流体动力学效应和火焰运动学。此外，研究证实，预混火焰主要响应于上游流速的波动。
This paper proposes and compares two nonlinear time-domain models of self-excited thermoacoustic oscillations of laminar premixed flames. Both models are hybrid formulations, where the flame and its immediate vicinity are resolved with a reactive flow simulation, while the acoustic field is modeled with a low-order model that is coupled to the reactive flow simulation. Firstly, a flame model based on the fully compressible Navier–Stokes equations is investigated. In this case, the flame simulation is coupled to the low-order model via the characteristic wave amplitudes at the inlet boundary. Secondly, the flame is resolved with a low Mach number reactive flow simulation. In order to include two-way thermoacoustic feedback, this flame model is coupled with an acoustic network model via the global heat release rate and the fluctuation of the axial velocity at a reference position upstream of the flame. A bifurcation analysis using the plenum length as bifurcation parameter is conducted. Both models exhibit complex nonlinear oscillations and are in good agreement with each other. Therefore, we conclude that the coupling of a linear acoustic model and a nonlinear flame model via reference velocity and global heat release rate is sufficient to accurately capture thermoacoustic oscillations of the configuration investigated. This implies that the most important nonlinearities can be attributed to hydrodynamic effects and flame kinematics. Furthermore, the study corroborates that premixed flames respond predominantly to fluctuations of the upstream flow velocity.
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