Charged Spray Research Articles

Evaluation of the Potential Pesticide Reduction of Three Electrostatic Spray Charge Systems for Orchard Applications Aligned with the European Farm to Fork Strategy

Evaluation of the Potential Pesticide Reduction of Three Electrostatic Spray Charge Systems for Orchard Applications Aligned with the European Farm to Fork Strategy

Electrostatically charged COVID-19 disinfectant spray coverage on a cylinder

Electrostatically charged COVID-19 disinfectant spray coverage on a cylinder

Estimating droplet charge in numerical simulations of charged sprays

A novel method for estimating droplet charge in numerical simulations of conductively and inductively charged sprays is presented. This method is based on balancing the effective electric field at the sprayer nozzle with the global electric field induced by the charged droplets. The global approach avoids the need for computationally expensive local resolution of the spray formation region, allowing it to be used in Eulerian–Lagrangian simulations of high-flowrate sprays. The method is validated against experimental data from literature, proving it can predict droplet charge with reasonable engineering accuracy, over a wide range of spray parameters, for conductive spray liquids.

Cavitation between cylinder-liner and piston-ring in a new designed optical IC engine

A new engine block with optical access has been designed and manufactured capable of running up to 3000 r/min with the same specification as the unmodified engine. The optical window allowed access to the full length of the liner over a width of 25 mm to investigate the lubricant flow and cavitation at contact point between the rings and cylinder-liner. In addition, it allowed good access into the combustion chamber to allow charged flow, spray and combustion visualisation and measurements using different optical methods. New custom engine management system with build in LabView allowed for the precise full control of the engine. The design of the new optical engine was a great success in producing high quality images of lubricant flow, cavitation formation and development at contact point at different engine speeds ranging from 208 to 3000 r/min and lubricant temperatures (30°C–70°C) using a high-speed camera. The results under motorised operation confirmed that there was no cavitation at contact points during the intake/exhaust strokes due to low in-cylinder presure, while during compression/expansion strokes, with high in-cylinder pressure, considerable cavities were observed, in particular, during the compression stroke. Lubricant temperatures had the effect of promoting cavities both in their intensity and covered ring area up to 50°C as expected. Beyond that, although the cavitation intensity increases further with temperature, its area reduces due to possible collapse of the cavitating bubbles at higher temperature. The change of engine speed from 208 to 800 r/min increased cavitating area considerably by 52% of the ring area and was further increased by 19% at 1000 r/min. After that, the results showed very small increase in cavitation area (1.3% at 2000 r/min) with similar intensity and distribution across the ring.

Quantification of particle separation using electrostatically charged spray mist in a dust chamber

In order to improve the efficiency of reducing fine dust emissions from diffuse sources, the commonly used water mist can be electrostatically charged. Thus, the attraction between particles and droplets increases due to electrostatic field forces. In the experimental investigations carried out, an electrostatic two-fluid nozzle was used to generate a charged spray mist according to the principle of charging by induction. In a chamber, dispersed dust was precipitated with the spray mist, while detecting the laser light attenuation. By means of comparative measurements it could be shown that faster sedimentation and separation takes place through electrostatic attraction. Parameter variations regarding the use of compressed air and water were investigated and the sedimentation time of the particle–droplet mixture in the chamber was shown. A size distribution was then calculated from the laser light attenuation, which shows that the proportion of small particles decreases with spray application. Furthermore, the influence of the polarity of droplets and solid particles on the reduction measure was determined.

AN INVESTIGATION OF ELECTROSTATIC CHARGE EFFECTS WITH A COVID-19 DISINFECTANT SPRAY TO COVER A VERTICAL CYLINDER

Surface disinfecting has become a necessity in the global effort to control the COVID-19 pandemic, and the application of disinfectant liquid to completely and uniformly cover target objects is a common goal. Spraying of these materials offers a clearly beneficial solution where the liquid is atomized into droplets that are distributed on the target surface. However, while surfaces in the direct line-of-sight may receive adequate coverage, hidden surfaces on the sides and back of an object may be shielded and receive limited or no coating. Electrostatically charged sprays have received added attention and use because, in concept, a charged droplet may be more likely to not only land on a surface through direct impingement, but also be drawn further toward hidden surfaces due to attractive charge forces. Therefore, electrostatically charged sprayers provide a uniquely beneficial method to distribute disinfectant materials, although the actual effects have received limited scientific analysis. In the present study, a commercially available electrostatic sprayer has been investigated with electrostatic spray charge off and on in order to evaluate the resulting coating completeness, uniformity, and efficiency. Detailed measurements of the spray characteristics, such as drop size, velocity, and concentration, both upstream and downstream of the target object, offer explanations for differences in the resulting coverage. While this investigation is not comprehensive, it serves to offer insight into the potential benefits of electrostatically charged disinfecting sprays as well as explanations into how those improvements are achieved. Using the present sprayer, disinfectant material, and target object, coverage was improved by 40% using charged droplets, primarily due to increased coverage on the downstream (back) side of the target cylinder, which saw zero coverage without charged droplets. Through detailed analysis, this improvement is attributed to alterations in the velocity field of the droplets just downstream of the cylinder where the charged droplets are more susceptible to following the recirculating turbulence of the entrained air flow.

Atomization behaviour of a hybrid air-blast-electrostatic atomizer for spray combustion

An analysis of the atomization region of a series of diesel sprays generated from a hybrid (air-blast & electrostatic) atomizer is presented. The atomizer has been specifically designed to operate on single or hybrid mode to enable the delivery of a charged and/or air-assisted spray for combustion applications. High speed microscopic backlit imaging is applied over a range of operating conditions. A noticeable influence of charge on the measured droplet and ligament size and their numbers is observed at all the tested aerodynamic Weber numbers (We = 2.4, 5.2, 8.2, 11.2). The experimental results reveal that an increase in spray specific charge can reduce both droplet and ligament sizes while a significant increase in droplet count is noted. The influence of charge is found to vary depending on the aerodynamic Weber number, with a more noticeable influence on the atomization behaviour for the lowest Weber number case (We = 2.4). When operating in a hybrid mode, a minimum spray specific charge (0.14C/m3) is required for the applied electric potential to influence the aerodynamically assisted spray.

Experimental investigation on a novel agglomeration device based on charged ultrasonic spray and vortex generators for improving the removal of fine particles

Multi-field synergistic agglomeration is a promising pretreatment technology for improving the control and removal of fine particles. In this work, a novel agglomerator coupling with plasma charged ultrasonic spray and turbulent vortex generator was put forward, which has three agglomeration modes, namely turbulent agglomeration, atomized turbulent agglomeration and charged atomized turbulent agglomeration. As a pretreatment device, the agglomerator was combined with a fabric filter for the experimental investigation. The result indicated that the agglomeration efficiencies of the PM1 for the three agglomeration modes were 21.8%, 53.2% and 68.9%, respectively; and the removal efficiencies of the PM1 for the only fabric filter and the fabric filter combined with the three agglomeration modes were 66.5%, 83.9%, 86.8% and 89.7%, respectively. The characteristic experiment of the designed electrode showed that the stable voltage was about 19–38 kV and the charge-to-mass ratio was in the range of 1–5 mC kg−1. The optimization study of the two important parameters showed that the atomization quantity was recommended in the range of 1.6–2.7 kg∙h−1 and the inlet flue gas velocity should be as small as possible and close to 4.8 m/s to ensure the agglomeration effect.

Evaluating capacitive wetness sensors for measuring deposition in electrostatically charged spraying operations

Standard methods for measuring pesticide deposition include water sensitive paper and fibre (paper or cord) collectors, which require time consuming manual steps to gather, process and interpret results. Measurement of pesticide deposition is important in evaluating the efficacy of a spray, which affects the total crop yield. A lack of knowledge about spray quality often results in the need to spray to excess, which can contaminate the soil and damage neighbouring ecosystems and the atmosphere. The suitability of PHYTOS 31 capacitive leaf wetness sensors (Meter Group, Pullman, WA, USA) for spray sensing applications was analysed. The best fit calibration function for droplets of ~ 1 μL volume was linear (R2 = 0.985). The best fit calibration function for drops > 10 μL was a weighted sum of a linear and power function (R2 = 0.984). Thus, the calibration function should be chosen according to the anticipated size of droplet. The PHYTOS 31 sensors and water sensitive papers were used in a field test, comparing electrostatically charged and uncharged sprays. Both measurement techniques show that charged spray is more effective in covering parts of the plants which do not have a direct line of sight to the nozzle. The techniques disagree on quantitative coverage measurement, with the water sensitive papers reporting areal coverage two to four times higher than the capacitive sensors. High-speed video observations show that this is due to contraction (de-wetting) of the drop on the capacitive sensors. The surface of the capacitive sensors is more hydrophobic than the papers. The hydrophobicity of the capacitive sensors appears to be a better match to plant leaves than that of the papers. Capacitive sensors are a suitable measurement tool for evaluating liquid coverage in the field, but further calibration is necessary to be confident in the quantitative data.

Studies on chargeability parameters of charged spray droplets for chemical application in agriculture

The paper describes a method for charging spray droplets for pesticide application in agriculture. An induction based electrostatic charging system was developed with optimized parameter namely flow rate, electrode voltage and distance of electrode from nozzle tip. A high voltage charging module was fabricated to supply the voltage up to 10 kV. The experiments were conducted in division of agricultural engineering, IARI, New Delhi during 2017. A faraday cylinder test rig was used to optimize the flow rate, electrode voltage and distance of electrode from nozzle tip. The highest charge to mass of 1.543 mC/kg was obtained at a flow rate of 450 ml/min, applied voltage of 4.0 kV and electrode distance of 40 mm respectively. The results of CMR established the relationship between CMR and selected design parameters. The statistical analysis revealed that the individual effect of selected parameter had significant effect on CMR at 1% level of significance, whereas the interaction effect of voltage, flow rate and electrode position from nozzle tip had no significant effect on CMR.

Electrohydrodynamic spray applicator for homogenous application and reduced overspray of sunscreen.

The recommended amount of sunscreen by hand application (2mg/cm2 ) is in reality not achieved, which decreases the homogeneity and thereby the effective sun protection factor (SPF). The homogeneity of sunscreen applied by a newly developed spray applicator using an electrostatically charged aerosol, for which a hand rubbing of the formulation is not necessary, is evaluated. In vivo experiments were performed on the volar forearms of human volunteers using the spray applicator compared to the standardized hand application according to ISO 24444. The distribution homogeneity was assessed qualitatively using in vivo laser scanning microscopy and quantitatively by absorption spectroscopy after tape stripping and by the standard deviation of multiple spatially displaced reflectance measurements for non-invasive SPF determination below the minimal erythemal dose, which showed a significantly higher homogeneity by 20.9% after spray application compared to hand application. Non-invasive SPF determination of multiple spatially displaced reflectance measurements was proven to be a suitable method for the non-invasive determination of the sunscreen distribution homogeneity. Electrostatically charged spray application increased the sunscreen distribution homogeneity on the skin and can reduce the amount of overspray.

Numerical simulation of evaporating charged sprays in spray chilling

In this research we investigate whether charged sprays offer any improvements over conventional spray in the spray-chilling of meat. A Eulerian-Lagrangian CFD modelling approach is developed and validated with results from automotive spray painting. The model is then extended to include evaporation and the transport of evaporation products. The simulation results show doubling of the spray transfer efficiency as well as a notable increase in the rate of cooling when electric charge is applied to the spray. Furthermore, the presented modelling approach yields consistent results at low computational costs, making it suitable for use in future design optimisation studies.

Analysis of electrostatic solid lubricant spray process parameters during turning Ti-6Al-4V alloy

Titanium alloys are considered as hard-to-cut material due to its relatively high resistance to corrosion, low thermal conductivity and high chemical reactivity. Effective penetration of sufficient amount of lubricant in the metalworking process is of utmost importance to (a) reduce frictional resistance at the high-temperature tool–workpiece interface and (b) avert the formation of built-up edge in machining process. Traditionally, the lubricant forms a thin fluid film to reduce the friction. In order to reduce or eliminate coolant usage and to apply lubri-coolant efficiently at tool–chip–workpiece interface, a novel near-dry machining technique called electrostatic charged solid lubricant spray system has been developed. In electrostatic charged solid lubricant spray technique, the aerosolized micro-droplet particles were sprayed from the nozzle tip which uses a phenomenon called contact-charge electrification principle. The quick penetration and wettability of charged atomized droplet particles are impinged with high velocity at the tool–chip interface. The focus of the present experimental research is to analyse the optimum lubrication process parameters of the experimental set-up in terms of effectively applying cutting fluid in the machining zone. The study shows that the desired atomization and machining performance of the electrostatic charged solid lubricant spray technique can be obtained by governing different spray parameters (lubricant flow rate, air pressure, spray nozzle position, nozzle distance, electrostatic voltage). The results revealed that when the charged lubricants are applied with high velocity and large number of droplets, it will have significant influence on surface roughness and cutting force. The fabricated electrostatic charged solid lubricant spray technique provides us with an efficient and economic machining solution by applying solid lubricants effectively at tool–material interface during turning of Ti-6Al-4V alloy material. The present approach and the obtained results will help in better understanding of the machinability of hard-to-cut materials in manufacturing industries.

Electrostatic charging of water spray by induction

Results of experimental investigation of electric charging of water spray produced by several commercially available single-fluid pressure swirl atomizers, with cylinder induction electrode are presented in this paper. The process of induction charging of water spray is analysed in terms of specific charge and droplet size distribution, for water flow rate, water pressure, induction electrode voltage and inter-electrode distance as process variables. It was found that the specific charge of water droplets increases with increasing voltage applied to the induction electrode, but only to a certain voltage magnitude. The decrease in the specific charge for higher voltages is caused by corona discharge from the induction electrode and the shielding effect of space charge due to electric field produced by the charged droplets. The optimal inter-electrode distance maximizing the specific charge was determined for each of the tested nozzles.

Measurement of electric fields of charged spray clouds of conductive liquids in free space and in a conductive vessel

The process of spraying liquids generated electrical charges. The question therefore arises as to whether this electrostatic charge represent an ignition hazard when an explosive mixture is present. This hazard occurs when cleaning vessels, in which an explosive mixture is formed by residues of easily flammable liquids or the cleaning medium itself. Although measurement techniques and methods exist for detecting this electrostatic charging process, they have not been sufficiently scientifically proven. The Chilworth JCI 131 adverse conditions field meter is to be used to measure the electrostatic charging of sprayed liquids. It shall be validated by measuring the electric field strength of a flat spray water jet in low-pressure range (8 bar) charged by contact charging and accumulation of free electrons of a commercial, insulated arranged electrostatic spraying system (up to - 90 kV). A flat-jet nozzle is selected which atomizes the spray jet, which serves as the measuring surface, sufficiently large. This arrangement is further investigated in a 1 m3 stainless steel IBC. The investigations presented are part of a project aiming to extend the scope of the German Technical Rules for Hazardous Substances (TRGS) of TRGS 727, which regulate avoiding ignition hazards resulting from electrostatic charging. The aim is to reach an understanding that allows provisions for safe cleaning of “small” and “medium-sized” containers up to 50 m3. This project is funded by DGUV (German Social Accident Insurance) and partners from the industry.

Rapid Determination of Adenine Arabinoside Monophosphate in Pharmaceutical Injections by Droplet Spray Ionization – Tandem Mass Spectrometry (DSI-MS/MS)

Rapid analysis of pharmaceutical preparations is of great interest in clinical studies with benefits for identifying counterfeit drugs. In this study, droplet spray ionization tandem mass spectrometry (DSI-MS/MS) was developed for the rapid determination of adenine arabinoside monophosphate in pharmaceutical injections without complex sample pretreatment. The sample solution was loaded on the slip corner placed in front of the inlet of a mass spectrometer, and high voltage was applied to the solution to create a charged spray from the corner for MS analysis. The sample was loaded for analysis without additional sample preparation protocols, which greatly simplifies the operation. The limit of detection and limit of quantification were determined to be 2.7 and 9.1 ng/mL, respectively. The recoveries were in the range from 96% to 112%, and the calculated relative standard deviations were less than 7% for the DSI-MS/MS method. Three adenine arabinoside monophosphate pharmaceutical injection samples and a degraded sample obtained by acid treatment at 40 °C were successfully analyzed by directly dissolving and diluting the sample. Moreover, the sample-loading step required only 2 s. Together these capabilities indicate that the DSI-MS/MS is a simple and robust method and has promising applications in pharmacology studies without complicated sample pretreatment.

Experimental analysis of electrode parameter effect on spray charge

In this paper, the influence of the diameter of the annular electrode and the arrangement of the nozzle on the droplet in electrostatic spray was studied by experiment and analysis. On the conical spray nozzle, five different diameters of ring electrodes and five mounting positions were used to carry out the jet charged spray test. The net current method was used to measure the charged current, total mass and test time of the droplets. The charge to mass ratio was used to evaluate the inductive charge performance of the droplet. The test results show that the charge increases with the increase of the charge voltage on the electrode. When electrode ring diameter increases, the droplet charge decreases. While the installation position of the electrode moves forward along the direction of the spray, the charge of the droplet increases. There is a linear relationship between the charge and the electrode ring diameter and installation location.

Induction charging of water spray produced by pressure atomizer

Charged sprays are widely used in various branches of industry, for example, for surface coating or gas cleaning by wet electrostatic scrubbers. The selection of appropriate system for charged spray generation is of crucial importance for obtaining high cleaning efficiency of a scrubber. This paper presents comparative experimental studies of parameters of charged sprays produced by various types of pressure atomizers with charging of droplets by induction, using three types of induction electrodes. The spray systems were characterized in terms of droplet size distribution and specific electric charge carried by the generated droplets. The induction charging process was investigated experimentally for the following parameters: voltage of induction electrode, inter-electrode distance, supply water pressure. It was determined that nozzles of lower flow rate generate sprays of higher specific charge, because the Sauter Mean Diameter for these nozzles is smaller. It was also found that the specific charge of droplets increases with increasing voltage applied to the induction electrode, but only to a certain voltage magnitude. Above this voltage level, the specific charge decreases due mainly to the shielding effect of space charge of produced droplets and the corona discharge from induction electrode, which neutralizes the droplets' current. It was shown that the specific charge of droplets decreases with increasing Sauter Mean Diameter of those droplets.

Investigation of Optimum Applied Voltage, Liquid Flow Pressure, and Spraying Height for Pesticide Application by Induction Charging

Abstract. Superposition of charges to pesticide spray droplets by electrostatic induction principle plays an important role in plant protection. It influences spray droplets characteristics, deposition and wraparound effect on leaf surfaces. Hence, an adoption of optimum parameters combination will improve spraying effectiveness to reduce pesticide wastage and environmental pollution. This article investigated the effect of 0-12 kV applied voltages, 2-4 bar liquid flow pressures, and 20-60 cm spraying height regimes on spray chargeability, droplet sizes, spray swath, and droplets deposition while all other parameters were kept constant. The combined parameters of 12 kV applied voltage, 4 bar liquid flow pressure, and 60 cm spraying height produced maximum charged spray swath (1.98 m) and fine particulate droplet sizes (48.91 µm). However, applied voltage of 12 kV, liquid flow pressure of 4 bar at spraying height of 20 cm yielded maximum chargeability of -1.95×10-3 mC kg-1. Since spraying height influences the extent of pesticide spray coverage, a boom height of 60 cm is suitable for deposition in electrostatic pesticide application at 12 kV charging voltage and 4 bar liquid flow rate. The operation of combined optimum parameters took reference from a uniform plant height surface during spraying. Hitherto, the study would help farmers to select suitable electrostatic spraying parameters for pesticide application in plant protection. Keywords: Applied voltage, Charge-mass ratio, Droplet sizes, Liquid flow rate, Spray pressure, Spray swath.

Electrostatically charged aerial application improved spinosad deposition on early season cotton

Spinosad (Tracer™), produced by an actinomycete, Saccharopolyspora spinosa, was aerially applied on early season cotton at a spray rate of 9.35 L ha−1 with a bipolar electrostatic aerial spray system, charged on and off. The charge-to-mass ratio (Q/M) for spinosad was 0.7714 mC kg−1 at ±9.0 kV charging voltage. Electrostatically charged sprays significantly increased deposition on an artificial collector by 34.5% compared to uncharged sprays. Spray droplet spectra was significantly greater for the electrostatically charged application than that for the uncharged application. This study can provide guidance to aerial applicators for increasing spray deposits on early season cotton.