The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Fengshan Liu - One of the best experts on this subject based on the ideXlab platform.
-
soot primary particle sizing in a n heptane doped methane air laminar coflow Diffusion Flame by planar two color tire lii and tem image analysis
Fuel, 2020Co-Authors: F Patino, Jean-louis Consalvi, Fengshan Liu, J J Cruz, I Verdugo, Jose Moran, A FuentesAbstract:Abstract Soot primary particle size distribution along the centerline of a laminar coflow methane/air Diffusion Flame doped with vaporized n-heptane at atmospheric pressure was studied using the planar two-color time-resolved laser-induced incandescence (TiRe-LII) technique and analysis of transmission electron microscope images. An improved thermophoretic probe sampling procedure was used to collect samples of soot particles. The LII signals captured at two wavelength bands in the visible are used to determine the soot effective temperature by two-color pyrometry. The methodology was first validated against the literature data obtained in a laminar coflow ethylene/air Diffusion Flame. The same methodology is then applied to the n-heptane doped methane Flame along the Flame centerline. The Sauter and geometric mean diameters of soot primary particles were obtained. Good agreement is found between the soot primary particle size distributions obtained by the two techniques.
-
effects of water vapor addition to the air stream on soot formation and Flame properties in a laminar coflow ethylene air Diffusion Flame
Combustion and Flame, 2014Co-Authors: Fengshan Liu, Jean-louis Consalvi, Andres FuentesAbstract:Abstract The effects of adding water vapor to the air stream on Flame properties and soot volume fraction were investigated numerically in a laminar coflow ethylene/air Diffusion Flame at atmospheric pressure by solving the fully elliptic conservation equations and using a detailed C 2 reaction mechanism including PAH up to pyrene and detailed thermal and transport properties. Thermal radiation was calculated using the discrete-ordinates method and a statistical narrow-band correlated- k based wide band model for the absorption coefficients of CO 2 and H 2 O. Soot formation was modeled using a PAH based inception model and the HACA mechanism for surface growth and oxidation. Addition of water vapor significantly reduces radiation heat loss from the Flame primarily through reduced soot loading and Flame temperature. The added water vapor affects soot formation and Flame properties through not only dilution and thermal effects, but also through chemical effect. The chemical effect is as significant as the dilution and thermal effects. The primary pathway for the chemical effect of water vapor is the reverse reaction of OH + H 2 ↔ H + H 2 O. Our numerical results confirm that the reduced H radical concentration leads to lower PAH concentrations and consequently lower soot inception rates. In contrast, the radiation effect due to the added water vapor was found to have a minor influence on both Flame structure and soot formation in the laminar Diffusion Flame investigated.
-
effect of hydrogen and helium addition to fuel on soot formation in an axisymmetric coflow laminar methane air Diffusion Flame
International Journal of Hydrogen Energy, 2014Co-Authors: Fengshan Liu, Wenjun KongAbstract:Abstract A detailed numerical study was conducted to investigate the effects of hydrogen and helium addition to fuel on soot formation in atmospheric axisymmetric coflow laminar methane/air Diffusion Flame. Detailed gas-phase chemistry and thermal and transport properties were employed in the numerical calculations. Soot was modeled using a PAH based inception model and the HACA mechanism for surface growth and oxidation. Numerical results were compared with available experimental data. Both experimental and numerical results show that helium addition is more effective than hydrogen addition in reducing soot loading in the methane/air Diffusion Flame. These results are different from the previous investigations in ethylene/air Diffusion Flames. Hydrogen chemically enhances soot formation when added to methane. The different chemical effects of hydrogen addition to ethylene and methane on soot formation are explained in terms of the different effects of hydrogen addition on propargyl, benzene, and pyrene formation low in the Flames.
-
a numerical and experimental study of a laminar sooting coflow jet a1 Diffusion Flame
Proceedings of the Combustion Institute, 2011Co-Authors: Meghdad Saffaripour, Fengshan Liu, Hongsheng Guo, Gregory J Smallwood, Q. Zhang, P Zabeti, Seth B Dworkin, Murray J. ThomsonAbstract:Abstract As the drive towards a better understanding of airline fuel combustion, and its associated emission characteristics continues, there is a need for fundamental numerical and experimental jet fuel studies. In the present work, a numerical and experimental study is conducted for a complex blended liquid fuel, Jet-A1, in an atmospheric pressure, laminar sooting coflow Diffusion Flame. The numerical model uses a surrogate mixture, comprising 69% n -decane, 20% n -propylbenzene, and 11% n -propylcyclohexane (by mole). The combustion chemistry and soot formation are solved using a detailed chemical kinetic mechanism with 304 species and 2265 reactions, detailed transport, and a sectional soot model including soot nucleation, heterogeneous surface growth and oxidation, soot aggregate coagulation and fragmentation, and PAH surface condensation. The problem is intractable by serial processing; therefore, distributed-memory parallelization is used, employing 192 CPUs. Experimentally, soot volume fraction and gaseous species concentration profiles are determined by a Laser Extinction Measurement method and Gas Chromatography, respectively, in a coflow Diffusion Flame of vaporized Jet-A1. These data are used to validate the model. Centerline species concentrations are satisfactorily reproduced by the model. The order of magnitude of the peak soot volume fraction is well predicted without calibrating any of the model constants to the experimental data, but discrepancies remain between numerical and experimental results on the radial locations of the peaks and the centerline soot concentration levels.
-
implementation of an advanced fixed sectional aerosol dynamics model with soot aggregate formation in a laminar methane air coflow Diffusion Flame
Combustion Theory and Modelling, 2008Co-Authors: Q. Zhang, Fengshan Liu, Hongsheng Guo, Gregory J Smallwood, Murray J. ThomsonAbstract:An advanced fixed sectional aerosol dynamics model describing the evolution of soot particles under simultaneous nucleation, coagulation, surface growth and oxidation processes is successfully implemented to model soot formation in a two-dimensional laminar axisymmetric coflow methane/air Diffusion Flame. This fixed sectional model takes into account soot aggregate formation and is able to provide soot aggregate and primary particle size distributions. Soot nucleation, surface growth and oxidation steps are based on the model of Fairweather et al. Soot equations are solved simultaneously to ensure convergence. The numerically calculated Flame temperature, species concentrations and soot volume fraction are in good agreement with the experimental data in the literature. The structures of soot aggregates are determined by the nucleation, coagulation, surface growth and oxidation processes. The result of the soot aggregate size distribution function shows that the aggregate number density is dominated by sma...
Murray J. Thomson - One of the best experts on this subject based on the ideXlab platform.
-
effects of n propylbenzene addition to n dodecane on soot formation and aggregate structure in a laminar coflow Diffusion Flame
Proceedings of the Combustion Institute, 2017Co-Authors: Tongfeng Zhang, Liyun Zhao, Murray J. ThomsonAbstract:Abstract The effects of n -propylbenzene addition to n -dodecane on soot formation and aggregate structure in a laminar coflow Diffusion Flame is investigated. The goal is to gain insight on the influence of n -propylbenzene addition to n -dodecane on the underlying mechanisms of soot formation processes. The methane laminar coflow Diffusion Flame doped with pure n -dodecane establishes the base environment in this study. n -Propylbenzene is mixed into n -dodecane at three levels: 15%, 30% and 45% in mole fraction. The inlet total carbon flow rate is held constant for all of the Flames. The combined laser extinction and two-angle elastic light scattering method is used to measure soot volume fraction, primary particle diameter and number density. As expected, soot volume fraction is shown to increase at all heights in the Flames with increasing mole fraction of n -propylbenzene in the liquid fuel mixture. The differences in profiles of soot volume fraction suggest a non-linear relationship between the mole fraction of n -propylbenzene in the liquid fuel mixture and the increase in soot production. The relative importance of soot inception and surface growth affected by n -propylbenzene addition is shown to be different along the Flame wing and centerline. Along the wing, the aromatic fuel molecular structure primarily influences the initial soot inception process at earlier times by providing a larger population of incipient soot particles for the subsequent surface growth. Along the centerline, the aromatic fuel chemistry effect is stronger, as it accelerates both the soot inception and the subsequent surface growth processes. The experimental data presented in this study is also useful for the validation of soot models of the liquid fuel surrogate components.
-
molecular characterization of organic content of soot along the centerline of a coflow Diffusion Flame
Physical Chemistry Chemical Physics, 2014Co-Authors: Jeremy P Cain, Murray J. Thomson, Alexander Laskin, Mohammad Reza Kholghy, Hai WangAbstract:High-resolution mass spectrometry coupled with nanospray desorption electrospray ionization was used to probe chemical constituents of young soot particles sampled along the centerline of a coflow Diffusion Flame of a three-component Jet-A1 surrogate. In lower positions where particles are transparent to light extinction (λ = 632.8 nm), peri-condensed polycyclic aromatic hydrocarbons (PAHs) are found to be the major components of the particle material. These particles become enriched with aliphatic components as they grow in mass and size. Before carbonization occurs, the constituent species in young soot particles are aliphatic and aromatic compounds 200–600 amu in mass, some of which are oxygenated. Particles dominated by PAHs or mixtures of PAHs and aliphatics can exhibit liquid-like appearance observed by electron microscopy and be transparent to visible light. The variations in chemical composition observed here indicate that the molecular processes of soot formation in coflow Diffusion Flames may be more complex than previously thought. For example, the mass growth and enrichment of aliphatic components in an initial mostly aromatic structure region of the Flame that is absent of H atoms or other free radicals indicates that there must exist at least another mechanism of soot mass growth in addition to the hydrogen abstraction–carbon addition mechanism currently considered in fundamental models of soot formation.
-
experimental and kinetic modeling study of 1 hexanol combustion in an opposed flow Diffusion Flame
Proceedings of the Combustion Institute, 2013Co-Authors: C Yeung, Murray J. ThomsonAbstract:Abstract Biofuels are of particular interest as they have the potential to reduce our dependence on petroleum-derived fuels and the levels of greenhouse gas emissions from transportation. 1-Hexanol is a promising renewable long chain alcohol that can be used in conventional fuel blends or as a cosolvent for biodiesel mixtures. However, the fundamental combustion properties of 1-hexanol have not been fully characterized in the literature. Thus, new experimental results, consisting of temperature and concentration profiles of stable species were obtained for the oxidation of 1-hexanol generated in an opposed-flow Diffusion Flame at 0.101 MPa. This experimental data were compared to the predicted values of a detailed chemical kinetic mechanism proposed in the literature to study the combustion of 1-hexanol.This mechanism consists of 361 chemical species and 2687 chemical reactions (most of them reversible). Reaction pathway and sensitivity analyses were performed to interpret the results. In addition, improvements were investigated to optimize the proposed mechanism.
-
application of an enhanced pah growth model to soot formation in a laminar coflow ethylene air Diffusion Flame
Combustion and Flame, 2011Co-Authors: Seth B Dworkin, Q. Zhang, Murray J. Thomson, Nadezhda A Slavinskaya, Uwe RiedelAbstract:A recently developed chemical kinetic scheme for C2 fuel combustion with PAH growth has been implemented in a parallelized coflow Flame solver. The reaction mechanism has been developed to include almost all reasonably well-established reaction classes for aromatic ring formation and soot particle precursor molecular weight growth. The model has recently been validated for zero- and one-dimensional premixed Flame systems [N.A. Slavinskaya, P. Frank, Combust. Flame 156 (2009) 1705–1722] and has now been updated and extended to a sooting ethylene/air Diffusion Flame in the coflow geometry. Updates to the mechanism reflect the latest advances in the literature and address numerical stiffness that was present in Diffusion Flame systems. The chemical kinetic mechanism has been coupled to a sectional aerosol dynamics model for soot growth, considering PAH-based inception and surface condensation, surface chemistry (growth and oxidation), coagulation, and fragmentation. The sectional model predicts the soot aggregate number density and the number of primary particles per aggregate in each section, so as to yield information on particle size distribution and structure. Flame simulation data for the present mechanism is compared to data computed using two other reaction schemes [J. Appel, H.
-
a numerical and experimental study of a laminar sooting coflow jet a1 Diffusion Flame
Proceedings of the Combustion Institute, 2011Co-Authors: Meghdad Saffaripour, Fengshan Liu, Hongsheng Guo, Gregory J Smallwood, Q. Zhang, P Zabeti, Seth B Dworkin, Murray J. ThomsonAbstract:Abstract As the drive towards a better understanding of airline fuel combustion, and its associated emission characteristics continues, there is a need for fundamental numerical and experimental jet fuel studies. In the present work, a numerical and experimental study is conducted for a complex blended liquid fuel, Jet-A1, in an atmospheric pressure, laminar sooting coflow Diffusion Flame. The numerical model uses a surrogate mixture, comprising 69% n -decane, 20% n -propylbenzene, and 11% n -propylcyclohexane (by mole). The combustion chemistry and soot formation are solved using a detailed chemical kinetic mechanism with 304 species and 2265 reactions, detailed transport, and a sectional soot model including soot nucleation, heterogeneous surface growth and oxidation, soot aggregate coagulation and fragmentation, and PAH surface condensation. The problem is intractable by serial processing; therefore, distributed-memory parallelization is used, employing 192 CPUs. Experimentally, soot volume fraction and gaseous species concentration profiles are determined by a Laser Extinction Measurement method and Gas Chromatography, respectively, in a coflow Diffusion Flame of vaporized Jet-A1. These data are used to validate the model. Centerline species concentrations are satisfactorily reproduced by the model. The order of magnitude of the peak soot volume fraction is well predicted without calibrating any of the model constants to the experimental data, but discrepancies remain between numerical and experimental results on the radial locations of the peaks and the centerline soot concentration levels.
Markus Kraft - One of the best experts on this subject based on the ideXlab platform.
-
evolution of the soot particle size distribution along the centreline of an n heptane toluene co flow Diffusion Flame
Combustion and Flame, 2019Co-Authors: Jochen A H Dreyer, Maximilian Poli, Nick Eaves, Maria L Botero, Jethro Akroyd, Sebastian Mosbach, Markus KraftAbstract:Abstract A newly developed experimental set-up for studying liquid hydrocarbon combustion in the well-established Yale burner was used to investigate the correlation between fuel composition and its sooting propensity. Soot particle size distributions (PSDs) and Flame temperatures along the centreline of an n-heptane/toluene co-flow Diffusion Flame are reported. The results are compared to soot temperature and volume fraction profiles obtained using colour ratio pyrometry. The addition of toluene (0, 5, 10, and 15 mol%) to heptane moved soot inception to lower heights above the burner (HAB). The earlier inception extended the soot growth zone in the toluene-laden Flames, leading to larger soot primary and agglomerate particles. Toluene addition had little influence on the maximum soot number density, indicating that the observed increase in soot volume fraction can mainly be attributed to the increase in particle size. The reported PSDs inside a vapour-fed Diffusion Flame are the first of their kind and provide a comprehensive dataset for future studies of combustion chemistry and soot particle models.
-
internal structure of soot particles in a Diffusion Flame
Carbon, 2019Co-Authors: Maria L Botero, Jochen A H Dreyer, Jethro Akroyd, Markus Kraft, Yuan Sheng, Jacob W Martin, Wenming YangAbstract:Abstract The evolution of the internal structure of soot particles was studied in a coflow Diffusion Flame. Soot particles from the Flame were imaged using high resolution transmission electron microscopy. An algorithm to quantify the nano-structure of the particles was extended to study the radial distribution of fringes within the particles. The approximate size of the molecules in the particles was calculated from the fringe lengths, assuming planar peri-condensed PAHs. The molecules are slightly larger (∼16 rings) and more stacked at the core than at the surface (∼12 rings) of the youngest particles sampled, suggesting that the particles could be formed via the stabilisation of a nuclei of larger PAHs and condensation of smaller PAHs on their surface. In the lower-temperature region of the Flame the molecules grow mainly at the surface of the particles, whereas the molecules in the core of the particles become less stacked and slightly smaller, indicating some degree of nano-structural mobility. In the higher-temperature region of the Flame, a graphitisation process takes place, with the development of a shell of longer (∼20 rings), flatter and more compact molecules, and an immobilised amorphous core. At the tip of the Flame the particles are oxidised, mainly through surface oxidation.
-
experimental and numerical study of the evolution of soot primary particles in a Diffusion Flame
Proceedings of the Combustion Institute, 2019Co-Authors: Maria L Botero, Jochen A H Dreyer, Jethro Akroyd, Yuan Sheng, Wenming Yang, Nick A Eaves, Markus KraftAbstract:Abstract The evolution of primary soot particles is studied experimentally and numerically along the centreline of a co-flow laminar Diffusion Flame. Soot samples from a Flame fueled with C2H4 are taken thermophoretically at different heights above the burner (HAB), their size and nano-structure are analysed through TEM. The experimental results suggest that after inception, the nascent soot particles coagulate and coalesce to form larger primary particles ( ∼ 5 to 15 nm). As these primary particles travel along the centreline, they grow mainly due coagulation and condensation and a layer of amorphous hydrocarbons (revealed by HRTEM) forms on their surface. This amorphous layer appears to promote the aggregation of primary particles to form fractal structures. Fast carbonisation of the amorphous layer leads to a graphitic-like shell around the particles. Further graphitization compacts the primary particles, resulting in a decrease of their size. Towards the Flame tip the primary particles decrease in size due to rapid oxidation. A detailed population balance model is used to investigate the mechanisms that are important for prediction of primary particle size distributions. Suggestions are made regarding future model development efforts. Simulation results indicate that the primary particle size distributions are very sensitive to the parameterization of the coalescence and particle rounding processes. In contrast, the average primary particle size is less sensitive to these parameters. This demonstrates that achieving good predictions for the average primary particle size does not necessarily mean that the distribution has been accurately predicted.
-
sooting tendency of surrogates for the aromatic fractions of diesel and gasoline in a wick fed Diffusion Flame
Fuel, 2015Co-Authors: Maria L Botero, Jethro Akroyd, Sebastian Mosbach, Markus KraftAbstract:Abstract The sooting characteristics of pure substituted-aromatic fuels in a wick-fed Diffusion Flame were studied in terms of the particle size distribution (PSD) of the soot. The temperature and PSDs were measured at the tip of Flames of different heights, using a thin-wired thermocouple and differential mobility spectrometer. The temperature at the tip of the Flames was found to decrease with increases in Flame height. At the smallest Flame height the PSDs are bimodal with a slightly larger coagulation mode, except for trimethylbenze which exhibits a large nucleation mode. For larger Flame heights the coagulation mode enlarges and shifts to larger particle diameters. After the smoke point the PSDs present a single mode of particles with sizes of about 100 nm. Close to the smoke point, all fuels show a slight decrease in the rate of particle growth while the Flame changes from having a closed tip to an opened soot trail. At the same flow rates, tetralin produced the largest particles, toluene and 1,2,4-trimethylbenzene produced particles with similar sizes and n-butylbenzene produced the smallest particles. This indicates that aromatics substituted with larger aliphatics tend to produce smaller soot particles.
Hongsheng Guo - One of the best experts on this subject based on the ideXlab platform.
-
a numerical and experimental study of a laminar sooting coflow jet a1 Diffusion Flame
Proceedings of the Combustion Institute, 2011Co-Authors: Meghdad Saffaripour, Fengshan Liu, Hongsheng Guo, Gregory J Smallwood, Q. Zhang, P Zabeti, Seth B Dworkin, Murray J. ThomsonAbstract:Abstract As the drive towards a better understanding of airline fuel combustion, and its associated emission characteristics continues, there is a need for fundamental numerical and experimental jet fuel studies. In the present work, a numerical and experimental study is conducted for a complex blended liquid fuel, Jet-A1, in an atmospheric pressure, laminar sooting coflow Diffusion Flame. The numerical model uses a surrogate mixture, comprising 69% n -decane, 20% n -propylbenzene, and 11% n -propylcyclohexane (by mole). The combustion chemistry and soot formation are solved using a detailed chemical kinetic mechanism with 304 species and 2265 reactions, detailed transport, and a sectional soot model including soot nucleation, heterogeneous surface growth and oxidation, soot aggregate coagulation and fragmentation, and PAH surface condensation. The problem is intractable by serial processing; therefore, distributed-memory parallelization is used, employing 192 CPUs. Experimentally, soot volume fraction and gaseous species concentration profiles are determined by a Laser Extinction Measurement method and Gas Chromatography, respectively, in a coflow Diffusion Flame of vaporized Jet-A1. These data are used to validate the model. Centerline species concentrations are satisfactorily reproduced by the model. The order of magnitude of the peak soot volume fraction is well predicted without calibrating any of the model constants to the experimental data, but discrepancies remain between numerical and experimental results on the radial locations of the peaks and the centerline soot concentration levels.
-
implementation of an advanced fixed sectional aerosol dynamics model with soot aggregate formation in a laminar methane air coflow Diffusion Flame
Combustion Theory and Modelling, 2008Co-Authors: Q. Zhang, Fengshan Liu, Hongsheng Guo, Gregory J Smallwood, Murray J. ThomsonAbstract:An advanced fixed sectional aerosol dynamics model describing the evolution of soot particles under simultaneous nucleation, coagulation, surface growth and oxidation processes is successfully implemented to model soot formation in a two-dimensional laminar axisymmetric coflow methane/air Diffusion Flame. This fixed sectional model takes into account soot aggregate formation and is able to provide soot aggregate and primary particle size distributions. Soot nucleation, surface growth and oxidation steps are based on the model of Fairweather et al. Soot equations are solved simultaneously to ensure convergence. The numerically calculated Flame temperature, species concentrations and soot volume fraction are in good agreement with the experimental data in the literature. The structures of soot aggregates are determined by the nucleation, coagulation, surface growth and oxidation processes. The result of the soot aggregate size distribution function shows that the aggregate number density is dominated by sma...
-
numerical study on the influence of hydrogen addition on soot formation in a laminar ethylene air Diffusion Flame
Combustion and Flame, 2006Co-Authors: Hongsheng Guo, Fengshan Liu, Gregory J Smallwood, Omer L GulderAbstract:Abstract The influence of hydrogen addition to the fuel of an atmosphere pressure coflow laminar ethylene–air Diffusion Flame on soot formation was studied by numerical simulation. A detailed gas-phase reaction mechanism, which includes aromatic chemistry up to four rings, and complex thermal and transport properties were used. The fully coupled elliptic governing equations were solved. The interactions between soot and gas-phase chemistry were taken into account. Radiation heat transfer from CO2, CO, H2O, and soot was calculated using the discrete-ordinates method coupled to a statistical narrow-band-correlated K-based wide-band model. The predicted results were compared with the available experimental data and analyzed. It is indicated that the addition of hydrogen to the fuel in an ethylene–air Diffusion Flame suppresses soot formation through the effects of dilution and chemistry. This result is in agreement with available experiments. The simulations further suggest that the chemically inhibiting effect of hydrogen addition on soot formation is due to the decrease of hydrogen atom concentration in soot surface growth regions and higher concentration of molecular hydrogen in the lower Flame region.
-
the chemical effects of carbon dioxide as an additive in an ethylene Diffusion Flame implications for soot and nox formation
Combustion and Flame, 2001Co-Authors: Fengshan Liu, Hongsheng Guo, Gregory J Smallwood, Omer L GulderAbstract:Abstract A numerical study of the chemical effects of carbon dioxide addition on both the fuel side and the oxidizer side of a Diffusion Flame was conducted in an attempt to explore the chemistry mechanism of the experimentally observed soot suppression by carbon dioxide addition. The laminar ethylene Diffusion Flame established in a counterflow configuration was considered by using detailed chemistry and transport properties. A novel strategy was developed that is able to isolate the chemical effects of a species added on either the fuel or the oxidizer side. Numerical results show that carbon dioxide, added either on the fuel side or the oxidizer side, indeed participates in chemical reactions. The specific aspects of the chemical effects of carbon dioxide addition that have direct implications for chemical suppression of soot formation are reduced concentration of acetylene and Flame temperature and conversion of carbon dioxide by hydrogen atom to hydroxyl which prompts oxidation of soot precursors in the soot formation region. Reactions CO 2 +H → CO+OH and CO 2 +CH → HCO+CO were found to be responsible for the chemical effects of carbon dioxide addition. The chemical effects of CO 2 addition on the fuel side are small but becomes significant when introduced on the oxidizer side. The chemical effects of CO 2 addition were also found to suppress NO x formation.
-
extinction of low stretched Diffusion Flame in microgravity
Combustion and Flame, 1998Co-Authors: Kaoru Maruta, Hongsheng Guo, Masaharu Yoshida, Takashi NiiokaAbstract:Extinction of counterflow Diffusion Flames of air and methane diluted with nitrogen is studied by drop tower experiments and numerical calculation using detailed chemistry and transport properties. Radiative heat loss from the Flame zone is taken into consideration. Experimental results identified two kinds of extinction at the same fuel concentration, that is, in addition to the widely known stretch extinction, another type of extinction is observed when the stretch rate is sufficiently low. Consequently, plots of stretch rates versus fuel concentration limits exhibit a C-shaped extinction curve. Numerical calculation including radiative heat loss from the Flame zone qualitatively agreed with the experimental results and indicated that the mechanism of counterflow Diffusion Flame extinction at low stretch rates was radiative heat loss.
Omer L Gulder - One of the best experts on this subject based on the ideXlab platform.
-
numerical study on the influence of hydrogen addition on soot formation in a laminar ethylene air Diffusion Flame
Combustion and Flame, 2006Co-Authors: Hongsheng Guo, Fengshan Liu, Gregory J Smallwood, Omer L GulderAbstract:Abstract The influence of hydrogen addition to the fuel of an atmosphere pressure coflow laminar ethylene–air Diffusion Flame on soot formation was studied by numerical simulation. A detailed gas-phase reaction mechanism, which includes aromatic chemistry up to four rings, and complex thermal and transport properties were used. The fully coupled elliptic governing equations were solved. The interactions between soot and gas-phase chemistry were taken into account. Radiation heat transfer from CO2, CO, H2O, and soot was calculated using the discrete-ordinates method coupled to a statistical narrow-band-correlated K-based wide-band model. The predicted results were compared with the available experimental data and analyzed. It is indicated that the addition of hydrogen to the fuel in an ethylene–air Diffusion Flame suppresses soot formation through the effects of dilution and chemistry. This result is in agreement with available experiments. The simulations further suggest that the chemically inhibiting effect of hydrogen addition on soot formation is due to the decrease of hydrogen atom concentration in soot surface growth regions and higher concentration of molecular hydrogen in the lower Flame region.
-
the chemical effects of carbon dioxide as an additive in an ethylene Diffusion Flame implications for soot and nox formation
Combustion and Flame, 2001Co-Authors: Fengshan Liu, Hongsheng Guo, Gregory J Smallwood, Omer L GulderAbstract:Abstract A numerical study of the chemical effects of carbon dioxide addition on both the fuel side and the oxidizer side of a Diffusion Flame was conducted in an attempt to explore the chemistry mechanism of the experimentally observed soot suppression by carbon dioxide addition. The laminar ethylene Diffusion Flame established in a counterflow configuration was considered by using detailed chemistry and transport properties. A novel strategy was developed that is able to isolate the chemical effects of a species added on either the fuel or the oxidizer side. Numerical results show that carbon dioxide, added either on the fuel side or the oxidizer side, indeed participates in chemical reactions. The specific aspects of the chemical effects of carbon dioxide addition that have direct implications for chemical suppression of soot formation are reduced concentration of acetylene and Flame temperature and conversion of carbon dioxide by hydrogen atom to hydroxyl which prompts oxidation of soot precursors in the soot formation region. Reactions CO 2 +H → CO+OH and CO 2 +CH → HCO+CO were found to be responsible for the chemical effects of carbon dioxide addition. The chemical effects of CO 2 addition on the fuel side are small but becomes significant when introduced on the oxidizer side. The chemical effects of CO 2 addition were also found to suppress NO x formation.