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

点击翻译按钮获取中文摘要

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.