Rozprawy doktorskie na temat „Spray research”

Plants of Chrysanthemum moifolium Ramat. 'Ovaro' received 0, 10, 20, or 30 mg-liter ⁻¹ XE-1019 applied as a 204 ml-m⁻² foliar spray. Treatments did not affect time from start of short days to bloom or inflorescence height lunge. Inflorescence height and inflorescence display diameter both were reduced with increasing concentration of XE-1019.

Plant of Chysanthemum morífolium Rymat. 'Ovaio' received 0, 102, 204, 304 or 408 ml-m⁻² of 0, 40, 20, 13.3, and 10 mg-liter⁻¹ XE-1019, respectively. No treatment affected time from start of short days to bloom or inflorescence display diameter. All XE-1019 treatments resulted in shorter plants than controls did. No carrier volume effect on plant height was observed. The inflorescence height range per pot decreased with increasing carrier volume. The greater inflorescence height uniformity achieved with the high carrier volume is beneficial and warrants further investigation.

Plants of Euphorbia pulchenima Wind. 'Gutbier V-14 Glory Annette Hegg Dark Red', and 'Annette Hegg Brilliant Diamond' were treated with 37 iw a.i. of XE-1019 applied in 102, 204, or 408 ml-m⁻² foliar sprays. Half of the plants received overhead irrigation and the remaining received soil-surface irrigations. No spray carrier volume effect or irrigation effect was observed for final plant height, bract canopy diameter, or for days from start of short days to bloom. The results obtained do not support the hypothesis that spray carrier volume or irrigation method affect the efficacy of XE-1019 on poinsettias.

La technologie de programmation hors-ligne permet la génération de la trajectoire complexe en projection thermique. Dans le laboratoire du LERMPS, une extension logicielle appelée « Thermal Spray Toolkit » (T.S.T.) a été développée pour assister la programmation hors-ligne dans le domaine de projection thermique. Cependant, les efforts sont encore attendus pour améliorer sa fonctionnalité. Donc, l'objectif de cette thèse est d'améliorer l'application de la programmation hors-ligne en projection thermique. Selon la procédure d'application, les travaux de cette thèse se composent de trois parties.Premièrement, les efforts sont dévoués à l'amélioration du module « PathKit » dans T.S.T., afin d'optimiser la fonctionnalité de la génération de la trajectoire. L'algorithme pour la génération de la trajectoire sur le substrat courbe a été étudié pour assurer le pas de balayage constant. Une nouvelle trajectoire « spirale d'Archimède » a été développé pour réparer les défauts par la projection à froid. La réparation sur une pièce d'aluminium avec un défaut a été réalisé pour valider la trajectoire spirale d'Archimède. Deuxièmement, les modélisations ont été développées pour simuler l'épaisseur du dépôt en 2D et en 3D. Puis, Ils sont intégrés dans le logiciel RobotStudioTM comme un module individuel dit « ProfileKit ». Dans le « ProfileKit 2D », il peut évaluer les effets des paramètres opératoires sur le profil du dépôt et puis optimiser les paramètres. Dans le « ProfileKit 3D », l'épaisseur du dépôt peut être simulée selon la trajectoire du robot et la cinématique du robot.Les fonctionnalités sont validées par un dépôt de forme trapézoïdal élaboré par la projection à froid avec les pas debalayage variés.Dernièrement, l'analyse cinématique du robot a été étudiée pour optimiser la performance du robot pendant le processus de projection. Afin de mieux évaluer la performance du robot, un paramètre « overall parameter » (OP), la moyenne pondérée d'écart-type de la vitesse articulaire est introduit pour mesurer la complexité de la trajectoire du robot. Ensuite, l'optimisation du montage de la torche ainsi que l'optimisation de la disposition de la pièce sont étudiées par l'analyse cinématique du robot et le paramètre OP. Le résultat montre que l'optimisation cinématique peut efficacement améliorer la performance du robot pour maintenir la vitesse prédéfinie
The offline programming technology provides the possibility to generate complex robot trajectories in thermal spray process. In the laboratory of LERMPS, an add-in software called “Thermal SprayToolkit” (T.S.T.) has been developed to assist the offline programming in the field of thermal spray.However, efforts are still expected to improve the functionality of this software. The aim of this study is to improve the application of offline programming technology in the thermal spray process. According to the procedure of the offline programming in thermal spray, the work of this thesis consists of three parts.Firstly, efforts have been dedicated to improve the module “PathKit” in T.S.T., which aim to improve the functionality of trajectory generation. The algorithm of trajectory generation for the curved substrate surface was improved to maintain a constant scan step. A novel Archimedean spiral trajectory was developed for damage component recovery application by cold spray. The experiment of an Al5056 coating depositing on a manually manufactured workpiece with a crater defect was carried out to validate the effects of spiral trajectory with adapted nozzle speed.Secondly, numerical models were developed to simulate the coating thickness distribution in 2D and 3D, and then integrated in the RobotStudio™ as an individual module named “ProfileKit”. In the “ProfileKit 2D”, it is able to evaluate the effects of operating parameters on coating profile and optimize the parameters. In the “ProfileKit 3D”, coating thickness distribution can be simulated based on the nozzle trajectory and robot kinematics data. The functionalities were validated by the trapezoid coldsprayed coating.At last, kinematic analysis was used to provide the optimization methods for a better robot performance in thermal spraying. In order to better evaluate the robot performance, an overall parameter (OP) that is the weighted mean of standard deviation of joint speed, was introduced to measure the complexity of a robot trajectory. Afterwards, the optimal nozzle mounting method as well as the optimal workpiece placement were investigated by the kinematic analysis and the overall parameter. The result shows that the kinematic optimization can effectively improve the robot performance to maintain the predefined speed

Land application of wastes has become increasingly popular, to promote nutrient recycling and environmental protection, with soil functioning as a partial barrier between wastes and groundwater. Dairy shed effluent (DSE), may contain a wide variety of pathogenic micro-organisms, including bacteria (e.g. Salmonella paratyphyi, Escherichia coli. and Campylobacter), protozoa and viruses. Groundwater pathogen contamination resulting from land-applied DSE is drawing more attention with the intensified development of the dairy farm industry in New Zealand. The purpose of this research was to investigate the fate and transport of bacterial indicator-faecal coliform (FC) from land-applied DSE under different irrigation practices via field lysimeter studies, using two water irrigation methods (flood and sprinkler) with contrasting application rates, through the 2005-2006 irrigation season. It was aimed at better understanding, quantifying and modelling of the processes that govern the removal of microbes in intact soil columns, bridging the gap between previous theoretical research and general farm practices, specifically for Templeton soil. This study involved different approaches (leaching experiments, infiltrometer measurements and a dye infiltration study) to understand the processes of transient water flow and bacterial transport; and to extrapolate the relationships between bacterial transport and soil properties (like soil structure, texture), and soil physical status (soil water potential ψ and volumetric water content θ). Factors controlling FC transport are discussed. A contaminant transport model, HYDRUS-1D, was applied to simulate microbial transport through soil on the basis of measured datasets. This study was carried out at Lincoln University’s Centre for Soil and Environmental Quality (CSEQ) lysimeter site. Six lysimeters were employed in two trials. Each trial involved application of DSE, followed by a water irrigation sequence applied in a flux-controlled method. The soil columns were taken from the site of the new Lincoln University Dairy Farm, Lincoln, Canterbury. The soil type is Templeton fine sandy loam (Udic-Ustochrept, coarse loamy, mixed, mesic). Vertical profiles (at four depths) of θ and ψ were measured during leaching experiments. The leaching experiments directly measured concentrations of chemical tracer (Br⁻ or Cl⁻) and FC in drainage. Results showed that bacteria could readily penetrate through 700 mm deep soil columns, when facilitated by water flow. In the first (summer) trial, FC in leachate as high as 1.4×10⁶ cfu 100 mL⁻¹ (similar to the DSE concentration), was detected in one lysimeter that had a higher clay content in the topsoil, immediately after DSE application, and before any water irrigation. This indicates that DSE flowed through preferential flow paths without significant treatment or reduction in concentrations. The highest post-irrigation concentration was 3.4×10³ cfu 100 mL⁻¹ under flood irrigation. Flood irrigation resulted in more bacteria and Br⁻ leaching than spray irrigation. In both trials (summer and autumn) results showed significant differences between irrigation treatments in lysimeters sharing similar drainage class (moderate or moderately rapid). Leaching bacterial concentration was positively correlated with both θ and ψ, and sometimes drainage rate. Greater bacterial leaching was found in the one lysimeter with rapid whole-column effective hydraulic conductivity, Keff, for both flood and spray treatments. Occasionally, the effect of Keff on water movement and bacterial transport overrode the effect of irrigation. The ‘seasonal condition’ of the soil (including variation in initial water content) also influenced bacterial leaching, with less risk of leaching in autumn than in summer. A tension infiltrometer experiment measured hydraulic conductivity of the lysimeters at zero and 40 mm suction. The results showed in most cases a significant correlation between the proportion of bacteria leached and the flow contribution of the macropores. The higher the Ksat, the greater the amount of drainage and bacterial leaching obtained. This research also found that this technique may exclude the activity of some continuous macropores (e.g., cracks) due to the difference of initial wetness which could substantially change the conductivity and result in more serious bacterial leaching in this Templeton soil. A dye infiltration study showed there was great variability in water flow patterns, and most of the flow reaching deeper than 50 cm resulted from macropores, mainly visible cracks. The transient water flow and transport of tracer (Br⁻) and FC were modelled using the HYDRUS-1D software package. The uniform flow van Genuchten model, and the dual-porosity model were used for water flow and the mobile-immobile (MIM) model was used for tracer and FC transport. The hydraulic and solute parameters were optimized during simulation, on the basis of measured datasets from the leaching experiments. There was evidence supporting the presence of macropores, based on the water flow in the post-DSE application stage. The optimised saturated water content (θs) decreased during the post-application process, which could be explained in terms of macropore flow enhanced by irrigation. Moreover, bacterial simulation showed discrepancies in all cases of uniform flow simulations at the very initial stage, indicating that non-equilibrium processes were dominant during those short periods, and suggesting that there were strong dynamic processes involving structure change and subsequently flow paths. It is recommended that management strategies to reduce FC contamination following application of DSE in these soils must aim to decrease preferential flow by adjusting irrigation schemes. Attention needs to be given to a) decreasing irrigation rates at the beginning of each irrigation; b) increasing the number of irrigations, by reducing at the same time the amount of water applied and the irrigation rate at each irrigation; c) applying spray irrigation rather than flood irrigation.

Agrichemical spray drift is an issue of concern for the orcharding industry. Shelterbelts surrounding orchard blocks can significantly reduce spray drift by intercepting droplets from the airflow. At present, there is little information available with which to predict drift deposits downwind, particularly in the case of a fully-sheltered orchard block. In this thesis, we develop a simple mathematical model for the transport of airborne drifting spray droplets, including the effects of droplet evaporation and interception by a shelterbelt. The object is for the model to capture the major features of the droplet transport, yet be simple enough to determine an analytic solution, so that the deposit on the ground may be easily calculated and the effect of parameter variations observed. We model the droplet transport using an advection-dispersion equation, with a trapping term added to represent the shelterbelt. In order to proceed analytically, we discretise the shelterbelt by dividing it into a three-dimensional array of blocks, with the trapping in each block concentrated to the point at its centre. First, we consider the more straightforward case where the droplets do not evaporate; solutions are presented in one, two and three dimensions, along with explicit expressions for the total amount trapped and the deposit on the ground. With evaporation, the model is more difficult to solve analytically, and the solutions obtained are nestled in integral equations which are evaluated numerically. In both cases, examples are presented to show the deposition profile on the ground downwind of the shelterbelt, and the corresponding reduction in deposit from the same scenario without the shelterbelt.

yes
The NLW database illustrates the extensive and eclectic literature regarding NLWs which covers the last few decades. It currently contains over 250 entries. It is important to have access not only to the more recent material, but also to earlier sources since many of the general debates and controversies have already been rehearsed, and lessons learnt from them are still relevant today. Yet, it is also vital to follow new developments of NLWs closely because rapidly changing technology is producing weapons whose implications for integration into military and civil police forces have yet to be clearly defined and understood. Of particular interest are not only NLW applications for war fighting, but opportunities for deployment in peace enforcement and peace keeping missions. These technologies span many bases including: psycho-chemicals; unmanned weapons platforms and delivery systems; biogenetics; acoustic and microwave weapons; biological and chemical weapons; laser systems; kinetic energy ballistics; dual purpose (lethal/non-lethal) weapons; and, sprays and foams which inhibit movement. The database will keep up to date on these developments and future reports will highlight new issues and debates surrounding them. With these rapid technological advances come a series of associated dangers and concerns including: the ethics of use; implications for weapons control and disarmament treaties; military doctrine; public accountability and guidelines; dangers of misuse and proliferation; and, research and development strategies. Using the database, and drawing from military and non-military sources, this report will select the main current issues and debates within the non-lethal community. Bearing in mind that many operations undertaken by military forces are now more akin to policing actions (such as peace support operations) there are lessons to be learnt by military units from civil police experience. There still remains a tension between perceived benign and malign intent both in NLW operational use and non-lethal research and development.

yes
Non-lethal weapons (NLWs) are explicitly designed and primarily employed to incapacitate personnel or material whilst minimising collateral damage to property and the environment. Existing NLWs include rubber and plastic bullets, entangling nets, chemical sprays such as OC and CS gas, and electrical stunning devices such as the `Taser¿ gun. New NLWs are on the way, which will include acoustic and microwave weapons, non-lethal landmines, malodorants, and sophisticated weapons developed through rapid advances in neuroscience and the genomics revolution. Most analysts would agree that there is a `legitimate¿ role for non-lethal weapons, both for civil and military applications. However there is considerable disagreement as to the operational effectiveness of NLWs, and the threat such weapons pose to arms conventions and international law. As usual, a balance has to be achieved where the benign advantages of developing and deploying non-lethal weapons are not outweighed by their more malign effects. In particular, emerging non-lethal technologies offer an increasing opportunity for the suppression of civil dissent and control of populations ¿ these are sometimes referred to as the `technologies of political control¿. There is a continuing need for sustained and informed commentary to such developments which highlights the impact and threats that these technologies pose to civil liberties and human rights. Because the last BNLWP Report was produced in August 2001, this edition is somewhat longer than usual so that key developments since then can be highlighted and summarised. Future BNLWRP reports will be published three times a year, and we welcome material to be considered for inclusion.

yes
Two recent detailed reports, by the U.K Northern Ireland Office (NIO) - January 2004 1 and the U.S. Council on Foreign Relations (CFR) - February 2004 2, provide further insights into current policy and technology developments in the U.K. and U.S. The NIO report is the 4th and final report of a U.K wide Steering Group set up by the Secretary of State for Northern Ireland in Summer 2000, with the objective: To establish whether a less potentially lethal alternative to baton rounds is available; and to review the public order equipment which is presently available, or could be developed, in order to expand the range of tactical options available to operational commanders. 3 In her foreword to the report Jane Kennedy, Minister of State for Northern Ireland notes that: Despite a protracted and international search for a commercially available product, we have been unable to find anything that meets the criteria of an acceptable, potentially less lethal alternative to the baton round currently in service which provides an effective capability that does not expose officers and the public to greater risk in violent public disorder.4 The NIO Report has sections looking at the Defence Science and Technology Laboratory (DSTL) programme on the development of less lethal technologies (particularly the Attenuating Energy Projectile and the Discriminating Irritant Projectile); commercial off the shelf product evaluations and update (12 Gauge Sock Round Assessment); Water Cannon; the U.K. use of less lethal technologies (with a focus on L21A1 baton rounds, CS sprays and the Taser). The report also contains a section entitled `The Management of Conflict¿ which discusses the dynamics of crowd behaviour. For a critical response to the NIO report see that from Dr. Brian Rappert.5 The CFR report provides a strong endorsement for non-lethal weapons. A key finding states: Wider integration of nonlethal weapons into the U.S. Army and Marine Corps could have reduced damage, saved lives, and helped to limit the widespread looting and sabotage that occurred after the cessation of major conflict in Iraq. Incorporating NLW capabilities into the equipment, training and doctrine of the armed services could substantially improve U.S. effectiveness in conflict, post-conflict, and homeland defense. 6 Interestingly, in describing the nonlethal capability sets (NLCS) which have been deployed in Kosovo and Iraq, and which help to provide a continuum of force between ¿don¿t shoot¿ and ¿shoot¿ 7, the CFR seems to distinguish between NLWs (rubber balls [grenades and shotgun munitions], bean bags, riot shields, Tasers, net entanglers, and caltrops), and equipment such as flash-bang grenades, laser dazzlers, and bullhorns of which it states ¿It is important to note that these are not weapons but non-lethal capabilities¿ 8 The CFR recommends expanded deployment of NLWs in the armed services, longer ranges for non-lethal payloads using precision delivery and fusing systems, and further development of millimetre-wave area-denial system (HPM weapons such as VMADS) and the advanced tactical laser (ATL). The report also argues for the need to have a bigger Joint Non-Lethal Weapons Directorate (JNLWD) or a new Non-lethal Joint Program Office (NLJPO) and for Bradford Non-Lethal Weapons Research Project (BNLWRP) ¿ Research Report 5 (May 2004) 2 closer links with the Joint Forces Command (JFCOM). In the opinion of the authors the JNLWD should also have more access into classified programmes throughout all branches of the armed services so as not to duplicate non-lethal development initiatives. To stimulate incorporation of NLWs throughout the U.S. Armed Services the CFR advocates two approaches: (1) top-down planning in the Defense department and (2) creation of demand for these [NLWs] weapons from the field as personnel gain experience with prototype equipment. 9 They argue there is a need for the top-level military and civilian leadership to be educated about NLW capabilities, not only for warfighting and peacekeeping, but also in `homeland defence in isolating a hot zone in the aftermath of a biological attack' 10. We will be referring again to both the NIO and CFR publications in other sections of this report.

Робота виконана у Тернопільському національному технічному університеті імені Івана Пулюя Міністерства освіти і науки України. Захист відбудеться «12» жовтня 2010 р. о 1200 годині на засіданні спеціалізованої вченої ради Д 58.052.02 у Тернопільському національному технічному університеті імені Івана Пулюя за адресою: 46001, м. Тернопіль, вул. Руська, 56, аудиторія 79. З дисертацією можна ознайомитись у бібліотеці Тернопільського національного технічного університету імені Івана Пулюя за адресою: 46001, м. Тернопіль, вул. Руська, 56.
У дисертаційній роботі на сучасному технічному рівні вирішується завдання дослідження впливу обертових мас приводу на несучі конструкції сільськогосподарських машин. Впроваджено фотоелектричний моментомір, створено математичне обґрунтування обробки цифрового сигналу, записаного реєструючою системою, яке закладено в основу комп’ютерної програми «Krejаtor» для виведення сигналу на екран монітора у формі придатній для статистичної обробки. З використанням розроблених засобів вимірювання проведено дослідження машин ОВП-2000 та ОШУ-50А. Результати досліджень покладено в основу розрахунку консолі кріплення вентилятора методом мінімуму потенціальної енергії деформації. За результатами теоретичних досліджень запропоновано внести зміни в конструкцію консолі, що дозволить знизити її матеріалоємність, та забезпечить нормативний ресурс роботи.
В диссертационной работе на современном техническом уровне решено важную научно-техническую задачу - повышение работоспособности сельскохозяйственных машин, типа вентиляторных опрыскивателей с приводом от ВВП энергосредства. В основу работы положены исследования влияния разницы знакопеременных нагрузок в опорах мультипликатора от привода крутящего момента, а также дисбаланса вращающихся масс вентиляторной установки, что повышает достоверность оценки несущей способности, оптимизацию и необходимую долговечность рассматриваемой конструкции. Разработано научно-техническую методику по определению эксплуатационных кососиметрических знакопеременных нагрузок относительно продольной плоскости симметрии машин типа одноосных ельскохозяйственных прицепов и алгоритм аналитически-экспериментального исследования, сочетающий в себе модифицированный метод минимума потенциальной энергии деформации конструктивных структур со специально сконструированными средствами эксплуатационных исследований реальной динамики нагруженности. Реализованый комплексный подход обеспечил: снижение НДС в лонжеронах консольного крепления вентиляторной установки с 52 МПа до 34 МПа (лонжерон 59) и с 63 МПа до 36 МПа (лонжероны 63). Благодаря достижению упругого равновесия в элементах базовой несущей системы металлоемкость усовершенствованной металлоконструкции снизилась на 8,7%. При нормативном сроке службы опрыскивателей 7 лет и сезонной эксплуатации 300 часов ресурс работы составляет: серийной конструкции -1100 часов; модернизированной -2250 часов (Патент Украины на полезную модель № 48663, от 25.04.2010 г.), что вполне соответствует нормативному сроку службы. Годовой экономический эффект от усовершенствования несущей системы машины ОВП-2000 составляет 3350 грн. на одно изделие.
The research of influence the rotating mass drive over the main constructions of agricultural machines on the modern level is decided in this dissertation work. Photoelectrical momentomir is used, the mathematical study of digital signal processing is created, recorded by the recording system, which laid the basis for the computer program "Krejator" for output a signal on the monitor screen in a form suitable for statistical processing. Such machines as ОВП-2000 and ОШУ-50A are tested using developed means of measuring. The results of research are put in the basis for calculating the console fan fastensng using method of minimum potential energy of deformation. According to the results of theoretical studies modifications to the console consumption are proposed which will help to reduce its material consumption and provide normative resource of work.

В работе методом рентгендифрактометрии исследованы пленки, полученные методом спрей-пиролиза с использованием в качестве прекурсора раствора хлорида магния. Определен интервал температур подложек, где растут пленки кубического оксида магния с нанокристаллической структурой. Параметры кристаллической решетки соединения составляли а = 0,42345 нм для слоев, нанесенных при Ts = 380 0C, и а = 0,42121 нм при Ts = 400 0C, что хорошо коррелирует со справочными данными.
A spray pyrolysis method has been applied to prepare MgO thin films on glass substrates by using magnesium chloride hexahydrate as starting reactants. Structural properties of the films have been investigated. The experimental results revealed that the substrates temperature played important roles in the formation MgO film.

Active layer morphology of polymer-based solar cells plays an important role in improving power conversion efficiency (PCE). In this thesis, the focus is to improve the device efficiency of polymer-based solar cells. In the first objective, active layer morphology of polymer-solar cells was optimized though a novel solvent annealing technique. The second objective was to explore the possibility of replacing the highly sensitive aluminum cathode layer with a low-cost and stable alternative, copper metal. Large scale manufacturing of these solar cells is also explored using roll-to-roll printing techniques. Poly (3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl (PCBM) were used as the active layer blend for fabricating the solar cell devices using bulk heterojunction (BHJ), which is a blend of a donor polymer and an acceptor material. Blends of the donor polymer, P3HT and acceptor, PCBM were cast using spin coating and the resulting active layers were solvent annealed with dichlorobenzene in an inert atmosphere. Solvent annealed devices showed improved morphology with nano-phase segregation revealed by atomic force microscopy (AFM) analysis. The roughness of the active layer was found to be 6.5 nm. The nano-phase segregation was attributed to PCBM clusters and P3HT domains being arranged under the solvent annealing conditions. These test devices showed PCE up to 9.2 % with current density of 32.32 mA/cm2, which is the highest PCE reported to date for a P3HT-PCBM based system. Copper was deposited instead of the traditional aluminum for device fabrication. We were able to achieve similar PCEs with copper-based devices. Conductivity measurements were done on thermally deposited copper films using the two-probe method. Further, for these two configurations, PCE and other photovoltaic parameters were compared. Finally, we studied new techniques of large scale fabrication such as ultrasonic spray coating, screen-printing, and intense pulse light sintering, using the facilities at the Conn Center for Renewable Energy Research at the University of Louisville. In this study, prototype devices were fabricated on flexible ITO coated plastics. Sintering greatly improved the conductivity of the copper nano-ink cathode layer. We will explore this technique’s application to large-scale fabrication of solar cell devices in the future work.

The flow residence time in a scramjet combustor is of the order of a millisecond (10−3s). High energy density liquid fuels are the energy carriers of choice in scramjet engines, however liquid fuels must be atomized, evaporated and mixed before heat release by combustion can occur. Atomization, mixing and ignition require fnite time. Therefore it is important to study spray formation and its atomization in supersonic flows. Experiments are performed to study the spray formation from a water jet injected through a plain orifce atomizer with an exit diameter (d) of 1 mm, into a Mach 2.2 supersonic crossflow. High-speed shadowgraphy is performed using high-frequency nano-pulsed LASER as well as LED, to capture the local structures and spray features. The high-speed camera and nano-pulsed LASER is synchronized using a delay pulse generator. The pulse width of the LASER is kept at 8 and 14 ns, such that to freeze the spray features in time. The bow shock profles are observed to overlap between different momentum flux ratios (q) of the injected jet when shifted to the sonic point. The penetration height of the spray is evaluated using the upper spray boundary. The average spray trajectories are compared for three different momentum flux ratios. Wavelike disturbances are observed on the windward side of spray, which further develops into ligaments. Fundamental questions like ligament origin, speed and their breakup are addressed. The ligaments are present at spray boundary and observed to move with free stream flow near the injector. Further ligaments are tracked in successive shadowgraph images using cross-correlation technique to fnd their speed. The ligament speed is also compared for different momentum flux ratio and found to vary inversely with the momentum flux ratio. The wavelength associated with ligaments or surface waves is observed to increase linearly along the spray boundary irrespective of the momentum flux ratio. The ligament breakup is characterized using shear Weber number and wavelength is used as characteristic length scale. It is found that ligaments break due to shear from free stream flow. Small shocks (shocklets) are formed ahead of ligaments which are noted to increase the residence time. Shocklets also delay atomization of the ligaments.

碩士
國立中央大學
光電科學與工程學系
107
Volatile Organic Compounds, VOCs, are environmental source of pollution, which mainly emitted by using solvent in industry of painting. Nowadays, the workplace of painting is most in atmosphere, if we exposure in this place, it may damage the human body. In order to reduce the solvent used in painting, in other words, reduce the contact with VOCs, this study established a vacuum polymer coating system to improve the spraying environment and use solvent-free coatings to move the process of industrial coating in the atmosphere to vacuum. Recycling and exhausting systems are established in the vacuum chamber to reduce the possibility of contact with the human body; Using UV-curable materials, it is desirable to achieve a solvent-free UV-curing solution, reducing the viscosity use in a vacuum spray system, atomizing by pressure , achieving a coating effect with a minimum spray amount and rapidly curing into a film. Complete the sample and establish the process of the vacuum spray system. The study began with improvements in the materials and environment in the coating industry. The research will discuss in two parts: Part of the material: monomer trifunctional and monomer difunctional. The UV curing solutions formulated in a solvent-free form; the sprayed part has an experimental vacuum of 2×10-2 torr, and the coating material sprayed with a nozzle by a pressure. The substrate cosmetic bottle be coated into a liquid film, and then uses a high-speed camera observe the distribution of the spray during the spraying process. Thereafter, the liquid film irradiated by UV lamp formed a UV curing film. This experiment compares the effects of different viscosity on adhesion and atomization, and UV curing film formation, observes the atomization phenomenon, solves the film formation problem, and successfully produces a film with a smooth and non-porous film surface. In the heat curing and UV process on the market, there are lower temperature and less energy consumption. The UV illumination time of the coating is 50 seconds, the hardness can reach 6H or more, and the adhesion is the highest level of 5B, which is friendly environment and high. Efficiency (no solvent), low VOCs emissions process.

Thermal spray coatings applied with high velocity techniques produce dense, industrial quality coatings with strong adhesion and minimal decomposition. This thesis reports on investigations of splat-substrate interactions for both solid and molten splats. Specifically, individual particles were studied to see how the particle is altered during the spray coating process, how they bond to the substrate and the role of surface oxides. Investigations of NiCr particles high velocity air fuel (HVAF) thermally sprayed onto different materials found that soft substrates predominantly had deeply penetrating solid particles, whereas harder substrates resisted particle penetration and had a higher percentage of molten splats. This effect is caused by particle kinetic energy converted into heat during plastic deformation. The percentage of particle kinetic energy converted into heat is proportional to substrate hardness. It was also discovered that during the coating process the oxide is not removed or altered in composition, but becomes redistributed over a larger surface area due to the plastic deformation of the substrate. During this process, small scale redistribution and penetration of the oxide material by the incoming particle occurs. These results support the idea that successful bonding can occur only when the surface oxide on the substrate and on the coating material has been disturbed (for solid splats) or disrupted (for molten splats). To date, our knowledge of solid splat bonding processes within thermal spray coatings has been very subjective where mechanical and chemical bonding has been expected to contribute. In this thesis, the splat-substrate interface was investigated with focused ion beam (FIB) microscopy, cross-sectional SEM and cross-sectional TEM. For solid NiCr splat HVAF coatings, the discovery of interfacial formations, together with no evidence of chemical bonding across the particle-substrate interface suggest that mechanical bonding is the dominant bonding mechanism for solid splat coatings; where as chemical bonding only plays a role when splats and/or substrate become molten.
GNS Science

碩士
東南科技大學
機械工程研究所
106
The phenomenon of paint film formation on the surface of the paint will occur when the baking equipment of car sprayers reaches the operating temperature. This article is to compare the characteristics of car spray pieces by the flow field structure and effects of new/old spray chamber, as also to discuss and study the quality improvement of products quality. It examines the parameters such as brightness, hue, chroma, and film thickness. And compare the differences of the parameters in the brightness, hue, chroma and film thickness between the old and new spray chamber. The experimental data show that for the economic effect, the data of pearl-white color (070) in the old/new furnaces (lightness, hue, chroma) are quite different, and the data in the new spray chamber has excellent data. The pieces should be used as much as possible in the new spray chamber. The new furnace is unable to achieve the intended effect in dark-colored painted parts. At this time, the dark-colored painted pieces should be used as much as possible in the old spray chamber to reduce the load on the new spray chamber.

碩士
吳鳳科技大學
消防研究所
102
The principle of transformer is used by electromagnetic induction, altered to voltage and electric current, the immobile electric device to delivery the power of electric energy. So many of classification, the one of the transformer of oil immersion is commonly used in our country of electric power system.The study for the reason of breakdown in the transformer of oil immersion and fire risk, according to NFPA version to give a right way to keep in fire preventive facilities of water spray fire system to protect oil-filled transformer. This research on domestic and foreign laws and regulations related to research and analysis, and the actual to the substation site inspection, to understand the current situation and fire protection design to items substation fire safety, the proposed fire safety design a suitable oil-immersed transformers guidelines. Besides serving as reference for fire regulating authorities when they stipulate related regulations and laws and for designers during fire safety design, this study can also be referred to by Taipower when it tries to improve old and outdated fire safety equipment so as to enhance its ability to ensure fire safety and reduce potential crises as a result of power failure caused by fires, accordingly improving the business image of the company.

碩士
逢甲大學
機械與電腦輔助工程學系
103
In thesis, the use of water spray with mixed gas as dielectric fluid in EDM. In order to environment, it is well known that using kerosene as a dielectric fluid in EDM would evoke the undesirable problems, such as fire hazard. Therefore, using the way of water spray with mixed gas can prevent from the undesirable problems, and can reduct the carbon is benefit for the environment. This research studied on the hybrid EDM process by using water spray mixed gas with assisting ultrasonic vibration to explore the benefits of the developed hybrid process and improving the machining characteristics. The current focus on carbon reduction environmental trends, with considerable positive value. The developed hybrid process was adopted to determine the machining performance for SKD61 steel in the experimental investigation. Experimental results show that the hybrid discharge machining produced different processing results, due to the different gases were mixed in; In addition, the oxygen medium could facilitate the reaction within the machining gap to increase the exploding, melting effects, and the MRR obtained the highest values. The argon was an inert gas that could prevent the oxidation during the process, and the lower EWR could be obtained by using Argon as a medium in EDM process. This research experimental results showed that the hybrid discharge machining method could be assisted by the ultrasonic vibration, to efficiently improve reducing adverse slag discharge generation, and to recast layer which also effectively reducing the generation of surface patterns in the processing to get a better MRR and SR. Nowadays, the study of hybrid EDM system can be expanded at the application level complex discharge machining technology and meet the trend of green machining to meet the needs of manufacturing industry.

Studies on liquid atomization and spray formation in coaxial type atomizers are necessary to improve the performance of liquid propellant rocket engines. Recess ratio, expressed as the ratio of orifice recess length to inner orifice diameter, is one of the geometrical parameters that influences the characteristics of sprays discharging from coaxial atomizers. The present thesis reports an experimental investigation on the atomization and spray formation processes in recessed gas-centered swirl coaxial (GCSC) atomizers through the analysis of spray morphologies and measurements of size and velocity characteristics of spray droplets. A GCSC atomizer discharges a swirling liquid film and a gas jet via its annular and central orifices, respectively. Specific attention is given to elucidate the role of atomizer recess ratio of the GCSC atomizer on the characteristics of the spray that results from the breakup of the annular swirling liquid sheet by the central gas jet. The experiments are carried out in a spray test facility using water and air as the experimental fluids. The measurements of pressure drop across the atomizer orifices and fluid flow rates are made in the test facility. The images of sprays at different flow conditions are captured using the technique of backlighted shadowgraphy. Laser-based optical diagnostic systems (Phase Doppler Interferometry and Spraytec) are used to measure the size and velocities of spray droplets at different spatial locations of the spray below the atomizer exit. In the present study, the spray condition from the GCSC atomizers is expressed in terms of the gas-to-liquid momentum flux ratio, J. The quantitative variations of the spray cone angle and the streamwise breakup length of the annular liquid sheet, with the atomizer recess ratio, RR are presented for different GCSC atomizer flow conditions. An increase in RR of the GCSC atomizer results in a smaller spray cone angle and a longer sheet breakup length. A power law analysis of the experimental data shows that the sensitivity of the sheet breakup to J is more in case of higher recess ratio GCSC atomizers. The formation of a fully developed spray (spray free from ligament/droplet clusters and non-spherical droplets) in GCSC atomizers is quantified. For a given J, an increase in RR significantly reduces the cone angle of spray. The distance from the atomizer exit to the fully developed spray zone decreases with increase in J. Among the tested GCSC atomizers with varying RR (RR = 1, 2 and 3), a fully developed spray is rapidly seen for sprays discharging from the atomizer with RR = 2. The generation of more axially directed ligaments for the sprays discharging from higher RR (RR = 3) atomizer makes the fully developed spray to begin at a farther distance from the atomizer exit, compared to that from the atomizer with RR = 2. The spray from a recessed GCSC atomizer comprises two distinct spray morphologies: a central dense spray of finer droplets and an outer coarse spray of bigger droplets. The radial boundary between the two spray morphologies is marked by a jump in the mean drop size of the spray recorded along the radial direction. The mean drop size of the central spray decreases with increase in J, whereas that of the outer coarse spray is independent of J. The reduced spray cone angle and enhanced interaction in the sprays discharging from a high RR GCSC atomizer facilitate the migration of bigger droplets from the annular film breakup region to the central fine spray. The mean drop size recorded at the spray axis increases substantially with increase in RR from 2 to 3. The radial profiles of the mean velocities of spray droplets at different J are presented. The measured radial and tangential velocities of the spray droplets are two orders of magnitude smaller than that of their axial velocity, suggesting that the spray flow discharging from recessed GCSC atomizers is axially dominated. For the sprays with high J, the profile of the mean axial velocity of the spray droplets exhibits trends similar to that of a self-similar free gas jet.

Coupling of spray with the coherent structures of a highly turbulent flow has been a long-standing problem especially in the context of liquid fuel delivery systems in gas turbine combustors. The atomizer in a gas turbine combustor usually has one or more (radial/axial entry) air swirlers with a fuel nozzle being mounted centrally along the longitudinal axis of swirler. It is well known that swirling flows are highly three dimensional in nature and often induce multiple aerodynamically unstable modes whose frequencies are several orders of magnitude. The basic understanding of flow dynamics in gas turbine swirl cup is critical to achieving clean and efficient combustion in modern-day gas turbine combustors. In this work, we analyze the evolution of the hydrodynamic topology and consequent spray-flow interactions in a coaxial swirl injector assembly. The key results of the present work are discussed in four parts. In the first part, the global evolution and temporal dynamics of various vortex breakdown modes are discussed. Experiments are carried out for three sets of co annular flow Reynolds number 𝑅𝑒𝑎=4896,10545,17546. Furthermore, for each 𝑅𝑒𝑎 condition, swirl number ‘𝑆𝐺’ is varied independently from 0≤𝑆𝐺≤3. Three distinct forms of vortex breakdown namely, pre-vortex breakdown (PVB), central toroidal recirculation zone (CTRZ; axisymmetric toroidal bubble type breakdown) and sudden conical breakdown are explored in greater details. Energy ranked, and frequency resolved / ranked robust structure identification methods – POD, DMD respectively is implemented over instantaneous time resolved PIV data sets to extract the dynamics of coherent structures associated with each vortex breakdown modes. The dominant structures obtained from POD analysis suggest the dominance of KH instability (axial + azimuthal; accounts ~ 80 % of total TKE) for both PVB and CTRZ while the remaining energy is contributed by shedding modes. On the other hand, shedding modes contribute to the majority of the TKE in conical breakdown. The frequency signatures quantified from POD temporal modes and DMD analysis reveals the occurrence of multiple dominant frequencies in the range of ~ 10 – 400 Hz with conical breakdown. This phenomenon may be a manifestation of high energy contribution by shedding eddies in the shear layer. Contrarily, with PVB and CTRZ, the dominant frequencies are observed in the range of ~ 20 – 40 Hz only. In addition, the current work explores the hysteresis (path dependence) phenomena of conical breakdown as functions of Reynolds and Rossby numbers. It has been observed that the conical mode is not reversible and highly dependent on the initial conditions. In the second part, we have reported how the liquid sheet behaves in such swirling flows. The air flow rate across the swirler is progressively varied to probe the two-phase flow interaction dynamics across weak, transition and strong momentum coupling regimes. The liquid sheet breakup and gas – liquid phase interaction dynamics suggests strong one way coupling at higher MR values. The POD analysis implemented over the shadow images clearly delineates the superimposing of gas phase instabilities with liquid sheet. The breakup length scale and liquid sheet oscillations are meticulously analyzed in time domain to reveal the breakup dynamics of liquid sheet. Furthermore, the large-scale coherent structures of swirl flow exhibit different sheet breakup phenomena in spatial domain. For instance, flapping breakup is induced by counter rotating vortices in the flow field induced by vortex breakdown phenomenon. The breakup regime map is also constructed based to illustrate the various forms of breakup mechanism as a function of MR values. Finally, the ligament formation mechanism and its diameter, size of first-generation droplets are measured with phase Doppler interferometry (PDI). The measured sizes scale reasonably with KH waves. In the third part, the fundamental mechanisms of vortex-droplet interactions leading to flow distortion, droplet dispersion and breakup in a complex swirling gas flow field are discussed. In particular, how the location of droplet injection determines the degree of inhomogeneous dispersion and breakup modes have been elucidated in detail. The droplets are injected as monodispersed streams at various spatial locations like the vortex breakdown bubble and shear layers (inner and outer) exhibited by the swirling flow. Time-resolved particle image velocimetry (3500 frames/s) and high-speed shadowgraphy measurements are employed to delineate the two-phase interaction dynamics. These measurements have been used to evaluate the fluctuations in instantaneous circulation strength 𝛤′caused by the flow field eddies and resultant angular dispersion in the droplet trajectories 𝜃′. The droplet-flow interactions show two-way coupling at low momentum ratios (MR) and strong one way coupling at high momentum ratios. The gas phase flow field is globally altered at low air flow rates (low MR) due to the impact of droplets with the vortex core. The flow perturbation is found to be minimal and mainly local at high air flow rates (high MR). Spectral coherence analysis is carried out to understand the correlation between eddy circulation strength 𝛤′and droplet dispersion 𝜃′. Droplet dispersion shows strong coherence with the flow at certain frequency bands. Subsequently, proper orthogonal decomposition (POD) is implemented to elucidate the governing instability mechanism and frequency signatures associated with turbulent coherent structures. POD results suggest the dominance of KH instability mode (axial and azimuthal shear). The frequency range pertaining to high coherence between dispersion and circulation shows good agreement with KH instability quantified from POD analysis. The droplets injected at inner (ISL) and outer shear layer (OSL) show different interaction dynamics. For instance, droplet dispersion at OSL exhibits secondary frequency (shedding mode) coupling in addition to KH mode, whereas, ISL injection couples only at a single narrow frequency band (i.e. KH mode). Finally, we have analyzed the spray- flow field dynamics in the realistic injector configuration (i.e. high shear injector). High shear injector usually consists of a series of air swirlers (primary and secondary) with diverging flare at the exit and centrally mounted fuel nozzle. It should be noted that to precisely probe the characteristic features, experiments have been also conducted with independent primary and secondary swrilers. A parameter named dynamic pressure ratio (𝜉) is used to quantify the monemtum transfer pathways between primary and secondary swirler flow field across various test cases. The test cases which exhbit 𝜉<1 are identified as primary swirler dominant flow and for 𝜉≥1 are delineated as secondary swirler dominant flow. In other words, for 𝜉<1 momentum exchange will be take palce from primary to secondary swirler and vice versa for 𝜉≥1 condtion. . The results revealed that flow pertaining to the secondary swirler exhibits sharp narrowband frequency in the range of 0 – 60 Hz, whereas, the primary swirler flow exhibits wideband frequencies with distinct peaks at 200, 800 Hz. The POD analysis extended over combined primary and secondary swirler flows shows the persistence of wide band oscillations for the test cases pertaining to 𝜉<1 (i.e. Regime I). This is due to the dominance of primary swirler flow in the Regime I. On the contrary, the frequenncy signatures shift to sharp narrow band (0- 70 Hz) for the secondary swirler dominant cases (i.e. 𝜉≥1; Regime II). In addition, we have also reported the sensitivity of the high shear swirl cup with respect to the geometrical parameters. The geometric parameters like flow split ratio (γ) between primary and secondary swirler, geometric swirl number, area ratio (Δ), flow orientation (i.e. co and counter rotation), exit flare angle (ϴ) etc are considered. The length scale (𝑊𝐷𝑓⁄), which embodies the radial extend of the recirculation zone is used as criteria to distinguish the various test cases. It is found that, the magnitude of (𝑊𝐷𝑓⁄) is governed by near field swirl number (SN10) and Reynolds number for the cases where SNgeo, γ, Δ have been varied. Here, SN10 represents the experimentally measured swirl number at ~ 10mm from the exit of swirl cup. On the other hand, for the cases with variations being θ and flow orientation, (𝑊𝐷𝑓⁄) founds to be only a function of near field swirl number f (SN10). Next, the spatial distribution of the spray perceived from patternation studies shows a linear relationship with the magnitude of 𝑊𝐷𝑓⁄. It is interesting to note that, though the spatial spread of the spray scales with 𝑊𝐷𝑓⁄, however, the spatial uniformity and measured droplet remains insensitive to the test variables.

In rotary fuel injection systems, the fuel is atomized with the help of centrifugal force provided by the rotation of the injector. The rotational power can be directly provided by the shaft of a gas turbine, which can go up to the rotational speed of 100000 RPM. Therefore, there is no need for extra systems such as a fuel pump or a pressure chamber. This makes the rotary injection system very compact and suitable for small gas turbines. Also, the injection orifice diameter in these systems is large enough to be used for high viscosity and slurry fuels, as small diameters can cause clogging. There is a strong need to study and understand the spray characteristics of these types of injectors to adapt combustors for challenging fuels such as high energetic fuels containing boron nanoparticles. Also, there is a need to develop correlations for improved prediction of spray characteristics. The present work is motivated by the demand for high-energy-density fuels, such as fuel slurries. In the first part of the study, the spray characteristics of rotary atomization were investigated experimentally. A high-speed rotating facility has been developed in which a 1.5-kW electric motor was used with a maximum operating speed of 40000-RPM. The spray characteristics of pure water, water-ethanol blend, and water-glycerol blend were investigated to understand the variation of liquid physical properties such as viscosity and surface tension on spray characteristics. It is shown that at lower rotational speeds, the effect of viscosity and surface tension are evident, but at higher speeds, the inertial effects dominate. To understand the spray characteristics from slurry fuels, aqueous colloidal silica nanoparticle suspension with different nanoparticle loading is used. Results showed that even with the particle loading, the variation in SMD is the function of liquid physical properties and does not have a unique dependency on particle loading. The jet visualization and spray characteristics such as breakup length and droplet size were measured using the shadowgraphy technique. For droplet size measurements, a long-distance microscope (LDM) attached to a CCD camera with laser-induced fluorescent backlight is used. The Spray patternation has been studied with water by passing a laser sheet to the spray and capturing scattering images. The images of the liquid flow inside the orifice were captured using a transparent atomizer made of acrylic. The second part of the study comprises of analyzing the liquid flow physics. A novel non-dimensional number has been derived to account for the Coriolis force induced inside the orifice. From the images of liquid flow inside the orifice, it has been shown that the flow physics can be explained using this non-dimensional number. There are eight different parameters affecting the spray characteristics, viz. viscosity, density, surface tension, liquid feed rate, atomizer rotational speed, atomizer diameter, orifice diameter, and orifice length. A new empirical correlation has been established to account for the variation in all these parameters, and this correlation is shown to be very effective over a wide range of parametric space. The last part of the study involves the design proposal of a novel orifice structure, which comprises of two stages; also, the feasibility of the design was investigated.

The stringent pollution and emission norms due to the present climate change and global warming have pushed industries to meet these norms and cut down their emission levels. In the same pipeline, the aviation industries do not remain untouched. The emissions from aircraft engines burning fossil fuel, NOx, CO, unburnt hydrocarbon, etc., affect the atmosphere's upper layer temperature and air quality. These increasing number of air-transport demands and strict emission norms have forced the aviation industry to develop a next-generation aero-engine that can burn fossil fuel more efficiently and meet the emission norms. Liquid fuel is a major power source for most power-generating units, such as land-based and air-based gas turbine combustors, rocket engines, industrial burners etc. The high energy density per unit volume for liquid fuel makes it a better candidate than gaseous fuel for an air-breathing engine/combustor. The extraction of power from the liquid fuel involves various stages such as fuel injection, its atomization in smaller droplets, oxidizer and fuel droplet mixing and then ignition of this fuel-oxidizer mixture. The fuel injection process and technique are key to enhancing the gas turbine combustion performance and reducing the emission levels to meet the pollution norms in upcoming eras of aviation transport. However, optimization of the fuel injection system remains a key challenge, especially in liquid-powered gas turbine engines. Modern-day aircraft combustors utilize high shear fuel injectors that consist of multiple arrangements of swirlers along with a concentric fuel nozzle that generates coflowing swirling air to enhance atomization quality and get a homogeneous level of fuel-air reactant mixture prior to combustion. The key observations of the current work are discussed in four parts. In the first part, we have designed, developed and characterized the performance of a new class of high shear injector (HSI). The benchmark to evaluate the performance of HSI are Spray flow field, Droplet size distribution, and droplet dispersion across a wide range of air-to-liquid mass ratios (ALR; 4-14). In the first part of the study, the influence of the injector’s geometrical features over the time-averaged and dynamical spray characteristics are examined using high fidelity laser-diagnostics technique (high-speed PIV). These features are swirl numbers (SN_Prim), airflow split-ratio(γ), area ratio(Δ), flare angle(θ) and relative flow orientation of primary and secondary swirlers (co and counter-rotation). A Simplex pressure-swirl fuel nozzle is mounted at the center of the injector to deliver the liquid. The non-dimensional length scales (radial; W/Df and axial; L/Df) are used to distinguish the test cases. W/Df and L/Df are governed by nearby swirl number SN5 for both counter and co-rotation swirl configuration. Here, SN5 is the experimental swirl number calculated 5mm from the exit. The length scales, W/Df and L/Df, are more sensitive to the split-ratio of primary and secondary swirlers, flare angle, and it’s mixing length. The spray droplet size and spatial uniformity are insensitive to the test variables. Further, dominant dynamic spatial modes changes with a change in W/Df of the recirculation zone and the oscillation frequency of the most dominating modes shifts to a lower value with increasing W/Df. Simplex pressure-swirl fuel nozzle and dual orifice fuel nozzle are commonly used for fuel delivery at the center of the fuel injector/atomizer in the present-day gas turbine combustor. However, these fuel-nozzle have limitations such as hollow-cone liquid sheets collapsing at higher pressure, prone to plugging of narrow passages with contaminations over time, and high delivery pressure requirement. The second part of the work addresses these issues by replacing the same with a discrete liquid-jet fuel nozzle with a simple orifice design and low injection pressure. The performance of a high shear injector with a discrete liquid – jet mounted at the center is evaluated and compared to the performance achieved with a high shear injector using a simplex pressure-swirl fuel nozzle. The comparison shows the potential of a discrete liquid -jet fuel nozzle to replace the simplex pressure-swirl fuel nozzle with the proper design of high shear injector. The injectors have excellent atomization capability along with superior azimuthal distribution of spray. The Sauter-Mean Diameters (SMD) across all the test cases are in the range of 9-30µm,15-37µm, 15-50µm and 23-75µm at ALR 14.1, 9.44, 7.08, and 4.72 respectively. Further, the Std. Deviation of azimuthal spatial uniformity in an azimuthal plane is below 6 percent of the mean. A high shear injector consists of multiple swirler that produce swirl flow, and swirl flow is generally characterized by swirl number (SN). Above particular SN, the swirl flow creates a negative axial pressure gradient at the central axis which manifests a vortex breakdown bubble (VBB), also called the recirculation zone or central toroidal recirculation zone (CTRZ). The CTRZ help to stabilize the flame inside the gas turbine combustor. However, the onset of the vortex breakdown bubble is associated with a self-excited instability known as precessing vortex core oscillation. The PVC oscillation in a swirl flow-based combustor aids the thermoacoustic instability, resulting in severe hardware damage and poor emission characteristic of the engine. The third part of the work addresses the suppression of PVC oscillation to avoid the thermoacoustic -instability by modifying the fuel nozzle mounted at the center of the injector. A dummy cylindrical post is attached to the fuel nozzle that acts as the centerbody. The work shows the intermittent or absolute suppression of PVC oscillation with proper design of centerbody and variation of flow Reynold number. The diameters of the centerbody considered are Dc = 7;9 and 11mm. The results further demonstrate the suppression of loud whistle-like acoustic sound with the suppression of PVC oscillations in the flow. Considering the current global warming scenario and emission norms, the fourth part of the work addresses the soot formation study using Laser-induced Incandesce Imaging (LII) in a turbulent non-premixed ethylene swirl flame at a constant global equivalence ratio, ∅global=0.55 in a high shear injector. First, the impact of the split-ratio of primary and secondary swirler on soot formation is estimated at the given Reynolds number and pressure conditions for constant ∅global, which shows that a 60/40 swirl cup produces lower soot than a 40/60 swirl cup. Further, at constant pressure and ∅global=0.55, soot volume fraction reduces from ~4 ppm to ~0.8 ppm by increasing the Reynolds number from Re~5000 to Re~ 15000, and at Re ~20000, no soot is observed. At constant exit bulk velocity and constant ∅global=0.55, the soot volume fraction scales-up with pressure as p2.1 on log-log plots. Further, pressure increment increases the soot formation at a constant Re number. Overall, it is observed that pressure endorses soot formation. In addition, a large formation of soot particles is majorly observed in the annual jet’s region of the swirl flow field.

Thermal spray is a well established technology that is commonly used in the aerospace and automotive industries. This thesis reports on the effect that substrate surface chemistry, morphology and temperature has on the morphology of PEEK single splats on aluminium substrates. PEEK single splats were deposited by HVAF and plasma spraying on aluminium substrates with 6 different pretreatments. Substrates were either sprayed at room temperature, or 323°C, and a subset of substrates was held at incremental temperatures up to 363°C. HVAF deposited splats on room temperature substrates showed sensitivity to surface chemistry, with increased circularity and area associated with low levels of hydroxide and chemisorbed water on the aluminium surface. Substrates held at 323°C were more sensitive to substrate morphology, where rough surfaces resulted in decreased circularity and area apparently independent of surface chemistry. Substrate temperature trials revealed a significant step in the results, equating to greater circularity, and lower splat area, perimeter and Feret diameter. This step occurred between 123°C and 163°C, the two points bracketing the glass transition temperature of PEEK (143°C). This result was due to the relaxation of splats deposited on surfaces above 143°C, whilst splats on cooler substrates quench through the glass transition and do not relax. PEEK splats deposited by plasma spray on room temperature and 323°C substrates showed sensitivity to the amount of hydroxide and chemisorbed water present on the aluminium substrates, with low levels resulting in more circular and larger area splats. Plasma splats did not show the same temperature effects as HVAF splats, thought to be due to the more molten state of plasma splats upon impact compared to the HVAF splats. The primary conclusions reached were that plasma sprayed polymers were sensitive to surface chemistry, and that as such the surface chemistry of a substrate should be considered when forming plasma spray polymer coatings. It was also concluded that the kinetic energy of particles in HVAF thermal spray contributed significantly to the thermal energy of a particle on impact, allowing for improved splat properties without overheating the particles in flight. Finally it was concluded that substrate temperature is far more important for HVAF thermal spray of polymers than plasma spray of polymers, but that it improves splat properties for both techniques.

Liquid jets in cross flows (JICF) have been an important part of spray research in the last few decades owing to the wide spectrum of applications ranging from agricultural sprays to aircraft gas turbine engines. However, the current study focuses on the liquid jet injected in swirling cross flows (JISCF), which is more specific to aircraft gas turbine engines. Since this configuration is relatively new in the research domain, various closely related problems are investigated for a better understanding of the spray dynamics. To begin with, the classical-JICF configuration is used to study the influence of liquid jet exit conditions on the resultant spray behaviour. The liquid jet exit velocity profiles are varied by altering the L/D ratio of the plain orifice nozzles between 10 and 100. While the smaller L/D nozzles produce laminar jets, the larger L/D nozzles allow the liquid to transition to fully turbulent conditions. Laser diagnostics are employed to measure the spray trajectory and drop sizes. It is observed that the laminar jets penetrate further into the cross flow as compared to the turbulent jet counterparts for similar flow conditions and produce larger droplets. This is attributed to the turbulent jet undergoing early breakup due to the inherent instabilities in the jet. This learning is then carried forward to experimental studies on liquid jet in swirling cross flow (JISCF) by employing longer L/D nozzles to promote better atomization. The swirl flow is generated with the aid of 3-D contoured axial swirl vanes with 30º and 45º exit angles and compared with baseline no-swirl case. The resultant spray shows interesting and counter-intuitive behaviour under the influence of swirl flows. While the centrifugal forces are expected to carry the droplets radially outward, the aerodynamics in the annular space has the opposing effect in the ABSTRACT ii wake regions of the jet. The drop size measurements also reveal the presence of coalescence among the droplets, which was not observed to be significant in classical JICF studies. Higher swirl numbers also caused the spray to bifurcate resulting in the larger droplets impinging on the outer wall much earlier as compared to the lower swirl conditions, whereas droplet impingement on the wall is not observed for no-swirl conditions. The JISCF problem is also studied computationally using an open source code, Gerris. As part of a validation study, secondary breakup is first simulated at a realistic density ratio of 1000:1. The Weber numbers were varied to cover the known regimes of breakup. Bag-and-stamen breakup, multi-bag breakup and shear breakup were captured with a close match to experimental results. The JISCF simulations are then carried out using similar annular geometry as that of the experiments for a density ratio of 180:1 owing to inherent limitations existing in the multi-phase numerical methodology. The spray characteristics such as trajectory and drop size distributions are analysed. The spray trajectory is observed to move radially outwards with increasing swirl numbers. The drop size measurements again indicate coalescence as the SMDs are observed to increase along the downstream direction. The numerical model is observed to effectively predict the qualitative behaviour of the spray in swirling cross flow. Overall, the present study helps further our understanding of the spray characteristics produced by liquid jets in swirling cross flows with combined efforts on experimental and numerical fronts.

Heavy fuel oil (HFO) is extensively used in industrial burners and marine engines. HFO droplet combustion gives rise to carbon particulates generated by pyrolysis, which are called cenospheres. There is a current hypothesis that ‘one HFO droplet generates one cenosphere’, though there is no strong experimental evidence in support of this hypothesis. The present research deals with experimental study of HFO droplet combustion and investigates effect of HFO spray characteristics on carbon particulate emission in a spray combustion environment. A new research burner is designed to study combustion characteristics of a sparse HFO spray in a controlled high temperature environment (800 K – 1300 K). A nebulizer system generates a sparse spray of HFO droplets which enables fundamental studies on droplet combustion. Initially, spray evaporation studies are performed with standard liquids such as n-decane and n-dodecane. The droplet evaporation rate constant Kevap data derived from experiments are found to be in good agreement with those from literature. The research burner is then utilized to study HFO spray combustion and particulate formation. A novel Laser-induced fluorescence (LIF) based optical technique is developed to optically image HFO droplets in the high temperature spray flame environment. Based on this data, fuel injection parameters are optimized to achieve spray characteristics with Sauter Mean Diameters (SMD) ranging from 24-μm to 53-μm. Soot measurements are carried out in the HFO spray flames using the Laser Induced Incandescence (LII) technique to identify soot formation and oxidation zones. Soot is observed to be produced at lower flame heights and subsequently oxidized along the spray flame height. It is observed that a reduction in SMD from 53-μm to 24-μm leads to a 58% reduction in soot 5 formation. To investigate the impact of HFO spray characteristics and environment temperature on droplet pyrolysis, the cenosphere sizes are measured using an aerodynamic particle sizer. With change in SMD from 53-μm to 24-μm, a drastic reduction (~90%) in cenosphere emission density (particles/cm3) is observed. It is also observed that higher temperatures ranging from 1073 K to 1223 K are favorable for cenosphere reduction. The morphological study of cenospheres indicates that these are nascent coke particles generated at the end of the droplet combustion phase. The results seem to indicate that the ‘one droplet generates one cenosphere’ theory is not applicable for smaller droplets. The data is further analyzed to establish the existence of a critical diameter of HFO, which undergoes complete combustion in the droplet combustion phase without generating a solid coke particle. In other words, if a HFO spray consists of droplets whose diameter is below this critical value, the particulate emissions can be nearly zero. From the experimental data, the critical droplet diameter is found to be in range of 18-μm to 23-μm for the medium grade of HFO used. Keywords: Heavy fuel oil (HFO), Spray, Droplets, Combustion, Particulate emission, Soot, Cenospheres, Laser Induced Incandescence, Laser Induced Fluorescence

The modelling of spray-wall interaction encountered in engine combustors relies heavily on studies of single drop impact on heated solid surfaces. In the present thesis, the impact of a single fuel drop on a hot, smooth stainless-steel surface is experimentally examined using high speed visualization. Four different fuels of significantly varying physical properties (heptane, decane, Jet A-1 and diesel) are considered. The condition of impacting fuel drop, characterized in terms of Weber number (We), is varied in the range 27-903. The temperature of the solid surface (Ts) is varied in the range 25-410 oC encompassing all heat transfer regimes from convection to film boiling. The analysis of fuel drop impact on an unheated surface (Ts = 25 oC) reveals that the lamella spreads sluggishly even beyond the end-point of the inertia driven primary spreading phase. This new phase of fuel impact dynamics is termed in the present study as ‘post-spreading’. The spreading rate of the fuel drops in the post-spreading phase is dependent on We and is much lower than that dictated by Tanner’s Law for spontaneous drop spreading. For the impact of fuel drops on hot stainless-steel surfaces, regime maps with We on the X-axis and Ts on the Y-axis, highlighting various heat transfer regimes and morphological outcomes are constructed. Quantitative trends on the variation of maximum spread factor (max) for the fuel drops on the hot surface are presented. With the help of existing theoretical models for predicting max, it is concluded that viscosity of the fuel plays a major role in the determination of temperature dependency of βmax. For drop impact in film evaporation regime, an empirical model for max involving an explicit surface temperature term in the form of normalized value T* is formulated from the experimental data and is found to agree well with similar data from literature. Further details of fuel drop impact dynamics on the hot surface in other heat transfer regimes including contact boiling and Leidenfrost regimes are presented.

Indiana University-Purdue University Indianapolis (IUPUI)
Fabrication and analysis of Copper Indium Gallium di-Selenide (CIGS) nanoparticles-based thin film solar cells are presented and discussed. This work explores non-traditional fabrication processes, such as spray-coating for the low-cost and highly-scalable production of CIGS-based solar cells. CIGS nanoparticles were synthesized and analyzed, thin CIGS films were spray-deposited using nanoparticle inks, and resulting films were used in low-cost fabrication of a set of CIGS solar cell devices. This synthesis method utilizes a chemical colloidal process resulting in the formation of nanoparticles with tunable band gap and size. Based on theoretical and experimental studies, 100 nm nanoparticles with an associated band gap of 1.33 eV were selected to achieve the desired film characteristics and device performances. Scanning electron microcopy (SEM) and size measurement instruments (Zetasizer) were used to study the size and shape of the nanoparticles. Electron dispersive spectroscopy (EDS) results confirmed the presence of the four elements, Copper (Cu), Indium (In), Gallium (Ga), and Selenium (Se) in the synthesized nanoparticles, while X-ray diffraction (XRD) results confirmed the tetragonal chalcopyrite crystal structure. The ultraviolet-visible-near infra-red (UV-Vis-NIR) spectrophotometry results of the nanoparticles depicted light absorbance characteristics with good overlap against the solar irradiance spectrum. The depositions of the nanoparticles were performed using spray-coating techniques. Nanoparticle ink dispersed in ethanol was sprayed using a simple airbrush tool. The thicknesses of the deposited films were controlled through variations in the deposition steps, substrate to spray-nozzle distance, size of the nozzle, and air pressure. Surface features and topology of the spray-deposited films were analyzed using atomic force microscopy (AFM). The deposited films were observed to be relatively uniform with a minimum thickness of 400 nm. Post-annealing of the films at various temperatures was studied for the photoelectric performance of the deposited films. Current density and voltage (J/V) characteristics were measured under light illumination after annealing at different temperatures. It was observed that the highest photoelectric effect resulted in annealing temperatures of 150-250 degree centigrade under air atmosphere. The developed CIGS films were implemented in solar cell devices that included Cadmium Sulfide (CdS) and Zinc Oxide (ZnO) layers. The CdS film served as the n-type layer to form a pn junction with the p-type CIGS layer. In a typical device, a 300 nm CdS layer was deposited through chemical bath deposition on a 1 $mu$m thick CIGS film. A thin layer of intrinsic ZnO was spray coated on the CdS film to prevent shorting with the top conductor layer, 1.5 μm spray-deposited aluminum doped ZnO layer. A set of fabricated devices were tested using a Keithley semiconductor characterization instrument and micromanipulator probe station. The highest measured device efficiency was 1.49%. The considered solar cell devices were simulated in ADEPT 2.0 solar cell simulator based on the given fabrication and experimental parameters. The simulation module developed was successfully calibrated with the experimental results. This module can be used for future development of the given work.

Air-suspension particle coating is a process by which thin coatings are applied to powder particles. The coatings can be formulated to act as permeable barriers to increase powder shelf-life or to impart controlled release character. The ultimate objective of a coating operation is to produce individual particles, each with a well-controlled, even coating. This project was focused on the air-suspension coating of fine powders of ~100 µm in diameter for the dairy industry. Despite the widespread use of the technology in the pharmaceutical industry, its use in the food industry has been limited. Little is known about the fundamental mechanisms, and so published work to date is product and equipment specific and is statistical in the way the experimental design and analysis has been approached. This 'black box' approach is time consuming and costly. Better methods based on an understanding of the physical and chemical mechanisms are needed to deal with the numerous products and constantly changing formulations typical of the dairy industry. This thesis proposes a new approach to air-suspension particle coating research. The basis of this 'micro-level process approach', is to deconvolute the complex coating process into smaller manageable parts based on classical physical phenomena for which descriptions already exist. The thesis identifies and develops an understanding of the key micro-level processes controlling coated product quality and process performance. Four were selected for further study: drying, droplet impact and spreading, and stickiness which encompasses the two key micro-level processes of droplet impact and adherence and inter-particle agglomeration. They were studied separately to deconvolute the variable effects and interactions. Kinetic data were collected for the drying droplets containing maltodextrins, whey protein isolate and gum arabic. A mathematical model, based on 'ideal shrinkage' was developed to predict the drying kinetics of single droplets with particular interest in the development of the surface glass transition temperature. The model accurately predicted the kinetics until significant morphological changes occurred in the droplet. To better predict the kinetics late in the drying process, the droplet radius was set to be constant at a time based on the surface proximity to the surface glass transition temperature (critical X concept). This was done to arrest droplet shrinkage in line with experimental observations and to more accurately depict the drying of high molecular weight, amorphous glass forming polymers. After this point, a new flexible calculation scheme was used to better predict the variation in internal droplet structure as either a dense, 'collapsed shell' structure or a 'dense skin-porous crumb' structure. Further study should focus on the surface and internal droplet structure (porosity and mechanical integrity) development during drying, particularly the conditions leading to the arresting of the droplet radius and the subsequent rate of skin thickness progression. The critical X concept was used to make industrial-scale predictions of the optimum drying conditions that ensure maximum droplet impact and adherence efficiency and minimum inter-particle agglomeration in a Würster-style coating operation. This enabled the prediction of two key design parameters, the nozzle distance from the powder impact point and the Würster insert height. The span in design parameters showed that there is significant opportunity for design optimisation based on the critical X concept. A probe tack test was used to map the level of stickiness of droplets of different coating materials as they dried. As skin formation progressed, the stickiness passed through a maximum, in most cases to arrive at a point at which the droplet was no longer sticky at all (non-adhesive state). The maximum point of stickiness represents the ideal state to ensure successful droplet-substrate impact and adherence. The minimum point of stickiness represents the ideal state to prevent unwanted inter-particle agglomeration. The time interval between the onset of stickiness and the non-adhesive state was particularly dependent on the addition of plasticisers, but also on the formulation and the drying air conditions. Future work should look to establish a possible relationship between the surface glass transition temperature and the probe tack test stickiness measurements. The impact and spreading of droplets containing maltodextrin DE5 on to solid anhydrous milkfat was studied using a high speed video camera. It was found that the final spread diameter was able to be fixed close to the maximum spread diameter by using surfactants, thus avoiding significant recoil. Because existing literature focuses on predicting the maximum spread diameter, this work defines a need for adequate prediction methods for the final spread diameter, as this is the significant parameter in coating applications. Formulation and operating guidelines were established to independently optimise each micro-level process. These were used in a series of population based coating experiments in a pilot-scale Würster coater. This study highlighted the limited flexibility of the standard 'off-the-shelf' Würster coating apparatus for the coating of fine sized dairy powders. Because of this, the validation of the guidelines were inconclusive and optimisation could not be carried out. Further validation work is required on a custom-built apparatus for dairy powders. This work has advanced the fundamental knowledge of the coating process and is independent of material, equipment and scale. This knowledge, based on physical and chemical mechanisms, can be used to develop coating formulations and identify optimum process conditions for successful coating in less time and at less expense than is current practice. The next step is to put the guidelines into practice and craft the engineering of a continuous coating apparatus for dairy powder applications.

Terrorism has become a serious threat in the world, with bomb attacks carried out both inside and outside buildings. There are already many unreinforced masonry buildings in existence, and some of them are historical buildings. However, they do not perform well under blast loading. Aiming on protecting masonry buildings, retrofitting techniques were developed. Some experimental work on studying the effect of retrofitted URM walls has been done in recent years; however, these tests usually cost a significant amount of time and funds. Because of this, numerical simulation has become a good alternative, and can be used to study the behaviour of masonry structures, and predict the outcomes of experimental tests. This project was carried out to find efficient retrofitting technique under blast loading by developing numerical material models. It was based on experimental research of strengthening URM walls by using retrofitting technologies under out-of-plane loading at the University of Adelaide. The numerical models can be applied to study large-scaled structures under static loading, and the research work is then extended to the field of blast loading. Aiming on deriving efficient material models, homogenization technology was introduced to this research. Fifty cases of numerical analysis on masonry basic cell were conducted to derive equivalent orthotropic material properties. To study the increasing capability in strength and ductility of retrofitted URM walls, pull-tests were simulated using interface element model to investigate the bond-slip relationship of FRP plates bonded to masonry blocks. The interface element model was then used to simulate performance of retrofitted URM walls under static loads. The accuracy of the numerical results was verified by comparing with the experimental results from previous tests at the University of Adelaide by Griffith et al. (2007) on unreinforced masonry walls and by Yang (2007) on FRP retrofitted masonry walls. To study the de-bonding behaviours of retrofits bonded to masonry, and find appropriate solution to protect certain masonry walls against blast loading, various retrofitting technologies were examined. The simulation covers explosive impacts of a wide range of impulses. Based on this work, pressure-impulse diagrams for different types of retrofitted URM walls were developed as a design guideline for estimating the blast effect on retrofitted masonry walls. The outcomes of this research will contribute to the development of numerical simulation on modelling retrofitted URM walls, improving the technique for explosion-resistant of masonry buildings, and providing a type of guideline for blast-resistant design.
http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1349719
Thesis (M.Eng.Sc.) - University of Adelaide, School of Civil, Environmental and Mining Engineering, 2009

The injector faceplate of a liquid propellant rocket engine is comprised of numerous single-element atomizers to inject propellants into the engine thrust chamber. The sprays from these single-element atomizers interact and mix, and then develop a combined spray. The present study investigates the characteristics of combined spray from a multi-injector assembly discharging three identical hollow cone swirl sprays arranged in an equilateral triangular configuration. The experiments are carried out in a spray test facility using water as the experimental liquid for different values of pressure drop (ΔPl) across the atomizers. The images of combined spray, captured using the technique of backlighted shadowgraphy, are used to deduce quantitative details of spray interaction behavior, and laser-based optical diagnostic systems (Phase Doppler Interferometry, and Spraytec) are used to record droplet characteristics of the combined spray. A mechanical patternator is used to describe the evolution of liquid mass distribution of the combined spray at different values of axial distance (Z) from the atomizer exit. The interaction process between the individual sprays influences spray width and liquid sheet breakup characteristics of the combined spray, particularly for sprays with low ΔPl. The interaction zones of the combined spray are marked by three lobes of high liquid mass flux, which develop asymmetry in the spray cross section perpendicular to the spray axis. It is showed quantitatively that the level of asymmetry in the combined spray decreases with increase in Z. The analysis of droplets characteristics of the combined spray reveals the presence of droplet coalescence for sprays with low ΔPl and droplet shattering for sprays with high ΔPl, which highlights droplets collision effects caused by the interaction and mixing of individual sprays in multi-injector thrust chamber.

In this work, studies have been conducted on sprays of methanol and its emulsions with diesel towards assessing the potential of methanol as an alternative fuel for IC engines. Methanol can be used in compression ignition engines as a methanol-in-diesel emulsion, and in spark ignition engines as a direct gasoline-substitute. Evaporating spray characteristics of methanol-in-diesel emulsions and pure methanol are studied in a high-pressure chamber with optical access. In the first part of the study, a comparison between two measurement methods (DBI and scattering) along with two post-processing methods (line-fit and threshold) to measure liquid length of a diesel spray is presented. The second part of the study involved assessing the stability of methanol-in-diesel emulsions with conventional surfactants such as sorbitan monooleate (Span-80®) and polyoxyethylene sorbitan monooleate (Tween-80®). The hydrophilic-lipophilic balance (HLB) values of the surfactant were varied from 7 to 15 to investigate the role of the surfactant on stability of the macroemulsion. It was observed that macroemulsions with up to 10 wt.% of methanol were stable. The macroemulsion with an HLB value of 10 gave the best stability results. In the third part of the study, the emulsion sprays were characterized in a constant volume chamber at injection pressures of 500 bar, 1000 bar, and 1500 bar in an inert atmosphere of nitrogen at 50-bar and 900-K. Interestingly, the liquid-length of the methanol-in-diesel emulsion spray with 10 wt.% of methanol using a mixture of Span-80® and Tween-80® as a surfactant is higher by around 25% as compared to that of the diesel spray, even though methanol is far more volatile than the components of diesel. This is attributed to the higher boiling point of the surfactant used, as confirmed by experiments with a low boiling point surfactant, i.e., 1-dodecanol, and recent observations from the literature. Next, microemulsions of diesel-methanol were produced by using various surfactants such as 1-dodecanol, pentanol, and butanol. Among these, 1-dodecanol was chosen as the most suitable surfactant for the microemulsion owing to its ability to create microemulsions with up to 25 wt.% of methanol, and its high cetane number. The evaporating spray liquid-length is observed to be insensitive to the methanol percentage in the emulsion when 1-dodecanol is used as the surfactant. The fourth part of the study focused on evaluating whether the phenomenon of micro-explosion in emulsion fuel droplets occurs at engine-relevant conditions of pressure and temperature. In a first-of-its-kind observation, emulsion droplets in the size range of 50 to 150-µm in a high-pressure, high temperature (50 bar, 900 K) environment did not exhibit the phenomenon of micro-explosion even up to 11 milliseconds, which is close to the timescales of relevance in practical engines. This is possibly because these timescales are not sufficient for phenomena such as coalescence of the dispersed phase and internal bubble formation to occur, which are normally precursors to micro-explosions. In the fifth part of the study, pure methanol sprays were characterized at injection pressures of 200 bar, 300 bar, 400 bar, and 480 bar in an inert atmosphere of nitrogen at three engine-relevant conditions. Data generated on liquid and vapour penetration at these conditions highlight the effect of the surrounding gas temperature and density on the spray physics. In the last part, a validated computational spray model of methanol sprays is developed using a commercial CFD solver, namely, CONVERGE-CFD. Overall, the data generated in the present work is expected to aid engine designers in adapting both compression ignition and spark-ignition engines for methanol fuel.

Studies on the atomization of sustainable aviation fuels (SAF) from aircraft engine atomizers are essential to replace the present fossil type jet fuel to counter the rise in aviation-caused CO2 emissions in the atmosphere. The characteristics of spray droplets resulting from the breakup of liquid film in atomizers are crucial for the description of primary atomization process and combustion dynamics in aircraft engines. The thesis investigates the atomization of camelina- and jatropha-derived drop-in aviation biofuels from a hybrid airblast atomizer (HAA) used in aircraft jet engines. The main focus of the study is on the evaluation of spray droplet characteristics in the near-region of liquid film breakup. The experiments are carried out in a spray test facility. The images of sprays at different flow conditions are captured using backlighted shadowgraphy technique. The measurements of spray droplet characteristics are obtained using phase Doppler interferometry (PDI) and Spraytec at different spatial locations of the spray below the atomizer exit. In the first part of the study, extensive experiments of liquid atomization from the HAA using water are conducted. The size and velocity characteristics of droplets resulted from the liquid film breakup in the simplex swirl atomizer (central atomizer in the HAA), measured within millimetre distance from the actual location of the liquid film breakup, are analysed. The mean axial velocity of the spray droplets measured at the film breakup point is independent of droplet size, which is different from the correlation characteristics of the spray droplets observed in other regions of the spray. The linear film breakup theory overpredicts Sauter mean diameter (SMD) of the spray measured at the breakup point significantly, and an existing scaling law for the determination of volume median diameter of the spray captures the present experimental trend of the droplet size recorded at the breakup point. The droplet size distribution measured at the breakup point is well described by a Gamma distribution with index parameter n governing the corrugation features of ligaments formed in the film breakup. Further, by using the self-similarity analysis of droplet size and velocity, the demarcation region between the near- and far-region of liquid film breakup in the spray is established. A systematic comparison of spray characteristics in the near- and far-region of the liquid film breakup is reported. In the second part of the study, the atomization characteristics of water and drop-in aviation biofuel sprays from the HAA is carried out. The droplet characteristics in the near-region of liquid film breakup are obtained at a distance 19 mm from the atomizer exit using Spraytec. The present droplet size data compare well with the predictions obtained using previously reported empirical correlation with a modified proportionality constant. The spray characteristics of the aviation biofuel sprays from the HAA are almost same as that of the standard fuel (Jet A-1) spray, which confirms the drop-in behavior of the chosen alternative fuels. By using the present experimental data of HAA spray from six experimental fluids, an empirical correlation for the estimation of nondimensionalized SMD in terms of liquid and gas Weber numbers and Ohnesorge number is proposed