The main objective of this article is to investigate the capability of the flamelet progress variable (FPV) model to capture the extinction processes observed in under-ventilated fire scenarios. To this end, large eddy simulation (LES) of the methane line fire plumes in oxygen-reduced environments down to global extinction, investigated experimentally at the University of Maryland (UMD), is performed. Two experimental burner configurations, that differ by the presence (anchored) or not (non-anchored) of an oxygen anchor to stabilise the flame base, are considered leading to two different extinction modes. Both the FPV and the steady laminar flamelet (SLF) model coupled with a presumed filtered density function (FDF) are considered. The Rank Correlated Full Spectrum k-distribution (RCFSK) model is used as a gas radiative property model. In both non-anchored and anchored scenarios, the FPV model reproduces with fidelity the evolution of the fire plume structure, radiative loss, and combustion efficiency with decreasing $X_{O_2}$ down to global extinction, without introducing any adjustable constant. The extinction in the non-anchored scenario occurs owing to flame-based detachment coupled to the generation of a buoyancy-driven vortex and is found to be very sensitive to the grid resolution in the near burner region. The present results suggest that these processes can be adequately resolved with a spatial resolution of 2.5 mm in this region. The SLF model, for its part, provides reliable predictions comparable to the FPV as long as no local extinction/re-ignition process occurs.

本文的主要目的是研究小火焰进展变量 (FPV) 模型捕捉在通风不足的火灾情景中观察到的熄灭过程的能力。为此，在马里兰大学 (UMD) 进行了实验研究，在氧气减少的环境中对甲烷线火羽进行大涡模拟 (LES)，直至全球灭绝。两种实验燃烧器配置的不同之处在于是否存在（锚定）或不存在（非锚定）氧锚以稳定火焰底部，被认为导致两种不同的熄灭模式。考虑了 FPV 和稳定层流火焰 (SLF) 模型以及假定的过滤密度函数 (FDF)。秩相关全谱 k 分布 (RCFSK) 模型用作气体辐射特性模型。$X_{{○}_2}$直到全球灭绝，没有引入任何可调常数。非锚定场景中的灭绝是由于基于火焰的分离与浮力驱动涡流的产生相结合而发生的，并且被发现对燃烧器附近区域的网格分辨率非常敏感。目前的结果表明，这些过程可以在该区域以 2.5 毫米的空间分辨率得到充分解决。SLF 模型就其本身而言，提供与 FPV 相当的可靠预测，只要不发生局部消光/重燃过程。