Statistical modeling of collision frequencies of non-spherical agglomerates

非球形团聚体碰撞频率的统计模型

• 批准号: 444076285
• 负责人: Professor Dr. Andreas Kronenburg
• 金额: --
• 依托单位: Institut für Technische Verbrennung (ITV)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/444076285?language=en
• 关键词: Statistical; modeling; collision; frequencies; non

Agglomeration is one of the key mechanisms for particle and aerosol growth. This growth process can easily span several orders of magnitude from the nanoscale to the microscale under process conditions that are typical for particle flame synthesis. Particle collision leads to particle growth and – depending on material properties and temperature – to agglomerate with clearly varying morphology. The mechanisms, however, that drive relative particle motion and collision depend on the agglomerates’ size. While collision mechanisms for very small and very large, spherical particles are well understood, there is no thoroughly validated model for particle collision of non-spherical particles in the transition region. In the present work, new models for collision frequencies of non-spherical agglomerates at sizes typical for particle flame synthesis will therefore be analysed and validated.Numerical simulations suitable for validation need to allow for agglomerate growth across several orders of magnitude, they need to account for the correct ratio of all relevant length scales such as primary particle diameter and turbulent length scales, and they need allow for effects of fractal agglomerate morphology on growth dynamics. Conventional simplifications that are based on scale separation between the small and the large scales are no longer valid due to the significant growth of the agglomerates and a wide range of scales needs to be resolved. The distinction of the project is the use of a coarse-graining approach that allows to represent the smallest scales by larger (coarser) scales and to significantly reduce computational requirements. Only by coarse-graining, the entire range of length scales can be computed.Firstly, the coarse-graining approach will be further developed to allow for a direct tracking of all agglomerates while resolving all relevant turbulent scales. Only then, an explicit analysis of collision frequencies between agglomerates of different sizes can be conducted and direct evaluation of the accuracy of existing models is possible. Secondly, the large data sets of these direct simulations will be used to automatize the additional characteristics of the coarse-grained particles that allow for the reduction in the degrees of freedom and to generate alternative models for the collision frequencies using deep learning methods.

团聚是颗粒物和气溶胶增长的关键机制之一。在颗粒火焰合成的典型工艺条件下，这种生长过程可以很容易地跨越从纳米级到微米级的几个数量级。颗粒碰撞导致颗粒生长，并且-取决于材料性质和温度-以明显不同的形态聚集。然而，驱动相对颗粒运动和碰撞的机制取决于团聚体的尺寸。虽然非常小和非常大的球形颗粒的碰撞机制已经很好地理解，但是对于过渡区域中的非球形颗粒的颗粒碰撞还没有经过彻底验证的模型。在目前的工作中，非球形团聚体的碰撞频率的新模型，在典型的颗粒火焰合成的大小，因此将进行分析和验证。数值模拟适用于验证需要允许团聚体的增长跨越几个数量级，他们需要考虑到所有相关的长度尺度，如初级颗粒直径和湍流长度尺度的正确比例，并且它们需要考虑分形团聚体形态对生长动力学的影响。传统的简化，是基于规模之间的小规模和大规模的分离不再有效，由于显着增长的团聚体和广泛的规模需要解决。该项目的区别是使用粗粒度的方法，允许用更大（更粗）的尺度来表示最小的尺度，并显着降低计算要求。只有通过粗粒化，才能计算整个长度尺度范围。首先，粗粒化方法将进一步发展，以允许直接跟踪所有团聚体，同时解决所有相关的湍流尺度。只有这样，才能对不同尺寸的团聚体之间的碰撞频率进行明确的分析，并直接评估现有模型的准确性。其次，这些直接模拟的大型数据集将用于自动化粗粒度颗粒的附加特征，这些特征允许减少自由度，并使用深度学习方法生成碰撞频率的替代模型。