Optical Properties of Soot Particles in Flames by Classical and Dynamic Light Scatterng PDF Download

Author: Tryfon Theodoroy Charalampopoulos
Publisher:
ISBN:
Category :
Languages : en
Pages : 324

View

Book Description

Author: David R. Schryer
Publisher:
ISBN:
Category : Light
Languages : en
Pages : 28

View

Book Description

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

View

Book Description
Soot aerosols are well known to be atmospheric constituents, but the hydrophobic nature of fresh soot likely prohibits them from encouraging cloud development. Soot aged through contact with oxygenated organic compounds may become hydrophilic enough to promote water uptake. In this study, the tandem differential mobility analyzer (TDMA) and differential mobility analyzer-aerosol particle mass analyzer (DMA-APM) were employed to measure the changes in morphology and hygroscopicity of soot aerosol particles upon coating with succinic and glutaric acids. The effective densities, fractal dimensions and dynamic shape factors of fresh and coated soot aerosol particles have been determined. Significant size-dependent increases of soot particle mobility diameter, mass, and effective density ([rho]eff) were observed upon coating of aggregates with succinic acid. These properties were restored back to their initial states once the acid was removed by heating, suggesting no restructuring of the soot core had occurred. Coating of soot with glutaric acid, on the other hand, leads to a strong size shrinking with a diameter growth factor ~0.60, even after the acid has been removed by heating suggesting the strong restructuring of the soot agglomerate. The additional 90% RH cycle can evidently enhance the restructuring process. The extinction and scattering properties at 532 nm of soot particles internally mixed with dicarboxylic acids were investigated experimentally using a cavity ring-down spectrometer and an integrating nephelometer, respectively, and the absorption is derived as the difference between extinction and scattering. It was found that the organic coatings significantly affect the optical and microphysical properties of the soot aggregates. The size-dependent amplification factors of light scattering were as much as 3.8 and 1.7 with glutaric and succinic acids coatings, respectively. Additional measurements with soot particles that are first coated with glutaric acid and then heated to remove the coating show that both scattering and absorption are enhanced by irreversible restructuring of soot aggregates to more compact globules. These results reveal the microphysical state of soot aerosol with incomplete restructuring in the atmosphere, and advance the treatment of atmospheric aged soot aerosol in the Mie theory shell-and-core model.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 26

View

Book Description

Author:
Publisher:
ISBN:
Category : Mathematics
Languages : en
Pages : 1298

View

Book Description
Publishes research papers in the mathematical and physical sciences. Continues: Proceedings of the Royal Society of London. Series A, Mathematical and physical sciences. Continued by: Proceedings. Mathematical, physical, and engineering sciences.

Author: G. M. Faeth
Publisher:
ISBN:
Category :
Languages : en
Pages : 130

View

Book Description
Measured soot optical properties were in good agreement with the predictions of RDG-PFA theory over a broad test range, as follows: soot from both the fuel-rich and fuel-lean regions of buoyant diffusion flames, wavelengths of 350-800 nm, primary particle size parameters as large as 0.46, and soot formed in diffusion flames burning in air for a variety of gaseous and liqud hydrocarbon fuels (acetylene, ethylene, propylene, butadiene, benzene, cyclohexane, toluene and n-heptane).

Author: Sivakumar Santhanakrishnan
Publisher:
ISBN:
Category :
Languages : en
Pages : 372

View

Book Description

Author: Sandra Török
Publisher:
ISBN: 9789178959716
Category :
Languages : en
Pages :

View

Book Description
The formation path from small poorly absorbing incipient soot to larger fractal-like strongly absorbing black soot is extensive, and along this path the optical and physicochemical properties of the soot evolve. Soot emitted into the atmosphere may originate from some stage of this process, which will result in a wide spectrum of carbonaceous aerosols in the atmosphere which may interact with the sun and influence the radiative balance of the earth.?In this work, differently matured soot from a mini-CAST soot generator was studied in terms of optical properties and the relation to its physicochemical properties. Various optical diagnostic tools, mainly multi-wavelength extinction, elastic light scattering (ELS), and laser-induced incandescence (LII), but also complementary aerosol instrumentation, were used for these purposes. These tools have provided generic information about soot properties, and additionally the applicability of the methods for soot analysis has been evaluated.?Soot from the mini-CAST was found to have properties which range from nm-sized soot with optical properties of brown carbon (BrC) to larger soot aggregates of black carbon (BC) type. It was shown that the BrC type of soot had a refractory soot core with properties similar to young soot. Hence, it was shown to not consist of a BC core with a BrC like coating. Also it was shown that upon heating during thermo-optical analysis in an inert atmosphere that the BrC soot transformed and became more absorbing.?LII was used to study the optical properties of soot, and it was shown that the optical properties of mature soot agreed well with results from extinction measurements, but for young soot LII results indicated absorption of slightly more mature soot character. Further analysis of the temperature evolution of the soot in the low fluence regime allowed for estimation of the soot absorption efficiency. Results showed large differences in absorption efficiencies for the differently matured soot and values for the mature soot agreed well with values presented in the literature.?Double-pulse LII experiments showed how rapid laser heating induced changes in soot of different maturity. It was shown that the absorption properties were enhanced as a result of thermal annealing for all soot with the strongest effect for young soot. Another effect for young soot (using LII at 532 nm excitation) was an increased fluorescence from vaporized fragments that potentially can interfere with the detection of LII signals.?A nephelometer was used to study the elastic scattering by soot particles, and it was investigated if scattering theory could be used to solve the inverse problem and obtain information on the morphological properties. The method appeared feasible as tests revealed good results when compared to results based on micrograph image analysis. The method may be useful for estimation of morphological properties of fractal-like soot, as it provides a faster and less elaborate estimation than microscopy analysis.?The findings of this work contribute to the understanding of how differently matured soot interact with electromagnetic radiation, especially for the laser-induced incandescence method. Hence information has been gained on how to optimise the diagnostic potential of LII as well as on limitations in the diagnostics of soot of different maturity.?

Author: Boyang Zhao
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 56

View

Book Description
Optical properties, i.e. scattering coefficient and absorption coefficient, of soot aerosol particles were investigated as they restructure during a simulated atmospheric ageing process. The soot particles were generated by a McKenna burner and injected into a smog chamber after being denuded and size selected. In the smog chamber, the soot restructuring process was induced by formation of a secondary organic aerosol (SOA) coating, which was generated by the photo-oxidation reaction of the SOA precursor p-xylene with OH radical. The particle diameter, mass, scattering and absorption coefficients were monitored with a scanning mobility particle sizer, a centrifugal particle mass analyzer, and a photoacoustic extinctiometer, respectively. Effective density and shape factor for the particles were determined to assess the degree of restructuring. Experiments were done at different relative humidities (RH) and I found that higher RH leads to a faster restructuring process. Mass scattering cross-section, mass absorption cross-section, and mass absorption cross-section with respect to bare soot particles were calculated to show how scattering and absorption are affected by the restructuring process. Under all RH conditions, the mass scattering cross-section increased for both coated and denuded soot particles. The mass absorption cross-section with respect to bare soot particle shows an increasing trend for coated soot particles as the mass growth factor increases. High and low RH conditions give rise to a higher value of mass absorption cross-section with respect to bare soot particles compared to intermediate RH conditions (RH=40%). The mass absorption cross-section value with respect to bare soot particles for intermediate RH is about 30% less than those for low and high RH. The overall work can provide optical information to the process of soot particles restructuring induced by SOA coating under different RH conditions.

Author: Harjit Singh Hura
Publisher:
ISBN:
Category :
Languages : en
Pages : 224

View

Book Description