Article
Thermodynamics
Binxuan Sun, Stelios Rigopoulos
Summary: This paper presents a comprehensive approach for modelling soot formation in turbulent flows by incorporating a recently developed conservative finite volume sectional method into the Large Eddy Simulation - Probability Density Function framework. The approach predicts particle size distribution of soot and considers aerosol dynamic processes, turbulence-chemistry interaction, and soot evolution. While the method can reasonably predict certain features of soot formation, there is underprediction in the magnitude of soot volume fraction.
COMBUSTION AND FLAME
(2022)
Article
Thermodynamics
Luke Henderson, Pradeep Shukla, Victor Rudolph, Suresh K. Bhatia
Summary: A 2-D population balance model with internal variables of carbon mass and surface sites was developed to study soot formation during hydrocarbon decomposition reactions. The model accurately predicts the size and composition distribution of soot particles under various conditions, which was confirmed by experimental data.
COMBUSTION AND FLAME
(2022)
Article
Thermodynamics
Hernando Maldonado Colman, Nasser Darabiha, Denis Veynante, Benoit Fiorina
Summary: Designing efficient and clean combustion devices to reduce soot formation is a major concern. Predictive simulations using virtual chemistry can reproduce characteristics of turbulent sooting flames and have a significant impact on soot formation.
COMBUSTION AND FLAME
(2023)
Article
Thermodynamics
L. Tian, R. P. Lindstedt
Summary: This study computationally investigates the impact of blending ammonia with ethylene on soot formation in laminar and turbulent flames. The results show that increased use of ammonia can suppress soot formation and lead to an increase in smaller soot particles. The suppression of soot is mainly caused by changes in the radical pool.
COMBUSTION AND FLAME
(2023)
Article
Biochemistry & Molecular Biology
Yang Cong, Yu Zhai, Xin Chen, Hui Li
Summary: This study validates the performance of several semi-empirical quantum chemistry methods in describing soot formation and discusses their limitations and applicability. The results show that these methods are qualitatively accurate but cannot provide quantitatively accurate data.
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
(2022)
Article
Energy & Fuels
Anxiong Liu, Zhan Gao, Stelios Rigopoulos, Kai H. Luo, Lei Zhu
Summary: In this paper, a population balance approach and a detailed soot model were used to simulate a laminar diffusion flame with blends of different components of biodiesel fuel. The simulation results successfully predicted the temperature rise, the shape of the soot occurrence zone, and the quantity of soot production. The model also captured the reducing tendency of soot formation as the percentage of DBE addition increased.
Article
Thermodynamics
Zhijie Huo, Matthew J. Cleary, Assaad R. Masri, Michael E. Mueller
Summary: A soot kinetic sectional scheme is coupled with the MMC-LES method to model soot formation in a turbulent flame. The interactions of soot formation, molecular chemistry, and turbulence are achieved through the MMC-LES model. The model results are compared to experimental data, showing good qualitative agreement but some discrepancies in numerical values.
COMBUSTION AND FLAME
(2022)
Review
Chemistry, Applied
E. Jiaqiang, Wanrong Xu, Yinjie Ma, Dongli Tan, Qingguo Peng, Yan Tan, Lehan Chen
Summary: Soot particles emitted by automobile engines have had a significant negative impact on the environment and human health. Understanding the complex process of soot formation and researching methods to reduce soot emission can help control pollution and contribute to advanced technology.
FUEL PROCESSING TECHNOLOGY
(2022)
Article
Thermodynamics
Lukas Berger, Achim Wick, Antonio Attili, Michael E. Mueller, Heinz Pitsch
Summary: A new LES model for subfilter soot-turbulence interactions is developed based on large-scale DNS data. The model significantly improves predictions by solving explicit transport equations for soot moments and using a new presumed PDF model that explicitly accounts for the sub-structure of the sooting mode.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2021)
Review
Thermodynamics
Jacob W. Martin, Maurin Salamanca, Markus Kraft
Summary: This review discusses the formation of carbonaceous nanoparticles from gas-phase molecules in hydrocarbon flames, highlighting both their useful applications and negative impacts as pollutants. Advances in experimental techniques have allowed for the direct observation of gas phase precursors and the transformation into nanoparticles over the past decade. Questions remain regarding the mechanisms leading to nanoparticle formation, with physically stabilised soot inception proposed as a potential middle ground combining physical and chemical routes.
PROGRESS IN ENERGY AND COMBUSTION SCIENCE
(2022)
Article
Thermodynamics
L. Tian, R. P. Lindstedt
Summary: This study quantifies the impact of differential diffusion on soot moments, statistical correlations, and Particle Size Distributions (PSDs) using a fully coupled transported joint probability density function (JPDF) method. The results show that reduced soot diffusion leads to an increase in the soot volume fraction RMS and a further reduction in the correlation between soot volume fraction and temperature in a particle-size-dependent manner. Similar observations are made for correlations between the soot volume fraction and the mass fractions of gas-phase species.
COMBUSTION AND FLAME
(2023)
Article
Thermodynamics
Pavan Prakash Duvvuri, Hernando Maldonado Colman, Michael E. Mueller
Summary: The oxidation of soot is crucial for understanding its behavior in turbulent reacting flows. The kinetic rates of soot oxidation and the role of turbulent transport are both important factors in determining the evolution of soot. This study investigates the relative importance of small-scale turbulent transport and oxidation kinetics on predicting soot evolution in turbulent nonpremixed flames.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Biology
Armin Shayesteh Zadeh, Baron Peters
Summary: In this study, a simple microkinetic model and chiral dumbbell model were utilized to investigate the formation mechanism of amyloid fibrils and predict docking and locking rate constants. These rate constants were embedded in a multiscale model to assist in extracting the correct docking and locking rate constants from experimental or molecular simulation data.
Article
Thermodynamics
Wesley R. Boyette, Scott A. Steinmetz, Thibault F. Guiberti, Matthew J. Dunn, William L. Roberts, Assaad R. Masri
Summary: This study investigates the effects of hydrogen and ammonia on soot production in turbulent flames, finding that hydrogen substitution increases soot production while ammonia substitution inhibits it. The results show that peak mean soot volume fraction is significantly lower in cases where ammonia is substituted for nitrogen, indicating the formation of smaller soot nanoparticles.
COMBUSTION AND FLAME
(2021)
Article
Thermodynamics
Binxuan Sun, Stelios Rigopoulos, Anxiong Liu
Summary: The paper aims to develop a population balance approach for accurate modelling of soot formation, with the accuracy of the method validated through experiments. The study finds that the two-PBE approach shows significant improvement in predicting soot morphology.
COMBUSTION AND FLAME
(2021)
Article
Thermodynamics
Anxiong Liu, Kai H. Luo, Stelios Rigopoulos, William Jones
Summary: In this article, a coupled PBE-CFD framework is proposed to study counterflow non-premixed flames and soot formation under an external electric field. The simulations show that the presence of an electric field modifies the flame structure and reduces soot formation, and the introduction of an electric correction factor enhances the flame stability.
COMBUSTION AND FLAME
(2022)
Article
Energy & Fuels
Anxiong Liu, Zhan Gao, Stelios Rigopoulos, Kai H. Luo, Lei Zhu
Summary: In this paper, a population balance approach and a detailed soot model were used to simulate a laminar diffusion flame with blends of different components of biodiesel fuel. The simulation results successfully predicted the temperature rise, the shape of the soot occurrence zone, and the quantity of soot production. The model also captured the reducing tendency of soot formation as the percentage of DBE addition increased.
Article
Mechanics
Malamas Tsagkaridis, Stelios Rigopoulos, George Papadakis
Summary: The objective of this study is to investigate the interaction between turbulence and coagulation through direct numerical simulation (DNS) coupled with the population balance equation (PBE). The study found that correlations due to turbulent fluctuations of particle number density make a significant contribution to the coagulation process.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
S. Schenke, F. Sewerin, B. van Wachem, F. Denner
Summary: We present a physical model and a numerical method for simulating acoustic waves in an accelerating background flow field using a space- and time-dependent Galilean-type coordinate transformation. The model considers the nonlinear dynamics of acoustic waves in a non-uniformly accelerating flow field under the assumption of spherical symmetry. The numerical simulations show that different combinations of flow acceleration and emitted wavelength result in geometrically similar sets of wave characteristics, but nonlinear variations in wave amplitude are observed along the wave characteristics.
Article
Engineering, Chemical
Malamas Tsagkaridis, Stelios Rigopoulos, George Papadakis
Summary: In this study, a new extended population balance equation (PBE) model coupled with computational fluid dynamics (CFD) is proposed to investigate the synthesis of silica nanoparticles in a laminar diffusion flame. The model includes finite-rate sintering and is validated with experimental data. The results show that the model provides a substantial improvement over the monodisperse model and has good agreement with the two-PBE model. Additionally, the coupled CFD-PBE simulation reduces computational time and the agreement with experimental data is reasonable.
AEROSOL SCIENCE AND TECHNOLOGY
(2023)
Article
Engineering, Chemical
Hin Yan Tang, Stelios Rigopoulos, George Papadakis
Summary: The present paper investigates the impact of turbulent fluctuations on precipitation and its implications for modelling through a coupled direct numerical simulation (DNS) - population balance study. The unclosed terms in the averaged population balance equation are identified and evaluated via DNS. The comparison of average nucleation and growth rates with computed values reveals significant deviations, emphasizing the importance of fluctuations in precipitation modelling. The findings also indicate the influence of thinner reaction zones on higher Schmidt numbers but marginal effect on the product particle size distribution.
CHEMICAL ENGINEERING SCIENCE
(2023)
Article
Thermodynamics
Jannis Finke, Fabian Sewerin
Summary: At high temperatures, aluminum particles can burn exothermally in oxidizing atmospheres. The main product is aluminum oxide (alumina), which can form through two different chemical pathways. This article aims to develop a detailed modeling framework for predicting alumina smoke size distributions.
COMBUSTION AND FLAME
(2023)
Article
Engineering, Chemical
Fabian Sewerin
Summary: Population balances are used to describe dense particulate phases with particle-particle interactions. In this study, we focus on particle coagulation and develop efficient analytical formulas for evaluating source terms within a finite volume framework. These formulas eliminate the need for explicit decomposition of integration domains and are applicable to any volume-grids. The study also proposes cell-wise constant and linear reconstructions of particle volume distribution to mitigate unphysical heavy tails.
CHEMICAL ENGINEERING SCIENCE
(2023)
Article
Mechanics
Thomas Readshaw, W. P. Jones, Stelios Rigopoulos
Summary: Tabulating chemical mechanisms with artificial neural networks (ANNs) provides faster computational integration of reaction source terms in turbulent reacting flow simulations. A method is developed to ensure physical consistency of ANNs with reaction mechanisms, by conserving mass and chemical elements, and enforcing bounds on species mass fractions. The method can be applied to any reacting system and integrated into existing ANN architectures. The proposed method reduces errors and improves the accuracy of ANN predictions at minimal additional computational cost when compared to direct integration (DI) of chemical kinetics.
Article
Engineering, Chemical
Kirill Mikhaylov, Stelios Rigopoulos, George Papadakis
Summary: This study applies Proper Orthogonal Decomposition (POD) to characterize large scale coherent structures inside a stirred tank agitated by a Rushton turbine at turbulent flow conditions (Re = 30000). The four leading POD modes correspond to precessing Macro-instabilities that rotate in a direction opposite to that of the impeller. Machine Learning methods are utilized to reconstruct the dominant pair from sparse velocity measurements, and the performance improves with a larger number of sensors. A reduced order model consisting of the mean and the first two modes reconstructs the largest structures but not the finer features.
CHEMICAL ENGINEERING RESEARCH & DESIGN
(2023)
Article
Engineering, Chemical
Kirill Mikhaylov, Stelios Rigopoulos, George Papadakis
Summary: This study investigates the flow inside an unbaffled stirred tank at Re=600 and decomposes the pressure field into different components based on the temporal coefficients of velocity proper orthogonal decomposition (POD) modes. The pressure components are used to analyze the power number of individual blades and blade combinations, and a linear dynamic estimator is derived to reconstruct the 3D velocity field in real time from sparse pressure measurements. The results show that the estimator is robust to changes in operating conditions and has potential for real time control of mixing with precise feeding control.
CHEMICAL ENGINEERING SCIENCE
(2023)
Review
Thermodynamics
Don Dasun Attanayake, Fabian Sewerin, Shreyas Kulkarni, Andrea Dernbecher, Alba Dieguez-Alonso, Berend van Wachem
Summary: In a pyrolysis reactor, organic polymers from biomass or plastic waste are thermally decomposed into gases, tar or bio-oil, and char. Pyrolysis is crucial for our progress towards a circular economy as the products can be used for downstream chemical refinement or bio-derived fuels. Using CFD-DEM methodology for predictive modeling of pyrolysis reactors is gaining attention, but plastic pyrolysis remains a challenge due to incomplete understanding of melting behavior. This article provides a blueprint for describing pyrolysis process using CFD-DEM, reviews past modeling choices and assumptions, and surveys the influence of operating conditions and feedstock properties on key metrics.
FLOW TURBULENCE AND COMBUSTION
(2023)
Article
Acoustics
Soeren Schenke, Fabian Sewerin, Berend van Wachem, Fabian Denner
Summary: We investigate the amplitude modulation of acoustic waves in accelerating flows using a convective form of the Kuznetsov equation. By solving it numerically, we identify a modulation of wave amplitude driven by the flow characteristics, distinct from convective amplification. A leading-order model is derived from first principles to rationalize the observed modulation, which can be used for numerical prediction and analysis of acoustic wave behavior in accelerating flows.
JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA
(2023)
Article
Computer Science, Artificial Intelligence
Mohammed I. Radaideh, Stelios Rigopoulos, Dimitris A. Goussis
Summary: This study extends the search for optimal input selection in Machine Learning algorithms by considering the time scale that characterizes the process. It demonstrates that using the time scale that characterizes the initiation of the process as input provides better accuracy for prediction compared to other parameters. Further research is suggested to develop methodologies for selecting optimal inputs among those that characterize the process.
Article
Thermodynamics
Tianjie Ding, Stelios Rigopoulos, W. P. Jones
Summary: The objective of this work is to develop a machine learning methodology that can account for fuel blends in thermochemistry. The methodology uses artificial neural networks to predict the composition space encountered in turbulent flame simulations. It is applicable to various combustion modeling approaches and has the capability for generalization. The results show excellent agreement between the artificial neural network simulations and direct integration, indicating its potential for reducing computational costs in turbulent combustion simulations.
APPLICATIONS IN ENERGY AND COMBUSTION SCIENCE
(2022)
Article
Thermodynamics
Yifan Yang, Haodong Zhang, Linye Li, Mingming Gu, Xi Xia, Fei Qi
Summary: This paper investigates the formation of a blue whirl by controlling tangential and radial airflows. By using a unique fire whirl apparatus, the blue whirl can be formed directly upon ignition without going through the transient phase. The study also discovers new flame regimes and explores the mechanism behind the formation and transition of the blue whirl.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Xiaobin Qi, Songyan Gao, Zhiping Zhu, Qinggang Lyu, Haixia Zhang
Summary: This study experimentally investigated the propagation characteristics of reverse combustion under oxygen-limited and enriched conditions. The contribution of volatiles gas-phase oxidation and char surface oxidation to reverse combustion was evaluated. The results showed that oxygen enrichment expanded the operating range of oxygen flow rate for reverse combustion and enhanced the low-temperature oxidation of the solid fuel. The findings provide a better understanding of the driving mechanism of reverse combustion and have important implications for efficient thermal conversion of solid fuels.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Bingjie Chen, Peng Liu, Bingzhi Liu, Zhandong Wang, Xiang Gao, William L. Roberts
Summary: In this study, the low temperature oxidation of 1,2,4-trimethylbenzene was investigated using experiments and numerical simulations. The results showed the presence of toxic oxygenated aromatic compounds and proposed potential formation pathways. The numerical simulations accurately predicted the mole fractions of most compounds, but some compounds were missing.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Meng Sui, Zhiheng Zhu, Fashe Li, Hua Wang
Summary: The effect of adding ferrocene as a combustion catalyst to Jatropha biodiesel on its pyrolysis and combustion performance is investigated. The results show that adding ferrocene reduces activation energy and harmful emissions while improving combustion efficiency.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Manaf Sheyyab, Mohammed Abdulrahman, Subharaj Hossain, Patrick T. Lynch, Eric K. Mayhew, Kenneth Brezinsky
Summary: Fuel surrogates, simplified representations of complex fuels, accurately model speciation results and reaction kinetics, reproduce the ignition quality and chemical functional group compositions of their parent fuels.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Yan Wang, Shumeng Xie, Hannes Bottler, Yiqing Wang, Xinyi Chen, Arne Scholtissek, Christian Hasse, Zheng Chen
Summary: This study investigates how flow affects the ignition and transition process of a cool flame. The results show that the ignition energy determines the highest temperature and the strain rate influences the flame propagation and the transition from cool flame to hot flame.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Tanusree Chatterjee, Mengyuan Wang, Goutham Kukkadapu, Chih-Jen Sung, William J. Pitz
Summary: Cycloalkanes, including cyclohexane, are important hydrocarbons in transportation fuels. However, limited oxidation data at low-to-intermediate temperatures and inadequate predictive ability of kinetic models have hindered the understanding and improvement of cyclohexane oxidation. This study provides experimental and modeling results to develop a more accurate kinetic model for cyclohexane oxidation.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Tao Wu, Erik Hagen, Haiyang Wang, Dylan J. Kline, Michael R. Zachariah, Carole Rossi
Summary: It was found that incorporating CuO into Al/I2O5 can significantly reduce the ignition time and enhance the combustion performance. The optimum composition of 80/20 wt% of I2O5/CuO shows a 30 times shorter ignition time and produces a peak pressure and pressurization rate 4 and 26 times greater than traditional Al/I2O5. A series of characterizations helped unravel the cause of improvement and propose a reaction mechanism for this ternary Al/I2O5/CuO system. This study proposes a facile, inexpensive, and efficient way to enhance the combustion performance of Al/I2O5 biocidal nanoenergetic materials.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Mahmoud Gadalla, Shervin Karimkashi, Islam Kabil, Ossi Kaario, Tianfeng Lu, Ville Vuorinen
Summary: In this study, the flame initiation process in dual-fuel spray assisted combustion is explored through scale-resolved simulations, providing numerical evidence on the initiation of premixed flames. It is found that there is a transient mixed-mode combustion phase after ignition, followed by a primarily deflagrative combustion mode. The interactions between turbulence and premixed flame front are characterized in the corrugated regime.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Neeraj Kumar Pradhan, Arindrajit Chowdhury, Debasis Chakraborty, Neeraj Kumbhakarna
Summary: In this study, a modified model for predicting the burn rate of composite solid propellants is proposed. The model has been validated against experimental and theoretical results, and it outperforms existing models in all cases considered. The model is highly robust and provides results quickly, making it highly efficient in terms of time, effort, and computational resources.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Lili Ye, Zhihe Zhang, Fan Wang, Xiaodong Wang, Yiming Lu, Lei Zhang
Summary: This study investigated the pyrolysis mechanism of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) explosive using ab initio and kinetic modeling simulations. The results showed that N-NO2 bond fission and C-H beta-scission are important channels in the decomposition of HMX.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Andrei N. Lipatnikov, Hsuchew Lee, Peng Dai, Minping Wan, Vladimir A. Sabelnikov
Summary: This study investigates the importance of thermodiffusive and hydrodynamic instabilities of laminar flames in turbulent flows through numerical simulations. The analysis suggests that laminar flame instabilities play a minor role at sufficiently high Karlovitz numbers.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Shijie Xu, Yue Qiu, Leilei Xu, Jianqing Huang, Shen Li, Elna J. K. Nilsson, Zhongshan Li, Weiwei Cai, Marcus Alden, Xue-Song Bai
Summary: Metal powder is a promising carbon-free and recyclable energy carrier. In this study, a computational model for the combustion and phase change of micron-sized iron particles was proposed and validated. The model successfully captures the melting, surface reactions, cooling, and solidification processes. The study also reveals a two-stage solidification phenomenon and identifies a diffusion-controlled mechanism during the melting process. The reaction between iron and CH4/O2/N2 flame products is found to play a significant role in the iron combustion process.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Khalid Aljohani, Abd El-Sabor Mohamed, Haitao Lu, Henry J. Curran, S. Mani Sarathy, Aamir Farooq
Summary: This study investigates the impact of exhaust gas recirculation (EGR) and NOx on the ignition delay time of oxygenated gasoline. A gasoline surrogate model is developed and the experimental data are useful for predicting fuel ignition behavior in internal combustion engines. The results show that EGR inhibits gasoline reactivity, while NOx has a promoting effect at high temperatures. This research is important for understanding the combustion behavior of gasoline in engines.
COMBUSTION AND FLAME
(2024)
Article
Thermodynamics
Chengcheng Ao, Jia Yan, Tong Yan, Lidong Zhang, Pan Wang
Summary: This study investigates the inhibitory effect of ammonia blended with hydrocarbon fuels on soot formation. The results show that there is a chemical interaction between ammonia and polycyclic aromatic hydrocarbons (PAHs), blocking the formation of larger PAHs.
COMBUSTION AND FLAME
(2024)