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Injection of gas–liquid sprays into gas–solid fluidized beds finds application in many industries. Effective mixing and distribution of liquid feed and solid bed material is paramount to ensure an efficient and profitable process. Despite its long-term use, the mechanism of liquid injection into gas–solid fluidized beds continues to raise questions and is only partially understood. This paper provides a thorough and up-to-date review of experimental and numerical investigations of gas–liquid sprays into gas–solid fluidized beds conducted over the past decades. Based on the surveyed literature, a phenomenological description of the prevalent mechanisms of gas–liquid injection under different operating conditions is presented. This review identifies suitable computational fluid dynamic models for simulating the mechanisms involved in gas–liquid–solid interactions along with recommendations for future numerical and experimental work.

ヒドラジンに替わる低毒性推進剤の開発のため，HAN (Hydroxyl Ammonium Nitrate)またはADN(Ammonium Dinitramide)を基剤とした高エネルギー液体に着目し研究を行った．これらの液体を推進剤として実用化するためには燃焼効率の向上が求められるため，渦巻噴射弁を用いた微粒化により反応性を向上させることを目的とした．従来得られていた知見より，これらの高エネルギー液体は粘性が高く微粒化は難しいとされている．そこで本研究では，粘度および表面張力を実測し，1-10N クラスのスラスタを想定した条件での噴射実験を行った．さらに，結果を種々の無次元数で整理することによって，低毒性推進剤の微粒化に求められる条件を検討した．, To replace hydrazine, which is a deadly toxic monopropellant for RCS (Reaction control system), research on green propellants is vitalized in the world, and green propellant-based HAN (Hydroxyl Ammonium Nitrate) or ADN (Ammonium Dinitramide) is considered to be promising candidates. Since the improvement of combustion characteristics is strongly required to achieve the practical use of green propellant, we focused on the atomization of green propellant by a swirl injector. According to the previous study, it was found that green propellant candidates are hard to be atomized because of the highly viscous liquid. In this study, we measured the viscosity and surface tension of green propellant candidates to derive the Reynolds number, Weber number, and Ohnesorge number, which are important to characterize the atomization state. We also conducted injection tests under the condition assuming 1-10 N class RCS, to acquire the state of injection flow and to inspect atomization characteristics of energetic ionic liquid. Then, we discussed suitable physical properties such as viscosity and surface tension by using dimensionless numbers to propose promising green propellants., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA2230017006, レポート番号: JAXA-RR-22-006

Переход садоводства на интенсивный путь развития требует непрерывного совершенствования и углубления отраслевой и межотраслевой специализации, разработки инновационных технологий и технических средств механизации основных технологических процессов. В технологическом процессе возделывания плодовых насаждений особая роль отводится химическим методам борьбы с вредителями и болезнями, которая реализуется применением различных опрыскивателей. Для получения высококачественной плодовой продукции в настоящее время применяют значительный объем химических средств защиты в связи с тем, что проводятся 30 и более опрыскиваний за один вегетационный период. Некачественное распыливание средств защиты плодовых насаждений приводит к загрязнению окружающей среды. Таким образом, качественная оценка технологических и технических характеристик опрыскивателей является актуальной проблемой. В связи с этим, предложенные в данной статье метрологическое и методическое обеспечение позволят получить достоверную информацию о технологических и технических характеристиках распылителей опрыскивателей для обоснования их эффективности и экологичности., Transition of horticulture to the intensive way of development requires continuous improvement and deepening of branch and inter-branch specialization, development of innovative technologies and technical means of mechanization of the main technological processes. In the technological process of fruit plantations cultivation, a special role is given to chemical methods of pest and disease control, which is implemented by using various sprayers. In order to obtain high quality fruit production, a considerable amount of chemical means of protection is currently used due to the fact that 30 and more sprayings are carried out during one vegetation period. Poor quality spraying of fruit plantation protection products leads to environmental pollution. Thus, a qualitative evaluation of technological and technical characteristics of sprayers is an actual problem. In this regard, the metrological and methodological support proposed in this article will allow to obtain reliable information on technological and technical characteristics of sprayers' atomizers to substantiate their efficiency and eco-friendliness., Международный научно-исследовательский журнал, Выпуск 7 (133) 2023

Due to current and future environmental and safety issues in space propulsion, typical propellants for upper stage or satellite rocket engines such as the toxic hydrazine are going to be replaced by green propellants like the combination of liquid oxygen and hydrogen or methane. The injection of that kind of cryogenic fluids into the vacuum atmosphere of space leads to a superheated state, which results in a sudden and eruptive atomization due to flash boiling. For a detailed experimental investigation of superheated cryogenic fluids, the new cryogenic test bench M3.3 with a temperature controlled injection system was built at DLR Lampoldshausen. After a first test campaign with high-speed shadowgraphy of flash boiling liquid nitrogen sprays, a laser-based Phase Doppler system was set-up to determine the spatial distributions of droplet velocities and diameters in highly superheated sprays. The spatial distributions revealed a core region with high mean velocities close to the injector orifice. With increasing distance from the injector orifice, the sprays develop a more and more monodisperse pattern. These distributions also showed that atomization due to flash boiling generates finer sprays with growing degrees of superheat. In certain spray regions, two droplet populations varying in their direction of motion, velocity and diameter due to possible recirculation zones were observed. The experimental data of flash boiling liquid nitrogen generated within this study provide a comprehensive data base for the validation of numerical models and further numerical investigations., Deutsche Forschungsgemeinschaft, Projekt DEAL

International audience; Assessment of geometry effects affecting shock-induced cavitation within a droplet is investigated for the first time. To do this, we use a thermodynamically well-posed multiphase numerical model accounting for phase compression and expansion, which relies on a finite pressure-relaxation rate formulation and which allow for heterogeneous nucleation. These geometry effects include the shape of the transmitted wave front, which is related to the shock speed to droplet sound speed ratio, and the droplet geometry (cylindrical versus spherical). Phenomenological differences between the column and the droplet configurations are presented. In addition, the critical Mach number for cavitation appearance is determined for both cases: between M = 1.8 and M = 2 for the column, and between M = 2 and M = 2.2 for the droplet. Based on the transmitted wavefront geometry, with Mach number varying from 1.6 to 6, two cavitation regimes have been identified and the transition has been characterised: an exponentially (M < 4.38) and a linearly (M > 4.38) increasing bubble-cloud volume. On more applied aspects, we also investigate the influence of the bubble cloud on the interface disruption and compare the results against the pure liquid droplet test case. A parallel with the technique of effervescent atomization is eventually presented.

The transition from arithmetic to algebra requires students to change both their thinking and the way they learn. We often observe students using arithmetic formalism also when solving algebraic problems. This formalism manifests itself primarily in the acquisition of coherent computational procedures. Students must be sufficiently aware that the computation steps are sequential transformations of the problem. This creates a problem for them in solving more complex problems. Our research investigated whether problem transformation coupled with atomization is a suitable alternative for students to learn coherent algorithms. Although atomization is not based on precise rules, it was reported by students to be a comprehensible way of solving problems and providing them with sufficient confidence. If students are motivated to understand a computational method, this understanding represents fulfilling the student’s need for security.

International audience; Numerical modeling of high-pressure liquid fuel injection remains a challenge in various applications. Indeed, experimental observations have shown that injected liquid fuel jet undergoes a continuous change of state from classical two-phase atomization and spray droplets evaporation to a dense-fluid mixing phenomenon depending on the ambient pressure, temperature, and fuel properties. Accordingly, a predictive and efficient computational fluid dynamics (CFD) model that can represent the possible coexistence of subcritical and supercritical regimes during the fuel injection event is required. The widely used Lagrangian Discrete Droplet Method (DDM) requires parameter tuning of model constants and cannot model the dense near-nozzle region. Meanwhile, the high computational cost of Interface Capturing Methods (ICM) has prohibited their application to industrial cases. Thus, another alternative is an Eulerian Diffuse Interface Model (DIM), where the unresolved interface features are modeled instead of being tracked. Accordingly, the current work proposes a fully compressible multi-component two-phase real-fluid model (RFM) with a diffused interface and closed by a thermodynamic equilibrium tabulation method based on a real-fluid equation of state. The RFM model is complemented with a postulated surface density equation for fuel atomization modeling within the Large Eddy Simulation (LES) framework. The Engine Combustion Network (ECN) Spray A injector non-evaporating and nominal evaporating conditions are used as a reference for the proposed model validation. Simulations are performed using the proposed RFM model that has been implemented in the CONVERGE CFD solver. Under the non-evaporating condition, the RFM model can capture well the fuel mass distribution in the near-nozzle field, but also the interfacial surface area. Besides, the predicted drop size from simulations falls within the experimental data range. On the other hand, under the evaporating condition, spray liquid and vapor penetrations and fuel mixture fraction distribution are also accurately predicted. The vaporization effect on the surface area density is revealed to enhance surface generation in the dense spray region while reducing the surface density in the dilute spray region. The mean droplet size is also relatively reduced under the evaporating condition in the diluted spray region. Overall, the accuracy and computationally efficiency of the proposed RFM model coupled with the surface density equation for high-pressure fuel injection modeling are confirmed, allowing its use for high pressure industrial configurations in future studies.

It is important to improve the thermal efficiency and reduce the harmful exhaust emissions of the direct-injection spark-ignition engine. However, this engine has problems such as the emission of particulate matter, including soot, from pool fire with luminous flames. Pool fire is caused by the thermal decomposition of a liquid film, which is created by fuel spray impinging on a piston surface. An understanding of liquid film formation process is important to reduce particulate matter. The purpose of this investigation was to evaluate the effects of injection pressure on fuel spray impingement and liquid film formation process, under engine motoring conditions, using the laser-induced fluorescence method. The fuel consisted of isooctane, 1-octanol and rhodamine B. 1-Octanol was the solvent for rhodamine B, which was illuminated with a neodymium-doped yttrium aluminum garnet laser, causing it to emit red fluorescence at a wavelength of 580 nm; the second harmonic of the laser is at 532 nm. Liquid film images were captured using a high-speed camera. Using image processing, the liquid film area, thickness and mass were estimated. It was found that increasing injection pressure increased the liquid film area, thinned the film and decreased the mass of fuel that remained. In total, 35.6% and 32.5% of the injection mass remained on the piston surface at an injection pressure of 5 and 13 MPa, respectively. In addition, the in-cylinder flow affected the liquid film formation process, stretching the film in the direction of the flow.

形態: カラー図版あり, Physical characteristics: Original contains color illustrations, Accepted: 2022-01-14, 資料番号: PA2220037000

Icing on aircraft wings is one of the leading causes of aircraft crashes. It is mainly caused due to accumulation of ice or snow on the wing surface due to impact with supercooled droplets when passing through clouds at high altitudes, causing loss of lift obtained by the wings. It was found that droplet impact characteristics are dependent on droplet size, surface roughness, surface material hydrophobicity, and droplet impact velocity. As a continuation of the study of droplet impact contact characteristics by varying surface roughness and impact velocity, this study focuses on droplets impacting the vibrating surface at frequencies between 2-7 kHz. Atomization (water drop splitting into smaller droplets and ejecting from the surface) has been observed at different rates for all frequencies. The first set of data is collected by keeping roughness constant and increasing the amplitude of the vibration to observe the critical amplitude at which atomization is initiated. The surface roughness is varied for the second set of experiments. The data is quantified using image processing of the high-speed videos to obtain the rate of ejection for each case. Master of Science Icing on aircraft wings is among the leading causes of crashes, which involves small freezing water drops sticking to the wing surface thus reducing the lift. This study is an investigation to experimentally observe how small water droplets interact with surfaces vibrating at high frequencies when impacted. Surface roughness, materials, droplet velocities, and frequency of vibration have been varied and the droplet was captured using high-speed photography to study their effect on the aforementioned interaction. Glass, PET-G. and aluminum having specific roughness were fabricated using laser and chemical etching. Atomization (water drop splitting into smaller droplets and ejecting from the surface) has been observed at different rates for all frequencies. A relation between the amplitude of the vibration and the rate of atomization was found. The effect of varying frequencies and surface roughness has also been documented.

Cold gas dynamic spray (CS) is a unique technique for depositing material using high-strain-rate solid-state deformation. A major challenge for this technique is its dependence on the powder’s properties, and another is the lack of standards for assessing them between lots and manufacturers. The motivation of this research was to understand the variability in powder atomization techniques for stainless steel powders and their subsequent properties for their corresponding impacts on CS. A drastic difference (~30%) was observed in the deposition efficiencies (DEs) of unaltered, spherical and similar sized stainless steel (316) powders produced using centrifugal (C.A) and traditional gas atomization (G.A) techniques. The study highlights more the differences on a precursor level. Using recent advancements in large scale statistical measurements, such as laser diffraction shape analysis and µCT scanning; and traditional methods, such as EBSD and nanoindentation, an attempt was made to understand the powder’s properties. Insights on powder size and shape were documented. Significant differences were observed between C.A and G.A powders in terms of grain size, fraction of high-angle grain boundaries (HAGBs) and nanohardness. The outcomes of this study should be helpful for understanding the commercialization of the cold-spray process for bulk manufacturing of powder precursors.

In the last decade, alginate-based microgels have gained relevant interest as three-dimensional analogues of extracellular matrix, being able to support cell growth and functions. In this study, core-shell microgels were fabricated by self-polymerization of dopamine (DA) molecules under mild oxidation and in situ precipitation of polydopamine (PDA) onto alginate microbeads, processed by electro fluid dynamic atomization. Morphological (optical, SEM) and chemical analyses (ATR-FTIR, XPS) confirmed the presence of PDA macromolecules, distributed onto the microgel surface. Nanoindentation tests also indicated that the PDA coating can influence the biomechanical properties of the microgel surfaces—i.e., σmaxALG = 0.45 mN vs. σmaxALG@PDA = 0.30 mN—thus improving the interface with hMSCs as confirmed by in vitro tests; in particular, protein adsorption and viability tests show a significant increase in adhesion and cell proliferation, strictly related to the presence of PDA. Hence, we concluded that PDA coating contributes to the formation of a friendly interface able to efficiently support cells’ activities. In this perspective, core-shell microgels may be suggested as a novel symmetric 3D model to study in vitro cell interactions.

Design of atomizers for gas-turbine purposes are an important ordeal. The per-formance of the atomizer directly impacts the efficiency of the gas-turbine, andconsequently, the energy extracted from the turbine. Furthermore, the design ofthe atomizer can have an impact on reducing toxic emissions. On a global scale,gas-turbines can be considered crucial for the transition to renewable energy. Forengineers, designing of atomizers are however challenging. Turbulent flow, multi-phase interaction and chemical reactions are some of the complex physics involvedwhich has to be taken into consideration when designing the atomizer. Engineerstraditionally uses experimental testing for investigation of designs, and it is still verymuch a useful methodology. However, numerical simulations and CFD have recentlygained popularity due to being a more cost-effective methodology. In this work, theprocedure for designing a prefilm atomizer involving CFD (single phase model andmulti phase model) and experimental testing is documented. The details of the twonumerical models (a single phase model and a multi phase model) has been doc-umented as well as the experimental setup. The single phase model is used for aparametric study and experimental testing is used for evaluation of designs. Themulti phase model is aimed to replicate the experimental results. The validity ofthe numerical models and the experimental setup are discussed, and possible mod-ifications of the methodology for future studies are suggested. Finally, suggestionsfor how the prefilmer should be designed is suggested.

International audience; This work focuses on the study of sprays generated through a bifluid nozzle and the modelling of characteristic spray properties (two characteristic diameters and a polydispersity index) using dimensional analysis. Two types of dimensionless models were identified for each spray target property from the 75 experimental points considered. The first type used a conventional monomial-exponential shape equation, and the second applied shape identification through machine-learning. Although conventional models of the first type were mostly satisfactory when considering the characteristic diameters, they nevertheless showed clear limitations addressed by the machine-learning identified models. The conventional approach also failed to identify a satisfactory equation for the polydispersity index. The machine-learning approach provided an equation identifying this index to the main dimensionless parameters governing atomization. This identification provides a foundation for proposing a two-parameters dimensionless model that predicts spray particle size distribution. The combination of dimensional analysis with machine-learning equation identification thus paves the way to physically rigorous and easy-to-use models capable of predicting characteristic properties and full distributions.

Cracking of sugars to glycolaldehyde and other value-added oxygenates has shown potential in lab-scale fluidized beds with high yield and selectivity towards glycolaldehyde. In this work, a homogeneous gas-phase kinetics model for sugar cracking available in literature is adopted and implemented into the Computational Particle Fluid Dynamics (CPFD) framework in order to simulate sugar cracking in a pilot-scale circulating fluidized bed riser operated at conditions relevant for continuous production of glycolaldehyde in the industry. An Eulerian-Lagrangian approach is applied to model the three-phase flow where liquid feed droplets are injected into the hot gas-solid fluidized bed. A modified gas-to-liquid ratio dependent Rosin-Rammler droplet size distribution is proposed to accurately represent the gas-liquid jet in the simulation. Simulated temperature and pressure distributions are in good agreement with measured ones. Prediction of the yield of glycolaldehyde at 60.9 wt.%-C and other oxygenates using the the CPFD model corresponds closely to the results obtained from the same kinetic model implemented in an isothermal plug flow reactor model. This suggests that the CFB riser behaves essentially like a plug flow reactor, as hydrodynamic and thermal deviations from plug flow conditions do not have a considerable effect on the predicted yields. Comparing the model predictions to the measured yield of glycolaldehyde, a 50% overprediction is observed, suggesting that the hydrodynamic and cracking kinetics submodels need to be more closely coupled to more accurately predict the product yields, by means of e.g. heterogeneous cracking reactions.

International audience; Atomization processes are used to produce uranium-based powders for the manufacturing of dispersion fuel for nuclear research reactors. Whereas this process is considered worldwide as a reference for U-Mo powder production, its use for U 3 Si 2 is still limited. In this paper, the microstructure of as-atomized nearly stoichiometric (7.4 wt% Si) and hyperstoichiometric (7.6 and 7.8 wt% Si) U 3 Si 2 powders is studied in detail. A wide range of analytical techniques were applied: X-ray diffraction (XRD), scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM), electron backscattered diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDS) at both micrometer (SEM) and nanometer (STEM) scales. These analyses lead to an original description of the microstructure of these as-atomized U 3 Si 2 particles. It is shown that most of atomized particles contain only a few U 3 Si 2 grains, some being even monocrystalline. The main secondary phase present in hyper-stoichiometric batches is an U 20 Si 16 C 3like phase. Other minor phases are also encountered, some of them containing metallic impurity elements. These features are attributed to the uranium raw material composition and to a slight contamination by carbon during the powder synthesis. The nature and morphology of secondary phases present in U 3 Si 2 atomized particles appear thus to be linked not only to the silicon excess but also to the presence of impurities which probably strongly segregate during the very fast solidification of the alloy droplets. A slight superficial oxidation of particles also occurs and induces a local redistribution of silicon.

Oral inhalation of aerosolized drugs has be widely applied in healing the affected body organs including lesions of the throat and lungs and it is more efficient than those conventional therapies, such as intravenous drip, intramuscular injection and external topical administration in the aspects of the dosage reduction and side effects of drugs. Nevertheless, the traditional atomization devices always exhibit many drawbacks. For example, non-uniformed atomization particle distribution, the instability of transient atomization quantity and difficulties in precise energy control would seriously restrict an extensive use of atomization inhalation therapy. In this study, the principle of intra-hole fluctuation phenomenon occurred in the hole is fully explained, and the produced volume change is also estimated. Additionally, the mathematical expression of the atomization rate of the atomizing device is well established. The mechanism of the micro-pump is further clarified, and the influence of the vibration characteristics of the atomizing film on the atomization behavior is analyzed theoretically. The curves of sweep frequency against the velocity and amplitude of the piezoelectric vibrator are obtained by the Doppler laser vibrometer, and the corresponding mode shapes of the resonance point are achieved. The influence of vibration characteristics on atomization rate, atomization height and atomization particle size are also verified by experiments, respectively. Both the experimental results and theoretical calculation are expected to provide a guidance for the design of this kind of atomization device in the future.

In this study, a two-fluid nozzle, as, e.g., used in fluidized-bed or spray drying applications, is comprehensively characterized regarding the spray pattern and droplet size. To analyze the spray cone, the spray cone angle and the radial mass distribution of the nozzle were measured at varied liquid flow rate, spray air pressure, liquid insert bore diameter, and air cap position. Additionally, droplet size distributions were recorded at different spray settings. In general, the overall spray cone and single droplets are significantly influenced by the spray parameters, especially the spray air pressure, as well as the nozzle geometry.

Dry fog is a specific form of aerosol that is used in many branches of industry and many aspects of everyday life. It can be used, inter alia, to disinfect rooms or to control the level of humidity. One of its greatest advantages is undoubtedly its ability to work in the vicinity of electrical devices. Although the process of its formation and the very phenomenon of its occurrence are extremely simple things to describe, there are still many aspects that can be discovered, which are the focus of research by scientists around the world. One of the main parameters that influence the production process of dry fog is the pressure of the supplied gas, as well as the environmental conditions in which the aerosol is formed. This work focuses on the production of dry fog with the use of the designed and constructed apparatus, the structure of which is based on a jet nebulizer. The test and measurement stand is equipped with a compressor with a built-in pressure gauge for reading air pressure, a valve that allows the flow to be regulated, and an air supply and heating device that operates at various power values. The aim of this research was to check the impact of the power that is supplied to the system, as well as the impact of changing selected parameters such as gas pressure (which is one of the required media), on the liquid spraying process. The analysis of the results obtained during the experimental tests was based on the photographic method and allowed the mean Sauter volume–surface diameters of the obtained droplets to be compared. The analysis also showed that an increase in the power of the air supply and heating device translates directly into an increase in the ambient temperature in which the dry fog is formed, and contributes to the reduction of the diameter of the generated droplets. Changing the pressure of the atomized gas has a direct impact on the size of droplets in the generated aerosol—the higher the pressure, the smaller the droplets.

Rotating jets are ubiquitous in agricultural irrigation. They can be observed at the outletof micro-sprinklers with rotating deflectors. However, the atomisation mechanisms involvedin this type of sprayer are poorly studied and therefore not well understood. In agriculture,health risks and inefficiencies are encountered due to the dispersion of drops generated bythe atomisation of a liquid jet. The objective of this study is to develop, with an industrialpartner, a prototype of a micro-sprinkler limiting the phenomena of drift and runoff,which would use biocontrol products. In order to carry out this project, an experimentallaboratory set-up with a shadowgraphy method combined with DTV (Droplet TrackingVelocimetry) was developed to observe the fragmentation of a liquid jet with differentangular velocities. First, we observed the atomisation of a turbulent jet expelled by acircular nozzle with different angular velocities controlled by a motor. The stretching ofthe jet caused by the rotation results in a decrease of the thickness of the liquid core.At the same time, the aerodynamic forces linked to the resulting velocity of the jet, dueto its rotation, will favour the decrease of the average diameter of the drops. Secondly,an experiment was carried out on prototype micro-sprinklers whose angular velocity isintrinsically linked to the geometry of the deflector and the volume flow rate. The rapidmanufacture of prototypes with a 3D printer enabled us to carry out a parametric studyon 70 configurations. The morphology of the jet is studied with respect to the geometricalparameters for a prediction of the average diameter of the drops. A classification of theprimary atomisation regimes was carried out according to the aerodynamic Weber number.It is observed that the transition atomisation regime avoids the dispersion phenomenarelated to the droplet size distribution in the case of micro-sprinklers. Finally, a perspectiveof numerical simulation of a rotating jet is also discussed.; Les jets en rotation sont omniprésents dans le domaine de l’irrigation en agriculture. Onpeut les observer en sortie de micro-asperseurs avec des déflecteurs rotatifs. Pourtant lesmécanismes d’atomisation qui sont en jeu dans ce type d’atomiseur sont peu étudiés etpar conséquent méconnus. En agriculture, des risques sanitaires et des manquements àl’efficience sont rencontrés à cause de la dispersion des gouttes générées par l’atomisationd’un jet liquide. Cette étude a pour objectif le développement, avec un partenaire industriel,d’un prototype de micro-asperseur limitant les phénomènes de dérive et de ruissellement,qui utiliserait des produits de biocontrôle. Afin de mener à bien ce projet, une installationexpérimentale de laboratoire avec une méthode d’ombroscopie combinée avec la DTV(Droplet Tracking Velocimetry) a été élaborée pour observer la fragmentation d’un jetliquide avec différentes vitesses angulaires. En premier lieu, nous avons observé l’atomisationd’un jet turbulent expulsé par une buse circulaire avec différentes vitesses de rotationcontrôlées par un moteur. L’étirement du jet causé par la rotation provoque la diminutionde l’épaisseur du cœur liquide. Conjointement, les forces aérodynamiques liées à la vitesserésultante du jet, de part sa rotation, vont favoriser la diminution du diamètre moyendes gouttes. En second lieu, une expérimentation a été réalisée sur des prototypes demicro-asperseurs dont la vitesse de rotation est intrinsèquement liée à la géométrie dudéflecteur et au débit volumique. La fabrication rapide des prototypes avec une imprimante3D nous a permis de réaliser une étude paramétrique sur 70 configurations. La morphologiedu jet est étudiée en regard des paramètres géométriques pour une prédiction du diamètremoyen des gouttes. Une classification des régimes d’atomisation primaire a été réalisée enfonction du nombre de Weber aérodynamique. On observe que le régime d’atomisation detransition permet d’éviter les phénomènes de dispersion liés à la distribution de la tailledes gouttes dans le cas des micro-asperseurs. Finalement, une perspective de simulationnumérique d’un jet en rotation a aussi été abordée.

[ES] El presente TFM aborda la resolución del flujo interno y la atomización primaria de un inyector “pressure-swirl” de uso aeronáutico mediante un estudio computacional. El problema de estudio consiste en un flujo bifásico en el que coexisten una fase gaseosa formada por aire y una fase líquida correspondiente al combustible n-heptano. Por ello, el enfoque empleado en la resolución del problema es el método VOF de captura de la interfase. En particular, este trabajo se centra en evaluar el efecto de distintos algoritmos de reconstrucción de interfase con el fin de encontrar el óptimo para el caso de estudio. Con tal finalidad, se emplea el software open-source OpenFOAM®, en el que se llevan a cabo una serie de simulaciones LES con mallas con distinto nivel de refinamiento en la región externa, donde se desarrolla la película de combustible. También se va a implementar una herramienta de mallado adaptativo (AMR) que permita refinar aquellas regiones en las que se desee aumentar la precisión de los resultados, como en la interfase entre el aire y el n-heptano. Todo ello con la finalidad de captar los fenómenos que caracterizan la atomización primaria del combustible, es decir, las oscilaciones e inestabilidades en la lámina de combustible que provocan su disgregación en ligamentos y gotas. Para completar el post-procesado de los resultados se va a implementar un algoritmo de detección de gotas que permita obtener las funciones de densidad de probabilidad (PDF) de las mismas. Las PDF obtenidas se contrastarán con los resultados experimentales disponibles con el fin de validar el modelo CFD. Como punto final, este trabajo aborda un segundo análisis en el que se tratará de evaluar la influencia de la temperatura en el caso de estudio, para lo cual se comparan dos condiciones de operación, una a temperatura ambiente y otra con el combustible precalentado., [CA] El present TFM aborda la resolució del flux intern i l’atomització primària d’un injector “pressure-swirl” d’ús aeronàutic mitjançant un estudi computacional. El problema d’estudi consisteix en un flux bifàsic en el qual coexisteixen una fase gasosa formada per aire i una fase líquida corresponent al combustible n-heptà. Per això, l’enfocament emprat en la resolució del problema és el mètode VOF de captura de la interfase. En particular, aquest treball se centra en avaluar l’efecte de diferents algoritmes de reconstrucció d’interfase amb la finalitat de trobar l’òptim per al cas d’estudi. Amb tal propòsit, s’empra el software open-source OpenFOAM®, en el qual es duen a terme una sèrie de simulacions LES amb malles amb diferent nivell de refinament a la regió externa, on es desenvolupa la pel·lícula de combustible. També s’implementarà una tècnica avançada de mallat adaptatiu (AMR) que permeta refinar aquelles regions en les quals es desitge augmentar la precisió dels resultats, com en la interfase entre l’aire i el combustible. Tot això amb la finalitat de captar els fenòmens que caracteritzen l’atomització primària del combustible, és a dir, les oscil·lacions i inestabilitats en la làmina de combustible que provoquen la seua disgregació en lligaments i gotes. Per a completar el post-processat dels resultats s’implementarà un algoritme de detecció de gotes que permeta obtindre les funcions de densitat de probabilitat (PDF) d’aquestes. Les PDF obtingudes es contrastaran amb els resultats experimentals disponibles amb la finalitat de validar el model CFD. Com a punt final, aquest treball aborda un segon anàlisi en el qual es tractarà d’avaluar la influència de la temperatura en el cas d’estudi, per a això es comparen dues condicions d’operació, una a temperatura ambient i una altra amb el combustible precalfat., [EN] This Master´s Thesis deals with the resolution of the internal flow and the primary atomisation of an aeronautical pressure-swirl injector by means of a computational study. The case of study consists of a two-phase flow in which a gaseous phase formed by air and a liquid phase corresponding to the n-heptane fuel coexist. Therefore, the approach used to solve the problem is the VOF method of capturing the interface. In particular, this work focuses on evaluating the effect of different interface reconstruction algorithms in order to find the optimal one for the case of study. To this end, the open-source software OpenFOAM® is used, in which a series of LES simulations are carried out with meshes with different refinement levels in the outer region, where the fuel film is developed. An adaptive meshing tool (AMR) will also be implemented to refine those regions where it is desired to increase the accuracy of the results, such as at the interface between air and n-heptane. The aim is to capture the phenomena that characterise the primary atomisation of the fuel, i.e. the oscillations and instabilities in the fuel film that cause its break up into ligaments and droplets. To complete the post-processing of the results, a droplet detection algorithm will be implemented to obtain the probability density functions (PDF) of the droplets. The obtained PDF will be compared with the available experimental results in order to validate the CFD model. As a final point, this work deals with a second analysis in which the influence of temperature on the case of study will be evaluated, comparing two operating conditions, one at ambient temperature and the other one with preheated fuel.

Bu çalışmanın amacı, daldırma ve atomizasyon yöntemlerini kullanarak ısıl işlem görmüş ahşap malzemenin yapışma direnci performansını değerlendirmektir. Isıl işlem sıcaklığı, işlem süresi, ahşap yönü ve uygulama türleri bağımsız değişkenler, yapışma mukavemeti ise bağımlı değişken olarak belirlenmiştir. Isıl işlem görmüş ahşap malzemelere uygulanan yüzey kaplamasının performansını belirlemek için yapay yaşlandırma testi kullanılmıştır. Yapay yaşlandırma testi sonrası yüzey işlem performansını etkileyen faktörler, çok yönlü varyans analizi (MANOVA) ve pareto analizi ile değerlendirilmiştir. Elde edilen sonuçlara göre 190°C sıcaklıkta ve 2 saatlik uygulama süresinde her iki yöntemde de yapışma mukavemeti daha yüksek bulunmuştur. Radyal yöndeki yapışma mukavemetinin teğetsel yönden daha iyi olduğu görülmüş ve özellikle daldırma yönteminin malzeme yönü üzerinde önemli bir etkileşim oluşturduğu ve yapışma mukavemetini önemli ölçüde etkilediği gözlemlenmiştir., The aim of this study is to evaluate the heat treated wood coating performance using dipping and atomization methods. Heat treatment temperature, treatment time, wood direction and application types were selected as independent variables while adhesion strength was determined as a dependent variable. The artificial weathering test was used to determine the performance of the surface coating applied to the heat-treated wood materials. The factors affecting the surface coating performance after the artificial weathering test were evaluated by multivariate analysis of variance (MANOVA) and pareto analysis. According to results, adhesion strength was found to be higher in both methods at 190° C temperature and 2 hours of application time. Adhesion strength in the radial direction was found to be better than the tangential direction, and it was observed that especially the dipping method created a significant interaction on the material direction and affected the adhesion strength considerably.

Background Traditionally, nanoparticles for biomedical applications have been produced via the classical wet chemistry method, with size control remaining a major problem in drug delivery. In recent years, advances in aerosol-based technologies have led to the development of methods that enable the production of nanosized particles and have opened up new opportunities in the field of nano-drug delivery and biomedicine. Aerosol-based technologies have been constantly used to synthesize multifunctional nanoparticles with different properties, which extends their possible biological and medicinal applications. Moreover, aerosol technologies are often more beneficial than other existing approaches because of the major disadvantages of these other techniques. Area covered This review provides a brief discussion of the existing aerosol-based nanotechnologies and applications of nanoparticles in a variety of diseases. Various types of nanoparticles, such as graphene oxide, Prussian blue, black phosphorous, gold, copper, silver, tellurium, iron oxide, titania, magnesium oxide, and zinc oxide nanoparticles, prepared using aerosol technologies are discussed in this review. The different tactics used for surface modifications are also outlined. The biomedical applications of nanoparticles in chemotherapy, bacterial/fungal/viral treatment, disease diagnosis, and biological assays are also presented in this review. Expert opinion Aerosol-based technologies can be used to design nanoparticles with the desired functionality. This significantly benefits the nanomedicine field, particularly as product parameters are becoming more encompassing and exacting. One of the biggest issues with conventional methods is their scale-up/scale-down and clinical translation. Aerosol-based nanoparticle synthesis helps enhance control over the product properties and facilitate their use for clinical applications.

This work describes a post-processing scheme for multiphase flow systems to characterize primary atomization. The scheme relies on the 2D fast Fourier transform (FFT) to separate the inherently multi-scale features present in the flow results. Emphasis is put on the robust quantitative analysis enabled by this scheme, with this work specifically focusing on comparing atomizer nozzle designs. The generalized finite difference (GFD) method is used to simulate a high pressure gas injected into a viscous liquid stream. The proposed scheme is applied to time-averaged results exclusively. The scheme is used to evaluate both the surface and volume features of the fluid system. Due to the better recovery of small-scale features using the proposed scheme, the benefits of post-processing multiphase surface information rather than fluid volume information was shown. While the volume information lacks the fine-scale details of the surface information, the duality between interfaces and fluid volumes leads to similar trends related to the large-scale spatial structure recovered from both surface- and volume-based data sets.

近年，ヒドラジンを代替する低毒性一液推進剤候補としてアンモニウムジニトラミド（ADN）を基材としたイオン液体が注目を集めている．イオン液体はその高密度，高比推力，低毒性からヒドラジンに代わる一液推進剤として有望であるが，高粘度であるため微粒化が困難であり，点火特性や燃焼特性に課題があるため実用化には至っていない．本研究では，ADN系イオン液体に添加物を加えることで粘度を低下させ，微粒化特性を改善することを試み，性能低下を最低限に抑えつつ粘度を低下させられる添加物についての検討と，そのために必要な粘度測定実験およびCEA による化学平衡計算を行った．, In recent years, energetic ionic liquid based ammonium dinitramide (ADN) is drawing attention as green monopropellant alternate of hydrazine. Energetic ionic liquid is promising new monopropellant because it has high density, high specific impulse, and low toxicity. However, it is difficult to atomize due to its high viscosity. Therefore, it has ignition and combustion characteristics issue and not in practical use. In this study, we tried adding an additive to decrease viscosity of ADN-based energetic ionic liquid to improve its atomization characteristics. Viscosity measurement and chemical calculation by NASA CEA were performed to find suitable additive material for ADN-based green propellant. As a result, it is found that 20 wt% of methanol is suitable for additive because of viscosity, atomization characteristics, and exhaust characteristics velocity., 形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA2030016002, レポート番号: JAXA-RR-20-007

Crude oil is an attractive fuel for energy production, since its use does not require additional processing costs. Existing technologies for burning liquid fuel do not always ensure the achievement of the modern ecological and energy performance when using highly viscous and substandard fuels. This relates to unstable ignition and combustion of such fuels in the combustion chamber, relatively fast coking of the burner surfaces, etc. The work deals with investigation of crude oil burning in a flow of superheated steam as a promising way to reduce NOx and increase the completeness of fuel combustion. The experiments were carried out using an original burner where liquid fuel is sprayed due to interaction with a high-velocity flow of superheated steam. This method of spraying allows the creation of a highly dispersed two-phase flow and prevents nozzle chocking and coking when using sub-standard fuel and waste. At the same time, steam gasification of products of fuel thermal decomposition allows the reduction of toxic emissions, increasing carbon burnout. The regimes of crude oil burning in a modernized burner that provide high completeness of fuel combustion (~44 MJ/kg) with a low content of NOx and CO in the combustion products have been determined. The amount of these toxic components corresponds to class 1 of EN 267. The results obtained confirm the effectiveness of the investigated method of fuel spraying by a superheated steam jet for environmentally friendly crude oil burning, including this process in the low-power burners (~15 kW). Such devices can be used for the cleaner elimination of liquid hydrocarbon waste with the receipt of thermal energy.

This paper presents the results of numerical simulations for the developed and discussed conical two-phase atomizers with swirl flow, differing in the ratio of the height of the swirl chamber to its diameter. Experiments were carried out for SAN-1 with HS/DS = 1 and SAN-2 with HS/DS = 4 atomizers. The study was conducted over a range of Reynolds number for liquid ReL = (1400, 5650) and for gas ReG = (2970, 9900). Numerical calculations were performed with the use of computational fluid dynamics (CFD), which were verified on the basis of experimental data. Based on the analysis of experimental studies and simulations results the influence of operational parameters and changes of the atomizer geometry on the generated spray was demonstrated. As the gas flow rate increased and the swirl chamber height decreased, the spray angle increased. Higher velocity values of the liquid and greater turbulence occur in the center of the spray. The flow inside the atomizer determines the nature of the spray obtained. The geometry of the swirl chamber influences the air core formed inside the atomizer, and this determines the atomization effect. The results of numerical simulations not only confirm the results of experimental studies, but also provide additional information on internal and external fluid flow.

The analysis of fuel injection processes in diesel engines showed the convergence of physical parameters affecting the mean diameter of the Sauter SMD (selected as a spray quality parameter) of the atomized fuel droplets and the parameters of the acoustic signal emission originating from the spring waves accompanying the atomization process. In experimental studies, the laser diffraction method was used to measure the atomization quality with the Malvern Spraytec device. For the acoustic signal recording and processing there was used the measurement set with a Fujicera 1045S sensor. The correlation between the values of the Sauter diameter and the energy of the acoustic signal has been obtained on the basis of which a method has been developed to assess the quality of fuel atomization in compression ignition engines by measuring the acoustic signal recorded during the fuel injection process

To support the ongoing energy transition and minimize the environmental footprint of combustion related technologies, the paper presents a novel approach for combustion control in gas turbines and burners. It relies on spatially targeted injection of inert components in the spray core where existent concepts fail to deliver the desired dilution rate and are unable to fully govern the spatial distribution of heat release rates. Combustion process control is thus possible by actively adjusting the composition and mass flow of spatially selective introduction of inert species in the spray, optionally combined with classic, external exhaust gas recirculation, leading to an ultimate fuel-flexible concept which is capable of adjustments to heterogeneous fuels, their reactivity and physical properties. The proof of concept is demonstrated in a gas turbine combustion chamber first by investigating the isolated effects of spatially selective injection of inert species, its comparison to external exhaust gas recirculation and a combination of both. The results confirm the superiority of the approach as spatially selective mixture inertization is capable of 7% reduction of NO emissions with merely 3% increase of CO emissions and even 9% reduction of PM emissions. Furthermore, the concept proved transferrable together with all its benefits to combustion cycles with external exhaust gas recirculation. In this case, the 63% reduction of NO emissions with no observed CO penalty is possible. Simultaneous exploitation of spatially selective inertization, as well as external exhaust gas recirculation forms a fully controllable concept - spatially selective dilution control (SSDC), which enables extensive adjustability of dilution rates throughout the spray core and primary zone of combustion chamber. Compared to baseline case, such approach was proved to simultaneously reduce CO, NO and PM emissions normalized to fuel thermal power for 39%, 63% and 91%, respectively. The confirmation of applicability of the novel approach and its potential to influence the local conditions is opening a series of possible uses, either as an original design feature for future fuel-flexible systems or as a retrofit approach in existent combustion systems.

Experimental investigations are conducted to determine the mechanism and characteristics of a jet in an L-shape crossflow simulating the radial swirl injector of a lean premixed-prevaporized (LPP) combustor. To simplify the radial flow of the actual injector while ignoring the centrifugal effect, the L-shaped 2D-channel is used for the crossflow, and water is used as a fuel simulant. The jet breakup is captured using a high-speed camera, and the density gradient magnitude is post-processed to clarify the spray. The Sauter mean diameter (SMD) of the spray is measured via a laser diffraction method with a helium–neon laser optical system (HELOS). The characteristics of the jet in the L-shape crossflow are compared with the characteristics of the jet in a typical crossflow through the flat channel. The results for different outlet heights of the L-shape channel (H/d0) and different injector positions (L/d0) are presented. A dimensionless number (τ) consisting of a time ratio is introduced to describe the jet characteristics. In a previous work, the spraying tendency was demonstrated for different injector positions. In addition, the effect of the recirculation area on H/d0 was empirically shown. H/d0 determines the size of the recirculation area, and the range of τ determines the jet breakup mechanism inside the L-shape channel. The results of this study present the breakup mechanism of the jet in the L-shape channel flow, which simulates a jet in a radial swirler injector for gas turbine engines. It is expected that these results can be used to assist in designing gas turbine engines with more combustion efficiency.

International audience; In food industry, atomization is an essential process as a large range of products are manufactured by spray drying of concentrated solutions. The pressure drop inside the nozzle, and its relation with the flowrate, is of prime importance to size an efficient continuous process. This work thus aims at both studying liquid atomization using pressure nozzles with throttle inserts and proposing a ready-to-use pressure/flowrate correlation from a series of experimental data. Beside the process parameters (flowrate) and fluid parameters (viscosity, density) of prime importance, the geometrical parameters of the nozzle were also accounted for to obtain a generic correlation. Using Newtonian maltodextrin aqueous solutions with viscosity ranging from 1 to 70.10-3 Pa s and eleven nozzle geometries, 264 experiments were performed. Through the use of a dimensionless pressure drop number (Euler number), all the experimental points gathered on a single Eu* vs. Re curve where conventional atomization regimes could be clearly identified. A comprehensive dimensional analysis, relying on the Vashy-Buckingham theorem, was performed. A set of dimensionless correlations, allowing to predict the pressure loss over a wide range of Reynolds number from parameters linked to the fluid, process and nozzle geometry, was then deduced from experimental data.

The Ni-11Mo-8Al-3Ta-2Cr-1Re spherical powders of

Biofuels have extensive available resources and have an immense potential as promising alternative fuels for automobile. The application advantages of biofuels are mainly reflected as particulate matter (PM) reduction, carbon neutral, greenhouse gases reduction, waste utilization, energy and economic security, and fuel pluralism. Based on the understanding of molecular structure effects of biofuels on soot formation and particles morphology, the effects of alcohols, ethers, esters and biodiesel on spray and combustion process in constant volume bomb in recent years are retrospectively analyzed in this paper. For the mixture, macromolecular ester fuels and polyoxymethylene dimethyl ether (PODE) are conducive to the improvement of liquid spray, while biodiesel, small molecules, dimethyl ether (DME) and alcohols are reversed. Alcohols are advantageous to the extension of mixing time and the increasing of vapor-phase mixture. Through the influence integrated assessment, alcohols show the best performance on the spray, atomization and combustion, while biodiesels show the worst. But in terms of combustion, PODE is the best choice without considering spray and atomization. For binary alternative-diesel fuel blends, methanol or butanol is the best additive based on synthetically considerations on spray, atomization and combustion. To meet the requirements of the fuel application of diesel engine, ternary fuel or even quaternary fuel have been proposed and explored. This review can help to form a systematic understanding on fuel recombining and obtain the guide of clean and efficient fuel formulation for diesel engine.

This paper presents an experimental study into dynamics of chamber pressure and heat release rate during self-excited spinning and standing azimuthal mode in NTO/MMH (nitrogen tetroxide/monomethylhydrazine) impinging combustion chambers. Nine cases including two combustion chamber configurations were conducted. The operating conditions of all unstable cases were located in the instability region according to Hewitt empirical correlation. The results show that chamber pressure oscillations keep pace with the corresponding OH* chemiluminescence intensity over the whole combustion region in the spinning and standing modes. It is indicated that the Rayleigh index is positive over the whole combustion area in all the unstable cases. A significant supersonic flame front structure of the first-order spinning mode was found in a cylindrical chamber, which means that a detonation wave could exist in the cylindrical chamber without a center body. The pressure and heat release rate oscillations at the pressure node are nonnegligible although their amplitudes are lower than those at the pressure antinode in the first-order standing mode with an annular chamber. Besides, the dominant frequency of pressure and heat release rate oscillations at the pressure node is twice as high as that at the pressure antinode.

The devastating phenomenon of depletion of fossil fuel and environmental pollution have caught global concern to explore for alternative fuel resources that could meet human demand. Due to the properties that match diesel fuel properties, biodiesel appears to be one of the plausible resources due to the many advantages it provides compared to the conventional petroleum-diesel. Recently, non-edible oil receives worldwide attention compared to edible feedstock in producing biodiesel. Among the many privileges provided by non-edible Calophyllum inophyllum plant include useful by-products (glycerol), environmental friendly, ability to reduce the competition for food and more economical feedstock. Besides the application in the diesel engine, biodiesel could be a promising substitute to distillate fuel for power generation sector. Gas turbine develops steady flame during its combustion and this feature gives the flexibility of wide range of fuel selection including biodiesel for gas turbine. Therefore, the use of biodiesel in gas turbine seems a viable solution for the problems. This paper aims to evaluate the physiochemical properties of C. inophyllum (CI) biodiesel for gas turbine application. The properties of C. inophyllum methyl ester was obtained to evaluate its potential in gas turbine application according to the fuel selection standard for gas turbine; ASTM D2880 . The evaluation result show that C. inophyllum biodiesel may be pursued as an alternative fuel in gas turbine.

Direct injection has been widely used in internal combustion engines from the enhancement of knock resistance, the improvement of fuel consumption and the high thermal efficiency. On the other hand, problems such as adhesion of fuel to the wall surface and unburned components have been point out. Also the 20%-30% of the input heat quantity is lost as cooling loss^2), which can’t be ignored. Previous researches^1) indicated that the impinging injection can help with these problems. Therefore, in this study, we focused on the influence factors as the injection timing, the amount ratio of fuel injection and the fuel properties. Through the examination of the effects on the combustion improvement by using Coaxial Multi-impinging Fuel Injection(CMFI), we performed consideration by the observation of flame behaviors, Sauter Mean Diameter(SMD) of liquid fuel which the previous researched have proofed that the SMD is influenced by the fuel properties^3), and the combustion characteristics like the Maximum Burning Pressure(MBP), the Total Burning Time(TBT) and the Rate Of Heat Release(ROHR). The main conclusions are as follows:(1) It is possible to improve the combustion characteristics under heterogeneous combustion field by using the impinging injection.(2) The most suitable conditions of the injection timing and the amount of fuel injection ratio exist for combustion improvement by using the Coaxial Multi-impinging Fuel Injection.

This paper studies three-dimensional transient flow characteristics of a medical air-compressing nebulizer which is widely used to treat respiratory diseases in the medical field. The transient atomization process of air and water was numerically simulated and reproduced by solving Navier-Stokes equations, turbulent transport equations, the volume of fluid (VOF) model, and discrete phase model (DPM). The water volume fraction inside the nebulizer was simulated and demonstrated under different time. Besides, to better the working performance of the nebulizer, the effects of different working parameters such as different orifice diameters, length of the outflow pipe, and air velocity on the secondary atomization were also studied and discussed. It was found that the most suitable diameter of the orifice for this air-compressing nebulizer is 1.0 mm. Most suitable length of the outflow pipe and the air velocity for producing small air-water bubbles are 10 mm and 4 m/s, respectively.

A comprehensive study on Flow-Focusing/Flow-Blurring (FF/FB) atomizers is presented in this study. A transparent FF/FB atomizer is introduced in this work to aid in the characterization of sprays emitting from both of the atomizer’s regimes. Newtonian and non-Newtonian liquids were tested over a wide range of operating conditions and laser diagnostics were employed to unveil the resulting structures and salient features of the sprays. Direct imaging of the atomizer’s liquid tube tip region enabled identification of the onset of the atomizer’s regime transition at different liquid tube recesses and over a wide range of conditions. New regime transition maps for FF/FB atomizers have been created that are function of ALR, Weber number, momentum flux ratio and liquid Re, and can be employed to identify the operating regime of atomizers and the controlling parameters for transition. Spray droplet size and flow-field measurements using a PDPA/LDV setup were obtained and have enabled identification of unique flow features that characterize the FF and FB regimes, of importance is the shown dependence of the resulting droplet size on the operating Weber number for both regimes, and the trend of decreasing difference in droplet size between the two regimes as the Weber number increased. The spray morphology of Newtonian and non-Newtonian liquids was also investigated. The FF regime was found to behave similarly to air-blast atomizers when operating with non-Newtonian liquids, it had an advantage though in the atomization of Newtonian liquids. The FB regime demonstrated the ability to always generate droplets immediately as the spray exited the atomizer when operating with Newtonian liquids. However, non-Newtonian liquids have proven to be difficult to atomize in the FB regime where the liquid separated into multiple streams and only broke up at far downstream locations.

This thesis presents an extensive study of the atomization and combustion of dielectric liquids using a hybrid air-blast electrostatic atomizer. While airblast atomization relies on the shear stresses generated at the liquid-air interface, electrostatic atomization introduces an electric charge into the bulk liquid, and the resulted Coulombic repulsive force facilitates the fragmentation process. The atomizer introduced in this contribution is specifically designed to operate in either a single (air-blast or electrostatic) or hybrid mode to enable the delivery of a charged and/or air-assisted spray for combustion applications. The aim is to understand the effect of adding electric charge to a liquid jet which is subject to break up in a co-flowing air stream. In addition to analysis of atomization processes, the influence of charge on flame structure is also analyzed. Laser diagnostics are utilized for measurements and the results obtained for the atomizer in hybrid mode (air-blast + electrostatic) are compared with the pure air-blast mode. Firstly, a high-speed microscopic shadowgraphy technique is implemented to examine near-field spray structure. Diesel is used as a dielectric liquid to create various sprays that cover a range of non-dimensional numbers. The effect of charge on liquid jet unsteadiness and on the probability distribution of wavelength and amplitude of instabilities is discussed. The influence of charge on droplet and ligament size and their population is also analyzed. The findings show that the application of charge makes the liquid jet more unstable and the instabilities forming on the liquid core exhibit a shift to a shorter wavelength with a broadening in the probability distribution of wave amplitude. In addition, a droplet and ligament size reduction along with an increase in droplet count is observed with the addition of charge. The thesis then progresses to discussing results from reacting sprays stabilized on a pilot where kerosene is chosen as the liquid. A premixed pilot flame is used to provide a steady heat source for stabilizing the hybrid atomized sprays. Flame stability characteristics, in terms of blow-off velocity, are presented as a function of controlling parameters, without and with charge. Downstream droplet statistics and flow field for both non-reacting and reacting sprays are shown using laser Doppler velocimetry/phase Doppler anemometry (LDV/PDA) revealing key features in the droplet fields from this burner. Due to relatively low spray specific charge for the aerodynamic Weber numbers investigated, the droplet size and velocity remained largely unaffected through the addition of charge, however, a rise in particle concentration at the center of the spray was noted. Finally, high-speed hydroxyl planar laser induced fluorescence (OH-PLIF) is used to locate reaction zones and comment on the morphology of the reaction zone structures. In a hybrid mode, the charge was seen to push reaction zones radially outward and assisted in stabilizing the flame by keeping OH islands more connected when compared to a pure air-blast mode. This observation was also consistent with a slight improvement in flame stability with the addition of charge.

The current study aims to investigate and develop numerical tools for the simulation of interfacial flows, including those with turbulence and primary spray atomization. In the past, many approaches were developed to track the interface of a multi-phase/immiscible flow system. Two of them, the volume of fluid (VoF) and the level set (LS), have shown promising findings and have been considered a benchmark for further research. VoF methods have proved good mass conservation behaviour during the advection of solution. However, LS methods have shown better interface representation when used for the calculations of interfacial flows. Most of the recent development in this context either originated from VoF, LS or a combination of both. In the first part of this thesis importance of the current study is highlighted in detail, and an overview of the recent developments for the numerical solutions of immiscible flows is presented. A detailed description of interface-capturing methods and their development over time is presented in a systematic way, leading to the issues addressed in this study. A stochastic field PDF-LES solution of the VoF approach is analyzed against the Sydney needle spray measurements. Solution behaviour for different combinations of stochastic fields and LES grid cells are examined in detail. In the second part of this work, three different LES treatment for unresolved sub-grid fluctuations, TFVoF, TF-AC and newly developed EVD, has been presented. The performance analysis of two already existing solutions, TFVoF and TF-AC, is compared with the EVD approach. Sydney needle spray measurements are used as a benchmark for this comparison. The suitability of the EVD approach is also tested for different flow conditions. Simulation results confirm that sub-grid surface tension plays an important role in the realistic prediction of the jet decay rate, and proper closure models to account for sub-grid surface tension are very necessary. An already existing sub-grid surface tension closure model is incorporated into OpenFOAM and tested for all three LES filtered solutions. The findings of this work suggest that the newly developed EVD approach has shown promising improvements to produce more reliable and realistic solutions for multi-phase flow applications. Sub-volume surface tension closure model, following the EVD formulation, is helpful for more accurate jet decay rate predictions.

The review presents the results of experimental and theoretical studies obtained in recent years within the framework of the main areas of research of gel fuels: choice of component composition and substantiation of fuel preparation technologies and their rheological characteristics; fuel transportation and atomization processes; and the processes of their ignition and combustion. The main advantages of gel fuels in comparison with widely used liquid and solid fuels are considered. The advantages and disadvantages of known experimental approaches to the study of the combustion processes of gel fuels are analyzed. The well-known physical and mathematical models of gel fuels ignition are given, including those under conditions of melt droplets dispersion. The tendencies of further development of gel fuels within the framework of the combustion theory are formulated.

Microbial proteases, especially from Bacillus spp., have enormously been exploited for a broad variety of applications such as for physiological processes, food and feedstuff, detergents, as well as in the pharmaceutical and leather. In this work, proteases produced by the thermophilic Bacillus sp. SMIA-2 submerged cultures were spray-dried in an attempt to improve its stability for applications in industry. The enzymatic extract was dried using drying adjuvants, and optimal conditions for preserving enzymatic activity were studied following a statistical experimental design. The spray process factors studied were the drier air inlet temperature and the adjuvants concentrations. The responses analyzed were the enzymatic activity and mass recovered of the powder after spray drying. Additionally, the stability of the powder was assessed during 180 days at room temperature. The results revealed that satisfactory levels of enzymatic activity were obtained when 0.5% (w/v) carboxymethylcellulose and 1.0% (w/v) maltodextrin were incorporated to enzymes solutions and the spray drier inlet temperature was 110 ºC. Furthermore, this dried protease extracts showed potential for future commercial applications because of their stability at room temperature for 180 days.

This article belongs to the Special Issue Dry Powders for Pulmonary Delivery: Device and Formulation Technologies for an Enhanced Lung Deposition., The inhaled route is regarded as one of the most promising strategies as a treatment against pulmonary infections. However, the delivery of drugs in a dry powder form remains challenging. In this work, we have used alginate to form microparticles containing an antibiotic model (colistin sulfate). The alginate microparticles were generated by atomization technique, and they were characterized by antimicrobial in vitro studies against Pseudomonas aeruginosa. Optimization of different parameters allowed us to obtain microparticles as a dry powder with a mean size (Feret diameter) of 4.45 ± 1.40 µm and drug loading of 8.5 ± 1.50%. The process developed was able to concentrate most of the colistin deposits on the surface of the microparticles, which could be observed by SEM and a Dual-Beam microscope. This produces a fast in vitro release of the drug, with a 100% release achieved in 4 h. Physicochemical characterization using the FTIR, EDX and PXRD techniques revealed information about the change that occurs from the amorphous to a crystalline form of colistin. Finally, the cytotoxicity of microparticles was tested using lung cell lines (A549 and Calu-3). Results of the study showed that alginate microparticles were able to inhibit bacterial growth while displaying non-toxicity toward lung cells., Financial support from Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN). Initiative funded by the VI National R&D&I Plan 2008–2011, Iniciativa Ingenio 2010, Consolider Program, CIBER Actions and financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund. Spanish Ministry of Science for project funding entitled: Non-Cytotoxic Nanoparticles for Promoting a Double Metabolic Inhibition of Tumour Growth: Cancer Cell as a Biochemical Reactor (PID2019-108994RB-I00).

The mechanisms involved in assisted atomization have been the subject of detailed analyses. Yet, the role of surfactants on these processes has rarely been addressed, so that the impact of surfactants on the evolution of the liquid jet and on the production of drops remains poorly understood. In order to better understand their role, the atomization of a liquid jet (water and surfactant) driven by a coaxial gas stream (air) is experimentally studied, over wide ranges of liquid and gas injection velocities. Three surfactants (SDS, C12TAB, C16TAB) with various properties have been selected: used at different concentrations, they allow to explore a very wide range of characteristic migration times to the interface, evolving from 10-3 to 1 second. Attempts to characterize their rheological properties are also proposed.The injector used consists of a liquid tube of 5 mm diameter, and a coaxial gas tube with a 5 mm section. A decontamination procedure of the liquid circuit after surfactant injection has been implemented, ensuring the reproducibility of the measurements.We first characterized by image analysis the structure of the liquid jet before its breakup, as well as the frequencies of the instabilities leading to the droplet formation.Both SDS and C12TAB candidates significantly increase the breakup length of the liquid jet. These molecules exhibit adsorption dynamics faster than the characteristic times of liquid structure formation, allowing to significantly lowering the surface tension at the tip of the liquid jet prior to its breakup. Conversely, the surfactant with slow adsorption dynamics (C16TAB) does not change the structure of the liquid jet. A model for the breakup length, based on the dynamic surface tension, shows good agreement with the measurements.C12TAB induces additional effects: the reduction of the oscillation amplitude of the jet (up to 40%), and of its breakup frequency (up to 50%). Finally, addition of SDS and C12TAB leads to changes in the mode of liquid jet breakup at low gas injection velocities: from a dominant fiber/ligament type jet breakup, a majority of breakups with membrane formation is observed due to the reduction of the surface tension.Finally, the frequencies of shear and flapping instabilities of the liquid jet are not affected by surfactants, as these mechanisms do not depend on the surface tension.The characteristics of the droplets resulting from liquid jet assisted atomization were studied using three techniques: laser diffraction particle size analysis, fast imaging and Doppler optical probe. The Doppler optical probe is a new sensor: its use on sprays required developments and optimizations of the signal processing routines. This sensor have then been tested by comparing the integral of radial liquid flow profiles to the injected flow rate: the observed deviations are less than 20, demonstrating the reliability of the instrument.Finally, the spray was characterized in the presence of surfactants. Laser diffraction, which allows to measure a distribution of droplet sizes on a spray diameter. The latter remains constant beyond twice the average breakup length of the liquid jet, with or without surfactant. Then the volume size distributions show that surfactants having an impact on the structure of the liquid jet also induce a higher presence of small drops than with pure water. Finally, the optical Doppler probe is used to measure sizes, velocities and fluxes of drops at the center of the spray.We thereby demonstrate that the parameter governing the influence of a surfactant on the atomization process is the adsorption time, which depends on the nature of the surfactant and its concentration. If this time is low compared to the typical break-up times of the liquid jet, its structure is affected, as well as the downstream spray resulting from its atomisation., Si les mécanismes intervenant en d’atomisation assistée ont fait l’objet d’analyses détaillées, le rôle de surfactants sur ces processus n’a été que rarement abordé, de sorte que l’impact de tensioactifs sur l’évolution du jet liquide et sur la production de gouttes reste très mal compris. Dans le but de mieux appréhender leur rôle, l’atomisation d’un jet liquide (eau) dopé et entraîné par un courant gaz (air) coaxial est étudiée expérimentalement, sur de larges plages de vitesses d’injection liquide et gaz. Trois tensioactifs (SDS, C12TAB, C16TAB) aux propriétés variées ont été sélectionnés : utilisés à différentes concentrations, ils permettent d’explorer des temps caractéristiques de repeuplement de l’interface évoluant sur une très large plage, allant de 10-3 à 1 seconde. Des tentatives pour caractériser leurs propriétés rhéologiques sont également proposées.L’injecteur utilisé est constitué d’un tube liquide et d’un tube gaz coaxial, tous deux d’une section de 5 mm. Un protocole de dépollution du circuit liquide après injection de tensioactifs a été mis en place, assurant la reproductibilité des mesures.Dans un premier temps, nous avons caractérisé par analyse d’image la structure du jet liquide avant sa rupture, ainsi que les fréquences des instabilités intervenant dans la formation des gouttes. Tout d’abord, les candidats SDS et C12TAB augmentent significativement la distance de brisure du jet liquide. Ces molécules présentent des dynamiques d’adsorption plus rapides que les temps caractéristiques de formation des structures liquides, ce qui permet un abaissement significatif de la tension de surface à l’extrémité du jet avant sa brisure. Dans le cas contraire, le tensioactif à dynamique d’adsorption lente (C16TAB) ne modifie pas la structure du jet liquide. Un modèle pour la longueur de brisure, basé sur la tension de surface dynamique, montre un bon accord avec les mesures. Le C12TAB induit des effets supplémentaires : la réduction de l’amplitude d’oscillation du jet (jusqu’à 40%), et de sa fréquence de brisure (jusqu’à 50%).Enfin, le dopage avec SDS et C12TAB conduit à des changements du mode de brisure du jet liquide aux faibles vitesses d’injection gaz: d’une rupture de type fibre/ligament, une majorité de brisures avec formation de membranes est observée due à la réduction de la tension de surface.Les fréquences des instabilités de cisaillement et de battement du jet liquide ne sont affectées par aucun tensioactif car ces mécanismes ne dépendent pas de la tension de surface. Les caractéristiques des gouttes résultant de l’atomisation du jet liquide ont été étudiées à l’aide de trois techniques : la granulométrie par diffraction laser, l’imagerie et la sonde optique Doppler. La sonde optique Doppler est une technique nouvelle, et a donc nécessité des développements et des optimisations des procédures de traitement du signal. Puis ce capteur a été testé en comparant l’intégrale de profils de flux liquide au débit injecté : les écarts observés sont inférieurs à 20%, démontrant la fiabilité de l’instrument.Enfin, le spray a été caractérisé en présence de tensioactifs. La diffraction laser, – qui mesure une distribution de tailles volumiques de gouttes sur un diamètre de spray -, est utilisée pour quantifier l’évolution de la taille des gouttes avec la distance axiale à l’injecteur, pour différentes vitesses gaz. Puis les distributions de tailles volumiques montrent que les tensioactifs ayant un impact sur la structure du jet induisent également une plus forte présence de gouttes de faibles tailles qu'en eau pure. Finalement, tailles, vitesses et flux de gouttes sont mesurés par sonde optique.Nous montrons ainsi que le paramètre gouvernant l’influence d’un tensioactif sur l’atomisation est le temps d’adsorption, qui dépend de la nature du tensioactif et de sa concentration. Si ce temps est faible devant les temps de rupture du jet liquide, sa structure est impactée, ainsi que le spray résultant de son atomisation.

Hot Isostatic pressing process is based on the densification of metals powders to near net shape parts with higher mechanicals properties than forged chemical equivalent. The precursor material can influence the parts properties. Thus the aims of this these is to understand the influence of the powder properties on the HIP parts. The particles characterization and the elements and compound monitoring during the HIP cycle allowed to understand the different oxidations phenomenons and their impact on the mechanical properties of parts. The comparison of differents powders batches with identical particles size repartition or identical chemical composition showed that the chemical composition affect the phases and the grains size of the material while the particle grains size repartition only affect the compaction rate. These results bring a possibility of deformations optimization during HIP to manufactured near net shape part whit high mechanical properties. Models developed in this study allow an identification of the batch utilization in accordance with its properties., La compaction isostatique à chaud est une technologie basée sur le frittage de poudre métallique pour obtenir des pièces denses, au plus près de la forme "Near net shape" et avec des propriétés mécaniques supérieures à une pièce forgée du même matériau. Les propriétés des pièces étant dépendantes des caractéristiques du matériau précurseur, l’influence de ce dernier a été étudiée. La caractérisation des particules de poudres ainsi que le suivi des différents éléments et composé au cours du cycle de compaction a permis de mieux comprendre les différents phénomènes d’oxydations et leurs influences sur les propriétés mécaniques des pièces. La comparaison de différents lots de poudre de granulométrie ou de composition identiques a mis en évidence que la composition de l’alliage influence les phases présentes et la taille des grains alors que la granulométrie n’influence que le taux de compaction des pièces. Ces résultats permettent d’optimiser la déformation des pièces pour permettre la réalisation de pièces au plus près de la forme tout en conservant les propriétés mécaniques des pièces. Les différents modèles réalisés permettent d’identifier les possibilités d’un lot de poudre suivant ses propriétés.

Disintegration of liquid masses in a free-surface flow is still an open question in the field of small-scale spray applications such as dispensing of detergents or sanitizing products. In this context, the pressure-swirl atomizer is widely investigated. It allows to improve several spray characteristics through the formation and breakup of a conical liquid sheet that results in the well-known hollow-cone atomization. From this perspective, the characterization of a small-scale pressure-swirl spray under laminar flow conditions is the focus of this work. The configuration of the device and the physical properties of the discharged liquid are the key parameters that modify the attributes of such multiscale flow. In this regard, the entire picture of the fragmentation process is structured into multiple stages: internal nozzle flow, outer displacement of the liquid–gas interface, droplet spread into the atmosphere, and droplet-wall interactions on a collection surface. Through the computational fluid dynamics, we analyze the influence of the main fluid/packaging parameters on the hollow-cone spray properties, and on the whole atomization process. Reynolds and Ohnesorge numbers are coupled with the Sauter mean diameter to distinguish different breakup mechanisms and spray performances. The solution of the entire spray system is performed by implementing the volume-of-fluid-to-discrete-phase-model, which allows to capture the liquid–gas interface displacement and track the droplets produced downstream the primary atomization, simultaneously. With this Eulerian–Lagrangian hybrid model, we link key features of the hollow-cone spray process to spray pattern and droplet size distribution for both Newtonian and non-Newtonian fluid properties.