EFFECT OF THE DOWNWASH FLOW FIELD OF A SINGLE-ROTOR UAV ON DROPLET VELOCITY IN SUGARCANE PLANT PROTECTION

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.

Download Full-text

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

Recent Patents on Mechanical Engineering ◽

10.2174/2212797614666210531103433 ◽

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.

Download Full-text

<i>Simulation analysis and test for flow field and deposition concentration of small size unmanned plant protection helicopter</i>

10.13031/aim.201800137 ◽

2018 ◽

Author(s):

Qiang Shi ◽

Hanping Mao ◽

Xianping Guan

Keyword(s):

Flow Field ◽

Simulation Analysis ◽

Plant Protection

Download Full-text

Effects of Spray Parameters on the Effective Spray Width of Single-Rotor Drone in Sugarcane Plant Protection

Sugar Tech ◽

10.1007/s12355-020-00890-3 ◽

2020 ◽

Author(s):

Ping Zhang ◽

Wei Zhang ◽

Hai-Tian Sun ◽

Feng-Guang He ◽

Hai-Ba Fu ◽

...

Keyword(s):

Plant Protection ◽

Spray Parameters ◽

Sugarcane Plant

Download Full-text

Design of UAV Downwash Airflow Field Detection System Based on Strain Effect Principle

Sensors ◽

10.3390/s19112630 ◽

2019 ◽

Vol 19 (11) ◽

pp. 2630 ◽

Cited By ~ 4

Author(s):

Yalei Wu ◽

Lijun Qi ◽

Hao Zhang ◽

Elizabeth M. Musiu ◽

Zepeng Yang ◽

...

Keyword(s):

Wind Speed ◽

Flow Field ◽

Strain Gauge ◽

Wind Field ◽

Output Voltage ◽

Plant Protection ◽

Strain Effect ◽

Sampling Point ◽

Field Detection ◽

Finite Element Software

Accurate measurement of the downwash flow field of plant protection unmanned aerial vehicles (UAVs) is essential for analyzing the spatial distribution of droplets. To realize on-line rapid detection of the downwash flow field of a multi-rotor UAV, a flexible polypropylene detection device based on the principle of full bridge strain effect was proposed. Its performance principle was based on the physical deformation caused by wind pressure. The Fluid Flow and Static Structural modules of ANSYS 16.0 finite element software were used to simulate one-way fluid-solid coupling interaction. The surface of the resistive strain gauge embedded in the flexible detecting structure responded well to wind speed variation, hence it was suitable for downwash airflow wind field detection. By solving the strain force on the surface of the flexible detection structure, the length and layout of the grating wire of the strain gauge on the surface of the flexible detection structure were optimized. Meanwhile at 4 m·s−1 wind speed, the output voltage at varied bridge flexible acquisition systems in the acquisition card was measured. Results indicated coefficient of variation of 3.67%, 1.63% and 1.5%, respectively, which proved the good data acquisition consistency of the system. Through calibration test, the regression equation for the relationship between output voltage and wind speed for three unique sensor signal measuring circuits was established. The determination coefficients R2 for single bridge, half bridge and full bridge circuits were 0.9885, 0.9866 and 0.9959, respectively. In conclusion, by applying the multi-rotor plant protection UAV test platform, the results indicated the maximum relative error of the wind speed at each sampling point of the system at 1.0 m altitude was below 5.61%. Simulated and measured value had an RMSE maximum error of 0.1246 m·s−1. Moreover, downwash airflow detection not only has high accuracy but also has high sensitivity. Thus, there is convenience and practicability in the plant protection offered by this approach. The rapid measurement of UAV wind field and the established two-dimensional wind field model can provide a basis for precise application of agricultural aviation.

Download Full-text

Flow field induced particle accumulation inside droplets in rectangular channels

Lab on a Chip ◽

10.1039/c5lc00420a ◽

2015 ◽

Vol 15 (13) ◽

pp. 2879-2886 ◽

Cited By ~ 26

Author(s):

Michael Hein ◽

Michael Moskopp ◽

Ralf Seemann

Keyword(s):

Flow Field ◽

Internal Flow ◽

Droplet Velocity ◽

Topological Change ◽

Particle Accumulation ◽

Rectangular Channels

We present accumulation of sedimenting particles/cells within elongated droplets. Particle patterns evolve with droplet velocity, as explained by a topological change of the internal flow and the droplet's outer shape.

Download Full-text

Numerical Computation and Validation of Two-Phase Flow Downstream of a Gas Turbine Combustor Dome Swirl Cup

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.2815456 ◽

1995 ◽

Vol 117 (4) ◽

pp. 704-712 ◽

Cited By ~ 7

Author(s):

A. K. Tolpadi ◽

D. L. Burrus ◽

R. J. Lawson

Keyword(s):

Flow Field ◽

Phase Velocity ◽

Gas Turbine ◽

Gas Phase ◽

Frame Of Reference ◽

Droplet Velocity ◽

Phase Flow ◽

Gas Turbine Combustor ◽

Two Phase ◽

Good Agreement

The two-phase axisymmetric flow field downstream of the swirl cup of an advanced gas turbine combustor is studied numerically and validated against experimental Phase-Doppler Particle Analyzer (PDPA) data. The swirl cup analyzed is that of a single annular GE/SNECMA CFM56 turbofan engine that is comprised of a pair of coaxial counterswirling air streams together with a fuel atomizer. The atomized fuel mixes with the swirling air stream, resulting in the establishment of a complex two-phase flow field within the swirl chamber. The analysis procedure involves the solution of the gas phase equations in an Eulerian frame of reference using the code CONCERT. CONCERT has been developed and used extensively in the past and represents a fully elliptic body-fitted computational fluid dynamics code to predict flow fields in practical full-scale combustors. The flow in this study is assumed to be nonreacting and isothermal. The liquid phase is simulated by using a droplet spray model and by treating the motion of the fuel droplets in a Lagrangian frame of reference. Extensive PDPA data for the CFM56 engine swirl cup have been obtained at atmospheric pressure by using water as the fuel (Wang et al., 1992a). The PDPA system makes pointwise measurements that are fundamentally Eulerian. Measurements have been made of the continuous gas phase velocity together with discrete phase attributes such as droplet size, droplet number count, and droplet velocity distribution at various axial stations downstream of the injector. Numerical calculations were performed under the exact inlet and boundary conditions as the experimental measurements. The computed gas phase velocity field showed good agreement with the test data. The agreement was found to be best at the stations close to the primary venturi of the swirler and to be reasonable at later stations. The unique contribution of this work is the formulation of a numerical PDPA scheme for comparing droplet data. The numerical PDPA scheme essentially converts the Lagrangian droplet phase data to the format of the experimental PDPA. Several sampling volumes (bins) were selected within the computational domain. The trajectories of various droplets passing through these volumes were monitored and appropriately integrated to obtain the distribution of the droplet characteristics in space. The calculated droplet count and mean droplet velocity distributions were compared with the measurements and showed very good agreement in the case of larger size droplets and fair agreement for smaller size droplets.

Download Full-text

Biosecurity: tools, behaviours and concepts

Emerging Topics in Life Sciences ◽

10.1042/etls20200343 ◽

2020 ◽

Vol 4 (5) ◽

pp. 449-452

Author(s):

Alan MacLeod ◽

Nicola Spence

Keyword(s):

Plant Protection ◽

Human Life ◽

Animal Health ◽

Early Warning Systems ◽

Policy Makers ◽

Recent Developments ◽

Surveillance Programs ◽

Harmful Organisms ◽

The One ◽

Biosecurity Practices

COVID 19 has raised the profile of biosecurity. However, biosecurity is not only about protecting human life. This issue brings together mini-reviews examining recent developments and thinking around some of the tools, behaviours and concepts around biosecurity. They illustrate the multi-disciplinary nature of the subject, demonstrating the interface between research and policy. Biosecurity practices aim to prevent the spread of harmful organisms; recognising that 2020 is the International Year of Plant Health, several focus on plant biosecurity although invasive species and animal health concerns are also captured. The reviews show progress in developing early warning systems and that plant protection organisations are increasingly using tools that compare multiple pest threats to prioritise responses. The bespoke modelling of threats can inform risk management responses and synergies between meteorology and biosecurity provide opportunities for increased collaboration. There is scope to develop more generic models, increasing their accessibility to policy makers. Recent research can improve pest surveillance programs accounting for real-world constraints. Social science examining individual farmer behaviours has informed biosecurity policy; taking a broader socio-cultural approach to better understand farming networks has the potential to change behaviours in a new way. When encouraging public recreationists to adopt positive biosecurity behaviours communications must align with their values. Bringing together the human, animal, plant and environmental health sectors to address biosecurity risks in a common and systematic manner within the One Biosecurity concept can be achieved through multi-disciplinary working involving the life, physical and social sciences with the support of legislative bodies and the public.

Download Full-text