Soot Formation in Annular Non-premixed Laminar Flames of Methane-air at Pressures of 0.1 to 4.0 MPa [microform] PDF Download

Author: Kevin Austen Thomson
Publisher: Library and Archives Canada = Bibliothèque et Archives Canada
ISBN: 9780494029565
Category :
Languages : en
Pages : 592

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Author: Hyun Il Joo
Publisher:
ISBN:
Category :
Languages : en
Pages :

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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.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

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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.

Author: Marie Emma Vaillancourt
Publisher:
ISBN: 9780494210178
Category : Combustion
Languages : en
Pages : 190

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Measurements of soot concentration, flame temperature and flame geometry have been recorded for non-smoking methane-air laminar diffusion flames at pressures from P = 1.5 MPa to P = 6.0 MPa. Soot concentration and temperature profiles were obtained using the spectral soot emission diagnostic method and the Abel inversion deconvolution technique. Visual inspection and measurement of the flame revealed a slight increase in height and decrease in cross-section with increasing pressure. Soot volume fraction increased with pressure according to fv max & prop; P1.4 for 1.5 & le; P & le; 5.0 MPa. The maximum carbon conversion to soot was related to pressure following the relationship eta s, max & prop; P0.55 for 1.5 & le; P & le; 5.0 MPa. The maximum value of carbon converted to soot was etas, max = 10.1% at P = 5.0 MPa. The maximum soot concentration was always found at a height approximately half way between the burner and the flame tip. The temperature was lower in high soot loading regions of the flame. For the same height in the flame, temperature decreased with increasing pressure.

Author: Michael I. B. Chai
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Soot is an important air pollutant. Its formation must be modeled accurately to assist designers in development of low soot emission combustors. This study was concerned with the semi-empirical modeling of soot. The models considered inception, coagulation, agglomeration, and oxidation of the soot particles. Since inception is a key process in the development of soot it was studied in great detail. Two approaches to modeling inception were investigated: acetylene and phenyl. For a methane/air coflow diffusion flame at a pressure of one atmosphere both approaches showed good agreement with experimentally observed trends. Furthermore, the acetylene route under predicted the magnitude of the soot volume fraction while the phenyl route over predicted the magnitude of the soot volume fraction. However, it is believed that the phenyl model will perform better with more complex fuels such as kerosene and with improved laminar flamelet libraries that are optimized for C6 species.

Author: Decio S. (Decio Santos) Bento
Publisher: Library and Archives Canada = Bibliothèque et Archives Canada
ISBN: 9780494024430
Category : Combustion
Languages : en
Pages : 158

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Laminar axisymmetric propane air diffusion flames were studied at pressures 0.1 to 0.725 MPa (1 to 7.25 atm). To investigate the effect of pressure on soot formation, radially resolved soot temperatures and soot volume fractions were deduced from soot radiation emission scans collected at various pressures using spectral soot emission (SSE). Overall flame stability was quite good as judged by the naked eye. Flame heights varied by 15% and flame axial diameters decreased by 30% over the entire pressure range.Analysis of temperature sensitivity to variations in E lambda(m) revealed that a change in E lambda(m) of +/-20% produced a change in local temperature values of about 75 to 100 K or about 5%.Temperatures decreased and soot concentration increased with increased pressure. More specifically, the peak soot volume fraction showed a power law dependence, fv ∝ Pn where n = 2.0 over the entire pressure range. The maximum integrated soot volume fraction also showed a power law relationship with pressure, f ̄v ∝ Pn where n = 3.4 for 1 ≤ P ≤ 2 atm and n = 1.4 for 2 ≤ P ≤ 7.25 atm. The percentage of fuel carbon converted to soot increased with pressure at a rate, etas ∝ Pn where n = 3.3 and n = 1.1 for 1 ≤ P ≤ 2 atm and 2 ≤ P ≤ 7.25 atm respectively.

Author: Gorngrit Intasopa
Publisher:
ISBN: 9780494761816
Category :
Languages : en
Pages : 208

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Methane-air, ethane-air, and n-heptane-air over-ventilated co-flow laminar diffusion flames were studied up to pressures of 2.03, 1.52, and 0.51 MPa, respectively, to determine the effect of pressure on flame shape, soot concentration, and temperature. A spectral soot emission optical diagnostic method was used to obtain the spatially resolved soot formation and temperature data. In all cases, soot formation was enhanced by pressure, but the pressure sensitivity decreased as pressure was increased. The maximum fuel carbon conversion to soot, etamax, was approximated by a power law dependence with the pressure exponent of 0.92 between 0.51 and 1.01 MPa, and 0.68 between 1.01 and 2.03 MPa with etamax=9.5% at 2.03 MPa for methane-air flames. For ethane-air flames, the pressure exponent was 1.57 between 0.20 and 0.51 MPa, 1.08 between 0.51 and 1.01 MPa, and 0.58 between 1.01 and 1.52 MPa where etamax=23% at 1.52 MPa. For nitrogen-diluted n-heptane-air flames, etamax=6.5% at 0.51 MPa.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 8

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Author: Arup Barua
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Abhishek Jain
Publisher:
ISBN:
Category :
Languages : en
Pages :

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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.