Ce travail de recherche examine aux échelles globale et locale les caractéristiques thermo-hydrauliques au sein des échangeurs à plaques ondulées pour les écoulements monophasiques et en mode condensation. Il comprend deux parties :La première partie concerne l'analyse des structures d'écoulement en mode monophasique à partir d'un outil de simulations numériques, et dont les résultats sont validés à partir d'une campagne expérimentale. L'exploitation des résultats de simulations, à partir d'observables judicieusement sélectionnées, a permis de quantifier les grandes classes d'écoulement en fonction des paramètres géométriques et fluidiques de l'échangeur. Ce nouvel éclairement sur les structures d'écoulement a conduit à la proposition d'un modèle général original sur les lois de friction au sein de ces échangeurs de géométrie d'écoulement complexe.La deuxième partie concerne l'étude de la condensation de la vapeur avec et sans surchauffe en entrée de l'échangeur. Ainsi, un dispositif expérimental permettant le contrôle précis des conditions aux limites a été développé, et une métrologie spécifique, basée sur la thermographie infrarouge a également été mis au point, afin de remonter à certaines grandeurs locales le long du condenseur (titre de vapeur, coefficient d'échange thermique...). On observe ainsi une très forte variabilité des coefficients d'échanges thermiques et de la densité de flux de chaleur le long du condenseur, et la surchauffe de la vapeur tend à intensifier les transferts thermiques. Ce complément de mesures remet en question certaines hypothèses de la littérature quant à l'élaboration de corrélations sur les transferts de chaleur dans les condenseurs. / This research work examines at the global and local scales the thermo-hydraulic characteristics of plate heat exchangers with corrugated chevron plates, for single-phase and condensation flows. The study is divided into two parts:The first part concerns the analysis of flow structures of single-phase flows using numerical simulations, which are validated using the results of the experimental campaign. The analysis of the simulations results, from a flow characteristic observable that has been carefully chosen, has allowed quantifying the main flow categories as a function of the heat exchanger geometric parameters and the flow characteristics. This new information on the flow structures has led to the proposal of an original generalized model of the friction law inside this type of heat exchanger with complex geometry.The second part concerns the study of condensation with and without vapor superheating at the inlet of the heat exchanger. Thus, a specific experimental setup allowing precise control of the boundary conditions has been developed. Otherwise a specific metrology, based on infrared thermography, has been set to the point in order to determine the variation of certain local quantities along the condenser (vapor mass fraction, heat transfer coefficient...). Thus, we observe a high and wide variability of the heat transfer coefficients and the heat flux density along the condenser, and the superheating of the vapor tends to increase the heat transfers. These additional measures question certain assumptions of the literature regarding the development of heat transfer correlations in plate heat condensers.

A bord des véhicules électriques (VE) et Hybrides (VEH), les fonctions de tractions sont assurées par des convertisseurs électroniques de puissances. Ces derniers sont constitués de module de puissance (IGBTs ou MOSFETs). Au cours de leur fonctionnement, ces modules sont parfois soumis à de fortes contraintes électriques et thermiques qui amènent à une défaillance ou même à une destruction. Le premier objectif sera de réaliser un banc expérimentale permettant d’étudier le vieillissement des modules IGBTs en régîmes extrêmes de fonctionnement (mode de court-circuit). Ainsi, nous évaluerons les différents indicateurs de vieillissements permettant de prédire la défaillance du composant. Il sera question aussi de suivre le vieillissement ou une dégradation initié sur les composants IGBTs par thermographie infrarouge. Le second objectif sera de modéliser et simuler par éléments finis différentes structures d’IGBTs, afin de valider les modèles en fonctionnement statique et dynamique. L’avantage de l’approche multicellulaire par rapport à l’approche unicellulaire sera mis en avant. / On board electric vehicles (EVs) and hybrid (HEV), the functions of traction is provided by power electronic converters. These consist of power modules (IGBT or MOSFET). During their operation, these modules are sometimes subjected to high electrical and thermal stresses that lead to failure or even destruction.The first objective will be to achieve experimental bench to study ageing IGBT modules under extreme operating conditions ( short circuit mode). Thus, we evaluate the various indicators of ageing to predict component failure. Topics will also follow the ageing or degradation initiated on IGBT components by infrared thermography. The second objective is to model and simulate by finite element different IGBT structures to validate the models in static and dynamic operation. The advantage of multicellular approach to the single cell approach will be highlighted.

Cette étude présente la caractérisation du comportement mécanique et la tenue en fatigue d’un composite thermoplastique à matrice PEEK renforcée en fibres de carbone courtes pour des applications aéronautiques. La première partie présente la description des matériaux étudiés ainsi que la mise en place d’un protocole de caractérisation de la microstructure. Il est alors mis en avant la nécessité de générer des éprouvettes de caractérisation simples en introduisant le concept d’éprouvettes amincies. Dans un second temps, la méthode d’auto-échauffement en régime transitoire est appliquée en concluant sur l’influence de différents paramètres sur le bilan énergétique tels que la microstructure ou le grade du matériau étudié. La troisième partie présente l’établissement d’une loi de comportement phénoménologique avec une prise en compte locale de l’anisotropie par des approches micromécaniques classiques. Les simulations mécanique et énergétique donnent des résultats corrélant très bien avec l’expérimentale pour une distribution d’orientation proche de 0° et des résultats moins convaincants pour une distribution d’orientation proche de 90°. La dernière partie présente l’utilisation d’un protocole de caractérisation rapide basé sur les essais d’auto-échauffement. Cette approche, validée pour les différents matériaux étudiés, permet de prédire la courbe d’endurance en fatigue déterministe avec une seule éprouvette et en une demi-journée d’essais. Il est également mis en évidence qu’un critère énergétique à deux paramètres est indépendant de la distribution d’orientation, et qu’il est possible de discriminer rapidement en fatigue les différents matériaux étudiés. / This study deals with characterization of the mechanical behavior and the fatigue lifetime of a short carbon fibers reinforced PEEKmatrix thermoplastic composite. The first part presents the description of the materials studied and the implementation of the characterization of the microstructure. It’s then emphasized the need to generate simple characterization samples by introducing the concept of thin specimens. In a second step, the heat build-up protocol is applied on the studied materials. It is then highligthed the influence on the energetic assessment of various parameters as the microstructure or the choice of material. The third part presents the etablishment of a phenomenological law of behavior with a local consideration of anisotropy using conventional micromechanical approaches. The mechanical and energetic simulations give resultats correlating very well with the experimental ones for a distribution of orientation close to 0°. The last part presents the use of the heat build-up technique to predict the fatigue lifetime. This approach uses an energetic criterion with two parameters and is able to predict the deterministic fatigue curve with one sample, in half a day. It is then shown the capability to catch the influence of the variations of matrix grade and fibers content on the fatigue properties and validates the use of the technique for fastmaterials screening.

L'objectif de cette thèse est d'étudier expérimentalement les phénomènes de vieillissement dus à la diffusion des atomes en solution dans les alliages d’aluminium et les instabilités qui leur sont associées comme le phénomène Portevin-Le Châtelier ou les bandes de Lüders et de proposer une modélisation de ces phénomènes dans le cadre de la thermodynamique des processus irréversibles. Une étude expérimentale détaillée est alors entreprise sur les alliages d’aluminium AA5083-H116 et AA5182-O. Le comportement du premier présente l’effet PLC de façon prononcée et les deux types d’instabilités sont observées simultanément pour le second. La corrélation d'images numériques et la thermographie infrarouge sont essentiellement employées pour détecter et caractériser les aspects spatiotemporels des instabilités observées. La déformation non homogène due à l’apparition et la propagation de bandes de localisation est mise en évidence. Ces bandes de déformation sont visualisées, permettant à leurs diverses caractéristiques (vitesse, orientation, largeur, vitesse de déformation à l'intérieur des bandes, augmentation de la température à l'intérieur des bandes) d'être mesurées sur des éprouvettes lisses (plates, cylindriques ou prismatiques). Dans le cas des éprouvettes plates, l’effet des épaisseurs de l’éprouvette a aussi été examiné. Les caractéristiques des bandes sont aussi analysées sur d’autres géométries d’éprouvette (entaillées avec divers types d’entailles) à des vitesses de déformation différentes pour exhiber leur morphologie en présence de chargements multiaxiaux. Des simulations non linéaires et tridimensionnelles ont été effectuées en utilisant le modèle de McCormick pour montrer comment la prise en compte des phénomènes de vieillissement, même partielle, permet de décrire les hétérogénéités et le mouvement des bandes de déformation ainsi que de prévoir leurs différentes caractéristiques. Enfin, en se basant sur les mécanismes physiques à la base des phénomènes de vieillissement et en soulignant les limites du modèle de McCormick, un modèle élasto-viscoplastique prenant en considération les phénomènes de vieillissement est proposé dans le cadre de la thermodynamique des processus irréversibles. / The objective of this thesis is to study experimentally the ageing phenomena due to the atoms diffusion in solid solutions in aluminium alloys and associated instabilities as the Portevin-Le Châtelier phenomenon or the Lüders bands and to propose a model of these phenomena within the framework of thermodynamics of irreversible processes. Digital Image Correlation (DIC) and Digital Infrared Thermography (DIT) are essentially employed to capture and characterize the spatio-temporal aspects of these instabilities. Inhomogeneous deformation, due to the appearance and the propagation of various localization bands are observed. These deformation bands are visualized, allowing their various characteristics (velocity, orientation, width, strain rate inside the bands, temperature increase inside the bands) to be measured on smooth specimens (flat, cylindrical or prismatic). In the case of flat test, the effect of the specimen thickness was also examined. The band characteristics are also analyzed on other specimen geometries (notched with various kinds of notches) at different strain rates to exhibit their morphology in the presence of multiaxial loadings. Some nonlinear and three-dimensional simulations were carried out with McCormick model to show how the inclusions of ageing phenomena, even partial, makes possible to describe heterogeneities and the deformation bands but also reproducing qualitatively their various characteristics. Finally, based on the physical mechanisms of aging phenomena and underlying the limitations of the McCormick model, an elasto-viscoplastic model taking into account the aging phenomena is proposed in the framework of thermodynamics of irreversible processes.

This diploma thesis discusses the problems of defects and faults of external thermal insulation composite systems. The first part describes the correct procedures for application systems, the next part describes defects, faults and their causes and the end of the thesis describes the contactless diagnostic methods used for the survey of ETICS. This part is mainly focus on detection of anchors. The example shows the calculation of anchoring.

Boiling is used in a wide variety of industries, including electronics cooling, distillation, and power generation. Fundamental studies on the boiling process are needed for effective implementation. Key performance characteristics of boiling are the heat transfer coefficient, which determines the amount of heat flux that can be dissipated for a given superheat, and critical heat flux(CHF), the failure point that occurs when vapor blankets the surface. The wettability of a surface is one of the key parameters that affects boiling behavior. Wetting surfaces(e.g., hydrophilic surfaces), typically characterized by a static contact angle below 90°,have better critical heat flux due to effective rewetting, but compromised heat transfer coefficients due to increased waiting times between nucleation of each bubble. Meanwhile, nonwetting surfaces (e.g., hydrophobic surfaces), characterized by static contact angles greater than 90°, have better heat transfer coefficients due to improved nucleation characteristic, but reach critical heat flux early due to surface dry out. However, recent studies have shown that the static contact angle alone offers and incomplete, and sometimes inaccurate, description of this behavior, which is instead governed entirely by the dynamic wettability. Specifically, the receding contact angle impacts the size and contact area of bubbles forming on a surface during boiling, while the advancing contact angle determines how the bubble departs. With this more complete set of wettability descriptors, three characteristic wetting regimes define the boiling behavior: hygrophilic surfaces having advancing and receding contact angles both under 90°; hygrophobic surfaces having both these dynamic contact angles over 90°;and ambiphilic surfaces having a receding contact angle less than 90°, but an advancing contact angle greater than 90°.The goal of this thesis is to experimentally characterize and compare the behavior of boiling surfaces in each of these regimes, observe the contact line behavior, and explain the mechanisms for their differences in performance.

[pt] A termografia por infravermelho (TIV) tem sido usada como ferramenta de avaliação não destrutiva para detectar falhas em componentes estruturais, desempenhando um papel importante nos programas de inspeção, de fabricação e manutenção. A TIV também pode ser aplicada para avaliar limites de fadiga para materiais estruturais a partir de testes de tensão cíclica uniaxial ou de tração uniaxial quase-estáticos. Recentemente, o método quase-estático para medir o limite de fadiga via TIV, foi estendido para estados de tensão biaxial atuando na superfície de corpos de prova de tamanho real de dutos com anomalias geométricas. Os resultados mostraram que o método biaxial quase-estático previu satisfatoriamente a localização de pontos críticos para a iniciação da fadiga em espécimes tubulares com mossas. Neste trabalho, as distribuições de tensões e deformações nos pontos críticos foram determinadas usando correlação de imagens digitais (DIC), aplicada a sete espécimes dog bone, padrão uniaxial, e oito espécimes de dutos de três metros de comprimento com tampas de cabeça plana fabricados a partir de tubos de aço API 5L Grau B. A determinação do estado de deformação superficial via DIC e a determinação das variações de temperatura correspondentes para os pontos do material de superfície observados ao longo dos testes, permitiram determinar não apenas o limite de fadiga do material, mas também o que conveniou-se chamar de temperatura mínima característica (TMC). Os testes uniaxiais usando espécimes dog bone para o mesmo material indicam que as TMCs medidas estão intimamente relacionadas com o limite de escoamento do material (MYS). Esta pesquisa destaca as observações experimentais relacionadas às medidas de tensão-deformação-temperatura no início do escoamento em pontos observados em ensaios uniaxiais e biaxiais. O objetivo deste trabalho é usar o monitoramento da temperatura de estruturas sob carga crescente quase-estática para prever a que distância do início do MYS estão os estados de tensão dos pontos observados. / [en] Infrared thermography (IRT) has been applied in several areas of science. Particularly in the field of engineering, which has proven to be an excellent tool in non-destructive evaluations of structural components. In addition, IRT has also been applied to assess fatigue limits for structural materials from uniaxial cyclic stress tests or quasi-static uniaxial tensile tests. Recently, the quasi-static method to measure the fatigue limit via IRT was extended to biaxial stress states acting on the surface of real size pipeline specimens with dents. The results showed that the quasi-static biaxial method satisfactorily predicted the location of the hot spots for fatigue initiation in tubular specimens with dents. In this dissertation, the strain distributions at the critical points were determined from mechanical test using digital image correlation (DIC) applied to seven uniaxial standard dog bone and eight 3-meter-long pipeline specimens with plane headed caps fabricated from API 5L Grade B steel. The determination of the deformation state via DIC and the corresponding temperature variations for observed points on the material surface allowed to determine not only the material endurance limit, but also what may be called as the characteristic minimum temperature (TMC). Uniaxial tests using dog bone specimens for the same material indicate that the measured TMC are closely related to the material yield strength (MYS). This work brings originality in the definition and determination of the TMC point. In uniaxial tests the TMC point is determined through the temperature-strain-stress curves, while in biaxial tests, it is located in the temperature-pressure-strain curves.

<p dir="ltr">Transportation and energy production industries strongly rely on improvements in gas turbine performance. The quantification of these improvements is dependent on the accuracy of the measurements performed during testing. An increase of 0.5\% in efficiency is sufficient to secure a new development program worth millions of dollars, but in the case of temperature measurements, uncertainties below 0.5 K are required, which presents a challenge. This work selects heat flux estimation and total temperature measurement uncertainties as major contributors for efficiency uncertainty.</p><ul><li>Heat flux measurements are critical to evaluate the impact on the efficiency. Additionally, thermal fatigue in turbine airfoils defines the life cycle of the engine core. This work performs an estimation of the heat transfer via a simplified numerical model that uses infrared (IR) measurements in the surface of the casing to predict the temperature of the passage wall. The model is validated with real cool-down data of the turbine to yield results within a 10\% of the actual temperature.</li><li>Total temperature measurement suffers from errors due to heat transfer effects in the probe. Two dominant sources of errors are convection and conduction between the thermocouple wires, the probe support, and the flow. These effects can be treated in two different categories: the velocity error, created by a non-isentropic reduction of the flow velocity upstream the thermocouple junction, and the thermal equilibrium effects between the junction and the probe support, involving heat transfer through the wire to the shield and the probe stem due to temperature differences between each component (the so-called \emph{conduction error}). An open jet stand is used to evaluate the effects of velocity error at various Mach numbers. The conduction error is addressed with the design and manufacturing of dual-wire thermocouple probes. The readings from two wires with different length-to-diameter ratios are used to correct for the flow total temperature. This probe yielded a recovery factor of 0.99 +/- 0.01 at Mach 0.6.</li></ul><p></p>

[ES] A medida que aumenta la conciencia climática y se buscan reducir las emisiones globales, se están realizando esfuerzos para producir tecnologías que permitan desarrollar motores más limpios y amigables con el medio ambiente. Los sistemas GDI (inyección directa de gasolina) tienen el potencial de cumplir con los cada vez más estrictos estándares de emisiones y, al mismo tiempo, mejorar el consumo de combustible. El espacio limitado dentro de la cámara de combustión hace que el impacto del chorro con la pared sea un fenómeno común en los motores de inyección directa de gasolina. Este fenómeno tiene un efecto significativo en el desarrollo del chorro y su interacción con el aire en la cámara. En condiciones de arranque en frío, las bajas presiones y temperaturas en la cámara facilitan la deposición del combustible en la superficie del pistón, lo que conduce a un aumento considerable en la formación de hollín y en los hidrocarburos sin quemar. Esta tesis busca proporcionar información sobre las características más relevantes de la interacción chorro-pared en sistemas de inyección directa de gasolina en condiciones de arranque en frío y otras condiciones evaporativas. Para ello, se utilizó una pared plana ubicada a diferentes distancias de impacto y ángulos con respecto a la punta del inyector. Se empleó un inyector solenoide fabricado por Continental y el inyector "Spray G", utilizando iso-octano como combustible inyectado. El estudio se llevó a cabo en diversas instalaciones experimentales cubriendo varias técnicas ópticas. El estudio de la interacción chorro-pared se llevó a cabo utilizando tres campañas experimentales. En la primera, se utilizó una pared de cuarzo transparente para analizar las características macroscópicas del chorro al impactar la pared, observándola lateral y frontalmente con el uso de tres cámaras de alta velocidad gracias a los accesos ópticos de la instalación experimental. En la segunda, se empleó una pared termorregulada de acero inoxidable para medir el efecto que tienen las condiciones de operación y ambientales sobre la transferencia de calor entre la pared y el chorro durante el evento de inyección de combustible. Se observó que la penetración del chorro libre y el desarrollo del chorro sobre la pared son influenciados por la presión de inyección y el ángulo de inclinación de la pared. El ancho del chorro medido después del impacto fue afectado principalmente por la distancia entre el inyector y la pared y por el ángulo de la pared pero más aún por la distancia respecto al punto de impacto sobre la cual fue medida. La semi área de impacto es susceptible a cambios en el ángulo de la pared y la distancia inyector-pared teniendo un papel fundamental en el arrastre de aire entre el chorro y el ambiente. No se encontraron diferencias significativas entre las fases líquida y vapor tanto para la penetración de chorro libre como para el desarrollo del chorro sobre la pared a temperatura ambiente. Por el contrario, con la pared calentada, se obtuvieron diferencias entre la fase líquida y vapor, destacando la contribución de la evaporación de combustible causada por el incremento en la temperatura de la pared. Respecto a la pared instrumentada, tanto la temperatura del combustible como de la pared produjeron los picos más significativos en términos del flujo de calor superficial. Órdenes de magnitud similares respecto al flujo de calor superficial fueron encontrados entre las campañas experimentales de la pared instrumentada y la termografía infrarroja. La aparición del flash boiling en condiciones de menor contrapresión ambiental y mayor temperatura del combustible modificó la morfología del chorro en términos de anchura , lo que tuvo repercusiones significativas en el parámetro R (que depende de la penetración del chorro) y en el número de gotas de líquido presentes en el chorro, afectando tanto a los perfiles de extinción de la luz como a los perfiles del flujo de calor superficial. / [CA] A mesura que augmenta la consciència climàtica i es busquen reduir les emissions globals, s'estan fent esforços per a produir tecnologies que permeten desenvolupar motors més nets i amigables amb el medi ambient. Els sistemes GDI (injecció directa de gasolina) tenen el potencial de complir amb els estrictes estàndards d'emissions i, al mateix temps, millorar el consum de combustible. L'espai limitat dins de la cambra de combustió fa que l'impacte del doll amb la paret siga un fenomen comú en els motors d'injecció directa de gasolina. Aquest fenomen té un efecte significatiu en el desenvolupament del doll i la seua interacció amb l'aire en la cambra. La interacció doll-paret és un fenomen interessant i difícil de comprendre que ocorre durant el procés de combustió. En condicions d'arrancada en fred, les baixes pressions i temperatures en la cambra faciliten la deposició del combustible en la superfície del pistó, la qual cosa condueix a un augment considerable en la formació de sutge i en els hidrocarburs sense cremar. Aquesta tesi busca proporcionar informació sobre les característiques més rellevants de la interacció doll-paret en sistemes d'injecció directa de gasolina en condicions d'arrancada en fred i altres condicions evaporatives. Per a això, es va utilitzar una paret plana situada a diferents distàncies d'impacte i angles respecte a la punta de l'injector. Es va emprar un injector solenoide fabricat per Continental i l'injector "Spray G", utilitzant iso-octà com a combustible injectat. L'estudi es va dur a terme en diverses instal·lacions experimentals cobrint diverses tècniques òptiques. L'estudi de la interacció doll-paret es va dur a terme utilitzant tres campanyes experimentals. En la primera, es va utilitzar una paret de quars transparent per a analitzar les característiques macroscòpiques del doll en impactar la paret, observant-la lateral i frontalment amb l'ús de tres càmeres d'alta velocitat gràcies als accessos òptics de la instal·lació experimental. En la segona, es va emprar una paret termorregulada d'acer inoxidable per a mesurar l'efecte que tenen les condicions d'operació i ambientals sobre la transferència de calor entre la paret i el doll durant l'esdeveniment d'injecció de combustible. Es va observar que la penetració del doll lliure i el desenvolupament del doll sobre la paret són influenciats per la pressió d'injecció i l'angle d'inclinació de la paret. L'ample del doll mesurat després de l'impacte va ser afectat principalment per la distància entre l'injector i la paret i per l'angle de la paret però més encara per la distància respecte al punt d'impacte sobre la qual va ser mesurada. La semi àrea d'impacte és susceptible a canvis en l'angle de la paret i la distancia injector-paret tenint un paper fonamental en l'arrossegament d'aire entre el doll i l'ambient. No es van trobar diferències significatives entre les fases líquida i vapor tant per a la penetració de doll lliure com per al desenvolupament del doll sobre la paret a temperatura ambient. Per contra, amb la paret calfada, es van obtindre diferències entre la fase líquida i vapor, destacant la contribució de l'evaporació de combustible causada per l'increment en la temperatura de la paret. Respecte a la paret instrumentada, tant la temperatura del combustible com de la paret van produir els pics més significatius en termes del flux de calor superficial. Ordres de magnitud similars respecte al flux de calor superficial van ser trobats entre les campanyes experimentals de la paret instrumentada i la termografia infraroja. L'aparició del flaix boiling en condicions de menor contrapressió ambiental i major temperatura del combustible va modificar la morfologia del doll en termes d'amplària, la qual cosa va tindre repercussions significatives en el paràmetre R i en el nombre de gotes de líquid presents en el doll, afectant tant els perfils d'extinció de la llum com als perfils del flux de calor superfial. / [EN] Fuel injection is one of the most important factor that must be considered to achieve cleaner and more efficient internal combustion engines. Its role is more evident when direct injection strategies are used. As awareness of climate change and global emission reduction policies increase, efforts are being made to develop new technologies that enable cleaner and more environmentally friendly engines. The gasoline direct injection systems can fulfill strict emission standards and improve fuel consumption. Because of the space constraints inside the combustion chamber for spray penetration, collision and interaction with the wall are common events in direct injection engines, considerably influencing spray formation and air-spray interaction inside the chamber. In cold-start engine conditions, the lower injection pressures and temperatures in the combustion chamber enhance the fuel deposition over the piston surface, incrementing the soot and the unburned hydrocarbon formation. The present work highlights the fundamental aspects of the spray-wall interaction for the gasoline direct injection (GDI) system under cold-start and other evaporative conditions. For that, a flat wall is located several distances and at different wall angles to the injector tip. Also, this thesis involves using a solenoid injector produced by Continental and the well-known "Spray G" injector using iso-octane as injected fuel covering several techniques and experimental facilities. To analyze the spray-wall interaction, three experimental approaches were used: The first used three high-speed cameras and a quartz wall inside the test rig vessel to study the macroscopic characteristics of the spray, which was observed lateral and frontal by using the optical accesses of the vessel. The second approach used a stainless steel wall to catch the effect of the operating and ambient conditions over the heat flux between the wall and the spray during the fuel injection event and determine how the spray development is affected by the cold-start realistic engine conditions and other evaporative conditions that were included in the test matrix. This wall was coupled with sensors to control the initial surface temperature and to compute the temperature variation in time and the surface heat flux using high-speed thermocouples. The spray under free-jet conditions was also analyzed as a comparison point with the spray-wall interaction conditions. The free spray penetration and the spray spreading over the wall were influenced mainly by the injection pressure and the wall angle. The spray thickness measured after the SWI was affected primarily by the wall-to-tip distance and the wall angle but even more by the distance from the impact point in which it is measured. The semi-circle impact area was susceptible to wall angles and wall-to-tip distance variations, essential in the spray-air entrainment. No remarkable differences were found between the liquid and vapor phases for the free jet or the isothermal wall configuration. In contrast, some differences were obtained for the instrumented and thermoregulated wall, remarking the contribution of fuel evaporation caused by the wall temperature increase. Regarding the thermoregulated wall, the fuel and wall temperatures produced the most important peaks in terms of surface heat flux. A similar order of magnitude regarding the surface heat flux was found between the thermoregulated wall and infrared thermography experimental campaigns. The flash boiling appearance for the lower ambient back pressure and higher fuel temperature condition changed the spray morphology in terms of the width (spray angle), having significant repercussions over the R-parameter (which depends on the spray penetration) and in the number of liquid droplets present in the spray affecting both the light extinction profiles and the surface heat flux profiles. / Esta tesis se ha desarrollado en el marco de una ayuda para la Formación de Personal Investigador (FPI) Subprograma 1 (PAID-01-19) financiada por la Universitat Politècnica de València. / Carvallo García, CL. (2023). Experimental study of the behavior of gasoline direct injection GDI sprays during wall impingement under realistic engine conditions [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/195027

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