Investigation on gas-liquid-solid three phase flow coupled with meso-scale particle-bubble interactions, particle-liquid turbulence and bubble induced turbulence in bubble column reactors

本项目旨在研究气-液-固三相鼓泡床反应器内的多相流动行为和相间相互作用机理。研究方法将包括理论建模、数值模拟和实验工作相结合。数值计算将同时使用多流体方法、三相人口平衡和LES-Euler/Lagrange方法。这两种方法都必须扩展，以允许考虑所有相关传输机制的三相鼓泡塔模拟。这首先包括对所有对于正确描述气泡和粒子运动很重要的力的考虑。鼓泡塔反应器中颗粒与气泡的细观相互作用、气泡诱导的湍流和颗粒调制的液体湍流将建立模型。因此，拟议的项目包括以下核心任务，每项任务都结合了对两种方法的详细验证和交叉比较：(1)模拟粒子-气泡相互作用，包括通过粘附力可能的粘连概率。该模型将基于随机碰撞模型，其中包括水动力相互作用。将为这两个相引入一个额外的阻力项，以描述颗粒被气泡拖曳，反之亦然。这些模型的发展将得到格子-玻尔兹曼模拟的支持，其中气泡被分解，颗粒被视为点质量。(2)发展了一种新的气泡合并和破碎核，该核考虑了气泡诱导的湍流、固体颗粒对液相湍流的调制以及修正湍流对气泡合并和破碎的影响。(3)建立了考虑气泡和固体颗粒对液相湍流调制的尺度和浓度效应的液相子网格模型，并与两种气泡群粒子平衡模型耦合进行三相大涡模拟。采用PIV和ECVT技术对气液固三相鼓泡塔反应器内的流体动力学参数和相分布特性进行了实验研究，特别是得到了气液固三相鼓泡塔反应器内的液相湍流功率谱。实验数据将被用来验证三相鼓泡塔反应器的大涡模拟，以及双流体和欧拉/拉格朗日方法，并研究气-液-固三相的基本相互作用。该项目将揭示三相鼓泡塔反应器中颗粒和气泡引起的细观湍流结构以及湍流调制的耦合机制。

This project aims to investigate the multi-phase flow behaviours and the mechanisms of interactions among phases in gas-liquid-solid three-phase bubble column reactors. The research methodologies will include the combination of theoretical modelling, numerical simulation and experimental work. Numerical calculations will be done concurrently using a multi-fluid approach in combination with a population balance for the three phases and a LES-Euler/Lagrange method. Both approaches have to be extended for allowing three-phase bubble column simulations considering all relevant transport mechanisms. This includes first of all the consideration of all forces important for correctly describing bubble and particle motion. Models will be developed for the meso-scale interactions between particles and bubbles, bubble induced turbulence and particle modulated liquid turbulence in bubble column reactors. Hence the proposed project includes the following core tasks, each combined with a detailed validation and cross-comparison of both approaches:(1) Modelling particle-bubble interactions including a possible sticking probability by adhesion forces. This model will be based on the stochastic collision model, which includes hydrodynamic interactions. An additional resistance term for both phases will be introduced in order to describe particles being dragged by bubbles and vice versa. These model developments will be supported by Lattice-Boltzmann simulations where bubbles are resolved and particles are treated as point masses.(2) Develop a novel bubble coalescence and breakup kernel that takes into account the effects of bubble induced turbulence, modulation on liquid phase turbulence by solid particles, and the impact of modified turbulence on bubble coalescence and breakup. The proposed model will be implemented by employing two bubble group population balance models.(3) To develop a liquid-phase sub-grid model that considers the scale and concentration effects of liquid phase turbulence modulation by bubbles and solid particles, which will then be coupled with the two bubble group population balance models to perform three-phase large eddy simulation. In addition sub-grid turbulence closures will be developed for application in the frame of LES-Euler/Lagrange simulations.(4) Adaptation of PIV and ECVT techniques to experimentally obtain the fluid dynamic parameters and characteristics of phase distribution in gas-liquid-solid three-phase bubble column reactors, especially the liquid phase turbulence power spectra. The experimental data will be used to validate the large eddy simulation of three-phase bubble column reactor, as well as two-fluid and Euler/Lagrange approaches and study the fundamental interactions of gas-liquid-solid three phases. The project will reveal the meso-scale turbulence structures due to particles and bubbles in the three-phase bubble column reactors and the coupling mechanisms of turbulence modulation.