Dissertations / Theses on the topic 'Dual fuel mode'

[ES] Históricamente, el sector del transporte de servicio mediano y pesado ha sido desafiado por las regulaciones de emisiones que se han impuesto a lo largo de los años, lo que requirió intensificar el esfuerzo de investigación con el objetivo de avanzar en el desarrollo tecnológico para ofrecer una opción que cumpla con las normas a un precio similar para el propietario. No obstante, la reciente introducción de la normativa EUVI ha requerido la adición de un complejo sistema de postratamiento, agregando nuevos costes fijos al producto, así como costes operativos con el consumo de urea. Este avance fue necesario debido a la limitación de la combustión diésel convencional que no puede desacoplar las altas emisiones de NOx y la eficiencia. Esta limitación tecnológica ha impulsado la investigación sobre diferentes conceptos de combustión que podrían mantener niveles de eficiencia similares a los de la combustión diésel controlando la formación de emisiones durante el proceso de combustión. Entre las diferentes soluciones que han ido apareciendo a lo largo de los años, se demostró que la Ignición por Compresión Controlada por Reactividad (RCCI por sus siglas en inglés) tiene una ventaja competitiva debido a su mejor controlabilidad, alta eficiencia y bajas emisiones de hollín y NOx. A pesar de sus beneficios, la extensión de RCCI a la operación de mapa completo ha indicado limitaciones importantes como gradientes de presión excesivos a alta carga, o alta inestabilidad de combustión y productos no quemados a baja carga del motor. Recientemente, se introdujo el concepto de combustión Dual-Mode Dual-Fuel (DMDF) como un intento de resolver los inconvenientes de la combustión RCCI manteniendo sus ventajas. Los resultados preliminares obtenidos en un motor mono cilíndrico (SCE por sus siglas en inglés) han demostrado que el DMDF puede alcanzar niveles de eficiencia similares a los de la combustión diésel convencional al mismo tiempo que favorece niveles ultra bajos de hollín y NOx. Si bien, los requisitos de la condición límite son difíciles de encajar en el rango operativo de sistema de gestión de aire, así como inconvenientes como el exceso de HC y CO que aún persiste en la zona de baja y media carga, lo que puede ser un desafío para el sistema de postratamiento. Además, las futuras regulaciones a corto plazo exigirán una reducción del 15 % de las emisiones de CO2 en 2025, reto que la literatura sugiere que no se logrará fácilmente solo mediante la optimización del proceso de combustión. En este sentido, esta tesis tiene como objetivo general la implementación del concepto de combustión DMDF en un motor multicilindro (MCE por sus siglas en inglés) bajo las restricciones de las aplicaciones reales para realizar una combustión limpia y eficiente en el mapa completo a la vez que brinda alternativas para reducir la concentración de HC y CO y lograr un ahorro de CO2. Este objetivo se logra mediante un primer extenso procedimiento de calibración experimental que tiene como objetivo trasladar las pautas de la combustión DMDF del SCE al MCE respetando los límites operativos del hardware original, evaluando su impacto en los resultados de combustión, rendimiento y emisiones en condiciones estacionarias y condiciones de ciclo de conducción. A continuación, se realizan estudios específicos para abordar el problema relacionado con la concentración excesiva de productos no quemados mediante investigaciones experimentales y simulaciones numéricas para comprender las consecuencias del uso de combustibles con diferente reactividad en la eficiencia de conversión del catalizador de oxidación original y su capacidad para lograr emisiones en el escape menores que el límite EUVI. Finalmente, se busca la reducción de CO2 a través de la modificación del combustible, investigando tanto la mejora del proceso de combustión como el equilibrio entre el ciclo de vida del combustible.<br>[CA] Històricament, el sector del transport de servei mitjà i pesat ha sigut desafiat per les regulacions d'emissions que s'han imposat al llarg dels anys, la qual cosa va requerir intensificar l'esforç d'investigació amb l'objectiu d'avançar en el desenvolupament tecnològic per a oferir una opció que complisca amb les normes a un preu similar per al propietari. No obstant això, la recent introducció de la normativa EUVI ha requerit l'addició d'un complex sistema de postractament, agregant nous costos fixos al producte, així com costos operatius amb el consum d'urea. Aquest avanç va ser necessari a causa de la limitació de la combustió dièsel convencional que no pot desacoblar les altes emissions de NOx i l'eficiència. Aquesta limitació tecnològica ha impulsat la investigació sobre diferents conceptes de combustió que podrien mantindre nivells d'eficiència similars als de la combustió dièsel controlant la formació d'emissions durant el procés de combustió. Entre les diferents solucions que han anat apareixent al llarg dels anys, es va demostrar que la Ignició per Compressió Controlada per Reactivitat (RCCI per les seues sigles en anglés) té un avantatge competitiu a causa de la seua millor controlabilitat, alta eficiència i baixes emissions de sutge i NOx. Malgrat els seus beneficis, l'extensió del RCCI a l'operació de mapa complet ha indicat limitacions importants com a gradients de pressió excessius a alta càrrega, o alta inestabilitat de combustió i productes no cremats a baixa càrrega del motor. Recentment, es va introduir el concepte de combustió Dual-Mode Dual-Fuel (DMDF) com un intent de resoldre els inconvenients de la combustió RCCI mantenint els seus avantatges. Els resultats preliminars obtinguts en un motor mono-cilíndric (SCE per les seues sigles en anglés) han demostrat que el DMDF pot aconseguir nivells d'eficiència similars als de la combustió dièsel convencional al mateix temps que afavoreix nivells ultra baixos de sutge i NOx. Si bé, els requisits de la condició límit són difícils d'encaixar en el rang operatiu de sistema de gestió d'aire, així com inconvenients com l'excés de HC i CO que encara persisteix en la zona de baixa i mitja càrrega, la qual cosa pot ser un desafiament per al sistema de postractament. A més, les futures regulacions a curt termini exigiran una reducció del 15% de les emissions de CO¿ en 2025, repte que la literatura suggereix que no s'aconseguirà fàcilment només mitjançant l'optimització del procés de combustió. En aquest sentit, aquesta tesi té com a objectiu general la implementació del concepte de combustió DMDF en un motor multi-cilindre (MCE per les seues sigles en anglés) sota les restriccions de les aplicacions reals per a realitzar una combustió neta i eficient en el mapa complet alhora que brinda alternatives per a reduir la concentració de HC i CO i aconseguir un estalvi de CO¿. Aquest objectiu s'aconsegueix mitjançant un primer extens procediment de calibratge experimental que té com a objectiu traslladar les pautes de la combustió DMDF del SCE al MCE respectant els límits operatius del motor original, avaluant el seu impacte en els resultats de combustió, rendiment i emissions en condicions estacionàries i condicions de cicle de conducció. A continuació, es realitzen estudis específics per a abordar el problema relacionat amb la concentració excessiva de productes no cremats mitjançant investigacions experimentals i simulacions numèriques per a comprendre les conseqüències de l'ús de combustibles amb diferent reactivitat en l'eficiència de conversió del catalitzador d'oxidació original i la seua capacitat per a aconseguir emissions al tub d'escapament menors que el límit EUVI. Finalment, es busca la reducció de CO2 a través de la modificació del combustible, investigant tant la millora del procés de combustió com l'equilibri entre el cicle de vida del combustible.<br>[EN] The medium and heavy-duty transport sector was historically challenged by the emissions regulations that were imposed along the years, requiring to step up the research effort aiming at advancing the product development to deliver a normative compliant option at similar price to the owner. Nonetheless, the recent introduction of EUVI normative have required the addition of a complex aftertreatment system, adding new fixed costs to the product as well as operational costs with the urea consumption. This breakthrough was required due to the limitation of the conventional diesel combustion which cannot decouple high NOx emissions and efficiency. This technological limitation has boosted the investigation on different combustion concepts that could maintain similar efficiency levels than the diesel combustion while controlling the emission formation during the combustion process. Among the different solutions that have appeared along the years, Reactivity Controlled Compression Ignition (RCCI) was demonstrated to have a competitive edge due to its better controllability, high efficiency and low soot and NOx emissions. Despite the benefits, the extension of RCCI to full map operation has presented significant limitations, as excessive pressure gradients at high load and high combustion instability and unburned products at low engine load. Recently, Dual-Mode Dual-Fuel (DMDF) combustion concept was introduced as an attempt of solving the drawbacks of the RCCI combustion while maintaining its advantages. The preliminary results obtained in single cylinder engine (SCE) have evidenced that DMDF can achieves similar efficiency levels than those from conventional diesel combustion while promoting ultra-low levels of soot and NOx. Albeit, the boundary condition requirements are hard to fit in the operating range of commercial air management system as well as drawbacks like excessive HC and CO that still persists from low to medium load, which can be a challenge for the aftertreatment system. Moreover, short-term future regulations will demand a 15 % reduction of CO2 emissions in 2025 which was proven in the literature to not be easily achieved only by combustion process optimization. In this sense, this thesis has as general objective the implementation of the DMDF combustion concept in a multi-cylinder engine (MCE) under the restrictions of real applications to realize clean and efficient combustion in the complete map while providing alternatives to reduce the HC and CO concentration and accomplish CO2 savings. This objective is accomplished by means of a first extensive experimental calibration procedure aiming to translate the guidelines of the DMDF combustion from the SCE to the MCE while respecting the operating limits of the stock hardware, assessing its impacts on combustion, performance, and emission results under steady and driving cycle conditions. Next, dedicated studies are performed to address the issue related with the excessive concentration of unburned products by means of experimental investigations and numerical simulations, to understand the consequences of using fuels with different reactivity in the stock oxidation catalyst conversion efficiency and its ability in achieving EUVI tailpipe emissions. Finally, CO2 reduction is explored through fuel modification, investigating both combustion process improvement and well-to-wheel balance as paths to realize CO2 abatement.<br>This doctoral thesis has been partially supported by the Spanish Ministry of Science Innovation and Universities under the grant:"Ayudas para contratos predoctorales para la formación de doctores" (PRE2018-085043)<br>Lago Sari, R. (2021). Dual Mode Dual Fuel Combustion: Implementation on a Real Medium Duty Engine Platform [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/165366<br>TESIS

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>Este trabalho avaliou o comportamento de um motor do ciclo Diesel, operando no modo original (Diesel puro) e no modo bicombustível (Diesel / etanol), em dois modos de hidratação do álcool (70 e 93 graus INPM). A rotação foi mantida fixa em 1800 rpm. A finalidade foi estudar os parâmetros de desempenho do motor e analisar a liberação de calor pela combustão, como também, o calor trocado com as paredes. Avaliou-se como parâmetros de desempenho, o rendimento térmico, consumo específico de combustível e emissão de poluentes. A fase inicial do trabalho constou de ensaios experimentais realizados no conjunto motor / dinamômetro nos modos mencionados acima. O objetivo foi coletar a variação de pressão no interior do cilindro, consumo de combustível, emissão de gases, temperaturas em pontos estratégicos, entre outros. Em uma segunda etapa foi realizada uma análise dos parâmetros de desempenho e da liberação de calor. Para emissões de poluentes, observou-se uma diminuição de MP em altas taxas de substituição. No entanto, notou-se um aumento elevado de HC. Em baixas cargas e taxas de substituição elevadas houve redução de emissão de NOx. O rendimento térmico apresentou comportamentos similares em 70 e 93 graus INPM. Em altas cargas e altas taxas de substituição houve um sensível aumento do rendimento quando comparado ao modo original. O rendimento foi menor para baixas cargas com altas taxas de substituição, em relação ao modo original. O início da combustão no modo bicombustível foi antecipado em relação ao modo original, nas condições de altas cargas e máximas taxas de substituição. Isto foi devido à liberação de calor que ocorreu mais cedo no modo bicombustível. Ressalta-se que, nas mesmas condições, houve a ocorrência de um maior calor trocado com as paredes do cilindro, em ambos os modos de hidratação (70 – 93 graus INPM), quando comparado ao modo original.<br>This work aimed to evaluate a Diesel cycle engine operating in the original (only Diesel) and dual-fuel modes (Diesel / ethanol) in two levels of hydration of alcohol (70 and 93 degrees INPM). Speed was kept fixed at 1800 rpm. The purpose was to study the parameters of engine performance and analyze the heat release by combustion and heat exchanged to the cylinder’s walls. For parameters of performance, evaluation of thermal efficiency, specific fuel consumption and emissions were conducted. Initial activities consisted in trial tests on the engine / dynamometer in the two modes as mentioned above. The goal was to collect the variation of indicated cylinder pressure data, as well as fuel consumption, emissions and temperatures at strategic points. Secondly, performance parameters and heat release analysis was performed. For emissions, a decrease in PM was found at higher replacement rates; however, in the same condition a large increase in HC was obtained. At low loads and at higher replacement rates, NOx emissions were reduced. Thermal efficiency showed similar behavior at 70 and 93 degrees INPM. At high loads and at higher replacement rates a significant increase in thermal efficiency compared to the original mode and for low loads with higher replacement rates thermal efficiency was decreased. In high loads and at higher replacement rates conditions, the process of combustion occurred before in the dual fuel mode, due to earlier heat release compared to original mode (only Diesel). In the same conditions an increase of heat exchanged to the cylinder’s wall in both modes of hydration of alcohol (70 and 93 degrees INPM) compared to the original mode was obtained.

A significant part of the world economy depends on stationary or vehicular Diesel engines. Such engines are fed mainly by fossil fuels, among these, the standard diesel. The growing interest in renewable energy sources makes the use of ethanol in these engines a real technological demand. From the existing concepts to meet this goal the Diesel-Ethanol in the Dual-Fuel mode has demand for published experimental data. Such concept brings a greater degree of freedom, but implications in technological challenges. It works through a PFI (Port Fuel Injection) system to prepare a pre-mixture of air and ethanol in the intake port which is compressed in the combustion chamber and ignited by pilot injection of diesel. In this work a single cylinder research engine with 100% electronically controlled calibration was used. The engine control parameters were set to maximize diesel substitution rate by ethanol with a limited indicated efficiency loss. Comparisons were made among different working conditions. Initially, the flow structure in the combustion chamber was tested in both quiescent and high swirl modes. Compression ratios were adjusted at 3 different levels: 14:1, 16:1 and 17:1. Two injectors were tested, the first one with mass flow of 35 g/s and another of 45 g/s. Regarding pressure diesel injection, 4 levels were investigated namely 800, 1000, 1200 and 1400 bar. The experiments discussed in this work were able to achieve up to 65% of diesel energy substituted by hydrated ethanol energy with an indicated efficiency of 49%. In comparison with the diesel only running condition, the NOx emissions was improved by up to 60%. But the HC, CO and aldehydes emissions had a penalty, showing a trade-off that shall be further investigated with a final design engine in the beginning of product development process.

Elevada eficiencia térmica y mínimas emisiones contaminantes impuestas por las restrictivas normativas anticontaminación en motores alternativos representan el principal objetivos de los fabricantes de motores. La estrategia de combustión diésel convencional es ampliamente utilizada en el mundo gracias a su excelente economía en el consumo de carburante. Esta estrategia permite operar con mezclas pobres de combustible y aire proporcionando elevada eficiencia térmica. Además, este tipo de combustión puede ser aplicada desde motores tanto para vehículos ligeros como en motores marinos. Sin embargo, este proceso de combustión conlleva a la generación de elevadas emisiones de NOx y emisiones de partículas (comúnmente llamado hollín en los diésel), siendo imposible reducir ambos contaminantes de forma simultánea. Por tanto, los fabricantes han incorporado sistemas de post-tratamiento con el objetivo de cumplir con las normativas de emisiones, cuya intención es la de proveer emisiones más limpias y elevada eficiencia. Por el contrario, este tipo de sistemas para mitigar las emisiones contaminantes incrementan la complejidad del motor dado el complejo proceso llevado a cabo durante el post-tratamiento y una aumento en los costes tanto de producción como operativos a lo largo del ciclo de vida del motor. La comunidad científica continua desarrollando soluciones alternativas a la combustión diésel convencional manteniendo los beneficios de este proceso de combustión mientras que las emisiones son reducidas (principalmente NOx y hollín). La comunidad científica ha encontrado en las estrategias de combustión de baja temperatura un proceso de combustión capaz de proporcionar elevada eficiencia térmica y emisiones ultra bajas de NOx y humo. En este sentido, la revisión bibliográfica dice que estos tipos de combustión permiten la reducción simultánea de ambas emisiones, rompiendo así el tradicional "trade-off" existente en la combustión diésel convencional. Sobre todas las estrategias, la que muestra un potencial superior es la estrategia conocida como combustión dominada por la reactividad del combustible. Este proceso de combustión se caracteriza por emplear dos combustibles, siendo capaz de solucionar los principales problemas de las estrategias de baja temperatura tales como el fasado de la combustión. Sin embargo, esta estrategia de combustión también presenta algunos inconvenientes como el elevado nivel de monóxido de carbono e hidrocarburos inquemados a baja carga y elevado gradiente de presión y presión en cámara a elevada carga que limitan el rango de operación. El objetivo general de la presente investigación es proveer de una estrategia de combustión "dual-fuel" capaz de operar sobre todo el rango de operación de un motor proporcionando igual o mejores eficiencia térmica que el diésel convencional y emisiones ultra bajas de NOx y humos. Adicionalmente, esta investigación implica una exploración delas emisiones de las partículas del concepto de combustión ya que el número de partículas se encuentra actualmente regulado por la normativa anticontaminante. El proceso de combustión que responde a este objetivo es "Dual-Mode Dual-Fuel". Este concepto de combustión emplea dos combustibles y cambia de combustión premezclada a baja carga a combustión de naturaleza difusiva a plena carga. Con el deseo de explorar las capacidades de la estrategia de combustión, se han empleado dos configuraciones de "hardware" y se ha realizado un estudio de la distribución por tamaños de las partículas. Finalmente, considerando los principales resultados de la investigación, el último capítulo pretende resumir las principales bondades del concepto de combustión así como sus limitaciones y trabajos futuros.<br>Elevada eficiència tèrmica i mínimes emissions contaminants impostes per les normatives anticontaminants en motores alternatius representen el principal objectiu dels fabricants de motors. La estratègia de combustió diésel convencional es àmpliament utilitzada per tot el mon gracies al excel·lent consum de carburant. Esta estratègia permet operar el motor amb dosatges pobres que resulten en elevada eficiència tèrmica. A més, aquest tipus de combustió pot ser aplicada tant a els motor mes lleugers con als motor per aplicacions marines. No obstant això, aquest procés de combustió implica la generació de elevats nivells de emissió de NOx i sutja, que no es poden reduir simultàniament. Per tant, els fabricants han incorporat sistemes de post-tractament amb el objectiu de acomplir les normatives anticontaminació, que pretenen obtindre motors en emissions mes netes i mes eficients. Per el contrari, aquest tipus de sistemes per a reduir les emissions incrementen la complexitat del motor i els costos tant de producció com operatius al llarg del cicle de vida del motor. La comunitat científica continua desenvolupant solucions alternatives a la combustió dièsel mantenint els beneficis d¿aquest tipus de combustió però reduint les emissions (principalment NOx i sutja). La comunitat científica ha trobat a les estratègies de combustió de baixa temperatura un procés de combustió que te elevada eficiència tèrmica i extremadament baixes emissions de NOx y partícules. En aquest sentit, la revisió bibliogràfica constata que aquests tipus de combustions permeten la reducció simultània dels contaminants NOx i sutja, trencant el tradicional "trade-off" existent a la combustió dièsel. De entre totes les estratègies proposades de baixa temperatura, la estratègia combustió dominada per la reactivitat del combustible presenta mes potencial que les altres. Aquest procés de combustió es caracteritza per utilitzar dos combustibles, lo que li permet solventar els principals problemes que han aparegut al llarg de la investigació de les estratègies de baixa temperatura com el control de la combustió. No obstant, aquest concepte de combustió també presenta algunes limitacions com el excessiu nivell de monòxid de carbó e inquemats a baixa càrrega i el elevat gradient de pressió i elevada pressió en càmera a elevada càrrega que limiten el rang de operació del motor. El objectiu de la investigació es proposar un concepte de combustió "dual-fuel" que puga operar en tot el rang de operació de un motor proporcionant el mateix o millorant la eficiència tèrmica que el dièsel amb emissions ultra baixes de NOx y partícules. A més, aquesta investigació també implica realitzar una exploració de les partícules emitides per el concepte ja que actualment està regulat per les normatives anticontaminants. El procés de combustió que compleix el objectiu es diu "Dual-Mode Dual-Fuel". Aquest concepte de combustió utilitza dos combustibles de diferent reactivitat y modifica la combustió de totalment premesclada a baixa càrrega a combustió de natura difusiva a plena càrrega. Amb el desig de explorar les capacitats del concepte, s¿han arribat a provar dos configuracions de pistons diferent per a adequar la relació de compressió i també un anàlisi per tamanys de les partícules. Finalment, considerant els principals resultats obtinguts, el últim capítol pretén resumir les principals avantatges del concepte ací com les principals limitacions y , per tant, els treballs futurs.<br>High thermal efficiency coupled to minimum pollutants emissions imposed by the stringent standard emissions limitations in reciprocating engines represent the main target of the engine manufacturers industry. Conventional diesel combustion strategy is widely used worldwide due to its excellent fuel economy. This combustion strategy allows operating under lean mixtures of fuel and air that provide high thermal efficiency. In addition, this type of combustion can be applied from light-duty engines to large bore marine engines. However, the combustion process leads to high NOx and particle matter emissions, being impossible to reduce both pollutants simultaneously. Hence, manufactures have incorporated aftertreatment systems in order to meet the imposed standard emissions limitations, which are aimed to provide cleaner emissions and high efficiency. By contrast, these systems required for the emissions mitigation result in a very complex processes and an increase in the engine production and operational costs. The research community continues developing alternative solutions to the conventional diesel combustion concept keeping the benefits of this combustion process while the emissions are reduced (mainly focused on NOx and soot). Research community have found in the low temperature combustion strategies the combustion process able to provide excellent high thermal efficiency and ultra-low NOx and smoke emissions. In this sense, the literature review states that this types of combustion processes allow the simultaneous reduction of NOx and smoke, breaking the traditional trade-off found in diesel engines. Amongst others, the most promising strategy is the reactivity controlled compression ignition. This combustion process is characterized by using two fuels and is able to solve the main challenges of the low temperature combustion processes such as combustion phasing control. Nonetheless, the reactivity controlled strategy also presents some challenges such as excessive carbon monoxide and unburned hydrocarbons during low load operation and high pressure rise rate and in-cylinder pressure that limit the engine range operation. The general objective of this investigation is to provide a dual-fuel strategy able to operate over the whole range providing similar or better thermal efficiency that the conventional diesel combustion and ultra-low values of NOx and smoke. In addition, the investigation also explores the particle emissions of the concept since it is regulated by the standard emissions. The combustion process that responds to the target provided at the general objective is the Dual-Fuel Dual-Mode concept. This concept uses two fuels and switches from a dual-fuel fully premixed strategy (based on the RCCI concept) during low load operation to a diffusive nature during high load operation. In order to explore the capabilities of the concept, two hardware configurations are used and a particle size distribution exploration is performed. Finally, considering the main findings of the investigation, the last chapter is aimed to provide the benefits of the combustion process developed as well as the main limitations or future works of the concept.<br>Boronat Colomer, V. (2018). Dual-Fuel Dual-Mode combustion strategy to achieve high thermal efficiency, low NOx and smoke emissions in compression ignition engines [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/113413<br>TESIS

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>No presente trabalho, ensaios experimentais de um motor do ciclo Diesel consumindo etanol hidratado ou gás natural em substituição parcial ao óleo diesel, foram realizados. Os objetivos principais foram verificar as influências dos combustíveis alternativos e avaliar as técnicas do avanço da injeção do diesel e da restrição parcial do ar de admissão, em relação aos parâmetros característicos da combustão, desempenho e emissões. Com base nos dados do diagrama pressão-ângulo de virabrequim, foi possível analisar alguns parâmetros característicos da combustão, tais como o início da combustão, a máxima taxa de elevação de pressão e o pico de pressão. Os parâmetros do desempenho e emissões do motor foram analisados através do rendimento térmico e as concentrações de monóxido de carbono, hidrocarbonetos, material particulado e óxidos de nitrogênio. Os resultados obtidos mostraram que as técnicas avaliadas no modo bicombustível junto com as elevadas taxas de substituição do óleo diesel favoreceram a melhor queima dos combustíveis alternativos, refletindo-se favoravelmente em menores emissões de CO e MP, além de um pequeno aumento no rendimento térmico do motor. No entanto, houve também um acréscimo nas emissões de NOX e, no caso específico do avanço da injeção, foi notado um maior ruído gerado pelo motor.<br>In this report, experimental tests of a Diesel cycle engine running with hydrous ethanol or natural gas with partial substitution for diesel fuel were performed. The main objectives were to verify the influence of alternative fuels and evaluate the advancing of diesel injection timing and the air partial restriction, regarding the characteristic parameters of combustion, performance and emissions. Based on data from the pressure-crank angle diagram, it was possible to analyze some characteristic parameters of combustion, such as the start of combustion, the maximum rate of pressure rise and peak pressure. The parameters of the engine performance and emissions were analyzed through the thermal efficiency and the concentrations of carbon monoxide, hydrocarbons, particulate matter and nitrogen oxides. The results showed that the techniques evaluated in dual fuel mode with higher rates of substitution of diesel fuel favored a better burning of the alternative fuels, reflecting favorably in lower emissions of CO and PM, and also in a small increase in the engine thermal efficiency. However, there was also an increase in NOX emissions and, in the specific case of the advanced injection timing, it was noted a louder noise generated by the engine.

La dégradation de l’environnement ainsi que l’épuisement progressif des énergies fossiles devient très inquiétant et incite les états à définir des limites d’émission polluantes plus strictes. Ceci a conduit les constructeurs automobiles à poursuivre leurs recherches dans le développement de conception propre et efficace des moteurs en utilisant des combustibles alternatifs dans les moteurs à combustion interne.Dans le présent travail, on s’intéresse à l’étude des moteurs fonctionnant en mode DF afin d’améliorer ses performances tout en minimisant les émissions polluantes, en particulier les HC et les CO. Pour ce faire des études expérimentales ont été menées. Une réduction de 77% des émissions de HC a été observée en passant d’une richesse de 0,35 à 0,7. Par ailleurs, Il a été noté aussi qu’une diminution de 20% à 50% des émissions de CO avec une amélioration de 30% du rendement peut être visualisée en variant l’avance à l’injection de 4,5 °V à 6 °V. Concernant la mise en place de la pré-injection, une baisse de 30% des émissions de NOx a été observée avec un gain de 12% à 30% de rendement par rapport à une seule injection. En dernier terme, un modèle thermodynamique à une zone a été développé afin de prédire la température et la pression dans le cylindre. Une bonne concordance a été notée entre les deux résultats avec une erreur moyenne relative inférieure à 5%<br>Currently, the environmental degradation due to pollutant emissions and the gradual depletion of fossil fuels, becoming very worrying, are prompting European directives to set pollutant emission limits. These have led manufacturers to continue research in the development of clean and efficient engine designs using alternative fuels in internal combustion engines.In this work, we focus on the study of engines operating in dual-fuel mode to improve its performance while minimizing pollutant emissions, particularly HC and CO. For this, experimental studies were conducted. A reduction of about 77% in the HC emissions was observed as the equivalence ratio was varied from 0.35 to 0.7. Regarding the effect of injection timing, it was noted that the CO emissions decreased about 20% to 50% with an improvement in the brake thermal efficiency by 30% upon varying the injection advance from 4,5 °CA to 6 °CA. On the other hand, the introduction of pre-injection strategy led to a decrease by 30% in NOx emissions with an amelioration of brake thermal efficiency of 12% to 30% compared to a single injection. Lastly, a single zone thermodynamic model was developed to predict the in-cylinder temperature and pressure. A good agreement was noted between the predicted and experimental results. The average relative error was less than 5%

A new quasi-dimensional, multi-zone model has been developed to describe the combustion processes occurring inside a dual fuel engine. A dual fuel engine is a compression ignition engine in which a homogeneous lean premixed charge of gaseous fuel and air is ignited by a pilot fuel spray. The atomisation and preparation of the pilot leads to the formation of multiple ignition centres from which turbulent flame fronts develop. The energy release in a dual fuel engine is therefore a combination of that from the combustion of the pilot fuel spray and lean premixed charge. Hence, the dual fuel combustion process is complex, combining elements of both conventional spark and compression ignition engines. The dual fuel engine is beneficial as it can achieve significant reductions in emissions of carbon dioxide (CO2), as well as reducing emissions of oxides of nitrogen (NOx) and particulate matter (PM).

<p> Natural gas (NG)-diesel dual fuel engines have been highlighted for their fuel flexibility and high thermal efficiency comparable to diesel engines. However, the addition of NG to compression ignition diesel engines was reported to elongate ignition delay and to increase the emissions of carbon monoxide (CO), unburned methane (CH₄), and nitrogen dioxide (NO₂). Past research on dual fuel engines has focused on the experimental research on the engine performance, combustion process, and exhaust emissions. The research on detailed mechanism dominating the impact of CH₄ on formation of CO and NO₂ in cylinder, and the mechanism for CH₄ to survive the combustion process and slip through the cylinder is limited. The examinations of these mechanisms require the simulation of dual fuel engine combustion using a CFD model coupled with chemical kinetic mechanism. </p><p> This research numerically investigates the combustion process and exhaust emissions from two NG-diesel dual fuel engines using a CFD model coupled with a reduced primary reference fuel (PRF) chemistry. The CFD model used is Converge-SAGE model with a maximum of 300000 grid points. The fuel chemistry used is a reduced PRF mechanism with 45 species and 142 reactions including a reduced NOx mechanism with 4 species and 12 reactions. The CFD model with reduced PRF chemistry has been validated against experimental data measured in a single-cylinder compression-ignition engine over a wide range of CH₄ substitution ratio. A post-processing tool has been developed to calculate, analyze, and visualize the instantaneous rate of production (ROP) of key species in each cell with the known temperature, pressure, and species concentration exported by CFD code. The simulation results are further post-processed to numerically investigate the combustion process and the formation mechanism of CO, and NO₂ in a dual fuel engine. The mechanism for CH₄ to survive the main combustion process and post-combustion oxidation process is numerically examined. </p><p> The research on NO₂ formation identified NO+HO₂&rarr;NO₂+OH as the key reaction dominating the increased formation of NO₂ in dual fuel engines. The HO₂ necessary for the formation of NO₂ emitted by the engine is produced through the post-oxidation of CH₄ that survived the main combustion process. The CO emitted from the NG-diesel dual fuel engine is formed through the oxidation of CH₄ during the late combustion process and post-combustion CH₄ oxidation. The CH₄ that survived the main combustion and post-combustion oxidation process is mainly distributed in region far from the spray plume of the pilot fuel and its combustion products. </p><p> This research also examined approaches capable of significantly reducing the emissions of CH₄ from a dual fuel engine. The preliminary results concluded that CH₄ emissions can be significantly reduced through optimizing injection timing, and the application of two-pulse fuel injection strategy. Adjusting injector fuel spray angle can also significantly reduce CH₄ emissions which should be considered in developing dedicated dual fuel engine.</p><p>

A major limitation of acousto-optic (AO) leaky-mode modulator based holographic displays is their inability to present full-parallax. We propose that full-parallax capabilities can be bestowed on these displays by integrating an electro-optic (EO) phased array into the architecture. We validated this concept by rendering computational models and by fabricating and testing a basic two-axis AO/EO deflector prototype in lithium niobate. This was, to our knowledge, the first instantiation of an integrated, hybrid AO/EO deflector. The prototype had a 6° deflection range along the AO-axis, and a 3° deflection range along the EO-axis. A series of models provide us with a clear path forward for optimizing this deflector. They suggest that an AO/EO modulator with an EO deflection range of 24.5° and that requires less than 7.5 V can be fabricated within the limitations of standard photolithography.

Dual-phase (DP) steels consisting of a ferrite matrix with dispersed martensite particles have attracted a significant interest due to their combination of high work hardening and ductility. A great deal of experimental work has been done to obtain a better comprehension of the relation of their mechanical behaviour to their microstructural characteristics. In the present work, a micromechanical study of ferrite-martensite DP steels is conducted. The deformation of ferrite is described by a rate-dependent crystal plasticity theory, which relates the stress-strain field equations on the grain level to the macroscopic behaviour of the material. The crystal plasticity theory assumes that slip is the only deformation mechanism. Martensite, on the other hand, is considered an elastic-plastic isotropic solid. The interfaces of the grains are taken into account through an idealized form of grain boundaries. A FORTRAN program was coupled with the finite element method to solve the stress equations of the crystal plasticity. Including the grain boundaries made it possible to examine the effect of ferrite grain size on the strength of the material. It is shown that by decreasing the grain size, the yield stress increases according to Hall-Petch equation. Additionally, the effects of the volume fraction of martensite (Vm) on the onset strain, i.e. the strain at which martensite deforms plastically, and of the distribution of martensite on the stress are studied. The former showed that the onset strain of the DP steel declines linearly with increasing Vm up to 36%, beyond which the onset strain becomes independent of V m. The latter revealed that when martensite particles are formed as islands in the ferrite grains, the material exhibits higher strength and hardening rate; compared to when martensite is distributed as large blocks among the ferrite grains.

The purpose of this research is to further investigate the ongoing debate between the Dual Mechanism Model and the Connectionist Model of language processing by investigating how knowledge of second language (L2) inflectional morphology is represented and processed by learners of English. Specifically, do second language learners of English use the same Dual Mechanism Model that Prasada and Pinker (1993) have argued is a universally applicable model, or does the Connectionist Model of language processing better explain L2 learning and language processing?<br>The participants in this study were students in a Montreal area CEGEP. The instrument used to gather data was the Prasada and Pinker pseudo-verb list, with modifications suggested by Lee (1994) to create a revised list. Participants were asked to create past tense forms of pseudo verbs. In addition to this task, four participants were asked to do a simultaneous verbal think aloud, orally explaining their responses to the stimulus presented in the study.<br>The results of the studies indicate that English second language learners used both a rule based mechanism and an associative mechanism in the formation of both regular and irregular English verbs. This result provides support for the claims of the Connectionist model of past tense formation of English verbs, but also supports some of the claims of the Dual Mechanism Model. There are possible implications for the teaching and learning of English as a Second Language (ESL). This study also raises further research questions involving rule vs. associative learning in the teaching and learning of language. (Abstract shortened by UMI.)

U okviru istraživačkog rada formiran je matematički model za simulacijuprocesa transformacije energije u postrojenju gasne turbine prisagorevanju gasova srednje ili niže toplotne moći. Data je analiza procesakosagorevanja gasa iz gasifikacije kukuruznog oklaska i prirodnog gasa upostrojenju gasne turbine, za tri različite konfiguracije postrojenja.Analiza je rađena na primeru osnovnog Joule-ovog ciklusa sa vazduhomhlađenim lopaticama.<br>This paper presents mathematical model for simulation of energytransformation process in gas turbine facility with combustion of mediumand low calorific gases. The basis of the mathematical model is theM&uuml;ller&rsquo;s method. Analysis of co-firing the corn cob gas and natural gas fordifferent gas turbine facility configurations is presented. The basic Joulecycle with blade cooling was analyzed.

Pinker and Prince (1988, 1994) propose that there are two separate systems involved in linguistic representation and processing; one system is rule-governed, and incorporates symbolic hierarchical linguistic representations, the other is associative with linguistic information represented in a more distributed fashion. One particular linguistic feature of English said to exemplify the principles of this dual-mechanism model is inflectional morphology. Pinker and Prince (1988; 1994) present a range of evidence showing that native speakers of English process regular inflectional items in ways that are both quantitatively and qualitatively different from irregular inflectional items. This dual-mechanism model has been largely investigated within the context of first language (L1) learning, and has received considerable support from investigations using a number of different research paradigms. Nonetheless, there have been a number of serious criticisms in that the apparent behavioural distinctions between regular and irregular inflectional items can be supported by an alternative associative system (Elman, Bates, Johnson, Karmiloff-Smith, Parisi & Plunkett, 1996). The research presented in this dissertation investigates how knowledge of second language (L2) inflectional morphology might be processed and represented. The research is grounded within the theoretical framework provided by the dual-mechanism model and evaluates whether the claims and assumptions of this model are relevant to how L2 learners process, represent and learn about inflectional morphology. Three experiments are presented which address the issues of: compounding with regular and irregular noun plurals (Experiment 1); past tense generalization with regular and irregular verbs (Experiment 2); and finally, the development of knowledge of a new inflectional paradigm (Old English noun plurals, Experiment 3). Each of these experiments provides findings which are difficult for the dual-mechanism model

In this dissertation I explored how women and men global managers from the generation aged 30 to 45 in the United States and Canada called "Generation X", navigated global work and family demands while pursuing a global career. I conducted in-depth interviews with 25 Generation X global managers in dual-career families ("Global Gen Xers") to examine the scope and nature of global work and the importance of international travel and technology in pursuing alternative forms of global careers. I also investigated how working globally interweaves with family routines and how participants assessed their ability to manage work and family demands. Three configurations of global work emerged from the data based on an examination of the degree of Travel Salience and Global Scope in each Global Gen Xer's job. These configurations represent different patterns of international travel and technology employed to meet the demands of global work. To reconcile these global work demands with family demands, a Global Gen Xers' individual discretion over international travel played a key role in their global careers. Moreover, I uncovered strategies and tactics employed to effectively manage boundaries between global work and family when the Global Gen Xers were both traveling abroad and working in the domestic location. Finally, I explored the Global Gen Xers' conceptualizations of "work-life balance" and analyzed their personal assessments relative to their individual: 1) Global Work Configurations, 2) Travel Discretion and 3) Boundary Management Strategies. This study reveals a unique global work-family interface as involving navigation between periods of: physical or virtual "presence" coupled with 24-7 "availability", which is facilitated by workplace flexibility and the use of key information and communication technologies. The findings suggest that alternative forms of pursuing a global career can under certain conditions satisfy both organizational global work demands and individual desires for work-life balance. The dissertation contributes to knowledge on global careers, work-family issues and generational diversity.<br>Dans cette thèse, j'étudie comment des gestionnaires américains et canadiens de la génération des 30 à 45 ans, la génération X, gèrent les exigences d'une carrière mondiale conjointement aux exigences familiales. Lors d'entrevues avec 25 gestionnaires mondiaux de la génération X et de familles à double-carrière (ci-après, « Global Gen Xers »), j'examine la portée et la nature du travail ainsi que l'importance du voyage et de la technologie dans la poursuite des formes alternatives d'une carrière mondiale. J'examine les effets d'entreprendre une carrière mondiale sur le rythme de la famille et sur la signification, pour chacun, de l'équilibre travail-vie.Trois configurations de travail mondial (formées des combinaisons du voyage et de la technologie) émergent des données basées sur l'analyse du degré de « Travel Salience » et du « Global Scope » de l'emploi de chaque Global Gen Xer. Il apparait que le pouvoir discrétionnaire des Global Gen Xers quant à la prise des décisions relatives aux voyages étant donnés leurs besoins personnels et familiaux sont essentiels pour maintenir une carrière mondiale. De plus, je mets en évidence certaines stratégies et tactiques employées par les Global Gen Xers pour gérer la frontière entre le travail et la famille tant à l'étranger qu'à domicile. Finalement, j'expose les conceptualisations de « l'équilibre travail-vie » pour ces Global Gen Xers et j'analyse par conséquent leur évaluation personnelle de l'équilibre travail-vie par rapport à leurs 1) « Global Work Configurations », 2) « Travel Discretion » et 3) « Boundary Management Strategies ». Cette étude souligne les aspects internationaux de la conciliation travail-famille, un contexte dans lequel sont cruciales la navigation entre des périodes de « présence » physique ou virtuel ainsi qu'une « disponibilité » 24-7. Toutes deux doivent être soutenues par une flexibilité organisationnelle et l'implantation de certaines technologies d'information et communications essentielles. Les résultats suggèrent que des formes alternatives d'une carrière mondiale peuvent, sous certaines conditions, satisfaire les besoins de l'organisation mondiale et les désirs de l'individu pour une vie équilibrée. Ces résultats contribuent donc à la littérature portant sur les carrières mondiales, l'équilibre travail-famille, et la diversité générationnelle.

This thesis focuses on the development of new compounds or new processes that are more environmentally friendly and economical than those currently in use. The decomposition of hydrazine, a well established liquid rocket fuel for both the aerospace and defense industries, to the product ammonia is studied. Control of this reaction will allow hydrazine to be used as a propellant for both chemical and electric propulsion. From this a dual stage thruster will be developed that will be more efficient than current systems decreasing the amount of propellant needed and allowing for either a larger mission payload or a longer duration of individual missions. Hydrazine, while beneficial and well established, is also highly toxic, so other work in this thesis focuses on the synthesis of the novel molecule 1,1-dimethyl-2-[2-azidoethyl]hydrazine or DMAEH and its hydrazone intermediate 1,1-dimethyl-2-[2-azidoethyl]hydrazone or De-DMAEH as less toxic hydrazine replacements. Novel "switchable" ionic liquids have been investigated in this research. These are solvents that can change from molecular liquids to ionic liquids and back, simply with the addition or removal of CO₂ from the system. They can be used for a variety of applications, including as solvents for a reaction and separation system. Due to the recyclable nature of these solvents, waste is decreased making their development and implementation both environmentally and economically beneficial. Finally, the grafting reaction of vinyl silanes onto a hydrocarbon backbone is investigated. Fundamental work is being performed to study the graft distribution, selectivity and mechanism by which this reaction occurs. A more thorough understanding of how this reaction proceeds will allow for the development of a more efficient industrial process.

The present work studies the use of a two-zone computer model to simulate the operation of an internal combustion engine with spark ignition fueled with alcohol fuels and gasohol. To fit the model to the experimental data, a parameter estimation technique was used and the heat transfer correlation that could better fit the tested fuels and engine was determined. The tested fuels were: hydrous ethanol, wet ethanol (from 10% to 40% of water, by volume), n-butanol, n-butanol/ethanol blend and gasohol. In addition to the experimental tests with the engine, tests with a packed distillation column under batch process were made in order to determine the energy efficiency involved between production and use as a fuel for hydrous ethanol and wet ethanol fuels. The results showed that the two-zone model was able to predict satisfactorily the behavior of all tested fuels, accurately obtaining the engine performance parameters. In terms of energy efficiency, wet ethanol fuels have advantage over hydrous ethanol fuel, especially in the case of 30% of water by volume, where energy efficiency reaches its maximum value, considering the distillation and engine combustion processes. The n-butanol fuel was capable of act as a surrogate for both hydrous ethanol and gasohol with efficiency, leading the engine to have good performance in the tested operational conditions and appearing, due to this, as an interesting alternative of renewable fuel to be inserted in the Brazilian energy matrix.<br>O presente trabalho investiga o uso de um modelo computacional de duas zonas para simular o funcionamento de um motor de combustão interna com ignição por centelha abastecido com álcoois combustíveis e gasolina. Para o ajuste do modelo fez-se uso de técnica de estimação de parâmetros e determinação da correlação de transferência de calor capaz de melhor se ajustar aos combustíveis e ao motor testados. Os combustíveis utilizados foram: etanol hidratado, etanol super-hidratado (de 10% a 40% de água, em volume), n-butanol, misturas de n-butanol e etanol e gasolina e etanol. Além dos testes experimentais com motor, testes de bancada com uma coluna de destilação recheada em regime descontínuo foram realizados a fim de determinar a eficiência energética do processo de produção e queima de etanol hidratado e super-hidratado. Os resultados obtidos mostraram que o modelo de duas zonas é capaz de prever de maneira satisfatória o comportamento de todos os combustíveis testados, com determinação precisa de parâmetros de desempenho do motor. Em termos de eficiência energética, o etanol super-hidratado tem vantagem em relação ao etanol hidratado combustível, em especial quando com 30% de água em volume, onde a eficiência energética é máxima, considerados os processos de destilação e queima no motor. O n-butanol combustível usado mostrou-se capaz de substituir eficientemente tanto o etanol hidratado como a gasolina brasileira, levando o motor a ter boa performance nas condições operacionais testadas e aparecendo, dessa forma, como interessante alternativa de combustível renovável a ser inserida na matriz energética brasileira.

In the last years climate change has become an emergency that united countries of the world to make agreements to reduce pollutant emissions. In this context, the diesel engine, whose combustion is characterised by high emissions of particulate matter and nitric oxides, is likely to disappear from the future automotive market. However, the high performances of this well established engine may still represent a resource in terms of power, efficiency and reliability. In this regard, a possible solution is to readapt the engine to operate in Dual Fuel mode. In order to assess the benefits and limits of this technology, it is necessary a deep investigation of the phenomena that characterise the combustion development that results further complicated, due to the interaction of two burning fuels. To this purpose, Computational Fluid Dynamics is the most powerful tool allowing investigation of the different processes that take place inside the cylinder such as turbulence, fuel atomisation and chemical kinetics. Clearly, major difficulties are encountered in the choice of a combustion model suitable for both fuels. In this regard, kinetics plays a key role in the description of the oxidation process. This thesis aimed at a progressive improvement of the methodology and more detailed kinetic mechanism were utilised to better comprehend the actual combustion mechanism and pollutants formation. Starting from a simplified kinetics scheme for diesel oil and natural gas oxidation, firstly a new mechanism including 9 reactions was introduced for the ignition of methane (considered as the main component of natural gas), in this way it was possible to release from empirical correlations for the ignition of at least one of the two fuels. Finally, this model was compared with a more detailed scheme consisting of 100 species and 432 reactions. Further criticalities arise from the wide operating range of the engine, especially for automotive applications. To overcome the typical problem related to the computational cost of the CFD based approach, the utilisation of different tools such as a one-dimensional model demonstrated to be helpful for extending the numerical investigations to multiple cases characterised by either different load levels or changes in the fuel injection settings. In this framework the experimental activity represented an effective tool for the validation of the numerical outcomes, since experimental data provided important information on the behaviour of three distinct diesel engines, say: a light-duty common rail engine, an optically accessible research engine and a heavy-duty engine. The main point to be highlighted is that the study of three engines with different characteristics allowed a wide investigation on different operating conditions.

Industrial dependence on energy and international conflicts has triggered the fuel prices to new highs. As a result, new alternative fuels must be explored that have no or very less harmful emissions without the compromise of the efficiency. One such fuel that can be converted for use in internal combustion engines is biogas. In this experimental study, a Direct Injection Compression Ignition (DICI) engine is converted into a dual-fuel engine that runs on biogas as primary fuel and various fuel blends as the pilot fuel. It will achieve the goal of lower exhaust emissions although the thermal efficiency remains nearby same. Diesel, biodiesel, alcohol and their blends are used as the pilot fuel, whereas biogas-air mixture is injected through intake manifold. Engine air intake system is upgraded to allow the combination of air and biogas to mix thoroughly before being fed to the cylinder. The engine performance and emission characteristics are measured and compared with conventional diesel engine. The findings of this investigation revealed that a DICI engine can efficiently be converted into a dual-fuel engine that runs on both diesel and biogas. Brake thermal efficiency decreases from 33.23% (in diesel mode) to 18.86% in dual fuel mode due to the lower calorific value of biogas compared to diesel. Whereas, the exhaust emissions like HC, CO, and CO2 are also measured and found a increment in their percentage but for NOx percentage was reduced r. Further, the results shows that the ratio 80:20 (i.e., 20% SBDO and 80% biogas) can be used in diesel engine with a very little reduction in engine performance; thus, saving about 80% of the conventional diesel fuel. Therefore, the engine performance characteristics reveal that a considerable amount of diesel can be saved with addition of biogas in dual-fuel mode.

Gasification is a thermo-chemical process which converts solid biomass into a mixture of combustible gases that can be used in various applications. In this project, a downdraft gasifier was designed and developed for running a single cylinder, 4-stroke, air cooled, direct injection diesel engine developing a power of 4.4 kW, at a rated speed of 1500 rpm on dual fuel mode. Wood chips and mustard oil cake in the ratio of 7:3 was used as a feed stock in the gasifier. An experimental study was also carried out on diesel fuel (DF) and producer gas (PG) on dual fuel mode. The producer gas was introduced in the inlet manifold of engine at 4lpm, 6lpm and 8lpm respectively. The performance and emission characteristics of the engine were studied at different loads for various gas flow rates. A reduction in the consumption of diesel fuel was observed when operated on dual fuel mode though there was a reduction in brake thermal efficiency. NO emission was found to be very low in dual fuel which is a great advantage of dual fuel mode over diesel fuel alone but, CO and HC emission for dual fuel mode was found to be higher than diesel.

In this research work, biogas was produced by the anaerobic co-digestion of cow dung with yard waste. First a laboratory scale experiment was conducted to find the best blend ratio of cow dung and yard waste which maximize the biogas production. Mechanical pre-treatment of feedstock was done to increase the specific surface area and increase the amount of biogas production. It was found that, with 75% cow-dung and 25% yard-waste (by volume) the biogas production was maximum. Further, using that optimum ratio large scale biogas production was done. The biogas was used as primary fuel and diesel as pilot fuel, in a direct injection(DI) diesel engine in dual fuel mode. Biogas was inducted through the intake manifold, at four different flow rates, viz., 0.25 kg/h, 0.5 kg/h, 0.75 kg/h and 1 kg/h, where it mixes with the air and goes to the cylinder in the suction stroke. Diesel was injected directly to the engine cylinder at the end of the compression stroke. The combustion, performance and emission characteristics of the engine in the dual fuel operation were experimentally analysed, and compared with those of diesel operation. The results indicated that, the biogas inducted at a flow rate of 0.75 kg/h was found to give a better performance and lower emission, than that of the other flow rates. The ignition delay in the dual fuel operation was found to be longer than that of diesel throughout the load spectrum. The cylinder peak pressure in the dual fuel operation was found to be overall lower than that of diesel operation. The nitric oxide(NO) and smoke emissions in the dual fuel operation are found to be decreased, compared to that of diesel operation.

Pretreatment improves the quantity of biogas produced. In this investigation, initially biogas was obtained from the co-digestion of cow dung (CD) and yard waste (YW) which were prepared at different proportions (i.e. 25:75, 50:50, 75:25 and 100% CD). The samples of feedstock were kept in different laboratory digestors. Sodium hydroxide (NaOH) at 6% by weight was added to all the samples for pretreatment. The obtained biogas from all the digestors were checked for their yield. The ratio with 75:25 CD and YW was found to be better in both yield and quality. Further, an experimental study was conducted on a single cylinder, four stroke, air cooled, direct injection (DI), diesel engine under dual fuel (diesel + biogas) mode at varying injection timings ranging from 20o to 26o crank angle (CA) before top dead centre (bTDC) in steps of 1.5oCA. The experimental results indicated the performance, emission and combustion analysis of the diesel engine in dual fuel mode.

Biodiesel is considered as one of the potential liquid alternative fuels in many countries in the world. It is produced from edible and non-edible oils, animal fat, and algae by the transesterification process. In India, Karanja (Pongamia pinnata) a non-edible oil seed is considered as a potential feedstock for biodiesel production. The de-oiled cakes of Karanja seed obtained from expeller units are of no use, and are disposed in the open. The disposal of such non edible oil cake in the open and land fill generates various anthropogenic gases, and may increase the global warming potential (GWP). The organic matters contained in these de-oiled cakes can be converted to useful energy by adopting a proper waste-to-energy conversion process. Hence, an attempt was made in this investigation to use the Karanja seed cake (SCK) as a potential feedstock for producing biogas by anaerobic digestion, and the produced biogas was proposed as an alternative fuel for CI engines. Initially, biogas was produced from four different proportions of SCK mixed with cattle dung (CD) in small scale rectors, to study the different parameters effecting the biogas production. The SCK-CD was mixed in the proportion of 75:25, 50:50, 25:75, and 0:100 in percentage on a mass basis, and the mixtures were denoted as S1, S2, S3, and S4 respectively. Important parameters, such as the pH, temperature, hydraulic retention time (HRT), and carbon/nitrogen ratio (C/N) were evaluated and analyzed. The results indicated that the sample S3 gave the best result, in comparison with the other samples, and the methane (CH4) and carbon dioxide (CO2) contents in the biogas were found to be about 73% and 17% respectively. The sample S3 was chosen for producing biogas in a large scale floating drum digester. The biogas obtained from the floating drum digester was stored in a gas bag and then characterized for its physiochemical properties, to ensure its application as a gaseous alternative fuel for CI engine.

碩士<br>國立嘉義大學<br>資訊工程研究所<br>91<br>We propose Channel Partition with Repacking Scheme (CPR) for the users with full-rate calls, half-rate calls, and dual-mode mobile stations in GSM system. The scheme partitions the time slots of GSM radio frame into two parts, one is full-slot partition that provides full-time slots for the full-rate calls, another is half-slot partition that provides half-time slots for the half-rate calls. If the time slots of the full-slot partition are not available, the system allocates the full-time slots of the half-slot partition to the full-rate calls request. If the time slots of the half-slot partition are not available, the system allocates the half-time slots of the full-slot partition to the half-rate calls request. Furthermore, consider the requests of the dual-mode mobile stations, we propose CPR with Least Repacking scheme, CPR with Maximum QoS scheme, CPR with QoS Partition scheme to improve the system performance. We evaluate the system performance by computer simulations. In the simulation, we show that our schemes can improve the usage of the time slots, and reduce the probabilities of new call blocking and handoff call failure.

The VCOST budgeting tool uses a drive cycle simulator to improve fuel economy predictions for vehicle fleets. This drive cycle simulator needs to predict the efficiency of various components of the vehicle's powertrain including any differentials. Existing differential efficiency models either lack accuracy over the operating conditions considered or require too great an investment. A fundamental model for differential efficiency is a cost-effective solution for predicting the odd behaviors unique to a differential. The differential efficiency model itself combines the torque balance equation and the Navier-Stokes equations with models for gear pair, bearing, and seal efficiencies under a set of appropriate assumptions. Comparison of the model with existing data has shown that observable trends in differential efficiency are reproducible in some cases to within 10% of the accepted efficiency value over a range of torques and speeds that represents the operating conditions of the differential. Though the model is generally an improvement over existing curve fits, the potential exists for further improvement to the accuracy of the model. When the model performs correctly, it represents an immense savings over collecting data with comparable accuracy.<br>text