An Efficient Method to Reproduce the Effects of Acoustic Forcing on Gas Turbine Fuel Injectors in Incompressible Simulations
An Efficient Method to Reproduce the Effects of Acoustic Forcing on Gas Turbine Fuel Injectors in Incompressible Simulations
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DOI：
10.1007/s10494-019-00020-4
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发表时间：
2019-03
期刊：
影响因子：
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通讯作者：
N. Treleaven;Jialin Su;A. Garmory;G. Page
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文献类型：
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作者：
N. Treleaven;Jialin Su;A. Garmory;G. Page
以前的研究已经强调了空气质量流量和涡流波动对旋流稳定燃气轮机燃烧室非定常放热的重要性。因此，模拟能否正确解析热声分析中重要的热释放波动或火焰传递函数(FTF)，取决于该方法能否正确地包含典型稀燃燃油喷射器的多个空气通道中出现的涡流数和质量流量波动。研究中使用的喷油器具有工业代表性，其几何形状比典型的预混燃烧器、实验室规模的燃烧器复杂得多，并且必须正确地捕捉到每个流动通道之间的相互作用。本文比较了可压缩的、声强迫的CFD(计算流体动力学)模拟和不可压缩的、质量流速强迫的模拟。喷油器的不可压缩质量流量强迫是一种很有吸引力的方法，因为它具有较大的时间步长、较低的计算成本和燃烧模型的灵活选择，但它不能再现可压缩模拟和下游流动发展所给出的空气通道的涡流和质量流量波动。这将对用这种方法计算的任何FTF产生重大影响。然而，通过使用带有适当边界条件的截断区域，使用从施主可压缩模拟中提取的数据，精确的不可压缩模拟是可能的。提出了一种基于本征正交分解和傅立叶级数(PODFS)的新模型，该模型克服了强循环方法的几个缺点。使用这种方法的模拟被认为比可压缩模拟的计算成本要低得多。这提出了一种方法，其中使用非反应可压缩模拟来产生基于PODFS的边界条件，该边界条件可以用于更便宜的不可压缩反应FTF计算。在工业环境中，这种改进的计算效率允许更多地探索设计空间和改进燃烧室设计。
Previous studies have highlighted the importance of both air mass flow rate and swirl fluctuations on the unsteady heat release of a swirl stabilised gas turbine combustor. The ability of a simulation to correctly resolve the heat release fluctuations or the flame transfer function (FTF), important for thermoacoustic analysis, is therefore dependent on the ability of the method to correctly include both the swirl number and mass flow rate fluctuations which emerge from the multiple air passages of a typical lean-burn fuel injector. The fuel injector used in this study is industry representative and has a much more complicated geometry than typical premixed, lab-scale burners and the interaction between each flow passage must be captured correctly. This paper compares compressible, acoustically forced, CFD (computational fluid dynamics) simulations with incompressible, mass flow rate forced simulations. Incompressible mass flow rate forcing of the injector, which is an attractive method due to larger timesteps, reduced computational cost and flexibility of choice of combustion model, is shown to be incapable of reproducing the swirl and mass flow fluctuations of the air passages given by the compressible simulation as well as the downstream flow development. This would have significant consequences for any FTF calculated by this method. However, accurate incompressible simulations are shown to be possible through use of a truncated domain with appropriate boundary conditions using data extracted from a donor compressible simulation. A new model is introduced based on the Proper Orthogonal Decomposition and Fourier Series (PODFS) that alleviates several weaknesses of the strong recycling method. The simulation using this method is seen to be significantly computationally cheaper than the compressible simulations. This suggests a methodology where a non-reacting compressible simulation is used to generate PODFS based boundary conditions which can be used in cheaper incompressible reacting FTF calculations. In an industrial context, this improved computational efficiency allows for greater exploration of the design space and improved combustor design.