Article
Thermodynamics
Hernando Maldonado Colman, Pavan Prakash Duvvuri, Michael E. Mueller
Summary: Large Eddy Simulation (LES) is used to investigate the evolution of soot in turbulent nonpremixed bluff body flames with different bluff body diameters. The new soot subfilter Probability Density Function (PDF) model accurately accounts for the distribution of soot and corrects previous models that overestimated soot oxidation. The results of the LES modeling approach compare well with experimental measurements, accurately predicting the distribution of soot in different regions of the flames. Mechanistic understanding of soot evolution is gained through the analysis of the source terms of the soot volume fraction.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(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
Thermodynamics
Mohammed K. H. Abbas Alhumairi, Yasseen A. Almahdawi, Sami A. Nawi
Summary: The computational investigation of the lean premixed flame in a jet flow combustor revealed that the flame topology strongly depends on the turbulence parameters, especially the amplitude of pulsation and the mass flow rate ratio. The V-shaped flame with corrugated wings formed near the flame holder reflects the turbulence-combustion interaction in all test cases. The suggested large-eddy simulation (LES) model is suitable for predicting the flame location and flame topology associated with pulsating jet flow.
Article
Chemistry, Physical
Yilong Yin, Paul R. Medwell, Bassam B. Dally
Summary: The low radiant intensity of hydrogen flames can be increased by adding biofuels with a high propensity for sooting. This study investigates the effects of biofuel concentration and phase on the combustion characteristics of turbulent nonpremixed hydrogen-based flames. Blending biofuel surrogates and hydrogen can enhance the formation of soot and increase luminosity, while also increasing NOx emissions.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2023)
Article
Thermodynamics
Qiang Wang, Xuan Liang, Aquan Lu, Ben Wang, Osamu Fujita, Suk Ho Chung, Longhua Hu
Summary: The blowout behavior of inclined nonpremixed turbulent jet flames is investigated by varying the jet inclined angle. Experimental quantification of the blowout limit and numerical simulations are performed to analyze the flow field difference for different inclined angles. Physical modeling and analysis are conducted to understand the effect of inclined angle on blowout behavior. The findings provide new insights into the blowout limit of nonpremixed inclined turbulent jet flames and propose a model to characterize this behavior.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Pavel Panek, Davy Brouzet, Mohsen Talei, Robert L. Gordon
Summary: This paper evaluates flame surface density modeling in the context of large-eddy simulation (LES) using a direct numerical simulation (DNS) dataset. The results suggest that significant improvement is needed for flame surface density modeling, particularly for (rho Sd)s.
COMBUSTION AND FLAME
(2022)
Article
Mechanics
Hasret Turkeri, Xinyu Zhao, Metin Muradoglu
Summary: The LES/PDF method is used to study turbulent swirling stratified flames, showing good agreement between numerical and experimental results in terms of velocity, temperature, equivalence ratio, and mass fractions of species. However, the method may be insufficient in predicting a low-equivalence-ratio high-temperature region near the bluff body.
Review
Chemistry, Applied
H. S. Zhen, Z. L. Wei, X. Y. Liu, Z. H. Liu, X. C. Wang, Z. H. Huang, C. W. Leung
Summary: This paper provides a thorough review of laboratory studies of inverse diffusion flame (IDF), focusing on the flow and combustion behaviors during the transition of IDF from laminar to turbulent. By discussing the geometric, fluidynamic, and combustion parameters of IDF, as well as topics like burner design, geometric features, flow dynamics, and flame characteristics, it aims to guide future studies and practical applications of IDF.
FUEL PROCESSING TECHNOLOGY
(2021)
Article
Energy & Fuels
Guoqiang Xiong, Gesheng Li, Weilin Zeng, Junjie Liang
Summary: The steady flamelet method was used in the large eddy simulation (LES) of turbulent cool flames to investigate its capability. The results showed that it accurately captured the mean and variance trends for temperature, mixture fraction, and formaldehyde, as well as described the flame morphology of the two-stream flamelet form.
Article
Thermodynamics
Qiang Wang, Longhua Hu, Fei Tang, Adriana Palacios, Suk Ho Chung
Summary: The lifted flame behavior of inclined turbulent jets was experimentally investigated by varying the inclination angle of non-premixed fuel jets. The results showed that the lift-off length increases linearly with the increase in initial fuel jet velocity at a fixed inclination angle. A physical model was developed to quantify the lift-off length, taking into account the effect of jet inclination angle.
COMBUSTION AND FLAME
(2023)
Article
Chemistry, Physical
Guangze Li, Huangwei Zhang, Longfei Chen
Summary: Large eddy simulations with a three-dimensional finite-volume Conditional Moment Closure (CMC) model were conducted for a hydrogen/nitrogen lifted flame with detailed chemical mechanism. The research focused on the influences of mesh resolution and convection scheme of finite-volume CMC equations on predictions of reactive scalars and unsteady flame dynamics. The results showed that the lift-off height and reactive scalars were affected by the coarseness of the CMC mesh, and the time sequences of hydroxyl radical mass fractions indicated that finer CMC mesh captured more unsteady details. Additionally, the effects of different convection schemes on lifted flame characteristics were investigated, showing limited differences on time-averaged temperature and species mass fractions.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2021)
Article
Energy & Fuels
Runzhi Liu, Kun Luo, Changcheng Song, Tai Jin, Min Chai, Jianren Fan
Summary: A novel direct moment closure (DMC) model has been developed and applied to simulate a supercritical flame. The DMC model shows improved prediction of reaction rate compared to the laminar chemistry closure (LCC) model. In addition, the LES-DMC model successfully reproduces the complex behaviors of the turbulent supercritical flame.
Article
Chemistry, Physical
Jiseop Lee, Nam Il Kim
Summary: Adding hydrogen to methane can reduce CO2 emissions from combustion systems, but it also presents challenges. This study investigated the combustion characteristics of a turbulent fuel jet with coaxial air under elevated pressures. The results identified three clear flame stabilization modes, with the inner-lifted mode demonstrating the best combustion performance.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2023)
Article
Thermodynamics
Yihao Tang, Venkat Raman
Summary: The study introduces a novel strained, non-adiabatic flamelet generated manifold model based on a counterflow premixed flame, which shows improved accuracy in predicting flame behavior. By varying strain and heat loss effects, different combustion modes are distinguished, enhancing the understanding of turbulent flame evolution.
COMBUSTION AND FLAME
(2021)
Article
Thermodynamics
Yunde Su, Seung Hyun Kim
Summary: The stretch effects in LES of a turbulent lean propane-air premixed Bunsen flame in the wrinkled flamelet regime are investigated. A simple approach to model the subgrid-scale flame stretch is proposed, which suggests using the volume-filtered strain rate on the unburned side of the filtered flame brush to approximate the surface-filtered strain rate. The study highlights the importance of mitigating the artificial heat release effects and examines the relative importance of curvature stretch and strain effects.
COMBUSTION SCIENCE AND TECHNOLOGY
(2023)
Article
Computer Science, Interdisciplinary Applications
Pierre-Yves C. R. Taunay, Michael E. Mueller
Summary: Quadrature-based moment methods (QBMM) are computational alternatives to direct Eulerian and Lagrangian particle solvers, providing noise-free solutions to the Boltzmann equation and capturing non-equilibrium velocity distribution functions (VDF) without excessive computational cost. Three QBMM approaches, QMOM, HyQMOM, and EQMOM, are applied to rarefied gas flow and plasma physics problems, with HyQMOM yielding good representations of both the moments and the VDF and providing significant wall-time improvement compared to other solvers.
JOURNAL OF COMPUTATIONAL PHYSICS
(2023)
Article
Meteorology & Atmospheric Sciences
Aditya K. K. Aiyer, Luc Deike, Michael E. E. Mueller
Summary: A sea surface-based hydrodynamic drag model is proposed in this paper to simulate the effect of waves on wind. The model is validated and shown to accurately predict average wind velocity and stress under different wave steepnesses and speeds. The model is easy to implement and has low computational cost, making it valuable for studying offshore wind energy and modeling air-sea fluxes.
JOURNAL OF THE ATMOSPHERIC SCIENCES
(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
Hernando Maldonado Colman, Pavan Prakash Duvvuri, Michael E. Mueller
Summary: Large Eddy Simulation (LES) is used to investigate the evolution of soot in turbulent nonpremixed bluff body flames with different bluff body diameters. The new soot subfilter Probability Density Function (PDF) model accurately accounts for the distribution of soot and corrects previous models that overestimated soot oxidation. The results of the LES modeling approach compare well with experimental measurements, accurately predicting the distribution of soot in different regions of the flames. Mechanistic understanding of soot evolution is gained through the analysis of the source terms of the soot volume fraction.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Hongchao Chu, Lukas Berger, Temistocle Grenga, Zhao Wu, Heinz Pitsch
Summary: Turbulence triggers thermodiffusive instabilities in flame kernels under engine conditions, significantly facilitating their growth and increasing fuel consumption rate. These instabilities also impact the mechanisms of flame surface area formation.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Kai Niemietz, Lukas Berger, Michael Huth, Antonio Attili, Heinz Pitsch
Summary: A direct numerical simulation (DNS) with finite rate chemistry was conducted to study the influences on carbon monoxide (CO) emissions in gas turbine combustion. The results showed that the mean strain rate of the turbulent flow, the flame-wall interaction, and the interactions of the flame with the recirculation zones of the flow all affected the formation of CO. The CO production and consumption in the turbulent flame differed significantly from those in a freely propagating flame. The relevant parameters for CO formation and consumption were identified as the local CO mass fraction, wall heat loss, and the mass fraction of the OH radical.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Marco Davidovic, Heinz Pitsch
Summary: The flamelet approach is commonly used for modeling non-premixed turbulent combustion. This study focuses on the consistent modeling of transport and mixing in mixture fraction space. A revised model is proposed based on a consistent formulation of flow parameters, which shows improved predictions in comparison to conventional models. The results demonstrate the capability of the Representative Interactive Flamelet (RIF) model in predicting pollutants under engine-relevant conditions.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(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
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
Giuseppe D'Alessio, Sankaran Sundaresan, Michael E. Mueller
Summary: Principal Component Analysis is used to reduce the dimensionality of turbulent reacting flows simulations through projection onto a lower-dimensional manifold. This study proposes a computationally efficient and automated nonlinear regression approach for predicting principal component source terms.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(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
Cristian E. Lacey, Katie VanderKam, Sankaran Sundaresan, Michael E. Mueller
Summary: Manifold-based turbulent combustion modeling reduces computational cost by projecting the thermochemical state onto a lower-dimensional space and reconstructing the state from a set of manifold equations. The dissipation rate of the progress variable is a key parameter in one-dimensional manifold equations, and existing models assume a 'universal' profile for this rate. However, the variance in instantaneous conditional progress variable dissipation rate profiles suggests that the assumed profiles are not universally valid.
COMBUSTION AND FLAME
(2024)
Article
Computer Science, Artificial Intelligence
Malik Hassanaly, Bruce A. Perry, Michael E. Mueller, Shashank Yellapantula
Summary: Improvements in computational and experimental capabilities are leading to a rapid increase in the amount of scientific data. This paper focuses on reducing the number of data points by selecting them based on estimated probability distribution, enabling efficient machine learning.
DATA-CENTRIC ENGINEERING
(2023)
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)