scholarly journals Numerical simulation of high-pressure gas atomization of two-phase flow: Effect of gas pressure on droplet size distribution

2019 ◽  
Vol 30 (11) ◽  
pp. 2726-2732 ◽  
Author(s):  
Kalpana Hanthanan Arachchilage ◽  
Majid Haghshenas ◽  
Sharon Park ◽  
Le Zhou ◽  
Yongho Sohn ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
High Pressure ◽  
Size Distribution ◽  
Droplet Size ◽  
Droplet Size Distribution ◽  
Gas Pressure ◽  
Phase Flow ◽  
Gas Atomization ◽  
Two Phase ◽  
Flow Effect

Two-Phase Flow Simulation of High-Pressure Gas Atomization: Effect of Molten Metal and Atomizing Gas Properties on Droplet Size Distribution

2019 ◽  
Author(s):  
Kalpana Hanthanan Arachchilage ◽  
Majid Haghshenas ◽  
Ranganathan Kumar
Keyword(s):  
High Pressure ◽  
Molten Metal ◽  
Droplet Size ◽  
Low Carbon Steel ◽  
Flow Simulation ◽  
Droplet Size Distribution ◽  
Gas Atomization ◽  
Low Carbon ◽  
Interfacial Instabilities ◽  
Two Phase

Abstract Numerical simulations of high-pressure gas atomization are performed by varying the molten metal and the atomizing gas to understand the physics behind high-pressure gas atomization and the effects of the melt and the atomizing gas on droplet size distributions. The Volume of Fluid method is used in the OpenFoam platform. The three melt-gas combinations used in these simulations are aluminum-nitrogen, aluminum-argon, and low carbon steel-nitrogen. Three interfacial instabilities have been identified in the early stages of all three atomization processes. Comparison of aluminum and steel as the molten metal indicates that steel atomizes more effectively and provides a higher yield than aluminum. However, changing the atomizing gas does not result in a significant change in the atomization process.

Thermal-Hydraulics of OC-OTEC Spout Flash Evaporators

1992 ◽  
Vol 114 (3) ◽  
pp. 187-196 ◽  
Author(s):  
S. M. Ghiaasiaan
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Two Phase Flow ◽  
Mechanistic Model ◽  
Droplet Size Distribution ◽  
Momentum Conservation ◽  
Phase Flow ◽  
Two Phase ◽  
Conservation Equations ◽  
Size Groups

A mechanistic model was developed for the thermal-hydraulic processes in the spout flash evaporator of an OC-OTEC plant. Nonequilibrium, two-fluid, conservation equations were solved for the two-phase flow in the spout, accounting for evaporation at the gas-liquid interface, and using a two-phase flow regime map consisting of bubbly, churn-turbulent and dispersed droplet flow patterns. Solution of the two-phase conservation equations provided the flow conditions at the spout exit, which were used in modeling the fluid mechanics and heat transfer in the evaporator, where the liquid was assumed to shatter into a spray with a log-normal size distribution. Droplet size distribution was approximated by using 30 discrete droplet size groups. Droplet momentum conservation equations were numerically solved to obtain the residence time of various droplet size groups in the evaporator. Evaporative cooling of droplets was modeled by solving the 1-D heat conduction equation in spheres, and accounting for droplet internal circulation by an empirical thermal diffusivity multiplier. The model was shown to favorably predict the available single-spout experimental data.

Numerical Simulation and Experiment of Atomization Field of Fan-Shaped Atomization Nozzle for Plant Protection UAV

2021 ◽  
Vol 14 ◽  
Author(s):  
Maohua Xiao ◽  
Yuanfang Zhao ◽  
Zhenmin Sun ◽  
Chaohui Liu ◽  
Tianpeng Zhang
Keyword(s):  
Numerical Simulation ◽  
Size Distribution ◽  
Droplet Size ◽  
Plant Protection ◽  
Cone Angle ◽  
Droplet Size Distribution ◽  
Droplet Velocity ◽  
Inlet Pressure ◽  
Spray Cone Angle ◽  
Spray Cone

Background: There are drift and volatilization of the droplets produced by the plant protection Unmanned Aerial Vehicle (UAV) under the influence of external wind speed and its flight speed. Objective: It studied the atomization characteristics of its fan-shaped atomizing nozzle under different inlet pressures and inner cavity diameters. Methods: For the start, the Realizable k-ε turbulence model, DPM discrete phase model and TAB breakup model are used to make a numerical simulation of the spray process of the nozzle. Then, the SIMPLE algorithm is used to obtain the droplet size distribution diagram of the nozzle atomization field. At last, the related test methods are used to study its atomization performance, and the changes of atomization angle and droplet velocity under different inlet pressures and inner cavity diameters and the distribution of droplet size are discussed. Results: The research results show that under the same inner cavity diameter, as the inlet pressure increases, the spray cone angle of the nozzle and the droplet velocity at the same distance from the nozzle increase. As the distance from the nozzle increases, the droplet velocity decreases gradually, the droplet size distribution moves to the direction of small diameter, and the droplets in the anti-drift droplet size area increase. Under the same inlet pressure, as the diameter of the inner cavity increases, the spray cone angle first increases and then decreases, and the droplet velocity at the same distance from the nozzle increases. As the distance from the nozzle increases, the droplet velocity decreases gradually, the droplet size distribution moves to the direction of large diameter, and the large size droplets increase, which cannot meet the anti-drift volatilization effect. Conclusion: Under the parameter set in this study, when the inlet pressure is 0.6MPa and the inner cavity diameter is 2mm, the atomization result is the best.

Kinetic Modeling and Monte-Carlo Simulations of Droplet Coalescence in a Turbulent Gas Flow

2002 ◽  
Author(s):  
Philippe Villedieu ◽  
Olivier Simonin
Keyword(s):  
Numerical Simulation ◽  
Monte Carlo ◽  
Kinetic Model ◽  
Size Distribution ◽  
Density Function ◽  
Droplet Size ◽  
Gas Flow ◽  
Droplet Size Distribution ◽  
Monte Carlo Algorithm ◽  
Droplet Coalescence

Two-phase gas-droplet flows are involved in a lot of industrial applications, especially in the combustion field (Diesel engine, turbomachinery, rocket engine,…). Among all the characteristics of the spray, the droplet size distribution generally has a major influence on the global performances of the system and must be accurately taken into account in a numerical simulation code. This is a difficult task because the carrier gas flow is very often turbulent. Hence, droplets located in the vicinity of the same point may have different velocities and coalesce, leading at the end to a strong modification of the initial droplet size distribution. The first part of our contribution will be devoted to the presentation of a new kinetic model for droplet coalescence in turbulent gas flows. This model is an extension, to the case of sprays, of the ideas introduced by Simonin, Deutsch and Lavie´ville in [1]. The key ingredient is the use of the “joint density function”, fgp (t, x, r, v, u), representing the density of droplets at time t, located at point x, with radius r and velocity v and “viewing” an instantaneous turbulent gas velocity u. The great advantage of using fgp (t, x, r, v, u) instead of the usual density function fp (t, x, r, v) is the possibility to close the collision operator, in the governing kinetic equation, with less restrictive assumptions on the velocity correlations of two colliding droplets. The link between this model and the usual one (relying on the so-called “chaos assumption”) will be discussed. In the second part of our contribution, we shall present a new Monte-Carlo algorithm derived from our kinetic model. Numerical simulation results, for some academic test cases (homogeneous isotropic turbulence), will be shown and compared to the results obtained with a classical algorithm for droplet collision, based on the chaos assumption (see for example [2] or [3]). The figure 1 below shows a comparison between the temporal evolution of the mass mean radius computed by a classical collision model (neglecting the influence of gas and droplet velocity correlation) and by the “joint-pdf” based model. In the first case, the growth rate of the droplet, due to coalescence phenomena, is overestimated. Moreover, figure 2 shows that the droplet kinetic energy, induced by the turbulent gas motion, decays rapidly with the chaos assumption based model, as already noticed by Lavie´ville et al [1] in the case of solid particle collisions.

Study on atomization particle size characteristics of two-phase flow nozzle

2021 ◽  
pp. 1-12
Author(s):  
Haoqi Lilan ◽  
Junbin Qian ◽  
Nan Pan
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Droplet Size ◽  
High Speed ◽  
Droplet Size Distribution ◽  
Average Diameter ◽  
Spray Atomization ◽  
Two Phase ◽  
Nozzle Pressure ◽  
Local Observation

Nozzle spray atomization is widely used in industrial and agricultural production processes and is a very complicated physical change. The spray atomization of the nozzle is a process in which the droplets are continuously broken into finer particles under the action of force, in order to study the effect of nozzle atomization, that is, droplet size distribution characteristics. The experimental average mathematical model of droplet size distribution was established by introducing the average diameter of Sutter (SMD). The droplet size distribution in the atomization field of the nozzle is studied by simulation. In the experimental study, the high-speed camera, external mixing air atomizing nozzle platform experimental device and image processing were used, and the atomization field was divided into multiple observation areas. Through the measurement of several local observation areas, the droplet size distribution of the whole atomization field is constructed. It provides a reference for the study of the atomization field of the nozzle and a basis for the intuitive understanding of the droplet size distribution in the atomization field of the nozzle. The effective atomization area of the nozzle atomization was selected to study the influence of the liquid flow rate, the liquid temperature and the nozzle pressure on the atomized particle size distribution of the externally mixed atomizing nozzle. The internal law is obtained, which provides a basis and reference for effectively controlling the atomization effect in the atomization field.

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