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Large-eddy simulation of combustion systems with convective heat-loss.

机译:具有对流热损失的燃烧系统的大涡模拟。

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摘要

Computer simulations have the potential to viably address the design challenges of modern combustion applications, provided that adequate models for the prediction of multiphysics processes can be developed. Heat transfer has particular significance in modeling because it directly affects thermal efficiencies and pollutant formation in combustion systems. Convective heat transfer from flame-wall interaction has received increased attention in aeronautical propulsion and power-generation applications where modern designs have trended towards more compact combustors with higher surface-to-volume ratios, and in diesel engines where enclosed volumes and cool walls provide ample conditions for thermal quenching. As intense flame-wall interactions can induce extremely large heat fluxes, their inclusion is important in computational models used to predict performance and design cooling systems.;In the present work, a flamelet method is proposed for modeling turbulence/chemistry interactions in large-eddy simulations (LES) of non-premixed combustion systems with convective heat-losses. The new method is based on the flamelet/progress variable approach of Pierce & Moin (J. Fluid Mech. 2004, 504:73-97) and extends that work to include the effects of thermal-losses on the combustion chemistry. In the new model, chemical-state databases are constructed by solving one-dimensional diffusion/reaction equations which have been constrained by scaling the enthalpy of the system between the adiabatic state and a thermally-quenched reference state. The solutions are parameterized and tabulated as a function of the mapping variables: mixture fraction, reaction progress variable, and normalized enthalpy. The new model is applied to LES of non-premixed methane-air combustion in a coaxial-jet with isothermal wall-conditions to describe heat transfer to the confinement. The resulting velocity, species concentration, and temperature fields are compared to experimental measurements and to numerical results from the adiabatic model. The new method shows distinct improvement in the prediction of temperature, mixture composition, and heat flux in the near-wall regions of the combustor.
机译:只要可以开发出用于预测多物理场过程的适当模型,计算机模拟就可以有效解决现代燃烧应用的设计挑战。传热在建模中具有特别重要的意义,因为它直接影响燃烧系统中的热效率和污染物形成。火焰-壁相互作用产生的对流传热在航空推进和发电应用中受到了越来越多的关注,在现代应用中,现代设计已趋向于使紧凑型燃烧器具有更高的表面积/体积比,而在封闭式容积和冷壁提供充足空间的柴油发动机中热淬火的条件。由于强烈的火焰-壁相互作用会产生极大的热通量,因此在用于预测性能和设计冷却系统的计算模型中,将它们包括在内非常重要。在当前工作中,提出了一种小火焰方法来模拟大涡流中的湍流/化学相互作用。对流热损失的非预混燃烧系统的模拟(LES)。新方法基于Pierce&Moin的小​​火焰/进度变量方法(J. Fluid Mech。2004,504:73-97),并扩展了其工作范围,包括热损失对燃烧化学的影响。在新模型中,化学状态数据库是通过求解一维扩散/反应方程而建立的,该方程已通过在绝热状态和热淬灭参考状态之间缩放系统的焓而受到限制。根据映射变量对溶液进行参数化和制表,这些变量包括:混合比,反应进程变量和归一化焓。该新模型应用于等温壁条件下的同轴射流中非预混合甲烷-空气燃烧的LES,以描述向密闭空间的热传递。将所得的速度,物质浓度和温度场与实验测量值以及绝热模型的数值结果进行比较。新方法在燃烧器近壁区域的温度,混合物组成和热通量的预测中显示出明显的改进。

著录项

  • 作者

    Shunn, Lee.;

  • 作者单位

    Stanford University.;

  • 授予单位 Stanford University.;
  • 学科 Applied Mechanics.;Energy.;Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 176 p.
  • 总页数 176
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 应用力学;机械、仪表工业;能源与动力工程;
  • 关键词

  • 入库时间 2022-08-17 11:37:41

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