“Plasma Tube” is proposed for nano particle transportation and for particle surface purification in this study. The well-controlled efficient nano particle transportation is realized by combining plasma actuation, electrostatic force and high oxidation potential of produced ozone in a tube. Nano particles in the plasma tube can be transported in axial direction with swirl. Nano particles near the inner electrode wall jump due to electrostatic force, which can suppress particle clogging in a tube. The characteristics of plasma induced flow, particle charging and ozone generation are experimentally clarified in this study for various electrode angles and electrical conditions. Finally, the powder transportation rate is quantitatively evaluated. The alumina powder with average diameter of 30 nm can be transported at the maximum rate of 2.8 mg/s at consumption power of as low as 0.35 W for the transportation distance of 100 mm.
Axial fluctuations in carrier concentrations cause detection noise during chemical analysis using flowing carrier streams. Here, we report a method of axial mixing using serially cascaded microchannel units with branches and junctions. Two branched channels in one unit differ in liquid residence time, and the time lags between the two branched channels are different for each unit. Each unit decreases the fluctuations in carrier concentration of the frequency associated with the time lag. The branched channels are in the form of spirals to induce the secondary flow that decreases axial dispersion and enhances the cancelling effect of the axial fluctuations from the branched channels. We evaluated the effect of secondary flow on the reduction in axial dispersion as a function of the Dean number in computational fluid dynamics simulations. Axial mixing in the prototype mixer was the most effective at a Dean number of 10. A prototype mixer whose volume was 52.5 mm3 reduced absorbance fluctuations from 27.2 to 5.0 mAU in a 0.1% trifluoroacetate aqueous: acetonitrile stream under these conditions. The frequency characteristics of the reduced absorbance fluctuations were evaluated through numerical simulations within a deviation of 20%.
This research presents a wind tunnel experiment for investigating three-dimensional flows in the vicinity of a blade in a Horizontal Axis Wind Turbine (HAWT) model. Though the design of the wind turbine blade has been recognized as a modern advance, most of them are based on two-dimensional sectional performance analyses. However, the actual flow around the rotating blade also has a flow effect from a span-wise direction that it is generated from centrifugal and Coriolis forces. A span-wise flow can change the boundary layer on the blade surface. The sectional performance strongly depends on the surface boundary layer. Thus, the actual flow characteristics and correct surface boundary layer in thevicinity of a wind turbine blade is important in designing a wind turbine blade with high performance. In this research, the test wind turbine was a three-bladed type. The test blade comprised four types of airfoils that were smoothly connected and distributed along the blade. The experimental investigation of the flow on the blade surface was performed by simultaneously measuring three-dimensional velocity components by the approach of a three-dimensional Laser Doppler Velocimetry (LDV) method: two LDV probes were used in the synchronized measurement of three-dimensional velocity components. Characteristics of the three-dimensional flow were investigated and visualized by velocity vector field, boundary layer and trajectory path. The results clarified that the three-dimensional flow for the inboard had higher values than the outboard. The two-dimensional relative velocity and the span-wise velocity for the optimum tip speed ratio and low tip speed ratio showed significant differences in the boundary thickness. The shape factor H had satisfactory results and could clearly separate laminar and turbulent regions. The flow trajectory seemed to be affected by the span-wise velocity at chord station y/c > 0.25.
Understanding and predicting the efficiency of displacement, i.e., the non-wetting phase saturation after drainage, is of great importance in many practical applications. In this study, we experimentally derive the empirical equations of the non-wetting phase saturation as a function of the capillary number, the Bond number, and the viscosity ratio. A series of laboratory experiments are conducted with a packed bed of glass beads. Several fluid pairs are used to change the viscosity ratio. However, the density of the non-wetting phase is lower than that of the wetting phase for all pairs. In the case of vertically upward injection, the non-wetting phase saturation decreases with the Bond number and increases with the capillary number for all fluid pairs. In the case of the unfavorable viscosity ratio, the non-wetting phase saturation is low because the displacement interface is always unstable. At a low capillary number, the capillary fingering enhanced by buoyancy results in low non-wetting phase saturation. In the case of the downward injection, if the viscosity ratio is favorable, the displacement front is always stable against the Darcy velocity. If the viscosity ratio is unfavorable, the displacement front is stable for low Darcy velocity, when the non-wetting phase saturation is high. When the Darcy velocity exceeds the critical velocity, the non-wetting phase saturation reduces.