Regimes of plasma-assisted ignition of turbulent hydrocarbon mixtures

实验表明，一种特殊的等离子体被称为非热等离子体，可以在传统点火方法失败的极端燃料稀薄条件下点燃碳氢化合物/空气混合物。这些非热等离子体通过高活性分子作用，以低能量输入刺激燃烧过程。在这个项目中，我们将开发和实现一个鲁棒和准确的预测模型，可用于优化等离子体辅助燃烧装置中的湍流点火。如果成功，该模型在减少燃烧产生的排放和提高热循环效率方面具有巨大潜力，对能源安全和环境产生积极影响。该项目旨在加强德克萨斯大学奥斯汀分校的本科STEM教育，并可能在项目完成后被美国各地的高中（9-12年级）采用。尽管在改进能量转换过程方面技术前景看好，但对等离子体放电、耦合等离子体和燃烧化学动力学以及湍流输运的相互作用缺乏系统的理解。为了在实际设备中实现等离子体辅助点火（PAI），以实现低排放和高效的能量转换技术，需要这样的理解。PAI事件的结果取决于能量运输和等离子体产生的自由基之间的竞争，以及从点燃核和加速化学动力学和热释放。在这个项目中，我们将确定控制湍流反应混合物PAI的无量纲参数，并通过利用大规模并行和大规模模拟来定义状态图。所采用的高保真物理模型确保不调用闭包。在我们的方法中考虑的流动结构是一个典型的均匀各向同性湍流，其中湍流输运速率和所有其他相关尺度可以被仔细控制。将考虑到等离子体放电的时间和空间尺度，湍流，化学动力学，以及分子的热量和质量扩散率。来自模拟的数据将使用强大的新数学技术进行分析，这些技术将量化化学反应的竞争以及瞬态点火事件中局部和瞬时的传输。我们方法的一个重要方面是，模拟将密切反映由我们的合作者并行进行的湍流燃烧容器中的PAI实验，为直接比较提供了独特的机会。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Experiments indicate that a special class of plasmas known as non-thermal plasmas can ignite hydrocarbon/air mixtures under extremely fuel-lean condition where conventional ignition approaches have failed. These non-thermal plasmas act through highly reactive molecules that stimulate the combustion process with low energy input. In this project, we will develop and implement a robust and accurate predictive model that can be used to optimize the plasma- assisted ignition of turbulent flows in combustion devices. If successful, the model developed holds enormous potential to reduce combustion-generated emissions and improve thermal cycle efficiency with positive outcomes for energy security and the environment. The project features activities that seek to enhance undergraduate STEM education at UT Austin and are likely to be adopted in high schools (G9-12) throughout the United States upon completion of the project.Despite the technological promise with regard to improving energy conversion processes, a systematic understanding of the interaction of plasma discharges, coupled plasma and combustion chemical kinetics, and turbulent transport is lacking. Such understanding is required in order to implement plasma-assisted ignition (PAI) in practical devices towards low-emission and high-efficiency energy-conversion technology. The outcome of a PAI event depends on the competition between transport of energy and plasma-generated radicals out of the igniting kernel and accelerating chemical kinetics and heat release. In this project, we will identify the non-dimensional parameters that govern PAI of turbulent reactive mixtures and define regime diagrams by leveraging massively parallel and large-scale simulations. The high-fidelity physical models employed ensure that no closures are invoked. The flow configuration considered in our approach is a canonical homogeneous isotropic turbulent flow whereby the rates of turbulent transport and all other relevant scales may be carefully controlled. Consideration will be given to temporal and spatial scales of plasma discharges, turbulent flow, chemical kinetics, and rates of molecular diffusion of heat and mass. Data from simulations will be analyzed using powerful new mathematical techniques that quantify the competition of chemical reactions and transport locally and instantaneously during transient ignition events. An important aspect of our approach is that simulations will closely mirror PAI experiments in a turbulent combustion vessel conducted in parallel by our collaborators, providing the unique opportunity for direct comparisons.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.