Population balance modelling of nanoparticle formation in laminar and turbulent flows
File(s)
Author(s)
Tsagkaridis, Malamas
Type
Thesis
Abstract
Nanoparticle formation in reacting flows involves many complex phenomena such as turbulence, chemical kinetics, aerosol processes, particle size distribution (PSD) evolution, etc. Simulations of such processes should incorporate several models and solution methods. The main objective of the present work is to develop and employ accurate and comprehensive methodologies for simulating particle formation and flame synthesis in laminar and turbulent flows.
In the first part of the present thesis, we propose a novel extended population balance equation (PBE) model for aggregation and sintering and couple it with computational fluid dynamics (CFD) to investigate synthesis of silica nanoparticles in a laminar diffusion flame. The model is validated with the detailed experimental in-situ SAXS data of Camenzind et al. (2008) for the S-2 flame and is also compared with a monodisperse and a two-PBE approach.
In the second part, the extended one-PBE model is incorporated into the Large-Eddy Simulation - Probability Density Function (LES-PDF) modelling framework to investigate synthesis of silica nanoparticles in a turbulent diffusion flame. The models for gas-phase chemistry and aerosol dynamics were the same as those used in the laminar-flame simulation. Thus, by maintaining the same kinetics without any adjustments, we focus on the modelling issues arising in silica synthesis in turbulent flames. Numerical predictions are compared with the detailed experimental in-situ SAXS data of Camenzind et al. (2008) for the S-10 flame.
Finally, an investigation of turbulence-coagulation interaction via DNS coupled with PBE is presented in the third part of the thesis. Coagulation is an important process in several environmental and engineering applications involving turbulent flow, including soot formation and flame synthesis of nanoparticles, but its interaction with turbulence is not yet fully understood. In this work, we employ a discretisation (sectional) method for the solution of the PBE, which is free of a priori assumptions regarding the PSD, and couple it with a DNS for the flow field in order to study the behaviour and significance of correlations of turbulent number-density fluctuations.
In the first part of the present thesis, we propose a novel extended population balance equation (PBE) model for aggregation and sintering and couple it with computational fluid dynamics (CFD) to investigate synthesis of silica nanoparticles in a laminar diffusion flame. The model is validated with the detailed experimental in-situ SAXS data of Camenzind et al. (2008) for the S-2 flame and is also compared with a monodisperse and a two-PBE approach.
In the second part, the extended one-PBE model is incorporated into the Large-Eddy Simulation - Probability Density Function (LES-PDF) modelling framework to investigate synthesis of silica nanoparticles in a turbulent diffusion flame. The models for gas-phase chemistry and aerosol dynamics were the same as those used in the laminar-flame simulation. Thus, by maintaining the same kinetics without any adjustments, we focus on the modelling issues arising in silica synthesis in turbulent flames. Numerical predictions are compared with the detailed experimental in-situ SAXS data of Camenzind et al. (2008) for the S-10 flame.
Finally, an investigation of turbulence-coagulation interaction via DNS coupled with PBE is presented in the third part of the thesis. Coagulation is an important process in several environmental and engineering applications involving turbulent flow, including soot formation and flame synthesis of nanoparticles, but its interaction with turbulence is not yet fully understood. In this work, we employ a discretisation (sectional) method for the solution of the PBE, which is free of a priori assumptions regarding the PSD, and couple it with a DNS for the flow field in order to study the behaviour and significance of correlations of turbulent number-density fluctuations.
Version
Open Access
Date Issued
2023-02
Date Awarded
2023-07
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Rigopoulos, Stelios
Papadakis, George
Sponsor
Leverhulme Trust
Grant Number
RPG-2018- 101
Publisher Department
Mechanical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)