Spray Characteristics of Non-Circular Nozzle in Air-Assisted Injection System

In order to analyze the spray characteristics of non-circular nozzle holes based on the air-assisted spray system, the spray characteristics of circular and non-circular nozzles were studied under the pressure of 0.2-0.6 MPa and the spray volume of 1000-5000 mL/h. Elliptical nozzle and triangular nozzle are classified as non-circular geometries. The spray cone angle was measured by processing the spray image captured by a CCD camera. The measured spray cone angles of the circular nozzles were analyzed, and the axis switching phenomenon of minor plane of elliptical nozzle was found during the test. Among the three shapes of nozzles, the elliptical nozzle had the largest spray cone angle, and the triangular nozzle had the smallest. The velocity field obtained depended on the PIV system. The results show that for axial velocity, elliptical orifice spray has greater kinetic energy and smaller droplet size under the same working parameters. Compared with the circular and elliptical nozzles, triangular orifice reached maximum spray velocity the fastest, but its velocity decay was the fastest. For radial velocity, away from the axis, the spray velocity of the elliptical orifice was less affected by the injection parameters, and the velocity was less than that of circular orifice and triangle orifice. Increasing air pressure will weaken radial propagation. The increase of liquid spraying rate had no remarkable effect on the increase of spraying rate. The results of particle size analysis show that the particle size of the non-circular orifice is reduced compared with that of the circular orifice, which promotes the breakup of droplets to a certain extent and enhances the atomization effect.

Spray Characteristics of Air-Assisted Injector Under Different Ambient Pressures

Spray atomization of liquid fuel plays an important role in droplet evaporation,combustible mixture formation and subsequent combustion process.Well-atomized liquid spray contributes to high fuel efficiency and low pollutant emissions.Gasoline direct injection(GDI)has been recognized as one of the most effective ways to improve fuel atomization.As a special direct injection method,the air-assisted direct injection utilizes high-speed flow of high-pressure air at the injector exit to assist liquid fuel injection and promote spray atomization at a low injection pressure.This injection method has excellent application potential and advantages for high performance and lightweight engines.In this study,the hollow cone spray emerging from an air-assisted injector was studied in a constant volume chamber with the ambient pressures ranging from 5 kPa to 300 kPa.External macro characteristics of spray were obtained using high speed backlit imaging.Phase Doppler particle analyzer(PDPA)was utilized to study the microcosmic spray characteristics.The results show that under the flash boiling condition,the spray will generate a strong flash boiling point which causes the cone shape spray to expand both inwards and outwards.The axisymmetric inward expansion would converge together and form a lathy aggregation area below the nozzle and the axisymmetric outward expansion greatly increases the spray width.The sauter mean diameter(SMD)of flash boiling condition can be reduced to 5μm compared to the level close to 10μm in the non-flash boiling condition.

Evaluation on Application and Spraying Effect of Air-Assisted Sprayer in Apple Orchard with Dwarfing Rootstocks

The application and spraying effect of 3 WG-1200 A air-assisted sprayer in dwarfing rootstock apple orchard were evaluated by investigating the droplet density, coverage and volume median diameter(VMD) in different canopy layers(2.0, 1.5, 1.0 m) and five directions(east, south, west, north and middle) of apple trees. The results showed that the droplet density was 166.99 per square centimeter, the coverage was 48.23%, and the VMD was 138.63 μm. The droplet density in different canopy layers of the trees had consistent trend with the coverage. The droplet density and coverage in the upper and middle canopy(2.0 m and 1.5 m) had no significant difference, but they were both higher than those in the lower canopy, while the VMD in different canopy layers showed an opposite trend. The change trends of the coverage and VMD in the five directions were consistent, and the values in the middle and east were the highest, followed by the north, south and west, respectively. The results indicated that droplet characteristics of the 3 WG-1200 A air-assisted sprayer met the basic requirements for pest and pathogen control. This study provides a theoretical basis and data support for the application and improvement of orchard application equipments in dwarfing rootstock apple orchard.

Simple decision-making model for orchard air-assisted spraying airflow

Airflow speed is one of the three factors of air-assisted spraying.Optimizing the matching model between airflow speed and target canopy characteristics is an effective way to improve the orchard precision spraying technology,as airflow can significantly affect droplet deposition and drift loss.A simple model of airflow speed was established in this study.First,air-assisted spraying experiments were carried out on a standard simulation canopy to study the airflow speed depended on canopy width,leaf area index,and porosity rate.Second,determined by Ribbon Method and verified by droplet drift data,the airflow speed through the canopy was between 0.5 m/s and 0.7 m/s.Third,multiple tests were carried out under standard simulation canopy with different characteristics,and the airflow speed model was established ultimately:with a fixed leaf area index(LAI),the relationship between canopy upwind boundary airflow speed and canopy width satisfied the exponential model(y=ae^(bx)),and the coefficients a and b are well related to the density of branches and leaves in the canopy.When LAI=3.456,y=2.036e^(1.5887x),R^(2)=0.994;LAI=1.728,y=1.639e^(1.445x),R^(2)=0.972.Orchard growers can acquire needed airflow speed through this simple model,it is quick and precise and appropriate to most growth periods of a variety of fruit trees,such as apples,pears,and vines.

Nozzle test system for droplet deposition characteristics of orchard air-assisted sprayer and its application

In order to obtain nozzle droplet deposition characteristics for sprayer mechanical design and variable spraying control algorithms,a nozzle droplet deposition characteristics test system for air-assisted spraying was designed.The test system can supply a stable wind site with precisely controlled air speed whose speed control ranges from 2 m/s to 16 m/s with maximum relative error of 4.5%.It can spray out a certain amount of liquid pesticide with adjustable spraying pressure which can be controlled with high precision while the maximum relative error is only 1.33%.The distribution of droplet deposition can be collected and measured by using the acquisition device and a pesticide deposition optical measurement system.The experiment of two-dimensional nozzle flow measurement was carried out.The results show that nozzle flow distribution is uniform and symmetric with“double-hump”shape in the spray range.Multi-nozzle overlapped droplet deposition ranges from 85%to 116%relative to the average.The nozzle droplet deposition experiment was completed.The experiment results show that in air-assisted spraying,the higher the wind speed,the less droplet deposition is affected by gravity.When the wind speed is higher than 12 m/s and spraying distance is 0.80 m,droplet deposition is concentrated on the originally designated point and hardly affected by gravity.The horizontal spray width becomes smaller with higher wind speed.When the wind speed is high,it can be considered that nozzle deposition only focuses on the nozzle center,if the position requirement is not very high in orchard spraying.

Seeding performance of air-assisted centralized seed-metering device for rapeseed

In order to analyze seed movement characteristics and improve seeding quality of air-assisted centralized metering device for rapeseed,the effects of the model-hole structure on seed feeding performance were investigated using EDEM simulation.Furthermore,the CFD-DEM coupling approach was applied to determine movement trajectories and airflow fields.The impacts of rapeseed varieties and rotational speed on seeding performance were investigated by bench tests.The results showed that the seed feeding quantity increased with the increase of model-hole’s length,depth and section size.Under the model-hole’s depth of 3.0 mm,the type II model-hole and model-hole’s length of 10 mm,both the variation coefficient of seed feeding quantity and hill diameter were lower which meet the seeding quantity requirement of 2 seeds in each hill.It was revealed that the seed population migrated in a large airflow velocity area and the distribution was uniform.The bench tests indicated that rapeseed varieties and rotational speed had a significant effect on the seed feeding quantity in each hill at rotational speed of 10-40 r/min.The variation coefficient of seed feeding quantity in each hill was less than 17.0%for each treatment.The hill diameter,which did not exceed 3.5 cm,tended to reduce with increasing rotational speed.The variation coefficient of seeding quantity in each row and seeding uniformity was less than 6.5%and 32.0%,respectively.Field experiments demonstrated that the seedling was 9-13 plants per meter each row for three rapeseed varieties.The variation coefficient of plants was less than 25.0%for six rows and their yields reached 2761 kg/hm2,which realized the mechanized planting requirements.The results can optimize structure of an air-assisted centralized metering system and improve seeding performance.

Design and test of a novel crawler-type multi-channel air-assisted orchard sprayer

In order to solve the problem of poor traveling stability and excessive pesticide application during plant protection operations in hilly orchards,a novel crawler-type multi-channel air-assisted sprayer that is particularly appropriate for hilly orchards was designed in this study.Considering anti-rolling requirements and the orchard environment in hilly areas,this study selected limits for uphill and downhill rolling angles as well as the transverse rolling angle as the evaluation indexes for determining both the layout and parameter settings of the sprayer.According to freely submerged jets and the requirements in plant protection operation,a multi-channel air-assisted system was developed.The test results showed that the anti-rolling performance and the designed air-assisted system were adequate.At 2 m from the longitudinal center plane of the sprayer,the airflow exhibited wavy distribution patterns under different parameter combinations since the four streams of the airflow were not thoroughly intersected and mixed.At 3 m from the longitudinal center plane of the sprayer,the jet was ejected at great velocity but underwent rapid attenuation;the airflow velocity in most areas barely satisfied the requirements for plant protection operation.In addition,different air outlet layout schemes led to significant differences in the spatial distribution of the airflow field.Compared with a traditional air-assisted sprayer,using the developed multi-channel air-assisted sprayer enhanced the droplet coverage uniformity by 19.4%,and the mean droplet deposition in the front,middle,and rear of the canopy was enhanced by 32.9%,50.3%,and 78.1%,respectively,while reducing ground deposition and air drift by 26.8%.

CFD simulation and experiment on the flow field of air-assisted ultra-low-volume sprayers in facilities

In order to explore the performance of the B-ULV-616A knapsack sprayer,computational fluid dynamics(CFD)was used to simulate the B-ULV-616A knapsack air-assisted device,which features an ultra-low-volume electric sprayer.Field experiments were carried out to test the spraying effects,and the KANOMAX anemometer was used to verify the simulated results.First,the internal and external flow fields and droplet deposition distribution of the ultra-low-volume sprayer were established.The results showed that the air-assisted spray device can change the airflow speed and direction and produce a high-speed swirling airflow at the outlet of the air-assisted spray device.The high-speed airflow(maximum of 83.5 m/s)generates negative pressure(minimum of 0.099 MPa)and causes a rapid increase in the droplet velocity and a secondary droplets spray,allowing droplets to reach a longer distance.Then,the maximum relative error was 20.14%,and its average value was 9.59%,indicating that the CFD method is suitable for the flow field analysis of the air-assisted spray device.Finally,based on the greenhouse experiment,the knapsack air-assisted ultra-low-volume electric sprayer was found to effectively improve the deposition on the rear of the crop,increase the droplet density(maximum of 81/cm2;droplet density of conventional electric sprayer is 64/cm2),and reduce the deposition amount and coefficient of variation(below 20%)within and between regions.Further,it managed to reduce pesticide use(by 69.85%)and rural non-point source pollution.

Effects of leaf response velocity on spray deposition with an air-assisted orchard sprayer

The interaction between leaves and airflow has a direct effect on the droplet deposition characteristics of the leaf canopy.In order to make clear the mechanism of droplet deposition in terms of the interaction between the droplets and leaves from the point of the leaf aerodynamic response velocity,the leaf movement under different airflow velocities and the influence of the leaf aerodynamic response on droplet coverage ratio were investigated.The effect of the aerodynamic response velocity of a leaf on the droplet deposition of the leaf surface was investigated.The aerodynamic characteristics of the leaf were analyzed theoretically.Boundary layer theory from fluid mechanics was used to develop a model of the leaf aerodynamic response velocity to nonperiodic excitations based on a convolution integral method.Target leaf aerodynamic velocities were detected using a high-speed camera,and the results indicated that the modeled leaf aerodynamic response velocity matched the measured values.At given conditions of spray liquid and leaf surface texture,the spray test showed that the droplet coverage ratio was influenced by the leaf aerodynamic response velocity,the droplet coverage ratio increased and then decreased with the leaf response velocity.Through analyze four droplets deposition state,the highest droplet deposition ratio and best deposition state on the leaf surface occur when the leaf aerodynamic response velocity was less than 0.14 m/s.According to the analysis of droplet deposition states,the uniformity of the droplet size and quantity distribution of droplets on the leaf surface related to the leaf aerodynamic response velocity.The results can provide a basis for the design and optimization of orchard air sprayers.

Tunnel-convective air-assisted spraying technology for improving droplet deposition on hedgerow vines

Given the impermeability,larger dosage,and higher drift of pesticides used in modern hedgerow vine canopies,a novel tunnel-convective air-assisted spraying technology was proposed.Mechanized spraying equipment with high penetration and low drift was developed.The air-assisted system of this equipment was centrosymmetric,and the fan type was cross-flow.The fan outlet width was 138 mm and the air duct’s main body followed a logarithmic spiral profile,based on parallel flow theory.The external diameter of the impeller was 157 mm,which was fixed into a barrel structure by 23 strong forward-curved blades,each being 1 mm thick.The central angle of the blades was 108°,and the ratio of the internal and external diameters was 0.81.The impeller and air duct served as guides to circulate and reciprocate airflow around the crown,forming a tunnel-convective air-assisted to the vine.Using MATLAB interpolation,the airflow trajectory of the air convection circulation in the door-shaped cover was obtained.The velocity field distribution test showed that,in the case of a canopy,there were tunnel-convective circulating airflows with high velocity on both sides and uniform velocity in the middle of the canopy.Due to the tunnel-convective air-assisted spraying technology,the vertical distribution uniformity of spray deposition has been significantly improved,spray penetration has been enhanced,penetrability has been effectively improved,and droplets on the ground and in the air have been significantly reduced.The results of this study can assist in providing further optimization and improvement of plant protection machinery.The new tunnel-convective air-assisted spraying technology may be a more favorable choice for future spray applications and the environment.

Design and performance test of a novel UAV air-assisted electrostatic centrifugal spraying system

In order to improve the deposition and uniformity of the pesticide sprayed by the agricultural spraying drone,this study designed a novel spraying system,combining air-assisted spraying system with electrostatic technology.First,an air-assisted electrostatic centrifugal spray system was designed for agricultural spraying drones,including a shell,a diversion shell,and an electrostatic ring.Then,experiments were conducted to optimize the setting of the main parameters that affect the charge-to-mass ratio,and outdoor spraying experiments were carried out on the spraying effect of the air-assisted electrostatic centrifugal spray system.The results showed the optimum parameters were that the centrifugal rotation speed was 10000 r/min,the spray pressure was 0.3 MPa,the fan rotation speed was 14000 r/min,and the electrostatic generator voltage was 9 kV;The optimum charge-to-mass ratio of the spray system was 2.59 mC/kg.The average deposition density of droplets on the collecting platform was 366.1 particles/cm^(2) on the upper layer,345.1 particles/cm^(2) on the middle layer,and 322.5 particles/cm^(2) on the lower layer.Compared to the results of uncharged droplets on the upper,middle,and lower layers,the average deposition density was increased by 34.9%,30.4%,and 30.2%,respectively,and the uniformity of the distribution of the droplets at different collection points was better.

Experimental Study and Numerical Simulation on Spray Characteristics of New-Type Air-Assist Nozzle

To investigate the spray characteristics of a new-type air-assist nozzle,three-dimensional laser phase Dopper analyzer( PDA) was used to measure the spray parameters. The external flow fields of the nozzle were simulated by means of computational fluid dynamics( CFD). The distributions of the diameter and the axial velocity for the droplets were analyzed respectively. The results indicate that,the mean diameter of the droplets fluctuates along the center axis. The distance between the measurement point and the nozzle increases,the axial velocity of the droplets decreases. The further the measurement point from the center axis is,the smaller the axial velocity of the droplets is. With the increase of the nozzle pressure drop,the axial velocity of the droplets improves while the mean diameter of the droplets is reduced,and the distribution uniformity of the droplets is better for the diameter. The simulation result agrees well with the experimental data. The average deviation ranges from 3.9% to 7.7%.

Effect of different drying methods on the taste and volatile compounds,sensory characteristics of Takifugu obscurus

Pufferfish is prone to deterioration due to abundant nutrients and high moisture content.Drying technology can extend the shelf life and enhance the flavor quality of aquatic products.The study investigated the effect of hot air drying(HAD),microwave vacuum drying(MVD)and hot air assisted radio frequency drying(HARFD)on the taste and volatile profiles of Takifugu obscurus.Different drying methods had significant influence on the color,rehydration,5’-nucleotides,free amino acids and volatile components(P<0.05).The results showed that HAD and HARFD could promote the flavor of T.obscurus by producing higher equivalent umami concentration(EUC)values,which were about two times of MVD group,and more pronounced pleasant odor according to sensory analysis.HAD is more appropriate for industrial application than HARFD and MVD considering the economic benefits.This study could provide a reference for the industrial application of drying T.obscurus.

Mixing Characteristics of Pulsed Air-assist Liquid Jet into an Internal Subsonic Cross-flow

Penetration depth,spray dispersion angle,droplet sizes in breakup processes and atomization processes are very important parameters in combustor of air-breathing engine.These processes will enhance air/fuel mixing inside the combustor.Experimental results from the pulsed air-assist liquid jet injected into a cross-flow are investigated.And experiments were conducted to a range of cross-flow velocities from 42～136 m/s.Air is injected with 0～300kPa,with air-assist pulsation frequency of 0～20Hz.Pulsation frequency was modulated by solenoid valve.Phase Doppler Particle Analyzer(PDPA) was utilized to quantitatively measuring droplet characteristics.High-speed CCD camera was used to obtain injected spray structure.Pulsed air-assist liquid jet will offer rapid mixing and good liquid jet penetration.Air-assist makes a very fine droplet which generated mist-like spray.Pulsed air-assist liquid jet will introduce additional supplementary turbulent mixing and control of penetration depth into a cross-flow field.The results show that pulsation frequency has an effect on penetration,transverse velocities and droplet sizes.The experimental data generated in these studies are used for a development of active control strategies to optimize the liquid jet penetration in subsonic cross-flow conditions and predict combustion low frequency instability.

Design and experiment of low-frequency ultrasonic nozzle integrating air-assistant system and acoustic levitation mechanism

Ultrasonic atomization nozzles are generally divided into two categories:high frequency and low-frequency ultrasonic atomization nozzles.Compared with high-frequency ultrasonic atomization nozzles(working frequencies>1 MHz),low-frequency ultrasonic atomization nozzles are not sensitive to clarity,temperature and viscosity of the liquid.However,they can control atomization quantity precisely,but the sizes of droplets generated by them are relatively large.In aeroponics cultivation,and precision welding,in such both cases,precise spraying control and tiny droplet sizes are expected.Therefore,how to decrease droplet size using low-frequency ultrasonic atomization nozzles is a valuable issue.In this paper a 60 kHz low-frequency ultrasonic atomization nozzle integrating air-assistant system and acoustic levitation mechanism was proposed and designed.Furthermore,the design was verified by FEA(Finite Element Analyzes)and impedance analyzer PV70A,and the verified results indicated relative design error was 0.49%.Driving voltage,spout angle,air pressure and levitating ball were taken as influential factors in the experimental protocol to the character in spray properties of this designed nozzle.A laser particle size analyzer was used to measure droplet sizes.Experiment results indicated that:the diameters of droplets generated by this nozzle at driving voltage 46 V were smaller than those at 40 V driving voltage;Both the assistant air and levitation mechanism could effectively change the diameters and uniformity of droplets;The minimum values of D10,D50,and D90(D10,D50 and D90 were mean diameters when cumulative percentages of the samples’diameter were 10%,50%and 90%,respectively)were 23.06μm,31.14μm and 41.38μm,respectively.However,all those minimum values were presented at the same run(spout angle 0°,air pressure 0.05 MPa,having levitated ball,driving voltage 46 V);Levitating ball above the atomization surface would make droplet sizes more uniform and tinier.More importantly,the famous Lang equation which assumes that droplet diameters just decided by the liquid surface tension,density and ultrasonic atomizer’s working frequency needed to be revised because experimental results indicated that changing vibration amplitudes of ultrasonic atomization surface might lead to the changing of the droplet diameters and those results were at odds with the Lang equation.

Multi-hierarchical flexible composites towards superior fire safety and electromagnetic interference shielding

Vast amounts of electromagnetic waves are generated in modern society,which severely endanger human health and cause instrument disturbance.Furthermore,practical application of electromagnetic shielding polymer-based materials aspires to flame retardancy.Herein,cellulose acetate butyrate modified ammonium polyphosphate(CAPP)and phosphoramide flame retardant decorated short carbon fiber(MSCF)were synthesized separately and then simultaneously blended into thermoplastic polyurethane(TPU)to prepare a series of flame retardant TPU composites.Then,the multi-hierarchical flexible TPU/CAPP/MSCF composites were fabricated via our self-developed air-assisted thermocompression method.The results revealed that the TPU/CAPP/MSCF showed improved thermal stability.Moreover,the TPU/10CA/2.5F incorporated with 10.0 wt.%CAPP and 2.5 wt.%MSCF respectively exhibited 77.8%and 58.6%reduction in peak of heat release rate(PHRR)and total heat release(THR),compared to those of pure TPU.In addition,the TPU/10CA/2.5F passed the UL-94 V-0 rating test and achieved a higher limit oxygen index(LOI)(27.3%)than pure TPU(21.7%).In the case of electromagnetic interference shielding effectiveness(EMI SE),the TPU/10CA/10.0F-SW with 10 wt.%CAPP and 10 wt.%MSCF dispersed in the surface layer and Ti_(3)C_(2)Tx MXene intercalated in the interlayer exhibited EMI SE of 43.8 dB in X band and 32.0 dB in K band.Summarily,synergistic effect between CAPP and MSCF together with scattered and multiply adsorbed effect of MSCF,MXene and CAPP was responsible for fire safety and EMI shielding property improvements.This work provides a fascinating strategy for fabricating multi-hierarchical flexible TPU composites with outstanding flame retardant and EMI shielding performances.