Extension of the Eddy Dissipation Concept for turbulence/chemistry interactions to MILD combustion
Extension of the Eddy Dissipation Concept for turbulence/chemistry interactions to MILD combustion
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DOI：
10.1016/j.fuel.2015.09.020
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发表时间：
2016
期刊：
影响因子：
7.4
通讯作者：
A. Parente;Mohammad Rafi Malik;F. Contino;A. Cuoci;B. Dally
中科院分区：
文献类型：
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作者：
A. Parente;Mohammad Rafi Malik;F. Contino;A. Cuoci;B. Dally
在过去的 30 年里，涡耗散概念 (EDC) 已在业界广泛应用于湍流燃烧问题的数值模拟。 EDC 的成功主要是因为与其他一些模型相比，它能够以可承受的计算成本整合详细的化学机制。为了捕获湍流火焰，其中湍流和化学动力学之间存在强耦合，需要详细的动力学方案。这种火焰存在于中度和高度低氧稀释（MILD）燃烧中，与传统燃烧相比，化学时间尺度增加，主要是因为反应速度较慢（由于反应物的稀释）。最近的建模研究强调了标准 EDC 模型在应用于 MILD 系统模拟时的局限性，特别是对温度水平的显着高估。提出了对模型系数的修改，以考虑 MILD 燃烧的具体特征，即反应区域的扩展和最高温度的降低。本文的目的是提供函数表达式，显示 EDC 系数对无量纲流动参数（例如雷诺数和 Damköhler 数）的依赖性，同时考虑 MILD 燃烧状态的具体特征，其中热稀释剂的存在及其对流动和混合场的影响会影响反应速率和热场。使用阿德莱德喷射热协流 (JHC) 燃烧器在不同协流成分（3%、6% 和 9% O2 质量分数）和燃油喷射雷诺数（5000、10,000 和 20,000）下稳定的火焰的详细实验数据对该方法进行了验证。结果表明，相对于标准 EDC 配方，有很大的改进，特别是在稀释条件和中低雷诺数下。
Over the past 30 years, the Eddy Dissipation Concept (EDC) has been widely applied in the industry for the numerical simulations of turbulent combustion problems. The success of the EDC is mainly due to its ability to incorporate detailed chemical mechanisms at an affordable computational cost compared to some other models. Detailed kinetic schemes are necessary in order to capture turbulent flames where there is strong coupling between the turbulence and chemical kinetics. Such flames are found in Moderate and Intense Low-oxygen Dilution (MILD) combustion, where chemical time scales are increased compared with conventional combustion, mainly because of slower reactions (due to the dilution of reactants). Recent modelling studies have highlighted limitations of the standard EDC model when applied to the simulation of MILD systems, noticeably a significant overestimation of temperature levels. Modifications of the model coefficients were proposed to account for the specific features of MILD combustion, i.e. an extension of the reaction region and the reduction of maximum temperatures. The purpose of the present paper is to provide functional expressions showing the dependency of the EDC coefficients on dimensionless flow parameters such as the Reynolds and Damköhler numbers, taking into account the specific features of the MILD combustion regime, where the presence of hot diluent and its influence on the flow and mixing fields impacts on the reaction rate and thermal field. The approach is validated using detailed experimental data from flames stabilized on the Adelaide Jet in Hot Co-flow (JHC) burner at different co-flow compositions (3%, 6% and 9% O2mass fraction) and fuel-jet Reynolds numbers (5000, 10,000 and 20,000). Results show promising improvement with respect to the standard EDC formulation, especially at diluted conditions and medium to low Reynolds numbers.