Numerical simulations are foreseen to provide a tremendous increase in gas-turbine burners efficiency in the near future. Modern developments in numerical schemes, turbulence models and the consistent increase of computing power allow Large Eddy Simulation (LES) to be applied to real cold flow industrial applications. However, the detailed simulation of the gas-turbine combustion process remains still prohibited because of its enormous computational cost. Several numerical models have been developed in order to reduce the costs of flame simulations for engineering applications. In this paper, the Flamelet-Generated Manifold (FGM) chemistry reduction technique is implemented and progressively extended for the inclusion of all the combustion features that are typically observed in stationary gas-turbine combustion. These consist of stratification effects, heat loss and turbulence. Three control variables are included for the chemistry representation: the reaction evolution is described by the reaction progress variable, the heat loss is described by the enthalpy and the stratification effect is expressed by the mixture fraction. The interaction between chemistry and turbulence is considered through a presumed beta-shaped probability density function (PDF) approach, which is considered for progress variable and mixture fraction, finally attaining a 5-D manifold. The application of FGM in combination with heat loss, fuel stratification and turbulence has never been studied in literature. To this aim, a highly turbulent and swirling flame in a gas turbine combustor is computed by means of the present 5-D FGM implementation coupled to an LES turbulence model, and the results are compared with experimental data. In general, the model gives a rather good agreement with experimental data. It is shown that the inclusion of heat loss strongly enhances the temperature predictions in the whole burner and leads to greatly improved NO predictions. The use of FGM as a combustion model shows that combustion features at gas turbine conditions can be satisfactorily reproduced with a reasonable computational effort. The implemented combustion model retains most of the physical accuracy of a detailed simulation while drastically reducing its computational time, paving the way for new developments of alternative fuel usage in a cleaner and more efficient combustion.

中文翻译：

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FGM 的 5 维实现，用于燃气轮机燃烧室中带热损失的分层旋流火焰的大涡模拟

预计数值模拟将在不久的将来大幅提高燃气轮机燃烧器的效率。数值方案、湍流模型的现代发展和计算能力的不断提高使得大涡模拟 (LES) 能够应用于真正的冷流工业应用。然而，由于计算成本巨大，对燃气轮机燃烧过程的详细模拟仍然受到禁止。为了降低工程应用的火焰模拟成本，已经开发了几种数值模型。在本文中，实施并逐步扩展了小火焰生成歧管（FGM）化学还原技术，以包含固定式燃气轮机燃烧中通常观察到的所有燃烧特征。这些包括分层效应、热损失和湍流。化学表示包括三个控制变量：反应演化由反应进度变量描述，热损失由焓描述，分层效应由混合物分数表示。通过假定的β形概率密度函数（PDF）方法来考虑化学与湍流之间的相互作用，该方法被考虑为进度变量和混合分数，最终获得5维流形。文献中从未研究过 FGM 与热损失、燃料分层和湍流相结合的应用。为此，通过与 LES 湍流模型相结合的当前 5 维 FGM 实现来计算燃气轮机燃烧器中的高度湍流和漩涡火焰，并将结果与​​实验数据进行比较。总的来说，该模型与实验数据吻合得相当好。结果表明，包含热损失极大地增强了整个燃烧器的温度预测，并大大改善了 NO 预测。使用 FGM 作为燃烧模型表明，通过合理的计算工作可以令人满意地再现燃气轮机条件下的燃烧特征。所实施的燃烧模型保留了详细模拟的大部分物理精度，同时大大减少了计算时间，为更清洁、更高效的燃烧中替代燃料使用的新发展铺平了道路。