No description available.

Thesis (M.A. Sc.)--University of Toronto, 2006. / Source: Masters Abstracts International, Volume: 45-03, page: 1546. Includes bibliographical references.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: acoustic agglomeration; smoke detector response; enhanced deposition; soot deposition. Includes bibliographical references (p. 146-147).

As a byproduct of incomplete combustion, soot attracts increasing attentions as extensive researches exploring serious health and environmental effects from soot particles. Soot emission reduction requires a comprehensive understanding of the mechanism for polycyclic aromatic hydrocarbons and of soot formation and aging processes. Therefore, advanced experimental techniques and numerical simulations have been conducted to investigate this procedure. In order to investigate the effects of dimethyl ether (DME) mixing on soot particle size distribution functions (PSDFs), DME was mixed in premixed ethylene/oxygen/argon at flames at the equivalence ratio of 2.0 with a range of mixing ratio from 0% to 30% of the total carbon fed. Two series of atmospheric pressure flames were tested in which cold gas velocity was varied to obtain different flame temperatures. The evolution of PSDFs along the centerline of the flame was determined by burner stabilized stagnation probe and scanning mobility particle sizer (SMPS) techniques, yielding the PSDFs for various separation distances above the burner surface. Meanwhile, the flame temperature profiles were carefully measured by a thermocouple and the comparison to that of simulated laminar premixed burner-stabilized stagnation flame was satisfactory. Additionally, to understand the chemical role of DME mixing in soot properties, characterization measurements were conducted on soot samples using thermo-gravimetric analysis (TGA) and elemental analysis (EA). Results of the evolution of PSDFs and soot volume fraction showed that adding DME into ethylene flame could reduce soot yield significantly. The addition of DME led to the decrease of both the soot nucleation rate and the particle mass growth rate. To explain the possible mechanism for the observation, numerical simulations were performed. Although DME addition resulted in the slight increase of methyl radicals from pyrolysis, the decrease in acetylene and propargyl radicals inhibited the production of polycyclic aromatic hydrocarbons. At the same time, the addition of DME gave rise to the increase of the flame temperatures, which favored the production of OH radicals. The incremental concentration of OH radicals promoted the oxidation rate of soot particles. Additionally, soot samples from flames with higher DME mixing ratios showed higher O/C, H/C mass ratios and thus better oxidation characteristics. In summary, the addition of DME reduces soot emission in two ways: on the one hand, it inhibits soot nucleation and mass/size growth, then the production of soot particles decreases; on the other hand, it promotes soot oxidation process by increasing the concentration of OH radicals and improving the oxidation behavior of the soot particles, then more particles are oxidized. Both of them are responsible for the reduction of soot emissions at the presence of DME.

Soot is a common byproduct of hydrocarbon based combustion systems. It poses a risk to human and environmental health, and can negatively or positively affect combustor performance. As a result, there is significant interest in understanding soot formation in order to better control it. More recently, the need to study soot formation in engine relevant conditions has become apparent. One engine relevant parameter that has had little focus is the ambient pressure. This body of work focuses on the formation of soot in elevated pressure environments, and a number of investigations are carried out with this purpose. Laminar coflow diffusion flames are used as steady, simple soot producers. First, a commonly studied flame configuration is further characterized. Coflow flames are frequently used for fundamental flame studies, particularly at elevated pressures. However, they are more susceptible to buoyancy induced instabilities at elevated pressures. The velocity of the coflow is known to have an effect on flame stability and soot formation, though these have not been characterized at elevated pressures. A series of flames are investigated covering a range of flowrates, pressures, and nozzle diameters. The stability limits of coflow flames in this range is investigated. Additionally, an alternative strategy for scaling these flames to elevated pressures is proposed. Finally, the effect of coflow rate on soot formation is evaluated. Identification of fundamental flames for coordinated research can facilitate our understanding of soot formation. The next study of this work focuses on adding soot concentration and particle size information to an existing fundamental flame dataset for the purpose of numerical model validation. Soot volume fraction and average particle diameters are successfully measured in nitrogen-diluted ethylene-air laminar coflow flames at pressures of 4, 8, 12, and 16 atm. An increase in particle size with pressure is found up to 12 atm, where particle sizes plateau. Particle size in the annulus is more sensitive to pressure. Next, the development of an alternative particle size measuring technique is studied. Time Resolved Laser Induced Incandescence (TiRe-LII) is a commonly used technique to measure soot concentrations and particle size at atmospheric pressure. However, Laser Induced Incandescence (LII) models suffer from an incomplete understanding of the effects of elevated pressures on the absorption, annealing, and cooling of soot. The present study focuses on what affect the laser temporal pulse shape and duration may have on particle sizing. TiRe-LII in flames at 1 and 15 bar is carried out, using laser pulses with tophat or Gaussian temporal profiles of varying duration. Mono-disperse equivalent primary particle diameters are calculated using the KAUST LII model. Little difference in particle sizing is found for different laser pulses. However, this data will be useful for validating the KAUST LII model when absorption and poly-dispersion are accounted for. In an effort to move one step closer to logistical fuel studies, the sooting tendencies of a number of liquid fuels are studied at pressures up to 10. Of parallel relevance, a sooting index for surrogate development is evaluated for elevated pressure applications. The Yield Sooting Index (YSI) methodology is applied to 11 normal, cyclic, and branched alkanes. When referencing to two n-alkane fuels, the YSI of n-alkanes determined at atmospheric pressures accurately reflects the relative sooting tendencies of these fuels at elevated pressures. The relative sooting tendencies of cyclo- and methyl-alkanes have a lower pressure sensitivity than n-alkanes.

No description available.

New demands and tighter government legislations on greenhouse gases and pollutants, especially for those produced by diesel engines, there has been much focus on developing more efficient diesel engine designs and pollution control devices. There are several pollution control devices currently being implemented in diesel engines such as, diesel particulate filters, selective reduction catalyst, electrostatic filters, exhaust gas recirculation systems, etc. Diesel particulate matter is of particular importance especially when deposited because of its corrosive and thermal insulating nature. There are many complex mechanisms involved in fine particle deposition. This study will focus on the main deposition mechanisms such as convection, diffusion, thermophoresis and electric field effects. The objective of this study was to evaluate experimentally the mechanisms of diesel soot deposition in a rectangular (RWCS) and cylindrical (CWCS) wall cooled sections to evaluate thermophoretic effects. In additional, the coaxial cylindrical wall cooled section with additional with coaxial wire electrode was used to study applied electric field effect (CCWCSE) on soot deposition. A non-destructive Real-Time Neutron Radiography technique was used to evaluate the soot deposition thickness profiles inside the cooled sections. The experiments were conducted using diesel engine exhaust from a single cylinder diesel engine operated at fixed 2.4kW, at a exhaust gas mass flow rate of 20 kg/hr with exposure times ranging 0 to 3hrs, coolant temperatures from 20 to 40°C and exhaust gas temperatures from 250 and 270°C. The resulting Reynolds Number based on the mass flow rate per cross-sectional area times the hydraulic diameter was 6300 for the RWCS and 9000 for the CWCS and CCWCSE. The results show that for the RWCS, the soot deposition pattern qualitatively matched the cooling water channel outer wall surface temperature profile along with thicker deposition at the entrance region due to convection effects. For the ewes, the deposition was more uniformly distributed throughout the device. It was observed for both devices that as the mean soot deposition thickness increases with increasing exhaust gas exposure time and decreasing wall cooling temperature. Finally the experimental results for the CCWCSE shows that the soot deposition was enhanced by a positive or negative applied electric field. / Thesis / Master of Applied Science (MASc)

This study is dedicated to investigation of soot formed during combustion in diesel engine. Measurements were performed in a high speed direct injection optical diesel engine. Initially soot particle size, size distribution and soot volume fraction were investigated using time resolved laser induced incandescence (TR-LII) technique. For this study standard diesel fuel was used and measurements were performed for various injection timing and two different engine loads. Investigation showed that TR-LII is a powerful tool that can be used for characterization of in-cylinder soot in the engines. Subsequently TR-LII technique was developed to measure in-cylinder soot in two dimensional plane (planar laser induced incandescence PLII) and technique was combined with high speed imaging to investigate soot processes for ultra-low sulfur diesel (ULSD) and bio-fuel (RME). Two injection strategies of single and double injection were applied during these measurements. A high speed imaging technique was used to study the soot formation and oxidation during the combustion process within the cylinder and PLII was applied later in the stroke to study qualitatively the relative amount of un-oxidised soot that was left in the combustion chamber. In addition to PLII, TR-LII technique was used simultaneously to explore crank angle resolved variation of primary soot particle size and their size distribution during the expansion stroke. The same measurements were repeated for fuels with different composition investigating the relationship between the fuel properties and soot emission. Finally mathematical model for soot particle size and distribution width was modified by introducing assumption of multi-lognormal in-cylinder soot particle size distribution.

Abstract: Soot from combustion emissions has a negative impact on human health and the environment. Understanding and controlling soot formation is desirable to reduce this negative impact, especially as energy demands continue to increase. In this work, a range of fundamental combustion experiments are performed to better understand the soot formation process, and to develop diagnostics for measuring soot properties. First, studies on the effects of doping the flame with different polycyclic aromatic hydrocarbons (PAHs) was performed to investigate soot nucleation mechanisms. Soot formation was found to be most sensitive to phenylacetylene addition and nucleation through physical dimerization appears to be unlikely. Next, the effects of ammonia addition, a possible future fuel, on soot formation in laminar nonpremixed ethylene counterflow flames was performed. A reduction in soot volume fraction was observed and attributed to chemical effects of ammonia addition. Second, the investigation and development of several types of diagnostics was performed. Soot is typically reported to scale with pressure as Pn where P is pressure and n is a scaling factor. A wide range of scaling factors for ethylene coflow flames have been reported using different types of diagnostics. In this work, a comparison between a light extinction technique and PLII was performed and differences between reported values was explored. Next, the time resolved laser induced incandescence (TiRe-LII) diagnostic was advanced by exploring the effects of SVF on local gas heating. Errors introduced into this model by neglecting local gas heating are explored. Finally, a new diagnostic was developed for 3 dimensional measurements of SVF and velocity in turbulent flames using a technique known as diffuse-backlight illumination extinction imaging. Third, the application of gated 2D TiRe-LII was assessed in pressurized environments on laminar coflow flames. Comparisons between TiRe-LII and thermophoretically captured soot imaged by transmission electron microscopy (TEM) was performed. TiRe-LII was found to have reasonable agreement with TEM measurements if the SNR was high, but due to the large disparity in primary particle size in pressurized environments errors in 2D TiRe-LII can be significant.

En las últimas décadas, la investigación en motores de combustión ha estado enfocada fundamentalmente en la reducción de las emisiones contaminantes y la eficiencia de los mismos. Estos hechos junto con un aumento de la concienciación sobre el cambio climático han llevado a un aumento en la importancia de la eficiencia térmica respecto a otros criterios en el diseño de motores de combustión interna (MCIA). Para alcanzar este objetivo, existen diferentes estrategias a aplicar. En concreto, la transferencia de calor a las paredes de la cámara de combustión puede ser considerada como una de las principales fuentes de disminución de la eficiencia indicada. En particular, en los modernos motores diésel de inyección directa, la emisión de radiación de las partículas de hollín puede constituir un componente importante de las pérdidas de eficiencia. En este contexto se enmarca el objetivo principal de la tesis: contribuir a la comprensión de la transferencia de calor por radiación en la combustión diésel de inyección directa junto con la mejora del conocimiento en el proceso de formación-oxidación de hollín. El trabajo se ha basado tanto en resultados experimentales mediante la aplicación de técnicas ópticas en diversas tipologías de motor como en resultados simulados a partir de modelos unidimensionales validados. En la primera parte de resultados experimentales, se ha evaluado la cantidad de energía por radiación respecto a la energía química del combustible mediante la aplicación de una sonda optoelectrónica (basada en la técnica del 2-Colores) tanto en un motor óptico DI como en motor poli-cilíndrico DI de producción. En este estudio se han obtenido valores de intensidad espectral emitida por el hollín y posteriormente, la radiación total emitida por las partículas de hollín en todo el espectro. Como se ha citado anteriormente, las partículas de hollín son las principales responsables de la transferencia de calor por radiación, además de uno de los principales agentes contaminantes emitidos por los motores diésel. Las emisiones de hollín son el resultado de dos procesos antagonistas: la formación y oxidación del hollín. Los mecanismos de formación de hollín se discuten extensamente en la literatura. Sin embargo, existen deficiencias en cuanto al conocimiento de la oxidación de hollín. Por lo tanto, el objetivo de esta sección ha sido evaluar el impacto del proceso de mezcla y la temperatura del gas sobre el proceso de oxidación de hollín durante la última parte de la combustión bajo condiciones reales de operación. Finalmente, y en base a los resultados y conocimientos adquiridos hasta el momento, se ha desarrollado un modelo capaz de predecir las pérdidas de calor por radiación para un chorro diésel. El modelo está basado en tres sub-modelos: modelo de chorro, el cual analiza y caracteriza la estructura interna del chorro en términos de mezcla y combustión en un proceso de inyección con resolución temporal y espacial. Un modelo de hollín, en el que los resultados se justifican en función de procesos de formación y oxidación del hollín. La cohesión de estos dos sub-modelos se utiliza para obtener los valores de entrada al modelo de radiación, con el que se obtiene los valores de transferencia de calor por radiación para una llama diésel. / En els últims anys, la recerca en motors de combustió ha estat focalitzada principalment en la reducció de les emissions contaminants i la millora de la eficiència. Aquests fets afegits al fet del augment de la conscienciació del canvi climàtic han impulsat el interés per incrementar la eficiència tèrmica per damunt de altres criteris en el disseny de motors de combustió interna alternatius (MCIA). Per aconseguir aquest objectiu, existixen diferents estratègies a aplicar. Concretament, la transferència de calor a les parets de la càmera de combustió pot ser considerada un dels principals focs de reducció de eficiència indicada. En particular, en els moderns motors dièsel de injecció directa, la emissió de radiació de les partícules de sutja pot constituir un component important de les pèrdues de eficiència. En aquest context s'emmarca el objectiu principal de la tesis: contribuir a la comprensió de la transferència de calor per radiació en la combustió dièsel de injecció directa i la millora del coneixement del procés de formació-oxidació de la sutja. El treball esta basat tant en resultats experimentals mediant l'aplicació de tècniques òptiques en diverses tipologies de motor com en resultants simulats a partir de models unidimensionals validats. En la primera part dels resultats experimentals, s'ha avaluat la quantitat de energia per radiació respecte a la energia química del combustible mediant la aplicació de una sonda optoelectrònica (basada en la tècnica del 2-Colors) tant en un motor òptic DI com en un motor poli-cilíndric DI de producció en serie. En aquest estudi s'han obtingut valors de intensitat espectral emesa per la sutja i posteriorment, la radiació total emesa per les partícules de sutja en tot el espectre. Com s'ha citat amb anterioritat, les partícules de sutja son les principals responsables de la transferència de calor per radiació, a més de un del principals agents contaminants emès per els motors dièsel. Les emissions de sutja son el resultat de dos processos antagonistes: la formació i la oxidació de sutja. Els mecanismes de formació de sutja es discuteixen àmpliament en la literatura. No obstant això, existeixen deficiències pel que fa al coneixement de l'oxidació de sutja. Per tant, l'objectiu d'aquesta secció ha sigut avaluar l'impacte del procés de mescla i la temperatura del gas sobre el procés d'oxidació de sutja durant l'última part de la combustió sota condicions reals d'operació. Finalment, i en base als resultats i coneixements adquirits fins aquest moment, s'ha desenvolupat un model que permet predir les perdudes de calor però radiació per a un raig dièsel. El model esta basat en tres sub-models: model de raig, el qual analitza i caracteritza la estructura interna del raig en termes de mescla i combustió en un procés de injecció amb resolució temporal i espacial. Un model de sutja, en el qual els resultats es justifiquen en funció del procés de formació i oxidació de la sutja. La cohesió d'aquests dos sub-models s'utilitza per obtindre els valors d'entrada al model de radiació, amb el que s'obté els valors de transferència de calor per radiació per a una flama dièsel. / In the last two decades engine research has been mainly focused on reducing pollutant emissions and increasing efficiency. These facts together with growing awareness about the impacts of climate change are leading to an increase in the importance of thermal efficiency over other criteria in the design of internal combustion engines (ICE). To achieve the objective, there are different strategies to apply. The heat transfer to the combustion chamber walls can be considered as one of the main sources of indicated efficiency diminution. In particular, in modern direct-injection diesel engines, the radiation emission from soot particles can constitute a significant component of the efficiency losses. In this context, the main objective of the thesis is framed: to contribute to the understanding of the radiation heat transfer in DI diesel combustion together with the improvement of the knowledge in the soot formation-oxidation processes. The work has been based on experimental results through the optical technique application in different types of engine and on simulated results from validated one-dimensional models. In the first part of experimental results, the amount of energy lost to soot radiation relative to the input fuel chemical energy has been evaluated by means of the optoelectronic probe application (based on the 2-Color technique) in both an optical engine DI and a production 4-cylinder DI engine. In this study, the values of soot spectral intensity emitted have been obtained and later, the total radiation emitted by the soot particles in the whole spectrum. As mentioned above, soot particles are the main responsible for the radiation heat transfer, in addition to one of the important concern in meeting emissions regulations. Soot emissions are the result of two competing processes: soot formation and soot oxidation. Mechanisms of soot formation are discussed extensively in the literature. However, there are deficiencies in the knowledge of soot oxidation. Therefore, the objective of this section has been to evaluate the impact of mixing process and bulk gas temperature on late-cycle soot oxidation process under real operating conditions. Finally, based on the results and knowledge acquired, a model able to predict heat losses by radiation for a spray diesel has been developed. The model is based on three sub-models: spray model, which analyzes and characterizes the internal spray structure in terms of mixing and combustion process with temporal and spatial resolution. A soot model, in which the results have been justified according to soot formation and oxidation processes. The link of these two sub-models has been used to obtain the input values to the radiation model, which the radiation heat transfer values for a diesel flame are obtained. / Villalta Lara, D. (2018). RADIATION HEAT TRANSFER IN DIRECT-INJECTION DIESEL ENGINES [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/114793 / TESIS