采用假定-PDF方法的升力湍流射流火焰一致条件矩闭合模型

IF 1.5 Q3 ENGINEERING, CHEMICAL
A. E. Sayed, R. Fraser
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引用次数: 5

摘要

用条件矩闭包法研究了升力射流火焰进入污浊共流的问题。选择条件速度(CV)和条件标量耗散率(CSDR)子模型,使它们与假定概率密度函数(PDF)的矩完全一致。CV采用pdf梯度扩散模型进行建模。基于齐次和非齐次混合分数PDF输运方程的二重积分实现了两个CSDR子模型。研究了CSDR模型在一定共流温度范围内的影响(),并通过对运输预算和稳定高度之前的自由基积累历史的分析确定了稳定机制。总的来说,化学、轴向对流和微混合之间的平衡,以及稳定高度上游不存在轴向扩散,表明火焰是通过自燃来稳定的。这一结论得到了快速积累的ahead,,和。非均匀CSDR模型在最活跃的混合分数下产生更高的耗散水平,从而导致更长的点火延迟和更大的起飞高度。均匀模拟产生的杂散源的影响很小,但不可忽略,尤其是在火焰区内。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Consistent Conditional Moment Closure Modelling of a Lifted Turbulent Jet Flame Using the Presumed -PDF Approach
A lifted turbulent jet flame issuing into a vitiated coflow is investigated using the conditional moment closure. The conditional velocity (CV) and the conditional scalar dissipation rate (CSDR) submodels are chosen such that they are fully consistent with the moments of the presumed probability density function (PDF). The CV is modelled using the PDF-gradient diffusion model. Two CSDR submodels based on the double integration of the homogeneous and inhomogeneous mixture fraction PDF transport equations are implemented. The effect of CSDR modelling is investigated over a range of coflow temperatures () and the stabilisation mechanism is determined from the analysis of the transport budgets and the history of radical build-up ahead of the stabilisation height. For all , the balance between chemistry, axial convection, and micromixing, and the absence of axial diffusion upstream of the stabilisation height indicate that the flame is stabilized by autoignition. This conclusion is confirmed from the rapid build-up of ahead of , , and . The inhomogeneous CSDR modelling yields higher dissipation levels at the most reactive mixture fraction, which results in longer ignition delays and larger liftoff heights. The effect of the spurious sources arising from homogeneous modelling is found to be small but nonnegligible, mostly notably within the flame zone.
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来源期刊
Journal of Combustion
Journal of Combustion ENGINEERING, CHEMICAL-
CiteScore
2.00
自引率
28.60%
发文量
8
审稿时长
20 weeks
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