Rectangular Ports Research Articles

Numerical Analysis of Hydrogen Behavior Inside Hydrogen Storage Cylinders under Rapid Refueling Conditions Based on Different Shapes of Hydrogen Inlet Ports

In order to investigate the effects of different shapes of hydrogen inlet ports on the behavioral characteristics of hydrogen in Type IV hydrogen storage cylinders under rapid refueling conditions, a mathematical model of hydrogen temperature rise and a three-dimensional numerical analysis model were developed. The rectangular, hexagonal, triangular, Reuleaux triangular, circular, elliptical and conical inlet ports were researched by using computational fluid dynamics methods. The results showed that, for the same refueling flow rate and cross-sectional area, the hydrogen temperature inside a cylinder with a rectangular inlet port is higher and the jet tilt angle is larger than for a hexagonal port, while the thermal stratification phenomenon is not obvious. The hydrogen temperature inside a cylinder with a triangular inlet port is lower than that with a Reuleaux triangle port and the jet tilt angle is larger, and neither has significant thermal stratification. The hydrogen temperature inside a cylinder with a circular inlet port is higher than that with an ellipse port, the jets are not tilted on either one, and the phenomenon of thermal stratification is prominent. Further analysis indicated that enlarging the cross-sectional area and increasing the refueling flow rate results in a higher hydrogen temperature and intensified thermal stratification and an upward-angled jet can effectively reduce or eliminate thermal stratification.

Two phase flow analysis of micro channel evaporator to investigate effect of geometry on pressure and heat transfer coefficient with respect to volume of fraction

Abstract Pressure and heat transfer coefficient (HTC) are parameters used to measure the performance of microchannel evaporators (MCE). By keeping the same overall dimensions, optimised hydraulic diameters of three different port shapes, square, rectangle and trapezoid, are analysed using CFD software to study the effect of geometry on the performance characteristics of MCE. The number of square, rectangle, and trapezoid channels is 580, 986, and 812, respectively. CFD analysis of the evaporator using R134a refrigerant is performed using the Volume of Fluid (VOF) with the SST k-ω model and Lee model for interphase mass transfer trace. Variation of pressure and HTC concerning volume of fraction liquid refrigerant (α) is compared for these three port structures. The trapezoid port microchannel evaporator (MCE) exhibits the highest pressure drop compared to square and rectangular port MCEs. The rectangular port MCE demonstrates the highest heat transfer coefficient among the configurations studied. The rectangular port MCE outperforms both square and trapezoid port MCEs in overall performance.

Ka-band diplexer design based on half-mode groove gap waveguide

This paper shows the practical design of a Ka-band tuning-less diplexer in half-mode groove gap waveguide (HM-GGW) technology for multi-beam satellite applications. This new technology can be easily manufactured, since it lets the design of two separate metallic pieces: one for the cover with periodic pins, and another one for the half-groove gap waveguide structure. The proposed diplexer is composed of two bandpass HM-GGW filters, an H-plane T-junction and the corresponding transitions to the input/output WR28 rectangular ports. To illustrate how this technology can be applied, a prototype has been successfully fabricated, showing in-band measured return and insertion losses of 21 dB and 0.87 dB in the lower band, 16 dB and 0.86 dB in the upper band, and a good isolation level (better than 32.5 dB) in the whole operational frequency range.

Dual-Mode Conical Horn Antenna with 2-D Azimuthal Monopulse Pattern for Millimeter-Wave Applications.

In this paper, a novel concept of a three-dimensional full metal system including a Dual-Mode Converter (DMC) network integrated with a high-gain Conical Horn Antenna (CHA) is presented. This system is designed for 5G millimeter wave applications requiring monopulse operation at K-band (37.5-39 GHz). The DMC integrates two mode converters. They excite either the TE11cir or the TE01cir modes of the circular waveguide of the CHA. The input of the mode converters is the TE10rec mode of two independent WR-28 standard rectangular waveguide ports. By integrating the DMC with the CHA, the whole system, called a Dual-Mode Conical Horn Antenna (DM-CHA), is formed, radiating the sum (Σ) and difference (Δ) patterns associated to the monopulse operation. To adequately prevent the propagation of higher order modes and mode mutual coupling, this integration procedure is carefully designed and fabricated. To prove the performance of the design, the DMC network was fabricated using subtractive manufacturing by Computer Numerical Control (CNC) technology. The CHA was fabricated using additive manufacturing by Direct Metal Laser Sintering (DLMS) technology. Finally, the simulation and measurement results were exhaustively compared, including return loss, isolation, radiation pattern, and gain of the full DM-CHA structure. It is noteworthy that this system provided up to ±11° per beam in the angular of arrival detection to support the high data rate operation for 5G satellite communications in the millimeter-wave band.

Circularly Polarized V-Band Orthomode Transducer

A compact septum-based orthomode transducer (OMT) is designed to provide dual circularly polarized states for horn antennas. The OMT is backfed by two rectangular ports separated by a stepped tapered septum from thick to thin walls toward the common port. The OMT covers 16.7% fractional bandwidth in the V-band (55–65 GHz), which coincides with the fifth generation and beyond (5 GB) communications standards and intersatellite communications. The OMT performance is evaluated by measuring the back-to-back scattering parameters. Measured insertion loss is below 1.3 dB, whereas the isolation between the rectangular ports remains beyond 17 dB in the operating band.

Numerical Investigation of a Rectangular Jet Exhausting over a Flat Plate with Periodic Surface Deformations at the Trailing Edge

Multiple competing factors are forcing aircraft designers to reconsider the underwing engine pod configuration typically seen on most modern commercial aircraft. One notable concern is increasing environmental regulations on noise emitted by aircraft. In an attempt to satisfy these constraints while maintaining or improving vehicle performance, engineers have been experimenting with some innovative aircraft designs which place the engines above the wings or embedded in the fuselage. In one configuration, a blended wing concept vehicle utilizes rectangular jet exhaust ports exiting from above the wing ahead of the trailing edge. While intuitively one would think that this design would reduce the noise levels transmitted to the ground due to the shielding provided by the wing, experimental studies have shown that this design can actually increase noise levels due to interactions of the jet exhaust with the aft wing surface and flat trailing edge. In this work, we take another look at this rectangular exhaust port configuration with some notional modifications to the geometry of the trailing edge to determine if the emitted noise levels due to jet interactions can be reduced with respect to a baseline configuration. We consider various horizontal and vertical offsets of the jet exit with respect to a flat plate standing in for the aft wing surface. We then introduce a series of sinusoidal deformations to the trailing edge of the plate of varying amplitude and wave number. Our results show that the emitted sound levels due to the jet–surface interactions can be significantly altered by the proposed geometry modifications. While sound levels remained fairly consistent over many configurations, there were some that showed both increased and decreased sound levels in specific directions. We present results here for the simulated configurations which showed the greatest decrease in overall sound levels with respect to the baseline. These results provide strong indications that such geometry modifications can potentially be tailored to optimize for further reductions in sound levels.

A diagnostic for measuring radial profile of visible continuum radiation from ADITYA-U Tokamak Plasmas

On ADITYA-U tokamak, a spectroscopic diagnostic has been developed to measure the radial profile of visible continuum radiation for determining the plasma effective charge, Zeff, to study the impurity transport and MHD driven instabilities. It consists of the collimating lenses, optical fibers, a multi-channel wavelength selection system, and photo multiplier tubes. The optical system allowing continuum radiation measurements around 536 nm (the wavelength selection system) consists of set of lenses, optical fibers and an interference filter with diameter of 5 cm and bandwidth of 3 nm. The spatial profile of radiation with a spatial resolution of ∼ 3 cm has been recorded from eight lines of sight viewing the plasma using an UHV compatible rectangular view port placed on the bottom port of the ADITYA-U tokamak. The centrally peaked spatial profile of visible continuum radiation has been recorded from the ADITYA-U tokamak plasmas. The chord averaged Zeff values estimated from the brightness measured along the central chord fall within 2.5 to 4.1 for the electron densities of 1.0 - 2.2 × 1019 m−3.

Determination of laminar burning velocity of methane/air flames in sub atmospheric environments

The global energy demand enhances the environmental and operational benefits of natural gas as an energy alternative, due to its composition, mainly methane (CH4), it has low polluting emissions and benefits in energy and combustion systems. In the present work, the laminar burning velocity of methane was determined numerically and experimentally at two pressure conditions, 0.85 atm and 0.98 atm, corresponding to the city of Medellín and Caucasia, respectively, located in Colombia. The environmental conditions were 0.85 atm, 0.98 atm, and 295±1 K. The simulations and experimental measurements were carried out for different equivalence relations. Experimental laminar burning velocities were determined using the burner method and spontaneous chemiluminescence technique, flames were generated using burners with contoured rectangular ports to maintain laminar Reynolds numbers for the equivalence ratios under study and to reduce the effects of stretch and curvature in the direction of the burner's axis. In general, the laminar burning velocity fits well with the numerical results. With the results obtained, a correlation is proposed that relates the laminar burning velocity with the effects of pressure, in the form SL=aPb, where a and b are model constants. Sensitivity analysis was performed using the GRI-Mech 3.0 mechanism which showed that the most sensitive reaction was H+O2=O+OH (R38). Additionally, it was found that the reactions H+CH3 (+M)=CH4 (+M) (R52), 2CH3 (+M)=C2H6 (+M) (R158), and O+CH3=H+CH2O (R10) dominate the consumption of CH3 which is an important radical in the oxidation of methane, this analysis is carried out for equivalence ratios of 0.8 and 1.0, and atmospheric pressures of 0.85 atm and 0.98 atm

Additive manufacturing of a compact Ku-band orthomode transducer

This work presents a compact ortho-mode transducer (OMT) built by additive manufacturing in a single-block, reducing the number of parts and flanges and improving the losses and power handling capability. The single-block approach also reduces potential passive intermodulation issues since the number of interfaces between parts is minimized. The presented OMT is based on the T-junction topology, with a short-circuited common circular waveguide where the two rectangular waveguides ports are attached. Both ports are arranged in opposite direction to maintain a symmetry plane for the whole structure in order to obtain a high isolation. Specific matching elements are introduced for each polarization to route the orthogonal modes to the common waveguide. The device is built by Selective Laser Melting (SLM), which imposes a set of specific mechanical restrictions to the 3D model of the OMT. The proposed design incorporates those restrictions, simplifying the geometry of the OMT as much as possible (especially the routing elements) to simplify the manufacturing. After this process, the experimental results show an OMT working in the band from 13.4 to 15.6 GHz (15.2%) with a return loss level higher than 20 dB for both polarizations, insertion loss lower than 0.18 dB and isolation between polarizations better than 45 dB. The OMT has also been tested in radiation connected to a reference horn, measuring a cross-polarization lower than -45 dB. This experimental performance shows that the proposed combination of compact design with single-block SLM manufacturing provides tested results similar to those obtained by high-accuracy milling or spark erosion suitable for satellite applications.

Numerical Study of the Microflow Characteristics in a V-ball Valve.

V-ball valves are widely applied in many process industries to regulate fluid flow, and they have advantages of good approximately equal percentage flow characteristics and easy maintenance. However, in some applications, the V-ball valve needs to have good performance under both large and extremely small flow coefficients. In this paper, the improvement of the original V-ball valve is made and the flow characteristics between the original and the improved V-ball valve are compared. Two types of small gaps are added to the original V-ball, namely the gap with an approximately rectangular port and the gap with an approximately triangular port. The effects of the structure and the dimension of the gap on flow characteristics are investigated. Results show that within the gap, the flow coefficient increases but the loss coefficient decreases as the valve opening increases, and the flow coefficient has an approximately linear relationship with the flow cross-area of the added gap. Results also show that under the same flow cross-area, the flow coefficient has a higher value if the distance between the gap and the ball center is greater or if the gap is an approximately rectangular port, while the loss coefficient has an opposite trend.

Mathematical modeling of arbitrary shaped harbor with permeable and impermeable breakwaters using hybrid finite element method

A mathematical model is developed based on the application of permeable and impermeable breakwaters utilizing the mild slope equation (MSE) to analyze the wave amplification in an arbitrary shaped harbor with variable bathymetry. Finite element method (FEM) coupled with analytical approximation is described as Hybrid FEM, which is used to solve the MSE and Helmholtz equation in bounded and unbounded domains (open Sea region), respectively. The validation of the present numerical scheme is conducted by comparing the simulation results with the existing studies and the convergence analysis is also conducted to verify the accuracy of the numerical scheme. The effects of energy dissipation, bottom friction, and variable wave transmission through impermeable and permeable breakwaters are investigated to understand the resonance phenomenon in rectangular port. In addition, the current numerical scheme is implemented on a real Paradip port, Odisha, India at six different key locations, and for the first time the effect of breakwaters placed at the entrance and in the bounded region, along with bottom friction, and partially reflecting port boundary are investigated. The breakwaters with small permeability/transmission coefficient have high efficiency to reduce the wave resonance inside the port.

On the Accurate Full Characterization of Septum Polarizers Through Simple Amplitude Measurements in Back-to-Back Configuration

This article introduces an easy and accurate technique for the full characterization of septum polarizers (SPs) in back-to-back configuration through standard amplitude/power measurements at the rectangular waveguide ports. The proposed calibration algorithm, based on the use of two simple waveguide sections, along with the developed mathematical formulation, allows the complete extraction of the relevant SP parameters: return loss, isolation, cross-coupling (XP) or axial ratio (AR), and copolarization losses (CP). The methodology has been successfully validated for two different designs at Ku-band.

Spectral wave modeling of tsunami waves in Pohang New Harbor (South Korea) and Paradip Port (India)

A coupled numerical model is developed based on the spectral element method (SEM) and boundary element method (BEM) to predict the characteristics of tsunami wave response on Pohang New Harbor (PNH), South Korea, and Paradip Port, India. The current numerical model is developed to analyze the impacts on the coastal region with slowly varying bathymetry under the resonance conditions. In this method, the boundary integral equation of each boundary segment is discretized into the spectral elements using the Chebyshev’s polynomial, and the corresponding boundary integrals are transformed using the Jacobian of transformation. This leads to a highly accurate depiction of the boundary edges or corners of the complex domain. Convergence and error analyses are conducted on the rectangular port using the BEM and the present method, which shows that the later approach enhances the overall numerical accuracy of the model. The simulation results for normal day wave (ordinary wave propagating in the ocean under normal conditions) and tsunami waves are validated with previous studies and measurement data at Pohang New Harbor (PNH), South Korea. In addition, the calculated spectral density for tsunami waves at PNH is also compared with the Hokkaido tsunami (reported on July 12, 1993) data at tide gauge record station in Pohang. The amplification factor is determined for normal day wave and tsunami waves at key locations inside the PNH and Paradip Port for different directional incident waves. Further, the spectral density is also estimated at the same locations with respect to the wave period to understand the consequences of tsunami waves on the coastal ports. Therefore, the coupled numerical model is an efficient tool to predict tsunami wave impact on a realistic port. The causes and countermeasure are suggested to reduce the risk of normal day waves and tsunami waves.

A Simple Asymmetric Orthomode Transducer Based on Groove Gap Waveguide

The groove gap waveguide (GGWG) technology is used to design a simple asymmetric orthomode transducer (OMT) at the Ka -band in this letter. The OMT consists of two metal layers which do not need electrical contact due to the property of the gap waveguide technology. The vertical polarization (VP) is directly fed to a standard rectangular waveguide port from the main arm of a square waveguide, while the horizontal polarization (HP) is fed to the side arm by an H-bend. No septum or iris is needed, which contributes to a simple structure. The OMT has been manufactured and measured using a back-to-back setup. A high isolation of over 40 dB is achieved within the working band from 26.1 to 29.3 GHz. The reflection coefficient is below −11.4 and −17.7 dB for the HP and VP, respectively. The higher return loss of the HP is caused mainly by the manufacturing errors. Nevertheless, the insertion loss for both polarizations is below 0.25 dB for a single OMT.

부산 연안 소규모 어항의 수역시설 규모 분석과 형태 분류에 관한 연구

In this study, we propose six characteristic factors to understand the topographic characteristics of the fishing port for the installation and use of facilities reflecting the topographical characteristics in the future development of small scale fishing port. This was applied to 34 small fishing ports in Busan coast. As a result, the curvature of the fishing port is large in the case of the urban-type fishing port (section II), the fishing port in the port area (section III), and the fishing port (IV) located in the city"s large river, And the other fishing ports show relatively small curvature. In addition, the shape factors proposed in this study can determine the shape of the fishing port and the surface area, the shape of the shoreline, and the openness of the fishing port. In the case of the coastal length S, the hydraulic radius(R), and the virtual rectangular fishing port surface area(A"), the fishing port characteristic factor increases as the actual water facility increased(A). However, other factors did not show a high correlation.

A New 4 × 4 Rectangular Waveguide Short-Slot Coupler in 3D Printed Technology at Ku-Band

This paper presents a novel design of an eight-port directional coupler with a very compact structure and simple manufacturing, working in the Ku frequency band. One of the main goals of the design was to ease the manufacturing with a simple structure: the coupler consisted of four rectangular waveguide input ports, four rectangular waveguide output ports, and a central coupling region with only H-plane variation. A prototype was fabricated using additive manufacturing, with a combination of 3D printing and silver coating metallization. The obtained performance showed a theoretical bandwidth of 6.6% with 20 dB return loss for the input/output ports. Good agreement between simulations and measurements was obtained, validating the proposed coupler as a good trade-off for low cost 3D printing, compactness, and high performance for systems requiring a high number of ports as in phase arrays or Butler matrices.

Optimum Septum Polarizer Design for Various Fractional Bandwidths

The numerical optimization results of constant thickness septum polarizer’s performances for various operating fractional bandwidths (FBW) are presented in the paper. The polarizer’s structure includes a common input square waveguide, a constant thickness septum with several steps, and two output rectangular waveguides. The polarizer design of 2-, 3-, 4-, and 5-step septums is optimized for different narrow and wide operating FBWs to obtain the simultaneously maximum values of cross-polarization discrimination and isolation between rectangular ports and return losses. The optimized dimensions of the septums for FBW = 5, 10, 15, 18, and 20% are presented. Based on the obtained results, Q- and K-band prototypes were manufactured and their performances were measured. The measurements of the prototypes are in good agreement with simulations. These optimization results can be widely used for the development of septum polarizers and prediction of their performances for various FBW in the required frequency range.

A Waveguide Switch Based on Contactless Gap Waveguide Technology

A novel dual-pole dual-throw (DPDT) waveguide switch is proposed for high-power and low-loss applications. The proposed DPDT was designed based on the contactless properties of the gap waveguide technologies in the Ku frequency band. The DPDT was composed of two concentric contactless cylinders. Standard rectangular waveguide ports (WR 75) and waveguide paths are machined in the middle of these cylinders. The rotational movement of the inner cylinder is realized using two bearings in the top and bottom of the DPDT. The proposed structure is fabricated and the measured results are in good agreement with the simulated ones. The measured insertion loss and return loss for the aligned ports are better than 0.1 and 25 dB in the frequency band ranging from 11 to 13.5 GHz, respectively, and the measured isolation between two adjacent ports is better than 60 dB.

Modal Analysis of Directional Coupler and Its Equivalent Circuit

A modal analysis for the directional coupler is presented in this paper. The analysis is based on the mode-matching technique. The theory is verified by Ansoft HFSS software at a directional coupler with standard X-band (WR 90) rectangular waveguide ports. Element values of equivalent circuit model are computed by using the S-parameters obtained from the presented method in this paper. In addition this paper has corrected two formulations used in two previous works which have been published.

Full-Band Oversized Turnstile-Based Waveguide Four-Way Power Divider/Combiner for High-Power Applications

Very high-power and high-efficiency microwave applications require waveguide structures to combine/divide the power from/to a variable number of high-power solid-state devices. In the literature, among the different waveguide configurations, those capable of providing the maximum output power show a limited relative bandwidth. To overcome this limitation, in this paper a full-band (40%) waveguide power divider/combiner specifically designed for high-power applications (up to several kW) is presented. The proposed structure uses an evolved turnstile junction with a standard rectangular waveguide common port, rotated 45°, with respect to its central axis, to divide/combine the signal to/from the four output/input rectangular ports. The inclusion of an oversized central cavity together with circular and rectangular waveguide impedance transformers at the common port allows the achievement of a full-band operation with excellent electrical performance, while maintaining a very simple and compact configuration. Only two layers of metal are required for the physical implementation of this structure in platelet configuration. A prototype has been designed covering the full Ka-band (26.5–40 GHz), showing an excellent measured performance with around 30 dB of return loss, 0.18 dB of insertion loss, and less than 1.5° of phase imbalance.