Article
Energy & Fuels
Shixing Wang, Zhihua Wang, Ayman M. Elbaz, Yong He, Chenlin Chen, Yanqun Zhu, William L. Roberts
Summary: The study found that increasing the hydrogen mole fraction or decreasing the CO2 mole fraction in the fuel can increase the combustion speed of syngas under high pressure conditions. CO2 dilution and CH4 addition were shown to decrease the overall reaction order of syngas flames by reducing the adiabatic flame temperature, leading to lower flame speeds.
Article
Energy & Fuels
Gyu Jin Hwang, Dong Seok Jeon, Nam Il Kim
Summary: In this study, the lift-off heights of propane and butane flames were measured to determine the effective Schmidt numbers and diffusivities. A triangle regime for stable laminar lifted flames was introduced and its three limiting mechanisms were explained. An additional flame stabilization mode was found for larger tube diameters and higher pressures. A revised fuel concentration gradient that can be used at elevated pressures was proposed, and the relationship between the revised fuel concentration gradient and the flame propagation velocity was revealed.
Article
Energy & Fuels
Francis Oppong, Zhongyang Luo, Xiaolu Li, Yang Song, Cangsu Xu, Abdullatif Lacina Diaby
Summary: This study investigated the combustion characteristics of ethyl acetate/hydrogen/air premixed flames. It was found that the laminar burning speed increased significantly with the addition of hydrogen. Furthermore, an increase in hydrogen concentration and initial pressure led to flame thinning and curvature effects, causing flame instability and cellularity.
Article
Energy & Fuels
Xiaoman Li, Wu Xu, Ya Li, Yong Jiang
Summary: This study experimentally investigated the laminar burning velocities, Markstein lengths, and flame instability of DMC under different pressures. It was found that LBVs decrease with increasing pressure and reach peak values at an equivalence ratio of approximately 1.1. Sensitivity analysis revealed that increased pressure facilitates certain chain termination reactions, leading to a reduction in LBVs.
Article
Thermodynamics
Elie Antar, Julien Delavande, Etienne Robert
Summary: The combustion of multi-fuel mixtures is experimentally studied in unstrained diffusion flames for the first time, eliminating parasitic hydrodynamic effects. The study investigates H2-CO-CH4 fuels diluted in CO2 to understand diffusive-thermal instabilities. Flame stability and properties of cellular-pulsating instabilities are characterized by measuring various parameters. Effective fuel Lewis number and Damkohler number are used to map the observed instabilities.
COMBUSTION AND FLAME
(2023)
Article
Engineering, Environmental
Xufeng Yang, Wen Yang, Changlin Liu, Minggao Yu, Shixin Han
Summary: This study conducted experiments in two closed ducts to comparatively study the explosion behavior of premixed syngas-air mixtures. The results showed that the development of the flame's structure is predictable in one duct, but complex in the other. Increasing both the hydrogen volume fraction and the aspect ratio of the duct increases the amplitude of the flame oscillation. The flame tip speed was found to have a strong correlation with overpressure profiles.
PROCESS SAFETY AND ENVIRONMENTAL PROTECTION
(2023)
Article
Thermodynamics
Shixing Wang, Ayman M. Elbaz, Zhihua Wang, William L. Roberts
Summary: Ammonia is a promising carbon-free fuel and hydrogen carrier for renewable energy, with turbulent flame speed found to increase with oxygen content but turbulent-to-laminar flame speed ratio decreasing. The study presents correlations of turbulent flame speed based on Karlovitz number and Damkohler number, showing that ammonia/oxygen/nitrogen mixtures can achieve similar turbulent flame speed as methane/air.
COMBUSTION AND FLAME
(2021)
Article
Chemistry, Physical
Guo-Peng Zhang, Guo-Xiu Li, Hong-Meng Li, Jian-Bin Cao
Summary: This study investigated the propagation of hydrogen-rich syngas premixed flame and found that the mixing process of turbulent flow and the stretching effect of the flame front significantly influenced its propagation speed. The effects of flame inherent instability, diffusional-thermal instability, and hydrodynamic instability on flame acceleration process were also observed. These findings are important for the development of hydrogen-rich syngas as an alternative energy source.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2023)
Article
Energy & Fuels
Linyuan Huang, Sheng Huang, Yebing Mao, Bo Wang, Quan Zhu, Rongpei Jiang
Summary: This work develops a new surrogate fuel for RP-3 kerosene and validates its consistency with the original fuel in terms of combustion characteristics through experiments and kinetic modeling. In addition, the flame propagation process and instability of the fuel under high temperature and pressure conditions were analyzed.
Article
Thermodynamics
Shangkun Zhou, Wenjun Yang, Houzhang Tan, Qiwei An, Jinhua Wang, Hongchao Dai, Xiaoxiao Wang, Xuebin Wang, Shuanghui Deng
Summary: Ammonia (NH3) plays a crucial role in large-scale storage and long-distance transportation of renewable energy. Co-firing with syngas and bio-syngas, along with increasing the initial temperature of reactants, are effective methods to enhance the reactivity of NH3 flames. However, current kinetic models lack accuracy in temperature dependence, indicating a need for further research in this area.
COMBUSTION AND FLAME
(2021)
Article
Thermodynamics
Ksenia N. Osipova, S. Mani Sarathy, Oleg P. Korobeinichev, Andrey G. Shmakov
Summary: This paper presents the importance of ammonia and ammonia/hydrogen combustion chemistry in engine and gas turbine systems, and investigates the structure of the NH3/H2/O2/Ar premixed flame, the formation of nitrogen compounds, and the control strategy of NO emissions through experimental data and numerical simulation.
COMBUSTION AND FLAME
(2022)
Article
Engineering, Environmental
Jintao Xu, Xiangfeng Chen, Haipeng Jiang, Wei Gao
Summary: The flame behaviors and pressure characteristics of vented hydrogen-air explosions at elevated static activation pressures were investigated in this study. It was found that the maximum flame lengths and widths increased with the increase in venting diameters and equivalent ratios by controlling the concentration of vented unburned gas. Non-dimensional formulas were established to predict the maximum flame length and width with a relative error within 50%. The pressure curves exhibited notable oscillations, and an empirical formula was proposed to predict the internal pressure with a relative error within 25%. The mechanism of external explosions was revealed using BOS images, and it was found that the intensity of external explosions depended on the external flow field intensity and the concentration of unburned gas.
PROCESS SAFETY AND ENVIRONMENTAL PROTECTION
(2022)
Article
Thermodynamics
Natarajan Rajesh, Shu Zheng, Chockalingam Prathap
Summary: The objective of this study was to measure the unstretched laminar burning velocity (LBV) and burned gas Markstein length (Lb) of oxy-n-dodecane mixtures using the spherically outwardly propagating flame (SPF) method. Mixtures with different compositions were analyzed under varying conditions, and the LBV was simulated using different mechanisms. The predicted results showed good agreement with the experimental measurements.
COMBUSTION AND FLAME
(2023)
Article
Energy & Fuels
Gyu Jin Hwang, Dong Seok Jeon, Nam Il Kim
Summary: The effects of pressure on the characteristics of propane flame were examined, and it was found that extending the pressure range allows for more precise and abundant experimental results, revealing the general features of flame structures and explaining the non-monotonic variation in flame height and variations in flame structure during the transition from laminar lifted flame to turbulent lifted flame.
Article
Thermodynamics
Wenyu Li, Chun Zou, Hong Yao, Qianjin Lin, Rui Fu, Jianghui Luo
Summary: Oxy-fuel combustion is a promising strategy for carbon capture. The existing syngas combustion models have been improved to enhance the prediction accuracy of ignition delay time and flame propagation speed, and the chemical and physical effects of CO2 as a diluent have been investigated.
COMBUSTION AND FLAME
(2022)
Article
Thermodynamics
Muye Feng, Yi Wang, Kai H. Luo
Summary: This study uses reactive molecular dynamics simulation to investigate the kinetics and catalytic mechanisms of the thermal decomposition of RDX on GO. The presence of GO enhances the decomposition reaction of RDX and the catalytic effect is better at low temperatures. The catalytic capabilities of GO primarily come from its functional groups that promote both the initiation and intermediate reactions. The proposed catalytic mechanisms can be applied to similar energetic materials.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Zhongze Bai, Xi Zhuo Jiang, Kai H. Luo
Summary: Coal splitting and staging is a promising technology for reducing NOx emissions from coal combustion. In this study, molecular dynamics simulations were conducted to investigate the reaction mechanisms of NO removal by nitrogen-containing species (HCN and NH 3 ) in coal pyrolysis gas. The effects of temperature on NO consumption and N 2 formation were analyzed, and control strategies for the pyrolysis and reburn processes were proposed. This research provides new insights into the mechanisms of NO reduction and can help optimize the operating parameters to decrease NOx emissions.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Ying Wang, Qian Mao, Zhanyuan Wang, Kai H. Luo, Lei Zhou, Haiqiao Wei
Summary: In this study, the reaction mechanisms of large polycyclic aromatic hydrocarbons (PAHs) and the interactions between O-2, NO, and NO2 were investigated using ReaxFF molecular dynamics simulations. It was found that the O radical is the key species for PAH oxidation and that NO2 is a stronger oxidizer compared to NO and O-2, significantly accelerating PAH oxidation. This research provides fundamental insights for designing strategies to inhibit soot and NOx emissions at the source.
COMBUSTION AND FLAME
(2023)
Article
Energy & Fuels
Qichang Wang, Ran Yu, Dekui Shen, Qian Liu, Kai Hong Luo, Chunfei Wu, Sai Gu
Summary: In this study, ginkgo leave-based carbon was used as a precursor to prepare nitrogen/sulfur/phosphorus co-doped carbon matrix loaded with cobalt phosphide. It was found that the nitrogen/sulfur heteroatoms from ginkgo leaves can accelerate electron transfer and adjust the electronic structure of the catalyst, resulting in improved electrocatalytic activity.
Article
Energy & Fuels
Zhongze Bai, Xi Zhuo Jiang, Kai H. Luo
Summary: This study investigates the effects of electric field on fuel-NOx formation during pyridine combustion and fills the knowledge gaps regarding the influence of electric field on fuel-NOx emissions.
Article
Energy & Fuels
Jing Wang, Xi Zhuo Jiang, Kai H. Luo
Summary: Ammonia has gained attention as a carbon-free fuel, but further research is needed to understand its combustion mechanisms under different conditions. In this study, reactive molecular dynamics simulations were conducted to study ammonia/methane combustion at high temperature and pressure. The results showed that high temperature accelerated ammonia consumption and affected the formation of nitrogen oxides (NOx), while high pressure also accelerated ammonia consumption and influenced NOx formation. By tracing the trajectories of reacting atoms, the reaction pathways for ammonia/methane combustion under high pressure were generated. Comparing with existing combustion mechanisms, new intermediates and elementary reactions were identified. The study also calculated the activation energies for several important elementary reactions, which were consistent with previous combustion kinetics studies. The study demonstrated the feasibility of generating reaction networks and revealed in-depth reaction mechanisms under extreme conditions using reactive molecular dynamics.
Article
Thermodynamics
Zhen Wang, Timan Lei, Kai Hong Luo
Summary: The paper presents a lattice Boltzmann (LB) method for premixed and nonpremixed combustion simulations with nonreflective boundary conditions. The approach employs different sets of distribution functions for flow, temperature, and species fields, which are fully coupled. The LB method is validated against various benchmarks and shows capability for low Mach number combustion with potential applications in various fields.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Timan Lei, Kai H. Luo
Summary: This study establishes a lattice Boltzmann (LB) model to simulate two important aspects of in-situ combustion (ISC): coke formation and combustion at the pore scale. The results show that the LB model accurately captures coke combustion properties and yields important findings on coke formation and two-step combustion. These results contribute to the improved understanding and development of ISC.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Yunfeng Xu, Qian Mao, Ying Wang, Kai H. Luo, Lei Zhou, Zhanyuan Wang, Haiqiao Wei
Summary: In this study, the effect of NH3 on the growth of polycyclic aromatic hydrocarbons (PAHs) was investigated using simulations and quantum chemistry calculations. The results showed that NH3 addition slowed down the growth of large carbon-containing species in the C2H4/O2 system. A novel path with HCN addition was discovered, which inhibited PAH growth compared to the conventional Hydrogen-Abstraction-Carbon-Addition (HACA) path via C2H2 addition. The study provides fundamental insights into the inhibition of PAH growth due to NH3 addition.
COMBUSTION AND FLAME
(2023)
Article
Water Resources
Junyu Yang, Timan Lei, Geng Wang, Qianghui Xu, Jin Chen, Kai H. Luo
Summary: This study establishes a lattice Boltzmann (LB) method with phase change to simulate salt precipitation during brine evaporation. The proposed LB models consider gas-brine multiphase flow, brine evaporation, salt concentration evolution, salt precipitate nucleation, and growth. The numerical simulations successfully reproduce the typical salt precipitation patterns observed in experiments and investigate the competition mechanisms between nucleation and growth. Additionally, the effects of gas injection rate on salt precipitation performance are clarified. The proposed LB models have comprehensive consideration of multiphase brine evaporation, salt species transport, nucleation, and growth, which have not been done in previous studies. This work has important implications for practical engineering applications such as CO2 sequestration.
ADVANCES IN WATER RESOURCES
(2023)
Article
Mechanics
Jin Chen, Geng Wang, Junyu Yang, Timan Lei, Kai H. Luo
Summary: In this paper, the transport of miscible fluids in porous media is investigated using a multiple-relaxation-time lattice Boltzmann method, with a focus on interface instabilities and their dependence on density difference, viscosity contrast, and injection velocity. It is found that increasing viscosity contrast or injection velocity can suppress density fingering, while a moderate viscosity contrast and high injection velocity can stabilize it. Additionally, high viscosity contrast and injection velocity can jointly trigger viscous fingering. The results are quantitatively analyzed to classify five different flow patterns and provide guidance for controlling flow stability under different operating conditions.
Review
Thermodynamics
Qian Mao, Muye Feng, Xi Zhuo Jiang, Yihua Ren, Kai H. Luo, Adri C. T. van Duin
Summary: Molecular dynamics (MD) is a computational method widely used in fundamental research, and it has recently been applied in engineering as a predictive method for material properties and physicochemical processes. This paper provides a comprehensive overview of MD applications in combustion and energy systems, covering a wide range of topics such as fuel oxidation, catalytic combustion, nanoparticle synthesis, and heat transfer.
PROGRESS IN ENERGY AND COMBUSTION SCIENCE
(2023)
Article
Chemistry, Physical
Zhongze Bai, Xi Zhuo Jiang, Kai H. Luo
Summary: Carbon dioxide (CO2) electroreduction by metal-nitrogen-doped carbon (MNC) catalysts is a promising method to convert CO2 molecules into value-added chemicals. This research focuses on the behaviors of single and dual-atom Cu catalysts during the CO2 electroreduction process. The study identifies two structures, CuNC-4-pyridine and CuCuNC-4a, that are beneficial for the generation of C-2 chemicals with high stability.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Dingyu Hou, Geng Wang, Jingqi Gao, Kai H. Luo
Summary: Flame spray pyrolysis is a favorable method to synthesize LiNi1-x-yCoxMnyO2 (NCM) materials, which are promising cathode materials for Li-ion batteries. However, the formation mechanisms of NCM nanoparticles in flame spray pyrolysis are not well understood.
Article
Energy & Fuels
Qichang Wang, Jing Zhao, Ran Yu, Dekui Shen, Chunfei Wu, Kai Hong Luo, Lian-Hua Xu
Summary: The distribution of nitrogen species in carbon materials can be adjusted by varying the pyrolysis temperature, leading to optimization of the valence band structure and improved catalytic activity.
JOURNAL OF THE ENERGY INSTITUTE
(2023)
