Rotary Atomizer Research Articles

Spray characteristics of axially-vaned slinger atomizer in air crossflow

Slinger atomizers are frequently employed to facilitate fuel spray atomization in aeroengine combustors. Unlike traditional radial slinger atomizers that induce the limited interaction between the rotating fuel and the surrounding air, this study proposes an innovative approach by incorporating axial vanes into the slinger rotor to potentially enhance fuel atomization performance. A comprehensive analysis of the spray characteristics of an axially-vaned slinger atomizer in air crossflow is numerically conducted, focusing on the effects of axial vane, rotor–stator axial clearance, and fuel inlet conditions. Results demonstrate that axially-vaned slingers outperform radial slingers by enhancing air swirl strength to disrupt the fuel jet, reducing the average droplet size by 25 % at 30000 rpm. Furthermore, positioning fuel nozzles farther from the rotor wall can mitigate the potential risk of surface thermal erosion. Fuel leakage through the rotor–stator clearance decreases from around 80 % at 10000 rpm to below 5 % at 30000 rpm and becomes negligible at 40000 rpm, thereby enhancing fuel–air mixing efficiency. Introducing supercritical fuel at the inlet facilitates its transition into a gaseous state within the slinger inner chamber, thereby markedly amplifying mixing efficiency. Nonetheless, this improvement is accompanied by a reduction in fuel flow rates. A significant aspect to consider is the heightened risk of substantial wall erosion due to pronounced leakage through the rotor–stator axial clearance. This study presents novel perspectives on improving the efficiency and ensuring the operational safety of rotary atomizers, thereby offering valuable guidance for the design of power and propulsion systems.

Commercialization of the Xalkori Pediatric Multiparticulate Product Using Quality-by-Design Principles.

A pediatric dosage form for crizotinib (Xalkori) was commercialized using quality-by-design principles in a material-sparing fashion. The dosage form consists of spherical multiparticulates (microspheres or pellets) that are coated and encapsulated in capsules for opening. The crizotinib (Xalkori)-coated pellet product is approved in the US for pediatric patients 1 year of age and older and young adults with relapsed or refractory, systemic anaplastic large cell lymphoma (ALCL) and unresectable, recurrent, or refractory inflammatory myofibroblastic tumor (IMT) that is ALK-positive. The product is also approved in the US for adult patients with non-small cell lung cancer (NSCLC) who are unable to swallow intact capsules. The lipid multiparticulate is composed of a lipid matrix, a dissolution enhancer, and an active pharmaceutical ingredient (API). The API, which remains crystalline, is embedded within the microsphere at a 60% drug loading in the uncoated lipid multiparticulate to enable dose flexibility. The melt spray congealing technique using a rotary atomizer is used to manufacture the lipid multiparticulate. Following melt spray congealing, a barrier coating is applied via fluid bed coating. Due to their particle size and content uniformity, this dosage form provides the dosing flexibility and swallowability needed for the pediatric population. The required pediatric dose is achieved by opening the capsules and combining doses of different encapsulated dose strengths, followed by administration of the multiparticulates directly to the mouth. The encapsulation process was optimized through equipment modifications and by using a design of experiments approach to understand the operating space. A limited number of development batches produced using commercial-scale equipment were leveraged to design, understand, and verify the manufacturing process space. The quality by design and material-sparing approach taken to design the melt spray congeal and encapsulation manufacturing processes resulted in a pediatric product with exceptional content uniformity (a 95% confidence and 99% probability of passing USP <905> content uniformity testing for future batches).

Experimental study on spray characteristics of aviation kerosene RP-3 in a radial rotary atomizer

Experimental study on spray characteristics of aviation kerosene RP-3 in a radial rotary atomizer

Statistical analysis of rotary atomization by phase Doppler anemometry

Rotary atomization is used in a wide variety of fields, exploiting the external control option of the spray while no high-pressure fluid is needed. Most papers on rotary atomization deal with liquid jet breakup, while external spray characteristics are rarely evaluated; this is performed currently. The water spray was measured by a two-component phase Doppler anemometer. The optical setup requires a special measurement chamber to avoid spray deposition on the optical components. Therefore, the first goal was to find a proper filter that enables the removal of biased droplets by secondary flows. Since most droplets have a similar radial-to-tangential velocity ratio at each measurement point, i.e., scattering around a line, this was the first component of the best filter. The second component was the need for a positive radial velocity component. This filter efficiently removed droplets originating from alternative processes, increasing the R2 of the line fit. The physical soundness of this filter was checked by evaluating the effect of filtering on the angle of the velocity components of each droplet at a given measurement point. The proposed filter efficiently detected recirculation, a secondary effect of the measurement setup with less regular dataset shapes. Finally, the slope and intercept values of the fitted lines were evaluated and presented. The mean of the former followed the same trend irrespective of the rotational speed and the mass flow rate; it was principally dependent on the radial distance from the atomizer. The intercept showed a regular but less universal behavior.

Benefits of ULV Application to Control Locusts in Caucasus and Central Asia

This paper discusses the state-of-the-art of Ultra-Low Volume (ULV) spray application with rotary atomisers in the Caucasus and Central Asian (CCA) region to control locusts. The technology is widely used around the world for locust control and promoted by the UN Food and Agriculture Organisation (FAO) as an effective and efficient control intervention that meets the scale and challenge posed by large area locust outbreaks. The technology utilises precisely controlled spray droplets in the range 50–100um using ready-to-use oil-based ULV formulations to target locusts more efficiently. Volume rates as low as 0.5–1.0 l/ha are utilised which greatly improves productivity of ground and aerial spray applications, timeliness, and reduces cost and waste of pesticide and water. ULV has become more widely adopted in CCA during recent years to control major economic pests such as Moroccan, Italian, and Asian migratory locusts. Its further adoption is hampered by the lack of available ULV formulations in the region and need for investment and training in the technology. ULV technology is highly appropriate for use of biological products to reduce risks to operators and the environment and efforts to increase regional cooperation and the registration of safer pesticides across the region present opportunities for its wider adoption.

Investigating atomization characteristics in an electrostatic rotary bell atomizer

Electrostatic rotary bell atomizers are commonly used in several engineering applications, including the automobile industry. A high-speed rotating nozzle operating in a strong background electric field atomizes paint into charged droplets that range from a few micrometers to tens of micrometers in diameter. The atomization process directly determines the droplet size and droplet charge distributions which subsequently control the transfer efficiency and the surface finish quality. We have previously developed a tool to perform high fidelity simulations of near-bell atomization with electrohydrodynamic effects. In this work, we perform simulations employed with a droplet ancestry extraction tool to analyze previously inaccessible information and understand the physical processes driving atomization. We find that the electric field accelerates breakup processes and enhances secondary atomization. The total number of droplets, the ratio of secondary to primary droplets, and the ratio of coalescence to breakup activity are all much higher when operating in an electric field. We analyze the droplet velocity, local Weber number and charge density statistics to understand the complex physics in electrically assisted breakup. The results of the study have helped us gain insights into the physics of atomization in electrostatic rotary sprays.

Preparation of dense/spherical fine particle by spray dryer

Fine particle granulation using a spray dryer was performed to prepare with a high drug content, a spherical shape, and a smooth surface. Since the target particle size was less than 200 μm, a rotary disk atomizer was adopted and a slurry was chosen as the spray liquid. When 5-aminosalicylic acid used as a model drug, hydroxypropyl cellulose, and sodium chloride were added in the slurry and was spray dried, the desired size of particles were obtained. Then, the obtained particles were coated with an enteric polymer, no dissolution of the drug in the 1st solution was observed, indicating no disruption occurred during coating.

Experimental investigation on liquid breakup regimes and spray characteristics in slinger atomizers with various injection orifices

Slinger atomizers, known as one type of rotary atomizers, have been widely applied in various small gas turbine engines. The fuel can be well atomized by taking advantage of the high rotational speed of the turbine shaft. The geometric characteristics of the injection orifice play an important role in determining the atomization performance of the slingers. The breakup regimes and the droplet size of the slinger atomizers with slot-shaped orifices have rarely reported in the past. Herein, three types of slinger atomizers with different orifice shapes and orifice diameters are tested at rotational speeds of 8000–20 000 rpm and liquid feed rates of 4 up to 20 g/s. High-speed shadowgraph imaging, high-speed digital imaging, and planar Mie technologies are applied to provide the spray breakup process, liquid film injection features, and droplet distribution, respectively. Spray visualizations show that the orifice diameters strongly affect the breakup modes, whereas the orifice shapes have a slight effect. The variation regarding droplet sizing under different heights from the slinger plane is analyzed. The uniformity of the droplet distribution in slot-shaped slinger atomizers is better than that in round-shaped slinger atomizers. Moreover, the smaller orifice diameter results in a small Sauter mean diameter (SMD) for the slinger atomizers with slot-shaped orifices. Finally, a mathematical expression is obtained to predict non-dimensional droplet size (SMD/d) for different slinger atomizers. The present results appear to be the first systematic investigation of the spray characteristics in slinger atomizers with slot-shaped orifices.

A spray painting simulation using high-speed rotary Atomizer—Model development and comparison of LES and RANS—

This study performed a spray-painting simulation based on the Large Eddy Simulation (LES) and Reynolds-Averaged Navier-Stokes (RANS) for spray painting using a rotary atomizer. The LES better reproduced the flow field and spray dispersion between the bell and target than the RANS. Also, the region called “over-spray” in the radially outside of the bell, in which the droplets stay, was formed, and the residence time became longer for droplets with larger diameter regardless of numerical methods for turbulent flow. Further, the transfer efficiency (TE) in the RANS was almost constant, independent of droplet diameter because all the eddy was modeled in the RANS, and the turbulent fluctuation a droplet received near the target was isotropic. In contrast, the TE in the LES varied depending on droplet diameter and showed the maximum value because only small eddies are modeled in the LES, and the turbulent fluctuation was more realistic.

Uncrewed Aerial Spray Systems For Mosquito Control: Efficacy Studies For Space Sprays.

Achieving an appropriate droplet size distribution for adulticiding has proved problematic for unmanned aerial spray systems (UASSs). The high-pressure pumping systems utilized on crewed aircraft conflict with the weight constraints of UASSs. The alternative is a lightweight rotary atomizer, which when run at a maximum rpm with a minimal flow rate can achieve the appropriate droplet size distribution. For this study a UASS was calibrated to discharge an appropriate droplet size distribution (Dv0.5 of 48 µm and Dv0.9 of 76 µm). Spray was released from an altitude of 23 m (75 ft). The spray plume was shown to effectively disperse through the sampling zone. To achieve the appropriate application rate, the flight speed was 3 m/sec (6.7 mph) with an assumed swath of 150 m (500 ft). The objective of this project was not to conduct an operational application; instead only 1 flight line was used so that the effective swath width could be confirmed and the appropriate flightline separation defined. This study showed that control was achieved across distances of 100-150 m. Considering a swath width of 150 m (500 ft), ground deposition was 13-36% of applied material. Spray deposition corresponded well with the mortality data, which helped improve confidence in the data. The overall conclusion from this study is that aerial adulticiding is feasible with the system presented here. Further work is required to improve the atomization system to allow operational flight speeds and to determine the interaction between release altitude and droplet size in order to minimize ground deposition of application material.

Morphological characteristics of spray dried cellulose nanofibers produced using various wood pulp feedstocks and their effects on polypropylene composite properties

Bleached Kraft pulp (BKP), unbleached Kraft pulp (UKP), and old corrugated cardboard pulp (OCC) are excellent feedstock sources for producing CNF suspensions manufactured by a mechanical disk refining process. The CNF drying operation should be performed to produce dry powders that can be compounded into thermoplastic matrices, and spray drying is fast, simple, cost-effective, and scalable. Among several spray-drying techniques, the pilot scale-rotary disk atomizer has many advantages, including large capacities, drying efficiency, and less feed blockage. In this study, BKP, UKP, and OCC pulps fibrillated to 90 % and 100 % fines levels were spray-dried using a pilot-scale rotary disk atomizer. The high-quality micrometer scale, round-shaped powders were produced from all feedstock sources, and a smaller particle size powder was produced with the higher fibrillated pulps. The spray-dried cellulose nanofibrils (SDCNFs) were compounded into a polypropylene (PP) matrix as a reinforcing material, and maleic anhydride-grafted polypropylene (MAPP) was used as a coupling agent. A masterbatch was used for the optimal dispersion and distribution of SDCNFs and MAPP in the PP matrix. It was concluded that the tensile and flexural properties increased as the particle size of SDCNFs increased, and the impact strength increased as the particle size decreased. The tensile strength, tensile modulus, flexural strength, flexural modulus, and impact strength increased by up to 29 %, 66 %, 15 %, 27 %, and 11 % respectively, compared to the neat PP after adding 10 wt% of SDCNFs with MAPP to the PP matrix.

UNCREWED AERIAL SPRAY SYSTEMS FOR MOSQUITO CONTROL: EFFICACY STUDIES FOR SPACE SPRAYS.

Achieving an appropriate droplet size distribution for adulticiding has proved problematic for unmanned aerial spray systems (UASSs). The high-pressure pumping systems utilized on crewed aircraft conflict with the weight constraints of UASSs. The alternative is a lightweight rotary atomizer, which when run at a maximum rpm with a minimal flow rate can achieve the appropriate droplet size distribution. For this study a UASS was calibrated to discharge an appropriate droplet size distribution (Dv0.5 of 48 µm and Dv0.9 of 76 µm). Spray was released from an altitude of 23 m (75 ft). The spray plume was shown to effectively disperse through the sampling zone. To achieve the appropriate application rate, the flight speed was 3 m/sec (6.7 mph) with an assumed swath of 150 m (500 ft). The objective of this project was not to conduct an operational application; instead only 1 flight line was used so that the effective swath width could be confirmed and the appropriate flightline separation defined. This study showed that control was achieved across distances of 100-150 m. Considering a swath width of 150 m (500 ft), ground deposition was 13-36% of applied material. Spray deposition corresponded well with the mortality data, which helped improve confidence in the data. The overall conclusion from this study is that aerial adulticiding is feasible with the system presented here. Further work is required to improve the atomization system to allow operational flight speeds and to determine the interaction between release altitude and droplet size in order to minimize ground deposition of application material.

High-fidelity simulations of a rotary bell atomizer with electrohydrodynamic effects

Electrostatic rotary bell atomizers are extensively used as paint applicators in the automobile industry. Paint undergoes atomization after exiting the edge of a high-speed rotating bell. In most setups, the paint is electrically charged and a background electric field is applied between the nozzle and the target surface to increase the transfer efficiency (TE). The atomization process directly determines the droplet size and droplet charge distributions which subsequently control TE and surface finish quality. Optimal spray parameters used in industry are often obtained from expensive trial-and-error methods. In this work, three-dimensional near-bell atomization is computationally simulated using a high-fidelity volume-of-fluid transport scheme that includes electrohydrodynamic (EHD) effects. We find that electrifying the setup results in the production of smaller droplets. Additionally, the electric field has a minor effect on primary atomization but a negligible effect on the size and stability of atomized droplets after secondary breakup. This cost-effective method of simulating EHD-assisted atomization allows for the understanding of the effect of the electric field and the extraction of droplet charge characteristics which is otherwise challenging to obtain experimentally.

Influence of air swirl orientation on the spray characteristics of a micro-channel-based rotary (MCR) atomizer

In this work, we investigate the atomization and spray characteristics of a novel rotary atomizer with micro-channel grooves, using optical diagnostics. Micro-jets emanate from the grooves provided in the rotating injector. The spiraling liquid jets interact with the surrounding high-speed swirling air flow, resulting in the creation of a well-dispersed fine spray. Attention is focused on the effects of air swirler orientation with respect to that of injector rotation. Accordingly, the co- and counter-swirl cases are investigated. The primary jet breakup process is visualized using back-lit illumination technique, which also provides the measurement of jet breakup length. The jet break-up modes are identified for different air swirl strength and orientation and injector rotational speed. The size, number density and velocity components of the spray droplets are measured using PDPA technique at different axial and radial locations. Air velocity is also measured (in the absence of liquid injection) using the LDV technique. In addition, Laser Sheet Imaging (LSI) is employed to investigate the overall spray structure. Results show that the droplet size significantly reduces when air swirl strength or injector rotational speed is increased. Though not much difference is observed in the characteristic droplet size between the co- and counter-swirl cases, the droplet size distribution is narrower and droplet dispersion is improved for the latter. The current findings demonstrate the potential of the rotary injector to dynamically control the spray characteristics as per requirement.

Characterization of TC4 Alloy Powder Prepared by EIGA for Laser 3D Printing

Spherical TC4 alloy powder for laser 3D printing have been prepared by the vacuum rotary electrode gas atomization(EIGA), and the characteristics such as particle size distribution, chemical composition, sphericity, phase, hollow sphere ratio, apparent density and flowability of spherical TC4 alloy powder were studied. The results show that the TC4 alloy powder with ideal characteristics was successfully prepared under the optimized process parameters, the morphology of the powder is mainly spherical and its sphericity reaches 98%, the phase is composed of α′-Ti single solid solution, the main particle size distribution is 1~150 μm, and the hollow sphere rate is 3%. The chemical composition of the TC4 alloy powder meets the requirements of industrial standards and the TC4 alloy powder has low oxygen content of 0.106%.The apparent density of alloy powder with 54~150 µm is 2.648 g/cm3, and the flowability is 25.7 s/50g. The characteristics of the TC4 alloy powder prepared by this EIGA method meet the requirements of laser 3D printing high-quality TC4 alloy.

The effect of wastewater components and operation conditions on selenium release during desulfurization wastewater evaporation: A lab-scale study

Rotary atomization evaporation technology is one of the effective technologies to achieve zero discharge of desulfurization wastewater. However, the migration and transformation mechanism of selenium during desulfurization wastewater evaporation is still unknown, hindering this technology's further application. Therefore, the effects of evaporation temperature, pH, Cl−, S2O2–8, SO2–4and Ca2+ on selenium release during evaporation were investigated in this work. The results showed that elevated temperature promoted the release of selenium, especially in the solid-phase pyrolysis stage. pH affected the release of selenium through influencing its initial species, and the release rate of Se(IV) increased with decreasing pH. The ionic compositions of the solution were also found to be a critical factor in the stability of selenium species during evaporation. Cl− would promote the release of Se(IV), while SO2–4 inhibited the release of selenium species, and Ca2+ had little effect on the final release rate of selenium species release. In addition, it was found that the presence of S2O2–8 would significantly enhance the conversion of Se(IV) to Se(VI) during the evaporation process. The results obtained in this work provided guidelines and suggestions for controlling the selenium release from desulfurization wastewater in power plants.

Influence of Different Liquid Spray Pollination Parameters on Pollen Activity of Fruit Trees—Pear Liquid Spray Pollination as an Example

Liquid spray pollination (LSP) is widely used in fruit tree pollination. However, the LSP parameters that affect the pollen activity are still unclear. In this study, three LSP parameters that mainly affect the pollen activity were studied: storage time of pollen suspensions, sprayer parameters and unmanned aerial vehicle sprayer (UAVS) downwash airflow. In addition, sprayer parameters include the recirculation device, pump type, spraying pressure, nozzle size and revolutions per minute (rpm) of the rotary atomizer (RA). The results showed that, with the exception of nozzle size and UAVS downwash airflow, the pollen activity was significantly influenced by LSP parameters. The mean pollen activity decreased by 20.20% when the pollen suspension was stored for 30 min compared to 0 min. The activity of pollen in the tank was dramatically reduced using the recirculation device. The mean pollen activity decreases as the pump production maximum pressure increases. The mean pollen activity decreased from 40.7% to 29.02% when the spraying pressure increased from 0.3 MPa to 2.5 MPa. Additionally, the mean pollen activity decreased from 44.25% to 14.14% as the rpm of RA increased from 3000 rpm to 14,000 rpm. Our study demonstrated that pollen activity would be ensured by appropriate LSP parameters. This study provides a reliable theoretical basis for optimizing and advancing pear LSP technology.

Experimental and theoretical investigation of rotary atomization dynamics for control of microparticle size during spray congealing process

Experimental and theoretical investigation of rotary atomization dynamics for control of microparticle size during spray congealing process

Computational study of free surface film flow and subsequent disintegration of a sheet and ligaments into droplets from a rotary disk atomizer

In the present study, a computational methodology based on computational fluid dynamics (CFD) is developed to investigate free surface film flow and its subsequent disintegration on a rotary disk atomizer. The present study provides an insight into efficiently modeling both liquid film formation and its subsequent disintegration. The presented computational methodology can easily be reproduced and can act as a benchmark for the modeling of liquid film formation as well as the disintegration phenomenon. The influence of disk speed, liquid flow and feed arrangement on the rotating disk are investigated. The film thickness profile on the disk resembles the formation of spiral waves at 500 RPM and an irregular breakup of the spiral waves for a disk speed of 1000 RPM. At higher speeds, a smooth and thin liquid film is observed on the disk. Offset feeding of the liquid on the disk alters the wave formation and breakup of the spiral waves. It is found that ligaments are formed at the lip of the disk owing to Rayleigh–Taylor instability, whereas liquid sheet breakup is due to combined rim and wave disintegration for the parameters investigated in this study.

Insights from high-fidelity modeling of industrial rotary bell atomization

The global automotive industry sprayed over 2.6 billion liters of paint in 2018, much of which through electrostatic rotary bell atomization, a highly complex process involving the fluid mechanics of rapidly rotating thin films tearing apart into micrometer-thin filaments and droplets. Coating operations account for 65% of the energy usage in a typical automotive assembly plant, representing 10,000s of gigawatt-hours each year in the United States alone. Optimization of these processes would allow for improved robustness, reduced material waste, increased throughput, and significantly reduced energy usage. Here, we introduce a high-fidelity mathematical and algorithmic framework to analyze rotary bell atomization dynamics at industrially relevant conditions. Our approach couples laboratory experiment with the development of robust non-Newtonian fluid models; devises high-order accurate numerical methods to compute the coupled bell, paint, and gas dynamics; and efficiently exploits high-performance supercomputing architectures. These advances have yielded insight into key dynamics, including i) parametric trends in film, sheeting, and filament characteristics as a function of fluid rheology, delivery rates, and bell speed; ii) the impact of nonuniform film thicknesses on atomization performance; and iii) an understanding of spray composition via primary and secondary atomization. These findings result in coating design principles that are poised to improve energy- and cost-efficiency in a wide array of industrial and manufacturing settings.