Download or read book The Evolution of Soot Morphology in Laminar Co Flow Diffusion Flames of the Surrogates for Jet A 1 and a Synthetic Kerosene written by Mohammad Reza Kholghy and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experimental and Numerical Studies for Soot Formation in Laminar Coflow Diffusion Flames of Jet A 1 and Synthetic Jet Fuels written by Meghdad Saffaripour and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Soot Morphology in a Laminar Co flow Diffusion Flame written by Jidong Xiao and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Detailed Modeling of Soot Formation Oxidation in Laminar Coflow Diffusion Flames written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: PhD.

Download or read book Detailed Modeling of Soot Formation oxidation in Laminar Coflow Diffusion Flames written by Qingan Zhang and published by . This book was released on 2009 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first goal of this thesis is to develop and validate a modeling tool into which fundamental combustion chemistry and aerosol dynamics theory are implemented for investigating soot formation/oxidation in multi-dimensional laminar coflow diffusion flames taking into account soot polydispersity and fractal-like aggregate structure. The second goal is to use the tool to study soot aggregate formation/oxidation in experimentally studied laminar coflow diffusion flames to advance the understanding of soot aggregate formation/oxidation mechanism.The first part of the thesis deals with the large CPU time problem when detailed models are coupled together. Using the domain decomposition method, a high performance parallel flame code is successfully developed. An advanced sectional aerosol dynamics model which can model fractal-like aggregate structure is successfully implemented into the parallel flame code. The performance of the parallel code is demonstrated through its application to the modeling of soot formation/oxidation in a laminar coflow CH4/air diffusion flame. The parallel efficiency reaches as high as 83%.In the third part of the thesis, the effects of oxidation-driven soot aggregate fragmentation on aggregate structure and soot oxidation rate are studied. Three fragmentation models with different fragmentation patterns are developed and implemented into the sectional aerosol dynamics model. The implementation of oxidation-driven aggregate fragmentation significantly improves the prediction of soot aggregate structure in the soot oxidation region.The second part of the thesis numerically explores soot aggregate formation in a laminar coflow C2H4/air diffusion flame using detailed PAH-based combustion chemistry and a PAH-based soot formation/oxidation model. Compared to the measured data, flame temperature, axial velocity, C2 H2 and OH concentrations, soot volume fraction, the average diameter and the number density of primary particles are reasonably well predicted. However, it is very challenging to predict effectively the average degree of particle aggregation. To do so, particle-particle and fluid-particle interactions that may cause non-unitary soot coagulation efficiency need to be considered. The original coagulation model is enhanced in this thesis to accommodate soot coagulation efficiency. Different types of soot coagulation efficiency are numerically investigated. It is found that a simple adjustment of soot coagulation efficiency from 100% to 20% provides good predictions on soot aggregate structure as well as flame properties.

Download or read book Effect of Flow Unsteadiness on Soot Morphology written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The morphology of combustion-generated soot is of fundamental interest, but is difficult to measure. A new planar diagnostic technique was developed for morphology measurements in simple laminar flames. Additionally, Polycyclic Aromatic Hydrocarbons, (PAH) the precursors to soot formation, were measured non-intrusively in an unsteady laminar flame to determine the characteristic time scales of their formation. An existing point-wise laser scattering technique to determine soot morphology was extended to a planar technique and applied to a laminar ethylene air co-flow flame. An Nd:YAG laser (532 nm) was used to illuminate the soot particles and the resulting scattered light was collected over a wide range of angles. A low power laser was used to eliminate fluorescence and incandescence interferences. Simultaneous laser induced incandescence measurements were used to determine the soot volume fraction. Six morphological parameters, including primary spherule size and mass fractal dimension, were derived using this new planar measurement technique based on RDG/PFA theory. The results clearly show the soot formation processes, including inception, agglomeration, and oxidization. A two-angle approximate method was also demonstrated and shown to be applicable for instantaneous measurements in unsteady flames. The approximate method can provide limited soot morphology information including primary particle size and number of primary particles per aggregate, when the fractal dimension and distribution are assumed. The approximate method was not suitable over the entire region of this flame because the fractal dimension varies significantly from the assumed value of 1.8, particularly in the soot inception zone. Three different size classes of PAH were measured qualitatively via laser induced fluorescence by detecting fluorescence in different spectral regions. The relative concentrations of these PAH were measured in counterflow diffusion flames subjected to both steady and.

Download or read book Soot Formation in Laminar Jet Diffusion Flames written by Peter Bradford Sunderland and published by . This book was released on 1995 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effect of Pressure on Soot Morphology in Laminar Diffusion Flames written by Ben Gigone and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of pressure on soot aggregate morphology in laminar diffusion flames, specifically pertaining to primary soot particle size and soot aggregate fractal parameters, was investigated in methane-air and nitrogen-diluted ethylene flames. Soot aggregate samples were collected by thermophoretic sampling within a high-pressure combusting chamber. Soot samples were imaged via transmission electron microscopy followed by an automated imaging detection method. The experiments covered pressures from 7 to 30 bar at vertical flame heights of 3, 6, and 8 mm in methane-air flames, and 3 to 6 bar at heights of 2, 5, 10, and 15 mm in nitrogen-diluted ethylene flames. It was observed that mean primary soot particle size increased with increasing pressure for both fuel types at virtually all flame locations. The fractal dimension was found to vary with pressure for both fuel cases, suggesting that a universal soot aggregate fractal value may not be justified in high-pressure flames.

Download or read book Soot Formation in Ethane air Coflow Laminar Diffusion Flames at Elevated Pressures written by Paul Michael Mandatori and published by . This book was released on 2006 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ethane-air laminar coflow non-smoking diffusion flames have been studied at pressures up to 3.34 MPa to determine the effect of pressure on soot formation, flame temperatures and physical flame properties. The spectral soot emission (SSE) diagnostic was used to obtain spatially resolved (both radially and axially) soot volume fraction and soot temperature measurements at pressures of 0.20 to 3.34 MPa. In general, temperature profiles of a given height were found to decrease with increasing pressure. Pressure was found to enhance soot formation with decreased sensitivity as pressures were increased. A power law relation between maximum soot volume fraction and pressure was found to be fvmax & prop;P 2.39 for 0.20 & le; P & le; 1.52 MPa and fvmax & prop;P 1.10 for 1.52 & le; P & le; 3.34 MPa. The integrated line-of-sight soot volume fraction was found to vary as fvline, max & prop;P 2.32 for 0.20 & le; P & le; 0.51 MPa, fvline, max & prop;P 1.44 for 0.51 & le; P & le; 1.52 MPa and fvline, max & prop;P 0.95 for 1.52 & le; P & le; 3.34 MPa. The variation of maximum carbon conversion to soot, as a percentage of the fuel's carbon, was etas, max & prop; P2.23 for 0.20 & le; P & le; 1.13 MPa, etas, max & prop; P1.12 for 0.51 & le; P & le; 1.52 MPa and etas, max & prop; P0.41 for 1.52 & le; P & le; 3.34 MPa. The maximum value of carbon conversion was found to be eta s, max = 27.61% at P = 3.34 MPa.

Download or read book Experimental and Numerical Studies on the Soot Formation of Liquid Fuel Relevant Compounds written by Tongfeng Zhang and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In the present thesis, fundamental experimental and numerical studies are performed for the soot formation of liquid fuel relevant compounds. The thesis is composed of four research studies. The first develops an improved data analysis approach for the combined laser extinction and two-angle elastic light scattering diagnostics to relate the various measured optical cross sections to soot aggregate properties. Compared to previously reported studies, the proposed approach can be applied to a wider range of soot sources by removing the assumption made to scattering regime or moment ratio of aggregate size distribution. The second study investigates the effects of n-propylbenzene addition to n-dodecane on soot formation and aggregate structure in a laminar coflow diffusion flame using the combined laser extinction and two-angle elastic light scattering method. It is shown that the relative importance of soot inception and surface growth affected by n-propylbenzene addition is different along the flame wing and centerline, with the aromatic fuel chemistry effect being stronger along the centerline. The third study extends the investigation on the same issue using a numerical model. The simulation results show that mixing n-propylbenzene into the liquid fuel mixture accelerates soot inception, and increases soot surface growth per unit surface area by PAH addition, while soot surface growth per unit surface area by HACA is shown to decrease modestly with n-propylbenzene addition. The fourth and final study investigates the soot formation from jet fuel in a laminar coflow diffusion flame using both numerical and experimental methods. The results demonstrate the robustness of the soot model to changes of fuel and also show that the HyChem model (i.e., lumped fuel breakdown approach, Xu et al., 2017) can be used to predict soot formation from real jet fuel combustion in laminar coflow diffusion flames by adding a PAH growth scheme to the model.

Download or read book Hydrodynamic Effects on Soot Formation in Laminar Hydrocarbon fueled Diffusion Flames written by Guozheng Lin and published by . This book was released on 1996 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Soot Formation in Co flow and Counterflow Laminar Diffusion Flames of Fuel Mixtures written by Ahmet Emre Karatas and published by . This book was released on 2009 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the formation process of soot in the flames of even-carbon-numbered fuels, acetylene and its derivatives are suspected to be dominant. The addition of an odd-carbon-numbered fuel into these flames introduces methyl radicals and/or C3 chemistries, which are believed to (de)activate certain chemical pathways towards the production of soot. The resultant soot formation rate of the mixture could be higher than the sum of the respective rates of the mixture components, i.e., synergistic effect.In this work, the mixtures of butane isomers, ethylene-butane isomers, and propane-butane isomers were studied on a co-flow and a counterflow burner. Chemical effects were isolated from those of thermal and dilution by mixing isomers and comparing the mixtures including one isomer to those including the counterpart. Line of sight attenuation (LOSA) and laser-light extinction techniques were used for measuring soot volume fraction. The results provide information on synergistic effects in soot formation for the fuels used.

Download or read book Soot Fformation in Co flow and Counterflow Laminar Diffusion Flames of Fuel Mixtures written by Ahmet Emre Karatas and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the formation process of soot in the flames of even-carbon-numbered fuels, acetylene and its derivatives are suspected to be dominant. The addition of an odd-carbon-numbered fuel into these flames introduces methyl radicals and/or C3 chemistries, which are believed to (de)activate certain chemical pathways towards the production of soot. The resultant soot formation rate of the mixture could be higher than the sum of the respective rates of the mixture components, i.e., synergistic eff ect. In this work, the mixtures of butane isomers, ethylene-butane isomers, and propane-butane isomers were studied on a co-flow and a counterflow burner. Chemical effects were isolated from those of thermal and dilution by mixing isomers and comparing the mixtures including one isomer to those including the counterpart. Line of sight attenuation (LOSA) and laser-light extinction techniques were used for measuring soot volume fraction. The results provide information on synergistic effects in soot formation for the fuels used.

Download or read book Understanding Soot Particle Growth Chemistry and Particle Sizing Using a Novel Soot Growth and Formation Model written by Armin Veshkini and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Modelling of Sooting Laminar Diffusion Flames at Elevated Pressures and Microgravity written by Marc Robert Joseph Charest and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Soot Nanostructure Evolution from Gas Turbine Engine Premixed and Diffusion Flame written by Chung-hsuan Huang and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Combustion generated soot impacts human health and climate. Particulate emissions from combustors on jet aircraft are relevant to each area, occurring at ground level and at altitude. One of the advantages of alternative fuels is their potential for reducing emission levels. Comparative field-testing of alternative fuels for their emissions was conducted in the Alternative Aviation Fuel Experiment II (AAFEX II), a NASA-led ground-based field campaign. In this study, particulate emissions from a CFM-56-2C1 engine aboard a DC-9 aircraft were characterized by HRTEM and XPS for nanostructure, carbon speciation and surface chemistry. Fuels studied included JP-8, a 50:50 (JP-8 & HRJ) blend, Hydrotreated Renewable Jet (HRJ), and a Fischer-Tropsch (FT) synthetic fuel. Soot nanostructure and surface chemistry are examined across engine power levels from 4% to 100%. Nanostructure ranged from amorphous (reflecting organic carbon) to graphitic (reflecting elemental carbon) as characterized by lamellae length analysis. With JP-8 fuel, soot particle bonding chemistry, as inferred from the XPS ratio for sp2/sp3 carbon is compared to soot nanostructure evolution. Increasing lamellae length is found to strongly correlate with increasing sp2/sp3 ratio with increasing engine power -- suggesting a change in species identity contributing to the soot growth process. Comparisons between fuels for the same power levels yielded insights into differences in soot processes as dependent upon initial fuel. Soots from the renewable HRJ and FT fuels exhibit significant nanostructure at each power level, rather than the progression as observed for JP-8. This difference is associated with differences in the soot formation environments as dependent upon fuel. To further examine the correlation between chemical environment and soot structure as manifested on different physical length scales, primary particle size versus lamellae length was compared. For JP-8 and its blend with HRJ, there is correlation with engine power, i.e. each spatial metric increases with increasing power, suggesting common underlying cause(s) for both observations. For the HRJ and FT fuels, there is no discernable trend. These results are interpreted in terms of the aromatic content of the JP-8 and blended fuels and their different pyrolysis kinetics compared to paraffinic components of the fuels. Observations of fullerenic nanostructure, particularly evident in soots from the pure paraffinic fuels were interpreted as reflecting partial premixing in order to produce the C5 membered rings for lamellae curvature. This led to the hypothesis defining this study: Partially premixed combustion produces soot with fullerenic nanostructure. Curvature is that one special feature of nanostructure that can be related back to particular gas phase specie(s), namely cyclopentadiene and PAHs containing 5-membered rings.This hypothesis was tested in the following two laboratory flame studies. Partial premixing within simple gas jet diffusion flames has a very long history -- stemming back to the Bunsen flame. Yet HRTEM data of soot from such flames appears absent. In the first study cyclopentane was used as fuel to test lamellae curvature dependence upon C5 species. Modest curvature was observed -- given competing fuel pyrolysis and ring dehydrogenation to yield cyclopentadiene, referred to as C5. Using benzene as the primary fuel with partial premixing tested the chemical path for C5 production -- proceeding through partial benzene oxidation yielding the phenoxy radical followed by CO loss to produce C5. A strong variation of lamellae curvature with oxygen content in the primary fuel stream was observed -- reflecting the increasing C5 production rate. Generality of the nanostructure dependence upon partial premixing and associated change in gas phase chemistry (compared to pure thermal pyrolysis) was demonstrated using an ordinary laboratory Bunsen burner with ethylene as fuel. In absence of partial premixing, soot production is well described by the HACA mechanism, C6 PAHs with observed flat lamellae, without curvature, dissimilar to observations here accompanying partial premixing.In the third study, the main goal was to test two main parameters -- adiabatic flame temperature (2000K) and fuel/air equivalence ratio ([phi] = 2.0) -- for their relative impact on soot nanostructure formation. The soots were collected from a burner-stabilized flat flame burning the petroleum-based JP-8, synthetic FT, and surrogate -- iso-Octane/n-Dodecane, m-Xylene/n-Dodecane, and n-Dodecane -- fuels on a McKenna burner. Images from high-resolution transmission microscopy (HRTEM) show that for the same equivalence ratio of [phi] = 2.0 with temperature maintained constant, soot from the FT fuel has significant curvature compared to soot from the JP-8 fuel, as also found in FT-derived soot from the jet engine. This comparative observation indicates two major findings. First is that the soot nanostructure depends upon initial fuel composition -- and by extension molecular structure. Similar findings from diesel engine studies have also been documented by Yehliu (2010) 1. Second is that fuel pyrolysis pathways and products also depend upon the fuel components. Adjustment of flame adiabatic temperature suggests a temperature threshold for realization of such differences. Soot nanostructure comparisons with a surrogate fuel mixture of n-dodecane/m-xylene (75:25 wt.%) further illustrate pyrolysis processes and intermediates as dependent upon fuel molecular structure and components present. To further compare the experimental results, CHEMKIN with the SERDP mechanism using the burner-stabilized flame model was carried out and processed for the three surrogate fuels, iso-Octane, n-Dodecane, and m-Xylene at various reaction temperatures and fuel/air equivalence ratios. Both the C5H5/C6H6 ratio and C3H3 profiles were distinctly different between the pure n-dodecane and m-xylene/n-dodecane mixture. That the C3H3 profile is also the main difference between the iso-octane and surrogate fuel mix suggests that C3H3 participation in 5-membered ring formation is also key to introduction of 2-D curvature in lamella -- especially given that the highest curvature is observed for FT fuel soot. Moreover, by these results the higher C5H5 observed for the surrogate mixture is an inferred consequence of the different C3H3 profile. Presently these calculated values are only used to interpret the observed curvature differences, as threshold values or the concentration dependency of curvature upon particular species are currently unknown.The goal of this study was to build a bridge between molecular gas phase species and the soot nanostructure. Initial observations of nanostructure curvature in jet engine soot prompted interest. Current chemical kinetic models can address fuel breakdown, thermal and oxidatively assisted, PAH formation and growth all via detailed kinetics, followed by soot inception via their physical and chemical coalescence. Thereafter soot models are particle based and use measured growth rates and aerosol dynamics to account for increasing soot mass and aggregate formation. No modeling studies have yet addressed the link between gas phase species with any aspect of soot nanostructure. As shown here soot nanostructure can reflect its origin, specifically the species forming the soot lamellae. The novelty of two-dimensional curvature is that it can be related uniquely to C5 species, via known chemical pathways -- involving oxygen directly or indirectly. The oxygen concentration in the primary fuel stream defines the level of partial premixing. Therein lies the origin of the hypothesis that partial premixing leads to (recognizable) curvature in soot lamellae. Definition of the operative range of [phi] and temperature will constitute future work for C5 production and its manifestation as curvature in nanostructure.

Download or read book Soot Formation in Non premixed Laminar Flames at Subcritical and Supercritical Pressures written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental study was conducted using axisymmetric co-flow laminar diffusion flames of methane-air, methane-oxygen and ethylene-air to examine the effect of pressure on soot formation and the structure of the temperature field. A liquid fuel burner was designed and built to observe the sooting behavior of methanol-air and n-heptane-air laminar diffusion flames at elevated pressures up to 50 atm. A non-intrusive, line-of-sight spectral soot emission (SSE) diagnostic technique was used to determine the temperature and the soot volume fraction of methane-air flames up to 60 atm, methane-oxygen flames up to 90 atm and ethylene-air flames up to 35 atm. The physical flame structure of the methane-air and methane-oxygen diffusion flames were characterized over the pressure range of 10 to 100 atm and up to 35 atm for ethylene-air flames. The flame height, marked by the visible soot radiation emission, remained relatively constant for methane-air and ethylene-air flames over their respected pressure ranges, while the visible flame height for the methane-oxygen flames was reduced by over 50 % between 10 and 100 atm. During methane-air experiments, observations of anomalous occurrence of liquid material formation at 60 atm and above were recorded. The maximum conversion of the carbon in the fuel to soot exhibited a strong power-law dependence on pressure. At pressures 10 to 30 atm, the pressure exponent is approximately 0.73 for methane-air flames. At higher pressures, between 30 and 60 atm, the pressure exponent is approximately 0.33. The maximum fuel carbon conversion to soot is 12.6 % at 60 atm. For methane-oxygen flames, the pressure exponent is approximately 1.2 for pressures between 10 and 40 atm. At pressures between 50 and 70 atm, the pressure exponent is about -3.8 and approximately -12 for 70 to 90 atm. The maximum fuel carbon conversion to soot is 2 % at 40 atm. For ethylene-air flames, the pressure exponent is approximately 1.4 between 10 and 30 atm. The maximu.