Airblast Sprayer Research Articles

Spinosad application in an apple orchard affects both the abundance of the spider Araneus diadematus and its web construction behaviour.

The principles of organic production are based on the respect of ecological processes including the promotion of natural enemies to control pests. However, as a last resort, some natural pesticides can be applied such as the pesticide spinosad. This neurotoxic insecticide is now widely used even in non-organic production systems. As generalist predators, spiders, and especially orb web spiders, which prey on flying pests, are thought to be useful for biocontrol. To study the effects of spinosad on orb web spiders, we applied spinosad (Success4®) at the normal application rate (96 g ha-1) in an orchard covered by nets where Araneus diadematus was very abundant. Its abundance (number of webs), location when present on the web and web characteristics were determined one day before (D - 1) and 1, 3, 6, 10 and 14 days after the application (D + 1, D + 3, D + 6, D + 10 and D + 14). After spinosad application, at D + 1 and D + 14, the number of A. diadematus webs decreased by 28% and 47%, respectively, compared to D - 1 where we observed on average 0.2 webs m-2. This decrease is likely due to a combination of direct pesticide effects, reduced prey availability and mechanical effects of the air blast sprayer. The short-term toxicity of spinosad was assessed using behavioural markers: (i) the percentage of abnormally located spiders (i.e. neither in the centre of the web nor hidden under the apple leaves) for 30 and 50% of the webs at D + 1 and D + 3 respectively, (ii) the percentage of incomplete webs (made only of the non-sticky spiral) in 35 and 75% of the cases at D + 1 and D + 3 respectively and (iii) one web characteristic, the mean parallelism between spirals, that was significantly reduced at D + 1 compared to D - 1. The study of the other web characteristics indicated that spiders did not modify the capture area but rather significantly decreased their investment in silk at D + 6 and D + 10 by reducing the number of radii and spiral turns. Overall, the application of spinosad (Success4®), representing a triple disturbance (mechanical, toxicological and alimentary), has a negative impact on the orb web spider A. diadematus and should thus be used with caution if growers want to promote the contribution of these spiders to natural biocontrol in their fields.

Numerical Investigation on the Thermodynamic Characteristics of a Liquid Film upon Spray Cooling Using an Air-Blast Atomization Nozzle.

This paper developed a three-dimensional model to simulate the process of atomization and liquid film formation during the air-blast spray cooling technological process. The model was solved using the discrete phase model method. Several factors including the thermodynamic characteristics of the liquid film as well as the spray quality with different spray mass flow rates under different spray heights were numerically investigated and discussed. The results show that the varied spray height has little effect on the Sauter Mean Diameter (d32) of the spray droplet, while the thermodynamic characteristics of liquid film including the liquid film height, the liquid film velocity, and the liquid film generation rate are sensitive to the change of the spray height. With the growth of spray mass flow rates, d32, the liquid film generation rate and liquid film height become larger, while the liquid film velocity with different spray mass flow rates has a similar velocity distribution, indicating that the spray mass flow rate has little effect on the liquid film velocity. The average d32 of droplet size shows a sharp drop when sprayed from the nozzle in a short period of time (<1.5 ms), then approaching smoothness, below a value of 40 , the spray status tends to be stable.

Comparison of within canopy deposition for a solid set canopy delivery system (SSCDS) and an axial–fan airblast sprayer in a vineyard

Solid set canopy delivery systems (SSCDS) are novel ways of pesticide spray applications in modern high–density orchards and vineyards. Through our prior efforts, SSCDS variants have been tested and adjusted to provide optimal system configurations for spray application in high–density apple orchards and vineyards. This present study compared two prior optimized variants of an SSCDS comprising treatments with 1–tier and 2–tier of emitters/nozzles and an axial–fan airblast sprayer for spray performance in a modified vertical shoot position (VSP) vineyard. Such vineyards have the vine canes constricted under trellis wires, with the top of canes being loose and more sprawling. SSCDS 1–tier had a pair of full–circle emitters installed per vine at 76 cm above the cordon. For SSCDS 2–tier, two hollow–cone nozzles were installed per vine near the drip line at 45 cm above ground level in combination with additional emitters as in 1–tier. The sprayate was a fluorescent tracer dissolved in water at 500 ppm. Spray deposition and coverage were quantified in different canopy zones and on either side of leaf surfaces using mylar cards and water sensitive papers (WSPs) as samplers, respectively. The samplers were respectively analyzed using fluorometry and image processing techniques. Analysis of deposition data indicated statistically similar mean deposition for different treatments, however, uniformity of distribution was higher for the airblast sprayer treatment. Similar and uniform deposition on the mylar cards on the adaxial and abaxial leaf surfaces was observed in all the treatments, indicating that emitters/nozzles placed within a canopy can deposit similar amounts of active ingredient as an airblast sprayer. Contrary to the deposition data, spray coverage was highest for the airblast sprayer (33.5 ± 2.8%) followed by SSCDS 1–tier (21.5 ± 2.9%) and 2–tier (19.9 ± 3.0%). Such differences could be because of the use of air-assist which was absent in SSCDS based application. In summary, SSCDS provided higher canopy deposition, however, the airblast sprayer provided higher spray coverage and better spray application uniformity. Prior biological efficacy studies in apple orchards have reported equivalent insect-pest control for SSCDS and airblast sprayer, notwithstanding the uniformity and heterogenous spray coverage. Therefore, future studies are warranted to collect season long pest management data in economically viable plot sizes in a vineyard.

Determination of spray drift and buffer zones in 3D crops using the ISO standard and new LiDAR methodologies

Spray drift generated in the application of plant protection products in tree crops (3D crops) is a major source of environmental contamination, with repercussions for human health and the environment. Spray drift contamination acquires greater relevance in the EU Southern Zone due to the crops structure and the weather conditions. Hence, there is a need to evaluate spray drift when treating the most representative 3D crops in this area. For this purpose, 4 spray drift tests, measuring airborne and sedimenting spray drift in accordance with ISO 22866:2005, were carried out for 4 different crops (peach, citrus, apple and grape) in orchards of the EU Southern Zone, using an air-blast sprayer equipped with standard (STN) and spray drift reduction (DRN) nozzle types. A further 3 tests were carried out to test a new methodology for the evaluation of spray drift in real field conditions using a LiDAR system, in which the spray drift generated by different sprayer and nozzle types was contrasted. The airborne spray drift potential reduction (DPRV) values, obtained following the ISO 22866:2005, were higher than those for sedimenting spray drift potential reduction (DPRH) (63.82%–94.42% vs. 39.75%–69.28%, respectively). For each crop and nozzle type combination, a sedimenting spray drift model was also developed and used to determine buffer zone width. The highest buffer width reduction (STN vs DRN) was obtained in peach (˃75%), while in grape, citrus and apple only 50% was reached. These results can be used as the starting point to determine buffer zone width in the countries of the EU Southern Zone depending on different environmental threshold values. Tests carried out using LiDAR system demonstrated high capacity and efficiency of this system and this newly defined methodology, allowing sprayer and nozzle types in real field conditions to be differentiated and classified.

Simulation and experimental research on droplet flow characteristics and deposition in airflow field

In order to study the motion law of droplet flow under the airflow action of long-range air-blast sprayers, a CFD-based 3D model was established for the air-blast sprayer duct and its external airflow field, and the discrete phase model was introduced to simulate the motion of droplet flow in the airflow. The simulation data of the droplet flow trajectory, droplet flow parameters and droplet deposition were obtained by establishing the monitoring sections and bilateral coupling calculation in the airflow field. Results showed that gravity had an obvious effect on droplets and large droplets settled faster. Some of the larger droplets were formed by polymerization in droplets motion. The smaller droplets were transported further along with the airflow, and the long-range sprayer has a significant effect on the directional transport of small droplets. Besides, the spraying swath in the direction perpendicular to the range enlarged gradually with the increase of the spraying range. At the end of the range, the diffuse and drifting of the droplets were dominant. Given that the outlet airflow velocity of the sprayer duct was 25.01 m/s and the spray pressure 1.8 MPa, the maximum motion distances of aerosol, mist, fine mist and coarse mist in the airflow field were 18.5 m, 19.5 m, 17.5 m and 10.5 m, respectively. Droplet size and number as well as number density and volume density of droplet flow on all monitoring sections showed a regression function with changes in the distance of the spraying range. The simulation results of the model adopted in this paper were verified by Chi-square test between the simulation results of the droplet deposition and the spray measurement results. Research results provide a new method for the study of orchard air-blast spraying technology and references for the optimization of spraying technology. Keywords: droplet flow, droplet density, air-blast sprayer, computational fluid dynamics, droplet deposition DOI: 10.25165/j.ijabe.20201306.5455 Citation: Xiahou B, Sun D Z, Song S R, Xue X Y, Dai Q F. Simulation and experimental research on droplet flow characteristics and deposition in airflow field. Int J Agric & Biol Eng, 2020; 13(6): 16–24.

Smart Spray Analytical System for Orchard Sprayer Calibration: A-Proof-of-Concept and Preliminary Results

Abstract. Efficient chemical spray applications are vital to reduce off-target drift, economic losses to tree fruit growers, and negative environmental impacts. It is thus important to adequately calibrate and adjust orchard sprayers for intended applications. This technical note describes the design, prototyping, and field evaluation of a sensor-based smart spray analytical system (SSAS). The SSAS is equipped with units for spray capturing and volumetric quantification, air-assist velocity measurement, system actuation and control, and data acquisition and wireless transmission. The spray liquid and air-assist velocity quantification units are assembled on a custom-made mobile frame for vertical stop-and-go movement to provide measurements at eight distinct sampling heights above ground level. The data acquisition and transmission units autonomously log the data on-board and transmit wirelessly to a receiving computer with time and height stamps for real-time graphical visualization. All these autonomous processes are guided by a custom programmable single-board computer. The SSAS was preliminarily evaluated for spray liquid and air-assist velocity pattern assessment of an air-assisted orchard sprayer in four sets of spray trials. An average spray liquid recovery of 14.03% and pertinent coefficient of variation (CV) of 10.73% were observed. An average CV of 11.93% was observed in the air-assist velocity patterns. Overall, the SSAS provided measurements within acceptable ranges of variation. This system can thus minimize the experimental errors, time, and efforts involved in conventional assessments of sprayer attributes, thereby providing a reliable solution for orchard sprayer calibration and adjustment. Keywords: Air-assist velocity pattern, Airblast sprayer calibration, Data storage and transmission, Graphical visualization, Smart spray analytical system, Spray liquid pattern.

CitrusVol Validation for the Adjustment of Spray Volume in Treatments against Tetranychus urticae in Clementines

The optimization of the water volume used to apply pesticides with airblast sprayers is key to reducing water footprint, costs, operational time and drift of pesticides. This study evaluated a new tool (CitrusVol) that adjusts the spray volume to the characteristics of the vegetation and the pesticide used to control the two-spotted spider mite Tetranychus urticae in clementine trees. This mite is one of the main citrus pests because it damages fruit before harvest. For this aim, a total of 20 applications against T. urticae were evaluated during two consecutive years in seven commercial orchards. In these orchards, we evaluated: (i) the distribution of the spray in tree canopies, (ii) pest density before and after the treatment, and (iii) fruit damage at harvest when conventional volumes and volumes adjusted with CitrusVol were applied. On average, CitrusVol reduced 36% the water volume used to control T. urticae in the 20 applications. This reduction in the spray volume involved a decrease in the coverage in some parts of the canopy. However, T. urticae density and fruit damage at harvest were similar in trees treated with the adjusted volume calculated with CitrusVol and the volume used by the owners of the orchard. Therefore, the spray volume recommended by CitrusVol is adequate to control T. urticae in clementines.

Canopy spray deposition and related mortality impacts of commonly used insecticides on Drosophila suzukii Matsumura (Diptera: Drosophilidae) populations in blueberry.

Insecticide applications in blueberry production systems play a crucial role in the control of Drosophila suzukii populations. Here, quantitative spray deposition patterns were obtained under replicated field experiments in blueberry during two field seasons with three sprayers, i.e. cannon, electrostatic, and air-blast. Seven insecticides were tested (at 6 hours using a Potter spray tower) to determine the mortality data for adult D. suzukii. Spray deposition and mortality data for adult D. suzukii were used to create model simulations for insect populations. Model simulations included field deposition rates of sprayers and insecticide mortality as factors. Simulations were applied in different combinations with five applications over a 6-week period. Relative deposition rates for the cannon sprayer were elevated in the upper zones of the canopy, whereas for the air-blast sprayer, deposition was greater in the bottom zones. Electrostatic spray deposition was relatively uniform within the six canopy zones. Clear trends in D. suzukii laboratory mortality were found with lowest to highest mortality recorded for phosmet, spinetoram, spinosad, malathion, cyantraniliprole, zeta-cypermethrin, and methomyl respectively. Maximum D. suzukii population impacts, as shown by model outputs, were observed with air-blast sprayers together with zeta-cypermethrin. The electrostatic sprayer had the least variable canopy deposition among the three types of spray equipment, and the air-blast sprayer had the highest overall deposition rates. This study provides new hypotheses that can be used for field verification with these spray technologies and insecticides as key factors. © 2019 Society of Chemical Industry.

Residual Effects of Insecticides on Deraeocoris brevis (Hemiptera: Miridae)

Deraeocoris brevis (Uhler) is a key predatory natural enemy of insects and mites in pear orchards in the United States. Insecticides used for crop protection in pear orchards and their residues can negatively affect populations of D. brevis. The focus of this study was to investigate the field-aged residual effects of lambda-cyhalothrin, spinetoram, and chlorantraniliprole insecticides on D. brevis through contact exposure. An airblast sprayer was used to apply the high label rate of insecticides on pear trees. Leaves were collected from the experimental trees at 1 d after treatment (DAT) and then at 7-d intervals up to 21 DAT. Adults and nymphs were exposed to leaves with insecticide residues or untreated control for 72 h in the laboratory. The nymphs that survived the treatments were reared until they emerged as adults. The surviving paired adults were reared until death. The treated nymphs were assessed for acute mortality, survival, developmental time, and the sex ratio if they emerged as adults. The treated adults were assessed for acute and chronic mortality, fecundity, fertility, and longevity. Both nymphs and adults exposed to leaf residues of lambda-cyhalothrin had significantly higher acute mortality compared with the insects exposed to the control. When compared with the control treatment, the toxicity of field-aged residues of lambda-cyhalothrin, chlorantraniliprole, and spinetoram can persist over a longer period of time. Similar patterns were observed in previous laboratory and field experiments on D. brevis. We discuss the residual effects of three insecticides through contact exposure of D. brevis.

Spray Drift from Three Airblast Sprayer Technologies in a Modern Orchard Work Environment.

Pesticide spray drift represents an important exposure pathway that may cause illness among orchard workers. To strike a balance between improving spray coverage and reducing drift, new sprayer technologies are being marketed for use in modern tree canopies to replace conventional axial fan airblast (AFA) sprayers that have been used widely since the 1950s. We designed a series of spray trials that used mixed-effects modeling to compare tracer-based drift volume levels for old and new sprayer technologies in an orchard work environment. Building on a smaller study of 6 trials (168 tree rows) that collected polyester line drift samples (n = 270 measurements) suspended on 15 vertical masts downwind of an AFA sprayer application, this study included 9 additional comparison trials (252 tree rows; n = 405 measurements) for 2 airblast tower sprayers: the directed air tower (DAT) and the multi-headed fan tower (MFT). Field-based measurements at mid (26 m) and far (52 m) distances showed that the DAT and MFT sprayers had 4-15 and 35-37% less drift than the AFA. After controlling for downwind distance, sampling height, and wind speed, model results indicated that the MFT [-35%; 95% confidence interval (CI): -22 and -49%; P < 0.001] significantly reduced drift levels compared to the AFA, but the DAT did not (-7%; 95% CI: -19 and 6%; P = 0.29). Tower sprayers appear to be a promising means by which to decrease drift levels through shorter nozzle-to-tree canopy distances and more horizontally directed aerosols that escape the tree canopy to a lesser extent. Substitution of these new technologies for AFA sprayers is likely to reduce the frequency and magnitude of pesticide drift exposures and associated illnesses. These findings, especially for the MFT, may fit United States Environmental Protection Agency's Drift Reduction Technology (DRT) one-star rating of 25-50% reduction. An 'AFA buyback' incentive program could be developed to stimulate wider adoption of new drift-reducing spray technologies. However, improved sprayer technologies alone do not eliminate drift. Applicator training, including proper sprayer calibration and maintenance, and application exclusion zones (AEZs) can also contribute to minimizing the risks of drift exposure. With regard to testing DRTs and establishing AEZs, our study findings demonstrate the need to define the impact of airblast sprayer type, orchard architecture, sampling height, and wind speed.

Planar drop-sizing and liquid volume fraction measurements of airblast spray in cross-flow using SLIPI-based techniques

This paper presents planar measurements of Sauter mean diameter (SMD) and liquid volume fraction distributions of airblast spray injected into cross-flow. The experiments are conducted using a combination of structured laser illumination planar imaging with laser sheet drop-sizing (SLIPI-LSD) and particle/droplet imaging analysis (PDIA) techniques. Effect of gas to liquid mass ratio (GLR) and cross-flow velocity (Ucross) is studied. Planar SMD distribution at low GLR improved with increase in Ucross due to secondary atomization of large droplets. Uniform SMD distribution in a range of 10–20 µm is observed for GLR more than 3. The distribution of liquid volume fraction at low GLR condition shows poor dispersion with most of the liquid concentrated near the injector. The liquid volume fraction distribution improves with increase in GLR and better dispersion is observed for GLR more than 3 and two-phase momentum ratio (q2) greater than 13.06. Spatial bifurcation in liquid fraction is found for high GLR conditions. The SMD in the range of 10–20 µm and uniform distribution of liquid are observed for GLR more than 3 and q2 > 25.6.

Occupational Risk Factors for Health Disparities among Latina Farm Workers in Southern Idaho

TPS 792: Occupational health 2, Exhibition Hall, Ground floor, August 27, 2019, 3:00 PM - 4:30 PM Background/Aim: Latina farm workers may experience a unique intersection of social and environmental factors that are known to affect health. The disadvantages inherent in their gender, race and social class may be compounded by their immigration status, rural location and the hazards of farm work. We propose to identify the most critical risk factors for poor health facing this underserved and understudied population. Methods: Our study uses a mixed-methods approach that combines qualitative data from focus groups (n=3 groups of 10 participants each) and semi-structured interviews (n=15) with quantitative and qualitative survey data (n=100) and biological monitoring (n=45). The study includes six domains of inquiry: sociodemographics, food security and food access, housing conditions, social isolation, access to medical care and occupational hazards. Urinary biomonitoring is used to assess exposure to common agricultural pesticides. Results: All study participants identify as Latina or Hispanic and, among those recruited to date (n=25), range in ages from 25 to 71 and report an average of 12 years working in agriculture. While sample and data collection is in progress, preliminary analysis indicate that these participants spend an average of 7.5 months per year employed in agricultural work. Participants report working with a range of crops common in Southern Idaho, including onions, sugarbeets, peas, corn, grapes, and hops. More than 25% of the study participants report that their employers do not provide water, cups and hand washing facilities on a daily basis. Participants report use of backpack and air blast sprayers, and approximately one-third report receiving training from their employers on the use of pesticides. Conclusions: This research will assess the prevalence of social and environmental risk factors among Latina farm workers using an interdisciplinary approach that combines surveys, in-depth interviews and focus groups, biological monitoring and field observations.

Evaluation of droplets size distribution and velocity pattern using Computational Fluid Dynamics modelling

Synchronizing airflow output in air atomized spray to achieve effective spraying and minimal crop damage is a big challenge in controlled cultivation. The environmental conditions inside these structures presents several limitations in spray application including limited sprayer-target distance. A Computational Fluid Dynamics (CFD) modeling of droplet sizes and droplets velocity was developed and applied to evaluate the distribution pattern of spray and spraying effectiveness at varied sprayer settings for a new model greenhouse air blast sprayer. The evaluated sprayer settings were: three horizontal distances from the nozzle (0.3, 0.5 and 0.7 m), two nozzle discharge rates (0.40 and 0.65 l min−1) and two ground speeds (0 and 0.36 m s−1). The airflow velocity at the nozzle outlet was maintained at 24.3 m s−1. Particles were tracked according to the Lagrangian approach taking into account the spray atomization. To complement the simulation, droplet sizes were determined using the Malvern Mastersizer 2000. The model predicted droplet sizes considerably well with a root mean square error, ERMS of 8.29 μm. The results indicated that both distance and nozzle’s flow rate influenced droplets size distribution. At low flow rate, the spray corresponded to a finer droplet size spectrum compared to at higher flow rate. The motion of the sprayer significantly affected the trajectories of the droplets hence their spatial location.

Season Long Pest Management Efficacy and Spray Characteristics of a Solid Set Canopy Delivery System in High Density Apples.

Solid set canopy delivery systems (SSCDS) are a novel foliar agrochemical delivery system designed as an alternative for airblast sprayers in high density fruit production. This study tested the pest management potential, coverage, and chemical deposition of an SSCDS using commercially available microsprinkler components over the course of a growing season. Spray coverage and deposition for a representative airblast sprayer and SSCDS were evaluated using water sensitive paper and tartrazine dye, respectively. Foliar sprays for pest suppression were applied through both systems, and damage assessments were taken at the midpoint and end of the growing season. SSCDS sprays demonstrated similar levels of coverage on the adaxial leaf surface as airblast sprays, but significantly lower coverage on the abaxial surface. However, mean levels of foliar chemical deposition was generally higher in the SSCDS. Evaluations found minimal arthropod and fungal damage in both airblast and SSCDS treated plots compared to untreated trees. The SSCDS was shown to be a viable alternative to the airblast, with inherent advantages such as rapid application time and improved worker safety. Furthermore, higher deposition on SSCDS treated foliage supports the hypothesis that SSCDS provide a higher droplet capture rate in the canopy, with less off-target loss and drift than airblast sprayers.

Field-Aged Insecticide Residues on Chrysoperla johnsoni (Neuroptera: Chrysopidae).

We studied the direct (lethal) and indirect (sublethal) effects of field-aged insecticide residues of spinetoram, chlorantraniliprole and lambda-cyhalothrin on adults and larvae of the green lacewing, Chrysoperla johnsoni Henry, Wells and Pupedis an important generalist predator in western United States pear orchards. We applied formulated pesticides using their high label rates mixed with 935 liters/ha of water on pear trees utilizing an airblast sprayer. We collected leaves from the experiment trees at 1, 7, 14, 21 days after treatment (DAT) and exposed C. johnsoni adults and second instars to insecticide residues or untreated control for 72 h. We monitored larvae that survived the treatments until adult emergence (for larvae) or adults until death (for paired adults). We assessed the adults for acute and chronic mortality, longevity, fecundity, and fertility, and larvae for acute mortality, sex ratio, developmental time, and survival of adults emerged from treated second instars, to determine lethal and sublethal effects. The field-exposed insecticide residues of chlorantraniliprole exhibited higher lethal and sublethal toxicities on C. johnsoni during the 21-d leaf collection period when compared with the field-exposed residue toxicities of lambda-cyhalothrin and spinetoram. The field-exposed residue of lambda-cyhalothrin and spinetoram exhibited moderate toxicities on C. johnsoni during the 21-d leaf collection period. Results from this study show similar trends with previous studies using multiple routes of exposure laboratory assays and field experiments on Chrysoperla sp. The direct and indirect effects of field-aged residues of spinetoram, chlorantraniliprole, and lambda-cyhalothrin on C. johnsoni are discussed.

Spray coverage and pest management efficacy of a solid set canopy delivery system in high density apples.

Air blast sprayers are not optimized for spraying the short statured trees in modern apple orchards, resulting in off target drift and variable coverage. A solid set canopy delivery system (SSCDS) consisting of a microsprayer array distributed throughout the orchard was investigated as a replacement agrochemical application method in this study. SSCDS's have the potential to optimize coverage, rapidly spray applications, and remove the operator and tractor from the orchard. Air blast and SSCDS applications were compared using water sensitive paper, bioassays, and pest damage assessments. Pest management and coverage were compared using application volumes of 700 and 795 L ha-1 , respectively. In 2013, adaxial coverage measurements showed no difference between the treatments, but air blast sprayers had higher coverage levels on the abaxial surfaces. There were no significant differences in coverage in 2014. Bioassays using Choristoneura rosaceana fed on leaf discs treated by the SSCDS displayed 95.8% mortality in 2013 and 94.2% mortality in 2014, and air blast treated larval mortality was 95% in 2013 and 100% in 2014. Damage evaluations in both years generally showed no significant differences between the air blast plots and the SSCDS plots, but significant differences between the treated plots and untreated control. The prototype SSCDS was an effective pest management tool in high density apples, and offered a number of advantages over an air blast. Further engineering and research into coverage optimization would offer producers a novel tool for foliar agrochemical applications. © 2019 Society of Chemical Industry.

Experimental studies on structure of airblast spray in crossflow

The present investigation is focused on experimental studies on the structure of airblast spray in crossflow. Atomizer is at a higher pressure than ambient and the airblast gas is expected to exhibit features generally found in under-expanded gas jets. High-speed images are captured using shadowgraphy technique. Certain wave-like structures observed in the near-nozzle region are attributed to shock–vortex interactions, generally observed in under-expanded gas jets. Proper Orthogonal Decomposition (POD) analysis has been carried out using these images. POD mode shapes clearly show signatures of shock–vortex oscillations and frequencies close to the screeching frequency observed in under-expanded jets. The POD modes are compared for different conditions and the significance of dynamic structures and their temporal behavior is discussed. Finally, a regime map is also proposed to characterize spray behavior in crossflow.

Survey Reveals Training Needs for Airblast Sprayer Applicators, Farm Managers, Owners and Pest Control Advisers

Survey Reveals Training Needs for Airblast Sprayer Applicators, Farm Managers, Owners and Pest Control Advisers

Toward a new method to classify the airblast sprayers according to their potential drift reduction: comparison of direct and new indirect measurement methods.

Drift is one of the most important issues to consider for realising sustainable pesticide sprays. This study proposes an alternative indirect methodology for comparative measurements of drift reduction potential (DRP) generated by airblast sprayers, aimed at overcoming the practical inconveniences and drawbacks of standardized ISO 22866:2005. A test bench in the absence of target crop and wind was employed to measure drift potential values (DPVs). A variation to the proposed method that introduced a crop between sprayer and test bench device was considered to study the canopy effect (absence/presence) and to validate the method. In parallel, direct spray drift measurements (ISO 22866) were performed to obtain the drift value (DV). A representative vineyard airblast sprayer was evaluated in four configurations (a combination of two fan airflow rates and two nozzle types). The configurations tested under the three methods (direct and indirects) were classified according to achieved drift reduction percentages (ISO 22369-1:2013) and compared. Indirect methods discriminated DPVs from different nozzles (conventional, air induction) and fan airflow rate (high, low) combinations. Indirect methods also showed that despite crop influence on drift amount, target absence has a negligible effect when used specifically for DRP determination/classification. In fact, identical DRP final classifications were achieved for the two methodologies tested. Alternatively, all tested configurations resulted in lower DR values following the ISO 22866 field method, which caused different final classifications due to the high dependence of results on external factors. The alternative test bench methodology, characterized by the absence of target crop and calm of wind, was considered feasible for comparative measurements of airblast sprayer DRP. © 2019 Society of Chemical Industry.

Planar liquid volume fraction and SMD distribution of Jatropha vegetable oil spray: effect of ethanol blending and GLR

This research paper presents the planar distribution of Sauter Mean Diameter (SMD) and liquid volume fraction in airblast sprays of Jatropha vegetable oil. The effect of ethanol blending at different gas to liquid mass ratios (GLRs) is presented. The planar SMD distributions are obtained using Structured Laser Illumination and Planar Imaging-Laser Sheet Drop sizing (SLIPI-LSD) and Particle/droplet Imaging Analysis (PDIA) techniques. The straight vegetable oil (SVO) spray showed poor atomization at GLR 1, which rose with increasing GLR. The blending of ethanol significantly improved the atomization of SVO even at GLR 1 condition. The liquid volume fraction distribution increased with higher GLR and with the increase in the percentage of ethanol in the blend. The impact of the increase in ethanol on drop size is small at GLR of 5. The E30 blend showed uniformly distributed liquid in the spray plane with uniform SMD distribution in the range of 50 \(\upmu \)m at GLR 5.