Hierarchical modeling concepts for ignition processes of fluorinated refrigerants

子项目的目标是建立一个分层数学模型，用于模拟含氟制冷剂(R32（二氟甲烷）、R1234yf（2,3,3,3-四氟丙烯）和R1234ze（反式-1,3,3,3-四氟丙烯）在层流和湍流条件下的点火过程。项目合作伙伴的实验和理论结果将用于模型验证和模型开发。该模型的建立是基于详细的数值模拟、化学动力学及其与分子输运耦合的分析和模型简化，以及点火概率的统计模型。这个子项目的重点是点火过程的初始阶段，特别是化学动力学与分子运输性质的相互作用。特别要解决以下问题：点火源对初始火焰核形成的影响是什么？离子反应对化学动力学有重要影响吗？小点火半径下火焰核形成的机理是什么？氟化化合物的低火焰传播速度是否定性地改变了着火的早期阶段？核的点火和自持火焰传播形成的最小点火能量有区别吗？点火核形成的统计波动有多重要？为了回答这些问题，将使用详细的动力学机制结合中性和带电物质的详细输运模型进行详细的数值模拟。为了关注潜在过程的物理化学，并允许详细的计算，重点将放在空间上的一维配置（包括曲率和应变效应）上，并且只在几个关键测试用例中执行对二维配置的扩展。此外，将基于反应扩散流形（REDIM）的概念对耦合反应扩散系统进行时标分析。这将允许识别控制子过程并开发简化的耦合反应-扩散模型，然后将其用于点火过程的分层统计模型。

The goal of the subproject is to develop a hierarchical mathematical model for the simulation of ignition of fluorinated refrigerants (R32 (difluoromethane), R1234yf (2,3,3,3-tetrafluoropropene), and R1234ze (trans-1,3,3,3-tetrafluoropropene)) under laminar and turbulent conditions. Experimental and theoretical results of the project partners will be used for model validation and model development. The model development is based on detailed numerical simulations, analysis and model reduction for the chemical kinetics and its coupling with molecular transport, and statistical models for the ignition probability. The focus of this subproject is on the initial phase of the ignition process, and in particular on the interaction of the chemical kinetics with molecular transport properties. In particular the following questions will be addressed: What is the influence of the ignition source on the formation of the initial flame kernel? Do reactions of ions have an important impact on the chemical kinetics? Which mechanisms govern flame kernel formation for small ignition radii? Does the low flame propagation velocity of fluorinated compounds change the early stage of the ignition in a qualitative way? Is there a difference between minimum ignition energies for ignition of the kernel and the formation of a self-sustained flame propagation? How important are statistical fluctuations of the ignition kernel formation? In order to answer these questions, detailed numerical simulations will be performed using detailed kinetic mechanisms in combination with detailed transport models for neutral and charged species. In order to focus on the physical chemistry of the underlying processes, and to allow detailed calculations, a focus will be on spatially one-dimensional configurations (including curvature and strain effects), and an extension to two-dimensional configurations will be performed only for a few critical test cases. Furthermore, time scale analyses for the coupled reaction-diffusion system will be performed based on the concept of Reaction-Diffusion-Manifolds (REDIM). This will allow to identify the governing subprocesses and to develop reduced coupled reaction-diffusion models, which are then used for hierarchical statistical models for the ignition process.