Investigation of Droplet Size Distribution for Vibrating Mesh Atomizer

Vibrating mesh atomizers (VMA) are increasing in demand for various aerosol applications due to their ability to generate uniformly sized droplets. Currently there are two types of VMA (commercial metallic membranes and silicon based). High Uniformity and control of small droplet size are the basic requirements for many aerosol applications, for which ultrasonic or VMA are employed. However, there is limited research on understanding the droplet size distribution of different types of atomizers. In this study three aerosol generators were investigated: Ultrasonic, metallic VMA, and MEMS-based silicon VMA. The primary objective was to compare these devices on droplet size distribution and mechanism of action. A systematic study to compare the performance of the two VMA was investigated based on droplet distribution, volumetric median diameter (VMD) using liquids with different physiochemical properties. Size distribution of the droplet produced by the metallic VMA was twice the span compared to silicon VMA for fluids with viscosity <2cP. The metallic VMA also resulted in an increase in VMD as the viscosity increased, whereas the Si VMA did not see a significant increase in VMD. The silicon-based VMA demonstrated a 4-15x increase in fine particle fraction control compared to metallic VMA. The results demonstrate that silicon based VMA has narrower droplet distribution with more uniform droplet size and lower span compared to metallic VMA.

Preparation and application of a thidiazuron·diuron ultra-low-volume spray suitable for plant protection unmanned aerial vehicles

Spraying of defoliant can promote centralized defoliation of cotton and advance maturity to facilitate harvesting. Modern pesticide application equipment includes plant protection unmanned aerial vehicles (UAVs), which are used widely for spraying defoliants. However, commonly used defoliant formulations are mainly suspension concentrates and water-dispersible granules, which need to be diluted with water when used. These are not suitable for plant protection UAVs with limited load capacity, especially in arid areas such as Xinjiang, China. Therefore, we prepared a thidiazuron·diuron ultra-low-volume (ULV) spray, which can be used directly without dilution in water. We found that ULV sprays had better wettability than the commercially available suspension concentrate, could quickly wet cotton leaves and spread fully. The volatilization rate was lower. ULV sprays also showed better atomization performance and more uniform droplet distribution than the commercially available suspension concentrate. At a dosage of 4.50–9.00 L/ha, the coverage rate on cotton leaves was 0.85–4.15% and droplet deposition densities were 15.63–42.57 pcs/cm2; defoliation rate and spitting rate were also greater than those of the reference product. This study could be contributed to the development of special pesticide formulations suitable for UAVs.

Antiviral Action of Curcumin Encapsulated in Nanoemulsion against Four Serotypes of Dengue Virus

Background: Curcumin has been used as a traditional medicine showing antiinflammatory, antimicrobial, and antiviral properties. Despite the promising potentials, curcumin-based drug development is hindered due to its poor solubility and cell uptake. Objective: This study aims to produce curcumin nanoemulsion (nanocurcumin) and evaluate its physical characteristics and in vitro cell cytotoxicity and antiviral activity against dengue virus (DENV). Method: Nanocurcumin was generated by self-nanoemulsion technique. Cytotoxicity was determined using MTT assay in A549 cell line. Anti-DENV properties were determined by calculation of inhibitory concentration 50 (IC50) and plaque assay. Results: The resulting nanoemulsion showed uniform droplet size distribution with the average droplet size of 40.85 ± 0.919 nm. Nanocurcumin exhibited higher cell cytotoxicity compared to curcumin solution and may be explained by better cell uptake. Nanocurcumin treatment suppressed DENV growth, although no significant difference observed compared to the curcumin solution counterpart. Greater virus reduction was observed for DENV-1 and DENV-2. Conclusion: The synthesis of nanocurcumin improved curcumin physicochemical properties with potential as antiviral against DENV.

The Emulsifying Properties of Hydrogenated Rosin Xylitol Ester as a Biomass Surfactant for Food: Effect of pH and Salts

The xylitol ester of hydrogenated rosin (XEHR) was obtained for the first time from biomass-based hydrogenated rosin and xylitol using an environmentally friendly, high-pressure CO2 catalytic synthesis. This compound is intended for use as an emulsifier for food. Analyses by ICP-AES showed the absence of heavy metal residues in the product, such that it met food standards. Fourier transform infrared and nuclear magnetic resonance spectroscopies together with gel permeation chromatography confirmed the successful esterification and the formation of a monoester and diester with molar masses of 427 and 772 g/mol. The emulsification of water/soybean oil mixtures by adding the XEHR was assessed at pH values of 4, 6.86, and 10 and in the presence of NaCl, KCl, MgCl2, and CaCl2. The XEHR was found to act as an emulsifier by reducing the interfacial tension of such mixtures to less than 2 mN/m under all conditions. The highest emulsifying activity index (9.52 m2/g) and emulsifying stability index (94.53%) were obtained after adding MgCl2 (100 mM). Particle size and confocal microscopy showed that the presence of salts gave a more uniform droplet size and a finer emulsion structure. The high viscosities of the emulsions containing salts also suggested a more cohesive oil droplet network.

A Numerical Investigation of Air/Mist Cooling in a Conjugate, 3-D Gas Turbine Vane With Internal Passage and External Film Cooling

This paper describes a numerical investigation to study the effect of injecting mist (tiny water droplets, micrometers in size) into the cooling airstream to cool down gas turbine vanes. In this study, the conjugate heat transfer method is employed which consists of the simulation of the air/mist fluid flow inside and outside the vanes as well as the heat conduction through the vane body. The complete 3-D vane with internal cooling passages and external film cooling holes on the surface is simulated in a rotational periodic sector. The discrete phase model (DPM) is used to simulate and track the evaporation and movement of the tiny water droplets. The effects of different parameters such as the mist/air ratio (10–20%) and the mist droplets size (20–50μm) on mist cooling enhancement are investigated. The results show that by using a mist/air ratio of 10%, 15%, and 20% with 20 μm droplets size, on the pressure side, a maximum wall temperature reduction of 250 K, 340 K, and 450 K respectively can be achieved. On the suction side, the corresponding maximum wall temperature reductions are 160 K, 260 K, and 360 K, respectively. Using larger droplets of 50μm did not achieve better cooling enhancement because the droplets were rushed far away from the surface by the acceleration through the film cooling holes. Using the uniform droplet size distribution provides noticeably better cooling enhancement in the first 40% of the vane’s height (from the shroud) than the non-uniform droplet size distribution (Rosin-Rammler Distribution) does.