Flow Features of Three Side-by-side Circular Cylinders at Low Reynolds Number

In order to study the fluctuation of kinetic parameter of cylinder matrix in incompressible stationary flow, the flow fluid around three side-by-side circular cylinders are simulated using Immersed Boundary–Lattice Boltzmann method (IB-LBM). Drag and lift force of the three cylinders are investigated as the interval between each cylinder varied from zero to five times of the cylinder diameter. Five flow patterns are defined according to the vortices structure in the downstream of the cylinders. Power spectrum analysis of lift force is developed to explain the vortex patterns. Through the research, we find the strength and phase of the gap flow play an important role in the vortex formatting process. The vortices shedding from different cylinders neutralize and combine in the near wake, contributing a lot to the variation of forces

Flow Features of Three Side-by-side Circular Cylinders at Low Reynolds Number

In order to study the fluctuation of kinetic parameter of cylinder matrix in incompressible stationary flow, the flow fluid around three side-by-side circular cylinders are simulated using Immersed Boundary–Lattice Boltzmann method (IB-LBM). Drag and lift force of the three cylinders are investigated as the interval between each cylinder varied from zero to five times of the cylinder diameter. Five flow patterns are defined according to the vortices structure in the downstream of the cylinders. Power spectrum analysis of lift force is developed to explain the vortex patterns. Through the research, we find the strength and phase of the gap flow play an important role in the vortex formatting process. The vortices shedding from different cylinders neutralize and combine in the near wake, contributing a lot to the variation of forces

The soft magnetic properties of ring-shaped (Co0.6Fe0.3Ni0.1)(68)(B0.811Si0.189)(27)Nb-5 bulk metallic glasses

Ring-shaped (Co0.6Fe0.3Ni0.1)(68)(B0.811Si0.189)(27)Nb-5 bulk samples with an outer diameter of 10 mm, an inner diameter of 6 mm, and a thickness of 1 mm were successfully prepared by copper mold casting. The effects of annealing treatments on magnetic properties of the ring-shaped bulk sample were investigated. After the optimum annealing treatment, the resulting ring-shaped bulk sample exhibits good magnetic properties, i.e., low coercive force of 0.55 A/m, high maximum permeability of 433 000, and high permeability of 19 400 at 50 Hz under an AC field amplitude of 1.2 A/m, respectively. In addition, the ring-shaped bulk sample also shows low core loss of 0.09 W/kg at 50 Hz under induction of 0.5 T. The synthesis of ring-shaped bulk samples with good magnetic properties is encouraging for their potential applications as functional materials in the future. (C) 2013 AIP Publishing LLC

Novel Fe-based nanocrystalline powder cores with high performance prepared by using industrial materials

The FeSiBPNbCu amorphous magnetic powder with partial crystallization is successfully synthesized using low purity industrial raw materials by gas atomization. The magnetic powder cores (MPCs) are then produced from the mixture of the FeSiBPNbCu powders with 2 wt % epoxy resin as insulation and bonding materials by cold pressing under a compact pressure of 1800 MPa. Evolution of the high-frequency properties for the MPCs with respect to the annealing temperature is systematically studied. The results show that upon annealing at the optimum temperature, the cores exhibit excellent magnetic properties, including high initial permeability of 86 with a high frequency stability up to 10 MHz, high quality factor of 110 at 1 MHz, and low core loss of 1290 mW/cm(3) at 100 kHz for B-m = 0.1 T. It is emphasized that the MPCs prepared by partially crystallized magnetic powders can also achieve lower core losses and higher magnetic permeability, which is of great significance in industrial production

Structural and magnetic characterization of Al microalloying nanocrystalline FeSiBNbCu alloys

The magnetic properties of nanocrystalline Fe77Si10B9Cu1Nb3-xAlx (x = 0 and 1) alloys have been investigated and their structural and electromagnetic parameters have been quantitatively studied by X-ray diffraction, transmission electron microscopy and Mossbauer spectra under one-step and two-step annealing processes. The nanocrystalline structure consists of single alpha-Fe(Si) phase embedded in a residual amorphous phase. Both saturation magnetic flux density (B-s) and permeability (mu) of the nanocrystalline alloys are increased by substituting 1 at% Al for Nb and one-step annealing, from B-s= 1.41 T to 1.47 T and from mu = 18,000 to 23,000 at 1 kHz, respectively. The two-step annealing has little effect on the B-s, coercivity (H-c) and grain size of the nanocrystalline alloys, but greatly improves the mu of the Al-doped alloy, reaching up to 28,000 at 1 kHz. The improved mu can be attributed to the increased magnetic moment and exchange stiffness constant, homogeneous chemical structure and reduced magnetostriction. The Al-doped nanocrystalline alloy with high B-s, high mu, low H-c and good frequency stability are good candidates for magnetic shielding pieces of wireless charging

Study on the Protection Effect of Sprinklers on Glass by Fire Scale in Building Fires

Window sprinklers are commonly used to protect glass, but there is a lack of research on the effect of fire scale on protection. In this study, full-scale experiments on sprinkler-protected glass in building fires were carried out. The experimental process was simulated using CFD numerical simulation software (FDS), and the effect of the heat release rate on the protection effect was revealed based on the glass surface temperature and heat insulation efficiency. It was found that in a full-size compartment fire, the window sprinkler was able to protect the glass from being damaged by high-temperature smoke. The numerical simulation could effectively simulate the spray distribution pattern of a window sprinkler as well as the gas temperature evolution, and the simulation results matched well with the full-size experiments. The window surface temperatures all decreased rapidly and increased linearly with the HRR after the window sprinkler was activated. The steady-state window center temperatures were 40 °C, 60 °C and 76 °C when the HRR was 2 MW, 4 MW and 6 MW, respectively. The window center temperature was less than the critical temperature of glass breakage, indicating that the window sprinkler could protect the glass from fire damage well, within the fire scale of 6 MW. The thermal insulation efficiency in the edge region was slightly lower than that in the center of the window. In the range of 2 to 6 MW, there was no significant correlation between the thermal insulation efficiency and the HRR, and the thermal insulation efficiency was in the range of 54% to 59%

Novel Fe-based nanocrystalline powder cores with high performance prepared by using industrial materials

The FeSiBPNbCu amorphous magnetic powder with partial crystallization is successfully synthesized using low purity industrial raw materials by gas atomization. The magnetic powder cores (MPCs) are then produced from the mixture of the FeSiBPNbCu powders with 2 wt % epoxy resin as insulation and bonding materials by cold pressing under a compact pressure of 1800 MPa. Evolution of the high-frequency properties for the MPCs with respect to the annealing temperature is systematically studied. The results show that upon annealing at the optimum temperature, the cores exhibit excellent magnetic properties, including high initial permeability of 86 with a high frequency stability up to 10 MHz, high quality factor of 110 at 1 MHz, and low core loss of 1290 mW/cm(3) at 100 kHz for B-m = 0.1 T. It is emphasized that the MPCs prepared by partially crystallized magnetic powders can also achieve lower core losses and higher magnetic permeability, which is of great significance in industrial production

New Fe-based amorphous soft magnetic composites with significant enhancement of magnetic properties by compositing with nano-(NiZn)Fe2O4

Amorphous soft magnetic composites based on spherical Fe76Si9B10P5 amorphous powder made by gas atomization and (NiZn)Fe2O4 nanoparticles dispersed in epoxy resin are investigated in details. Scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis revealed that the surface layer of the amorphous powder consisted of (NiZn)Fe2O4 nanoparticles and epoxy resin with uniform surface coverage. The samples composited with (NiZn)Fe2O4 nanoparticles have an significant enhancement of permeability in comparison with uncoated ones. The permeability of the composite cores at 20 kHz is 101 with the addition of 2 wt% (NiZn)Fe2O4 nanoparticles, which was increased 44% as compared with that of uncoated samples (70). In addition, it could be able to maintain a relatively low core loss of 1210 mW/cm(3) (B-m - 0.1 T, f - 100 kHz). The compound Fe76Si9B10P5/(NiZn)Fe2O4 soft magnetic composites with excellent soft magnetic properties provide great potential for expanding the application of various electronic components like low frequency filters, DC output chokes and resonant inductors. (C) 2016 Elsevier B.V. All rights reserved

Influence of static magnetic field on rapid solidified structure and nanocrystallization behavior of Fe–Si–B–Cu soft magnetic alloys with pre-existing α-Fe nanocrystals

The effects of static magnetic field strength on the rapid solidified structure, thermal stability, crystallization structure and soft magnetic properties of melt-spun Fe81.6Si4B13Cu1.4 alloys were investigated and the corresponding related mechanism was discussed in terms of formation of pre-existing α-Fe crystals and nanocrystallization behaviors. The rise of magnetic field strength promotes the formation of the α-Fe crystals in as-spun alloy, enhances the competitive growth between the crystals during annealing, and then refines the crystals in the annealed alloy and improves their magnetic softness. The Fe81.6Si4B13Cu1.4 alloy prepared under 200 mT contains α-Fe crystals with a high number density and average size (D) of 8.3 × 1022 m−3 and 5.9 nm, respectively, in as-spun state, and possesses fine crystals with a D of 18.2 nm and excellent soft magnetic properties with a high saturation magnetization of 1.75 T, low coercivity of 9.2 A/m and high effective permeability of 10,160 at 1 kHz after annealing at 633 K for 60 min

Low core loss combined with high permeability for Fe-based amorphous powder cores produced by gas atomization powders

Gallium-doped zinc oxide; Titanium dioxide co-doping; Moisture resistance; Weak-acid resistance; Magnetron sputtering; Thin film