A new model, PDRFOAM, has been developed for the prediction of gas explosions in congested plant. It uses the PDR approach to model the effect of small-scale obstacles, e.g., pipes and vessels on flame propagation and on explosion overpressure. While the effects of large obstacles i.e., that is the large scales are explicitly resolved. The equations for mass, momentum, enthalpy and Favre-averaged regress variable are solved. In addition, porosity modified standard k-ε turbulence model and the transport equations for the flame wrinkling parameter are solved. The model PDRFOAM, is built as a new application in OpenFOAM, suite of models. OpenFOAM is an open-source CFD package of routines for solution of systems of partial differential equations.

In addition, to the PDRFOAM model, the CADPDR program was developed which generates various fields (volume blockage, area blockages, surface area, sub-grid drag and turbulence generation parameters) needed by PDRFOAM. CADPDR needs as input obstacle files that list coordinates and dimension of the obstacles e.g. pipes and vessels. The PDRFOAM code solves porosity-modified momentum and continuity equations with sub-grid source terms. The combustion model in PDRFOAM is based on flame area transport. The turbulent burning velocity correlation used is based on Markstein and Karlowitz number. Flame area generation due to the folding of the flame around obstacles is explicitly modelled.

This paper presents the formulation of PDRFOAM and validation of the PDRFOAM code against three series of small- and medium-scale experiments i.e., ERGOS, MERGE and Buxton S-Series experiments. A total of more than 150 experiments were used for validation which includes variation in blockage ratio, grid pitch, size of the congested region, equivalence ratio, confinement, partial fill, obstacle diameter, different obstacle shapes and three different fuels. The model is compared against flame position, flame speed as a function of time and maximum overpressure obtained from experiments. Simulations predict the experimental trends of increase in overpressure with increase in blockage ratio, laminar burning velocity, partial fill of the gas cloud, size of the congested region, confinement, grid pitch and obstacle diameter. It also predicts the trends of increase in overpressure with increase in equivalence ratio, variation of maximum overpressure with ignition location, change in obstacle shape and obstacle configuration. The maximum overpressure predicted by simulations (see Fig. 1) is in general within the uncertainty of a factor of two.

已经开发了一种新模型 PDRFOAM，用于预测拥挤工厂中的气体爆炸。它使用 PDR 方法来模拟小规模障碍物的影响，例如管道和容器对火焰传播和爆炸超压的影响。而大障碍物的影响，即大尺度，被明确解决。求解了质量、动量、焓和 Favre 平均回归变量的方程。此外，还求解了孔隙率修正的标准k-ε湍流模型和火焰起皱参数的输运方程。PDRFOAM 模型是作为 OpenFOAM 模型套件中的新应用程序构建的。OpenFOAM 是一个开源 CFD 程序包，用于求解偏微分方程组。

此外，针对 PDRFOAM 模型，开发了 CADPDR 程序，生成 PDRFOAM 所需的各种场（体积阻塞、面积阻塞、表面积、亚网格阻力和湍流生成参数）。CADPDR 需要作为输入障碍文件，列出障碍的坐标和尺寸，例如管道和船只。PDRFOAM 代码使用子网格源项求解孔隙度修正的动量和连续性方程。PDRFOAM 中的燃烧模型基于火焰区域传输。使用的湍流燃烧速度相关性基于 Markstein 和 Karlowitz 数。由于障碍物周围的火焰折叠而产生的火焰区域被明确地建模。

本文介绍了 PDRFOAM 的制定和 PDRFOAM 代码针对三个系列中小型实验的验证，即 ERGOS、MERGE 和 Buxton S 系列实验。总共使用了 150 多个实验进行验证，其中包括阻塞率、网格间距、拥挤区域大小、当量比、限制、部分填充、障碍物直径、不同障碍物形状和三种不同燃料的变化。将该模型与火焰位置、作为时间函数的火焰速度和从实验获得的最大超压进行比较。模拟预测了随着堵塞比、层流燃烧速度、气体云的部分填充、拥挤区域的大小、限制、网格间距和障碍物直径的增加，超压增加的实验趋势。它还预测了超压随当量比的增加而增加的趋势，最大超压随点火位置的变化，障碍物形状和障碍物配置的变化。模拟预测的最大超压（见图 1）一般在 2 倍的不确定性范围内。