Spray Droplet Distribution Research Articles

Analyzing the Nozzle Spray Fan Pattern of an Agricultural Sprayer Using Pulse Width Modulation Technology to Generate an On-Ground Coverage Map

Chemical application is an integral part of crop care. Today, advanced sprayers automatically control individual boom sections and nozzles to accommodate increased machine sizes and travel speeds, yet automatic control of flow-based systems raises concerns regarding coverage accuracy and uniformity during changes in travel speed and spray swath width. New commercial systems apply product at a constant pressure using varied duty cycles of pulse width modulated (PWM) solenoids to maintain a constant application rate. However, concerns exist regarding the dynamic effect of solenoid on/off latency on spray fan pattern and spray coverage. The objectives of this study were to investigate the on/off latency in PWM nozzles, determine if active nozzles affect spray fan pattern latency, and develop flow characteristics to simulate dynamic spray coverage. A PWM system and flow rate controller were installed on a 6.6 m three-section boom sprayer with 13 nozzles. A Raven Viper 4 controller regulated the product flow rate and pressure, while a Capstan Pinpoint controller was used to set the system pressure, nozzle on/off configuration, and duty cycle. The results indicated that the PWM spray system maintained the pressure within ±5% of the target value and applied an accurate amount of flow per pulse regardless of the number of nozzles activated. There was a 20 ms delay in nozzle pressure development during each cycle, and the delay was constant regardless of the number of nozzles activated. After de-energizing the solenoid, the nozzle continued spraying at system pressure for 10 ms. Static spray droplet distribution proved that the system applied the correct volume per pulse. In addition, PWM duty cycles of 100%, 80%, 60%, and 40% provided spray coverage within ±10% of the target rate for 100%, 94%, 77%, and 67% of the time, respectively. Greater signal overlap between odd and even nozzles increased the application coverage. Dynamic spray simulations showed that as-applied application error may vary beyond ±10% of the target rate. As such, while the PWM system provided the desired amount of product per pulse, the spray coverage results indicated that the on-ground coverage could result in areas with under- or over-application.

A novel detection method of spray droplet distribution based on LIDARs

During the process of plant protection in agriculture, the distribution and deposition of droplets or fog fields could directly influence the effectiveness and efficiency of spray. The traditional method of measurement of the distribution of droplets mainly used water sensitive papers, glass containers or flour to collect data and inverse results, while a new method of measurement based on the principle of reflection of LIDAR was presented. Droplets were the major targets of the study, and four important algorithms were primarily developed, including the recognition and extraction of targets, the superposition in time-domain, the calculation of effective ranges of distribution, and the development of 3D distribution models. Combined with these algorithms, in order to eliminate the environmental noise, the methods of Fuzzy Environment Matching and Secondary Filter were created and utilized. Meanwhile, the statistics was used for analysis of the duration of scanning as well as computation of the distribution, with enough datasets but the minimum length of time. The results of the experiments showed that the relative error of measurement was less than 7% and Relative Standard Deviation was less than 16%, compared with the values of manual measurement. Furthermore, the 3D models were accurate and clarified in the wind-tunnel experiment. The completed system based on this method could adapt to the requirements of both indoor and outdoor detection. Besides, it is capable of the quantized detection of droplet distribution, providing an effective way of tests for spray technique, especially for the research of the application of plant protection by UAVs. Keywords: droplets, distribution, detection, agricultural aviation, UAV DOI: 10. 25165/j.ijabe.20171004.3118 Citation: Zheng Y J, Yang S H, Lan Y B, Hoffmann C, Zhao C J, Chen L P, et al. A novel detection method of spray droplet distribution based on LIDARs. Int J Agric & Biol Eng, 2017; 10(4): 54–65.

Tomographic imaging of the liquid and vapour fuel distributions in a single-cylinder direct-injection gasoline engine

This article reports the application of optical tomography and chemical species tomography to the characterisation of the in-cylinder mixture preparation process in a gasoline, direct-injection, single-cylinder, motored research engine. An array of 32 near-infrared beams is transmitted in a horizontal plane across the cylinder bore near the top of the cylinder, through a circular quartz annulus. A novel approach to enable the optical alignment of the transmitting and receiving optics is utilised. The engine is operated at a stoichiometric condition at 1200 r/min, with negative valve overlap timing. Two tomographic measurement schemes (optical attenuation and chemically specific absorption) were used to acquire data on the spatial and temporal distribution of fuel throughout the engine cycle. Optimised data pre-processing methods are described for maximal beam count and data reliability. The presence of fuel during the intake stroke was detected by the optical beam attenuation due to scattering from the liquid gasoline droplets. Optical tomographic reconstruction of the spatial distribution of these droplets was achieved at an imaging rate of 7200 frames per second, revealing rapid intra-cycle spatial variations that were consistent between consecutive cycles. During the compression stroke, chemical species tomography images of fuel vapour were reconstructed from data acquired using chemically selective spectral absorption by the hydrocarbon molecules, at an imaging rate of 2400 frames per second. Later in the compression stroke, the temporal evolution of the fuel vapour distribution in the plane of observation is relatively slow and displays inhomogeneities that are consistent between consecutive cycles. This is the first report of the use of tomography to image, within individual engine cycles, the in-cylinder evolution of both fuel spray droplet distribution and fuel vapour distribution.

Characterization of the Acoustic Interactions in a Two-Stage Multi-Injection Combustor Fed With Liquid Fuel

Burners operating in lean premixed prevaporized (LPP) regimes are considered as good candidates to reduce pollutant emissions from gas turbines. Lean combustion regimes result in lower burnt gas temperatures and therefore a reduction on the NOx emissions, one of the main pollutant species. However, these burners usually show strong flame dynamics, making them prone to various stabilization problems (combustion instabilities, flashback, flame extinction). To face this issue, multi-injection staged combustion can be envisaged. Staging procedures enable fuel distribution control, while multipoint injections can lead to a fast and efficient mixing. A laboratory-scale staged multipoint combustor is developed in the present study, in the framework of LPP combustion, with an injection device close to the industrial one. Using a staging procedure between the primary pilot stage and the secondary multipoint one, droplet and velocity field distributions can be varied in the spray that is formed at the entrance of the combustion chamber. The resulting spray and flame are characterized using OH-planar laser induced fluorescence, high speed particle image velocimetry, and phase Doppler anemometry measurements. Three staging values, corresponding to three different flame stabilization processes, are analyzed, while power is kept constant. It is shown that mean values are strongly influenced by the fuel distribution and the flame position. Using adequate postprocessing, the interaction between the acoustic field and the droplet behavior is characterized. Spectral analysis reveals a strong acoustic-flame coupling leading to a low frequency oscillation of both the velocity field and the spray droplet distribution. In addition, acoustic measurements in the feeding line show that a strong oscillation of the acoustic field leads to a change in fuel injection, and hence droplet behavior.

SPRAY CHARACTERISTICS OF DIESEL FUEL CONTAINING DISSOLVED CO2

The effect of adding CO 2 to diesel fuel has been previously studied by seve ral groups that used tailored made injection systems with which rem arkable low SMD's were archived. In the present study we use a real commercial fuel inj ection system and studied the effect of the amount of dissolved CO 2 on the resulted spray characteristics. In this cas e, when the mixture enters the injector and flows downstream through th e variable cross-sections duct, partial nucleation is expected to occur at different locati ons along the duct and a part of the dissolved gas is transformed into tiny bubbles that grow fast downstream. When the mixture is driven out through the discharge orifice, these bubbles un dergo a rapid flashing process resulting a rapid disintegration of the liquid bulk into small droplets. In the present study, an experimental study of steady-state atomization proc ess of diesel fuel containing dissolved CO 2, is presented. An extensive study was performed to map the effect of the CO 2 content on the spray SMD and droplet distribution at different locations downstream the discharge orifice, and also on the spray angle. The spray cha racteristics (SMD, D 0.1 , and Span factor) were measured with a laser particle size analyzer ( Malvern X-Mastersizer), and a digital camera was employed to record the spray angle. An overall analysis has been performed to evaluate the advantage of the proposed method over its counterparts, in terms of the total energy required to produce a desired spray. It is c oncluded that the atomization of diesel fuel containing dissolved CO 2, is significantly promoted by the flash-boiling ph enomenon to result low SMD sprays. It was also found that the s pray structure of a fuel/dissolved gas mixture is essentially different from that of a sin gle-component fuel.

Large Eddy Simulation of Spray Injection to Turbulent Flows from a Slit Nozzle

Slit nozzles are used in some gasoline direct injection engines and make fan shaped spray. Spray injecting flows to turbulent flows from a slit nozzle have been analyzed numerically using combination of Large Eddy Simulation (LES) and lagrangian Discrete Droplet Method (DDM). As a result, LES can resolve the internal structure of the spray and irregular droplet distribution made by small eddies that momentum of spray itself induced. In conventional Reynolds Averaged Navier-Stokes (RANS) combined DDM calculation such eddies cannot be resolved, and also the internal spray structure or irregularity doesn't appear since all effects of turbulence are averaged. But such structure or irregularity is important for stable combustion in gasoline direct injection engines. Therefore the combination of LES and DDM method will play essential role for developing more robust and high efficient engines under wide operating conditions. We also proposed the way of constructing pseudo particle image in order to compare calculation results with sliced spray pictures obtained by experiments. We show time changes of the shape of brightness Probability Density Function (PDF) can be used to evaluate variance of spray droplets.

Spray Stress Revisited

Abstract In winds approaching hurricane strength, spray droplets proliferate. Once created, these droplets accelerate to the local wind speed in 1 s or less and thereby extract momentum from the wind. Because these droplets have substantial mass, they eventually plunge back into the ocean, delivering their horizontal momentum to the surface in the form of a spray stress. Inadequate information on the production rate and size distribution of spray droplets, however, hampered previous attempts to estimate the magnitude of this spray-mediated momentum exchange. This paper therefore uses recent estimates of the spray generation function to reconsider spray's ability to alter air–sea momentum exchange. Conservation of momentum requires that spray cannot enhance the air– sea stress beyond what the large-scale flow dictates. However, spray can redistribute stress in the near-surface atmosphere since the wind must slow if the spray droplets accelerate. For a wind of 30 m s−1, spray supports about 10% of the surfa...

Effect of Formulation and Nozzle Type on Droplet Size with Isopropylamine and Trimesium Salts of Glyphosate

When spray mixtures were examined using a laser spray droplet analyzer, the new isopropylamine glyphosate formulation produced more small droplets than a previous isopropylamine salt of glyphosate formulation or glyphosate–trimesium plus nonionic surfactant. The use of a pre-orifice flat-fan nozzle and an impact type flat-fan nozzle reduced the amount of small droplets produced compared to an existing extended range flat-fan nozzle, while maintaining a spray droplet distribution that could still provide good weed control. The new nozzle technologies could provide a useful management tool to manage potential drift situations.

Performance of Image Analysis for Assessment of Simulated Spray Droplet Distribution

Various distribution patterns of spray droplets were simulated with Autosketch V.2 software and images of specks were printed on a Laserjet 2 printer. The specks were studied with a Dapple Systems image analyzer and Imageplus+ software. The objectives were to evaluate the utility of image analysis for spray deposition assessment and determine the effects of image area, speck size, and number of specks on the accuracy of the measurements.

Behavioral responses of Ceratitis capitata flies to bait spray droplets and natural food

AbstractIn studies carried out on field‐caged non‐fruiting host trees, we examined effects of environmental and adult physiological and experiential state factors on responses of released Mediterranean fruit flies, Ceratitis capitata (Wiedemann), to droplets of proteinaceous bait (PIB‐7) with or without 20% insecticide (malathion). We confirmed that fresh PIB‐7 is both attractive and phagostimulatory to proteindeprived medflies and found that presence of 20% malathion ultra low volume concentrate (ULVC) in PIB‐7 droplets does not significantly repel medflies from approaching droplets but does significantly deter feeding on them. A single relatively fresh deposit of bird feces, an important source of protein for medflies in natural environments, attracted several times more laboratory‐cultured and wild medflies than 20 droplets of 80% PIB‐7/20% malathion ULVC (about the average number of droplets per m2of plant canopy in aerial bait spray programs). Attraction to protein was significantly greater among wild medflies deprived of protein continuously from eclosion than among wild medflies that had recent (within 3 days) or continuous access to protein. Attraction to protein increased significantly with increasing age (2, 7 and 12 days) of protein‐deprived wild medflies. But we found no significant positive impact of recent brief experience of wild medflies with protein on degree of subsequent attraction to protein. In final experiments that mimicked the size, density and distribution of bait spray droplets on tree foliage typical for an aerial medfly control program, very few (4%) or no released protein‐deprived wild medflies found a bait droplet within the 15 min test period even though most found a single deposit of bird feces. We conclude that the effectiveness of aerial bait sprays against medflies might be enhanced substantially (and the proportion of infested area treated with bait spray reduced considerably) by (1) including synthetic equivalents of attractive components of bird feces in the spray mixture, and (2) adjusting spatial and temporal patterns of bait spray applications according to estimates of the composition and abundance of natural medfly food and the age structure of medfly adult populations in infested regions.

Impinging jets atomization

An analysis of the characteristics of the spray produced by an impinging-jet injector is presented. Predictions of the spray droplet size and distribution are obtained through studying the formation and disintegration of the liquid sheet formed by the impact of two cylindrical jets of the same diameter and momentum. Two breakup regimes of the sheet are considered depending on Weber number, with transition occurring at Weber numbers between 500 and 2000. In the lower Weber number regime, the breakup is due to Taylor cardioidal waves, while at Weber number higher than 2000, the sheet disintegration is by the growth of Kelvin–Helmholtz instability waves. Theoretical expressions to predict the sheet thickness and shape are derived for the low Weber number breakup regime. An existing mathematical analysis of Kelvin–Helmholtz instability of radially moving liquid sheets is adopted in the predictions of resultant drop sizes by sheet breakup at Weber numbers greater than 2000. Comparisons of present theoretical results with experimental measurements and empirical correlations reported in the literature reveal favorable agreement.

Interaction Between Spray Distribution and Systemic Activity of Insecticides for Control of European Corn Borer (Lepidoptera: Pyralidae) in Peppers and Snap Beans

Interactions between spray distribution and insecticide mode of action in relation to control of European corn borer, Ostrinia nubilalis (Hubner), on bell peppers ( Capsicum annuum L.), sweet banana peppers ( Capsicum annuum L.), and snap beans ( Phaseolus vulgaris L.) were investigated. Multiple treatments were applied using either a conventional boom sprayer or an air-curtain sprayer. Materials evaluated were fenvalerate (local activity) and acephate (systemic activity). Spray droplet distribution was evaluated with UV-spectrophotometric analysis of sprayed dyes. European corn borer egg massey were sampled weekly during the experiment, and crop injury was evaluated at harvest. Spray deposition with the air-curtain sprayer was much higher on the undersides of the leaves and on fruit than with the conventional boom application. Variability of spray deposition between samples also was reduced. Faceplate and fenvalerate significantly reduced banana pepper and bell pepper injury from European corn borer. However, significant reductions in injury due to air-curtain application occurred only with fenvalerate on bell peppers. Systemic activity of the acephate compensated, at least partially, for poor spray distribution with the conventional boom application. Virtually no injury occurred to the snap beans even in artificially infested, untreated plots. Total mortality caused by glandular trichomes was observed when larvae were introduced onto snap bean plants in the laboratory.

Effect of Water Soluble Polymers on Spray Droplet Size

ABSTRACT THE effects of polymer type and concentration, nozzle orientation, nozzle core size, and liquid shear on the size distribution of spray droplets produced in a high speed airstream for mixtures of water, Triton X-100 surfactant, and polymer product were analyzed with a laser particle measurement system. The effect of polymer concentration on droplet size was found to be dependent on polymer type. Polyvinyl and polyacrylamide polymers were found to be more effective than linear alkyl epoxide or polymide copolymers in increasing volume median diameter and reducing the percentage of spray volume composed of small droplets subject to spray drift. Shearing the polymer spray mixtures by multiple passes through a gear pump reduced both liquid viscosity and the size of spray droplets produced by disc-core nozzles in a 190 km/h airstream

Factors Affecting Size Distribution of Vegetable Oil Spray Droplets

ABSTRACT DROPLET size measurements were made to obtain definitive information on the effects of several factors on the size distribution of cottonseed and soybean oil spray droplets produced by fan nozzles under simulated aerial application conditions. Results indicated that the droplet size distribution is affected by airspeed, nozzle orientation and the physical characteristics of the oil. Visual observation of the fan nozzles spraying cottonseed and soybean oil in an airstream revealed that the droplet formation process for the oil differs greatly from that for water-based spray..

THE DISTRIBUTION AND RECOVERY OF AERIAL ULTRA‐LOW VOLUME SPRAYS FOR CONTROLLING NYMPHS OF THE AUSTRALIAN PLAGUE LOCUST, CHORTOICETES TERMINIFERA WALKER

AbstractField trials were conducted to determine the effect of a number of factors on the distribution and recovery of ULV spray droplets, emitted from a light aircraft equipped with Micronair rotary cage atomisers for the control of Australian plague locust nymphs [Chortoieetes terminifera (Walker)]. Spray deposits were sampled with small oil‐sensitive papers attached to pasture vegetation, and were analysed with a Quantimet 720 Image Analyser for droplet number and volume densities.Results indicated that volume recovery was 6 times higher in a strong (3–5 m/s) than in a light (< 1 m/s) wind, and about 3 times higher with a 50° Micronair blade angle and thus a relatively coarse droplet spectrum (volume median diameter ca 120 μm) than with a 25c setting (ca 70 μm). Aircraft flying height (either 3 or 10 m) had little influence on average recovery, though the greater altitude gave a slightly more uniform spray distribution.Subsequent trials applying fenitrothion 128% w/v at 0.3 L/ha against C. terminifera nymphal infestations confirmed the effectiveness of spraying in a strong wind using the 50° blade setting; nearly 100% mortality was recorded and treated areas were cleared of nymphal bands in 2 d. Control was unsatisfactory in the light wind trial, despite a higher applied dosage of 0.38 L/ha.

Spray Particle Size Distribution in Greenhouse ULV Applications to Poinsettia12

Spray particle size distribution was studied in dense poinsettia foliage after mechanical aerosol (or ULV) applications of mineral oil resmethrin formulations for control of greenhouse whitefly, Trialeurodes vaporariorum (Westwood), in a commercial greenhouse. A systematic arrangement of Teflon®-coated microscope slide sampling units was used to monitor both spray droplet distribution in horizontal and vertical directions in the foliage and particle size deposition on upper and lower leaf surfaces at each sampling position. Seven distinct application types, consisting of 2 avg particle size ranges (10–13 and 30–40 μ m mass median diam (MMD)) and 4 application techniques in different comhinations, were tested in a total of 19 spray tests. Microscope slide analysis provided MMD and avg deposition volume per unit of slide area data. Statistical analyses of these data indicated that 15–25 μ m MMD was the optimum spray particle size for greenhouse whitefly control and that application technique was an important factor. Spraying techniques that maximize the amount of air circulation within the foliage during application were most efficient.