Flame simulations with an open-source code

Flame simulations are used to gain insight into combustion physics and to design combustion systems such as piston engines, gas–turbine engines, and process heaters. In these simulations, the balance between reaction and molecular mixing plays a key role. To model molecular mixing, using a full multicomponent approach leads to high accuracy at the expense of a hefty computational cost. Thus, the use of a mixture-averaged model is usually preferred. Hence, this paper presents and tests a new OpenFOAM®-based code that incorporates a detailed, mixture-averaged approach for calculating transport properties in reacting flows, and provides a capability to solve either fully-compressible or low-Mach-number governing equations. The code is made readily available on GitHub and is written completely in OpenFOAM®’s native code framework, making it highly portable and easy to maintain, enhance, and extend. It is tested by modeling two laminar flames, and two turbulent flames undergoing extinction and reignition. Overall, predictions with the present code are seen to be in good agreement with experimental and direct-numerical-simulation data.

火焰模拟用于深入洞悉燃烧物理机理，并可用于设计活塞发动机、燃气涡轮发动机及工艺加热器等各类燃烧系统。在这类模拟中，反应与分子混合之间的平衡起着关键作用。为模拟分子混合过程，采用全多组分方法虽可获得极高的模拟精度，但需承担高昂的计算开销作为代价。因此，混合平均模型（mixture-averaged model）通常是更优选的建模方案。为此，本文提出并测试了一款基于OpenFOAM®的新型代码：该代码集成了用于计算反应流输运性质（transport properties）的精细化混合平均模型，且支持求解全可压缩或低马赫数控制方程。该代码已公开上传至GitHub平台，且完全基于OpenFOAM®的原生代码框架编写，具备极强的可移植性，同时便于后续的维护、改进与扩展。本文通过对两场层流火焰以及两场经历熄火与复燃过程的湍流火焰进行建模，完成了对该代码的验证。整体而言，本代码生成的预测结果与实验数据及直接数值模拟（direct-numerical-simulation）数据均具有良好的一致性。