This thesis proposed and demonstrated a new all-polymer based fabrication process for an all-polymer flexible and parallel optical interconnect cable having a vertical light coupler, which can not only cut down the cost by eliminating metallization process for alignment but also facilitate both in production and application. Throughout the process, polyimide was used as the substrate, coated by Epoclad as claddings, then AP2210B and WPR 5100 were used to fabricate waveguides and 45 degree mirror couplers, respectively. In addition, precisely aligned mirror couplers to waveguides are fabricated by using polymer-based, non-metallic, and transparent alignment marks. Conventional and metallic alignment marks are easy to be detected by camera, when a layer of high reflective material, generally Cr metal, is patterned. However, transparent polymer material is used in this process, as alignment marks made of it which are actually buried phase structures. Therefore, it is hardly to be observed by conventional microscopy system. Hence, to increase the contrast of the alignment marks, I proposed and tested a feature specific alignment camera system for which the shape and depth of the alignment marks are optimized for phase-based imaging, such as phase contrast and Schlieren imaging. The results showed a contrast enhancement of alignment marks image compared to that of a conventional microscopy system. By using the fabrication and alignment process, process for adding waveguides to the structure is identified by using the polymer based alignment marks on the WPR 5100 layer. Mask was made by etch down process using fused silica wafer plate, Cr and AZ 3312 photoresist. At last, the developed and proposed process provides means of all-polymer based fabrication process for a flexible and parallel optical interconnect.

<p>In this report, microrockets from the company NanoSpace were studied using schlieren imaging techniques. The rocket chips are manufactured using MEMS technology, which requires compromises regarding the shape of the nozzle. The rocket chips are 22x22x0.85 mm, manufactured from laminated silicon. The nozzles are approximately 20 µm wide at the throat, and 350 µm wide at the exit. A semi in-line schlieren apparatus was designed, set up, and aligned. A small vacuum chamber was constructed, and a series of tests was conducted in order to qualitatively evaluate the consequences of these compromises, and other performance issues. It was found that the existing 1 kW quartz-tungsten-halogen lamp was sufficient as a light source, standard photographic equipment served well as an imaging device, and a 400 mm, f/7.9 achromatic doublet as schlieren lens, resolved enough detail in the exhaust gas to perform the studies. At maximum magnification, the viewing area was 7 by 4.5 mm, captured at 14 Mpixel, or about 1.5 µm/pixel. Several different rocket chips were studied, with helium, nitrogen and xenon as propellant gases. Feed pressure ranged from 0.5 bar to 3.5 bar, and the rockets were studied at atmospheric pressure and in vacuum, and with and without heaters activated. Through these studies, verification and visualization of the basic functionality of the rockets were possible. At atmospheric pressure, slipping of the exhaust was observed, due to the severe overexpansion of the nozzle. In vacuum, the nozzle was underexpanded, and the flow was seen to be supersonic. There was a measurable change in the exhaust with the heaters activated. It was also shown that the method can be used to detect leaks, which makes it a valuable aid in quality control of the components.</p>

In this report, microrockets from the company NanoSpace were studied using schlieren imaging techniques. The rocket chips are manufactured using MEMS technology, which requires compromises regarding the shape of the nozzle. The rocket chips are 22x22x0.85 mm, manufactured from laminated silicon. The nozzles are approximately 20 µm wide at the throat, and 350 µm wide at the exit. A semi in-line schlieren apparatus was designed, set up, and aligned. A small vacuum chamber was constructed, and a series of tests was conducted in order to qualitatively evaluate the consequences of these compromises, and other performance issues. It was found that the existing 1 kW quartz-tungsten-halogen lamp was sufficient as a light source, standard photographic equipment served well as an imaging device, and a 400 mm, f/7.9 achromatic doublet as schlieren lens, resolved enough detail in the exhaust gas to perform the studies. At maximum magnification, the viewing area was 7 by 4.5 mm, captured at 14 Mpixel, or about 1.5 µm/pixel. Several different rocket chips were studied, with helium, nitrogen and xenon as propellant gases. Feed pressure ranged from 0.5 bar to 3.5 bar, and the rockets were studied at atmospheric pressure and in vacuum, and with and without heaters activated. Through these studies, verification and visualization of the basic functionality of the rockets were possible. At atmospheric pressure, slipping of the exhaust was observed, due to the severe overexpansion of the nozzle. In vacuum, the nozzle was underexpanded, and the flow was seen to be supersonic. There was a measurable change in the exhaust with the heaters activated. It was also shown that the method can be used to detect leaks, which makes it a valuable aid in quality control of the components.

<p dir="ltr">Examination of gaseous detonation flow-fields represents a unique experimental challenge. High-speed shock interaction within a reactive mixture manifests combustion modes across a range of spatial-temporal scales. While the kinetics along the leading front are often characterized by adiabatic compression, simultaneously strong shear induces turbulent mixing in downstream portions of the flow. This all occurs within a wave structure typically traveling near 2000 m/s. To advance fundamental understanding, high-resolution diagnostics are required to make quantitative, time-resolved measurements of the unsteady detonation propagation.</p><p dir="ltr">In this work, detonations are experimentally studied in a single-shot, narrow channel using non-intrusive optical diagnostics. The change in wave structure between mixtures fueled by methane and natural gas was characterized using 175 kHz schlieren and CH* chemiluminescence imaging. The effect of the higher order alkanes in natural gas is speed up the reaction kinetics and produce a wave structure with smaller spatial scales and in which reaction occurs closer to the leading shock front.</p><p dir="ltr">A schlieren system operating at a rate of 5 MHz is then implemented to resolve the spatial-temporal oscillation of the leading shock front. These images are used to compute the lead shock normal speed, which enables a statistical analysis of the oscillating shock velocity. The moments of distribution are compared with computed instability levels of sixteen mixtures and a positive correlation is found. Simultaneous chemiluminescence is used to create joint distribution of shock speed and chemical length scale, which are then compared with the quasi-steady reaction zone solution.</p><p dir="ltr">Experiments are performed with highly nitrogen diluted mixtures of methane and oxygen to examine specific flow features. Different regimes of transverse wave reactivity are observed, from nonreactive to detonative. The transverse detonation wave structure is modeled using oblique shock relations and good agreement is found. The chemical length scales within the configuration are compared to the relevant expansion scales to explain the observed near-steady propagation. Distinct reactive processes following transverse wave collision are also captured. In one instance an explosion immediately occurs, while in the other a reactive gas jet grows from the point of collision. An unsteady reaction zone model is applied to understand the reaction mode within the jet.</p><p dir="ltr">Lastly, 300 kHz OH PLIF is performed to study small scale and weak reaction structures within the flow. The evolution of deflagrative burning mechanisms becomes resolvable using this technique, which highlights the benefit of its use.</p>

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

Ce travail de thèse repose sur l’élaboration et l’exploitation d’un banc expérimental dédié à l’étude d’un écoulement cavitant dans un micro-canal, pour des conditions proches de celles de l’injection diesel. Ce banc a été développé dans le but de faire varier différents paramètres, notamment l’état de surface des parois du canal. Plusieurs méthodes optiques (imagerie en transmission, strioscopie et interférométrie) ont été mises en place afin de visualiser l’écoulementet d’en extraire des informations quantitatives. Les images en transmission permettent de visualiser la formation de vapeur dans le canal. Elles sont sensibles au gradient de masse volumique et font ainsi apparaître des couches de cisaillement, des structures turbulentes et des ondes de pression. Leur interprétation est rendue délicate par cette richesse en information et nécessite de recourir aux autres techniques optiques. Il ressort de ce travail que la cavitation se forme dans la couche de cisaillement, sous l’effet combiné de la dépression engendrée par le décollement à l’entrée du canal et de tourbillons générés par des instabilités dans la couche de cisaillement. La confrontation des résultats obtenus à l’aide des différentes techniques optiques, notamment les champs de pression reconstruits à partir des interférogrammes, montre que la zone de formation de la cavitation ne correspond pas à la zone de minimum de pression moyenne de l’écoulement. Il apparaît aussi que certaines bulles de vapeur ont une durée de vie bien supérieure à ce que prévoient les modèles de dynamique de bulles. On suspecte que des fluctuations de pression de l’ordre de 20 bar, associées à la turbulence, contribuent à la prolongation de ces temps de vie. Un algorithme de PIV, appliqué à des couples d’images en transmission, permet de montrer une augmentation importante des fluctuations de vitesse en sortie de canal lorsque les poches de vapeur se développent. Cette augmentation devient plus significative quand les poches atteignent60% de la longueur du canal. L’écoulement cavitant est essentiellement piloté par le nombre de cavitation K. Les conditions d’apparition et de développement de la cavitation ont été quantifiées dans différents canaux, en faisant varier des paramètres géométriques, la pression amont ou la température. L’influence de la hauteur du canal et du rayon de courbure à l’entrée de l’orifice est conforme aux données de la littérature. Une dépendance du nombre de cavitation critique Kcrit à l’apparition de la cavitation au nombre de Reynolds Re est montrée. Enfin, l’influence de l’état de surface des parois a fait l’objet d’une étude spécifique. Cette partie du travail demande probablement à être complétée mais l’état de surface semble avoir une influence sur la cavitation. D’après les cas étudiés au cours de cette thèse, une surface rugueuse ou texturée avec des motifs suffisamment espacés peut retarder l’apparition de la cavitation et une rugosité limitée (jusqu’à Ra = 0,7 μmici) peut favoriser le développement des poches de vapeur. / This PhD study is based on the design and use of an experimental set-up dedicated to the study of a cavitating flow in a micro-channel in conditions close to Diesel injection. The experimental set-up has been designed so that different parameters may vary, in particular channel wall roughness. Several optical systems (backlit imaging, Schlieren imaging and interferometry) have been developed in order to visualize the flow and get quantitative data.Backlit images make it possible to visualize vapor formation in the channel. They are sensitive to density gradients and therefore show shear layers, turbulent structures as well as pressure waves. Since they are rich in information, it is tricky to interpret them and the use of other optical methods is required.This study shows that cavitation appears in the shear layer due to the combined effect of the depression induced by flow detachment at the channel inlet and vortexes caused by instabilities in the shear layer. The comparison of the results obtained from the different optical systems – in particular the pressure fields rebuilt from interferograms – indicates that cavitation does not appear where flow pressure is the lowest in average.It is noticed that some vapor bubbles have a life expectancy much higher than predicted by bubble dynamics models. It is thought that pressure variations of about 20 bar, associated to turbulence, may play a role in this phenomenon.A PIV algorithm applied to couples of backlit images shows that velocity fluctuations largely increase at the channel outlet when vapor cavities develop. The increase gets more significant when cavities are 60 % the channel length.The cavitating flow is mainly dependent on the cavitation number K. The conditions of cavitation inception and development have been quantified in different channels, and geometrical parameters, upstream pressure or temperature have varied. The influence of channel height and radius inlet on cavitation is in line with the literature. At cavitation inception, it is shown that the critical cavitation number Kcrit is dependent on Reynolds number Re. Finally, the influence of wall roughness has been the subject of a specific study. Although it would need to be further investigated, roughness seems to have an influence on cavitation. The samples used during this PhD work suggest that roughness or patterns sufficiently spaced out may delay cavitation inception, and limited roughness (up to Ra = 0.7 μm here) may enhance vapor cavity development.

<p>The first force and moment measurements were conducted in the BAM6QT. Three 7-degree half-angle sharp cones were tested, one with base radius of 4.5 in. and two with base radius of 3.5 in. made out of different materials. Models were tested at 0 and 2 degrees angle of attack. Models were tested over a range of burst pressures and Reynolds numbers. Models were fitted onto a strain gauge, 6 component, internal, moment balance. Multiple assemblies were tested that mounted the balance in the BAM6QT. High-speed schlieren video was used to monitor flow conditions and track the movement of the tunnel and model. Three entries were performed in the BAM6QT. The improvement in data quality with each new entry is shown and the startup and running loads from entry 3 are analyzed.</p> <p>Startup loads were measured and are of importance in determining the load range needed to operate in the BAM6QT. Large startup loads up to 40X the running load were identified. Tunnel movement was measured and was used to approximate the inertial loading during startup and the run. The inertial loading was not found to be the cause of the large startup loads. Schlieren video was used to qualitatively review the startup flow. It was found the large startup loads in axial force were plausibly from the high-pressure subsonic flow evacuating the nozzle. For normal force and pitching moment, the startup loads peak at a different time than axial force and appear to be from a shock-shock interaction nearby the model. Trends in startup load with changing model geometry, AoA, and burst pressure were put together to form an empirical estimation for startup loads sharp cones. </p> <p>Running loads were profiled and found to be trending with burst pressure and model geometry similarly to Newtonian flow theory predictions. However, due to the lack of a base pressure measurement, the results are uncorrected for sting effects and differ from Newtonian flow theory by a scalar. A 5.3 Hz oscillation in axial force was identified. The frequency of the oscillation is the same as the frequency of the quasi-steady flow periods caused by the reflection of the expansion fan in the driver tube. Normal force during the running load was found to be measuring positive loads when at 0 degrees angle of attack. Both the axial and normal force phenomena were unexpected and were investigated but both require further research. </p> <p><br></p> <p><br></p> <p><br></p> <p><br></p>