| Author: | Wang, Fei |
| Title: | Numerical simulation of aerosol dynamics and coupling with CFD for soot modelling in combustion flows |
| Advisors: | Chan, Tat Leung (ME) An, Liang (ME) |
| Degree: | Ph.D. |
| Year: | 2025 |
| Department: | Department of Mechanical Engineering |
| Pages: | xxxi, 257 pages : color illustrations |
| Language: | English |
| Abstract: | The incomplete combustion of carbon-based fuels leads to the appearance of soot. It is required to predict and control soot emissions due to the detrimental effects on the environment and human health. Detailed soot models are based on aerosol dynamics, which is governed by the population balance equation (PBE). In the present study, solving the particle size distribution (PSD) of the PBE is conducted to deepen the understanding of aerosol dynamics and coupled with CFD to investigate soot formation and evolution in laminar and turbulent combustion flows. A new sorting algorithm-based merging weighted fraction Monte Carlo (SAMWFMC) method is firstly proposed and developed to solve the PBE of coagulation based on sorting algorithm and a new merging scheme. Numerical results of the SAMWFMC method show excellent agreement with analytical solutions and very low stochastic errors in different order moments of PSD. Instead of dealing with only one or several dynamic processes, a new sorting algorithm-based merging Monte Carlo method (SAMMC) capable of solving all aerosol dynamic processes is then proposed and developed based on a new neighbour merging method. Numerical results show that the SAMMC method has very high computational accuracy and can accurately deal with dynamic processes without introducing systematic errors. Simultaneously, a new OpenFOAM solver incorporating a detailed transport model is developed for reacting flow simulations. Systematic validations are conducted to evaluate its computational performance. The successful development and implementation of the accurate numerical framework provide a new CFD tool for the combustion community. A newly proposed dimer-based soot model involving various aerosol dynamics is then incorporated into the new numerical framework for investigating soot formation in laminar diffusion flames. Simulated soot volume fractions (SVFs) agree very well with experimental data under different oxygen mole fractions (Xo) and strain rates (K). With Xo increasing or K decreasing, dimer production and surface growth are significantly enhanced, leading to an increase of SVF and skewness of SVF profile towards the fuel stream. To gain a deeper understanding of turbulence modelling, a new one-equation turbulence model is developed in the numerical framework, which combines the best characteristics of standard k-e and Wilcox's k-co turbulence models. Numerical validation of benchmark flow configurations demonstrates that the new turbulence model has a great potential to predict flow separation and reattachment. Finally, the numerical framework coupling an extended soot sectional method with a finite-rate chemistry model is used for soot modelling in turbulent bluff body flames. Results show that the numerical framework can accurately predict the flow and flame properties and well capture the soot formation and evolution processes. With bluff body radius increasing, soot PSD remains a bimodal shape and shifts towards the larger soot aggregate side at the centerline and within the recirculation zone. Coagulation predominantly occurs at small soot aggregates, while PAH condensation and HACA surface growth take significant effect at large soot aggregates. In summary, numerical simulation of aerosol dynamics provides a better understanding of PSD evolution, and the newly developed CFD numerical framework demonstrates high capability in soot modelling. |
| Rights: | All rights reserved |
| Access: | open access |
Copyright Undertaking
As a bona fide Library user, I declare that:
- I will abide by the rules and legal ordinances governing copyright regarding the use of the Database.
- I will use the Database for the purpose of my research or private study only and not for circulation or further reproduction or any other purpose.
- I agree to indemnify and hold the University harmless from and against any loss, damage, cost, liability or expenses arising from copyright infringement or unauthorized usage.
By downloading any item(s) listed above, you acknowledge that you have read and understood the copyright undertaking as stated above, and agree to be bound by all of its terms.
Please use this identifier to cite or link to this item:
https://theses.lib.polyu.edu.hk/handle/200/13821