Search Results (496)

Vector-borne diseases remain a public health concern, and ultra-low-volume (ULV) systems generate adulticide droplets that must remain airborne long enough to contact flying mosquitoes. Accurate droplet and aerosol size characterization is essential for equipment calibration, interpretation of efficacy studies, and evaluation of the airborne fraction relevant to spray transport. This study evaluated complementary nozzle-level and downstream airborne measurements under controlled chamber conditions using a DC-IV droplet counter, TSI APS 3321, and GRIMM MiniWRAS 1.371. Mineral oil and kerosene were atomized at 1.0 to 10.5 bar and 0.20 to 1.00 mL/min. Mass median diameter (MMD), count median diameter (CMD), regression relationships, and size distributions were evaluated. Four MMD calculation methods were also assessed, including Hatch–Choate conversion and a Volume-Based method. For mineral oil, DC-IV reported a mean MMD of 30.78 µm, compared with 4.88 µm for APS and 3.15 µm for MiniWRAS. For kerosene, differences narrowed to 6.21, 6.45, and 4.09 µm, respectively. Hatch–Choate estimates were unstable when lognormal assumptions were violated, whereas the Volume-Based method reproduced reported APS and MiniWRAS MMD values within ±1%. These findings support continued DC-IV use for nozzle calibration and indicate that APS and MiniWRAS can provide complementary real-time characterization of the downstream airborne spray aerosols. Full article

Hydraulic nozzles are widely utilized for dust removal, cooling, and waste heat recovery in mining production. Nevertheless, the influence of co-flow disturbance on the atomization characteristics within the downstream region of droplet fields remains inadequately understood. In this study, three typical hydraulic nozzles were selected, and the atomization characteristics of the downstream region under different co-flow disturbance intensities were experimentally investigated. The results reveal that increasing co-flow disturbance velocity does not intensify the reduction in sauter mean diameter (SMD), but markedly reduces the dispersed phase fraction (DPF). Under four co-flow disturbance velocities (1.5, 3.0, 4.5, and 6.0 m/s), the relative reduction rates of mean SMD are 6.77%, 3.27%, 4.42% and 2.60%, while those of mean DPF are 13.86%, 35.85%, 52.88%, and 61.86% (e.g., hollow-cone nozzle), respectively. The variation in SMD is achieved through the redistribution of cumulative volume among CV₁, CV₂, CV₃, and CV₄. As the velocity increases from 0 to 3 m/s, the mean SMD of the three hydraulic nozzles exhibits a decreasing trend, which can be directly attributed to the continuous increase in the total cumulative volume of CV₁ and CV₂, and the continuous decrease in those of CV₃ and CV₄. For the hollow-cone and solid square-cone nozzles, the SMD first decreases and then increases, with the turning point occurring at 3.0 m/s, consistent with the variation trend of cumulative volume fractions. In contrast, for the solid-cone nozzle, the SMD continues to decrease at velocities exceeding 3.0 m/s. This work provides both a fundamental understanding of atomization characteristics in the downstream region of hydraulic nozzles under co-flow disturbance and practical guidance for velocity control in mine spray systems. Full article

Andrographolide-loaded microparticles with an aqueous-based carrier system were developed with the aim of pulmonary drug delivery. Five formulations of andrographolide (0.6–5.8% w/w) loaded on mixed-polymer carriers containing chitosan (CHS), hydroxyethyl cellulose (HEC), Poloxamer 188, and PEG 20,000, with various ratios were produced under various spray-drying parameters: solution viscosity (5–20 cP), atomization air pressure (0.8–1.5 bar) and solution feed rate (3–6 mL/min). The physiochemical properties of the microparticles were strongly affected by carrier composition and atomization air pressure. The optimal formulation: andrographolide 0.6% w/w, CHS 62.2% w/w, HEC 15.5% w/w and Poloxamer 188 21.7% w/w, spray dried using solution viscosity 15 cP, atomization air pressure 1.1 bar and feed rate 3 mL/min, was selected according to its particle sizes (3–5 µm) with rough morphology, encapsulation efficiency (54.47%) and release behaviors (22.31%/h and 89.23% within 4 h). Good physical, chemical, and thermal stabilities under room storage condition (28 ± 2 °C, 50% relative humidity) were also proven. Importantly, it demonstrated potent antiviral activity against Influenza A/H1N1, achieving a 3.3-log₁₀ reduction in viral titer with 99.95% inhibition. Overall, this aqueous-based carrier approach and spray-drying technique offer a stable and effective inhalable formulation for localized treatment of influenza infections. Full article

Facing the stringent demands of ultra-high pressure fuel injection systems on atomization quality and mixing efficiency, non-circular nozzle geometries have shown significant potential. Biodiesel, as a renewable alternative fuel, suffers from poor atomization due to its high viscosity, low volatility, and large surface tension, posing greater challenges for injector design. Among non-circular designs, the equilateral triangular orifice offers distinct advantages in promoting atomization of high-viscosity fuels and inducing jet axis-switching. This study demonstrates that such triangular nozzles under ultra-high pressure conditions exhibit intense turbulent vorticity at the outlet and distinctive cavitation development, which significantly affect the primary breakup of biodiesel. During spray development, a pronounced axis-switching behavior is observed, characterized by alternating spray cone angles between the major and minor axes. This phenomenon intensifies with higher injection pressure but is mitigated by increased ambient backpressure. The comparative analysis quantitatively establishes these macro–micro coupling characteristics over ultra-high injection pressures of 160–200 MPa, using fixed orifice lengths of 1.5 mm across exit cross-sectional areas ranging from 24,942 to 29,272 μm². The axis-switching process is accompanied by vigorous air entrainment, which significantly enlarges the spray projected area, accelerates liquid breakup, and shortens penetration distance, collectively enhancing the mixing rate and uniformity of biodiesel with air. This work systematically investigates the atomization characteristics and axis-switching behavior of equilateral triangular orifices with varying side lengths when injecting biodiesel under ultra-high pressure conditions, providing an effective technical pathway for the active control of spray morphology and atomization enhancement of biodiesel. Full article

During the 9th NASA MISSE (Materials International Space Station Experiment) campaign, a multilayer LDPE-based shield was tested in a low Earth orbit (LEO) environment aboard the International Space Station for the first time, in the wake-facing orientation. The architecture of the multilayer flight sample, 1 inch in diameter, consisted of two external LDPE sheets and two inner layers filled with boron nitride and samarium–cobalt powders. The inner layers were manufactured using an original process based on compression molding of two superimposed LDPE sheets, with the functional filler deposited onto one of them by spray coating. Thanks to the partial filling of the inner layers and their relative positioning, four different shielding configurations were obtained. The sample was exposed to the space environment for approximately 200 days, experiencing the combined effects of vacuum, solar radiation, thermal cycling, and limited atomic oxygen exposure. The results show that the structural integrity of the shield was not affected by its prolonged residence in LEO. The most significant effect observed was the partial oxidation of the external surfaces of the individual layers, particularly the uppermost layer. Full article

Postbiotics, a type of fermented functional food, are attracting attention alongside the more common pro- and prebiotics. The main production stages—fermentation, thermal inactivation, and drying—significantly influence the functional effects of these foods. This study investigated the impact of pH control during the fermentation of oat flour suspension and optimized spray-drying parameters to produce oat-based postbiotic powders. A Lacticaseibacillus paracasei CBA L74 fermented hydrolyzed oat suspension was analyzed at 37 °C for 24 h, with and without pH control. Both pH conditions produced similar bacterial growth (~10⁹ CFU/mL) and lactic acid (~9 g/L). No significant differences were observed in polyphenols, flavonoids, or antioxidant activity, indicating that pH control did not noticeably improve productivity or the phytochemical properties. The best results—57.40% drying yield and 3.9% relative humidity—were achieved when the postbiotic suspension (diluted 1:4 with water) was mixed 1:1 with maltodextrins, and the spray drying process was conducted with 50 L/min air flow, 200 °C, 3.2 bar atomization pressure, and 5 L/min feed flow. These results support the possibility of scaling the production process from laboratory-optimized parameters and represent a first step toward a cost-effective and industrially feasible route for manufacturing stable oat-based postbiotic powders. Full article

Plant protection unmanned aerial vehicles (UAVs) provide an effective approach for spray application in mountain orchards, yet droplet deposition distribution and spray swath stability under complex terrain remain unpredictable. Based on previous findings on asymmetric effective swath width in mountain Nanguo pear orchards, this study investigated the spatial distribution of droplet size under different operational parameters and clarified the formation and displacement mechanisms of the effective swath from a droplet-size perspective. Under unidirectional flat conditions, small droplets (≤100 μm) decreased and then increased across the swath, whereas large droplets (>150 μm) and D_V0.5 showed opposite trends, with larger droplets concentrated in the central region. Similar patterns occurred in mountain conditions, but asymmetry was more pronounced, especially during inter-row flight. Peak D_V0.5 values generally occurred 7–8 m from the flight path. In reciprocating operations, nozzle atomization mainly affected droplet size beneath the UAV. Inter-row flight shifted the effective swath downslope by approximately 3–4 m, whereas treetop-following flight improved swath stability. These findings provide guidance for nozzle selection, flight path optimization, and precision spraying in mountain orchards. Full article

Exhaust piping in diesel engines is subject to severe thermal stress arising from high-temperature, high-pressure gas flows, and spray cooling with atomizing nozzles has become a widely adopted method to safeguard structural reliability. However, at present, the understanding of the spray fragmentation mechanism of two-phase flow under low inlet pressure is still not comprehensive. This study establishes a three-dimensional model of a gas–liquid impinging-jet nozzle and applies a coupled Volume-of-Fluid to Discrete-Phase-Model (VOF–DPM) approach to resolve the liquid breakup process in detail. High-speed imaging experiments were carried out to validate the numerical results. Orthogonal tests were conducted at five pressure levels for both gas and water—0.28, 0.24, 0.20, 0.16, and 0.12 MPa—producing 25 data pairs of spray cone angle and Sauter Mean Diameter (SMD). Within the 0–0.3 MPa air inlet pressure range explored here, raising the pressure consistently reduced the SMD and widened the cone angle, although both trends weakened as the pressure increased. Water inlet pressure exhibited a nonlinear influence, with local extrema appearing in the higher-pressure region. The overall SMD reached a minimum of 34.12 μm and a maximum of 149.04 μm. Using these 25 data points, a genetic algorithm was employed to optimize the pressure ratio under the constraint of total hydraulic power, yielding optimization strategies for different power budgets. An additional outcome of the simulation was the identification of a structural weakness: by reshaping the original flat impingement surface into a full conical surface, atomization quality improved by 29.36% under identical boundary conditions. These findings clarify the atomization mechanism of gas–liquid impinging jets under low inlet pressure and offer practical guidance for nozzle optimization. Full article

Reported herein is tantalum (Ta)-based film, including TaN, TaO_x, composite TaO_xN_γ, multilayered TaN/TaO_x-(5:5) and TaN/TaO_x-(10:10), prepared by atomic layer deposition (ALD) technology via adjusting the sub-cycle of TaN and TaO_x films. The influence of different growth parameters on microstructure, crystal form, chemical bonding state and corrosion resistance of Ta-based films was systematically investigated. Representative results include the following: (1) The surface of the Ta-based films prepared by ALD is continuous, dense and smooth, and the root mean square roughness (Rq) of those are TaN: 0.74 nm, TaO_x: 0.69 nm, TaO_xN_γ: 0.55 nm, TaN/TaO_x-5:5: 0.56 nm and TaN/TaO_x-10:10: 0.77 nm. (2) The TaN film presents a polycrystalline structure with good crystallinity, while the incorporation of oxygen significantly inhibits the crystallinity of the film. (3) Electrochemical tests in 3.5 wt.% NaCl solution and neutral salt spray experiments show that ALD deposition of Ta-based films can significantly improve the corrosion resistance of carbon steel substrates. The order of corrosion resistance of different films is TaO_xN_γ film > TaN/TaO_x multilayer film > TaN film. Among them, the TaO_xN_γ film exhibited the most excellent corrosion resistance, with a charge transfer resistance (R_ct) as high as 24.75 Ω·cm² and a corrosion current density (I_corr) as low as 1.20 × 10⁻⁶ A/cm², and no obvious rusting phenomenon was observed on the surface of that film after the 2 h neutral salt spray test. Full article

Efficient capture of respirable dust remains difficult in fully mechanized excavation roadways because fine particles readily migrate with airflow beyond the effective spray region. Here, a wind-assisted negative-pressure dust suppression device was developed by integrating annular Venturi entrainment with a mechanical air duct, enabling coupled airflow induction and droplet transport. The device was optimized using nozzle atomization tests, CFD-based orthogonal simulations, and laboratory-scale validation. The results show that an SK508 solid-cone nozzle provides suitable atomization for Venturi-induced suction. Using induced air inlet velocity and diffuser-inlet static pressure as evaluation indicators, the optimal Venturi unit was obtained at 0.1 MPa water pressure, 0.4 MPa air pressure, a 15° diffuser angle, and a throat-center nozzle position. For the integrated device, the best configuration was ten Venturi tubes, an impeller rotational speed of 2400 r/min, and an impeller position of 300 mm from the air duct inlet. In laboratory-scale tests, the complete wind-assisted negative-pressure mode outperformed fan-only, spray-only, wind-assisted spray, and negative-pressure secondary dust suppression modes, achieving maximum total and respirable dust suppression efficiencies of 87.39% and 86.68%. The results demonstrate the feasibility of coupling mechanical airflow with Venturi entrainment and support subsequent field-scale validation. Full article

We present a unified GPU-accelerated framework for real-time Smoothed Particle Hydrodynamics (SPH) fluid simulation with two-way rigid body coupling, secondary particle effects, and volumetric rendering, implemented entirely within the Unity game engine. The framework employs a weakly compressible SPH formulation with O(n) count sort-based spatial hashing and introduces a signed distance field (SDF) coupling system that evaluates three representative geometric primitives, sphere, cylinder, and torus, of increasing topological complexity directly on the GPU. Bidirectional force exchange is achieved through lock-free atomic compare-and-swap impulse accumulation, enabling thousands of fluid particles to interact simultaneously with each rigid body without serialization. A GPU stream compaction–based secondary particle system generates and classifies foam, spray, and bubble effects in real time, while a volumetric rendering pipeline samples fluid density into a 3D texture for SDF-composited volume rendering without surface mesh extraction. A conditional kernel dispatch strategy eliminates GPU cycles for disabled subsystems, and dynamic buffer management reduces memory pressure through runtime allocation. The system sustains above 54 frames per second at four million particles on a consumer-grade GPU, with sub-linear frame time scaling and a 1.70× speedup from dynamic buffer allocation over static pre-allocation. Full article

This study aims to demonstrate the feasibility of controlling particle size through a mathematical model in the design of industrially applicable ultrasonic spray nozzles by utilizing the vibrational characteristics of piezoelectric ceramics. A piezoelectric ceramic composition with a low sintering temperature and excellent thermal stability (Curie temperature above 300 °C) was developed and used as a ceramic vibrator. Furthermore, the resonance frequency and nozzle displacement were calculated using the COMSOL program and applied to a mathematical model to design an ultrasonic nozzle capable of producing a spray particle diameter of approximately 30 μm. The designed ultrasonic nozzle was fabricated, and its spray characteristics were analyzed. The consistency of the spray characteristics was examined by comparing them with the mathematical model based on changes in ultrasonic nozzle length, resonance frequency, and fluid viscosity. When the ultrasonic nozzle horn length was 22 mm, the resonance frequency was found to be 42.1 kHz, and at a flow rate of 65 mL/min. the average spray particle size was approximately 30–40 μm, indicating fine and uniform particles. In addition, it can be seen that as the length of the nozzle horn increases, the resonance frequency decreases, reducing the supply energy delivered to the liquid, and the particle size increases as shown in the mathematical analysis. The theoretical separation energy required to atomize pure water at a flow rate of 65 mL/min. is 2100 J, which was found to be greater than all energy loss occurring during the atomization process. However, it can be seen that as the length of the ultrasonic nozzle increases, the maximum atomization volume increases, and as viscosity increases, the energy required to separate a single atomized particle becomes greater. Full article

Atmospheric sea spray aerosol (SSA) undergoes chemical aging during long-distance transport, leading to significant alterations in its climate effects. However, the aging mechanisms of SSA driven by oxygenated volatile organic compounds (OVOCs) remain unclear. Hence, the aging processes of NaCl particles driven by glyoxal (GL), a representative OVOC, are systematically investigated using molecular dynamics (MD) simulations and density functional theory (DFT) calculations. MD simulations with high GL coverage show that GL readily mixes with NaCl and preferentially orients its carbonyl groups toward the NaCl surface. The adsorption of GL on the NaCl surface is dominated by the interaction between the O atom of GL (O_GL) and the Na atom of the surface. DFT calculations with single GL coverage further reveal the formation of the O_GL–Na bond between GL and NaCl. The mixing process of GL and NaCl is regulated by both the number of aldehyde groups engaging in the interfacial coordination and the corresponding lengths of O_GL–Na bonds. The subsequent heterogeneous oxidation of GL by an OH radical proceeds mainly via a barrierless H-abstraction pathway to form HC(O)CO radicals, which may further react with methylamine/ammonia and contribute to brown carbon formation. Our results reveal the importance of incorporating such aging mechanisms into atmospheric models to improve climate predictions. Full article

Liquid rocket engine injectors play a fundamental role in determining combustion efficiency, stability, and overall propulsion performance. This review paper provides a comprehensive analysis of liquid-injector technologies used in space propulsion systems, with emphasis on their historical evolution, atomization mechanisms, and cross-domain insights from aviation fuel injection systems. The study begins by examining the fundamental processes governing liquid jet breakup, including primary and secondary atomization, ligament formation, and droplet generation, together with the non-dimensional parameters that control these phenomena. The historical development of injector architectures -from early orifice-based and impinging designs to modern coaxial and pintle configurations—is then discussed in relation to increasing performance requirements and combustion stability challenges. A comparative perspective with aviation gas turbine injectors is introduced to highlight similarities in atomization physics and differences in operating conditions and design constraints. The paper also reviews experimental and numerical approaches used to characterize spray formation and injector performance. The results indicate that injector geometry and flow conditions strongly influence mixing efficiency, droplet size distribution, and combustion–acoustic coupling mechanisms. The study concludes that integrating cross-domain knowledge and modern design techniques is essential for advancing injector performance in next-generation propulsion systems. Full article

High-pressure airless spray coating can atomize high-viscosity, high-solids coatings without compressed air and is widely used for large-scale anticorrosion applications, but robotic operation often produces substantial overspray that increases material waste, environmental burden, and lowers deposition efficiency. In this work, air-curtain blowing is investigated as an overspray control strategy for wall-climbing robotic airless spraying. A validated CFD framework was established using the realizable k–ε turbulence model coupled with a discrete-phase model (DPM) to simulate particle atomization, transport, impact, and escape, and to examine the effects of blowing angle and gap distance on the flow field and particle trajectories. Overspray performance was quantified using the wall deposition rate, hood collection rate, and particle escape rate. Experiments using a transparent spray hood with a mass collection system were conducted to validate the numerical predictions. The CFD results captured the measured trends in deposition and escape across the tested conditions. Among the evaluated parameters, a 60° blowing angle provided the most effective overspray reduction by redirecting particles toward the target surface. Overall, combining CFD analysis with experimental validation offers a practical methodology for designing and optimizing air-curtain systems to improve coating efficiency in automated high-pressure airless spray applications. Full article