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Artykuły w czasopismach na temat "Spray and Atomization"
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Panão, Miguel. "Ultrasonic Atomization: New Spray Characterization Approaches". Fluids 7, nr 1 (7.01.2022): 29. http://dx.doi.org/10.3390/fluids7010029.
Pełny tekst źródłaStreszczenie:
In particle engineering, spray drying is an essential technique that depends on producing sprays, ideally made of equal-sized droplets. Ultrasonic sprays appear to be the best option to achieve it, and Faraday waves are the background mechanism of ultrasonic atomization. The characterization of sprays in this atomization strategy is commonly related to the relation between characteristic drop sizes and the capillary length produced by the forcing frequency of wavy patterns on thin liquid films. However, although this atomization approach is practical when the intended outcome is to produce sprays with droplets of the same size, drop sizes are diverse in real applications. Therefore, adequate characterization of drop size is paramount to establishing the relations between empirical approaches proposed in the literature and the outcome of ultrasonic atomization in actual operating conditions. In this sense, this work explores new approaches to spray characterization applied to ultrasonic sprays produced with different solvents. The first two introduced are the role of redundancy in drop size measurements to avoid resolution limitation in the measurement technique and compare using regular versus variable bin widths when building the histograms of drop size. Another spray characterization tool is the Drop Size Diversity to understand the limitations of characterizing ultrasonic sprays solely based on representative diameters or moments of drop size distributions. The results of ultrasonic spray characterization obtained emphasize: the lack of universality in the relation between a characteristic diameter and the capillary length associated with Faraday waves; the variability on drop size induced by both liquid properties and flow rate on the atomization outcome, namely, lower capillary lengths produce smaller droplets but less efficiently; the higher sensibility of the polydispersion and heterogeneity degrees in Drop Size Diversity when using variable bin widths to build the histograms of drop size; the higher drop size diversity for lower flow rates expressed by the presence of multiple clusters of droplets with similar characteristics leading to multimodal drop size distributions; and the gamma and log-normal mathematical probability functions are the ones that best describe the organization of drop size data in ultrasonic sprays.
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Sapit, Azwan, Takashi Yano, Yoshiyuki Kidoguchi i Yuzuru Nada. "Effect of Wall Configuration on Atomization of Rapeseed Oil Diesel Spray Impinging on the Wall". Applied Mechanics and Materials 315 (kwiecień 2013): 320–24. http://dx.doi.org/10.4028/www.scientific.net/amm.315.320.
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Fuel-air mixing is important process in diesel combustion. It has been well known that wall configuration of the piston affects spray atomization. Biomass fuel, that is viable alternative fuel for fossil one, needs great help of mixing to atomization because the fuel has high viscosity and high distillation temperature. This study investigates spray atomization characteristics of rapeseed oil (RO) when it impinges on the piston wall. Optical observation of RO spray was carried out using shadowgraph photography technique. The optical images and image analysis show that wall impingement effectively promotes RO spray atomization. Spray atomization is more sensitive to wall configuration for RO than diesel fuel. The wall that has flat floor at the bottom can improve atomization. It is necessary for RO spray to promote spray penetration followed by wall-impingement because long spray path offers wide spray boundary region to form droplets.
3
Post, Scott L., i Andrew J. Hewitt. "Flat-Fan Spray Atomization Model". Transactions of the ASABE 61, nr 4 (2018): 1249–56. http://dx.doi.org/10.13031/trans.12572.
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Abstract. In pesticide application, the lack of a suitable theoretical atomization model for flat-fan spray nozzles forces a reliance on empirical data and correlations, even for computational simulations. There is considerable difficulty in the theoretical analysis of the liquid sheet emanating from flat-fan nozzles because no simplification to a two-dimensional analysis can be employed, as is done for cylindrical jets. Nonetheless, 50 years ago, Dombrowski and co-workers used linear stability analysis to analyze the breakup of flat-fan spray sheets into ligaments and from ligaments to droplets. Their correlations have not found use because they include parameters that are difficult, if not impossible, to measure. In this work, the Dombrowski model is simplified using dimensional analysis, resulting in a correlation to predict the volume median diameter of flat-fan sprays in terms of common user parameters, i.e., the nozzle size and operating pressure. Keywords: Atomization, Droplet size, Nozzles, Pesticides, Sprayers.
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Ghahremani, Amirreza, Mohammad Ahari, Mojtaba Jafari, Mohammad Saidi, Ahmad Hajinezhad i Ali Mozaffari. "Experimental and theoretical study on spray behaviors of modified bio-ethanol fuel employing direct injection system". Thermal Science 21, nr 1 Part B (2017): 475–88. http://dx.doi.org/10.2298/tsci160108253g.
Pełny tekst źródłaStreszczenie:
One of the key solutions to improve engine performance and reduce exhaust emissions of internal combustion engines is direct injection of bio-fuels. A new modified bio-ethanol is produced to be substituted by fossil fuels in gasoline direct injection engines. The key advantages of modified bio-ethanol fuel as an alternative fuel are higher octane number and oxygen content, a long-chain hydro-carbon fuel, and lower emissions compared to fossil fuels. In the present study spray properties of a modified bio-ethanol and its atomization behaviors have been studied experimentally and theoretically. Based on atomization physics of droplets dimensional analysis has been performed to develop a new non-dimensional number namely atomization index. This number determines the atomization level of the spray. Applying quasi-steady jet theory, air entrainment and fuel-air mixing studies have been performed. The spray atomization behaviors such as atomization index number, Ohnesorge number, and Sauter mean diameter have been investigated employing atomization model. The influences of injection and ambient conditions on spray properties of different blends of modified bio-ethanol and gasoline fuels have been investigated performing high-speed visualization technique. Results indicate that decreasing the difference of injection and ambient pressures increases spray cone angle and projected area, and decreases spray tip penetration length. As expected, increasing injection pressure improves atomization behaviors of the spray. Increasing percentage of modified bio-ethanol in the blend, increases spray tip penetration and decreases the projected area as well.
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Mohandas, Anu, Hongrong Luo i Seeram Ramakrishna. "An Overview on Atomization and Its Drug Delivery and Biomedical Applications". Applied Sciences 11, nr 11 (2.06.2021): 5173. http://dx.doi.org/10.3390/app11115173.
Pełny tekst źródłaStreszczenie:
Atomization is an intricate operation involving unstable and complex networks with rupture and fusion of liquid molecules. There are diverse details that typify the spray formation, which are the technique and configuration of the atomization process, dimension and structure of the nozzle, experimental parameters, etc. Ultimately, the process generates fine sprays from the bulk of a liquid. Some examples of atomization that we come across in our day-to-day life are antiperspirant or hair spray, shower head, garden sprinkler, or cologne mist. In this review paper we are briefly discussing the theoretical steps taking place in an atomization technique. The instabilities of the jet and sheet are explained to understand the underlying theory that breaks the jet or sheet into droplets. Different types of atomization processes based on the energy sources are also summarized to give an idea about the advantages and disadvantages of these techniques. We are also discussing the various biomedical applications of the electrohydrodynamic atomization and its potential to use as a drug delivery system. In short, this paper is trying to demonstrate the diverse applications of atomization to show its potency as a user friendly and cost-effective technique for various purposes.
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Chen, J. L., M. Wells i J. Creehan. "Primary Atomization and Spray Analysis of Compound Nozzle Gasoline Injectors". Journal of Engineering for Gas Turbines and Power 120, nr 1 (1.01.1998): 237–43. http://dx.doi.org/10.1115/1.2818082.
Pełny tekst źródłaStreszczenie:
This work addresses primary atomization modeling, multidimensional spray prediction, and flow characteristics of compound nozzle gasoline injectors. Compound nozzles are designed to improve the gasoline spray quality by increasing turbulence at the injector exit. Under the typical operating conditions of 270-1015 kPa, spray atomization in the compound nozzle gasoline injectors is mainly due to primary atomization where the flow turbulence and the surface tension are the dominant factors. A primary atomization model has been developed to predict the mean droplet size far downstream by taking into account the effect of turbulent intensity at the injector exit. Two multidimensional spray codes, KIVA-2 and STAR-CD, originally developed for high-pressure diesel injection, are employed for the lower-pressure gasoline injection. A separate CFD analysis was performed on the complex internal flows of the compound nozzles to obtain the initial and boundary conditions for the spray codes. The TAB breakup model used in KIVA-2 adequately facilitates the atomization process in the gasoline injection.
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Ghaffar, Zulkifli Abdul, Ahmad Hussein Abdul Hamid i Mohd Syazwan Firdaus Mat Rashid. "Spray Characteristics of Swirl Effervescent Injector in Rocket Application: A Review". Applied Mechanics and Materials 225 (listopad 2012): 423–28. http://dx.doi.org/10.4028/www.scientific.net/amm.225.423.
Pełny tekst źródłaStreszczenie:
Injector is one of the vital devices in liquid rocket engine (LRE) as small changes in its configurations and design can result in significantly different LRE performance. Characteristics of spray such as spray cone angle, breakup length and Sauter mean diameter (SMD) are examples of crucial parameters that play the important role in the performance of liquid propellant rocket engine. Wider spray cone angle is beneficial for widespread of fuel in the combustion chamber for fast quiet ignition and a shorter breakup length provides shorter combustion chamber to be utilized and small SMD will result in fast and clean combustion. There are several mechanisms of liquid atomization such as swirling, e.g. jet swirl atomization or introducing bubbles into the liquid and effervescent atomization. Introducing a swirl component in the flow can enhance the propellant atomization and mixing whereas introducing bubbling gas directly into the liquid stream inside the injector leads to finer sprays even at lower injection pressures. This paper reviews the influence of both operating conditions and injector internal geometries towards the spray characteristics of swirl effervescent injectors. Operating conditions reviewed are injection pressure and gas-to-liquid ratio (GLR), while the injector internal geometries reviewed are limited to swirler geometry, mixing chamber diameter (dc), mixing chamber length (lc), aeration hole diameter (da), discharge orifice diameter (do) and discharge orifice length (lo).
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Zhang, Zhen, Yusong Yu i Jie Cao. "Effect of Upstream Valve Opening Process on Dynamic Spray Atomization of Bipropellant Thruster Injector". Micromachines 13, nr 4 (27.03.2022): 527. http://dx.doi.org/10.3390/mi13040527.
Pełny tekst źródłaStreszczenie:
In order to develop a new generation of intelligent satellites, fast-response bipropellant thrusters are required to work in minimum impulse mode without limitation. When a valve is opening, the fluctuation affects downstream spray atomization at the injector, which determines the thruster’s impulse performance, involving combustion efficiency and impulse repeatability. Accordingly, the spray atomization under impulse working condition was investigated to optimize the thruster’s dynamic response. The effects of propellant property, switch speed, valve stroke, and throttle orifice layout are respectively compared in simulation cases using OpenFOAM. The fluctuating flowrate caused by valve opening was simulated and then used as boundary conditions for downstream spray. Among these factors, orifice layout plays the most significant roles in transient spray development. Compared with MMH spray, NTO spray from outer swirl injector is more sensitive to upstream fluctuation. When the upstream flowrate stabilizes faster, the atomization stability can also be enhanced, thereby improving the impulse repeatability of thrusters in combustion. This experimental result was in good agreement with the simulation, thereby showing that only when atomization of MMH spray and NTO spray both develop into a steady state within 5 ms after valve opening can the impulse performance be reliably achieved.
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Sphicas, Panos, i Apostolos Pesyridis. "Diesel Spray Liquid Length Imaging at High Pressure". Energies 16, nr 6 (20.03.2023): 2874. http://dx.doi.org/10.3390/en16062874.
Pełny tekst źródłaStreszczenie:
Engine efficiency and emissions depend on the fuel atomization and dispersion. The fuel atomization and dispersion depend heavily on the ambient pressure and temperature. In this work, to study Diesel sprays in engine conditions, an electrically heated, constant-volume, pressurized vessel was designed and manufactured. The controlling electronics and software were developed and tested to ensure safe and precise operation. A commercial Bosch six-hole automotive Diesel injector was used. The spray spatial and temporal development were studied. In the literature, spray liquid length and cone angle are extensively used to quantify fuel dispersion. In this work, these parameters were quantified using a high-speed shadowgraph technique. Models were derived to describe the temporal evolution of the liquid core. Such models can be used to predict the Diesel spray behaviour and the engine performance.
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Li, Shougen, Chongchong Chen, Yaxiong Wang, Feng Kang i Wenbin Li. "Study on the Atomization Characteristics of Flat Fan Nozzles for Pesticide Application at Low Pressures". Agriculture 11, nr 4 (2.04.2021): 309. http://dx.doi.org/10.3390/agriculture11040309.
Pełny tekst źródłaStreszczenie:
Spraying is the most widely used means of pesticide application for pest control in agriculture and forestry. The atomization characteristics of the nozzles are directly related to the spray drift, rebound, and deposition. Previous research studies have mainly focused on the change pattern of atomization characteristics. Mathematical descriptions of the atomization characteristics of flat fan nozzles are rare, and pesticide application theories are also insufficient. Atomization characteristics mainly include droplet size and velocity. This study analyzes the influence of the spray parameters (spray angle, pressure, and equivalent orifice diameter of nozzles) and the spatial position in the flow field. To obtain the atomization characteristics of flat fan nozzles, the phase Doppler particle analyzer (PDPA) was selected for the accurate measurement of the droplet sizes and velocities at distances 0.30–0.60 m, using low spray pressures (0.15–0.35 MPa). The droplet size and velocity models were then established and validated. The results revealed that the average absolute error of the droplet size model was 23.74 µm and the average relative error was 8.23%. The average absolute and relative errors of the droplet velocity model were 0.37 m/s and 7.86%, respectively. At a constant spray pressure and angle, there was a positive correlation between the droplet size and the equivalent orifice diameter of the nozzles. The test also verified that the spray angle and distance had a negative correlation with the droplet velocity at a given pressure. The spray distance had no effect on the spray axial droplet size at constant spray pressure. In addition, the spray angle greatly affected the droplet velocity along the X-axis; similarly, the spray parameters, especially spray angle, greatly affected the droplet size.
Rozprawy doktorskie na temat "Spray and Atomization"
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Abbas, Fakhar. "Numerical Studies of Spray Atomization for Multiphase Flows". Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/29953.
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The current study aims to investigate and develop numerical tools for the simulation of interfacial flows, including those with turbulence and primary spray atomization. In the past, many approaches were developed to track the interface of a multi-phase/immiscible flow system. Two of them, the volume of fluid (VoF) and the level set (LS), have shown promising findings and have been considered a benchmark for further research. VoF methods have proved good mass conservation behaviour during the advection of solution. However, LS methods have shown better interface representation when used for the calculations of interfacial flows. Most of the recent development in this context either originated from VoF, LS or a combination of both.
In the first part of this thesis importance of the current study is highlighted in detail, and an overview of the recent developments for the numerical solutions of immiscible flows is presented. A detailed description of interface-capturing methods and their development over time is presented in a systematic way, leading to the issues addressed in this study. A stochastic field PDF-LES solution of the VoF approach is analyzed against the Sydney needle spray measurements. Solution behaviour for different combinations of stochastic fields and LES grid cells are examined in detail.
In the second part of this work, three different LES treatment for unresolved sub-grid fluctuations, TFVoF, TF-AC and newly developed EVD, has been presented. The performance analysis of two already existing solutions, TFVoF and TF-AC, is compared with the EVD approach. Sydney needle spray measurements are used as a benchmark for this comparison. The suitability of the EVD approach is also tested for different flow conditions. Simulation results confirm that sub-grid surface tension plays an important role in the realistic prediction of the jet decay rate, and proper closure models to account for sub-grid surface tension are very necessary. An already existing sub-grid surface tension closure model is incorporated into OpenFOAM and tested for all three LES filtered solutions.
The findings of this work suggest that the newly developed EVD approach has shown promising improvements to produce more reliable and realistic solutions for multi-phase flow
applications. Sub-volume surface tension closure model, following the EVD formulation, is helpful for more accurate jet decay rate predictions.
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Khuong, Anh Dung. "The Eulerian-Lagrangian Spray Atomization (ELSA) Model of the Jet Atomization in CFD Simulations: Evaluation and Validation". Doctoral thesis, Universitat Politècnica de València, 2012. http://hdl.handle.net/10251/17237.
Pełny tekst źródłaStreszczenie:
Fuel sprays play a major role in order to achieve the required combustion characteristics and pollutant emissions reduction on internal combustion engines, and thus, an accurate prediction of its behavior is required to perform reliable engine combustion and pollutant simulations. A great effort both on experimental and theoretical studies of spray atomization and dispersion has been performed in the latest years. As a result, Computational Fluid Dynamics (CFD) calculations have become a standard tool not only for spray physics understanding but also for design and optimization of engine spray systems.
However, spray modeling in its different uses in the Internal Combustion Engine (ICE) context is still nowadays a challenging task due to the complex interrelated phenomena taking place, some of them still not fully understood. Primary atomization and secondary breakup, droplet collision, coalescence and vaporization, turbulent interactions between phases have to be solved under high Reynolds (so they are turbulent) and Weber numbers conditions due to the high speed (~500 m/s) and small nozzle diameter (~100 µm) imposed by current engine injection systems technologies. Moreover, Taylor numbers cover a wide range, according to the composition of the injected liquid. Those conditions make experimental observations quite challenging and probably insufficient, especially in the very near nozzle region, where primary atomization takes place.
Most of the CFD spray models are currently based on the Discrete Droplet Method. The continuous liquid jet is discretized into 'blobs' or 'parcels', which consists in a number of droplets with the same characteristics. A Lagrangian method is applied to track the liquid phase parcels, which are subject to breakup according to atomization models mainly based on the linear instability theory proposed by Reitz and later extended by Huh and Gosman for liquid turbulence effects to be considered. This approach has been successfully applied bKhuong ., AD. (2012). The Eulerian-Lagrangian Spray Atomization (ELSA) Model of the Jet Atomization in CFD Simulations: Evaluation and Validation [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17237
Palancia
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Aftel, Robert. "Effect of atomization gas properties on droplet atomization in an "air-assist" atomizer". Master's thesis, Virginia Tech, 1996. http://hdl.handle.net/10919/32599.
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Air, nitrogen, argon and carbon dioxide were used as the atomizing gas in an 'air-assist' spray nozzle to determine the effect of these gases on mean droplet size, number density, velocity and their distributions in kerosene fuel spays and spray flames using a two dimensional phase Doppler interferometer. Data have been obtained with these atomizing gases using a base, air assisted case as a reference, since this is the most commonly used atomizing fluid in almost all applications. Comparisons were made between the gases on a mass and momentum flux basis. Both burning and nonburning sprays were investigated. The results show significant differences in atomization characteristics from the atomizer with different gases and under conditions of constant mass and momentum flux of the gas. The results also show that the presence of oxygen in the air atomized sprays assists in the combustion process, since it produces smaller and faster moving droplets, especially at locations near to the nozzle exit. In nonburning sprays, droplets had similar size and velocity. Lighter gases such as nitrogen more effectively atomized the fuel in comparison to the denser gases. Argon and carbon dioxide produced larger, slower moving droplets than air and nitrogen assisted cases in both the burning and nonburning sprays. Flame photographs revealed the argon and carbon dioxide atomized flames to have greater luminosity than air or nitrogen atomized flames.
Master of Science
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Singh, Gajendra. "Atomization and Combustion Characterization of Sprays". Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/23135.
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This thesis presents an extensive study of turbulent air-blasted sprays aimed at advancing the current understanding of the atomization and the turbulent combustion of dense sprays. The burner employed controls the spray quality by recessing the liquid-injecting needle inside the air-blast tube to transition the spray from dilute to dense. A pilot is used to stabilize the flame to the burner which is sitting in a co-flowing stream of secondary air. Three fuels, acetone, ethanol, and biodiesel, are used to generate several sprays that cover a broad range of non-dimensional numbers. Probability distributions of wavelength and amplitude of instabilities forming on coaxial air-blast atomizers are measured directly using high-speed shadowgraphs (or back-lit microscopic imaging), in a range of cases that investigate the independent effects of a suite of parameters. The influence of jet velocity and gas velocity on the initiation and growth of jet instabilities is discussed. The range of mechanisms governing the formation of liquid fragments and their relation to surface instabilities is discussed. Previous work suggested that the mean wavelength scales with the boundary layer thickness. This is confirmed here and extended to demonstrate that the wavelength probability distribution correlates well with the ligament length probability distribution. This establishes a direct link between interfacial instabilities and ligament formation in air-assisted primary atomization. The complete structure of atomizing liquid fragments is analyzed by employing multi-dimensional visualization techniques and advanced image processing, where objects from multiple views are matched to extract three-dimensional information. An in-house MATLAB script is developed to extract the spray volume, which employs the principle of image discretization, where each image is divided into a number of slices, and the individual slice from each camera is matched to compute the liquid volume fraction in each image. The volume of individual objects is calculated based on their planar area and orientation. An error analysis is performed using dozens of three-dimensional virtual models of fragment-like shapes with a known volume. Local characteristics of atomizing fragments are discussed by using the information obtained through the slicing method. A detailed account of fragment statistics are provided for the atomizing sprays. The LIF-OH-CH2O technique is used to measure the product of OH and CH2O ([OH]*[CH2O]) and hence the heat release zones in turbulent, moderately dense spray flames of ethanol and biodiesel fuels. A combination of several filters is used to remove interference from droplet luminosity. Mie scattering is measured jointly on a separate camera to locate the droplets with respect to the reaction zones. It is found that while the overall flame structure is similar to that of a diffusion flame. Structures referred to as burning rings of different sizes are observed, and these are ignited by heat source before they grow, propagate, and burnout. Statistics about the occurrence of these rings, with and without clouds of fragments within them, are presented. Occurrences of single-droplet combustion are also noted. Overall this thesis expands the current understanding of the primary and secondary atomization zones and provides new insights into the turbulent combustion characteristics of denser sprays. An extensive and novel data set in generated, and this will be made available to modelers with the aim of changing the predictive capability of both atomization and combustion of such flows.
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BURROUGHS, ERIC WILLIAM. "DEVELOPMENT OF A HIGH-RESOLUTION MECHANICAL SPRAY PATTERNATOR FOR THE CHARACTERIZATION OF FUEL SPRAYS". University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1132346171.
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Valencia, Bejarano Maritza. "Experimental investigation of droplet coalescence in a poly-disperse full-cone spray". Thesis, The University of Sydney, 2003. https://hdl.handle.net/2123/27907.
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Droplet collisions and coalescence play an important role in the droplet size evolution in
several processes involving sprays. These processes strongly affect the spray characteristics,
making it difficult to control and predict the final droplet size. This thesis has experimentally
quantified the effect of the operating conditions and multi-nozzle atomisation on droplet
coalescence in a full-cone spray. The coalescence mechanisms that lead to droplet collisions
and coalescence in the spray have also been investigated.
This experimental investigation was carried using two-fluid atomising nozzles with external
mixing for low flowrates, model number Mt” XAOOSROSOA from BETE, which produce a
poly-dispersed full-cone spray with an angle of 17-22°. In this work, measurements of the
integrated Sauter mean diameter, across the spray at various positions downstream of the
nozzle, were obtained by means of a laser diffraction instrument from Malvern Instruments
(Malvern 2600C). The measurements were carried out at five different operating conditions
for one-nozzle atomisation, where the principal manipulated variables were the water
flowrates, from 16.7 to 40 ml/min, and air flowrates, from 11.5 to 14.6 l/min. For the twonozzle
atomisation case, two nozzles were pointed towards each other, and the measurements
were carried out at the most favourable operating conditions for coalescence, found in the
single nozzle experiments.
The coalescence mechanisms involved in droplet collisions and coalescence were investigated
from the local values of the droplet size, and droplet mean and fluctuating velocities, which
were measured using a two component phase—Doppler anemometer RSA 3100 from
Aerometrics, Inc. The measurements were carried out for one and two nozzle atomisation, and
the droplet trajectories were studied for the two—nozzle atomisation case.
This work quantitatively confirms that droplet coalescence depends on the operating
conditions used. The most favourable operating conditions for coalescence were found when
the droplets generated were smaller, which corresponded to relatively low water flowrates
(16.7 ml/min) and high air flowrates (14.6 l/min) for this type of nozzle. At these conditions
the greatest size increase (52%) was obtained, the initial droplet size was the smallest (12.6
um), and the estimated droplet number concentration was the highest (6.7x107 m'3). By
contrast, a lower size increase (27%) was obtained when larger droplets were generated, at a
lower air flowrate of 13.1 l/min and a constant water flowrate of 16.7 ml/min. At these
conditions, the initial droplet size was approximately 18 am, and the estimated droplet
number concentration was just half (3.5x107 m’3) that for the most favourable operating
conditions for coalescence.
The results for the two-nozzle atomisation case have quantitatively demonstrated that droplet
coalescence is further increased by pointing two nozzles towards each other. The size increase
observed for the two nozzle atomisation was significantly greater (86%) compared with that
for the single nozzle case (52%). This is the result of an increase in estimated droplet number
concentration, from 6.7x107 m"3 to l.3><108 m‘3, which was achieved using two nozzles.
Coalescence among droplets interacting can be induced by different mechanisms, such as
Brownian motion, shearing flow and turbulence, differential motion by external forces
(gravity or centrifugal forces), aerodynamic and electrical forces, and acoustic fields. The
mechanism of coalescence was found to be mainly the differential velocity between droplets
of different sizes induced by the differential inertia between them, and the differential velocity
associated with the eddying fluid motion or turbulence. This differential velocity allows
droplets to approach each other, collide and coalescence. Droplet number concentration (inter
particle distance) is also an important parameter, as shown by the results for the two-nozzle
case compared with those for one nozzle.
Finally, a more detailed study at the edge of the spray at two different operating conditions,
generating relatively small and large droplets, quantitatively suggested that the greatest size
increase observed in this case for the smaller droplets case was because of both a 50%
increase in the velocities and a 20% increase in droplet number concentration when
generating smaller droplets.
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Downer, Roger Anthony. "The impact of spray modifiers on pesticide dose transfer". Thesis, University of Portsmouth, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327001.
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The impact of adjuvants on atomization and patternation of spray mixtures was evaluated. The data showed that certain adjuvants, in particular drift control agents, could potentially detrimentally affect the distribution of herbicide dose across the sprayed swath. The present research sets out to evaluate the impact of this distribution and to seek ways of improving the way researchers and users characterize and possibly mitigate these effects with a view to minimizing the potential detriments and maximizing the efficiency of herbicide active ingredient (AI) utilization. Different formulations of glyphosate with and without a novel polymeric drift control agent (AgRho DR 2000) applied to contrasting broad-leaved and grass weeds were used to evaluate several effects of polymer use. Variables included nozzle type (XR TeeJet extended range flat spray tips, TT Turbo TeeJet wide angle flat spray tips, and TurboDrop air induction nozzles) sampling position (principally under the nozzle centers and under the overlap between two adjacent nozzles), boom height (30, 45, and 60 cm above the target), spray delivery (the volume of spray arriving at the target), spray retention ( the volume of spray actually retained by the target foliage), and herbicide efficacy ( the response of the target weeds to the herbicide dose applied). The data showed that when the polymer was included in the spray mixture, the nozzle used, boom height, presence of the adjuvant, sampling position and certain interactions between these variables were all significant. Spray retention was affected by plant type and retention of coarse sprays was improved by the inclusion of DR 2000. Very coarse sprays reduced glyphosate efficacy on both grasses and broad-leaved weeds although that effect was reduced by use of DR. Addition of drift control agents always ii resulted in increased variability in spray distribution with concomitant increases in both retention and efficacy variability. Variability was shown to decrease with decreasing boom height. There was little correlation between spray delivery and herbicide efficacy. Deposit structure was shown to be a highly important factor in understanding herbicide dose transfer. A novel methodology utilizing digital imaging technology and diversity statistics was developed and evaluated to improve the way we measure and characterize deposit structures. Separation of qualitatively different treatments with similar volumetric distributions was possible. This methodology will be of use to both biologists and fOnTIulation chemists for prediction or explanation of biological results relating to deposit structure. Use of Scanning electron microscopy, and epi-fluorescence microscopy was used to characterize deposit morphology. Differences in deposit morphology were observed and documented leading to a possible explanation for the enhanced glyphosate activity in the presence of DR 2000 iii
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FLOHRE, NICHOLAS MATTHEW. "EXPERIMENTAL INVESTIGATION OF SPRAY ATOMIZATION PROPERTIES OF AN AIRCRAFT ENGINE SWIRL CUP". University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1054322000.
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Pandal, Blanco Adrián. "Implementation and Development of an Eulerian Spray Model for CFD simulations of diesel Sprays". Doctoral thesis, Universitat Politècnica de València, 2016. http://hdl.handle.net/10251/68490.
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[EN] The main objective of this work is the modeling of diesel sprays under engine conditions, including the atomization, transport and evaporation processes pivotal in the diesel spray formation and its development. For this purpose, an Eulerian single fluid model, embedded in a RANS environment, is implemented in the CFD platform OpenFOAM.
The modeling approach implemented here is based on the ⅀-Y model. The model is founded on the assumption of flow scales separation. In actual injection systems, it can be assumed that the flow exiting the nozzle is operating at large Reynolds and Weber numbers and thus, it is possible to assume a separation of features such as mass transport (large scales) from the atomization process occurring at smaller scales. The liquid/gas mixture is treated as a pseudo-fluid with variable density and which flows with a single velocity field. Moreover, the mean geometry of the liquid structures can be characterized by modeling the mean surface area of the liquid-gas interphase per unit of volume. Additionally, an evaporation model has been developed around the particular characteristics of the current engine technologies. This means that vaporization process is limited by fuel-air mixing rate and fuel droplets evaporate as long as there is enough air for them to heat up and vaporize. Consequently, the evaporation model is based on the Locally Homogeneous Flow (LHF) approach. Under the assumption of an adiabatic mixing, in the liquid/vapor region, the spray is supposed to have a trend towards adiabatic saturation conditions and to determine this equilibrium between phases Raoult's ideal law is considered. Finally, the spray model is coupled with an advanced combustion model based on approximated diffusion flames (ADF), which reduces the computational effort especially for complex fuels and is a natural step for modeling diesel sprays.
First, the model is applied to a basic external flow case under non-vaporizing conditions, extremely convenient due to both the experimental database available and the symmetric layout which allows important simplification of the modeling effort. Good agreement between computational results and experimental data is observed, which encourages its application to a more complex configuration. Secondly, the model is applied to the "Spray A" from the Engine Combustion Network (ECN), under non-vaporizing conditions, in order to reproduce the internal structure of diesel sprays as well as to produce accurate predictions of SMD droplets sizes. Finally, vaporizing "Spray A" studies are conducted together with the baseline reacting condition of this database. The calculated spray penetration, liquid length, spray velocities, ignition delay and lift-off length are compared with experimental data and analysed in detail.[ES] El objetivo principal de este trabajo es el modelado de chorros diésel en condiciones de motor, incluyendo los fenómenos de atomización, transporte y evaporación fundamentales en la formación y desarrollo del chorro. Para este fin, se implementa un modelo de spray euleriano de tipo monofluido en un entorno RANS en la plataforma CFD OpenFOAM. El enfoque de modelado aplicado aquí sigue la idea de un modelo del tipo ⅀-Y. El modelo se fundamenta en la hipótesis de separación de escalas del flujo. En los sistemas de inyección actuales, es posible asumir que el flujo que sale de la tobera opera a altos números de Reynolds y Webber y por tanto, es posible considerar la independencia de fenómenos como el transporte de masa (grandes escalas del flujo) de los procesos de atomización que ocurren a escalas menores. La mezcla líquido/gas se trata como un pseudo-fluido con densidad variable y que fluye según un único campo de velocidad. Además, la geometría promedio de las estructuras de líquido se puede caracterizar mediante el modelado de la superficie de la interfase líquido/gas por unidad de volumen. Completando el modelo de chorro, se ha desarrollado un modelo de evaporación alrededor de las características particulares de las tecnologías actuales de los motores. Esto supone que el proceso de evaporación está controlado por mezcla aire-combustible y las gotas de combustible se evaporan siempre que exista suficiente aire para calentarlas y evaporarlas. Debido a esto, el modelo de evaporación implementado está basado en el enfoque de Flujos Localmente Homogéneos (LHF). Considerando una mezcla adiabática, en la región líquido/vapor, se supone que el chorro tiende a las condiciones adiabáticas de saturación y para determinar este equilibrio entre fases, se utiliza la ley ideal de Raoult. Finalmente, el modelo de chorro se acopla con un modelo avanzado de combustión basado en llamas de difusión aproximadas (ADF), que reduce el coste computacional especialmente para combustibles complejos y supone el paso lógico en el desarrollo del modelo para simular chorros diesel. En primer lugar, el modelo se aplica al cálculo de un caso básico de flujo externo no evaporativo, muy adecuado tanto por la extensa base de datos experimentales disponible como por la simetría geométrica que presenta, permitiendo una importante simplificación de la simulación. Los resultados obtenidos presentan un buen acuerdo con los experimentos, lo cual estimula su aplicación en configuraciones más complejas. En segundo lugar, el modelo se aplica al cálculo del "Spray A" del Engine Combustion Network (ECN), no evaporativo, para reproducir la estructura interna del chorro diesel así como predecir tamaños de gota (SMD) de forma precisa. Finalmente, se realizan estudios evaporativos del "Spray A" junto con la condición nominal reactiva de esta base de datos. La penetración de vapor, la longitud líquida, velocidad, el tiempo de retraso y la longitud de despegue de llama calculados se comparan con los datos experimentales y se analizan en detalle.
[CAT] L'objectiu principal d'aquest treball és el modelatge de dolls dièsel en condicions de motor, incloent els fenòmens d'atomització, transport i evaporació fonamentals en la formació i desenvolupament del doll. Amb aquesta finalitat, s'implementa un model de doll eulerià de tipus monofluid en un entorn RANS a la plataforma CFD OpenFOAM. L'enfocament de modelatge aplicat ací segueix la idea d'un model del tipus ⅀-Y. El model es fonamenta en la hipòtesi de separació d'escales del flux. En els sistemes d'injecció actuals, és possible assumir que el flux que surt de la tovera opera a alts nombres de Reynolds i Webber, i per tant és possible considerar la independència de fenòmens com el transport de massa (grans escales del flux) dels processos d'atomització que ocorren a escales menors. La mescla líquid / gas es tracta com un pseudo-fluid amb densitat variable i que flueix segons un únic camp de velocitat. A més, la geometria mitjana de les estructures de líquid es pot caracteritzar mitjançant el modelatge de la superfície de la interfase líquid / gas per unitat de volum. Completant el model, s'ha desenvolupat un model d'evaporació al voltant de les característiques particulars de les tecnologies actuals dels motors. Això suposa que el procés d'evaporació està controlat per la mescla aire-combustible i les gotes de combustible s'evaporen sempre que hi hagi suficient aire per escalfar i evaporar. A causa d'això, el model d'evaporació implementat està basat en el plantejament de fluxos Localment Homogenis (LHF). Considerant una mescla adiabàtica, a la regió líquid / vapor, se suposa que el doll tendeix a les condicions adiabàtiques de saturació i per determinar aquest equilibri entre fases, s'utilitza la llei ideal de Raoult. Finalment, el model de doll s'acobla amb un model avançat de combustió basat en flamelets de difusió aproximades (ADF), que redueix el cost computacional especialment per a combustibles complexos i suposa el pas lògic en el desenvolupament del model per simular dolls dièsel. En primer lloc, el model s'aplica al càlcul d'un cas bàsic de flux extern no evaporatiu, molt adequat tant per l'extensa base de dades experimentals disponible com per la simetria geomètrica que presenta, permetent una important simplificació de la simulació. Els resultats obtinguts presenten un bon acord amb els experiments, la qual cosa estimula la seva aplicació en configuracions més complexes. En segon lloc, el model s'aplica al càlcul del "Spray A" no evaporatiu de la xarxa Engine Combustion Network (ECN), per reproduir l'estructura interna del doll dièsel així com predir mides de gota (SMD) de forma precisa. Finalment, es realitzen estudis evaporatius del "Spray A" juntament amb la condició nominal reactiva d'aquesta base de dades. La penetració de vapor, la longitud líquida, velocitat, el temps de retard i la longitud d'enlairament de flama calculats es comparen amb les dades experimentals i s'analitzen en detall.
Pandal Blanco, A. (2016). Implementation and Development of an Eulerian Spray Model for CFD simulations of diesel Sprays [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/68490
TESIS
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Strasser, Wayne Scott. "Seeking Understanding of Acoustics and Spray Character in a Three-Stream Pulsating Transonic Airblast Injector". Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/77428.
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Despite the staggering volume of work in the open literature on primary and secondary atomization, there is nothing known that addresses the mechanisms for, and injector geometry implications for, primary atomization within a self-sustained pulsating transonic three-stream injector. Thus, a computational effort involving 86 simulations, including multiple validation exercises, has been executed in order to develop a numerical foundation and then study the effects of nozzle geometry, numerical methodology, grid resolution, modeled domain extent, feed rates, feed flow modulation, feed flow swirl, feed materials, and operating conditions. This is the first undertaking ever reported to disclose the intense details of transonic pulsating flows within the three-stream injector.
Metrics for assessment of acoustics and temporal spray character were numerous. Frequency responses among those metrics implied a common pulsation-driving mechanism. It has been discovered that liquid bridging with the production of a liquid fountain and shocklet-like structures in the retracted (pre-filming) zone, along with localized gas-liquid normal pressure gradients, are responsible for bulk pulsations. These findings were never reported in the literature, thus represent an important contribution of this study.
Unexpectedly, a new trend for temporal mean droplet size, when normalized by distance from the nozzle, versus distance from the nozzle has been found, which took a common form among all geometries and feed materials tested. Therefore, there is some value to simulate air-water flows, first, to scope general parameters and characteristics, before modeling more computationally challenging slurry flows. This represents an additional contribution of this work not previously reported in the literature.
Newly unveiled strong interactions between feed materials, geometry, and feed rate were discovered. Various combinations of inner nozzle retraction and slurry annular thickness were shown to be advantageous, depending on the goals of the injection system. The importance of either geometry variable for three-stream injectors has not been quantified until now.
The predictive power of various modeling frameworks has been assessed for the first time. Axi-symmetric (AS) simulations can successfully predict absolute acoustic details; remarkably and surprisingly, AS simulations can also be used for directional indicators of bulk droplet size. This is an especially powerful revelation given the massive reduction in computational requirements for AS models. Reduced order 3-D models are required for better droplet size estimates. A relatively simple eddy-viscosity turbulent model seems to be adequate for predicting droplet sizes for three-stream injectors, in which the primary energy source is bulk pulsations. For larger two-stream systems (atomization energy is sourced in local shear layer instability development), however, a state-of-the-art hybrid model (newly implemented for this effort) appeared to be necessary to capture the resulting droplet scales. Lastly, droplet size and characteristic flow length scale predictions for two open literature non-Newtonian liquid atomizers were made available.Ph. D.
Książki na temat "Spray and Atomization"
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Lavernia, Enrique J. Spray atomization and deposition. Chichester: John Wiley, 1996.
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R, Buchele Donald, i United States. National Aeronautics and Space Administration., red. Small-droplet spray measurements with a scattered-light scanner. [Washington, D.C.]: National Aeronautics and Space Administration, 1988.
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R, Buchele Donald, i United States. National Aeronautics and Space Administration., red. Small-droplet spray measurements with a scattered-light scanner. [Washington, D.C.]: National Aeronautics and Space Administration, 1988.
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R, Buchele Donald, i United States. National Aeronautics and Space Administration., red. Small-droplet spray measurements with a scattered-light scanner. [Washington, D.C.]: National Aeronautics and Space Administration, 1988.
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R, Buchele Donald, i United States. National Aeronautics and Space Administration., red. Small-droplet spray measurements with a scattered-light scanner. [Washington, D.C.]: National Aeronautics and Space Administration, 1988.
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Yates, Wesley E. Effects of Nalco-Trol on atomization. Davis, CA: U.S. Dept. of Agriculture, Forest Service, Forest Pest Management, 1985.
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Kuan-Yun, Kuo Kenneth, red. Recent advances in spray combustion: Spray atomization and drop burning phenomena. Reston, Virginia: American Institute of Aeronautics and Astronautics, 1996.
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Chang, Chan-Teng. Experimental study of diesel spray characteristics and atomization. Ann Arbor: UMI, 1998.
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J, Dunkley John, red. Atomization of melts for powder production and spray deposition. Oxford: Clarendon Press, 1994.
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United States. National Aeronautics and Space Administration., red. Cryogenic spray vaporization in high-velocity helium, argon and nitrogen gasflows. [Washington, DC]: National Aeronautics and Space Administration, 1993.
Znajdź pełny tekst źródłaCzęści książek na temat "Spray and Atomization"
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Günther, Astrid, i Karl-Ernst Wirth. "Superheated Atomization". W Process-Spray, 609–45. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-32370-1_16.
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Bogno, Abdoul-Aziz, Hani Henein, Volker Uhlenwinkel i Eric Gärtner. "Single Fluid Atomization Fundamentals". W Metal Sprays and Spray Deposition, 9–48. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-52689-8_2.
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Anderson, Iver E., i Lydia Achelis. "Two Fluid Atomization Fundamentals". W Metal Sprays and Spray Deposition, 49–88. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-52689-8_3.
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Lefebvre, Arthur H., i Vincent G. McDonell. "External Spray Characteristics". W Atomization and Sprays, 183–205. Second edition. | Boca Raton : Taylor & Francis, CRC Press, 2017.: CRC Press, 2017. http://dx.doi.org/10.1201/9781315120911-7.
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Eslamian, M., i N. Ashgriz. "Spray Drying, Spray Pyrolysis and Spray Freeze Drying". W Handbook of Atomization and Sprays, 849–60. Boston, MA: Springer US, 2010. http://dx.doi.org/10.1007/978-1-4419-7264-4_37.
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Omer, K., i N. Ashgriz. "Spray Nozzles". W Handbook of Atomization and Sprays, 497–579. Boston, MA: Springer US, 2010. http://dx.doi.org/10.1007/978-1-4419-7264-4_24.
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Lefebvre, Arthur H., i Vincent G. McDonell. "Spray Size and Patternation Methods". W Atomization and Sprays, 243–80. Second edition. | Boca Raton : Taylor & Francis, CRC Press, 2017.: CRC Press, 2017. http://dx.doi.org/10.1201/9781315120911-9.
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Umemura, A. "Spray Group Combustion". W Handbook of Atomization and Sprays, 299–313. Boston, MA: Springer US, 2010. http://dx.doi.org/10.1007/978-1-4419-7264-4_14.
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Moreira, A. L. N., i M. R. Oliveira Panão. "Spray-Wall Impact". W Handbook of Atomization and Sprays, 441–55. Boston, MA: Springer US, 2010. http://dx.doi.org/10.1007/978-1-4419-7264-4_21.
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Purwanto, A., W. N. Wang i K. Okuyama. "Flame Spray Pyrolysis". W Handbook of Atomization and Sprays, 869–79. Boston, MA: Springer US, 2010. http://dx.doi.org/10.1007/978-1-4419-7264-4_39.
Pełny tekst źródłaStreszczenia konferencji na temat "Spray and Atomization"
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FAETH, G. "Spray atomization and combustion". W 24th Aerospace Sciences Meeting. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1986. http://dx.doi.org/10.2514/6.1986-136.
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Costa, Mário, Bruno Pizziol, Miguel Panao i André Silva. "Multiple Impinging Jet Air-Assisted Atomization". W ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems. Valencia: Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/ilass2017.2017.4737.
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The growth of the aviation sector triggered the search for alternative fuels and continued improvements in thecombustion process. This work addresses the technological challenges associated with spray systems and theconcern of mixing biofuels with fossil fuels to produce alternative and more ecological fuels for aviation. This workproposes a new injector design based on sprays produced from the simultaneous impact of multiple jets, using anadditional jet of air to assist the atomization process. The results evidence the ability to control the average dropsize through the air-mass flow rate. Depending on the air-mass flow rate there is a transition between atomizationby hydrodynamic breakup of the liquid sheet formed on the impact point, to an aerodynamic breakup mechanism,as found in the atomization of inclined jets under cross-flow conditions. The aerodynamic shear breakupdeteriorates the atomization performance, but within the same order of magnitude. Finally, our experiments showthat mixing a biofuel with a fossil fuel does not significantly alter the spray characteristics, regarded as a stepfurther in developing alternative and more ecological fuels for aero-engines.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4737
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FERRENBERG, A., i M. VARMA. "Atomization data for spray combustion modeling". W 21st Joint Propulsion Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1985. http://dx.doi.org/10.2514/6.1985-1316.
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Jacobsohn, Gabriel L., Eli T. Baldwin, David P. Schmidt, Benjamin R. Halls, Alan Kastengren i Terrence R. Meyer. "Diffuse Interface Eularian Spray Atomization Modeling of Impinging Jet Sprays". W 2018 AIAA Aerospace Sciences Meeting. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2018. http://dx.doi.org/10.2514/6.2018-2078.
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Gorny, Ramona Klaudia, Gerhard Schaldach, Peter Walzel i Markus Thommes. "Spray Conditioning for the Preparation of Spray Dried Submicron Particles". W ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems. Valencia: Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/ilass2017.2017.4701.
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Particle size reduction down to the submicron range (0.1-1 µm) is an effective option to increase the bioavailabilityof low water soluble active pharmaceutical ingredients. According to the Nernst-Brunner equation, the preparation of submicron sized particles increases the specific surface area, thus increases the dissolution rate. Conventional spray drying devices for submicron particles show certain limitations. The main challenge is the preparation of small and uniform droplets during the atomisation step. In this work, fine droplets were generated combining a nozzle with a droplet separator. Therefore, the aerosol is generated with a pneumatic nozzle and is sprayed into a cyclone droplet separator. Depending on the characteristics of the cyclone, droplets larger than the cut-off-size were separated and returned into the liquid feed. The conditioned aerosol at the top of the cyclone separator can then be introduced into the drying chamber. With this concept the usable part is separated, thus no classification process after drying is necessary. The investigations show that the dependencies during atomisation of the droplets size on the liquid-to-gas mass flow ratio µm and the liquid properties (e.g. viscosity) do not apply to the separation step. The conditioned aerosol only depends on the separation characteristics of the cyclone droplet separator. However, the amount of droplets separated is determined by the atomisation step. Hence, the amount of droplets smaller than the cut-off-size can be increased by decreasing the droplet size of the primary aerosol. This is realised by secondary droplet fragmentation. An impact surface causes breakup of the droplets of theprimary aerosol before separation. The investigations show an increased amount of droplets <2µm.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4701
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Daaboul, Michel, Nicolas Saba, Jihad Rishmany i Christophe Louste. "Properties of Fuel Spray Obtained by Electrohydrodynamic Atomization". W ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems. Valencia: Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/ilass2017.2017.5018.
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Airblast atomization is com monly used to atomize fuel in aircraft engines. An annular liquid sheet is atomized bythe shear forces exerted by the co-flowing air stream. Nevertheless, this technique is less effe ctive in some specific cases, e.g. when the external air flow velocity is relatively low. Electrohydrodynamic (EHD) atomization can constitute a solution in these cases. It consists of applying an electric field between two electrodes and electricallycharging the passing carburant. This phenomenon will create instabilities within the liquid, provoking therefore its atomization. The main objective is therefore to electrically atomize a liquid sheet without the application of an external air flow like in airblast atomizers.This paper presents a novel actuator, based on dielectric barrier injection, used to induce instabilities within a plane liquid sheet of fuel similar to the annular sheet in aircraft engines. The behaviour of this atomizer was described in previous works. Several modes were observed, sometimes leading to a complete atomization, or just inducing instabilities and oscillating the liquid sheet. In the present study, only the cases where the liquid sheet is completely atomized are investigated. Images were reco rded with the help of a high speed camera. Primary atomization is only studied, secondaryatomization being neglected. The properties of the spray obtained by EHD atomization are investigated thoroughly, namely the breakup length, the mesh size, the drople t diameter, thedroplet count, etc.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.5018
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Lozano, Antonio, Juan Antonio García, Javier Alconchel, Félix Barreras, Esteban Calvo i José Luis Santolaya. "Influence of liquid properties on ultrasonic atomization". W ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems. Valencia: Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/ilass2017.2017.4588.
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Ultrasonic atomization is very convenient because it can generate droplets with diameters of a few microns andwith very narrow size distribution. Besides, opposite to twin fluid nozzles, in ultrasonic atomization, dropletgeneration and transport are decoupled processes. Droplets are ejected from the liquid surface with very lowvelocities, so driving them is relatively simple. Although this atomization method is now common in some specificapplications, for example in household humidifiers, there are still some details about the physics of this processthat are not completely understood. Up to date, most of the published results have been limited to experimentswith water. However, it has been demonstrated that atomization rates quickly decrease as liquid viscosityincreases. This work analyzes the characteristics of ultrasonic atomization of some alternative fluids to determineif there is any influence of other physical properties such as surface tension or vapor pressure. Experiments areperformed using a commercial piezoceramic disk with a resonance frequency of 1.65 MHz. The disk is excitedwith a sinusoidal signal with voltage amplitudes that go up to 60 V. Sprays are visually characterized analyzinginstantaneous images and high speed video sequences. Besides atomization rates are calculated by measuringthe weight loss in a fixed time.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4588
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Bornschlegel, Sebastian, Chris Conrad, Lisa Eichhorn i Michael Wensing. "Flashboiling atomization in nozzles for GDI engines". W ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems. Valencia: Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/ilass2017.2017.4750.
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Flashboiling denotes the phenomenon of rapid evaporation and atomization at nozzles, which occurs when fluidsare injected into ambient pressure below their own vapor pressure. It happens in gasoline direct injection (GDI) engines at low loads, when the cylinder pressure is low during injection due to the closed throttle valve. The fuel temperature at the same time approaches cylinder head coolant temperature due to the longer dwell time of the fuel inside the injector. Flash boiling is mainly beneficial for atomization quality, since it produces small droplet sizes and relative broad and homogenous droplet distributions within the spray. Coherently, the penetration depth normally decreases due to the increased aerodynamic drag. Therefore the thermal properties of injectors are often designed to reach flash boiling conditions as early as possible. At the same time, flash boiling significantly increases the risk of undesired spray collapsing. In this case, neighbouring jets converge and form a single jet. Due to the now concentrated mass, penetration depth is enhanced again and can lead to liner or piston wetting in addition to the overall diminished mixture formation.In order to understand the underlying physics, it is important to study the occurring phenomena flashboiling and jet-to-jet interacting i.e. spray collapsing separately. To this end, single hole injectors are built up to allow for an isolated investigation of flashboiling. The rapid expansion at the nozzle outlet is visualized with a microscopic high speed setup and the forces that lead to the characteristic spray expansion are discussed. Moreover, the results on the macroscopic spray in terms of penetration, cone angles and vapor phase are shown with a high speed Schlieren setup. Resulting droplet diameters and velocities are measured using LDA/PDA.As a result, we find a comprehensive picture of flash boiling. The underlying physics can be described and discussed for the specific case of high pressure injection at engine relevant nozzle geometries and conditions, but independently from neighbouring jets. These findings provide the basis to understand and investigate flashboilingand jet-to-jet interaction as distinct, but interacting subjects rather than a combined phenomenon.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4750
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Dai, S., J. P. Delplanque, E. J. Lavernia i R. H. Rangel. "Modeling of Reactive Spray Atomization and Deposition". W ITSC 1998, redaktor Christian Coddet. ASM International, 1998. http://dx.doi.org/10.31399/asm.cp.itsc1998p0341.
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Abstract Recent experimental investigations of reactive spray deposition of aluminum alloys have indicated that oxides could not be detected for atomization gas oxygen contents lower than 10%. In order to elucidate this behavior, an analysis of the oxidation kinetics during reactive spray deposition based on the Mott-Cabrera theory of oxidation is proposed herein. A linear growth law is obtained that indicates that the oxide growth rate decreases with decreasing temperature or oxygen pressure. Furthermore, the oxide growth rate is found to decrease faster at low oxygen pressure with decreasing temperature as well as at low temperature with decreasing oxygen pressure. Calculations of the width of oxide stringers as a function of oxygen content and superheat temperature based on this analysis are in good agreement with the experimental observations.
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Corcoran, T., A. Mansour i N. Chigier. "Medical Atomization Design for Inhalation Therapy". W ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0779.
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Abstract The medical community has lately shown increased interest in drug administration via the internal surfaces of the lung. Administration of medication to the lungs is typically performed using either an aerosol or a spray, that is inhaled by the patient. Spray droplet size distribution is a primary determinant of whether medication will deposit effectively within the lungs. Spray liquid flow rates will determine required treatment time. Examination of three typical atomizer (nebulizer) designs used to generate inhalation sprays is presented. The separate stages in the design of these nebulizers include entrainment (jet pump), atomization, and conveyance stages. Mass flow rate of liquid in the sprays delivered from all examined designs was at least two orders of magnitude less than the mass flow rates of liquid pumped through the atomization stages. This indicated that liquid typically circulated through the atomization stages many times before being completely administered. Visualization was performed on the atomization stages showing less than ideal mechanisms for break up. Final outlet droplet cumulative number distributions obtained via Phase Doppler Particle Analyzer (PDPA) demonstrate that approximately 80% of the droplets generated by each design are within the range of sizes generally considered desirable for inhaled administration. (1–5 μm).
Raporty organizacyjne na temat "Spray and Atomization"
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Genzale, Caroline. Development of a Turbulent Liquid Spray Atomization Model for Diesel Engine Simulations. Office of Scientific and Technical Information (OSTI), czerwiec 2021. http://dx.doi.org/10.2172/1785712.
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Oefelein, Joseph. Development of high-fidelity models for liquid fuel spray atomization and mixing processes in transportation and energy systems. Office of Scientific and Technical Information (OSTI), kwiecień 2015. http://dx.doi.org/10.2172/1494618.
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Lin, S. P. Mechanism of Atomization and Behavior of Non-Dilute Sprays. Fort Belvoir, VA: Defense Technical Information Center, czerwiec 1992. http://dx.doi.org/10.21236/ada254902.
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