Low Spray Research Articles

Influence of Gas Temperature and Heat Treatment on Microstructure and Properties of Cold Sprayed Commercially Pure Titanium

Diffusion of oxygen and nitrogen in the cold sprayed commercially pure Ti (CS CP Ti) deposits profoundly impacts their mechanical properties. One plausible approach to additively manufacture a malleable (wrought) and high-density Ti is optimizing CS deposition parameters considering a reduction in porosity for the following heat treatment. Herein, we examined porosity, bulk density, and hardness characteristics of CS CP Ti deposits produced at varying processing gas temperatures (700, 800, and 900°C), which significantly influences the interactions of CP Ti with oxygen and nitrogen. Post-processing heat treatments at 800, 900, and 1000°C were performed in a high vacuum furnace, respectively, which diminished splat boundaries and submicron pores with increasing grain size. SEM images revealed that CS CP Ti had a dense microstructure with low porosity. According to LECO research, low spraying temperatures (i.e. 700°C) maintained oxygen and nitrogen levels in the CS CP Ti deposits at the same level as the stock powders. The bulk density of CS CP Ti produced at 900 °C matched that of wrought CP Ti metal. In addition, to improve the mechanical properties of CS CP Ti deposits, we looked at the link between CS conditions and heat treatment.

Optical and photoluminescence studies of precursor stabilised Aluminium-Gallium Zinc oxide thin films

A low cost, versatile, and cost-effective ultrasonic spray pyrolysis approach was used to generate aluminium and gallium doped Zinc Oxide thin films on stretchable corning glass substrates at 400 °C temperature. Ammonium acetate is employed as a stabilizing ingredient in the precursor solution. According to X-ray diffraction patterns, high quality polycrystalline films on glass substrates grew successfully. As Ga doping levels rose, photoluminescence spectra showed an increase in exciton peak emission. As time passes, photoluminescence spectra show a strong emission peak centred at 3.24 eV that is progressively pushed toward higher wavelength. When Aluminum and Gallium were added into the Zinc Oxide lattice, the crystalline size was reduced and the thin film residual stress was raised. In the visible area, all films were extremely clear, with an average transparency of 80%. The optical energy band gap increased from 3.12 eV to 3.3 eV when the doping concentration increased.

Variation of sulfur concentration on the effective deposition of solution processed ZnS thin films for buffer layer in thin film solar cells

The influence of sulfur concentrations on the growth of ZnS thin films were investigated by low cost chemical spray pyrolysis and chemical bath deposition techniques. The deposited ZnS films showed the major peaks at (111) zinc blende structure from X-ray-diffraction. The FESEM analysis resulted that the deposited films were identified as sphere-like particles for both deposition techniques and the ZnS particle size improved as the sulfur concentration increased in the prepared solutions. The UV analysis showed higher optical transmittance > 70% in the visible region and PL spectra exhibited the defects-free ZnS peaks at blue-green emission bands in the range between 350 nm and 550 nm by both deposition methods. The linear response of I-V characteristics denote to ohmic behavior of the deposited films and the calculated resistivity of the films were in the range of 107Ω.cm and 108 Ω.cm. Hence, the characterized results suggest that the deposited ZnS films with increasing sulfur concentration using both deposition methods show optimum properties for buffer layers in thin film photovoltaics.

Suppression Efficiency for Dust from an Iron Ore Pile Using a Conventional Sprinkler and a Water Mist Generator

Re-suspension of iron ore dust presents a constant hazard in the working environment within steel production plants. Herein, the optimal operating parameters for maximum dust suppression efficiencies through a water mist generator and a conventional sprinkler for particulate matter (PM) originating from an iron ore pile measuring about 2 m in height and with a stacking angle of about 30° are investigated. The effects of operating parameters including wind velocity, spray angle, and mode of water supply on dust suppression efficiencies are evaluated. Size differentiated PM samples were collected from the upwind and downwind locations of the iron oral pile and the dust suppression efficiencies are determined. The operating parameters with the highest dust suppression efficiencies using the water mist technology are low spray angle, low wind velocity, and intermittent water supply, while those for water sprinkling technology are high spray angle, low wind velocity, and intermittent water supply. The average dust suppression efficiencies for Total Suspended Particles (TSP), PM10, and PM2.5 for the mist generators are 80.9%, 77.9%, and 76.9%, respectively, whereas those for the conventional sprinklers are 76.4%, 72.9%, and 72.7%, respectively. For the surfactant to water ratios of 0.024, 0.022 and no surfactant, the ratio of 0.024 had the highest dust suppression efficiencies for TSP, PM10, and PM2.5 at 90.9%, 89.5%, and 89.0%, respectively. Insights from this investigation can be applied to optimize the dust suppression methods to ensure economical consumption of water and energy.

Effect of the Substrate Surface Profile on the Bonding Strength of the Aluminum Thermal Sprayed on the Low Carbon Steel

The contact surface of thermal spray significantly affected bonding strength and coating elasticity. This work aimed to evaluate the effects of contact surface conditions characterised by substrate surface profile and spray pressure on the bonding and buckling strength of aluminium thermal sprayed on the low-carbon steel substrate. The SS400 low-carbon steel substrate was profiled using the milling process to form the V, small V, U, and flat profiles that were subsequently roughed by employing the sandblasting process. A coating comprising 99% aluminium was sprayed onto the substrate surface with different spraying pressures of 3.5, 4.5, and 5.5 bar. Pull-off and buckling tests were performed for determining thermal spray characteristics. The results of this work showed that the optimal bonding strength of the coating was obtained for the thermal spray specimen that had a flat substrate surface, and the spraying pressure was set to 5.5 bar. Generally, low spraying pressure lead to be low bonding strength and vice versa. Profiled surface was not profitable on the mechanic properties of thermal spray bonding.

Phosphonate Treatment Effects on Phytophthora Root Rot Control, Phosphite Residues and Phytophthora cactorum Inoculum in Young Apple Orchards.

Phytophthora root rot, caused by Phytophthora cactorum, is an economically important disease on young apple trees. Limited information is available on the effect of different phosphonate application methods and dosages on disease control, fruit and root phosphite concentrations, and soil and root pathogen inoculum levels. Evaluation of phosphonate treatments in three apple orchard trials (two in the Grabouw and one in the Koue Bokkeveld region) showed that foliar sprays (ammonium or potassium phosphonate), trunk sprays and trunk paints, were equally effective at increasing trunk diameter in one trial and yield in a second trial over a 25-month period. Foliar ammonium and potassium phosphonate sprays (12 g of phosphorous acid/tree), and two different dosages of the ammonium phosphonate sprays (∼4.8 g or 12 g of phosphorous acid/tree) were all equally effective at improving tree growth. The addition of a bark penetrant (polyether-polymethylsiloxane-copolymer) to trunk sprays did not improve the activity of trunk sprays. The low dosage ammonium phosphonate foliar spray (∼4.8 g a.i./tree) was the only treatment that, in general, yielded significantly lower root phosphite concentrations than the other phosphonate treatments. Root phosphite concentrations were significantly positively correlated (P < 0.0001) with an increase in trunk diameter and negatively (P < 0.0001) with P. cactorum root DNA quantities. Phosphite fruit residues were <31 ppm for all treatments, with the trunk paint treatment (80 g of phosphorous acid/tree applied annually) yielding significantly lower residues than the higher dosage foliar sprays (∼12 g a.i./tree). Twenty-one months posttreatment, most of the phosphonate treatments in all of the trials similarly significantly reduced P. cactorum DNA quantities estimated directly from roots, but not from soil based on soil baiting DNA analysis. Pathogen quantities in fine feeder roots did not differ significantly from those in higher-order roots (<5 mm diameter). P. cactorum DNA quantities estimated using DNA quantification directly from roots were significantly correlated (P < 0.0001) with those obtained through root leaf baiting DNA analysis and, to a lesser extent, with soil leaf baiting DNA quantities (P = 0.025).

Study on dust diffusion characteristics of continuous dust sources and spray dust control technology in fully mechanized working face

When the roadheader works, it will produce a lot of dust, causing serious dust pollution to the roadway. In order to solve the problem of dust pollution in fully mechanized working face, the dust pollution law of roadway and the low surface tension spray dust removal technology of heading head were studied by fluid solid coupling simulation analysis software FLUENT. The results show that the optimum pressure of the spray head is 3.0 MPa, the droplet size of 50% is less than 3.00E-05 m, and the spray angle is 35 degrees. Reducing the surface tension of the solution can improve the atomization effect; When the surface tension drops to 61.9 mN/m, the spray size can be reduced obviously. Injection scheme D is the best injection scheme. Finally, according to the simulation results, the design of low surface tension spray dust suppression device for roadheader is carried out. The test and field application are carried out. The field application analysis shows that the dust reduction rate can reach 90%, and the dust reduction rate of respiratory dust can reach 85%.

INTELLIGENT HEALTH STATUS DETECTION METHOD FOR LOCOMOTIVE FUEL CELL BASED ON DATA-DRIVEN TECHNIQUES

Main drawbacks of fuel cell systems, namely, high cost, poor reliability, and short lifespan, limit the large-scale commercial application of fuel cell systems. The health status detection of fuel cell systems for locomotives is of great significance to the safe and stable operation of locomotives. To identify the failure modes of the fuel cell system accurately and quickly, this study proposed an intelligent health status detection method for locomotive fuel cells based on data-driven techniques. In this study, the actual test data of a 150-kW fuel cell system for locomotives was analyzed. The t-distributed stochastic neighbor embedding (t-SNE) algorithm was combined with the general regression neural network (GRNN) to intelligently detect the health status of the fuel cell system for locomotives. Specifically, t-SNE was used to process the high-dimensionality and strong coupling raw data of health status, enabling the dimensional reduction of the raw data to reflect essential features. Then, GRNN was used to identify the feature data to achieve the fast and accurate detection of the health status of the fuel cell system. Results show that the proposed method can effectively detect four health conditions, namely, normal state, high inlet coolant temperature, low air pressure, and low spray pump pressure, with a diagnostic accuracy of 98.75%. This study is applicable to the analysis of the actual measurement data of high-power level fuel cell systems and provides a reference for the health status detection of fuel cell systems for locomotives. Keywords: fuel cell system for locomotive; data-driven; general regression neural network; t-distributed stochastic neighbor embedding; health status detection

DEVELOPMENT OF ECOLOGICAL DENIM BLEACHING METHODS

Although the textile industry has many products to offer to humanity, it consumes a lot of energy and indirectly causes greenhouse gas emissions. With increasing environmental awareness, parameters such as the cost and performance of each industrial activity to society, as well as the use of natural resources and the possibility of causing global environmental problems to have become more frequently considered factors. In the denim bleaching process, the desired effect is usually obtained with the help of sodium hypochlorite. Sodium metabisulfite is then used for the neutralization process. Since these processes are carried out at high liquor ratios, the waste load resulting from the consumption of necessary chemicals and water is also high. In this study, ecological bleaching methods have been developed as an alternative to the conventional sodium hypochlorite bleaching method by reducing the use of water and chemicals with low liquor and spraying bleaching methods. Denim garments subjected to bleaching with low liquor and spraying methods were compared with denim garments applied to sodium hypochlorite bleaching in industrial washing machines according to exhaustion method. In the spraying method, the mixture coming out of the narrow nozzle is mixed with the compressed air by means of a specially designed spray gun and sprayed in very small droplets. Thus, a good atomization is ensured, and a low liquor ratio water cloud is created.

Fabrication of nanostructured NiO and NiO:Cu thin films for high-performance ultraviolet photodetector

In this work, pure NiO and NiO:Cu based photodetectors with different concentrations of Cu dopants (0, 0.5,1.0, and 1.5 wt%) were coated on glass substrates by using a simple, low cost nebulizer spray pyrolysis technique. Their structural, morphological, optical (UV–Vis absorption and photoluminescence), and ultraviolet (UV) sensing features were characterized with state-of-the-art analytical techniques. The structural studies confirm that the prepared films have crystalline nature and possess a cubic structure. From the absorption measurement, the optical bandgap ( E g ) of the deposited films decreases with the increase in Cu dopants. Photoluminescence study illustrates that 1.0% of Cu doping significantly improves the physical property of the NiO:Cu films and also its UV sensing study suggests that the 1.0% of NiO:Cu film could be better suited for high-speed optoelectronic devices due to their high Responsivity (0.202 AW -1 ), External quantum efficiency (47%), and Detectivity (5.9 × 10 9 jones) values. A possible mechanism of the photodetector performance under air and UV illumination is also discussed in this work. • First time investigation on Cu insists of NiO films based UV photodetector by simple nebulizer spray method. • Reported the increase of photocurrent with respect to bias voltage for enhancing photoelectric properties. • Decrease of the optical bandgap for Cu doped films due to the observed redshift in absorption and higher crystallite size. • Maximum responsivity, external quantum efficiency, and specific detectivity were observed for the 1% Cu doped NiO detector. • A possible mechanism for enhancing photocurrent under UV illumination was also discussed with a schematic diagram.

Phone App to Perform Quality Control of Pesticide Spray Applications in Field Crops

It has been recognized for decades that low and inconsistent spray coverages of pesticide applications represent a major challenge to successful and sustainable crop protection. Deployment of water-sensitive spray cards combined with image analysis can provide valuable and quantitative insight into spray coverage. Herein we provide description of a novel and freely available smartphone app, “Smart Spray”, for both iOS and Android smart devices (iOS and Google app stores). More specifically, we provide a theoretical description of spray coverage, and we describe how Smart Spray and similar image-processing software packages can be used as decision support tools and quality control for pesticide spray applications. Performance assessment of the underlying pixel classification algorithm is presented, and we detail practical recommendations on how to use Smart Spray to maximize accuracy and consistency of spray coverage predictions. Smart Spray was developed as part of ongoing efforts to: (1) maximize the performance of pesticide sprays, (2) minimize pest-induced yield loss and to potentially reduce the amount of pesticide used, (2) reduce the risk of target pests developing pesticide resistance, (3) reduce the risk of spray drift, and (4) optimize spray application costs by introducing a quality control.

Effect of Nozzle Type and Adjuvants on Spray Coverage on Apple Leaves

Three non-ionic adjuvants, Agral, Silwet, and Greemax, at three concentrations, were applied on apple leaves with the use of hollow cone nozzles (TR) and air-induction nozzles (ID) to verify the assumption that adjuvants may improve spray coverage obtained by coarse droplets, and thereby ensure both satisfactory application quality and an environmental advantage. Spray coverage and droplet density were measured on both sides of the leaves. The adjuvants enhanced the spray coverage when applied at a certain concentration level. In general, the adjuvant coverage produced by the ID nozzles equaled the pure water coverage produced by the TR nozzles, thereby showing the adjuvants’ potential to compensate for the lower spray coverage usually obtained by coarse spray. A higher spray coverage was obtained on the lower side of leaves, which is discussed in terms of leaf surface properties. In the experiment with the mixture of Silwet and the fungicide Delan (dithianon), the product interacted with the adjuvant, resulting in the reversed picture of spray coverage and droplet density on the upper and lower leaf sides compared to the results obtained for the adjuvant alone. The combination of coarse spray nozzles with adjuvants may reduce environmental pollution without compromising the quality of spray applications in fruit growing.

Artificial neural networks in the evaluation of the influence of the type and content of carrier on selected quality parameters of spray dried raspberry powders

In the paper an attempt was made to evaluate influence of type (maltodextrin, gum Arabic and inulin) and content (50, 60, 70% solids) of carrier on quality of raspberry powders. The different types of powders were compared taking into account the structure of microparticles, water activity and their humidity. The use of modern methods such as: low temperature spray drying, artificial intelligence together with visual technique supported by electron microscope are undoubtedly an innovation in this solution. The aim of this undertaking is monitoring the process in order to obtain raspberry powders characterized by high quality characteristics. The paper shows the created neural models, which allow to obtain homogeneity on the basis of microparticles of powders as well as their microbiological condition (indirectly via water activity and humidity). The created networks were characterized by low Root Mean Square and high effectiveness of classification on the level of 99%.

Optimization of chemically sprayed ZnS films by Mn doping

In this study, undoped and Mn doped ZnS films were grown on microscope glass substrates at substrate temperature of 400 ± 5 °C by using a low cost Ultrasonic Spray Pyrolysis technique, and the effect of Mn doping on some physical properties of ZnS films was investigated. Structural, optical, electrical and morphological properties of all films were analyzed using X-ray diffractometer (XRD), UV–Vis spectrophotometer, two-probe technique and atomic force microscope (AFM), respectively. X-ray diffraction studies showed that all films were formed in ZnS hexagonal structure and the crystallization levels of the films were relatively improved due to the increase in the Mn doping ratio, especially for 4% doped films. It was determined that the average transmittance value of undoped ZnS film in the visible region is 38% and this value increases to 60% for the sample doped by Mn at the highest rate (12%). The band gap values of the films were calculated using the Tauc equation and determined to be between 3.82 and 3.94 eV. Electrical resistivity values of the films decreased significantly due to the Mn doping. Mn doping also caused ZnS films to have uniform surface morphologies consisting of noticeable particle formations. Figure of merit calculations showed that Mn doping has a favorable effect on ZnS films and ZnS:Mn (12%) films may be promising materials for applications such as photovoltaic solar cells and optoelectronic devices.

Secondary aerosol formation from dimethyl sulfide – improved mechanistic understanding based on smog chamber experiments and modelling

Abstract. Dimethyl sulfide (DMS) is the dominant biogenic sulfur compound in the ambient marine atmosphere. Low-volatility acids from DMS oxidation promote the formation and growth of sulfur aerosols and ultimately alter cloud properties and Earth's climate. We studied the OH-initiated oxidation of DMS in the Aarhus University Research on Aerosol (AURA) smog chamber and the marine boundary layer (MBL) with the aerosol dynamics and gas- and particle-phase chemistry kinetic multilayer model ADCHAM. Our work involved the development of a revised and comprehensive multiphase DMS oxidation mechanism, capable of both reproducing smog chamber and atmospheric relevant conditions. The secondary aerosol mass yield in the AURA chamber was found to have a strong dependence on the reaction of methyl sulfinic acid (MSIA) and OH, causing a 82.8 % increase in the total PM at low relative humidity (RH), while the autoxidation of the intermediate radical CH3SCH2OO forming hydroperoxymethyl thioformate (HPMTF) proved important at high temperature and RH, decreasing the total PM by 55.8 %. The observations and modelling strongly support the finding that a liquid water film existed on the Teflon surface of the chamber bag, which enhanced the wall loss of water-soluble intermediates and oxidants dimethyl sulfoxide (DMSO), MSIA, HPMTF, SO2, methanesulfonic acid (MSA), sulfuric acid (SA) and H2O2. The effect caused a 64.8 % and 91.7 % decrease in the secondary aerosol mass yield obtained at both dry (0 % RH–12 % RH) and humid (50 % RH–80 % RH) conditions, respectively. Model runs reproducing the ambient marine atmosphere indicate that OH comprises a strong sink of DMS in the MBL (accounting for 31.1 % of the total sink flux of DMS) although less important than the combined effect of halogen species Cl and BrO (accounting for 24.3 % and 38.7 %, respectively). Cloudy conditions promote the production of SO42- particular mass (PM) from SO2 accumulated in the gas phase, while cloud-free periods facilitate MSA formation in the deliquesced particles. The exclusion of aqueous-phase chemistry lowers the DMS sink as no halogens are activated in the sea spray particles and underestimates the secondary aerosol mass yield by neglecting SO42- and MSA PM production in the particle phase. Overall, this study demonstrated that the current DMS oxidation mechanisms reported in literature are inadequate in reproducing the results obtained in the AURA chamber, whereas the revised chemistry captured the formation, growth and chemical composition of the formed aerosol particles well. Furthermore, we emphasize the importance of OH-initiated oxidation of DMS in the ambient marine atmosphere during conditions with low sea spray emissions.

The transient flow mechanism and intermittent film thickness evolution regulation of droplet mode for horizontal tube falling film

The behavior of falling film over horizontal has significant impacts on the efficiency of heat and mass transfer for the horizontal tube evaporators and absorbers especially for intermittent droplet model at low spray density, which has lower heat and mass transfer resistance. Thus it is critical to illuminate transient and intermittent flow mechanism of droplet dynamic behavior and film thickness evolution regulation over horizontal tube falling film at low spray density. A two dimension multi-phase flow mode for superhydrophilic surface was established to capture the microscopic flow mechanism. The results indicated that droplet generation and growth stages accounted for more than half of the droplet life cycle and an obvious droplet retraction and pulsation were first observed during droplet generation due to surface tension and local additional pressure. Further, the whole life cycle transient and intermittent film thickness map of droplet mode was depicted. And found that the liquid film thickness transient evolution regulation of droplet mode could be split into two zones: impact zone and stable zone. For impact zone, the film thickness was rapidly decreased with the spreading of the liquid film from the millimeter level to 200 μm within 0.2 s. While for stable zone, film thickness almost maintained stable over a long period time until the next droplet impacted. Because of the intermittent of droplet generation and movement, the change of film thickness of droplet mode with spray Reynolds was achieved by increasing impact frequency of droplet impact instead of the volume of a single droplet.

Spray Coverage and Biological Efficacy of Single, Twin Symmetrical, and Twin Asymmetrical Flat Fan Nozzles

Abstract Proper selection of nozzle type and spray volume is essential to optimize herbicide dose, reducing its adverse environmental effects. It has not been sufficiently evaluated which nozzle type (twin symmetrical flat fan nozzle or the twin asymmetrical one) is more efficient and whether pinoxaden application is more efficient at a low or high spray volume. The spray coverage of a single, twin symmetrical, and twin asymmetrical flat fan nozzles, each in the sizes of 110015, 11002, 110025, 11003, 11004, and 11005 on the moisture-sensitive papers (MSPs) was investigated. The biological efficacy of treatments using pinoxaden against wild oat was investigated. Unlike other nozzle types, the single flat fan nozzle could not cover MSP placed vertically behind the nozzle trajectory. Except for the latter, each nozzle type could cover the MSPs more efficiently with increase in nozzle size. Generally, the nozzles’ performance was twin symmetrical &gt; single = twin asymmetrical flat fan nozzles. A larger nozzle size improved the coverage of MSPs but increased the effective dose (ED50; dose that gives a 50% reduction in dry weight), indicating a decrease in the efficacy of pinoxaden. Among all treatments, the lowest ED50 value was obtained by the twin symmetrical flat fan nozzle 110015 (5.2 g a.i. ha−1). The smaller, more concentrated droplets are required to achieve optimal pinoxaden efficacy against wild oat, which can be provided by a twin symmetrical flat fan nozzle with a smaller size.

Bandgap tuning in ZnO thin films and enhanced n-type properties through Mn doping synthesized by a simple spray pyrolysis

Undoped and manganese (Mn)-doped zinc oxide (ZnO) thin films have been deposited onto glass substrates at 300[Formula: see text]C using a low cost spray pyrolysis technique. Structural, optical and electrical properties of the as-deposited films have been investigated. Scanning electron microscopy images show the existence of clusters with well-defined nucleation centers consisting of highly dense ganglia-like fibers over a large area around the nucleation center. Chemical compositions of the ZnO and Mn-doped ZnO thin films are studied by using energy dispersive X-ray (EDX) analysis. X-ray diffraction spectra depict that the films have polycrystalline wurtzite structure. The average crystallite sizes are calculated in the range of 8–16 nm by Williamson–Hall method and found in good agreement with Scherer method. Optical transmittance of the films is about 80% in the visible region. Bandgap energy is tuned to 2.83 eV from 3.10 eV with increasing Mn doping. Electrical resistivity at room-temperature decreases significantly with increasing Mn doping as well as increasing temperature from 300–440 K. The activation energies in the temperature ranges 300–350 K and 350–440 K are found to be in the range of 0.25–0.16 eV and 0.35–0.59 eV, respectively. Hall Effect measurements show that the thin films have negative Hall co-efficient indicating [Formula: see text]-type conductivity at room-temperature. Carrier concentration is found to be of the order of 10[Formula: see text] cm[Formula: see text].

Study on the Atomization Characteristics of Flat Fan Nozzles for Pesticide Application at Low Pressures

Spraying is the most widely used means of pesticide application for pest control in agriculture and forestry. The atomization characteristics of the nozzles are directly related to the spray drift, rebound, and deposition. Previous research studies have mainly focused on the change pattern of atomization characteristics. Mathematical descriptions of the atomization characteristics of flat fan nozzles are rare, and pesticide application theories are also insufficient. Atomization characteristics mainly include droplet size and velocity. This study analyzes the influence of the spray parameters (spray angle, pressure, and equivalent orifice diameter of nozzles) and the spatial position in the flow field. To obtain the atomization characteristics of flat fan nozzles, the phase Doppler particle analyzer (PDPA) was selected for the accurate measurement of the droplet sizes and velocities at distances 0.30–0.60 m, using low spray pressures (0.15–0.35 MPa). The droplet size and velocity models were then established and validated. The results revealed that the average absolute error of the droplet size model was 23.74 µm and the average relative error was 8.23%. The average absolute and relative errors of the droplet velocity model were 0.37 m/s and 7.86%, respectively. At a constant spray pressure and angle, there was a positive correlation between the droplet size and the equivalent orifice diameter of the nozzles. The test also verified that the spray angle and distance had a negative correlation with the droplet velocity at a given pressure. The spray distance had no effect on the spray axial droplet size at constant spray pressure. In addition, the spray angle greatly affected the droplet velocity along the X-axis; similarly, the spray parameters, especially spray angle, greatly affected the droplet size.

On the Characteristics of Cold Spray Technology and Its Application in Aerospace Industries

Cold spraying technology is an advanced spraying technology developed based on the principles of aerodynamics. It is mainly used to deposit and repair the surface of metal alloy parts to ensure that the parts have better mechanical properties and service life. Compared with traditional thermal spraying technology, cold spraying technology has many advantages, such as low spraying temperature, low oxygen content and low porosity, and it is not easy to cause oxidation, burning, phase change and other phenomena during spraying. This article reviews the principles, technical parameters, and characteristics of cold spray technology, focusing on the effects of powder particle size and shape, particle and substrate temperature, critical speed, spray gun, collision angle, and spray distance on coating quality and deposition efficiency. In addition, the current research and application status of cold spray technology in the preparation of anti-corrosion coatings, high temperature resistant coatings, high temperature oxidation and wear resistant coatings are discussed, and the development prospects of cold spray technology are prospected.