Spray Field Research Articles

Effects of air swirler geometry on air and spray droplet interactions in a spray chamber

In this work, interactions between cold spray and swirl airflow are characterized experimentally and numerically for various air swirler geometries. The number of vanes, vane angle, vane curvature, and air velocity are varied for the swirling airflow. Spray visualization and phase Doppler interferometry techniques have been employed to obtain important parameters such as spray cone angle and mean drop size. In the numerical work, the Realizable [Formula: see text] turbulence model has been employed along with the Linearized Instability Sheet Atomization and Taylor Analogy Breakup to simulate spray field. The predicted results for the airflow field compare well with available experimental results in published literature. Good match is also found between the present predictions and measured spray data. The radial distribution of Sauter mean diameter exhibits peak values at the periphery of the spray near the injector, due to liquid swirl. The peak Sauter mean diameter shifts to the spray axis, beyond the recirculation zone, due to entrainment of droplets by the swirling air stream. The volume fraction of droplets exhibits multi-modal distribution, due to the interactions between spray droplets and recirculating airflow. A curved swirler gives rise to finer spray compared to a flat swirler, due to lower losses and better utilization of momentum.

Molluscicidal activity of 25% wettable powder of pyriclobenzuron sulphate against Oncomelania hupensis robertsoni

To evaluate the molluscicidal activity of a novel molluscicide pyriclobenzuron against Oncomelania hupensis robertsoni in the mountain regions of Yunan Province, and test its toxicity to fish, so as to provide scientific evidence for the extensive application of this molluscicide in schistosomiasis-endemic foci of Yunan Province. In the laboratory and snail-breeding field of Dali Prefecture, Yunnan Province, the molluscicidal activity of 5% wettable powder of pyriclobenzuron sulphate (25% PBU) against O. hupensis robertsoni was assessed by using the immersion and spraying method, and the acute toxicity of 25% PBU to carp fries was tested, while 25% wettable powder of niclosamide ethanolamine salt (50% WPNES) served as a control. The 1-, 2- and 3-day 25% PBU LC50 and LC90 values were 0.47, 0.25 and 0.23 mg/L, and 1.54, 0.61 and 0.49 mg / L for O. h. robertsoni by using the immersion method in laboratory, and immersion with 25% PBU at 1.0 mg / L for 1 day achieved a comparable molluscicidal efficacy in relative to 50% WPNES at 1.0 mg/L. Spraying with 25% PBU at 4.0 g/m2 achieved 1-, 3- and 7-day snail mortalities of 64.23%, 96.67% and 100.00% in laboratory, respectively, which were not significantly different from those caused by treatment with 50% WPNES at 1.0 g/m2 (all P values > 0.05). One-day field immersion with 25% PBU at doses of 1, 2 and 4 g/m3 resulted in snail mortalities of 90.00%, 93.33% and 100.00%, respectively, which were not significantly different from those caused by treatment with 50% WPNES at 1.0 g/m3 (all P values > 0.05), and 3-day field spraying with 25% PBU at doses of 2.0 and 4.0 g/m2 caused snail mortalities of 86.36% and 87.72%, respectively, which were not significantly different from those caused by 50% WPNES treatment (both P values > 0.05). The 24-, 48- and 72-hour LC50 values of 25% PBU to carp fries were 29.38, 24.62 and 23.38 mg/L, respectively, and no fish death was observed within 72 hours of exposure to 25% PBU at a concentration of 17.5 mg/L and lower. 25% PBU is a novel, highly potent and environment-friendly molluscicide that is feasible in fish ponds, and the recommended dose is 1 g/m3 for field immersion and 2 g/m2 for field spraying in schistosomiasis-endemic areas of Yunnan Province.

The effects of the spraying pressure and nozzle orifice diameter on the atomizing rules and dust suppression performances of an external spraying system in a fully-mechanized excavation face

The spraying dedusting technique using equipment that is mounted outside a roadheader is an important dust prevention measure in fully-mechanized excavation faces. In this study, ANSYS-FLUENT software was used for investigating the atomizing properties and the related variation rules of the nozzles with different orifice diameters (1.6 mm, 2.0 mm, 2.4 mm) under different spraying pressures from 1 MPa to 5.5 MPa. The conclusions are as follows: the relationship between the mean droplet size and spraying pressure can be fitted as a power function, as the spraying pressure increased, the variation of the droplet size tended to be small, and the uniformity degrees of the droplet size distribution reached the optimum level at a spraying pressure of 5 MPa. Under a spraying pressure of 5 MPa, the number of droplets in the target area increased greatly when a nozzle with an orifice diameter of 2.4 mm, the formed spray field exhibited the greatest spray concentration, which can wrap the cutting head effectively and provide the best performance with regard to dust suppression. Therefore, the use of a nozzle with an orifice diameter of 2.4 mm can achieve an optimal dust suppression performance under a spraying pressure of 5 MPa.

Experimental and theoretical studies on the droplet temperature behavior of R407C two-phase flashing spray

Flashing spray is a common phenomenon in many industrial fields. A rapid droplet temperature change in flashing spray is an important feature, which distinguishes this phenomenon from other traditional sprays. This study provides first-hand droplet temperature data of an R407C flashing spray, which serves as a substitute for R22, by conducting systematic experiments. A coupled droplet evaporation model is also introduced to predict the droplet temperature of flashing spray, rather than CFD simulation, for the first time considering the coupling of heat and mass transfer between a droplet surface and its surrounding region of influence. Experimental result shows that droplet temperature first decreases rapidly with axial distance, and then a gradual decrease in the downstream until its minimum value is reached. A hot core is observed near the nozzle exit, where the droplet temperature is higher at the spray center than in its periphery region. Droplet radial temperature distribution becomes uniform in the far spray field. The interaction of heat and mass transfer between the droplet surface and its surrounding region of influence is revealed using a coupled evaporation model. That is, the vapor mass fraction and temperature of the influence region undergo increase and decrease with evaporating time, respectively. Therefore, the coupled evaporation model presents better performance than a one-way evaporation model in predicting droplet minimum temperature. This predictive result agrees well with the experimental data. The minimum temperature of a predictive droplet is independent of the initial diameter and velocity of this droplet.

A new spray deposition pattern measurement system based on spectral analysis of a fluorescent tracer

To complement shortages of discrete sampling data and improve the detection accuracy of droplet deposition in unmanned aerial vehicle (UAV) spraying, we developed a new spray deposition pattern measurement system (SDPMS) based on a fluorescent tracer and spectral analysis. Then, we evaluated the system performance in two field spraying experiments in comparison with water-sensitive paper results. The system comprises a fluorescence scanner and spectral analysis program. The fluorescence scanner includes an ultraviolet light, spectrometer, far end controller, stepping motor, and sample reel. First, 1.0% fluorescent tracer solution is sprayed, and the droplets are collected on a paper strip. Then, the paper strip is scanned with the fluorescence scanner, and a set of fluorescence intensity values is collected and processed by the spectral analysis program. Finally, the spray deposition pattern is calculated. The experimental results showed that the spray deposition pattern from the SDPMS had a 0.89 correlation coefficient with that of water-sensitive paper. A linear regression model between fluorescence intensity and deposit coverage was constructed, with a coefficient of determination of 0.91 (F = 61.8845, P < 0.001). In addition, a linear regression model between fluorescence intensity and volume rate was constructed, with a coefficient of determination of 0.89 (F = 51.6639, P < 0.001). The SDPMS and field experiments offer a good foundation for the development of an improved system compatible with UAV spraying.

Analysis of internal flow and outlet velocity characteristics associated with dust suppression nozzles and their impact on spray field

In order to understand the relationship between nozzle structure and spray field, the present paper conducts velocity-based parametric study on two types of dust suppression nozzles, focusing on the link among nozzle structure, velocity distribution, and the resulting spray field. The simulation investigation indicates that the increase of flow velocity mainly occurs in the convergence section and the outlet region of a nozzle, with its magnitude dictated by the convergence angle, ratio of inlet to outlet diameter, and the length–diameter ratio of the outlet. Based on the velocity distribution characteristic of axis direction and radial direction near different nozzles’ outlet, one can predict that fluid density is higher in the central axis region and lower in the boundary region in spray field with cylindrical outlet, which can form a “solid cone” shape and stable spray. In the case where the nozzle outlet has “dash” type, one can find that the spray field, which associated with this type of nozzle, is a fan-shaped, with the fluid density fluctuating up and down. The above hypothesis has been corroborated by the spray experiments which have been conducted here. The simulation results concerning the internal flow field in dust suppression nozzles can provide guidance over the nozzle design and the parametric optimization and are of great significance to enhance the atomization quality of spray field.

Spray dynamics of HVO and EN590 diesel fuels

This investigation aims at quantifying the spray dynamics of diesel-like injection at the steady stage. A 1D model based on momentum flux conservation and combined with Gaussian radial profiles is derived to predict the axial and radial velocity, fuel concentration, liquid volume fraction and density distribution within the steady spray field. To validate the model over a range of conditions, global quantities such as spray tip penetration, spray cone angle, spray tip velocity, and spray volume was measured by diffused back-illumination imaging. The spray characteristics of hydrotreated vegetable oil (HVO) and European standard diesel fuel (EN590) under different ambient air conditions (36 kg/m3 and 115 kg/m3) are compared to further predict the local velocity, fuel concentration, liquid volume fraction and density distribution. The present results indicate that an accurate model of diesel-like spray evolution can be obtained for different fuel types and ambient air densities.

Detection of particle position from a linear interferometric out-of-focus image

A high precision method based on erosion match is proposed to extract the location coordinate of particles from a compression interferogram. With this method, particles can be positioned exactly when the overlap coefficients for that perpendicular and parallel to the fringes are less than 94.23% and 25% respectively. Super performance with the method is well confirmed by the synthetic and experiment data. Furthermore, the method can also be employed in the center detecting of complex fringe patterns for both circular and linear fringe images. The numerical and experimental results suggest that the method presented may be of considerable value to high-density spray field in accurately measuring both the particle location and its velocity.

Experimental characterization of multi-nozzle atomization interference for dust reduction between hydraulic supports at a fully mechanized coal mining face.

To analyze the distribution pattern concerning multi-nozzle interference spray particle granularity between hydraulic supports, the present study conducts atomization interference experimental characterization for three types of nozzles used in coal mines based on a Doppler laser interference spray dust suppression simulation experimental system. The results indicate that for single-nozzle atomization, the impact of spray pressure on spray droplet size is gradually subdued, and a spray pressure of 8MPa yields the best result; compared with single-nozzle spray, the multi-nozzle atomization interference effect can downsize the spray field overlapping zone, leading to an improved uniformity of overall spray particle distribution. As the spray field overlapping coefficient k increases, the particle size of the interference spray field decreases first and then increases. As the spray field overlapping coefficient reaches 0.4, the distribution of spray droplet size is most concentrated, corresponding to the optimal atomized dust suppression effect. Practical testing indicates that the optimal spray field overlapping coefficient measured at a fully mechanized mining face agrees well with the experimental result. Under the optimal parameters, the average total dust and respirable dust suppression rates measured at various measuring points on the downwind side during support relocation reach 78.93% and 80.53%, respectively.

Simulation and Experimental Study on Spray Characteristics of Gas-Assisted Urea Spray Gun

In this paper, the internal flow field and external spray characteristics of the spray gun were simulated and analyzed by establishing a coupling model of the gas-liquid two-phase flow of the spray gun. The spray particle size and cone angle under different gas path pressures were mainly studied. The calculation results showed that the spray particle size distribution had a large span, but the overall spray particle size was small. The liquid flow and the air pressure had a little influence on the spray cone angle. The spray SMD was tested by a three-dimensional particle dynamic analyzer (PDA), and the spray cone angle was photographed with a high-speed camera. The test data was basically consistent with the simulation results. The experimental results showed that the model can accurately simulate the internal flow field of the spray gun and the atomization process of urea. It can be used to analyze the characteristics of urea spray and provide a theoretical basis for the optimal design of urea spray gun.

Numerical Simulation and Experimental Verification of the Deposition Concentration of an Unmanned Aerial Vehicle

Abstract. To analyze the droplet deposition under the influence of the flow field of an unmanned aerial vehicle (UAV), a hand-held three-dimensional (3D) laser scanner was used to scan 3D images of the UAV. Fluent software was used to simulate the motion characteristics of droplets and flow fields under the conditions of a flight speed of 3 m/s and an altitude of 1.5 m. The results indicated that the ground deposition concentration in the nonrotor flow field was high, the spray field width was 2.6 m, and the droplet deposition concentration was 50 to 200 ug/cm2. Under the influence of the rotor flow field, the widest deposition range of droplets reached 12.8 m. Notably, the droplet deposition uniformity worsened, and the concentration range of the droplet deposition was 0 to 500 ug/cm2. With the downward development of the downwash flow field, the overall velocity of the flow field gradually decreased, and the influence interval of the flow field gradually expanded. In this article, the droplet concentration was verified under simulated working conditions by a field experiment, thereby demonstrating the reliability of the numerical simulation results. This research could provide a basis for determining optimal UAV operating parameters, reducing the drift of droplets and increasing the utilization rate of pesticides. Keywords: Unmanned aerial vehicle (UAV), Aerial application, Downwash flow field, Droplet deposition, Simulation analysis.

Biodynamic preparations, greater root growth and health, stress resistance, and soil organic matter increases are linked

Abstract The effects of biodynamic preparations were tested in the context of comparisons of conventional, organic, and biodynamic systems and diverse crop rotations in Washington and Wisconsin, USA. Wisconsin research also entailed testing a new nettle-and-manure-based field spray preparation (NCP). Focus was on winter wheat and maize and on soil quality. In Washington, preparations increased root growth of winter wheat, microbial biomass, and soil organic matter. In Wisconsin, applying a combination of preparations that included NCP increased root growth of maize, root health, and particulate organic matter in the soil. Relative to the organic treatments, root dry matter increases associated with the use of preparations varied from 12% to 39% and root length differences varied from 10% to 37% depending on the experiment, crop, year, and preparation application. The biodynamic + NCP treatment also induced substantial, positive yield compensatory effects for maize and wheat under stress condition years. The response slopes were practically identical for wheat and maize, indicating that the effect is of the same magnitude for both crops. Results were higher average grain yields and gross financial returns than for organic grain. The greater root production and root health stimulated by preparations is probably linked to greater vegetative growth, enhanced yield under stress conditions, and increased soil quality and carbon in soils.

Effects of droplet formation patterns on the atomization characteristics of a dust removal spray in a coal cutter

To improve the coverage of an external spray in a coal cutter and enhance the coal dust capture efficiency, the atomization characteristics of a dustproof spray were investigated using a self-constructed experimental system by considering different droplet formation patterns. In addition to the droplet diameter, the spray solution consumption, droplet number density and atomization angle were used to more comprehensively analyze the effects of spray pressure and nozzle structure on the atomization characteristics. It was found that the spray field formed by a nozzle with a 1.5 mm outlet diameter and a spray pressure of 5 MPa, had the optimal atomization characteristics, i.e. the droplet diameter was not significantly reduced over 5 MPa, while the solution consumption was optimal (7.69 L/min) at an outlet diameter of 1.5 mm. Droplet diameters were slightly reduced as the solution surface tension decreased. A novel nozzle distribution device, with two nozzles (the optimal distance between them was 15 cm), was designed and installed on the rocker arm of a coal cutter, enhancing the coverage of the dust removal spray. Field application verified that compared to a traditional spray, the total dust and respirable dust control efficiency of the optimized spray field were enhanced by over 8%, effectively improving the working environment in the underground coal mine.

A Riemannian Geometry Theory of Three-Dimensional Binocular Visual Perception.

We present a Riemannian geometry theory to examine the systematically warped geometry of perceived visual space attributable to the size–distance relationship of retinal images associated with the optics of the human eye. Starting with the notion of a vector field of retinal image features over cortical hypercolumns endowed with a metric compatible with that size–distance relationship, we use Riemannian geometry to construct a place-encoded theory of spatial representation within the human visual system. The theory draws on the concepts of geodesic spray fields, covariant derivatives, geodesics, Christoffel symbols, curvature tensors, vector bundles and fibre bundles to produce a neurally-feasible geometric theory of visuospatial memory. The characteristics of perceived 3D visual space are examined by means of a series of simulations around the egocentre. Perceptions of size and shape are elucidated by the geometry as are the removal of occlusions and the generation of 3D images of objects. Predictions of the theory are compared with experimental observations in the literature. We hold that the variety of reported geometries is accounted for by cognitive perturbations of the invariant physically-determined geometry derived here. When combined with previous description of the Riemannian geometry of human movement this work promises to account for the non-linear dynamical invertible visual-proprioceptive maps and selection of task-compatible movement synergies required for the planning and execution of visuomotor tasks.

Effects of spraying pressure and installation angle of nozzles on atomization characteristics of external spraying system at a fully-mechanized mining face

Aiming to effectively suppress excessively high dust concentration around the drums during coal cutting and the related dust particle dispersion issues at a fully-mechanized mining face, the present study employed experiments, numerical simulations, and field measurements to carry out an in-depth investigation of the dust suppression performance of an external spraying system. Firstly, the atomization characteristics of the nozzles with optimized macro-atomization performances were tested. According to the experimental results, hybrid nozzles with an orifice diameter of 2.0 mm and an X-shaped diversion core (type-B nozzles) delivered the best overall atomization performances at a spraying pressure of 8 MPa; in this case, the spraying angle and the effective spraying range were approximately 81.9° and 2.56 m, respectively. Next, numerical simulations were conducted to assess the dust suppression performances of an external spraying system, using ANSYS Fluent software. The results showed that, when the nozzles were installed at an inclination angle of 30° and operated at a spraying pressure of 8 MPa, the spray field formed could cover the whole dust-producing region around the drum. Meanwhile, the spray field near the coal cutter drum was not affected by airflow, which prevented dust particles being dispersed by the airflow, leading to a mitigation of pollution. Finally, field testing at the No. 30106 mining face of the Shiquan Coal Mine indicated that the mean overall dust suppression efficiency could reach up to 90.10%, i.e. the dust particles at this fully-mechanized mining face were effectively settled. To conclude, the dust pollution issues at a fully-mechanized mining face during the coal cutting process were adequately addressed by the measures investigated here.

Influence of Plasma Sprayed Coatings on Die Life during Hot Forging Process: A State of Art Review

Tooling and die failure is a prime concern for hot forging industry for survival in the competitive globe. Different methods are employed to protect the tools/dies from degradation. Thermal spraying is one of the most effective methods to protect the material from wear, thermal fatigue and plastic deformation due to adverse environments during hot forging process, thus increasing the life of material in use. A coating is a covering process that is applied to the surface of a material which is referred to as the substrate. The coating itself is either completely covered through the whole surface or the particular parts of the substrate. Different coatings are used to achieve the desired properties. In this process, relatively thick metallic, polymer, ceramic and composite coatings is deposited. The optimum coating process is selected on the basis of desired coating properties. Coating material is either in the form of wire, powder, rod, cord or molten-bath form. The procedure may be manual, mechanized or fully automated. This paper attempts to define some of the current important issues and research priorities in the plasma spray field.

Response of inner flow and spray characteristics of a pressure swirl injector to pressure oscillation in supply system

The present work focused on the response of the two phase flow of a pressure swirl injector to pressure oscillation in supply system. A mechanical pulsator was used to generate pressure oscillation in supply system. The inner flow of the injector and spray were captured by backlit shadowgraph technique and the droplet size was recorded by laser diffraction technique. In addition, image processing and proper orthogonal decomposition were used to analyze the data. The results indicate that the inner flow, spray and droplet size oscillate along with pressure oscillation mainly at the driving frequency. The oscillation of air core was used to characterize the inner flow. The dynamics of air core center and air core diameter was analyzed and the modes of the inner flow were obtained. Then, the way the oscillation propagated inside the nozzle was identified as a long wave manner. When the liquid was emanated from the nozzle, thick film resulted from pressure peak was faster when compared with thin film resulted from the trough of pressure oscillation. This characteristic was found to be responsible for the sudden shrink of the spray, and changed the spray pattern from a hollow cone to a pagoda. Finally, the thick and fast film produced a dense spray and large droplets. The whole paper discussed the response of inner flow and spray characteristics of a pressure swirl injector to pressure oscillation, and revealed the way the pressure oscillation propagated from supply system to spray field.

Identifying glyphosate-tolerant maize by soaking seeds in glyphosate solution

The identification of glyphosate-tolerant maize genotypes by field spraying with glyphosate is time-consuming, costly and requires treatment of a large area. We report a potentially better technique of seed-soaking to identify glyphosate-tolerant maize genotypes. The effects of soaking maize seeds in glyphosate solution under controlled conditions were studied on seed germination rate, seedling morphological indices, seedling growth and leaf chlorophyll content. These responses were compared among a glyphosate-tolerant transgenic maize cultivar CC-2, glyphosate-susceptible inbred line Zheng 58 (the recurrent parent of CC-2) and hybrid cultivar Zhengdan 1002. The results showed that the germination rate, seedling morphological indices and leaf chlorophyll content of glyphosate-tolerant CC-2 seeds did not change significantly among five different concentrations of glyphosate treatment (0 to 2%). In contrast, germination rates, seedling morphological indices and leaf chlorophyll contents of Zheng 58 and Zhengdan 1002 seeds were significantly negatively affected by exposure to increasing concentrations of glyphosate. The glyphosate-tolerant inbred line CC-2 displayed a strong tolerance to glyphosate after soaking in 0.1 to 2.0% glyphosate solutions, while both the inbred line Zheng 58 and hybrid Zhengdan 1002 were susceptible to glyphosate. The accuracy of the glyphosate-soaking method for screening glyphosate-tolerant maize was confirmed using a field spraying trial.

Experimental Studies on the Spraying Pattern of a Swirl Nozzle for Coal Dust Control

The experimental and numerical studies were performed to understand the atomization mechanism of pressure spray of a swirl nozzle. The design and performance parameters such as spray cone angle, velocity of particles, spray pressure, and Sauter Mean Diameter (SMD) of the droplets were studied using a laser particle size analyzer and high-speed camera. The results show that the SMD increases at first, then decreases as the spray distance increases, and finally tends to be stable after 1 m. The SMD is largest in the center of the spray field and decreases gradually along the radial direction. The SMD distribution is more concentrated near the nozzle. Increasing spray pressure and deceasing nozzle diameter both can make the SMD distribution more concentrated and uniform. The swirl nozzle has been used in a coal mine and was shown to be very effective in suppressing coal dust compared to other traditional nozzles.

Development of a novel wind-assisted centralized spraying dedusting device for dust suppression in a fully mechanized mining face.

Aiming at addressing serious pollution in the No. 30106 fully mechanized coal mining face of Shiquan Coal Mine during coal cutting process, the spraying device between hydraulic supports was improved through the combination of experimental analysis, numerical simulation, and field measurement, and a novel wind-assisted centralized spraying dedusting device was developed. The newly developed device could make the formed spraying field more concentrated on the dust-producing source around the coal shearer's drum, and thus significantly enhanced the spraying performance. According to numerical simulation results, the spraying performance reached the optimum at a hydraulic pressure of 8MPa for the spraying device and an air pressure of 1MPa for the pneumatic motor; under these optimal conditions, the droplet concentration in the spraying field around the coal cutter drum was as high as 24.85g/m3, and the formed high-concentration spraying field could basically cover the whole section in the spraying field from coal wall to the support pillar. Field measured results revealed that, at a hydraulic pressure of 8MPa and an air pressure of 1MPa, the dust suppression rate around coal cutter driver reached up to 87.96%, suggesting that the developed wind-assisted centralized spraying dedusting device had remarkable dust suppression performance and could effectively improve the operating environment in the fully mechanized mining face. Graphical Abstract In this paper, we have designed a novel wind-assisted centralized spraying dedusting device and studied the optimal spray parameters. Firstly, the nozzles were selected according to the multi-factor experimental platform for measuring the spraying field's atomization characteristics. Secondly, we had a numerical simulation of the fully mechanized mining face. And the third, we tested the effect of dust removal.