Study of interface gas-liquid flow characteristics in a rectangular microchannel for wavy-annular flow

The aim of this work is an experimental study of a gas-liquid flow in a rectangular slit microchannel with a cross-section of 200 × 2045 μm. Ethanol/water (95/5) mixture and nitrogen are used as working liquid and gas, accordingly. The external T-mixer is used for obtaining of wavy-annular flow pattern. The experimental data on interfacial waves and their characteristics in the meniscus area on the short side of the microchannel are obtained using high-speed visualization for a wide range of gas and liquid superficial velocities. Images are processed using the Python libraries to define the average liquid layer thickness and maximum amplitude of waves. An increase of gas superficial velocity causes decreasing in the average liquid layer thickness and maximal amplitude of the liquid layer thickness. The waves on the liquid layer surface (maximal amplitude) can be three times larger than the average liquid layer thickness for presented liquid and gas velocities. With increasing gas superficial velocities more liquid displace from the meniscus area to the liquid film on the wide side of the microchannel.

Application of the laser-induced fluorescence to study local characteristics of a gas-liquid flow in rectangular microchannel

The Laser-Induced Fluorescence (LIF) method was used to characterize liquid phase distribution in rectangular slit microchannel with cross-section 200×1205 μm for horizontal gas-liquid flow. Ethanol and nitrogen were used as working liquid and gas accordingly. The feature of this study is an application of hydraulic focusing cross-junction mixer for obtaining elongated bubble and transition flows in the microchannel with a high aspect ratio. Using LIF measurements for elongated bubble and transition flows the liquid film distributions were obtained for different distances from the bubble top and average liquid film thickness was compared with the prediction according to Taylor’s law.

Extrusion rheometry of collagen dough

Although collagen is widely used (for example, in the food industry, in the pharmaceutical industry and in biomedicine), the rheological properties of the material are not well known for high concentrations (8% collagen, 90% water). Rheological properties were measured using a capillary-slit rheometer (an extrusion process), where the tested sample of collagen matter was pushed by a hydraulically driven piston through a narrow rectangular slit at very high shear rates of 50–6 000 s^–1. The Herschel-Bulkley (HB) constitutive equation and a new correlation taking into account the finite gap width was used to evaluate the rheological properties (n = 0.2, K = 879 Pa sⁿ, τ₀ = 2 380 Pa). Use was made of a new yield stress measurement method evaluating τ₀ 'post mortem' after extrusion stops. The effects of wall slip and of air bubbles, which caused apparent compressibility of the 'silly putty' collagen material, were also studied. Corrections of the wall slip effect were implemented using sliding layer thickness δ.

An octagonal ultra-wideband double slit antenna for WiMAX and WLAN rejection

This article proposes a dual band rejected double slits-based planar octagonal microstrip antenna for Ultra-Wideband (UWB) applications. The antenna built by an edge trimmed partial ground and an octagonal microstrip patch with a horizontal and an inclined rectangular slit. The slits are made to remove the interfering frequency bands WiMAX and WLAN from UWB band. The designed antenna without slits operates on the frequency range 2.78–10.78 GHz with a fractional bandwidth of 119% which includes the UWB frequency band 3.1–10.6 GHz. The antenna with diagonal inclined slit notches the band 4.4–5.83 GHz which excluded WLAN frequency range and shift the starting frequency of UWB band to the right from 2.78 to 3.26 GHz. The antenna with both horizontal and inclined slits further shifts the starting frequency from 3.26 to 3.619 GHz, eliminating the WiMAX band. The excluded bands show the VSWR value greater than 2 dBi whereas the rest of the band has less than 2 dBi. The proposed antenna results in nearly omnidirectional radiation pattern, 6.2 dBi peak gain and 85% radiation efficiency.

Estimation of power consumption when trapping finely-dispersed particles in a separator with coaxially-arranged pipes

This article sets out to estimate power consumption when trapping finely-dispersed particles of silicon dioxide using a separator with coaxially-arranged pipes, as well as the efficiency of such an installation. To this end, a numerical simulation of the movement of a gas flow with finely-dispersed particles of silicon dioxide through a separator with coaxial pipes was carried out in the ANSYS Fluent software. During the experiments, the inlet gas flow rate varied from 5 to 10 m/s, while the width and height of the rectangular slit ranged 2.1-8.7 and 10-30 mm, respectively. It was shown that the maximum efficiency of collecting finely-dispersed silicon dioxide particles and the minimum power consumption required for pumping the gas flow through the installation largely depends on the formation of a stable vortex structure in the interpipe space. The research showed that the optimal inlet gas flow rate equals 7.5 m/s. At this rate, the efficiency of particle collection corresponds to higher rates with a devia tion of ± 6%. In this case, the pressure loss is 1.74 times lower than that at higher rates. In order to achieve an efficiency of at least 90% with the height of the rectangular slit from 10 to 30 mm, the Stokes numbers must correspond to values of more than 50. The power consumption required for pumping a gas containing silicon dioxide particles through a separator equipped with coaxial pipes comprises from 1.9 to 31.2 W at the inlet gas flow rate of 7.5 m/s. In this case, the parameters of the rectangular slit are as follows: width - from 2.1 to 8.7 mm, height - from 10 to 30 mm. The use of separators with coaxially-arranged pipes in technological lines based on plasma technologies can become an alternative to installations for fine gas purification.

Compact Enhanced CPW-Fed Antenna for UWB Applications

This paper presents a compact antenna with co-planar waveguide (CPW) feed line for ultra-wideband (UWB) applications. The proposed antenna consists of a beveled radiating patch with wide rectangular slit at its upper side and a partial ground plane with insertion of symmetrically two-step beveled tapers at its center and sides, which provides a wide operating bandwidth. The antenna is integrated with narrow rectangular-shaped parasitic elements with different lengths placed adjacent to radiant patch to significantly enhance the impedance matching and bandwidth, especially at the upper frequencies. The measured results show an |S11| less than -10 dB bandwidth of 2.5-19.8 GHz with 155% fractional bandwidth. Simulation results are in good agreement with experimental measurements, which exhibits the validity of the proposed design approach. Moreover, the proposed CPW-fed antenna shows omnidirectional radiation patterns with stable gain within the operational range. The proposed compact antenna with low profile, light weight, large frequency bandwidth, ease of fabrication and low cost material is suitable for UWB applications.

On the Design and Analysis of Compact Super-Wideband Quad Element Chiral MIMO Array for High Data Rate Applications

This paper presents a compact, bouquet-inspired, four-element MIMO array for super wideband (SWB) applications. The proposed unit element monopole antenna has compact geometry, and it is deployed by the fusion of an elliptical and circular-shaped radiator. The convoluted geometry and semi-elliptical ground plane, along with the narrow rectangular slit defected ground structure, provides a wide impedance bandwidth. The designed unit cell has the dimensions of 32 mm × 20 mm × 0.8 mm, operates from 2.9 to 30 GHz (S11 ≤ −10 dB) and provides a bandwidth dimension ratio (BDR) of 2894. The proposed low-profile diversity array without any decoupling structures consists of four orthogonally placed, uncorrelated antennas with an inter element spacing of 0.05 λ0, occupies an area of 57 mm × 57 mm and provides dual polarization. The performance metrics of the diversity array were validated for frequencies over ultra-wideband, using mutual coupling characteristics, envelope correlation coefficient (ECC) by far-field radiation, diversity gain (DG), total active reflection coefficient (TARC), channel capacity loss (CCL) and cumulative distribution function (CDF) analysis. The measured mutual coupling over the operating band was less than −18 dB, the ECC was less than 0.004 and the TARC was less than −15 dB, and a better CCL of ˂0.28 bits/s/Hz was achieved by the fabricated antenna.

Meander-Line Slot-Loaded High-Sensitivity Microstrip Patch Sensor Antenna for Relative Permittivity Measurement

A high-sensitivity microstrip patch sensor antenna (MPSA) loaded with a meander-line slot (MLS) is proposed for the measurement of relative permittivity. The proposed MPSA was designed by etching the MLS along the radiating edge of the patch antenna, and it enhanced the relative permittivity sensitivity with an additional effect of miniaturization in the patch size by increasing the slot length. The sensitivity of the proposed MPSA was compared with that of a conventional rectangular patch antenna and a rectangular slit (RS)-loaded MPSA, by measuring the shift in the resonant frequency of the input reflection coefficient. Three MPSAs were designed and fabricated on a 0.76 mm-thick RF-35 substrate to resonate at 2.5 GHz under unloaded conditions. Sensitivity comparison was performed by using five different standard dielectric samples with dielectric constants ranging from 2.17 to 10.2. The experiment results showed that the sensitivity of the proposed MPSA is 6.84 times higher for a low relative permittivity of 2.17, and 4.57 times higher for a high relative permittivity of 10.2, when compared with the conventional MPSA. In addition, the extracted relative permittivity values of the five materials under tests showed good agreement with the reference data.