The increased fatigue loads and decreased power output of a wind turbine placed in the wake of another turbine is a well-known problem when building new wind-power farms and a subject of intensive research. These problems are caused by the velocity gradients and high turbulence levels present in the wake of a turbine. In order to better estimate the total power output and life time of a wind-power farm, knowledge about the development and stability of wind-turbine wakes is crucial. In the present thesis, the flow field around small-scale model wind turbines has been investigated experimentally in two wind tunnels. The flow velocity was measured with both hot-wire anemometry and particle image velocimetry. To monitor the turbine performance, the rotational frequency, the power output and the total drag force on the turbine were also measured. The power and thrust coefficients for different tip-speed ratios were calculated and compared to the blade element momentum method, with a reasonable agreement. The same method was also used to design and manufacture new turbine blades, which gave an estimate of the distribution of the lift and drag forces along the blades. The influence of the inlet conditions on the turbine and the wake properties was studied by subjecting the turbine to both uniform in flow and different types of boundary layer in flows. In order to study the stability and development of the tip vortices shed from the turbine blades, a new experimental setup for phase-locked measurements was constructed. The setup made it possible to introduce perturbations of different frequencies and amplitudes, located in the rear part of the nacelle. With a newly developed method, it was possible to characterize the vortices and follow their development downstream, using only the streamwise velocity component. Measurements were also performed on porous discs placed in different configurations. The results highlighted the importance of turbine spacings. Both the measurements on the turbine and the discs were also used to compare with large eddy simulations using the actuator disc method. The simulations managed to predict the mean velocity fairly well in both cases, while larger discrepancies were seen in the turbulence intensity. / <p>QC 20140424</p>

This thesis presents a detailed, two-dimensional analysis of the performance of multi-element guard-heated hot-film wall shear stress microsensors for turbulent flows. Previous studies of conventional, single-element sensors show that a significant portion of heat generated in the hot-film travels through the substrate before reaching the fluid, causing spectral and phase errors in the wall shear stress signal and drastically reducing the spatial resolution of the sensor. Earlier attempts to reduce these errors have focused on reducing the effective thermal conductivity of the substrate. New guard-heated microsensor designs proposed to overcome the severe deficiencies of the conventional design are investigated in this thesis. Guard-heaters remove the errors associated with substrate heat conduction, by forcing zero temperature gradient at the edges and bottom face of the hot-film, and hence, block the indirect heat transfer to the flow. Air and water flow over the sensors are studied numerically to investigate design, performance and signal strength of the guard-heated sensors. Our results show, particularly for measurements in low-conductivity fluids such as air, that edge guard-heating needs to be supplemented by a sub-surface guard-heater, to make substrate conduction errors negligible. With this two-plane guard-heating, a strong non-linearity in the standard single-element designs can be corrected, and spectral and phase errors arising from substrate conduction can be eliminated. / Graduate / 0548 / etrati@uvic.ca

Investigations into the turbulent flows in uniform and nonuniform open channels by previous researchers have demonstrated the requirement and importance of understanding the turbulence structures and energy losses due to irregularity in non- uniform open channels. Responding to this requirement, the turbulent flow in one special non-uniform open channel has been studied both experimentally and numerically. This non-uniform open channel was designed so that its width and bed level vary while its cross-sectional area below the water surface keeps constant. An upstream uniforzn open channel is attached to the non-uniform open channel to establish fully developed turbulent flow conditions. A downstream uniform channel is also attached for control of water depth and downstream flow condition. The experimental study consisted of measurements of turbulent velocity field with a LDV (Laser Doppler Velocimetry) and measurements of boundary shear stress (BSS) with Roving Preston tubes in the experimental channel. Turbulent velocity components in the longitudinal and vertical directions were measured with the LDV in forward scattering mode and the laser beams were focused from the channel side wall into the water. Turbulent velocity components in the longitudinal and transverse directions were measured with the LDV in back scattering mode and the laser beams are focused from above the water surface into the water. Both the forward scattering mode measurements and the back scattering mode measurements were taken at two cross sections in the upstream uniform open-channel and at twelve cross sections in the nonuniform open channel. Obtained data include mean longitudinal velocity U, transverse velocity V, vertical velocity W, turbulence intensities u^2, v^2, w^2, and Reynolds shear stresses -uv and -uw. The chief results of these measurements are: 1) There is no separation of flow in the nonuniform open channel. 2) As flow passes from wider and shallower section to narrower and deeper section, it responds as though it experiences contraction in horizontal planes and expansion in vertical planes. The reverse occurs as flow passes from narrower and deeper section to wider and shallower section; 3) The secondary currents in the nonuniform open channel are combinations of the effects of pure contraction and expansion of channel boundaries and the effects of the vortex kind secondary currents; 4) Turbulence intensities in the non-uniform open channel show similar distribution patterns to that in the uniform open-channel but their magnitudes change due to the change of channel shape; 5) Negative values of the Reynolds shear stresses, -uw, appear at the free surface and may extend to a large depth below the free surface in the nonuniform open channel. Boundary shear stresses in the experimental channel were measured with Roving Preston tubes. The use of the Roving Preston tubes was preceded with calibrations of themselves in air pipe flow and calibrations of a special pressure transducer in air and in water. Delicate measurement procedures were designed for measurements of BSS in the nonuniform open channel. The BSS were measured at one cross section in the uniform open-channel and at twelve cross sections in the nonuniform open channel. The chief results of these measurements are: 1) The irregularity of the nonuniform open channel significantly affects the distribution of the BSS but the total shear force has little change; 2) The effect of the secondary currents on the BSS is very similar to the effect of secondary currents on the ESS in uniform open channel; 3) The irregularity in the non-uniform open channel does not cause extra energy loss since there is no flow separation. The numerical study made use of a FEM (finite element method) commercial package FIDAP to simulate the turbulent flows in the experimental channel. These simulations are carried out with Speziale's eddy-viscosity anisotropic k-E model, the standard k-E model, and the RNG model. With each model, simulations were undertaken for four consecutive uniform channels of 5 m length so that fully developed turbulent flow conditions were established before entering into the simulation of flow in the non- uniform channel. In all simulations the free surfaces were fixed. Simulation results include U, V, W, k, and E. For turbulent flow in the uniform channel, only Speziale's model is capable of predicting qualitatively correct secondary currents. For turbulent flow in the non-uniform open channel, all three models gave similar simulation results. The calculated distribution patterns of U and W are in agreement with measurements except near the free surface but differences exist in magnitude. None of the three models was capable of modelling the transverse velocity V in the nonuniform open channel correctly. Further simulations are necessary with movable free surface and better boundary condition for the energy dissipation rate s in order to achieve better agreement with the experimental values, especially near the free surface.

L’aérosolthérapie a pour objectif de délivrer un médicament dans les voies respiratoires. Le nébuliseur pneumatique est un dispositif permettant de générer des gouttelettes de liquide de diamètre micrométrique. Son processus d’atomisation a cependant été peu analysé. Ainsi, les performances du nébuliseur, caractérisées par le diamètre des gouttes et la masse de médicament inhalable par le patient, et atteignent un palier. Notre travail consiste à utiliser un modèle numérique diphasique en 3D basé sur une géométrie donnée et paramétré sous ANSYS Fluent. Plusieurs méthodes sont utilisées pour caractériser expérimentalement la génération de l’aérosol : l’ombroscopie, la diffractométrie laser et l’anémométrie phase Doppler. Notre modèle est validé par rapport aux données expérimentales et peut donc être exploité pour analyser les processus de génération. L’influence de plusieurs paramètres physiques sur les caractéristiques de l’aérosol produit est étudiée. Ainsi, l’étape de génération de gouttelettes est optimisée pour le développement d’un nouveau nébuliseur. Le transport des gouttes aux poumons du patient est optimisé empiriquement. / The purpose of aerosol therapy is to deliver drugs into respiratory airways. The jet nebulizer is a device used to generate liquid droplets with a diameter lower than 5 μm. However its atomization process was not much analyzed. Nebulizer performances, which are characterized with droplet size and drug mass inhaled by the patient, are empirically optimized and have reached a plateau. Our work consists in setting a 3D diphasic numerical model on ANSYS Fluent, based on a given geometry. Several methods are used to experimentally characterize aerosol generation: shadowgraphy, laser diffractometry and phase Doppler anemometry. Our model is validated by experimental data and helps predicting generation processes. The influence of several geometric and physical parameters on the output is studied. From these data, droplet generation is optimized for the development of a new nebulizer. Droplet transport to the patient lungs is empirically optimized.

Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-08-28T20:29:05Z No. of bitstreams: 1 TONY CARLOS MOURA CAVALCANTI – TESE (PPGEEI) 2016.pdf: 4469755 bytes, checksum: 884382b3c566b4aca499dc522be900ab (MD5) / Made available in DSpace on 2018-08-28T20:29:05Z (GMT). No. of bitstreams: 1 TONY CARLOS MOURA CAVALCANTI – TESE (PPGEEI) 2016.pdf: 4469755 bytes, checksum: 884382b3c566b4aca499dc522be900ab (MD5) Previous issue date: 2016-12-12 / CNPq / O objetivo neste trabalho é propor um sistema para a hidrometria na faixa de submedição utilizando a anemometria térmica. O objetivo de medir vazão está presente em muitos campos da ciência, sendo necessário sabermos quais os valores de um material foram consumidos com o menor erro possível. Na primeira parte da pesquisa foram realizadas simulações em ambiente multifísico para identificar as condições de trabalho e possíveis pontos de localização do sensor. Para poder usar o sensor, é necessário conhecer valores limítrofes de trabalho do mesmo, ou seja, a faixa de operação, indicando assim a vazão mínima e máxima de operação do sensor anemométrico. Portanto, na segunda etapa do trabalho, foi proposta uma plataforma com um sistema de bombeamento para testar o sistema de medição proposto. A plataforma foi construída de modo a permitir que um fluído flua através de uma tubulação e, assim, determinar qual é a velocidade do fluído e, portanto, a vazão. / The objective of this work is to propose a system for the hydrometry in the sub-measurement range using thermal anemometry. The objective of measuring flow is present in many fields of science, it is necessary to know what values of a material were performed using COMSOL software to identify working conditions and maximum flow rate of the anemometric sensor. Therefore, in the second stage of the work, a platform with a pumping system was proposed in order to test the proposed measurement system. The platform was constructed so as to allow a fluid to flow through a pipeline, and thereby determine what the velocity of the fluid, and hence the flow, is.

Orientadores: Maria Regina Wolf Maciel, Antonio Andre Chivanga Barros, Henry França Meier / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-05T18:14:26Z (GMT). No. of bitstreams: 1 Soares_Cintia_D.pdf: 3816439 bytes, checksum: e39afd5653e2802b28899a3c09f4753c (MD5) Previous issue date: 2005 / Resumo: Grande parte dos estudos envolvendo colunas de destilação está fundamentada por modelos macroscópicos de conservação de massa e de energia. Exemplo disto são os modelos de estágios de equilíbrio e de não-equilíbrio. Nestes, os aspectos fluidodinâmicos do escoamento são restritos e orientados à medição de parâmetros macroscópicos. Porém, graças aos avanços introduzidos pelo emprego das técnicas da fluidodinâmica computacional (CFD), a análise de processos empregando uma abordagem microscópica tornou-se mais sofisticada e precisa. Além disto, há necessidade de trabalho experimental com o propósito de validar modelos e métodos em CFD e medir outros parâmetros ao longo do equipamento. Dentro deste contexto, este trabalho visa o desenvolvimento de uma metodologia de caráter numérico e experimental que possibilite o estudo do escoamento líquido-vapor, em nível microscópico, em um prato perfurado de uma coluna de destilação. Para tanto, objetiva-se a proposição de um modelo microscópico de conservação da quantidade de movimento, em condições de escoamento turbulento, sob a influência da fase vapor, e de uma metodologia para a aquisição de dados experimentais. A metodologia numérica consistiu em iniciar com um estudo aprofundado do escoamento com superfície livre, utilizando um módulo experimental de hidráulica, seguido do estudo do escoamento monofásico na superfície de um prato perfurado. Estudos em uma coluna de bolhas permitiram a obtenção de experiência com modelos e métodos associados ao escoamento multifásico. Finalmente, foram realizados estudos sobre o escoamento líquido-vapor em pratos perfurados com a proposição de um modelo 3-D e homogêneo. Na metodologia de solução, o principal objetivo esteve relacionado às características numéricas, tais como: fatores de relaxação, esquemas de interpolação, integração temporal, acoplamento pressão-velocidade, entre outras. A metodologia experimental consistiu no projeto e construção de uma coluna de destilação para a simulação física do escoamento líquido-vapor em um estágio a frio, sendo as informações microscópicas obtidas por meio do emprego da técnica de anemometria térmica. Técnicas de visualização do escoamento foram empregadas como ferramenta de análise qualitativa na identificação de padrões de escoamento, como mecanismo de apoio à realização de medidas experimentais e, finalmente, como instrumento complementar de análise para facilitar a interpretação dos resultados. A metodologia numérica permitiu a avaliação de estratégias de solução de modelos e métodos em CFD, além do desenvolvimento de um modelo homogêneo capaz de predizer o escoamento líquidovapor, em nível microscópico, em um prato perfurado de uma coluna de destilação. A metodologia experimental permitiu a caracterização do escoamento em um tanque retangular, entretanto, a técnica de anemometria térmica apresentou limitações quando da aplicação no escoamento bifásico. Na análise dos resultados obtidos concluiu-se que há a ocorrência de diferentes padrões de escoamento no interior de uma coluna de destilação, de acordo com a vazão da fase gás e da geometria do prato, sendo o escoamento não uniforme. Além disto, há uma tendência do fluxo de líquido próximo à parede retroceder, o que resulta no fenômeno de circulação. Outra observação importante foi que a fase vapor, em contato com o líquido fluindo horizontalmente, obtém uma energia cinética na direção do fluxo de líquido / Abstract: Greater part of researches involving distillation columns is based on macroscopic models of mass and energy conservation. Examples are the equilibrium and non-equilibrium stage models. In these cases, the fluid dynamics characteristics are restricted in measuring macroscopic parameters. However, advances introduced by fluid dynamic techniques made possible a more sophisticated and accurate process analysis using a microscopic approach. Researches in this area are indispensable and more experimental studies is necessary in order to validate models and methods in CFD and measure other parameters along the equipment. Based on these statements, this work takes aim the development of a numerical and experimental methodology that enables the study of liquid-vapour flow, in a microscopic level, on a sieve plate of a distillation column. It is proposed the development, implementation and application of a microscopic model for momentum conservation subjected to turbulent flow of the vapour phase, complemented by the development of an experimental methodology for data acquisition in an apparatus in laboratory scale. The numerical methodology consisted to make a deep study of flow with free surface using a hydraulic modulus and a study of a single-phase flow on a sieve plate. Studies in a bubble column allowed building knowledge for modelling momentum transfer phenomenon in multiphase flow. Finally, studies about the liquid-vapour flow in sieve plates were carried out with development of a 3-D and homogeneous model. The main objective in the solution methodology was related to numerical characteristics, such as: relaxation factors, interpolation schemes, temporal integration and pressure-velocity coupling. The experimental methodology consisted in the design and building of a distillation column that simulates the liquid-vapour in a sieve plate. The information related to velocity profiles were obtained by means of definition and implementation of the thermal anemometry technique. During the numerical and experimental studies, flow visualization techniques have also been employed in different ways as a tool for qualitative analysis of different flow patterns, as an assistance to the experimental measures, and finally, as a complement to the analysis, supporting the interpretation of results. The numerical methodology allowed the evaluation of models and methods strategies in CFD, and the development of a homogeneous model able to predict the liquid-vapour flow in a sieve plate of a distillation column. On the other hand, the experimental methodology allowed the evaluation of flow inside a rectangular reservoir, but the thermal anemometry technique presented limitations in the multiphase flow. It was concluded that there is the occurrence of different flow patterns inside the distillation column, according to the gas flow and plate geometry, and the flow is not uniform in the plate surface. Besides, there is a tendency of the liquid flow to go back near the wall, resulting in a circulating zone. Other observation was that the vapour phase, contacting with the horizontally flowing liquid, gains a kinetic energy in the direction of liquid flow / Doutorado / Desenvolvimento de Processos Químicos / Doutor em Engenharia Química

The principle of controlled auto-ignition (CAI) is to mix fuel and air homogeneously before compressing the mixture to the point of auto-ignition. As ignition occurs simultaneously, CAI engines operate with lean mixtures preventing high cylinder pressures. CAI engines produce small amounts of nitrogen oxides (NOx) due to low combustion temperatures while maintaining high compression ratios and engine efficiencies. Due to simultaneous combustion and lean mixtures, CAI engines are restricted between low and mid load operations. Various strategies have been studied to improve the load limit of CAI engines. The scope of the project is to investigate the consequences of varying valve timing, as a method to control the mixture temperature within the combustion chamber and therefore, controlling the mixture auto-ignition point. This study presents computational fluid dynamics (CFD) modelling results of transient flow, inside a 0.45 litre Lotus single cylinder engine. After a validation process, a chemical kinetics model is combined with the CFD code, in order to study in-cylinder temperatures, the mixture distribution during compression and to predict the auto-ignition timing. The first part of the study focuses on validating the calculated in-cylinder velocities. A mesh sensitivity study is performed as well as a comparison of different turbulence models. A method to reduce computational time of the calculations is presented. The effects of engine speed on charge delay and charge amount inside the cylinder, the development of the in-cylinder flow field and the variation of turbulence parameters during the intake and compression stroke, are studied. The second part of the study focuses on the gasoline mixture and the variation of the valve timing, to retain different ratios of residual gases within the cylinder. After validation of the model, a final set of CFD calculations is performed, to investigate the effects of valve timing on flow and the engine parameters. The results are then compared to a fully homogeneous mixture model to study the benefits of varying valve duration. New key findings and contributions to CAI knowledge were found in this investigation. Reducing the intake and exhaust valve durations created a mixture temperature stratification and a fuel concentration distribution, prior to auto-ignition. It resulted in extending the heat release rate duration, improving combustion. However, shorter valve timing durations also showed an increase in heat transfer, pumping work and friction power, with a decrease of cylinder indicated efficiency. Valve timing, as a method to control auto-ignition, should only be used when the load limit of CAI engines, is to be improved.

En la exploración de nuevos métodos para el mejoramiento de la eficiencia y rendimiento del motor diésel, es claro que un gran esfuerzo debe estar enfocado en el proceso de inyección de combustible. La eficiencia de la combustión y las emisiones, se ven muy afectadas por el proceso de atomización, y se ha demostrado que incrementos en presiones de inyección conllevan un gran potencial para mejorar el ahorro de combustible, producir mejores mezclas de aire y combustible, y por tanto menor generación de emisiones contaminantes. Últimamente, las presiones de inyección han aumentado de alrededor de 50 MPa en los años 70 hasta 250 MPa en los días actuales. Presiones de inyección muy altas (250-300 MPa) o incluso ultra altas (> 300 MPa) vienen siendo materia de investigación con el fin de ser implementadas de manera comercial en un futuro próximo. La estructura y desarrollo del spray diésel pueden ser caracterizados desde un punto de vista microscópico por medio de la medición del tamaño de gotas del spray y sus velocidades. En condiciones no-evaporativas, técnicas como el PDPA (Phase Doppler Particle Analyzer) vienen siendo utilizadas para la obtención de perfiles de diámetros y velocidades de gota con una alta resolución temporal. Desde el punto de vista macroscópico, existen parámetros específicos que permiten caracterizar a un chorro diésel, estos son: la penetración de vapor y líquida junto con el ángulo de apertura del chorro. La penetración líquida es un indicador claro de la capacidad de evaporación del combustible utilizado, mientras que la penetración de vapor, por su parte, es indicativo del proceso de mezcla y la probabilidad de colisión con las paredes de la cámara de combustión; factores claves a la hora de la generación de emisiones contaminantes. En esta tesis se estudia la influencia de presiones bajas, medias y muy altas presiones inyección, sobre un amplio espectro de condiciones y diagnósticos experimentales, y desde el punto de vista macroscópico y microscópico. Se realizaron experimentos para tres diferentes inyectores, 2 solenoides y un piezo eléctrico, este último con la capacidad de alcanzar presiones de inyección cercanas a 270 MPa. Las medidas incluyen una caracterización hidráulica, compuesta por tasa de inyección; una visualización de alta velocidad del chorro líquido isotermo; una visualización de alta velocidad del chorro inerte evaporativo, con captura simultánea de las fases líquida y vapor; y finalmente, una caracterización microscópica por medio de la obtención de distribución de tamaño de gotas y sus velocidades. Con respecto a los ensayos microscópicos, se desarrolló una metodología para el aislamiento y alineación de sprays con un error de medición muy bajo de 0,22°. Se llevaron a cabo mediciones de velocidad de gotas, cuyos resultados mostraron buen ajuste con perfiles teóricos de velocidad. De igual manera, una correlación para el tamaño de gota SMD se obtuvo mostrando un alto nivel de ajuste y siendo representativa para todo el rango de presiones de inyección estudiados. En el caso de la caracterización macroscópica del chorro isotermo, se han detectado variaciones macroscópicas en el desarrollo del chorro con propiedades de gas, inclusive en condiciones de motor comunes. Para estimar estos efectos y otros que las presiones de inyección muy altas tendrían sobre la estructura del chorro, se incentivó la aparición de ondas de choque controlando la velocidad del sonido del ambiente. Se usaron tres gases ambientales (SF6 N2 y CO2) con diferentes velocidades de sonido, promoviendo de esta manera chorros supersónicos en determinados casos. Al comparar ensayos con mismas densidades y diferentes gases ambientales, se encontró que todas las tendencias cercanas al estado transónico (0.8 <M <1.2) tenían una mayor penetración y menor ángulo de chorro. / En l'exploració de nous mètodes per al millorament de l'eficiència i rendiment del motor dièsel, és clar que un gran esforç s'ha enfocar en el procés d'injecció de combustible. L'eficiència de la combustió i les emissions, es veuen molt afectades pel procés d'atomització, i s'ha demostrat que increments en pressions d'injecció comporten un gran potencial per a millorar l'estalvi de combustible, produir millors mescles d'aire i combustible, i per tant menor generació d'emissions contaminants. Últimament, les pressions d'injecció han augmentat d'al voltant de 50 MPa en els anys 70 fins a 250 MPa en els dies actuals. Pressions d'injecció molt altes (250-300 MPa) o inclús ultra altes (> 300 MPa) vénen sent matèria d'investigació a fi de ser implementades de manera comercial en un futur pròxim. L'estructura i desenrotllament de l'esprai dièsel poden ser caracteritzats des d'un punt de vista microscòpic per mitjà del mesurament de la grandària de gotes de l'esprai i les seues velocitats. En condicions no-evaporatives, tècniques com el PDPA (Phase doppler particle analyzer) vénen sent utilitzades per a l'obtenció de perfils de diàmetres i velocitats de gota amb una alta resolució temporal. Des del punt de vista macroscòpic, hi ha paràmetres específics que permeten caracteritzar a un doll dièsel, estos són: la penetració de vapor i la penetració líquida junt amb l'angle d'obertura del doll. La penetració líquida és un indicador clar de la capacitat d'evaporació del combustible utilitzat, mentres que la penetració de vapor, per la seua banda, és indicatiu del procés de mescla i la probabilitat de col·lisió amb les parets de la cambra de combustió; factors claus a l'hora de la generació d'emissions contaminants. En esta tesi s'estudia la influència de pressions d' injecció baixes, mitges i molt altes, sobre un ampli espectre de condicions i diagnòstics experimentals, i des del punt de vista macroscòpic i microscòpic. Es van realitzar experiments per a tres injectors diferents, 2 solenoides i un piezo elèctric, este últim amb la capacitat d'aconseguir pressions d'injecció pròximes a 270 MPa. Les medides inclouen una caracterització hidràulica, composta per taxa d'injecció; una visualització d'alta velocitat del doll líquid isoterm; una visualització d'alta velocitat del doll inert evaporativo, amb captura simultània de les fases líquida i vapor; i finalment, una caracterització microscòpica per mitjà de l'obtenció de distribució de grandària de gotes i les seues velocitats. Respecte als assajos microscòpics, es va desenrotllar una metodologia per a l'aïllament i alineació d'esprais amb un error de mesurament molt davall de 0,22°. Es van dur a terme mesuraments de velocitat de gotes, els resultats van mostrar bon ajust amb perfils teòrics de velocitat. De la mateixa manera, una correlació per a la grandària de gota SMD es va obtindre mostrant un alt nivell d'ajust i sent representativa per a tot el rang de pressions d'injecció estudiats. En el cas de la caracterització macroscòpica del doll isoterm, s'han detectat variacions macroscòpiques en el desenrotllament del doll amb propietats de gas, inclusivament en condicions de motor comú. Per a estimar estos efectes i altres que altes pressions d'injecció tindrien sobre l'estructura del doll, es va incentivar l'aparició d'ones de xoc controlant la velocitat del so de l'ambient. Es van usar tres gasos ambientals (SF6, N2 i CO2) amb diferents velocitats de so, promovent d'esta manera dolls supersònics en determinats casos. Al comparar assajos amb mateixes densitats i diferents gasos ambientals, es va trobar que totes les tendències pròximes a l'estat transónic (0.8 < M < 1.2) tenien una major penetració i menor angle de doll. Respecte al doll evaporatiu, per a pressions d'injecció molt altes com 270MPa, els efectes dels paràmetres ambientals i d'injecció van romandre iguals respecte a totes les carac / In the exploration of new methods for improving the efficiency and performance of the diesel engine, it is clear that a great effort should be focused on the fuel injection process. The efficiency of combustion and emissions are greatly affected by the atomization process, and it is considered that injection pressures increments have a great potential to improve fuel economy, produce better air and fuel mixtures, and thus low generation of polluting emissions. Lately, injection pressures have increased from around 50 MPa in the 70's to 250 MPa in the current days, even very high injection pressures (250-300 MPa) or ultra high pressures (> 300 MPa) have been the subject of the scientific community in order to be implemented in future injection systems. The structure and development of the diesel spray can be characterized from a microscopic point of view by means of estimation of droplets size and velocities. At non-evaporative conditions, techniques such as PDPA (Phase Doppler Particle Analyzer) are being used to obtain diameters and velocity profiles a with high temporal resolution. From the macroscopic point of view, there are specific parameters that allow characterizing the diesel spray, these are: the liquid and vapor penetration along with the spray angle. The liquid penetration is a clear indicator of the evaporation capacity of the fuel used, whilst the vapor penetration, on the other hand, is an indicative of the mixing process and the probability of collision with the combustion chamber walls; key factors when generating polluting emissions. In this thesis the influence of low and very high injections pressures over the macro and micro characteristics of the diesel spray is studied, over a wide spectrum of conditions and experimental diagnoses. Experiments were carried out for three different injectors, two solenoids and one piezoelectric, the latter with the capacity to reach injection pressures close to 270MPa. The measurements include a hydraulic characterization; a high speed visualization of the liquid spray at isothermal conditions; a high-speed visualization of the evaporative spray, with simultaneous capture of the liquid and vapor phases; and finally, a microscopic characterization. Regarding the microscopic tests, a methodology was developed for the spray isolation and alignment with a very low measurement error of 0.22° Droplets velocity measurements were carried out, the results showed good adjustment with theoretical velocity profiles. Similarly, a correlation for SMD droplet size was obtained showing a high level of adjustment and being representative for the entire range of injection pressures studied. In the case of the macroscopic characterization of the isothermal spray, variations have been detected in the development of the jet with gas properties, even at common engine injection conditions. To estimate these effects and others that very high injection pressures would have on the spray structure, the apparition of shock waves was enhanced by controlling the speed of sound of the environment using three ambient gases with different speed of sound (SF6, N2 and CO2). When comparing tests with same densities and different ambient gases, it was found that all the tendencies near the transonic state (0.8 <M <1.2) had a higher penetration and lower spray angle. With respect to the evaporative jet, for very high injection pressures like 270MPa, the effects of the environmental and injection parameters remained the same with respect to all the macroscopic characteristics. / Giraldo Valderrama, JS. (2018). Macroscopic and microscopic characterization of non-reacting diesel sprays at low and very high injection pressures [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/113643 / TESIS

Examensarbetet har utförts hos RotoSub AB i Linköping. RotoSub fokuserar på innovativa lösningar inom brusreducering för fläktar och är även utvecklingspartner med det österrikiska företaget Noctua, som utvecklar och tillverkar kompaktfläktar och processorkylare inom elektronikbranschen. Under examensarbetet har en flödestestkammare för kompaktfläktar utvecklats och tillverkats. Testkammaren utnyttjar ett högupplöst motstånd som ger möjlighet till ett flertal driftpunkter för att konstruera detaljerade fläktkurvor. Detta låter RotoSub noggrant analysera och undersöka fläktkaraktäristiken under utvecklingsstadiet. I rapporten undersöks två metoder för att bestämma luftflödet genom testkammaren. Däribland en känd geometri i form av munstycken, enligt den amerikanska standarden ANSI/AMCA 210-16 samt utnyttjandet av en varmtrådsanemometer. Vidare undersöks alternativ för att konstruera ett högupplöst motstånd med hög pålitlighet och repeterbarhet, samt en tryckmätningsmetod som tillåter en jämn avläsning av det statiskatrycket som testfläkten ger upphov till. Under utvecklingen tillverkades prototyper där koncept testades och utvärderades, innan slutprodukten kunde modelleras i ett CAD-program för att slutligen tillverkas fysiskt. Slutprodukten tillverkades huvudsakligen i styren-akrylnitril (SAN) samt ett fåtal komponenter i polylaktid (PLA) och aluminium. Testkammaren använder sig av en tryckring med fyra tryckportar, en varmtrådsanemometer för att mäta luftflödet samt en roterande skiva som drivs av en stegmotor för att högupplöst variera motståndet i testkammaren. Testkammaren har visat sig kapabel att konstruera fläktkurvor för samtliga fläktstorlekar undersökta under arbetet med god repeterbarhet. Vidare arbete finns gällande tätning, då ett visst läckage finns i testkammaren vilket ger ett systematiskt fel i fläktkurvorna vid låga flöden där maximalt statiskt tryck inte kan uppnås. / This undergraduate thesis has been carried out at RotoSub AB in Linköping, Sweden. RotoSub develop innovative solutions for noise-reduction in fans. RotoSub are also development partners to the Austrian company Noctua, who design and develop fans and processor coolers for the electronics industry. During the thesis a compact airflow test chamber has been designed and constructed. The test chamber utilises a high-resolution load to measure and create a fan curve. The high-resolution load ensures that a large amount of operating points can be measured, which gives RotoSub the opportunity to closely analyse the characteristics of the fan being tested. In this thesis two different methods of measuring the airflow through the test chamber have been studied. Firstly a method of using nozzles to calculate the flow according to the standard ANSI/AMCA 210-16. Secondly the use of hot-wire anemometry to measure the airflow through the test chamber. Methods of measuring static pressure behind the test fan with high accuracy and stable readings have also been studied. Different high-resolution loads have been studied to ensure high repeatability and reliability. During the development phase, prototypes of the different components were created to allow for testing and evaluation before a final design was chosen. After the designs for each component was decided, the final design was modelled in CAD before being fabricated and constructed. The construction mostly utilises styrene-acrylonitrile (SAN) but with certain components made from polylactic acid (PLA) and aluminium. Pressure readings are taken behind the fan being tested using static ports placed on the outside of a hollow diffuser, mounted on the inlet of the test chamber. The hollow diffuser is filled with foam to stabilise the pressure readings. The chosen method of measuring airflow through the test chamber was hot-wire anemometry for its broad measurement range, high accuracy and simplicity in implementation. The design of the high-resolution load was chosen to be a rotating gate with two ports. As the gate rotates these ports openor close. The rotating gate is driven by a stepper-motor. This design allowed for very fine control at high loads and ensures reliable operation with a minimal amount of moving parts. Tests with the finished test chamber have shown that the test chamber is capable of measuring and creating high-resolution fan curves with high repeatability. However the test chamber cannot measure static pressure at zero flow as there are currently leaks within the test chamber that allows a small amount of flow through the chamber when the variable load is fully closed. This leads to a systematic error when creatingfan curves, mainly at lower flow rates and higher static pressures. Further work with this test chamber is needed to reduce leaks, which would improve measurement precision.

Many industrial applications acquire necessary thermal energy through the combustion process. The basic element of each combustion appliance is a burner and one~part~of~it~is a~nozzle system that supplies fuel to a combustion chamber. The geometry of the fuel nozzle significantly affects the intensity of mixing the fuel with the combustion air and thus the stability of the combustion. The main subject of~this diploma thesis is~determination of~velocity coefficients for nozzles with different geometries. The knowledge of~correct values of~velocity coefficients is a key parameter for the design of~the burner and~its subsequent operation. For the calculation of~velocity coefficients, the exit nozzle velocities were used. For chosen nozzles, a~theoretical exit nozzle velocities were calculated. They were compared with the actual exit nozzle velocities, which were measured experimentally using the hot-wire anemometry, and with velocities, which were calculated using the CFD simulation method.