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.

Axial and Radial Variation of Spray Characteristics of a Small-Scale Simplex Atomizer

2014 ◽  
Author(s):  
Muthuselvan Govindaraj ◽  
Muralidhara Halebidu Suryanarayana ◽  
Vinod Kumar Vyas ◽  
Jeyaseelan Rajendran ◽  
Rajeshwari Natarajan ◽  
...  
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Radial Direction ◽  
Cone Angle ◽  
Injection Pressure ◽  
Droplet Size Distribution ◽  
Axial Direction ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Injection Pressures

Simplex atomizer is widely used in the liquid fuel combustion devices in aerospace and power generation industries. An experimental work was conducted, to study variation of SMD and droplet size distribution along axial and radial directions of the spray for different injection pressures. Malvern spray analyzer is used in the present investigation. Four different atomizer configurations of increasing atomizer constant (K) are examined using water and kerosene. Spray cone angle is measured for different configurations at different injection pressures (up to 30 bar) using image processing technique. In the case of atomizer with lower K, spray cone angle continuously increases with injection pressure. In the case of atomizer with higher K, initially spray cone angle increases significantly, but remains almost constant after 16 bar. Variation of SMD and droplet size distribution along axial direction of the spray is compared between water and kerosene spray. SMD variation along the axial direction of spray clearly shows the continuous brakup of droplets along axial direction of the spray. In the case of water spray, SMD rapidly decreases along the axial direction up to 30 mm from the orifice exit, and gradually decreases up to 120 mm. In the case of kerosene spray, SMD rapidly decreases along the axial direction up to 40 mm from the orifice exit, after that SMD fluctuates along the axial direction up to 100 mm from the orifice exit. This fluctuation is due to evaporation of smaller droplets (50 microns) of kerosene. Span also continuously fluctuates after 40 mm from the orifice exit in the case of kerosene spray. Variation of SMD and droplet size distribution along radial direction of the spray is compared for different injection pressure and configurations of simplex atomizer. Increase in injection pressure, increases the disruptive aerodynamic force, which reduces the radial peak value of SMD and widens the radial profile. With decrease in atomizer constant (K), swirl strength inside the swirl chamber increases, which in turn increases the spray cone angle. SMD variation along the radial direction of spray showed more uniform droplet diameter distribution for lower atomizer constant (K) configurations. Reducing the atomizer constant improves the atomization quality more effectively than increasing the injection pressure.

Study of Two Miniature Air-Assist Atomizers With Radial and Axial Air Swirlers

2006 ◽  
Author(s):  
Y. Levy ◽  
V. Sherbaum ◽  
V. Ovcharenko ◽  
V. Nadvani
Keyword(s):  
Droplet Size ◽  
Droplet Diameter ◽  
Cone Angle ◽  
Droplet Size Distribution ◽  
Spray Angle ◽  
Air Velocity ◽  
Liquid Pressure ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Air Channels

The performances of two types of miniature air-assist atomizers were investigated; one with air being directed to the liquid spray through radial-tangential air channels and the other with air supplied through a small axial swirler. The study has shown that droplet size is reduced significantly when the air velocity increases up to about 50 m/s. However, further increase in air velocity has only a weak effect on the droplet size. In the absence of air supply, elevating the liquid pressure causes a reduction in the droplet diameter. The maximum values of the droplet mass flux shifts to the spray periphery with increasing of air velocity. In the air-assist operational regime, the liquid pressure has a slight effect on SMD however; the spray cone angle is increased significantly and can achieve values of up to 120 degrees for low liquid pressure drop. The larger spray angle at comparable droplet size distribution makes the atomizers with the radial air swirlers more favorable for small jet engines.

scholarly journals Atomization Quality of Twin Fluid Atomizers for Gas Turbines

1982 ◽  
Author(s):  
M. M. Elkotb ◽  
M. A. Elsayed Mahdy ◽  
M. E. Montaser
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Gas Turbines ◽  
Cone Angle ◽  
Droplet Size Distribution ◽  
Diameter Ratio ◽  
Air Pressure ◽  
Sauter Mean Diameter ◽  
Flow Number ◽  
Mean Diameter

A detailed investigation of the effect of nozzle/needle diameter ratio, normal fuel area, swirler degree, air pressure, fuel pressure on flow number, cone angle and droplet size distribution of external mixing twin fluid atomizers is given in this paper. Forty atomizers have been constructed to prevent mutual effect of various parameters. Flow number and cone angle are found to increase with nozzle/diameter ratio, and to decrease with the increase of air pressure. Optimum fuel flow is obtained at swirler angle 30-deg, while cone angle increases with increase of swirler angle. Sauter mean diameter decreases with the increase of air pressure and decrease of fuel pressure. Suitable functions are derived for droplet size distribution, Sauter mean diameter, and flow number. They are suitable to predict the geometry of the atomizer and to be used also in a prediction model for the calculation of fuel concentration and heat release.

scholarly journals Breakup Processes and Droplet Characteristics of Liquid Jets Injected into Low-Speed Air Crossflow

Processes ◽  
2020 ◽  
Vol 8 (6) ◽  
pp. 676
Author(s):  
Lingzhen Kong ◽  
Tian Lan ◽  
Jiaqing Chen ◽  
Kuisheng Wang ◽  
Huan Sun
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Weber Number ◽  
Droplet Size Distribution ◽  
Droplet Velocity ◽  
Liquid Jet ◽  
Outlet Section ◽  
Low Speed ◽  
Jet Breakup ◽  
Breakup Mode

The breakup processes and droplet characteristics of a liquid jet injected into a low-speed air crossflow in the finite space were experimentally investigated. The liquid jet breakup processes were recorded by high-speed photography, and phase-Doppler anemometry (PDA) was employed to measure the droplet sizes and droplet velocities. Through the instantaneous image observation, the liquid jet breakup mode could be divided into bump breakup, arcade breakup and bag breakup modes, and the experimental regime map of primary breakup processes was summarized. The transition boundaries between different breakup modes were found. The gas Weber number (Weg) could be considered as the most sensitive dimensionless parameter for the breakup mode. There was a Weg transition point, and droplet size distribution was able to change from the oblique-I-type to the C-type with an increase in Weg. The liquid jet Weber number (Wej) had little effect on droplet size distribution, and droplet size was in the range of 50–150 μm. If Weg > 7.55, the atomization efficiency would be very considerable. Droplet velocity increased significantly with an increase in Weg of the air crossflow, but the change in droplet velocity was not obvious with the increase in Wej. Weg had a decisive effect on the droplet velocity distribution in the outlet section of test tube.

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.

Atomization Characteristics of Jatropha-Derived Alternative Aviation Fuels From Aircraft Engine Injector

2017 ◽  
Author(s):  
Ramachandran Sakthikumar ◽  
Deivandren Sivakumar ◽  
B. N. Raghunandan ◽  
John T. C. Hu
Keyword(s):  
Size Distribution ◽  
Drop Size ◽  
Cone Angle ◽  
Fuel Spray ◽  
Jet Fuels ◽  
Spray Characteristics ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Atmospheric Air ◽  
Atomization Characteristics

Search for potential alternative jet fuels is intensified in recent years to meet stringent environmental regulations imposed to tackle degraded air quality caused by fossil fuel combustion. The present study describes atomization characteristics of blends of jatropha-derived biofuel with conventional aviation kerosene (Jet A-1) discharging into ambient atmospheric air from a dual-orifice atomizer used in aircraft engines. The biofuel blends are characterized in detail and meet current ASTM D7566 specifications. The experiments are conducted by discharging fuel spray into quiescent atmospheric air in a fuel spray booth to measure spray characteristics such as fuel discharge behavior, spray cone angle, drop size distribution and spray patternation at six different flow conditions. The characteristics of spray cone angle are obtained by capturing images of spray and the measurements of spray drop size distribution are obtained using laser diffraction particle analyzer (LDPA). A mechanical patternator system comprising 144 measurement cells is used to deduce spray patternation at different location from the injector exit. A systematic comparison on the atomization characteristics between the sprays of biofuel blends and the 100% Jet A-1 is presented. The measured spray characteristics of jatropha-derived alternative jet fuels follow the trends obtained for Jet A-1 sprays satisfactorily both in qualitative and quantitative terms.

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