Hierarchical modeling concepts for ignition processes of fluorinated refrigerants

该分项目的目标是开发层流和湍流条件下模拟含氟制冷剂(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))点火的分层数学模型。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。模型的开发是基于对化学动力学及其与分子传输的耦合的详细的数值模拟、分析和模型简化，以及对着火概率的统计模型。这一分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传输特性之间的相互作用。特别是，将讨论以下问题：点火源对初始火焰核心的形成有什么影响？离子的反应对化学动力学有重要影响吗？对于较小的点火半径，哪些机制控制着火核的形成？含氟化合物的低火焰传播速度是否定性地改变了点火的早期阶段？核心点火的最小点火能量和自持火焰传播的形成之间有区别吗？点火核形成的统计波动有多重要？为了回答这些问题，将结合中性和带电物种的详细输运模型，使用详细的动力学机制进行详细的数值模拟。为了专注于基本过程的物理化学，并允许进行详细的计算，将重点放在空间一维构型(包括曲率和应变效应)上，并将仅对几个关键测试案例进行二维构型的扩展。此外，将基于反应-扩散-流形(REDIM)的概念对反应-扩散耦合系统进行时间尺度分析。这将允许确定控制子过程并开发简化的反应-扩散耦合模型，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.