A theoretical and numerical evaluation of the steady-state burning rate of vertically oriented PMMA slabs
A theoretical and numerical evaluation of the steady-state burning rate of vertically oriented PMMA slabs
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DOI：
10.1080/13647830701843270
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发表时间：
2008-05
影响因子：
1.3
通讯作者：
J. Consalvi;Y. Pizzo;A. Kaiss;J. Torero;B. Porterie
中科院分区：
文献类型：
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作者：
J. Consalvi;Y. Pizzo;A. Kaiss;J. Torero;B. Porterie
对垂直取向聚甲基丙烯酸甲酯(PMMA)板材的稳态燃烧速率进行了数值研究。将模型预测与层流边界层理论的测量和结果进行了比较。数值模式提供了Favre平均的Navier-Stokes方程的解，以及湍流、燃烧、碳烟产生和辐射的子模型。凝聚相过程的模拟基于一维热传导方程，而热解过程采用相变潜热方法处理。结果表明，热解区可分为三个区域。在流动的层流部分(Grx<；4.3×10 7)，预测的归一化燃烧速率ṁ“px/μ∞是Grx的幂函数，其指数接近于Lbl理论的指数，表面再辐射是主要的差异来源。从自由流动的LBL理论出发，证明了局部燃速与剪切速度梯度成反比。数值模式结果从整体上证实了这一点。在Grx=4.3×107时，数值再现了实验观察到的表示层流区结束的燃速斜率的变化。由Grx=2.5×109模型计算的结果表明，裂解产物的表面质量通量随x的增大而增大，与文献中的实验数据一致。
The steady state burning rate of vertically oriented slabs of poly-methyl-methacrylate (PMMA) is numerically investigated. Model predictions are compared with measurements and results of the laminar boundary layer (LBL) theory. The numerical model provides a solution of the Favre-averaged Navier–Stokes equations coupled with sub-models for turbulence, combustion, soot production and radiation. The modelling of condensed phase processes is based on the one-dimensional heat transfer equation and pyrolysis is treated as a phase change using the latent heat approach. Results show that the pyrolysing region can be divided into three regions. In the laminar part of the flow (Gr x < 4.3 × 107), the predicted normalised burning rate, ṁ″ p x/μ∞, is a power-law function of Gr x with an exponent close to that of the LBL theory, surface re-radiation being the primary source of discrepancies. From the LBL theory for free flow, it is demonstrated that the local burning rate is inversely proportional to the shear velocity gradient. This is globally confirmed by numerical model results. At Gr x = 4.3 × 107 the change in slope of the burning rate observed experimentally, which indicates the end of the laminar flow region, is reproduced numerically. From Gr x = 2.5 × 109 model results show that the surface mass flux of pyrolyzate increases with x, in agreement with experimental data in literature.