Spray System Research Articles

Effect of heat treatment on the gas-atomized nickel‑aluminum bronze feedstock powders for cold spray

Due to the high strength of the nickel‑aluminum bronze (NAB), the cold spray deposition efficiency of the NAB powders was less than satisfactory. To improve the deformation behavior of powder, different heat treatment strategies were adopted for gas atomized NAB powders and then the heat-treated powders were deposited on NAB substrates using a high-pressure cold spray system. For various powders and their corresponding deposits, a series of related characterizations were performed. The results indicate that the microstructure of the gas-atomized powder was mainly composed of martensitic β′ and bainite α with high hardness, resulting in low deposition efficiency and poor bonding between particles and particles in the prepared deposits. An effective technique of heat treatment can eliminate the non-equilibrium structure in the gas atomized powder, reduce the hardness of the powder, and significantly improve the deposition efficiency and enhance particle interface bonding.

Molecular simulation study of the influence of different surfactants on the wetting characteristics of anthracite

The reduction of dust pollution in coal mines is of great importance both for protection of the environment and for the occupational safety and health of coal mine workers. The reduction of dust from anthracite has been a challenge due to its inherent hydrophobicity and high metamorphism. As a result, surfactants are commonly added to water to improve the wettability of coal, thereby improving the dust reduction efficiency of a water spray system. To clarify from a microscopic perspective the effect of different surfactants on the wettability of anthracite, models for the anthracite-surfactant-water system were established, and adsorption configuration, relative concentration distribution, and the diffusion coefficients of water molecules in the systems were thoroughly investigated with molecular simulations. The results showed the directional arrangement of surfactants in the simulation systems after 150 ps of equilibration, resulting in the reduced surface tension of the water-surfactant solution and enhanced wettability of anthracite. Along the (001) normal direction, the relative concentration of sodium dodecylbenzenesulfonate (SDBS) (15.32), the anthracite-water overlapping area, the diffusion rate of water molecules, and the activity (DSDBS = 0.97 × 10-8 m2·s−1) were maximized, indicating the excellent wettability effect of SDBS. The results of the study are of practical significance for improving the wetting effect of anthracite, improving the dust reduction efficiency, and safeguarding the occupational safety and health of personnel.

Effects of header design on thermal characteristics of multi-nozzle steam spraying

The distribution header of small-scale steam systems, commonly employed in household items like steam cleaners, is pivotal for dictating the spray characteristics of the steam generated. For uniform spray performance across multiple outlets, it's imperative to discern the design factors influencing this outcome. We numerically assessed the flow characteristics of steam in a spraying system with three nozzle outlets and scrutinized the impact of header design parameters on uniformity. Through a multiphase numerical model, numerical simulations were conducted. Our analysis revealed that decreasing the diameter of the three outlets promoted a more even mass flow rate of the sprayed steam from each outlet, having a minimal effect on temperature consistency. In contrast, enlarging the tapering angle of the header improved temperature uniformity up to 62.5 % but negatively influenced the uniformity of the steam spray amount when outlet diameters were consistent. Notably, when the combined area of the outlets was increased, there was a decline of up to 85 % in the uniformity of the discharged steam mass among the outlets with an increased tapering. This research offers insights that are anticipated to inform future studies and advancements in steam spraying system optimization, enhancing performance and efficiency for applications such as steam cleaning and sterilization processes.

One pot synthesis of high entropy rare earth zirconate ceramics with low thermal conductivity for high performance thermal-barrier coatings

By using the one pot synthesis method, zirconate rare earth ceramic powders with high entropy and low thermal conductivity were prepared. The phase and microstructure of the prepared powder and sintered ceramics were analyzed by x-ray diffraction, Raman spectroscopy and scanning electron microscopy. The results show that the prepared powder may be used directly for atmospheric plasma spraying. The ceramic prepared from this powder exhibited a density of 96.87 %, improved thermal conductivity and thermal expansion coefficient. Coating materials were prepared using an atmospheric plasma spraying system, with the LSZC coating demonstrating the highest bond strength of 48.81 MPa and thermal shock resistance of 18 cycles.

An Experimental Study on Blade Surface De-Icing Characteristics for Wind Turbines in Rime Ice Condition by Electro-Thermal Heating

Wind turbines in cold and humid regions face significant icing challenges. Heating is considered an efficient strategy to prevent ice accretion over the turbine’s blade surface. An ice protection system is required to minimize freezing of the runback water at the back of the blade and the melting state of the ice on the blade; the law of re-freezing of the runback water is necessary for the design of wind turbine de-icing systems. In this paper, a wind tunnel test was conducted to investigate the de-icing process of a static heated blade under various rime icing conditions. Ice shapes of different thicknesses were obtained by spraying water at 5 m/s, 10 m/s, and 15 m/s. The spray system was turned off and different heating fluxes were applied to heat the blade. The de-icing state and total energy consumption were explored. When de-icing occurred in a short freezing time, the ice layer became thin, and runback water flowed out (pattern I). With an increase in freezing time at a low wind speed, the melting ice induced by the dominant action of inertial force moved backward due to the reduction in adhesion between the ice and blade surface (pattern II). As wind speed increased, it exhibited various de-icing states, including refreezing at the trailing edge (pattern III) and ice shedding (pattern IV). The total energy consumption of ice melting decreased as the heat flux increased and the ice melting time shortened. At 5 m/s, when the heat flux was q = 14 kW/m2, the energy consumption at EA at tδ = 1 min, 5 min, and 7 min were 0.33 kJ, 0.55 kJ, and 0.61 kJ, respectively. At 10 m/s, when the heat flux was q = 14 kW/m2, the energy consumption at EA at tδ = 1 min, 3 min, and 5 min were 0.77 kJ, 0.81 kJ, and 0.80 kJ, respectively. Excessive heat flow density increased the risk of the return water freezing; thus, the reference de-icing heat fluxes of 5 m/s and 10 m/s were 10 kW/m2 and 12 kW/m2, respectively. This paper provides an effective reference for wind turbine de-icing.

Fuel integrity evaluation for the shutdown BWR-4 plant during LOCA event

Two BWR units in the Chinshan stopped operation since 2017. However, the spent fuel assemblies still reside in the reactor core, and the plant staffs defined this configuration as the Mode 5 condition. If a Loss-of-Coolant Accident (LOCA) occurs in this condition, the water level will drop and then maintain at approximately 2/3 of the height of the reactor core. The upper 1/3 of the fuel will be exposed to air, and then the fuel cladding temperature will increase significantly. This study use RELAP5 to investigate the effect of different Emergency Core Cooling System (ECCS) to mitigate the LOCA. It is found that the core spray (CS) system can sufficiently suppress the fuel temperature. However, the temperature increase of the uncovered fuel becomes larger if the low pressure coolant injection (LPCI) system which does not provide direct core injection is operable. Based on the results, the peak cladding temperature of both cases are still below the acceptance criteria of 600 °C.

Numerical study on heat transfer characteristics of spray cooling double skin façade

Using spray cooling technology to solve the overheating issue in double skin façade (DSF) is an important attempt to reduce building energy consumption. While, the thermal performance of the spray cooling double skin façade (SC-DSF) is not very clear, especially the complicated heat transfer characteristics. In this study, a comprehensive numerical model of SC-DSF system including solar radiation and two-phase flow problem is established by using three-dimensional steady Euler-Lagrange method to analyze the heat transfer characteristics from a microscopic perspective. And the CFD model is validated by the experiment. Meanwhile, a quantitative analysis is conducted to investigate the thermodynamic and kinetic behavior of the SC-DSF in hot humid climate region in China. The influences of outdoor air relative humidity, solar radiation intensity, and outdoor wind speed on the water spray cooling effect of the DSF are analyzed. The cooling efficiency of SC-DSF system is sensitive to the outdoor relative humidity. In a sufficiently cooled condition, the minimum temperature in the cavity is close to the outdoor wet-bulb temperature. The spray cooling efficiency reaches 28.2 % with the outdoor relative humidity of 20 %, but decreases to only 9.3 % as relative humidity rises to 80 %. Outdoor wind speed also has some impact on the spray cooling system, an optimal outdoor wind speed of 1.5 m/s can enhance cooling efficiency by 6.6 %, but it has adverse effect on the cooling efficiency when wind speed exceeds 3 m/s. However, in addition to increasing surface temperature of the DSF, solar radiation has little influence on the cooling performance. Excessive humidity exceeding 80 % and wind speed surpassing 3 m/s may render the spray system ineffective. Therefore, the effects of environmental conditions should be fully considered and utilized in the design and application of spray cooling systems.

Research on a UAV spray system combined with grid atomized droplets.

UAVs for crop protection hold significant potential for application in mountainous orchard areas in China. However, certain issues pertaining to UAV spraying need to be addressed for further technological advancement, aimed at enhancing crop protection efficiency and reducing pesticide usage. These challenges include the potential for droplet drift, limited capacity for pesticide solution. Consequently, efforts are required to overcome these limitations and optimize UAV spraying technology. In order to balance high deposition and low drift in plant protection UAV spraying, this study proposes a plant protection UAV spraying method. In order to study the operational effects of this spraying method, this study conducted a UAV spray and grid impact test to investigate the effects of different operational parameters on droplet deposition and drift. Meanwhile, a spray model was constructed using machine learning techniques to predict the spraying effect of this method. This study investigated the droplet deposition rate and downwind drift rate on three types of citrus trees: traditional densely planted trees, dwarf trees, and hedged trees, considering different particle sizes and UAV flight altitudes. Analyzing the effect of increasing the grid on droplet coverage and deposition density for different tree forms. The findings demonstrated a significantly improved droplet deposition rate on dwarf and hedged citrus trees compared to traditional densely planted trees and adopting a fixed-height grid increased droplet coverage and deposition density for both the densely planted and trellised citrus trees, but had the opposite effect on dwarfed citrus trees. When using the grid system. Among the factors examined, the height of the sampling point exhibited the greatest influence on the droplet deposition rate, whereas UAV flight height and droplet particle size had no significant impact. The distance in relation to wind direction had the most substantial effect on droplet drift rate. In terms of predicting droplet drift rate, the BP neural network performed inadequately with a coefficient of determination of 0.88. Conversely, REGRESS, ELM, and RBFNN yielded similar and notably superior results with a coefficient of determination greater than 0.95. Notably, ELM demonstrated the smallest root mean square error.

Investigation of aerosol generation through laser cleaning of various surfaces and optimization of mist & spray scavenging

To ensure the safe and effective decommissioning of the Fukushima Daiichi Nuclear Power Plant (NPP), it is crucial to investigate the behavior of radioactive aerosols generated during the laser decontamination of radiation hot spots and laser cutting of fuel debris. Understanding the generation and dispersion patterns of these aerosols is of utmost importance for the proper planning and execution of decommissioning activities. This study focuses on the performance evaluation of high-power continuous wave (CW) fiber lasers for cleaning surfaces composed of carbon steel, stainless steel, and concrete. The effective confinement and scavenging of radioactive aerosols are critical in minimizing the risk of radiation exposure during decommissioning processes. Test samples, made of carbon steel (CS), stainless steel (SS), and concrete, coated with ZrO2, CeO2, and CsI, were subjected to laser decontamination using a class-4 fiber laser within the UTARTS (University of Tokyo Aerosol Removal Test with Sprays) facility. The aerosol particles generated during the laser decontamination process were confined and captured utilizing a spray and mist system. The study proposes the utilization of a combined spray and mist technique, which has demonstrated high efficiency in scavenging aerosols generated through laser irradiation. This research contributes to the broader goal of promoting best practices and innovative solutions in the field of nuclear decommissioning, thereby safeguarding the environment and human health.

Experimental investigation on the performance of compressed air energy storage using spray-based heat transfer

Near-isothermal compression and expansion may be accomplished by injecting water droplets into the air during the process to increase the overall efficiency. However, little is known about the relationship between spray system parameters and compressed air energy storage (CAES). Furthermore, the experiments about compressed air energy storage using spray-based heat transfer have not been investigated. The aim of this paper is to study the relationship between the performance of CAES and the spray system parameters by experimentally. The parameters including the spray closing time, the spray opening time, and the nozzle diameter are discussed. Results show that under the same operating conditions, the maximum air pressure in compression chamber reach to constant value when the spray closing time is 0.6 s; and spraying water mist within 0.6-1.2 s has no heat exchange effect on the air in the cylinder. During the compression process, the smaller the nozzle diameter is, the higher maximum pressure in compression chamber is. During the expansion process, if we ignore the energy consumption of spray system, the larger the nozzle diameter is, the more the expansion output is. Further investigation is recommended to optimize spray parameters based on different CAES systems.

An intelligent spraying system for weeds in wheat fields based on a dynamic model of droplets impacting wheat leaves.

Targeted herbicide application refers to precise application of herbicides in weed-infested areas according to the location and density of farmland weeds. At present, targeted herbicide application in wheat fields generally faces problems including the low herbicide adhesion rate, leading to omission and excessive loss of herbicides. To solve these problems, changes in the impact force of herbicide and the weed leaves in the operation process of a spraying system were studied from the interaction between weeds and herbicides applied. A dynamic model of weed leaves was established. On this basis, the research indicated that the herbicide adhesion rate is highest under spraying pressure of 0.4 MPa and flow rate of 0.011 kg/s when the spray height is 300 mm. To study the dynamic deformation of weed leaves and the distribution of liquid herbicides in the external flow field under weed-herbicide interaction, a dynamic simulation model of herbicide application was built using the finite element method. The results show that when the spray height is 300 mm, the maximum weed leaf deformation index (LDI) is 0.43 and the velocity in the external flow field is 0 m/s under spraying pressure of 0.4 MPa and flow rate of 0.011 kg/s. This finding indicates that the herbicide is not splashed elsewhere and the turbulence intensity in the weed area is 2%, implying steady flow of the herbicide, most of which can be retained on weed leaves. Field test results of application quality of the herbicide show that the maximum LDI is 0.41 and the coverage of the herbicide in the sheltered area below the leaves is 19.02% when the spraying pressure is 0.4 MPa, flow rate is 0.011 kg/s, and spray height is 300 mm. This solves the problem of a low rate of utilization of herbicides because the herbicide passes through weed plants, and achieves the precision herbicide application in wheat fields.

Preface: ILASS-Europe Conference 2023

This special issue of our journal compiles extended versions of selected papers presented at the 32nd European Conference on Atomization and Spray Systems, which was held in Napoli (Italy), in the School of Engineering of the University "Federico II", from 4 to 7 of September 2023.

Ambient catalyst-free oxidation reactions of aromatic amines using water radical cations.

Water radical cations play a pivotal role in various scientific and industrial fields due to their unique reactivity and capacity to drive complex chemical transformations. Here we explored the formation of quaternary ammonium cations through the direct oxidation reaction of aromatic amines, facilitated by water radical cations within water microdroplets. This process was monitored via in situ mass spectrometry and occurs under ambient conditions, negating the need for traditional chemical catalysts or oxidants and achieving an impressive yield of approximately 80%. Additionally, we employed a multi-channel spray system and enhanced both the reactant concentration and flow rate, thereby enabling gram-scale synthesis. These findings not only demonstrate the effectiveness and eco-friendliness of microdroplet chemistry but also provide a new understanding of heterogeneous ˙OH generation channels, thereby boosting the synthetic efficiency and sustainability of chemical processes.

Study on the influence of airflow disturbance on spray atomization

The droplet distribution characteristics are one of the key factors that determine the dust suppression effect of spray system. In order to study the droplet distribution characteristics under different working conditions, the influence mechanism of wind speed and spray angle on droplet distribution characteristics was studied based on Fluent software. The results show that the increase of wind speed and spray angle will increase the lateral momentum of droplets, resulting in the increase of longitudinal height and lateral length of spray belt. The change of spray angle causes the change of the distribution ratio of transverse momentum and longitudinal momentum of droplets. With the increase of spray angle, the transverse momentum of droplets increases and the longitudinal momentum decreases, resulting in the increase of the longitudinal height and length of spray belt. In engineering practice, attention should be paid to the coordinated control of nozzle height, spray angle and airflow speed.

Design and development of a small-scale cement-based 3D printing robot extrusion nozzle

Additive manufacturing (AM), also known as three-dimensional (3D) printing, offers great potential to create complex structures layer by layer from computer-aided design (CAD) models. Despite advancements in printable concrete technology, controlling printing quality remains a challenge associated with both the geometric and materials design of the printer nozzle, especially for small-scale printing that may be required by small and medium-sized enterprises (SMEs). Therefore, this study explored the design and development of a robot nozzle system, optimised for a small-scale 3D printing of cement-based structures. Key design considerations included weight, nozzle diameter/shape, material compatibility, flow control, mixing mechanism, temperature resistance, cost-effectiveness, adaptability, safety, and ease of maintenance. Iterative designs were developed, focusing on stress concentration mitigation and material flow optimisation. The challenge of incorporating mixing mechanisms during nozzle designs was discussed, leading to the adoption of an on-demand accelerator spraying system. This method involved a micro-peristaltic pump connected to an accelerator tank, spraying accelerator onto the surface of the deposited material, as the robot moved along its programmed path. Evidently, both the nozzle design and the spraying approach improved the buildability and print quality of the extrusion-based 3D-printed cement-based structures.

PHYSICAL AND MECHANICAL PROPERTIES AND OPERATIONAL CHARACTERISTICS OF CORONA SPRAYED POWDER COATINGS

This article presents the results from an examination of the physical and mechanical properties of powder coatings based on different binding agents, including epoxy, epoxy-polyester, polyester, polyurethane, and silicone. The coatings that showed the highest results in all tests are epoxy, epoxy-polyester, and polyester. The study investigated the thickness and uniformity of coatings achieved under different spraying conditions. Specific spraying system modes were identified to achieve uniform coatings with predetermined thicknesses. The research highlights the potential application of powder coatings as protective and matching layers for ultrasonic sensors.

Field Study to Assess UASS Mosquito Adulticiding: Methods and Data

Highlights Mosquito adulticiding over operationally relevant areas is feasible using UASS. Wind speed plays an important role in the spray landing position, as expected based on previous studies using CASA. Results are based on both passive and active collectors, including flat cards, rotary impingers, and bottle brushes. Over 1900 total samples were collected in 8 trials, and elevated samplers allowed analysis of the descent of the droplet cloud. Abstract. A spatially extensive experiment was designed to evaluate the effectiveness of Uncrewed Aerial Spray Systems (UASS) in mosquito adulticiding. The practice of adulticiding uses very fine droplets (DV0.5 <50µm). The objective is to fill a volume of air with fine droplets that a flying adult mosquito will encounter in flight. A field program was designed with samplers as far as 500 m downwind from the UASS flight line. A total of over 1900 samples were collected over the course of eight trials. Both passive and active collectors were deployed. Tests were conducted in the early morning and were generally successful in terms of meteorological conditions and data collection. Elevated samplers successfully tracked the descent of the spray cloud, and spray was collected from the most distant samplers. The known dependence of spray movement on wind speed that has been widely observed and codified into label language for Crewed Aerial Spray Aircraft (CASA) was observed. Very low wind speed conditions are problematic for adulticiding in general, and undesirable near-field deposition of adulticiding spray was observed in the data presented here under low wind speed conditions. It needs to be emphasized that much more data needs to be collected before statistically robust conclusions can be drawn. Generally, these data show that UASS can be used to disperse very fine spray droplets over areas representative of operational adulticiding. This paper presents and discusses spray movement and deposition, a second paper is in preparation comparing these data to existing models of spray dispersion and deposition from UASS spraying. A third paper examining mortality from UASS adulticiding has been published. Keywords: Adulticiding, Pesticide drift, UASS Spraying, UAV.

A Novel Trichogramma ostriniae Release System to Control Ostrinia nubilalis in Sweet Corn

HighlightsA first novel injection system was built for spraying Trichogramma at a large scale in sweet corn fields.A mechanical mixer was designed for a rapid dissolution of xanthan and guar gums.The injection system achieved a Trichogramma emergence rate efficiency of 83%.Hose drops addition resulted in an extra 44% spraying coverage underneath sweet corn leaves.Abstract. In sweet corn processing sector, the use of Trichogramma for controlling Ostrinia nubilalis is uncommon in fields, primarily due to the absence of efficient mechanical deployment tools. The poor dissolution of xanthan and guar gums and the medium released along with Trichogramma also impedes the deployment of this biocontrol method. Thus, the preparation of the spraying solution and its application needed to be optimized to be feasible and profitable at a large scale. This work aimed to spray Trichogramma pupae by creating a novel tool: a specific mechanical mixer designed for the rapid dissolution of gums and a modular injection system containing a mixture of Trichogramma pupae and gum formulation to improve the Trichogramma spraying efficiency. Trichogramma emergence rate and concentration were assessed. Results showed that this spraying system greatly facilitated the release of Trichogramma ostriniae and the dissolution of xanthan and guar gums. Specifically, a 4-blade serrated dispersion disk dissolved 16 L at 12 g/L of gum in less than 6 minutes. The injection system successfully distributed pupae through both sides of the sprayer boom with an overall emergence rate efficacy of 83%. Also, an additional 44% of spraying coverage was achieved by spraying under sweet corn leaves using hose drops. Combined with the easy installation on any commercial sprayer, this modular injection system represents a promising pest control tool in organic and conventional crops. Keywords: Injection, Mechanized release, Ostrinia nubilalis, Spraying, Sweet corn, Trichogramma.

Spray Drift, Operator Exposure, Crop Residue and Efficacy: Early Indications for Equivalency of Uncrewed Aerial Spray Systems with Conventional Application Techniques

Highlights Initial data shows UASS spray drift is greater than ground, less than aerial, and similar to an airblast application. Operator exposure with UASS is less than that of a backpack sprayer. No current data shows that residues on crops from UASS applications would be different than conventional applications. UASS applications generally have similar efficacy as their conventional counterparts. Abstract. Uncrewed Aerial Spray Systems (UASS) are being adopted at a rapid pace in agricultural applications of crop protection products. The data required to effectively regulate their use must be gathered to position UASS in terms of equivalency with other conventional practices. In Fall 2021, the CropLife America Drones Working Group initiated an effort to collect published information on establishing the equivalency of UASS applications with conventional application types as it relates to spray drift, operator exposure, crop residue, and efficacy. Based on the published literature, our comparison demonstrated that UASS spray drift is lower than aerial, higher than ground boom, and similar to orchard airblast applications. However, this comparison is based on limited data and needs further confirmation. Individual use cases and other application variables will need to be considered to determine if this generalization applies (e.g., adjuvant use, rotor and nozzle configuration, etc.). For operator exposure, this work supported the current consensus that applications with UASS have less potential for exposure in some respects (e.g., compared to backpack applications), but for other job steps that are unique to UASS (such as mixing and loading) more information is needed. With respect to crop residue, UASS applicators follow the label for conventional application techniques with the same directions for use (i.e., application rate, pre-harvest interval, and number of applications), but there is no evidence that pesticide residues resulting from a UASS application are any different to conventional application techniques. In terms of efficacy, applications with UASS tend to be equivalent to conventional methods; however, more information is needed, especially where good coverage is a requirement. The assessment of published literature on UASS demonstrates potential equivalency in certain key areas and supports the responsible use of this emerging technology, while more information on spray distribution within the target zone, off-target droplet movement, operator and bystander exposure, and pesticidal efficacy continues to be generated. Keywords: Drone, Efficacy, Emerging technology, Operator exposure, Pesticide, Residue, Spray drift, UASS.

Application of REPAS to analyze the sump clogging issue following a LOCA and its impact on the reliability of the ECCS long-term core cooling function

Sump clogging has been identified as a relevant issue after an accident occurred in the Barsebäck-2 nuclear power plant in Sweden (1992). Following a steam line Loss of Coolant Accident (LOCA) due to the inadvertent opening of a safety relief valve, the jet stripped some insulation material from nearby pipes. The insulation debris were transported to the inlet of the strainers for the drywell spray system, thus clogging the intake. The accident was not serious but showed that the Emergency Core Cooling System (ECCS) could have failed. As a consequence, several actions have been undertaken by international organizations, regulatory bodies and nuclear power plant owners to characterize this issue, and propose solutions and improvements. In the present paper, the Reliability Evaluation of Passive Safety Systems (REPAS) methodology is applied to analyze the sump clogging issue and its effect on the long-term core cooling function. Originally developed to evaluate the reliability of passive systems, REPAS is here applied for the first time to an active system. The application is performed using the TRAC/RELAP Advanced Computational Engine (TRACE) code, developed by the USNRC, to simulate a generic three-loop PWR, with an active decay heat removal system.