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
Thermodynamics
M. Richter, R. Schultheis, J. R. Dawson, A. Gruber, R. S. Barlow, A. Dreizler, D. Geyer
Summary: Chemical energy vectors, such as ammonia (NH3), will play a crucial role in the global energy system transition due to their advantages in storing energy in gaseous, liquid, or solid fuels. Ammonia is a promising candidate as it is carbon-free, can be stored at moderate pressures, and already has a developed distribution infrastructure. By partially cracking ammonia into hydrogen (H2) and nitrogen (N2) prior to combustion, the combustion properties of ammonia can be improved, leading to enhanced flame stability and resistance to strain-induced blow-out compared to methane.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Chemistry, Physical
Ksenia N. Osipova, Oleg P. Korobeinichev, Andrey G. Shmakov
Summary: This paper presents experimental data on the flame structure of laminar premixed ammonia and ammonia/hydrogen flames at different equivalence ratios and the laminar flame speed of ammonia/hydrogen flames. Experimental data were compared with modeling results obtained using detailed chemical-kinetic mechanisms of ammonia oxidation. The study shows that slightly rich conditions and increasing pressure can reduce NO formation in ammonia flames.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2021)
Article
Thermodynamics
Daniel E. Thomas, Krishna P. Shrestha, Fabian Mauss, William F. Northrop
Summary: This study investigates the combustion of ammonia-hydrogen fuel mixtures and provides an improved kinetic mechanism for modeling ammonia combustion. The measured extinction strain rate and flame NO concentration are compared to various models, and it is found that the previously published models do not accurately predict the experimental results. By updating the reaction rate parameters, the improved model shows better agreement with the experimental data, especially in predicting NO concentration.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
K. N. Osipova, S. Mani Sarathy, O. P. Korobeinichev, A. G. Shmakov
Summary: The work investigates laminar premixed formic acid flames and flame speed, using experimental and kinetic modeling methods. Different chemical kinetic mechanisms were used to simulate flame structure and speed, with hydrogen consumed slower than formic acid due to its dual role as fuel and intermediate product. Despite satisfactory predictions for most components, discrepancies were identified in predicting formaldehyde concentrations.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2021)
Article
Thermodynamics
Yong Tang, Qiang Yao, Marien Simeni Simeni, Igor V. Adamovich
Summary: This study investigates the response of counterflow diffusion flames to sub-breakdown DC and AC electric fields, as well as their superposition with ns pulse discharge waveforms in the plane-to-plane electrode geometry. The results show that sub-breakdown DC and low-frequency AC electric fields displace the flame towards the grounded electrode. However, as the AC frequency increases, the flame response becomes less pronounced. Combining a nanosecond pulse discharge with a sub-breakdown DC field generates a diffuse plasma across the entire gap. The rapid plasma self-shielding in the plane-to-plane geometry prevents the detectable flame displacement enhancement observed in other electrode geometries.
COMBUSTION AND FLAME
(2022)
Article
Thermodynamics
Martin Rieth, Andrea Gruber, Forman A. Williams, Jacqueline H. Chen
Summary: In this study, direct numerical simulations were used to investigate the local effects of molecular diffusion on the overall burning rates of fuel-lean turbulent premixed hydrogen-enriched flames. The analysis revealed that diffusion of hydrogen species can remain the rate-controlling processes even at high turbulence intensity.
COMBUSTION AND FLAME
(2022)
Article
Thermodynamics
Xu Wen, Louis Dressler, Andreas Dreizler, Amsini Sadiki, Johannes Janicka, Christian Hasse
Summary: Large-eddy simulations were conducted for turbulent methane-hydrogen flames with different modeling approaches, showing varied predictions of flame properties in different regions. The performance of the flamelet models was explored by analyzing the differential diffusion parameter.
COMBUSTION AND FLAME
(2021)
Article
Thermodynamics
F. H. Vance, L. P. H. de Goey, J. A. van Oijen
Summary: Hydrogen flames have a higher tendency to flashback compared to methane flames, which can lead to strong thermal stresses in burners and hinder their performance. Studies have shown that traditional flashback correlation methods are not effective in accounting for stretch induced preferential diffusion effects, and a new Karlovitz number definition has been introduced to better understand and predict flashback limits.
COMBUSTION AND FLAME
(2022)
Article
Energy & Fuels
Chinonso Ezenwajiaku, Midhat Talibi, Ramanarayanan Balachandran
Summary: This study focuses on the formation and growth characteristics of polycyclic aromatic hydrocarbons (PAHs) in inverse diffusion flames of various hydrocarbon fuels enriched with H-2. The results show that only the addition of H-2 to CH4 significantly reduces PAH concentrations as the flame length increases. Additionally, the growth rate of PAHs remains relatively stable regardless of the fuel bonding, molecular structure, and H:C ratio.
Article
Chemistry, Physical
Xin Hui, Dongsheng Zheng, Wendi Tan, Xin Xue, Weitao Liu
Summary: The effects of H2 addition on soot formation in counterflow diffusion nheptane flames were investigated. Three effects, including chemical, thermal, and dilution, were studied by adding H2, He, and Ar. Soot volume fractions were measured using LE-calibrated LII technique, and flame temperatures were measured using OH-TLAF method and a thermocouple. Numerical simulations with a detailed mechanism and soot model showed good agreement with experimental data. The results demonstrated that H2 addition can significantly reduce soot formation. It was also observed that chemical and dilution effects suppress soot formation, while the thermal effect with increasing flame temperature promotes soot formation. Kinetic analysis suggested that the HACA growth rate could be the dominant factor controlling soot formation through the three effects due to H2 addition.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2023)
Article
Thermodynamics
Xu Wen, Thorsten Zirwes, Arne Scholtissek, Hannes Boettler, Feichi Zhang, Henning Bockhorn, Christian Hasse
Summary: This study focuses on analyzing the flame structure and modeling the composition space of a multidimensional premixed hydrogen flame transitioning from a laminar stable condition to a thermodiffusively unstable state. A new flamelet tabulation method is proposed to address the modeling issues of differential diffusion, strain rate, and curvature in the thermodiffusively unstable flame. The validity of the proposed method is evaluated based on representative flamelets with varying strain rates and curvatures. The results demonstrate the advancement achieved by the proposed flamelet model and identify key trajectory variables for characterizing the flame structure's response to strain rate and curvature.
COMBUSTION AND FLAME
(2022)
Article
Thermodynamics
Martina Baroncelli, Qian Mao, Heinz Pitsch, Nils Hansen
Summary: This study presents insights into the chemical mechanisms responsible for the formation of one- and two-ring aromatic species under non-premixed conditions through a combination of experimental and numerical analysis. The experimental dataset was used to trace the formation of aromatic structures and identify the underlying fuel-dependent molecular-weight growth chemistry. Analysis of the formation pathways of aromatic species predicted by established chemical mechanisms was supported by measured relative changes in species concentrations and numerical simulations. The study found that propargyl and allyl radicals play significant roles in benzene formation, with propargyl addition to benzyl radicals identified as the main contribution to naphthalene production. Formation pathways involving sequences of acetylene and methyl addition to aromatic radicals were found to be responsible reactions for trends in phenylacetylene and -C2H substituted naphthalene.
COMBUSTION AND FLAME
(2021)
Article
Thermodynamics
Bo Zhou, Jonathan H. Frank
Summary: The study investigates the effects of heat release on the interactions between vorticity and strain rate in turbulent premixed counterflow flames, revealing that heat release increases the misalignment between vorticity and strain rate, while density variations without heat release enhance their alignment. In regions with the largest vorticities, both reacting and non-reacting counterflows show an increase in vorticity-strain rate alignment.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2021)
Article
Thermodynamics
Wang Han, Arne Scholtissek, Felix Dietzsch, Christian Hasse
Summary: This study evaluates the effects of differential diffusion (DD) on flame structure, chemical reactions, and tangential diffusion in turbulent and laminar H2 combustion simulations. It is found that conditioning the thermochemical state on Z Bilger helps to capture DD effects and mitigate the relative contribution of tangential diffusion, making Z Bilger more advantageous for flamelet modeling. DD effects persist under turbulent conditions, primarily manifesting as thermal and chemical effects rather than transport effects, suggesting the conventional DD parameter may not be suitable for comprehensively characterizing such effects.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2021)
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)