Academic literature on the topic 'Droplet velocity distribution'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Droplet velocity distribution.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Droplet velocity distribution"
1
Wang, Junpeng, Cuicui Xu, Gang Zhou, and Yansong Zhang. "Spray Structure and Characteristics of a Pressure-Swirl Dust Suppression Nozzle Using a Phase Doppler Particle Analyze." Processes 8, no. 9 (September 10, 2020): 1127. http://dx.doi.org/10.3390/pr8091127.
Full textAbstract:
In order to understand the characteristics of the spray field of a dust suppression nozzle and provide a reference for dust nozzle selection according to dust characteristics, a three-dimensional phase Doppler particle analyzer (PDPA) spray measurement system is used to analyze the droplet size and velocity characteristics in a spray field, particularly the joint particle size–velocity distribution. According to the results, after the ejection of the jet from the nozzle, the droplets initially maintained some velocity; however, the distribution of particles with different sizes was not uniform. As the spray distance increased, the droplet velocity decreased significantly, and the particle size distribution changed very little. As the distance increased further, the large droplets separated into smaller droplets, and their velocity decreased rapidly. The distributions of the particle size and velocity of the droplets then became stable. Based on the particle size-velocity distribution characteristics, the spray structure of pressure-swirl nozzles can be divided into five regions, i.e., the mixing, expansion, stabilization, decay, and rarefied regions. The expansion, stabilization, and decay regions are the effective dust fall areas. In addition, the droplet size in the stabilization region is the most uniform, indicating that this region is the best dust fall region. The conclusions can provide abundant calibration data for spray dust fall nozzles.
2
Sun, Yicheng, Yufan Fu, Baohui Chen, Jiaxing Lu, and Wanquan Deng. "Numerical Simulation and Experimental Study on Flow Field in a Swirl Nozzle." Shock and Vibration 2021 (January 25, 2021): 1–9. http://dx.doi.org/10.1155/2021/6626715.
Full textAbstract:
In order to study the internal flow characteristics and external droplet velocity distribution characteristics of the swirl nozzle, the following methods were used: numerical simulations were used to study the internal flow characteristics of a swirl nozzle and phase Doppler particle velocimetry was used to determine the corresponding external droplet velocity distribution under medium and low pressure conditions. The distributions of pressure and water velocity inside the nozzle were obtained. Meanwhile, the velocities of droplets outside the nozzle in different sections were discussed. The results show that the flow rate in the swirl nozzle increases with the increase in inlet pressure, and the local pressure in the region decreases because of the excessive velocity at the internal outlet section of the swirl nozzle, resulting in cavitation. The experimental results show that under an external flow field, the minimum droplet velocity occurs in the axial direction; starting from the axis, the velocity first increases and then decreases along the radial direction. Swirling motion inside the nozzle and velocity variations in the external flow field occur under medium and low pressure conditions. The relationship between the inlet pressure and the distributions of water droplets’ velocities was established, which provides a reference for the research and development of the swirl nozzle.
3
Li, Xinpeng, Liping Chen, Qin Tang, Longlong Li, Wu Cheng, Peng Hu, and Ruirui Zhang. "Characteristics on the Spatial Distribution of Droplet Size and Velocity with Difference Adjuvant in Nozzle Spraying." Agronomy 12, no. 8 (August 19, 2022): 1960. http://dx.doi.org/10.3390/agronomy12081960.
Full textAbstract:
The spatial distribution of droplet size and velocity affects the deposition and distribution on the target. In order to investigate the influence of different adjuvant and pressures on the spatial distribution of droplet size and velocity in atomization area of different nozzles, air induction flat fan nozzle IDK120-03, multi-range flat fan nozzle LU120-03 and anti-drift flat fan nozzle AD120-03 were selected. Phase Doppler Interferometer (PDI) was used to analyze and compare the distribution of droplet size and velocity in the atomization area of three nozzles when four typical adjuvant Maisi, Maidao, Adsee AB-600 and Surun sprayed at different pressures. The results show that the volume median diameter of droplet size has no obvious change along the vertical direction of the nozzle center and increases with distance in the horizontal direction, the droplet size decreases with increasing pressure at the same position, the adjuvant all increases the droplet size (about 12%, 12%, 10% and 9% for Maisi, Maidao, Surun and Adsee AB-600, respectively), IDK120-03 nozzle droplet size is the largest and LU120-03 nozzle is the smallest in the same position. For droplet velocity distribution, droplet velocity decrease in distance along the vertical and horizontal direction, respectively, the droplet velocity increases with increasing pressure at the same position, compared with water, the droplet velocity increased by about 13%, 9%, 8%, and 4% for Maisi, Maidao, Surun, and Adsee AB-600, respectively, the velocity of AD nozzle is the largest and IDK nozzle is the smallest at the same position. The experiment can provide a basis for the selection of adjuvants and nozzles in pesticide application, and provide a data base for studying the distribution of droplets on the target.
4
Ge, MaoSheng, Pute Wu, Delan Zhu, and Daniel P. Ames. "Comparison between sprinkler irrigation and natural rainfall based on droplet diameter." Spanish Journal of Agricultural Research 14, no. 1 (March 2, 2016): e1201. http://dx.doi.org/10.5424/sjar/2016141-8076.
Full textAbstract:
<p>An indoor experiment was conducted to analyze the movement characteristics of different sized droplets and their influence on water application rate distribution and kinetic energy distribution. Radial droplets emitted from a Nelson D3000 sprinkler nozzle under 66.3, 84.8, and 103.3 kPa were measured in terms of droplet velocity, landing angle, and droplet kinetic energy and results were compared to natural rainfall characteristics. Results indicate that sprinkler irrigation droplet landing velocity for all sizes of droplets is not related to nozzle pressure and the values of landing velocity are very close to that of natural rainfall. The velocity horizontal component increases with radial distance while the velocity vertical component decreases with radial distance. Additionally, landing angle of all droplet sizes decreases with radial distance. The kinetic energy is decomposed into vertical component and horizontal component due to the oblique angles of droplet impact on the surface soil, and this may aggravate soil erosion. Therefore the actual oblique angle of impact should be considered in actual field conditions and measures should be taken for remediation of soil erosion if necessary.</p>
5
Sawaguchi, Erina, Ayumi Matsuda, Kai Hama, Masafumi Saito, and Yoshiyuki Tagawa. "Droplet levitation over a moving wall with a steady air film." Journal of Fluid Mechanics 862 (January 8, 2019): 261–82. http://dx.doi.org/10.1017/jfm.2018.952.
Full textAbstract:
In isothermal non-coalescence behaviours of a droplet against a wall, an air film of micrometre thickness plays a crucial role. We experimentally study this phenomenon by letting a droplet levitate over a moving glass wall. The three-dimensional shape of the air film is measured using an interferometric method. The mean curvature distribution of the deformed free surface and the distributions of the lubrication pressure are derived from the experimental measurements. We vary experimental parameters, namely wall velocity, droplet diameter and viscosity of the droplets, over a wide range; for example, the droplet viscosity is varied over two orders of magnitude. For the same wall velocity, the air film of low-viscosity droplets shows little shape oscillation with constant film thickness (defined as the steady state), while that of highly viscous droplets shows a significant shape oscillation with varying film thickness (defined as the unsteady state). The droplet viscosity also affects the surface velocity of a droplet. Under our experimental conditions, where the air film shape can be assumed to be steady, we present experimental evidence showing that the lift force generated inside the air film balances with the droplet’s weight. We also verify that the lubrication pressure locally balances with the surface tension and hydrostatic pressures. This indicates that lubrication pressure and the shape of the free surface are mutually determined. Based on the local pressure balance, we discuss a process of determining the steady shape of an air film that has two areas of minimum thickness in the vicinity of the downstream rim.
6
Yan, Ming De, Han Ping Mao, and Wei Dong Jia. "Experimental Study on the Gas-Liquid Two Phase Flow of Air-Assist Boom Spraying." Applied Mechanics and Materials 341-342 (July 2013): 371–74. http://dx.doi.org/10.4028/www.scientific.net/amm.341-342.371.
Full textAbstract:
The velocity and diameter distribution of the air-assist boom spraying is studied by a laser Phase Doppler Partic1e Analyzer when the operational parameters is changed, which including airflow velocity of air curtain and vertical relative position between the air curtain and the nozzle. From the experimental results, we find the as the air curtain velocity increases , the size distribution of the droplet is conducive to uniform . At the same air curtain velocity, droplet size decreases with increasing of nozzle pressure. On the right side of each measuring point, the number of droplets is gradual decreasing with the wind velocity increasing.When the working pressure is 0.5Mpa, the droplet size does not change with the change of the horizontal distance.
7
Sardina, Gaetano, Stéphane Poulain, Luca Brandt, and Rodrigo Caballero. "Broadening of Cloud Droplet Size Spectra by Stochastic Condensation: Effects of Mean Updraft Velocity and CCN Activation." Journal of the Atmospheric Sciences 75, no. 2 (January 24, 2018): 451–67. http://dx.doi.org/10.1175/jas-d-17-0241.1.
Full textAbstract:
Abstract The authors study the condensational growth of cloud droplets in homogeneous isotropic turbulence by means of a large-eddy simulation (LES) approach. The authors investigate the role of a mean updraft velocity and of the chemical composition of the cloud condensation nuclei (CCN) on droplet growth. The results show that a mean constant updraft velocity superimposed onto a turbulent field reduces the broadening of the droplet size spectra induced by the turbulent fluctuations alone. Extending the authors’ previous results regarding stochastic condensation, the authors introduce a new theoretical estimation of the droplet size spectrum broadening that accounts for this updraft velocity effect. A similar reduction of the spectra broadening is observed when the droplets reach their critical size, which depends on the chemical composition of CCN. The analysis of the square of the droplet radius distribution, proportional to the droplet surface, shows that for large particles the distribution is purely Gaussian, while it becomes strongly non-Gaussian for smaller particles, with the left tail characterized by a peak around the haze activation radius. This kind of distribution can significantly affect the later stages of the droplet growth involving turbulent collisions, since the collision probability kernel depends on the droplet size, implying the need for new specific closure models to capture this effect.
8
Meng, Yanhua, Wanqiang Zhong, Yue Liu, Meimei Wang, and Yubin Lan. "Droplet Distribution of an Autonomous UAV-based Sprayer in Citrus Tree Canopy." Journal of Physics: Conference Series 2203, no. 1 (February 1, 2022): 012022. http://dx.doi.org/10.1088/1742-6596/2203/1/012022.
Full textAbstract:
Abstract Although Unmanned Aerial Vehicles (UAVs) are developed for military missions originally, they have been used widely in civil activities for several decades globally. In agricultural, UAVs have been developed as an efficient sprayer for pesticide application since 1987. UAV-based sprayers are popular for the prevention and control of pests and diseases in field crop in many countries recently. Some of the UAV-based sprayers are developed to be equipped with fruit tree mode aiming at solving droplet penetration in the inside and bottom part of the fruit tree canopy. In this study, a newly released UAV-based sprayer (i.e., T30) equipped fruit tree mode is chosen as spraying platform to optimize the spraying parameters for practical application. The flight velocity and application rate are the variables, while droplet coverage, density, size, and penetration are the observed metrics. Three treatments with different flight velocities (2 m s-1 or 3 m s-1) or application rates (60 L ha-1 or 75 L ha-1) are arranged to collect the droplets for assessment. Water Sensitive Papers (WSPs) are placed in the outside, bottom, and inside layers of the canopy to collect droplets. The results show that the treatment combined a flight velocity of 2 m s-1 and an application rate of 60 L ha-1 obtains the most droplets among all the variables based on the values of droplet coverage and density. The treatment with a flight velocity of 2 m s-1 and an application rate of 75 L ha-1 has the best penetration, while the treatment with a velocity of 2 m s-1 and an application rate of 60 L ha-1 takes the second place according to the percentages of droplet deposition in the three layers. Overall consideration of the total droplet distribution and penetration of the application parameters, a flight velocity of 2 m s-1 and an application rate of 60 L ha-1 are recommended to get an ideal droplet distribution in tree canopy when UAV-based sprayer T30 equipped with fruit tree mode flies at 1.6∼2 m above the citrus tree canopy.
9
Jia, Wei Dong, Cheng Li, Jun Lu, Ning Yang, and Zhen Tao Wang. "CFD Simulation of Spraying with Air Jet." Advanced Materials Research 455-456 (January 2012): 228–33. http://dx.doi.org/10.4028/www.scientific.net/amr.455-456.228.
Full textAbstract:
Droplet drift is always an accompaniment of pesticide spraying and can cause serious consequences. In this paper, we used a computational fluid dynamics software package (FLUENT) to analyze flow fields of spraying with air jet under different conditions in the tunnel model, and compared the effect of air jet on spray deposition and drift. Results of this study indicate that air jet can act directly on the spray droplets and affect their distribution and movement. Larger jet velocity has better performance on the drift reduction and droplet deposition. Droplets in the flow fields with larger jet velocity can get more kinetic energy and arrive at the root of crops easilier. When droplets are released straight down, larger velocity of droplets can be given and better performance can be achieved either in terms of drift reduction or droplet deposition.
10
Wang, Fei, Lin Wang, Guoding Chen, and Donglei Zhu. "Numerical Simulation of the Oil Droplet Size Distribution Considering Coalescence and Breakup in Aero-Engine Bearing Chamber." Applied Sciences 10, no. 16 (August 14, 2020): 5648. http://dx.doi.org/10.3390/app10165648.
Full textAbstract:
In order to improve the inadequacy of the current research on oil droplet size distribution in aero-engine bearing chamber, the influence of oil droplet size distribution with the oil droplets coalescence and breakup is analyzed by using the computational fluid dynamics-population balance model (CFD-PBM). The Euler–Euler equation and population balance equation are solved in Fluent software. The distribution of the gas phase velocity field and the volume fraction of different oil droplet diameter at different time are obtained in the bearing chamber. Then, the influence of different initial oil droplet diameter, air, and oil mass flow on oil droplet size distribution is discussed. The result of numerical analysis is compared with the experiment in the literature to verify the feasibility and validity. The main results provide the following conclusions. At the initial stage, the coalescence of oil droplets plays a dominant role. Then, the breakup of larger diameter oil droplet appears. Finally, the oil droplet size distribution tends to be stable. The coalescence and breakup of oil droplet increases with the initial diameter of oil droplet and the air mass flow increasing, and the oil droplet size distribution changes significantly. With the oil mass flow increasing, the coalescence and breakup of oil droplet has little change and the variation of oil droplet size distribution is not obvious.
Dissertations / Theses on the topic "Droplet velocity distribution"
1
Falahati, Hamid. "The Characterization of Bimodal Droplet Size Distributions in the Ultrafiltration of Highly Concentrated Emulsions Applied to the Production of Biodiesel." Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/19585.
Full textAbstract:
A non-reactive model system comprising a highly concentrated and unstable oil-in-water emulsion was used to investigate the retention of oil by the membrane in producing biodiesel with a membrane reactor. Critical flux was identified using the relationship between the permeate flux and transmembrane pressure along with the separation efficiency of the membrane. It was shown that separation efficiencies above 99.5% could be obtained at all operating conditions up to the critical flux. It was observed that the concentration of oil in all collected permeate samples using the oil-water system was below 0.2 wt% when operating at a flux below the critical flux. Studies to date have been limited to the characterization of low concentrated emulsions below 15 vol.%. The average oil droplet size in highly concentrated emulsions was measured as 3200 nm employing direct light scattering (DLS) measurement methods. It was observed that the estimated cake layer thickness of 20 to 80 mm was larger than external diameter of the membrane tube i.e. 6 mm based on a large particle size. Settling of the concentrated emulsion permitted the detection of a smaller particle size distribution (30-100 nm) within the larger particles averaging 3200 nm. It was identified that DLS methods could not efficiently give the droplet size distribution of the oil in the emulsion since large particles interfered with the detection of smaller particles. The content of the smaller particles represented 1% of the total weight of oil at 30°C and 5% at 70°C. This was too low to be detected using DLS measurements but was sufficient to affect ultrafiltration. In order to study the critical flux in the presence of transesterification reaction and the effect of cross flow velocity on separation, various oils were transesterified in another membrane reactor providing higher cross flow velocity. higher cross flow velocity provides better separation by reducing materials deposition on the surface of the membrane due to higher shearing. The oils tested were canola, corn, sunflower and unrefined soy oils (Free Fatty Acids (FFA< 1%)), and waste cooking oil (FFA= 9%). The quality of all biodiesel samples was studied in terms of glycerine, mono-glyceride, di-glyceride and tri-glyceride concentrations. The composition of all biodiesel samples were in the range required by ASTM D6751 and EN 14214 standards. A critical flux based on operating pressure in the reactor was reached for waste cooking and pre-treated corn oils. It was identified that the reaction residence time in the reactor was an extremely important design parameter affecting the operating pressure in the reactor.Natural Sciences and Engineering Research Council of Canada (NSERC)
2
Sushanta, Mitra. "Breakup Process of Plane Liquid Sheets and Prediction of Initial Droplet Size and Velocity Distributions in Sprays." Thesis, University of Waterloo, 2001. http://hdl.handle.net/10012/931.
Full textAbstract:
Spray models are increasingly becoming the principal tools in the design and development of gas turbine combustors. Spray modeling requires a knowledge of the liquid atomization process, and the sizes and velocities of subsequently formed droplets as initial conditions. In order to have a better understanding of the liquid atomization process,the breakup characteristics of plane liquid sheets in co-flowing gas streams are investigated by means of linear and nonlinear hydrodynamic instability analyses. The liquid sheet breakup process is studied for initial sinuous and varicose modes of disturbance. It is observed that the sheet breakup occurs at half-wavelength intervals for an initial sinuous disturbance and at full-wavelength intervals for an initial varicose disturbance. It is also found that under certain operating conditions, the breakup process is dictated by the initial varicose disturbance compare to its sinuous counterpart. Further, the breakup process is studied for the combined mode and it is found that the sheet breakup occurs at half- or full-wavelength intervals depending on the proportion of the individual sinuous and varicose disturbances. In general, the breakup length decreases with the increase in the Weber number, gas-to-liquid velocity and density ratios. A predictive model of the initial droplet size and velocity distributions for the subsequently formed spray is also formulated here. The present model incorporates the deterministic aspect of spray formation by calculating the breakup length and the mass-mean diameter and the stochastic aspect by statistical means through the maximum entropy principle based on Bayesian entropy. The two sub-models are coupled together by the various source terms signifying the liquid-gas interaction and a prior distribution based on instability analysis, which provides information regarding the unstable wave elements on the two liquid-gas interfaces. Experimental investigation of the breakup characteristics of the liquid sheet is performed by a high speed CCD camera and the measurement of the initial droplet size and distributions is conducted by phase-Doppler interferometry. Good agreement of the theoretical breakup length with the experiment is obtained for a planar, an annular and a gas turbine nozzle. The predicted initial droplet size and velocity distributions show reasonably satisfactory agreement with experimental data for all the three types of nozzles. Hence this spray model can be utilized to predict the initial droplet size and velocity distributions in sprays, which can then be implemented as a front-end subroutine to the existing computer codes.
3
Tien, Chi-Hsun, and 田棨薰. "R-134a/Distilled Water Spray Droplets Size(d32)Distribution and Velocity/Temperature Measurements." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/95296645089509705250.
Full textAbstract:
碩士國立中山大學
機械與機電工程學系研究所
93
Water and R-134a sprays as they impinge on the flat endplate of a circle are studied experimentally. In order to optimize water and R-134a sprays cooling efficiency, a detailed characterization and understanding of the spray formation is essentially needed. The effects of the jet exit velocity and Weber number on spray segregation are investigated. An optical image system was used to quantify the droplet size and distribution. LDV measurements were used to characterize the local velocity and velocity fluctuation distribution from a commercial available nozzle in both axial and radial directions. It is found in the water spray that local mean droplet diameter (SMD) decreases as jet exit velocity increases and as jet proceeds further downstream as well. Furthermore, the SMD and radial velocity are found to be the largest at the outer edges of the water spray. In contrast, the radial velocity is found to be the smallest at the outer edges of the R-134a spray. The SMD and radial velocity continuously decrease across both the water spray and R-134a spray toward the jet axis; while the corresponding axial velocity is the maximum there. Moreover, the R-134a spray jet heat transfer in non-boiling regime was shown to be dependent on the velocity of the impinging jets in terms of Weber number and other related parameters which are in good agreement with those of previous studies.
Book chapters on the topic "Droplet velocity distribution"
1
Ramirez de Santiago, Mario. "Measurement of Size and Velocity Distributions of Droplets Produced by Bubbles Bursting." In Applications of Laser Techniques to Fluid Mechanics, 203–26. Berlin, Heidelberg: Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-642-61254-1_11.
Full text
2
Rees, Andreas, and Michael Oschwald. "Experimental Investigation of Transient Injection Phenomena in Rocket Combusters at Vacuum with Cryogenic Flash Boiling." In Fluid Mechanics and Its Applications, 211–31. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-09008-0_11.
Full textAbstract:
AbstractThe substitution of the toxic hydrazine in current high-altitude rocket engines like upper stages or reaction control thrusters by green propellants is a major key driver in the current technology development of rocket propulsion systems. Operating these kind of rocket engines at high-altitude leads to a sudden pressure drop in the liquid propellants during their injection into the combustion chamber with a near-vacuum atmosphere prior to ignition. The resulting superheated thermodynamic state of the liquid causes a fast and eruptive evaporation which is called flash boiling. The degree of atomisation is important for a successful ignition and a secure operation of the rocket engine. The development and operation of a cryogenic high-altitude test bench at DLR Lampoldshausen enables the systematical experimental characterization of cryogenic flash boiling due to its ability to adjust and control the injection parameters like temperature, pressure or geometry. Several test campaigns with liquid nitrogen (LN2) were performed using two optical diagnostic methods: First, flash boiling LN2 spray patterns were visualised by means of high-speed shadowgraphy and, secondly, we determined the droplet size and velocity distributions in strongly superheated LN2 sprays with the help of a laser-based Phase Doppler system (PDA). The experimental data generated within these measurement campaigns provide defined boundary conditions as well as a broad data base for the numerical modelling of cryogenic flash boiling like e.g. the publications [8, 9].
Conference papers on the topic "Droplet velocity distribution"
1
Ommi, Fathollah, Ehsan Movahednejad, S. Mostafa Hosseinalipour, and Chien-Pin Chen. "Prediction of Droplet Size and Velocity Distribution in Spray Using Maximum Entropy Method." In ASME 2009 Fluids Engineering Division Summer Meeting. ASMEDC, 2009. http://dx.doi.org/10.1115/fedsm2009-78535.
Full textAbstract:
The distribution of sizes and velocities of droplets initially formed in sprays is an important piece of information needed in the spray modeling, because it defines the initial condition of the spray droplets in the predictive calculations of the downstream flow fields. The early stage of the atomization process (Primary Breakup) is clearly deterministic, whereas the droplet formation stage is random and stochastic. The stochastic aspect deals with the stage of droplet formation after the liquid bulk breakup by statistical means through the maximum entropy principle (MEP) based. The MEP provided model predicts atomization process while satisfying constrain equations of mass, momentum and energy. This model is capable for considering drag force on droplets downstream through a gas field. The model prediction is compared favorably with the experimentally measured size and velocity distribution for droplets, near the liquid bulk breakup region, produced by an air-blast annular nozzle. Therefore, the present model can be used to predict the initial droplet size and velocity distribution in droplet formation region of sprays.
2
Kolodnytska, Ruslana, Sergiy Skurativskyi, and Pavel Moskvin. "Maximum entropy method for biodiesel spray droplet distribution." In ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems. Valencia: Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/ilass2017.2017.4769.
Full textAbstract:
The efficiency of combustion process in diesel engine depends on the spray characteristics. The most importantof them are droplet size and velocity distributions. There are four methods which are used for describing the droplet size distributions: empirical, maximum entropy formalism (MEF), discrete probability function (DPF) and stochastic method. The MEF assumes that spray formation is a random process that can be described using the principle of maximum entropy. DPF method is a combination of random and non-random processes when the drop-size distribution appears from fluctuations in the initial conditions. Under the DPF approach the spray formation is divided into following steps: liquid breakup, ligaments separation, breakup of ligaments into fragments, fragment breakup into droplets. The stochastic breakup model assumes that the probability of formation of daughter droplet breakup size is independent of its parent size (a fractal scaling of breakup has been identified). This paper presents an investigation into the application of MEF model for distribution of biodiesel droplets. We used the model approach with the constraints: normalization, mass conservation, momentum conservation and surface energy conservation. The resulting probability density function (PDF) for velocity and droplet size is obtained by maximizing the Shannon entropy. We also used the new numerical algorithm to improve the model accuracy. The PDF for droplets diameters with different Weber numbers were calculated for both diesel and biodiesel fuels. The MEF predictions were compared against the experimental data for diesel and biodiesel droplet distribution with different injection pressure. According to the maximum entropy method, the influence of fuel thermodynamic properties on the parameters of drop-size and velocity distribution function forfuel sprays has been analysed.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4769
3
Zama, Yoshio, Masaaki Kawahashi, and Hiroyuki Hirahara. "Three-Dimensional Velocity and Droplet Size Measurements of Spray Flow (Keynote Paper)." In ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45206.
Full textAbstract:
The present investigation describes an application of a novel technique of simultaneous measurement of droplet size and three-dimensional components of velocity in a high density spray with swirl. The spray has a complicated and three-dimensional structure caused by mixing with surrounding airflow entrained by high speed fuel jet issuing from a nozzle. The breakup process of fuel film to fine-droplet-cloud, the droplet size dispersion and the velocity distribution of droplets are important factors in practical application of fuel spray for combustors. The conventional technique can be applied to local measurement of droplet speed and size. Recent methods, based on optical and image processing techniques, provide measurement of the velocity and droplet size distribution in observation area or volume. Maeda et al. proposed an excellent measurement technique of the size and the velocity distribution of droplet in spray based on interferometric laser imaging in which the fringe pattern is generated at the out of focus plane by interference between 0th order and 1st order refractions of droplet illuminated by high power laser light sheet. And also, in this technique, the separation of overlapping droplets image has been successfully done by optical method. As a practical application, the size and velocity distributions of droplets in a high density spray without swirl have been measured by this technique. In general, the droplet motion in a spray field is highly three-dimensional. Especially, a spray generated by a swirl nozzle shows complicated droplet motion in the three-dimensional field. In order to analyze the configuration of a complicated spray field, three-dimensional velocity measurement of droplets must be required. In the present paper, a combined measurement technique of the size and three velocity components of droplets in three-dimensional spray field based on doublet imaging technique of droplets and stereoscopic PIV method has been developed. And its feasibility and applicability was confirmed by practical application to measurements of spray fields induced by a swirl jet nozzle using in gas turbine.
4
Fan, Hua-Tzu, Harry Kuo, and Joseph Simmer. "Measuring Paint Droplet Size, Velocity, and Charge-to-Mass Ratio Distribution for Electrostatic Rotary Bell Spray Simulation." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-63556.
Full textAbstract:
High-speed electrostatic rotary bells are widely used in the automotive industry as they provide high quality paint films with better transfer efficiency compared to air-atomizing guns. However, due to its highly turbulent spray pattern, transfer efficiency is still not ideal, i.e. some portion of paint will not reach intended target surfaces and becomes overspray. Numerical simulation of the electrostatic spraying process provides a tool to model this process as well as a way to optimize transfer efficiency. Currently, the state-of-the-art simulation model can simulate the flying trajectories of paint droplets from the edge of the rotating bell cup to the target surfaces. It requires some input information to start the simulation. The input information includes paint droplet size, velocity, and charge-to-mass ratio. Due to its large number of droplets, distributions based on droplet diameters are used to represent the entire droplet population. This paper describes experimental and mathematical methods to measure and calculate paint droplet size, velocity, and charge-to-mass ratio distributions. The resulting information can then be organized and used as the input data files for Electrostatic spray painting simulation.
5
Gong, Yunyi, Xianguo Li, Zhijun Peng, and Xingyan Bai. "Number-Based Droplet Velocity Distribution in High Pressure Diesel Fuel Sprays." In International Off-Highway & Powerplant Congress & Exposition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 1994. http://dx.doi.org/10.4271/941689.
Full text
6
Brady, Michael R., Claude Abiven, Pavlos P. Vlachos, and George Papadopoulos. "Time-Resolved Spray-Droplet Velocity and Size Measurements via Single Camera Laser Sheet Imaging and Planar DPIV." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-33174.
Full textAbstract:
This paper describes a first effort to investigate the feasibility of droplet size and shape characterization by direct laser sheet imaging using time resolved Digital Particle Image Velocimetry. A 60-degree conical, high-pressure spray generated a poly-dispersed droplet distribution. Measurements were preformed for seven planes parallel to the spray axis, and separated by 4mm. A CMOS camera recorded the DPIV images at sampling rate of 10 KHz. Advanced image processing techniques were employed to identify the droplets and individually resolve their velocity using a hybrid cross-correlation particle-tracking algorithm. Subsequently, the size distribution of each droplet was quantified using geometric optics theory to convert the droplet image information to the true droplet size. Finally, the entire volume of the spray velocity and size distributions was reconstructed in a time-averaged sense. The droplet sizes from our direct imaging DPIV system were validated using a Phase Doppler Particle Analyzer (PDPA). The calculated sizes from the direct imaging methodology were found to agree with the measured PDPA results for droplets images larger than the diffraction limited diameter. Resolution limitations introduced inaccuracy for smaller droplets. In addition, the shedding frequency of the spray ligament was observed to be on the order of 1KHz, demonstrating the feasibility of using a high speed, direct imaging system in the characterization of unsteady, liquid sheet breakup properties. This preliminary effort illustrates the potential of performing global time resolved velocity and size measurements using a simple DPIV configuration based on CMOS imaging technology.
7
Wu, Puyuan, Jun Chen, Paul E. Sojka, Yang Li, and Hongjun Cao. "Experimental Measurement of Oil Droplets Size and Velocity Above the Rotor/Stator in a Rotary Compressor." In ASME 2021 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/fedsm2021-65874.
Full textAbstract:
Abstract Hundreds of millions of Air conditioning (AC) systems are produced each year. Many of them, especially small AC appliances, use rotary compressors as the system’s heat pump due to their simple structure and high efficiency in a small system. Lubricant oil is used in the rotary compressor to lubricate the moving parts, such as the crankshaft and the rolling piston, and to seal the clearance between the sliding parts, e.g., the clearance between the rolling piston and the cylinder, and the vane and the cylinder. As the compressed refrigerant vapor is discharged from the cylinder through the discharge port, part of lubricant oil in the cylinder would be carried by the vapor and atomize into small droplets in the lower cavity during the discharge process, which is complicated and highly-coupled. Some of these oil droplets would ultimately be exhausted from the compressor and enter other parts in the system, reducing the compressor reliability and deteriorating the heat transfer of the condenser and the evaporator in the system. Our previous research studied the atomization of the lubricant oil during the discharge process in the compressor’s lower cavity. However, the oil droplets’ behavior downstream of the lower cavity is unknown. Thus, studying the oil droplets’ behavior after passing through the rotor/stator can help understand how the rotor/stator would affect the droplet size distribution and movement, thus controlling the flow rate of escaped oil droplets. In this study, a hot gas bypass test rig is built to run a modified rotary compressor with sapphire windows right above the rotor/stator. The oil droplets’ size distribution and movement along the radial direction are obtained at the shaft’s rotating frequency of 30 and 60 Hz by shadowgraph. It is found that droplet size at 30 and 60 Hz varies little in the inner region of the rotor/stator clearance and would increase sharply above the clearance and keep increasing in the outer region of the clearance. More importantly, droplet velocity has a downward velocity component at the inner region and an upward velocity component at the outer region of the rotor/stator clearance. With the result of droplet size distribution and droplet velocity above the rotor/stator, we propose the model of the oil droplet’s path above the rotor/stator, which can be understood as the coupling of a swirling jet and a rotating disk.
8
Li, Qibo, and Jorge L. Alvarado. "Large Eddy Simulation of Emulsified Canola Oil Sprays in Swirl-Promoted Combustion Chamber." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-52413.
Full textAbstract:
A study has been undertaken to understand the effects of swirl-promoted turbulent flow on the spatial distribution of emulsified canola oil droplets. To fully understand the effects of swirling flow on fuel droplets, the discrete phase model (DPM) has been adopted to simulate straight vegetable oils (SVO) blend droplets. The stochastic break-up model has been used to simulate the aggregated dynamic behavior of fuel droplets in the combustion chamber. A robust and stable numerical algorithm has been selected and validated using experimental data in terms of mean flow velocity profiles and fuel droplet spray distribution using known fuel characteristics. The interaction between the swirling air flow and fuel droplets have been simulated using LES by considering two swirl numbers. The effects of swirl number on droplet spatial distributions in the combustion chamber have been considered and evaluated correspondingly. Specifically, the effects of air flow structure on fuel droplet distributions have been evaluated via numerical simulation. Results reveal that fuel droplet distribution is affected by the vortices generated by the swirler. Moreover, the results also indicate that swirl number (SN) has a distinct effect on the distribution of droplets and the evolution of vortices in the combustion chamber.
9
Kim, Hoi-San, Kyong S. Im, and Byung Ok Cho. "Development of measurement technique of droplet velocity and size distribution using PMAS." In High-Speed Photography and Photonics: 21st International Congress, edited by Ung Kim, Joon-Sung Chang, and Seung-Han Park. SPIE, 1995. http://dx.doi.org/10.1117/12.209545.
Full text
10
IJzermans, Rutger H. A., Rob Hagmeijer, and Ryan S. R. Sidin. "Calculation of Droplet Size Distribution in Condensing Flow." In ASME 2006 2nd Joint U.S.-European Fluids Engineering Summer Meeting Collocated With the 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/fedsm2006-98031.
Full textAbstract:
Condensing flows can be found in a large variety of industrial machinery such as steam turbines and supersonic gas conditioners. In many of these applications, it is very important to predict the droplet size distributions accurately. In the present research, the droplet size distribution in condensing flows is investigated numerically. We consider condensing flows with droplets that nucleate and grow, but do not slip with respect to the surrounding gas phase. To compute the coupling between the condensed phase and the carrier flow, one could solve the general dynamic equation and the fluid dynamics equations simultaneously. In order to reduce the overall computational effort of this procedure by roughly an order of magnitude, we use an alternative procedure, in which the general dynamic equation is initially replaced by moment equations complemented with a closure assumption. This closure assumption is based on Hill’s approximation of the droplet growth law. The method thus obtained, the so-called Method of Moments, is assumed to approximately accommodate the thermodynamic effects of condensation, such as the temperature, pressure and velocity field of the carrier flow. We use the Method of Moments as a basis for the calculation of the droplet size distribution function. We propose to solve the general dynamic equation a posteriori along a number of selected fluid trajectories, keeping the flow field fixed. This procedure, called Phase Path Analysis [1], leads to accurate size distribution estimates, at a far lower computational cost than solving the general dynamic equation and the fluid dynamics equations simultaneously. In the present paper, we investigate the effect of a variation in the liquid mass density on the droplet size distribution, using the proposed method. In case of a varying liquid mass density, both the equation for the dropltet growth rate and the moment equations are modified. This modified form coincides with the usual form of the moment equations in the event that the variation in liquid density is negligible. This research is relevant for condensation in flows where large temperature differences may occur which lead to significant variations in the liquid mass density. We show that the implementation of a variable liquid mass density in the Method of Moments and the Phase Path Analysis results in a higher extremum in the droplet size distribution, whereas the skewed shape of the distribution function is nearly similar to that obtained in the constant liquid density case.