The size of a soot particle has an effect on smoke detector alarm activation. It is the purpose of this paper to identify changes to soot particle size and examine if those size changes effect smoke detector alarm times in the ceiling jet. Changes in particle size has been attributed to delays in detector activation, however, little evidence exists to support that particle size changes occur in the ceiling jet where detector activation occurs. This paper presents the results from laser scattering experiments and calculations conducted to support and validate the experimental findings. The laser scattering from various aerosols was collected, over time, to examine changes in particle size due to agglomeration in the smoke aging process. The laser scattering measurements were made at two linear polarizations, vertical (VV) and horizontal (HH), and scattering angles ranging from 20 to 155 degrees. A laser with a wavelength of 632.8 nm was used as a light source. The aerosol laser scattering results were then compared to the results from the Mie scattering theory. The Mie scattering theory was adjusted using a lognormal distribution to generate theoretical light scattering curves expected from a polydisperse aerosol typical of smoke. The collected data was examined using a combination of the Mie theory with various particle sizing techniques, including dissymmetry ratio and polarization ratio, to look for changes in laser scattering indicating changes in particle size.

Cette thèse a pour objet d'améliorer la connaissance du mécanisme de formation de suie. Deux méthodes ont été utilisées pour produire des particules de suie dans des conditions contrôlées : le brûleur à flamme plat où les particules se forment par combustion de mélanges d'éthylène/air riches et le tube à choc dans lequel la suie est produite par pyrolyse de C2H4 à haute pression (5 bar) et dans un large domaine de température (1850-2100 K). Ces deux systèmes ont été équipés avec un dispositif original de diffusion laser à trois angles couplé à l’extinction laser pour suivre la croissance de particules, identifier les différentes étapes de leur mécanisme de formation et en déduire l'évolution de la fraction volumique des suies, leur rendement, leur structure et leur morphologie. Dans la flamme, l’addition de H2 entraîne une réduction globale de la concentration des suies, de leur diamètre moyen des particules et leurs agglomérats, de la densité en nombre de particules. Dans le tube à choc, on n’observe pas de dépendance significative du délai d'induction à la formation des particules par addition de H2. La courbe de rendement en suie en fonction de la température présente la même forme avec et sans hydrogène mais le rendement maximal est fortement abaissé en présence d’hydrogène pour une concentration initiale fixée en atomes de carbone. Le rôle de l’hydrogène sur la croissance des particules et les caractéristiques des suies est discuté en comparant les résultats obtenus dans le cas de la flamme de prémélange et derrière l’onde de choc réfléchie respectivement. / The aim of this thesis was to improve the knowledge of the soot formation mechanism. Two methods have been used to produce soot particles in controlled conditions: flat flame burner where particles were formed by combustion of rich ethylene/air mixtures and shock tube in which soot was produced by C2H4 pyrolysis at high pressure (5 bar) and in a large range of temperature (1850-2100 K). Both systems have been equipped with a novel technique of scattering at three angles coupled with laser extinction device in order to follow particles growth, to identify different steps of their formation mechanism and to deduce soot volume fraction evolution, soot yield, structure and morphology. In the flame, an overall reduction of soot concentration, mean volume diameter, particles number density was observed when hydrogen was added to combustible mixture. In shock tube, induction delay time of particle formation does not depend on H2 addition. The typical curves of soot yield versus temperature present the same shape with and without H2 ; the maximum yield occurs at the same temperature (near 2000 K) but the yield is strongly lower in presence of H2 for a given C atom concentration. The role of hydrogen on particles growth rate and soot characteristics was discussed by comparing the results obtained respectively in the premixed flames and behind reflected shock waves.

Šiame darbe yra aptariama sklaidos matavimo sistema sukurta plačioje spektro srityje reikalingiems matavimams atlikti. Joje naudojami parametriniai šviesos generatoriai bei harmonikų generatoriai, kaupinami nanosekundinės trukmės impulsais, ir apibendrinami sklaidos tyrimai, atlikti įvairių tipų optinėse dangose ir netiesiniuose optiniuose kristaluose, naudojant derinamojo bangos ilgio lazerinius impulsus. Pirmą kartą buvo ištirti naujų netiesinėje optikoje perspektyvių LiInS2 ir LiInSe2 kristalų sklaidos nuostoliai infraraudonojoje srityje. Taip pat parodyta, kad koherentinės sklaidos tomografijos metodas, anksčiau taikytas puslaidininkinių kristalų tūriniams defektams tirti, yra tinkamas ir netiesinėje optikoje naudojamų kristalų kokybės tyrimams. / This work describes the system for the light scattering measurements in a wide spectral range, which uses the light parametric oscillators and harmonic generators pumped with a nanosecond pulses and summarizes the research in various types of coatings on optical components and inside nonlinear optical crystals. The total scattering losses for the first time were characterized in the infrared region for a new promising in nonlinear optics LiInS2 and LiInSe2 crystals. It was shown that the laser scattering tomography, previously used for investigation of volume defects in semiconductor crystals, can be applied in the nonlinear optical quality control.

This work describes the system for the light scattering measurements in a wide spectral range, which uses the light parametric oscillators and harmonic generators pumped with a nanosecond pulses and summarizes the research in various types of coatings on optical components and inside nonlinear optical crystals. The total scattering losses for the first time were characterized in the infrared region for a new promising in nonlinear optics LiInS2 and LiInSe2 crystals. It was shown that the laser scattering tomography, previously used for investigation of volume defects in semiconductor crystals, can be applied in the nonlinear optical quality control. / Šiame darbe yra aptariama sklaidos matavimo sistema sukurta plačioje spektro srityje reikalingiems matavimams atlikti. Joje naudojami parametriniai šviesos generatoriai bei harmonikų generatoriai, kaupinami nanosekundinės trukmės impulsais, ir apibendinami sklaidos tyrimai, atlikti įvairių tipų optinėse dangose ir netiesiniuose optiniuose kristaluose, naudojant derinamojo bangos ilgio lazerinius impulsus. Pirmą kartą buvo ištirti naujų netiesinėje optikoje perspektyvių LiInS2 ir LiInSe2 kristalų sklaidos nuostoliai infraraudonojoje srityje. Taip pat parodyta, kad koherentinės sklaidos tomografijos metodas, anksčiau taikytas puslaidininkinių kristalų tūriniams defektams tirti, yra tinkamas ir netiesinėje optikoje naudojamų kristalų kokybės tyrimams.

Submitted by Alison Vanceto (alison-vanceto@hotmail.com) on 2017-06-08T17:59:02Z No. of bitstreams: 1 DissTMG.pdf: 5915699 bytes, checksum: 6ec0af39899ad70e102eda93fa21e0e0 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-06-14T13:47:59Z (GMT) No. of bitstreams: 1 DissTMG.pdf: 5915699 bytes, checksum: 6ec0af39899ad70e102eda93fa21e0e0 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-06-14T13:48:05Z (GMT) No. of bitstreams: 1 DissTMG.pdf: 5915699 bytes, checksum: 6ec0af39899ad70e102eda93fa21e0e0 (MD5) / Made available in DSpace on 2017-06-14T13:55:25Z (GMT). No. of bitstreams: 1 DissTMG.pdf: 5915699 bytes, checksum: 6ec0af39899ad70e102eda93fa21e0e0 (MD5) Previous issue date: 2015-02-27 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / The morphology of extruded multiphase polymer systems is usually assessed through off-line characterization methods such as microscopy, which require much time for sample preparation and analysis of the results. This work aimed to the improvement of an optical detector to measure in real time the morphology of blends and polymeric composites in processing by extrusion, by laser light scattering at low angle (LALLS). Such equipment includes hardware and software and is based on measuring the intensity of light from a laser and is spread across and under the melt flow. The signals are collected by an array 91 of photodetectors sent to a computer, and displayed in real time on a three- dimensional plot of scattered light intensity to form a surface defined by 321 points. When analyzing the scattering profile valuable information can be determined that help to elucidate the morphology of the second phase particles. The LALLS detector was tested on bench using standard samples, which were prepared so that one of its parameters (orientation, second phase concentration, dispersed particle size or type of dispersed particle) were known. This allowed the systematic study of these samples and the detector device validation. Finally, the device was tested in real time on the extrusion process, and under different materials and operating conditions. Thus, the LALLS detector device created by the group was improved making it possible to evaluate in a practical way and in real time polymer blends in solid films and morphology of some blends and polymeric composites during extrusion. / A morfologia de sistemas poliméricos polifásicos é usualmente avaliada através de métodos de caracterização off-line, tal como a microscopia, os quais demandam muito tempo para a preparação das amostras e para a análise dos resultados. Este trabalho teve como principal objetivo o aperfeiçoamento de um detector óptico para medida em tempo real da morfologia de misturas e compostos poliméricos no processamento por extrusão, através do espalhamento de luz laser em baixo ângulo (LALLS). Tal equipamento inclui hardware e software e baseia-se na medida da intensidade da luz que provém de um laser e que é espalhada através do material fundido e sob fluxo. Os sinais são coletados por um arranjo de 91 fotodetectores, enviados a um computador, e apresentados em tempo real num gráfico tridimensional da intensidade de luz espalhada formando uma superfície definida por 321 pontos. Ao se analisar o perfil de espalhamento tem-se valiosas informações que ajudam elucidar a morfologia das partículas de segunda fase presentes. O detector de LALLS foi testado em bancada com o uso de amostras-padrão, as quais foram elaboradas de maneira que um de seus parâmetros (orientação, concentração de segunda fase, tamanho de partícula dispersa ou tipo de partícula dispersa) tivesse sido alterado de forma conhecida. Isso permitiu o estudo sistematizado dessas amostras e a validação do dispositivo detector. Por fim, o dispositivo foi testado em tempo real no processo de extrusão, sob diferentes condições materiais e de operação. Com isso, o dispositivo detector de LALLS criado pelo grupo foi aperfeiçoado possibilitando avaliar-se de forma prática e em tempo real: a morfologia de misturas poliméricas na forma de filmes sólidos e algumas misturas e compostos poliméricos durante a extrusão.