Download or read book Computational Study of the Effect of Pressure on Soot Formation in Laminar Premixed Flames written by Andrei F. Kazakov and published by . This book was released on 1997 with total page 566 pages. Available in PDF, EPUB and Kindle. Book excerpt: Offers a computational study of the effect of pressure on soot formation in laminar premixed flames. An existing detailed kinetic model of soot formation validated previously for low-pressure and atmospheric laminar premixed flames is extended to account for the effects associated with elevated-pressure conditions. Detailed analysis of the model predictions is then used to gain a physical understanding of the experimentally observed trends in soot formation caused by elevated pressures.

Download or read book Development of Predictive Reaction Models of Soot Formation written by and published by . This book was released on 1993 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the second twelve-month period of the project, progress has been made in the following areas: (1) The computational study of sooting limits in laminar premixed flames was completed. It was found that the critical equivalence ratios for soot appearance, both the absolute values and temperature dependencies, can be predicted fairly close to the experimental observations. Sensitivity and reaction path analyses were performed to examine the factors responsible for the predicted behavior. (2) New estimation techniques were developed and applied for calculations of standard-state enthalpies of formation and binary gaseous diffusion coefficients Of polyCyCl4C aromatic hydrocarbons (PAHs) and their radicals, thus providing critical information for accurate modeling of soot formation in flames. (3) Theoretical studies of a bench-mark ion-molecule reaction were completed. (4) Computer simulations of the effect of pressure on soot formation were initiated. (5) Several manuscripts summarizing the results obtained have been completed and submitted for publication.

Download or read book Soot Formation in Combustion written by Henning Bockhorn and published by Springer Science & Business Media. This book was released on 2013-03-08 with total page 595 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soot Formation in Combustion represents an up-to-date overview. The contributions trace back to the 1991 Heidelberg symposium entitled "Mechanism and Models of Soot Formation" and have all been reedited by Prof. Bockhorn in close contact with the original authors. The book gives an easy introduction to the field for newcomers, and provides detailed treatments for the specialists. The following list of contents illustrates the topics under review:

Download or read book Laminar Soot Processes Lsp written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the final report of a research program considering the structure and the soot surface reaction properties of laminar nonpremixed (diffusion) flames. The study was limited to ground-based measurements of buoyant laminar jet diffusion flames at pressures of 0.1-1.0 atm. The motivation for the research is that soot formation in flames is a major unresolved problem of combustion science that influences the pollutant emissions, durability and performance of power and propulsion systems, as well as the potential for developing computational combustion. The investigation was divided into two phases considering the structure of laminar soot-containing diffusion flames and the soot surface reaction properties (soot surface growth and oxidation) of these flames, in turn. The first phase of the research addressed flame and soot structure properties of buoyant laminar jet diffusion flames at various pressures. The measurements showed that H, OH and O radical concentrations were generally in superequilibrium concentrations at atmospheric pressure but tended toward subequilibrium concentrations as pressures decreased. The measurements indicated that the original fuel decomposed into more robust compounds at elevated temperatures, such as acetylene (unless the original fuel was acetylene) and H, which are the major reactants for soot surface growth, and that the main effect of the parent fuel on soot surface growth involved its yield of acetylene and H for present test conditions. The second phase of the research addressed soot surface reaction properties, e.g., soot surface growth and surface oxidation. It was found that soot surface growth rates in both laminar premixed and diffusion flames were in good agreement, that these rates were relatively independent of fuel type, and that these rates could be correlated by the Hydrogen-Abstraction/Carbon-Addition (HACA) mechanisms of Colket and Hall (1994), Frenklach et al. (1990,1994), and Kazakov et al. (1995). It was also fou

Download or read book Effect of Pressure on Soot Formation in Laminar Diffusion Flames written by Adel Maurice Iskander and published by . This book was released on 1987 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Computational Study of Soot Formation and Flame Structure of Coflow Laminar Methane air Diffusion Flames Under Microgravity and Normal Gravity written by and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Prediction of Soot Formation in Laminar Opposed Diffusion Flame with Detailed and Reduced Reaction Mechanisms written by Hojoon Chang and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The present work focuses on a computational study of a simplified soot model to predict soot production and destruction in methane/oxidizer (O2 and N2) and ethylene/air flames using a one-dimensional laminar opposed diffusion flame setup. Two different detailed reaction mechanisms (361 reactions & 61 species for methane/oxidizer flame and 527 reactions & 99 species for ethylene/air flame) are used to validate the simplified soot model in each flame. The effects of strain rate and oxygen content on the soot production and destruction are studied, and the soot related properties such as soot volume fraction, particle number density and particle diameter are compared with published results. The results show reasonable agreement with data and that the soot volume fraction decreases with higher strain rate and lower oxygen content. The simplified soot model has also been used with two reduced reaction mechanisms (12-step, 16-species for methane flame and 20-species for ethylene flame) since such reduced mechanisms are computationally more efficient for practical application. The profiles of the physical properties and the major species are in excellent agreement with the results using the detailed reaction mechanisms. However, minor hydrocarbon-species such as acetylene (C2H2) that is the primary pyrolysis species in the simplified soot model is significantly over predicted and this, in turn, results in an over-prediction of soot production. Finally, the reduced reaction mechanism is modified to get more accurate prediction of the minor hydrocarbon-species. The modified reduced reaction mechanism shows that the soot prediction can be improved by improving the predictions of the key minor species.

Download or read book Detailed Studies of Soot Formation in Laminar Diffusion Flames for Application to Modeling Studies written by and published by . This book was released on 1993 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: An investigation of soot formation in laminar diffusion flames has shown that soot particle surface growth under laminar diffusion flame conditions ceases because of the depletion of hydrocarbon species, in particular acetylene and benzene, and not due soot particle reactivity loss due to thermal aging of the particles. This results has been obtained through direct species concentration measurements under well controlled conditions while the particle reactivity effects were calculated based on premixed flame results along with particle temperature/time information available from earlier laminar diffusion flame studies. Comparisons with a soot formation model which incorporated detailed chemistry effects showed good agreement in terms of predicted and measured species concentration and soot particle field evolution. In addition, a novel technique for measuring soot volume fraction has been developed based on laser-induced incandescence and applied to similar laminar diffusion flame, studies with good success. This technique represents a major development in terms of its ability to make soot volume fraction measurements in unsteady inhomogeneous combusting flows. Soot formation, Soot particles, Diffusion flames.

Download or read book Effects of Elevated Pressure on Soot Formation in Laminar Diffusion Flames written by L. L. McCrain 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 Soot Formation in Non premixed Laminar Flames at Subcritical and Supercritical Pressures written by Hyun Il Joo and published by . This book was released on 2010 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 maximum carbon conversion to soot is approximately 6.5 % at 30 atm and remained constant at higher pressures.

Download or read book Effects of Pressure on the Mechanisms of Soot Formation and Oxidation in Laminar Diffusion Flames written by Chul Han Kim and published by . This book was released on 2005 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Multi Scale Investigations in Soot Formation and Chemical Vapor Deposition written by Abhishek Jain and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Progress is made in this thesis in understanding the complex multi-scale chemical and physical processes governing the formation of condensed phase material from gaseous species. The formation of soot through combustion and the synthesis of functional nanomaterial through chemical vapor deposition (CVD) are examined. We first attempt to characterize the sooting tendencies of alternative fuels using different techniques. A new numerical model based on modified flamelet equations is used along with a modified chemical mechanism to predict the effect of fuel molecular structure on soot yield in gasoline surrogates. These simulations provide trends on sooting behavior and are one-dimensional calculations that neglect other phenomenon that govern soot yield and distribution. To determine how other factors influence sooting behavior in laminar flames we carry out experimental and numerical studies to understand how the addition of oxygen to the oxidizer changes soot yield and distribution. Finite-rate chemistry based Direct Numerical Simulations (DNS) are carried out for a series of methane/air flames with increasing Oxygen Index (OI) using an extensively validated, semi-detailed chemical kinetic mechanism, along with an aggregate-based soot model and the results are compared with experimental measurements. It is seen that the effect of variable OI is well captured for major flame characteristics including flame heights, soot yield, and distribution by the numerical simulations when compared to the experimental data. This study is however confined to a small fuel that may not represent behavior seen in real fuels or the constituents that make up these gasoline fuels or their surrogates. Thus, we examine the effects of premixing on soot processes in an iso-octane coflow laminar flame at atmospheric pressure. Iso-octane is chosen as a higher molecular weight fuel as it is an important component of gasoline and its surrogates. Flames at different levels of premixing are investigated ranging from jet equivalence ratios of 1 (non-premixed), 24, 12, and 6. Numerical simulations are compared against experimental measurements and good agreement is seen in soot yield and soot spatial distributions with increasing levels of premixing. While the above studies for soot were carried out for laminar flames combustion devices frequently operate at conditions that lead to turbulent flow. Therefore, to understand how soot is affected by turbulence we computationally study the effects large Polycyclic Atromatic Hydrocarbons species (PAH) have on soot yield and distribution in turbulent non-premixed sooting jet flames using ethylene and and jet fuel surrogate (JP-8). The effects of large PAH on soot are highlighted by comparing the PAH profiles, soot nucleation rate, and soot volume fraction distributions obtained from both simulations for each test flame. Comparisons are also made with experiments when available and further analysis is performed to determine the cause of the observed behavior. Finally, a new multi-scale model is proposed for the computational modeling of the synthesis of functional nanomaterials using CVD. The proposed model is applied to a W(CO)6/H2Se system that has been used by researchers at Penn State to perform WSe2 crystal growth. A force-field for W/C/O/H/Se is developed and favorable agreement is seen when compared to QM data. A reaction mechanism leading from W(CO)6 and H2Se to the crystal precursor is then developed and used in a reacting flow simulation of the custom CVD chamber at Penn State. The bulk reacting flow numerical predictions show promising results for the gas-phase and precursor species, while additional work is still being performed to make the method more robust.

Download or read book Soot and Pah Formation in Counterflow Non premixed Flames Atmospheric Butane and Butanol Isomers and Elevated pressure Ethylene written by Pradeep K Singh and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the complexity of the fluid dynamics and non-linear reactions in the combustion zone, a simplified approach to study this process is required. Given these complexities, it is practically very challenging to take measurements in very high temperature and pressure zones in practical combustion systems, and if by any means those measurements can be made, it is equally challenging to analyze those measurements. Hence, in order to more comprehensively understand these processes, the problem needs to be resolved into the smaller and controllable sub-category of experiments, by creating laminar flamelets. One approach used in creating these flamelets is by establishing simplified non-premixed flames in the counterflow configuration. Alongwith all the fundamental properties of combustion, it is important to study the health hazard and environmentally detrimental emissions, such as soot and polycyclic aromatic hydrocarbons (PAHs). Such combustion studies need to be carried out using the non-intrusive in-situ optical diagnostics measurement techniques, such as the Laser Induced Incandescence (LII), Planar Laser Induced Fluorescence (PLIF) and Light Extinction (LE). These measurements for renewable biofuels aid in better understanding of the soot formation process, as well as in developing the fuel specific knowledge to bring them into commercial use. Furthermore since the most practical combustion systems operate at elevated pressures, it is also important to understand the soot formation process under elevated pressure conditions. Considering these, in the current study, the soot and PAH formation processes for butane and butanol isomers (C4 fuels) at atmospheric pressure; and for ethylene at elevated pressure have been experimentally investigated and compared in a counterflow non-premixed flame configuration. Under the investigated conditions, butane isomers were observed to form more soot than butanol isomers, thereby showing the effect of the hydroxyl group. The effects of isomeric structural differences on sooting propensity were also observed within the butane and butanol isomers. In addition, while soot volume fraction was seen to increase with increasing fuel mole fraction, the ranking of sooting propensity for these C4 fuels remained unchanged. For the conditions studied, the sooting tendency ranking generally follows n-butane > iso-butane > tert-butanol > n-butanol > iso-butanol > sec-butanol. . The counterflow non-premixed flames were also simulated using the gas-phase chemical kinetic models, USC Mech II [1], Sarathy et al. [2] and Merchant et al. [3] available in the literature to compute the spatially-resolved profiles of soot precursors, including acetylene and propargyl. For these C4 fuels, the PAHs of various aromatic ring size groups (2, 3, 4, and larger aromatic rings) have been characterized and compared in non-premixed combustion configuration. In particular, the formation and growth of the PAHs of different aromatic ring sizes in these counterflow flames was examined by tracking the PAH-PLIF signals at various detection wavelengths. PAH-PLIF experiments were conducted, by blending each of the branched-chain isomers with the baseline straight-chain isomer, in order to study the synergistic effects. The fuel structure effects on the PAH formation and growth processes were also analyzed by comparing the PAH growth pathways for these C4 fuels. A chemical kinetic model, POLIMI mechanism [4-7], available in the literature that includes both the fuel oxidation and the PAH chemistry was also used to simulate and compare the PAH species up to A4 rings. Counterflow non-premixed sooting ethylene‒air flames with fuel mole fractions of 0.20‒0.40 in the pressure range of 1‒6 atm were investigated experimentally with the laser diagnostic techniques of LII, PLIF and LE. A better understating of the quantitative soot formation process has been developed for ethylene counterflow flames under elevated pressure conditions. The effect of pressure on the formation of PAHs with different aromatic ring sizes has also been determined qualitatively. With increase in pressure, the increase in soot volume fraction and PAH-PLIF signals were observed. A chemical kinetic model available in the literature, that includes both the fuel oxidation and the PAH chemistry, was also used to simulate and compare the PAH species up to A4 rings. At the incipient stage of the PAH formation, the simulated results exhibited similar behavior to the experimental observations. A chemical kinetic model, WF-PAH mechanism [8], available in the literature was also used to compute the PAHs up to four aromatic rings. This chemical kinetic model predicted enhancing PAHs formation with an increase in pressure, consistent with the experimental trend.

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.

Download or read book Particulate Carbon written by Donald Siegla and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of the symposium, "Particulate Carbon: Formation During Combustion", held at the General Motors Research Laboratories on October 15 and 16, 1980, was to discuss fundamental aspects of soot formation and oxidation in combustion systems and to stimulate new research by extensive interactions among the participants. This book contains lhe papers and discussions of that symposium, the 26th in an annual series covering many different disciplines which are timely and of interest to both General Motors and the technical community at large. The subject of this symposium has considerable relevance for man in his effort to control and preserve his environment. Emission of particulate carbon into the atmos phere from combustion sources is of concern to scientists and laymen alike. The hope of reducing this emission clearly requires an understanding of its formation during the combustion process, itself an area of considerable long-term research interest. It is our hope that this symposium has served to summarize what is known so that what remains to be learned can be pursued with greater vigor.

Download or read book Numerical Simulation of AxiSymmetric Laminar Diffusion Flames with Soot written by Adhiraj Dasgupta and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Detailed numerical modeling of combustion phenomena, soot formation, and radi-ation is an active area of research. In this work a general-purpose, pressure-based,finite volume code for modeling laminar diffusion flames has been incorporatedinto the CFD code OpenFOAM. The code uses a mixture-averaged model for thecalculation of transport coefficients, and can be used to perform detailed modelingof multi-dimensional laminar flames using realistic molecular transport, and withdetailed chemical mechanisms containing hundreds of chemical species and reac-tions. Two soot models have been incorporated into the code: a semi-empiricaltwo-equation model, as well as a detailed Method of Moments with InterpolativeClosure (MOMIC). An emission-only, optically-thin radiation model has also beenincluded in the code to account for the radiative heat loss, and sophisticated radia-tion models with detailed calculations of spectral properties and radiative intensityhave also been included. The flame code showed excellent scalability on massivelydistributed, high-performance computer systems. The code has been validated bymodeling four axisymmetric, co-flowing laminar diffusion flames, and the resultshave been found to be mostly within experimental uncertainty, and comparableto results reported in the literature for the same and similar configurations. Anumber of parametric studies to study the effects of detailed gas-phase chemistry,soot models and radiation have also been performed on these flame configurations.It has been found that the flames considered in this work are all optically thin,and so the simple, emission-only, optically-thin radiation model can be used tomodel these flames with good accuracy and a reasonable computational effort. Inparticular, the detailed radiation models increase the computational cost by twoorders of magnitude, and thus their applicability in a detailed calculation may belimited.It was found that the two-equation soot model used in conjunction with a gas-phase mechanism that adequately describes the combustion of C2 hydrocarbons produces results in close agreement with experimental data for a 1-bar ethylene-airflame, a 10 bar methane-air flame, as well as an ethane-air flame at 10 bar. Thedetailed MOMIC soot model requires the use of a larger, more detailed gas-phasechemical mechanism containing polycyclic aromatic hydrocarbons (PAH) with fourrings, and thus the computational cost associated with the MOMIC soot modelis significantly higher. The detailed model was used to model the flames, andcomputed soot levels were within a factor of two of the experimental values, whichis typically considered good agreement considering the complex physics involved.The last flame studied using both the soot models was a N2 -diluted ethylene-airflame, in which the predicted values of major gas-phase species were seen to be closeto the experimental values, but the soot levels were off by an order of magnitude.Notwithstanding the lack of agreement with measurements for this flame, the flamesolver with the soot models was demonstrated to be a robust, scalable, and generalcode with potential applications to a variety of laminar flames in the non-premixed,partially premixed and premixed regimes.

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: