Article
Thermodynamics
Tao Shu, Yuan Xue, Wenkai Liang, Zhuyin Ren
Summary: The modified models MLC and MNQ show improved accuracy in predicting flame speeds and Markstein lengths, especially for lean hydrogen/air flames. As pressure increases, both unmodified and modified models can reduce uncertainty and the impact of finite flame structure becomes less significant.
COMBUSTION AND FLAME
(2021)
Article
Engineering, Environmental
Lu-Qing Wang, Dai-Guo Chen, Hong-Hao Ma
Summary: The laminar burning velocity and cellular instabilities of premixed flame in H2-N2O mixtures were experimentally studied at different equivalence ratios and initial pressures. It was found that both the laminar burning velocity and Markstein length increase with the equivalence ratio. The most unstable flames were observed at phi= 0.4-0.6 due to the combined effects of thermal-diffusion and hydrodynamic instabilities. At lower initial pressure, the flame front is smooth, while at higher initial pressure, diffusion-thermal and hydrodynamic instabilities dominate the cellular structure of the flame front.
PROCESS SAFETY AND ENVIRONMENTAL PROTECTION
(2023)
Article
Thermodynamics
Michael J. Hegetschweiler, Lukas Berger, Raik Hesse, Joachim Beeckmann, Chaimae Bariki, Heinz Pitsch, Gregory T. Linteris
Summary: This study investigates data reduction techniques for measuring the laminar burning velocities of R32(CH2F2)-air mixtures using a constant volume combustion device. The accuracy of different data reduction models is assessed by comparing them with results from detailed numerical simulations. The effects of stretch, radiation, and post-processing methodologies on the accuracy of the results are also explored and quantified. The study highlights the importance of using the correct radiation model in the data reduction process.
COMBUSTION AND FLAME
(2023)
Article
Energy & Fuels
Ya Li, Wu Xu, Yong Jiang, K. M. Liew
Summary: Recent investigation suggest that CO2, N2, and He have varying effects on the laminar burning velocity (LBV) and cellular instability of 2-MTHF-air flames. The most chaotic state occurred at approximately phi = 1.3 under all test conditions. CO2 and He showed similar abilities to delay the onset of cellular instability, while N2 showed a weaker ability to do so.
Article
Chemistry, Physical
J. Grune, K. Sempert, M. Kuznetsov, T. Jordan
Summary: This paper presents experimental results on spherical and cylindrical flame propagation in pre-mixed H2/air-mixtures in different geometries, analyzing the structure and propagation of the flames. The study discusses self-acceleration phenomena in unconfined and unobstructed pre-mixed H2/air flames.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2021)
Article
Thermodynamics
Xinlu Han, Marco Lubrano Lavadera, Christian Brackmann, Zhihua Wang, Yong He, Alexander A. Konnov
Summary: The formation of nitric oxide (NO) in methane (CH4) flames has been extensively studied, but discrepancies between simulations using different kinetic mechanisms and experimental results persist. Experimental data was collected for NO formation in post-flame zones of CH4+O2+N2 flames with varying oxygen ratios. Analysis showed that thermal-NO production plays a key role in the increase of NO mole fraction in stoichiometric and fuel-lean flames as oxygen ratio increases.
COMBUSTION AND FLAME
(2021)
Article
Thermodynamics
Michael J. Hegetschweiler, John L. Pagliaro, Lukas Berger, Raik Hesse, Joachim Beeckmann, Chaimae Bariki, Heinz Pitsch, Gregory T. Linteris
Summary: The study investigated the burning velocities of mixtures of R-32 with air at different equivalence ratios, finding that the effects of stretch and radiation occur simultaneously. Different data reduction approaches had significant effects on the burning velocities inferred from experiments and simulations, and a new flame radius tracking method provided improved agreement with predicted gas velocity variations.
COMBUSTION AND FLAME
(2022)
Article
Energy & Fuels
Ya Li, Yong Jiang, Wu Xu, K. M. Liew
Summary: In this study, the combustion characteristics and stability of 2-butanone were investigated experimentally and theoretically. It was found that the laminar burning velocity and Markstein length of 2-butanone decreased with increasing pressure. The experimental data were well predicted by the applied kinetic models. The onset of cellular instability of 2-butanone flames was influenced by both pressure and equivalence ratio.
Article
Thermodynamics
D. A. Knyazkov, T. A. Bolshova, V. M. Shvartsberg, A. A. Chernov, O. P. Korobeinichev
Summary: This paper investigates the laminar burning velocity and structure of methyl methacrylate flames with and without trimethylphosphate additives. The study aims to develop a predictive gas-phase chemical kinetic model for flame inhibition of polymethyl methacrylate by phosphorus-containing fire retardants. The experimental and numerical results validate the combustion mechanism and discuss the performance of the kinetic model in predicting the flame inhibition.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2021)
Article
Energy & Fuels
Huaqiang Chu, Longkai Xiang, Shun Meng, Wenlong Dong, Mingyan Gu, Zhihu Li
Summary: Experimental and numerical results showed that as the equivalence ratio increased, the laminar burning velocity, intermediate radicals, and NOx emissions exhibited a trend of increasing first and then decreasing. Under the same equivalence ratio, increasing the N-2 doping ratio resulted in a decrease in the mole fraction of intermediate radicals and NOx.
Article
Energy & Fuels
Tao Shu, Yuan Xue, Zijun Zhou, Zhuyin Ren
Summary: Experimental investigation of flame properties in ammonia/methane/air mixtures shows significant influence of gas composition and pressure on flame speeds and flammability limits. Linear correlation between flame speed and methane volume fraction is observed, with accurate prediction using Okafor et al. mechanism.
Article
Chemistry, Physical
Berk Can Duva, Elisa Toulson
Summary: The fundamental combustion characteristics of H-2/air flames with the addition of actual H-2/air combustion residuals were examined experimentally and numerically. The results showed that the flame speed and adiabatic flame temperature decreased linearly with increasing diluent level, while the change in burned gas Markstein length was more complex.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2022)
Article
Energy & Fuels
Runfan Zhu, Xinlu Han, Ziyue Zhang, Yong He, Zhihua Wang
Summary: This study investigates the laminar burning velocities of NH3/CH4/H2S/air flames and explores the effect of H2S addition on flame propagation. The experimental results show that H2S addition decreases the flame speed, and the kinetic analysis reveals that the elevated H2S content significantly impacts the radicals pool in the flame. Reactions involving S-containing species become important for flame speed determination under high H2S content.
Article
Thermodynamics
Hongchao Dai, Jinhua Wang, Xiao Cai, Shouguo Su, Haoran Zhao, Zuohua Huang
Summary: This study presents the accurate laminar burning velocity, turbulent burning velocity, and their correlations for ammonia/methane/air propagating spherical flames. The results indicate that the turbulent burning velocity decreases with the ammonia content, while the normalized turbulent burning velocity increases. It is also found that the turbulent burning velocity of ammonia flame can be expressed using the correlation of Karlovitz and Damkohler numbers.
COMBUSTION AND FLAME
(2022)
Article
Engineering, Chemical
Maria Mitu, Venera Giurcan, Codina Movileanu, Domnina Razus, Dumitru Oancea
Summary: The paper investigates the laminar combustion velocities of N-2-diluted CH4-N2O flames under different conditions to provide useful information for the design of safety devices and recommendations.
Article
Thermodynamics
Chinmoy K. Mohapatra, David P. Schmidt, Brandon A. Sforozo, Katarzyna E. Matusik, Zongyu Yue, Christopher F. Powell, Sibendu Som, Balaji Mohan, Hong G. Im, Jihad Badra, Mathis Bode, Heinz Pitsch, Dimitrios Papoulias, Kshitij Neroorkar, Samir Muzaferija, Pedro Marti-Aldaravi, Maria Martinez
Summary: The internal details of fuel injectors have a significant impact on emissions from gasoline direct injection engines, but understanding the impact of injector design features is currently limited due to challenges in observing and modeling internal flows. This study used five different modeling approaches to simulate the engine combustion network Spray G injector and compared the results with experimental measurements. While the models were able to accurately predict mass flow rate through the injector, there were variations in the accuracy of other features, such as plume width and fuel mass distribution.
INTERNATIONAL JOURNAL OF ENGINE RESEARCH
(2023)
Article
Thermodynamics
Lukas Berger, Michael Grinberg, Boyung Juergens, Pasquale Eduardo Lapenna, Francesco Creta, Antonio Attili, Heinz Pitsch
Summary: In this study, the contribution of each instability mechanism in lean hydrogen/air flames is quantified separately. The analysis shows that the thermodiffusive instability dominates the flame dynamics. If differential diffusion is suppressed, the flame exhibits reduced instability growth rates, whereas a wide range of unstable wave numbers is observed when differential diffusion is present. The thermodiffusive instability significantly affects the flames' consumption speed, while the consumption speed enhancement caused by the hydrodynamic instability is smaller. Moreover, the increase in surface area due to wrinkling is strongly diminished if one of the two instability mechanisms is missing.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Raik Hesse, Chaimae Bariki, Michael J. Hegetschweiler, Gregory T. Linteris, Heinz Pitsch, Joachim Beeckmann
Summary: This study investigates the near-limit flames of the low-GWP refrigerant difluoromethane (CH2F2) with nitrogen-enriched oxidizer mixtures. The potential and limitations of two widely used flame speed measurement methods, optical flame speed measurement and flame speed determination from pressure rise, are evaluated for ultra-slow combustion. Recommendations for extracting flame speed data are derived, taking into account the effects of stretch on the optical method and the pressure method.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Maximilian Hellmuth, Florence Cameron, Sebastian Faller, Leona Schmueckert, Bingjie Chen, Yihua Ren, Heinz Pitsch
Summary: Bio-hybrid fuels, which combine bio-based feedstocks and carbon dioxide with renewable electricity, offer a carbon-neutral and low-emissions solution for the transportation sector. In this study, the impact of 1,3-dioxolane on soot formation in ethylene counterflow diffusion flames was investigated. The addition of 1,3-dioxolane was found to have a synergistic effect on soot formation, with a maximum at 10% fuel mole fraction.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Florence Cameron, Yihua Ren, Sanket Girhe, Maximilian Hellmuth, Albrecht Kreischer, Qian Mao, Heinz Pitsch
Summary: Oxygenated fuels, such as DMC and MeFo, have the potential to be used as gasoline substitutes to store renewable energy. However, the impact of fuel blending on soot formation is not well understood. This study investigated the soot formation in ethylene-based and acetylene-based fuels blended with DMC and MeFo in laminar counterflow diffusion flames. The results showed that blending DMC enhanced soot formation in ethylene-based flames, while blending MeFo reduced soot production. The findings were supported by a reaction pathway analysis based on chemical kinetic modeling.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Peng Liu, Bingjie Chen, Anthony Bennett, Heinz Pitsch, William L. Roberts
Summary: This study investigates the influence of hydrogen cyanide (HCN) on polycyclic aromatic hydrocarbons (PAH) and soot formation during coal, nitrogen-rich biomass, and ammonia combustion. The experimental results show that the addition of HCN increases the formation of benzene but decreases the formation of PAH. This is attributed to the formation of N-containing PAH (NPAH) through HCN-PAH interaction, which competes with the pathways of C2H2 addition to PAH. The study also reveals that the cyclization for the growth of a new aromatic ring is challenging in the 1-naphthyl radical + HCN system due to a high energy barrier.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Tao Li, Bo Li, Pooria Farmand, Andreas Dreizler, Heinz Pitsch, Benjamin Boehm
Summary: Motion and swelling behavior of single bituminous coal particles during volatile combustion were investigated using a combined experimental and numerical approach. Measurements with high temporal and spatial resolutions provided insights into the interactions of particles with flow and flame. The behavior of particles, including acceleration and rotation speed, was found to be dependent on particle size and devolatilization process.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Chaimae Bariki, Fabien Halter, Raik Hesse, Christian Chauveau, Heinz Pitsch, Joachim Beeckmann
Summary: Nitrogen is used as an alternative to CO2 in the fire suppression industry, slowing down flame propagation in case of a fire outbreak. To quantify flame spread with nitrogen dilution, laminar flame speed of the mixture needs to be evaluated. Experiments under earth gravity showed that laminar flame speed extraction is impossible for highly dilute conditions due to flame-front distortions. To overcome this, experiments were carried out under microgravity, showing a reduction in flame speed induced by radiation.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
L. Nista, C. D. K. Schumann, T. Grenga, A. Attili, H. Pitsch
Summary: This work proposes a super-resolution Generative Adversarial Network (GAN) as a closure model for unresolved subfilter-stress and scalar-flux tensors in LES. The model is evaluated on similar configurations at different Reynolds and Karlovitz numbers and shows good generalization ability across different physical conditions. It outperforms existing algebraic models when preserving the ratio between the filter size and the Kolmogorov scale. Additionally, the model demonstrates the capability of reconstructing scalar fields with large gradients that were not explicitly used in the training.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Raymond Langer, Qian Mao, Heinz Pitsch
Summary: This work develops a detailed chemical kinetic model for Polycyclic Aromatic Hydrocarbon (PAH) chemistry and focuses on the prediction of soot precursors. The model was validated against experimental measurements and analyzed the effects of experimental uncertainty. The study also investigates the formation mechanisms of indene and naphthalene, as well as the role of five-member rings in PAH species and soot particles.
COMBUSTION AND FLAME
(2023)
Article
Thermodynamics
Can Huang, Yuqing Zhao, Indu Sekhar Roy, Bingjie Chen, Nils Hansen, Heinz Pitsch, Kai Leonhard
Summary: The joint and flexible utilization of renewable electricity, ligno-cellulosic biomass, and/or CO 2 point sources to produce bio-hybrid fuels is a promising solution to achieve carbon neutrality while meeting the energy demand of the transportation sector.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Hongchao Chu, Lukas Berger, Temistocle Grenga, Michael Gauding, Liming Cai, Heinz Pitsch
Summary: The understanding and prediction of the early development of flame kernels are crucial for the relight of aviation gas turbines and the control of cycle-to-cycle variations (CCV) of spark-ignition engines. Turbulence has significant effects on the development of premixed iso-octane and hydrogen turbulent flame kernels. The variations in flow field and turbulence can lead to remarkable differences in the flame kernel interactions with turbulence, fuel consumption rate, and flame response to curvature.
COMBUSTION AND FLAME
(2023)
Article
Thermodynamics
Michael J. Hegetschweiler, Lukas Berger, Raik Hesse, Joachim Beeckmann, Chaimae Bariki, Heinz Pitsch, Gregory T. Linteris
Summary: This study investigates data reduction techniques for measuring the laminar burning velocities of R32(CH2F2)-air mixtures using a constant volume combustion device. The accuracy of different data reduction models is assessed by comparing them with results from detailed numerical simulations. The effects of stretch, radiation, and post-processing methodologies on the accuracy of the results are also explored and quantified. The study highlights the importance of using the correct radiation model in the data reduction process.
COMBUSTION AND FLAME
(2023)
Article
Thermodynamics
Xu Wen, Lukas Berger, Florian vom Lehn, Alessandro Parente, Heinz Pitsch
Summary: This study investigates the NOx formation characteristics of a thermodiffusively unstable premixed hydrogen flame. The results show that curvature directly affects NOx formation, especially the dominant NNH and N2O reaction pathways. The contribution of the thermal-NO pathway is negligible. The flamelet model gives good predictions in positively-curved flame segments, but discrepancies exist in negatively-curved flame regions.
COMBUSTION AND FLAME
(2023)
Article
Thermodynamics
Mathis Bode, Michael Gauding, Dominik Goeb, Tobias Falkenstein, Heinz Pitsch
Summary: Models for finite-rate-chemistry in underresolved flows pose challenges for complex configuration simulations, especially when turbulence is involved. This work enhances the PIESRGAN modeling approach for turbulent premixed combustion by adjusting the network's processing of physical information, smoothing the training process, and considering density changes. The resulting model shows good performance in tests using direct numerical simulation data of a turbulent premixed flame kernel and allows for the efficient study of statistical processes due to lower computing costs.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)