spray dynamics

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Development of an Eulerian Lagrangian Method to Simulate Dispersed Multiphase Flows with Complex Spray Dynamics.

Development of an Eulerian Lagrangian Method to Simulate Dispersed Multiphase Flows with Complex Spray Dynamics.

A Lagrangian droplet tracking engine for three dimensional, structured, curvilinear multi-block grids has been developed and tested for a variety of flow conditions. A linear time search algo- rithm has been developed to allow for fast search of the cell which contains the droplet. Flow variables are interpolated to the droplet location using trilinear interpolation to calculate the forces acting on the droplet. The droplet is advected by accounting for various forces such as drag, lift and gravity, and the droplet position is integrated using a semi-implicit scheme. Phys- ical models to simulate droplet breakup and vaporization have been implemented in the engine in an effort to better simulate spray dynamics. Droplet breakup phenomenon is modeled using the Taylor Analogy Breakup (TAB) model. Multiple approaches to droplet generation have been considered based on the Cascade Analogy Breakup (CAB) model. Droplet vaporization has been modeled by evolving the droplet temperature and mass flow rate due to evaporation. Non equilibrium evaporation effects are included using the Langmuir-Knudsen law. The droplet engine can also handle immersed boundaries (IBs) in terms of droplet injection from marked IBs and droplet deposition on IBs in the domain. The developed engine is efficient enough to simulate tens of millions of droplets and is parallelized using OpenMPI using the same do- main decomposition as the CFD code. To this end, a new grid connectivity structure has been established and pre-computed.
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Measurement and CFD modelling of diesel engine spray dynamics

Measurement and CFD modelling of diesel engine spray dynamics

Chapter 2: This chapter focuses on the analysis of the spray structure at the SOI and Quasi- Steady stages of injection, considering each fluid as an incompressible continuum with constant density and viscosity in the absence of a cavitation model. Qualitative and quantitative experimental data from backlit imaging was used to validate the numerical results. This enables the validated CFD models to be used for further analysis of the spray dynamics and to clarify the impact of simultaneous physics on the fragmentation processes of the emerging liquid jet. The ability of Eulerian/VOF/LES-based CFD to reproduce the experimentally captured jet structure and penetration velocity and spray angle is demonstrated, showing that the selection of the boundary conditions, turbulence models and the quality of the mesh model can have a significant effect on the results. The influence of first and second order temporal discretization schemes and convection schemes on the computed morphology of the spray is been discussed and compared to experimental data. These results show that with a sufficiently fine mesh, and simulation conditions matching the experiments; the second order time derivative scheme and the Normalised Variable advection scheme give favourable comparisons with experimental measurements. The CFD methodology and key findings from Chapter 2 are used to provide the basis and support for the more comprehensive, complex and time-consuming simulations of in- and near-nozzle flow phenomena, as described in the subsequent chapters.
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Numerical and experimental analysis of
diesel spray dynamics including the
effects of fuel viscosity

Numerical and experimental analysis of diesel spray dynamics including the effects of fuel viscosity

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Numerical and experimental analysis of
diesel spray dynamics including the
effects of fuel viscosity

Numerical and experimental analysis of diesel spray dynamics including the effects of fuel viscosity

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Analysis of diesel spray dynamics using a compressible Eulerian/VOF/LES model and microscopic shadowgraphy

Analysis of diesel spray dynamics using a compressible Eulerian/VOF/LES model and microscopic shadowgraphy

injection pressure is not high, the liquid flow can re-attach to the walls downstream of the nozzle hole inlet 46.. [25, 26].[r]

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Design , Development and Analysis of multinozzle Coater-arm

Design , Development and Analysis of multinozzle Coater-arm

Numerical analysis is done to check whether the stresses are under permissible limit using ANSYS. As discussed earlier, parts which come in contact with process gases are made up of AISI304nmaterial having ultimate tensile strength 564MPa and Yield tensile strength 210MPa. In first case analysis is done to check rigidity of structure or frame which will be holding spray gun arm. Numerical analysis gives stress generated is 167.46Mpa that is less than allowable stresses and total deformation seen 0.82mm which is permissible. Fig 7(a) shows stress analysis of frame of coater arm and fig 7(b) shows total deformation of frame of spray coater arm. In second case stress analysis for entire spray arm system observed stress is 200.72MPa which is less than allowable stresses and total deformation observed is 0.418mm .Fig 7 (c) shows stress analysis of entire structure of coater arm and fig 7 (d) represent total deformation of coater arm structure.
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Analysis of heat transfer in spray cooling systems using numerical simulations

Analysis of heat transfer in spray cooling systems using numerical simulations

Roisman and Tropea (2004) presented hydrodynamic models for two extreme cases: (a) a very sparse spray impact characterized by small relative crown presence, such that the effect of their interaction can be neglected; and (b) a very dense spray impact. The velocities of the secondary droplets produced by the crown splash in a sparse spray were described theoretically. The fluctuations in the motion of the liquid film created by a dense impacting spray were analyzed statistically. This motion yields the formation of finger-like jets. The characteristic size and velocity of the film fluctuations were estimated. They validated two theoretical models against the experimental data and obtained good agreement. This agreement indicates that the inertial effect associated with drop impacts is the dominant factor in formation of the uprising sheets, whereas the capillary forces influence the velocity of the secondary droplets. They showed that the velocity of secondary droplets produced by very dense diesel spray impact are of the same order as the value of estimated characteristic velocity of film fluctuations and the average diameter of these secondary droplets is of order of the characteristic length of fluctuations.
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Study of a Pressurized Metered-dose Inhaler Spray Parameters in Fluent™

Study of a Pressurized Metered-dose Inhaler Spray Parameters in Fluent™

Abstract— The objective of this paper is to help fulfill the lack of information about the parameters needed to simulate a pressurized metered-dose inhaler (pMDI) spray (using a commercial computational fluid dynamics tool), providing future researchers the necessary information to study other pMDIs related devices, such as holding chambers. Following a previous bibliographic research about the characteristics of a pMDI spray, a further compilation was needed regarding the information to computationally define the spray in Fluent™. A very common drug asthma treatment (Ventolin®) was used in this study, with particles diameters going from 1.22 µm to 49.5 µm in a Rosin-Rammler distribution. The parameters were tested in Fluent™ (v6.3.26), using a three-dimensional “testbox” created especially for this purpose and meshed using the Gambit™ software (v2.2.30). The results showed that the selected parameters have produced a simulated spray very similar to the real one. It was also observed that the air behavior inside the “testbox” had a predictable response.
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DOE Modelling and Optimization of Tablet Coater Mechanism

DOE Modelling and Optimization of Tablet Coater Mechanism

The Coater is designed to coat tablets. The tablets are loaded into the product pan where they collect in the form of a product bed. The coating of the tablets within the product pan is achieved by means of spraying and dispersing the medium onto the product and then drying with preconditioned air. The rotating movement of the product pan and the mixing baffles prevents the tablets from sticking to each other and provides for a thorough mixture of the product as well as the necessary homogeneous distribution of the suspension. The spray medium is sprayed over the product bed through a spray nozzle. Depending on requirements, this can be done either continuously or through a series of programmed spray cycles. The tablets are dried by the process air that is sucked through the product bed. The discharge system allows a dust- and contamination-free discharge of the product bed. The outlet air fan produces negative pressure in the Coater throughout the process. Optimum product processing conditions can be selected to suit individual product requirements. Following table represents process parameters considered and their operating range for particular application.
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Optimization of working parameters for 3MGY-200 axial air-assisted sprayer in kiwifruit orchards

Optimization of working parameters for 3MGY-200 axial air-assisted sprayer in kiwifruit orchards

The final spray experiments were carried out on October 21, 2017 (Figure 5), in the most common Yangling kiwifruit orchards. The orchard was located 1500 km from Northwest A&F University. The orchard row spacing is approximately 1.9 m, the line spacing is approximately 3.0 m, the scaffolding height is 1.85 m above the ground, and the leaf canopy thickness is approximately 0.5 m. Water-sensitive paper (WSP) (26 cm by 76 cm; Syngenta, Greensboro, NC) was fixed on the two sides of the kiwifruit leaves to capture the spray results. The arrangement of the paper on the leaves is shown in Figure 5. A red nylon rope was used along the WSP positions to identify the paper after spraying. WSP is known as an accurate paper method because its surface is coated with the chemical indicator bromophenol blue [29] , and the colour changes from yellow to blue when the paper contacts water (Figure 6). A software deposit scan was used to analyse the percentage area covered by spray on each card, and the number of droplets were counted [30] .
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Effects of ambient density on flow characteristics of biodiesel spray injection using computational fluid dynamics

Effects of ambient density on flow characteristics of biodiesel spray injection using computational fluid dynamics

Efficiency of combustions engine is highly dependent on the formation of the air-fuel mixture prior to ignition. Both the homogeneity of the combustion process and the ignition process are largely dependent on the mixture properties. This study focuses on determining the spray characteristics of biodiesel blend in rapid compressions machine (RCM) by using simulation of ANSYS version 15.0 Fluent. The parameters investigated including spray angle, spray penetration, spray velocity, size diameter of particle, formations of spray, turbulence kinetics energy and spray area. The simulation was performed on three types of biodiesel blend which are B5, B10 and B15 at different ambient pressure and ambient density. Result shows that when in high ambient pressure, the spray of biodiesel angle decreased. The results also indicated that, the spray penetration length and spray area decreased with the increasing in the ambient density. The spray velocity also decreases as the ambient density increases. This study concludes that the ambient pressure and density strongly affected the characteristics of fuel spray.
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Fine nozzle characteristics for increasing filtration efficiency in commercial kitchen hood ventilation system

Fine nozzle characteristics for increasing filtration efficiency in commercial kitchen hood ventilation system

Due to the rising issues listed above, manufacturer implemented a water mist spray nozzle as an additional tool which used nontoxicity fluids (water) to be used in the kitchen area. Since the nozzle is utilised in a premise, thus the nozzles which produces a fine mist spray in low pressure condition is a major factor in consideration. Halton Company has selected a nozzle which complies the concept of deflector atomizer. This nozzle functioned as the first stage filtration system to trap the plumes before it passes through the second stage filtration system. However, there are still some weaknesses on the spray characteristic which affects the filtration efficiency. The conventional nozzle generated course water droplets, which resulted in the reduction of collision between water droplets and plumes. This will eventually leads to the reduction of filtration efficiency. Since the filtering system fails to capture the contaminant below the size of 2.5 micron, the targeted mist droplets size to be produced must be in the range of 1 micron to 3 micron.
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