Theoretical description and modelling of low-current arcs at small gap distances

弧等离子体的跨学科重要性今天在许多工业过程和设备中得到了明确的证明。然而，对电弧光的物理机制及其复杂性的了解还不完全。为了简化对强耦合和非线性物理问题的描述，人们经常假设平衡条件、漂移-扩散近似、欧姆定律的简单形式等。这些假设在小电流(低于50A)和短弧长(低于2毫米)时尤其不成立。该项目旨在对短长度小电流电弧及其与电极的相互作用进行高级非平衡描述和建模。对物理过程和弧等离子体特性的彻底分析将提供有关弧长减少到只有几毫米时的空间和时间行为的知识。特别是，模拟将使我们能够研究这些弧等离子体偏离热和化学平衡的程度。该项目的主要研究目标是发展一个自洽的短弧等离子体非平衡模型。这个模型还应该能够覆盖更大的电流范围(低至几安培)，它将包括电极，以及准中性等离子体与电极附近的多物种空间电荷护套的适当匹配。到目前为止，还没有开发出具有这些能力的模型，需要它来显著提高对各种应用中遇到的短长度弧等离子体的物理理解。该项目的另一个目标是对近电极区域进行多尺度分析，并研究由于弧长缩短而产生的弧等离子体的空间行为。从技术角度来看，预计项目成果将是有利的：现有的工艺，如短路和微弧焊接，新工艺，如带弧焊设备的生成式制造，以及低压触点和开关设备的开发，可能受益于新的见解和建模能力。申请人在等离子体建模方面的广泛经验以及她最近致力于电弧等离子体的自洽和非平衡建模的研究对该项目的成功是有利的。

The interdisciplinary importance of arc plasmas is today unequivocally demonstrated in many industrial processes and devices. However, the understanding of the physical mechanisms in electric arcs and their complexity is still incomplete. Assumptions such as equilibrium conditions, drift-diffusion approximation, simple form of Ohm law among others are often made in order to simplify the description of the strongly coupled and non-linear physical problem. These assumptions fail in particular at low current (below 50 A) and short arc length (below 2 mm). This project is aimed at advanced non-equilibrium description and modelling of low-current electric arcs of short length and their interaction with the electrodes. A thorough analysis of the physical processes and arc plasma properties will provide knowledge about the spatial and temporal behavior of the arc when its length is reduced to only a few millimeters. In particular, the modelling will enable us to study the degree to which these arc plasmas have departed from thermal and chemical equilibrium. The main research objective of the project is the development of a self-consistent non-equilibrium model for short-length arc plasmas. This model should also be capable of covering a larger current range (down to a few amperes), it will include the electrodes, and a proper matching of the quasi-neutral plasma with the multi-species space-charge sheaths adjacent to the electrodes. No model with these capabilities has been developed so far, and it is needed in order to significantly improve the physical understanding of short-length arc plasmas encountered in various applications. A multi-scale analysis of the near- electrode regions as well as a study of the spatial behavior of the arc plasma due to shortening of the arc length are further objectives of the project. Project achievements are expected to be advantageous from a technological point of view: established processes like short and micro arc welding, new processes like generative manufacturing with arc welding devices, and the development of low-voltage contacts and switching devices might benefit from new insights and modelling capability. The wide experience of the applicant in plasma modelling and her most recent investigations dedicated to self-consistent and non-equilibrium modelling of arc plasma are advantageous for the project success.