Numerical study on pre-film atomization mechanism and characteristics by a coaxial swirl injector

2019 ◽  
Vol 233 (8) ◽  
pp. 1022-1038
Author(s):  
Qun Zhang ◽  
Xin Wang ◽  
Rui Kou ◽  
Chaochao Li ◽  
Peng Zhang ◽  
...  
Keyword(s):  
Liquid Film ◽  
Size Distribution ◽  
Droplet Size ◽  
Numerical Study ◽  
Droplet Size Distribution ◽  
Venturi Tube ◽  
Experimental Results ◽  
Two Stage ◽  
Spray Cone ◽  
Fuel Flow

The overall process and mechanism of the centrifugal pre-film atomization with double swirling flow were studied using the methods of large Eddy simulation and volume of fluid. The atomization process includes a centrifugal jet under the primary swirl and a pre-film atomization under the two-stage counter-rotating swirl at the venturi outlet. The fuel is ejected from the outlet of the centrifugal nozzle and undergoes the transient process of reaching the venturi throat. The breaking mechanism of liquid film in this process is the same as that of the formation mechanism of the mushroom-shaped tip of liquid jet. The numerical simulation results are highly consistent with the experimental results. For the formation and development of the liquid film on the venturi wall, collision and wave action promote the expansion of the liquid film. At the outlet position of the venturi tube, the short wave mode and the two-stage reverse swirling structure play major roles in the fragmentation process of the flake liquid film, which coincides with the flow characteristics given by the experiment. It is found that the spray cone angle increases as the fuel flow rate increases, and the numerical results are basically consistent with the predicted values of the empirical formula under different fuel flow rates. The droplet size distribution showed a Poisson distribution during the atomization of centrifugal jets and pre-film, and the peak position and variation trend of the droplet size distribution at the outlet of the venturi tube were basically consistent with experimental results.

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.

Measurement Based Atomization Model for Diesel Spray Evaporation and Combustion in a Matrix Burner

2011 ◽  
Author(s):  
Dieter Bohn ◽  
James Willie
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Gas Turbines ◽  
Cone Angle ◽  
Measurement Data ◽  
Droplet Size Distribution ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
The Matrix ◽  
The Right

This paper describes the development of an atomization model for implementation in a CFD solver. The model is developed for application in a matrix burner that is suitable for simulating the conditions prevailing in stationary gas turbines. The fuel considered is diesel and the matrix burner is designed using the Lean Premixed Prevaporized (LPP) concept. In this concept, the liquid fuel is first atomized, vaporized and thoroughly premixed with the oxidizer before it enters the combustion chamber. The injector used is a hollow-cone Schlick series 121–123 pressure-swirl atomizer. Extensive measurements are carried out at different atomization pressures to determine the right parameters like the nozzle diameter, atomization pressure and spray cone angle that will yield a good spray pattern. Based on the measurement data, the mass flow rate and the droplet size distribution are determined. The latter is determined by curve fitting the experimental data. The determined droplet size distribution is implemented in a Fortran subroutine that is hooked to the CFD solver. Cold flow CFD results are compared for different positions of the nozzle. The hot flow CFD results are also compared with the hot flow results obtained when the droplet size distribution is assumed to be uniform.

scholarly journals Effect of Inlet Tangential Port Area on the Performance of Small – Scale Simplex Atomizer

2012 ◽  
Author(s):  
Selvan G. Muthu ◽  
H. S. Muralidhara ◽  
Vinod Kumar Vyas ◽  
Kanth T. P. Dinesh ◽  
S. Kumaran ◽  
...  
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Cone Angle ◽  
Droplet Size Distribution ◽  
Small Scale ◽  
Sauter Mean Diameter ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Mean Diameter ◽  
Coefficient Of Discharge

An experimental investigation was conducted to study the effects of increased area of inlet tangential ports on the performance of small scale simplex atomizer. The spray characteristics of three different simplex atomizer representing increasing area of inlet tangential ports are examined using water as a working fluid. Measurements of coefficient of discharge, spray cone angle, Sauter mean diameter and droplet size distribution were carried out over wide range of injection pressure. Coriolis mass flow meter was used to measure coefficient of discharge. Spray cone angle was measured by image processing technique. Sauter mean diameter and droplet size distributions were measured by Malvern droplet sizing instrument. It was observed that with increase in area of inlet tangential ports the size of air core produced along the center line reduced, which increases the coefficient of discharge. Spray cone angle decreases with increase in area of inlet tangential ports. It was found that increase in area of inlet tangential ports reduces swirl strength inside swirl chamber, which results in increasing Sauter mean diameter. Better droplet size distribution was observed for lower area of inlet tangential port configuration. The obtained experimental results were compared with experimental correlations available in literatures. Deviations in the obtained experimental results and experimental correlations was observed. This is due to difference in the size of atomizer used and difference in experimental techniques used between the present work and other investigations.

An Experimental Study on the Heat Transfer of Traveling Airborne Water Droplets in Cold Environment

2015 ◽  
Vol 32 (2) ◽  
pp. 219-225 ◽  
Author(s):  
Y.-K. Chuah ◽  
J.-T. Lin ◽  
K.-H. Yu
Keyword(s):  
Heat Transfer ◽  
Low Temperature ◽  
Size Distribution ◽  
Droplet Size ◽  
Heat Balance ◽  
Droplet Size Distribution ◽  
Experimental Results ◽  
Rapid Freezing ◽  
Water Droplets ◽  
Temperature Environment

AbstractThis paper presents experimental results on rapid freezing of water droplets injected into a low temperature environment. A heat balance method was applied to determine the ratio of the water droplets frozen at the collection after the airborne time. The experimental results show that rapid freezing of water droplets could be achieved within three seconds of airborne time. Droplet size distribution of the frozen water droplets after collection was estimated. Heat transfer during the airborne time was calculated with consideration of the droplet size distribution. At attempt was taken to compare the heat transfer obtained with some previous studies on heat transfer of spherical objects in air. The research results show that droplet size distribution is important for the prediction of heat transfer of water droplets traveling in air. The results presented in this study contribute to the understanding of heat transfer of water droplets injected into a low temperature air.

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