Trapezoidal Slot Research Articles

Numerical Analysis of a Novel Casing Treatment in an Axial Flow Fan

The present paper reports the use of a slotted casing treatment of trapezoidal shape to enhance the stall margin of an axial flow fan. The Taguchi method was used to optimize the rectangular slotted casing treatment based on that which the trapezoidal slots were designed. The unsteady numerical simulations were carried out using the shear-stress-transport turbulence model. The rotor with trapezoidal slots led to the stall margin improvement of 23.4% and mild pressure rise of 0.54%. Without the casing treatment, the tip leakage trajectory was directed from the suction surface of the blade toward the pressure surface of the adjacent blade. After incorporating the trapezoidal slots, the tip leakage trajectory was significantly shifted toward the suction surface of the same blade. This alteration in flow characteristics near the blade-tip region may be attributed to the exchange of momentum due to the simultaneous suction and blowing through the trapezoidal slots. It was also found that the trapezoidal slots improved the axial flow velocity and reduced the diffusion factor in the blade-tip region as compared to the baseline case.

Experimental investigation of double-glazed double-pass solar airheater (DG-DPSAH) with multi-v ribs having trapezoidal roughness geometry

In this study, roughness in the form of multi-V ribs having trapezoidal slots were crafted over the surface of absorber plate for enhancing the heat transfer rate in a solar air heater. An ex-perimental setup was designed and fabricated for demonstrating the performance of this plate with respect to smooth absorber plate. The setup has a double glazed-double pass air flow arrangement. The experiments were conducted under Indian climatic conditions (Latitude = 28.53˚N and Longitude = 77.39˚E) in September and October 2021 at various rates of air flow through the duct. The results of the roughened absorber plate were compared with the smooth absorber plate. It shows that the multi-V ribs with trapezoidal slots have higher efficacy as compared to smooth absorber plate in the order of 10.42% at an air flow rate of 0.078 kg/s. In addition, the present data of proposed roughness were also compared with data of various roughness available in the literature. It was found that the maximum thermo-hydraulic perfor-mance parameter of the proposed roughness texture is higher than other shapes of roughness texture. It was also found that the combination of double-glass cover and double-pass arrange-ment with the proposed roughness geometry increases the efficiency of the solar air heater at least by one order of the present solar air heating system.

Design and Simulation Analysis of Stator Slots for Small Power Permanent Magnet Brushless DC Motors

With the development of power electronics technology, permanent magnet brushless DC motors have developed rapidly and are now widely used in electric vehicles, flywheel energy storage, rail transit, and other applications. The stator slot structure is one of the main factors affecting the performance of the motor. A low-power permanent magnet brushless DC motor was selected as the research object, and the finite element analysis method was used to study the effects of different slot and pole combinations and stator slot types on the cogging torque, reluctance torque, and back electromotive force of the permanent magnet brushless DC motor. The influence of the stator slot structure of the motor on the performance of the motor was analyzed, and the optimal slot-pole combination and stator slot type were determined. The results showed that the cogging torque of the 2-stage 24-slot motor was 14 mN·m, and the reluctance torque was 75 mN·m. The cogging torque and reluctance torque were the smallest, and the back electromotive force waveform was similar to a trapezoidal wave. The motor cogging torque of the pear-shaped round slot was the smallest, with a value of 460 mN·m, and the motor reluctance torque of the pear-shaped trapezoidal slot was the smallest, with a value of 1.2 N·m. The back electromotive force waveforms of the motors with four different stator slot types were similar.

Estimation of Surface Dose in the Presence of Unwanted Air Gaps under the Bolus in Postmastectomy Radiation Therapy: A Phantom Dosimetric Study.

The aim of this study is to design and fabricate a thorax phantom with irregularly shaped trapezoidal slots across the left side of the chest wall, allowing for the creation of unwanted air gaps under the bolus. Surface dose (Dsurf) measurements were made with Gaf Chromic EBT3 films at air gaps (0.0, 5.0, 10.0 and 15.0 mm) under gel bolus of thickness (5.0 mm & 10.0 mm), for 3DCRT technique (2 and 3 field) with clinical 6 MV photon beam under uniform and non-uniform air gap condition. The obtained values were compared with TPS estimated ones. In the presence of 15.0 mm uniform air gap, the mean estimated and measured Dsurf values with two and three field techniques decreased by 14.0 % to 15.2% and 14.7% to 17.4% under 5.0 mm and 10.0 mm bolus applications respectively. In presence of non-uniform air gap condition, the effect on Dsurf was minimal (3 to 3.5%) compared with the uniform air gap condition. Based on the study's findings, it is recommended that when using bolus in clinical radiotherapy applications, special care be taken to avoid unwanted air gaps under the bolus in order to achieve a uniform surface dose across the treatment region, where a customized 3D printed bolus may be a better option.

Investigation of the film-cooling and flow characteristics of trapezoidal slot scheme on the blade tip with partial pressure side squealer in transonic flow

The present work first introduces and studies the blade tip with a discrete trapezoidal slot scheme. The film-cooling characteristics of the discrete trapezoidal slot scheme on the blade tip with the partial pressure side squealer and full suction side squealer is experimentally investigated by the Pressure Sensitive Paint technique in transonic flow. The effects of the mass-flow-ratio and tip-clearance-gap are investigated, and the experiment is carried out at four mass-flow-ratios of 0.1% + 0.05%, 0.14% + 0.07%, 0.17% + 0.085%, and 0.21% + 0.105% and three tip-clearance-gaps of 0.7%, 1.1%, and 1.5%. The cascade exit Mach numbers is 1.05. The flow characteristics of the blade tip is studied by the calculation. The results indicate that the coolant can cover the whole blade tip bottom surface at the tip clearance of 1.5% and high mass-flow-ratios; With the tip-clearance-gap increasing, the adiabatic film effectiveness near the squealer rim of the suction side is significantly improved; The adiabatic film effectiveness near the leading edge at the small tip-clearance-gap is higher than that at the large tip-clearance-gap under the mass-flow-ratio of 0.1% + 0.05% condition due to the mainstream-blockage-effect; With the tip-clearance-gap increasing, the high aerodynamic loss coefficient region is significantly enlarged. At three tip-clearance-gaps, changing the mass-flow-ratio shows a slight effect on the aerodynamic loss coefficient distribution.

MTM- and SIW-Inspired Bowtie Antenna Loaded with AMC for 5G mm-Wave Applications

This paper investigates a feasible configuration of slotted bowtie antenna based on MTM and SIW properties for 5G millimeter-wave applications. To realize the proposed slotted bowtie antenna in a compact dimension with high performances, the MTM and SIW concepts are implemented by applying the trapezoidal slots on the top surface of the antenna and metallic via holes through the substrate layer connecting the top surface to the ground plane. The antenna has been fed with a simple microstip-line which is connected to a waveguide-port. It is shown that the slotted bowtie antenna with a small dimension of 30 × 16 × 0.8 mm3 operates over a measured wideband of 32–34.6 GHz with the fractional bandwidth, average gain, and radiation efficiency of 7.8%, 3.2 dBi, and 50%, respectively. To improve the antenna's performance, the artificial magnetic conductor (AMC) properties have been employed on the ground plane by loading vertical and linear slots with various lengths. The AMC slots are aligned under the trapezoidal slots on the top surface to transfer the maximum electromagnetic signals to them for optimum radiation. The proposed method enlarges the antenna’s effective aperture area, keeping constant its physical dimensions. The proposed AMC-loaded antenna covers wider frequency range of 30–37 GHz in measurement, which corresponds to 21% fractional bandwidth. The average experimental gain and radiation efficiency have been increased to 5.5 dBi and 66.5%, respectively, which illustrate the effectiveness of the proposed AMC-loaded antenna. The results confirm that the proposed slotted bowtie antenna with advantages of compact dimension, wide bandwidth, high gain and efficiency, low profile, being cost-effective, simple design, and easy fabrication process, which makes it applicable for mass production, can be a good candidate for 5G millimeter-wave applications.

Asymmetrically fed trapezoidal superwideband pattern diversity antenna

In this paper, a trapezoidal antenna element and its pattern diversity configuration for superwideband applications are presented. The antenna consists of a modified trapezoidal slot loaded modified trapezoidal radiator asymmetrically fed by a tapered feedline and notch loaded modified semi-circular ground plane. An operating bandwidth of 2.6 THz to more than 60 THz is achieved for both configurations. The dimensions of the antenna element and diversity configuration are 24 × 41.8 um2 and 41.8 × 65.8 um2 respectively. For single element, a peak realized gain of 17 dB is observed. For diversity configuration, an intra-element isolation of more than 20 dB in most of the operating band is achieved. The proposed antenna element and diversity configurations are compact and have wider bandwidth in comparison to previously reported structures.

A SIW Horn Antenna without Broad Wall Loaded with Trapezoidal Air Slot

In this paper, a SIW horn antenna without broad wall loaded with trapezoidal air slot is proposed, processed, and tested. Based on the SIW horn antenna, this antenna strips off the wide wall at the horn diameter, introduces surface waves on the surface of the dielectric substrate, and improves the impedance matching between the antenna and free space. Further, trapezoidal air slots are loaded on the exposed dielectric substrate, gradually changes the dielectric constant of the dielectric substrate, so that the dielectric constant of the dielectric substrate can get closer to which of air, and the working bandwidth can be further expanded. The actual measurement results show that the working bandwidth of the antenna is 15.2-38GHz, the relative bandwidth reaches to 85.7%, and the maximum gain in the band is 9.1dBi.

Design of miniaturized super wideband printed monopole antenna operating from 0.7 to 18.5 GHz

A design of compact Super-Wide Band (SWB) antenna with enhanced- bandwidth for wireless application is presented in this article. The proposed structure has fusion geometry of circular, square and trapezoidal slots on the rectangular radiator with a defected ground plane being used to enhance the VSWR bandwidth. Rectangular and trapezoidal-shaped slots are added in the ground plane to enhance the impedance bandwidth towards the lower cut off frequency. The proposed antenna has VSWR ≤ 2, average gain of 4.68 dBi, radiation efficiency of ≥ 83, fractional bandwidth (FBW) of 185.41%, and good pattern characteristics are achieved throughout the band. Moreover, the proposed SWB antenna is implemented in two ports multiple-input and multiple-output (MIMO)/diversity antenna. The diversified performances of MIMO antenna are calculated and it is observed that the proposed system has an isotropic radiation pattern. Four different configurations of MIMO antennas are designed and good isolation is achieved from port-to-port. The fabricated antenna has good agreement between simulated and measured results. The proposed antenna finds its applications in a wide range of UWB, K and Ku band portable devices.

Beam steering of a single nanoantenna.

Nanoantennas play an important role as mediators to efficiently convert free-space light into localized optical energy and vice versa. However, effective control of the beam direction of a single nanoantenna remains a great challenge. In this paper, we propose an approach to steer the beam direction of a single nanoantenna by adjusting two antenna modes with opposite phase symmetry. Our theoretical study confirmed that the combination of even- and odd-symmetric modes with a phase difference of π/2 enables effective beam steering of a single nanoantenna whose steering angle is controlled by adjusting the amplitude ratio of the two antenna modes. To implement our theory in real devices, we introduced asymmetric trapezoidal nano-slot antennas with different side air-gaps of 10 and 50 nm. The trapezoidal nanoantennas can simultaneously excite the dipole and quadrupole modes in a single nanoantenna and enables effective beam steering with an angle of greater than 35° near the resonance of the quadrupole mode. In addition, the steering angle can also be controlled by adjusting the degree of asymmetry of the trapezoidal slot structure. We believe that our beam steering method for a single nanoantenna will find many potential applications in fields such as imaging, sensing, optical communication, and quantum optics.

A Low-Profile Dual-Band Dual-Polarized Antenna With an AMC Reflector for 5G Communications

A low-profile dual-band dual-polarized antenna with an artificial magnetic conductor (AMC) reflector is proposed for 5G communications. The antenna consists of a pair of crossed dual-polarized dual-band bowtie dipoles and a dual-band AMC reflector. By introducing trapezoidal slots and U-shaped slots on the bowtie dipoles, miniaturization and dual-band characteristics are achieved. Moreover, T-shaped feeding structures are utilized to broaden the bandwidth of the bowtie dipoles. By adopting a dual-band AMC reflector instead of a conventional perfect electric conductor (PEC) reflector, the distance between the radiator and the reflector can be reduced from $0.25\lambda _{0}$ to $0.08\lambda _{0}$ (where $\lambda _{0}$ is the free-space wavelength at 3.5 GHz). The radiator can maintain the impedance bandwidth and a high gain can also be achieved, even if it is close to the AMC reflector. A geometrical optics model is used to explain the mechanism of the AMC. The optimal parameters of the AMC depend on the antenna operating frequency and the distance between the radiator and the reflector. Measurements show that the proposed dual-band antenna has an impedance bandwidth of 19.8% (3.14-3.83 GHz) and 13.2% (4.40-5.02 GHz), covering the sub-6 GHz frequency spectra of 5G mobile communications. The peak gain is 7.1 dBi in the lower band and 8.2 dBi in the upper band. Port isolation better than 20 dB is achieved. The proposed antenna can be used alone for 5G indoor base station, or as the element of an array for 5G outdoor base station.

Estimating the mixture friction factor for the dense-phase transport of particulates in horizontal pipes with inner longitudinal spiral slots

This research was devoted to establishing a dimensionless model for estimating mixture friction factor based on the Buckingham Theorem. An experimental test-rig with conveying pipeline of 40 mm I.D was designed, assembled and used to collect the data needed to model the mixture friction factor. Experiments were carried out in four levels of slot depths (0, 0.35, 0.55 and 0.9 mm), three levels of air pressure (100, 200 and 300 kPa) and three pipeline lengths (3, 6 and 9 m). Conveying tests with three particulate materials of mung bean, corn, and polyethylene pellets were completed using three replications. Static air pressure across the conveyor, mass flow rate of discharge solids and inlet air mass flow rate were measured during the tests. The model developed can estimate the mixture friction factor within the range of variables studied. The comparison between predicted and measured mixture friction factor showed no significant difference. According to values of R 2 , RMSE, reduced chi-square and MRD parameters, mixture friction factor modelling of the pneumatic conveyor had good accuracy. Other results showed that the mixture friction factor was 65% less than that of pipelines with inner trapezoidal slots studied earlier, therefore lower upstream pressure was required for dense-phase pneumatic conveying of particulate materials in the new conveyor. The developed model showed acceptable error in predicting pressure drop from the experimental data.

Mesh-Grounded Monopolar Hexagonal Microstrip Antenna for Artillery-Launched Observation Round

This paper presents a novel low-profile microstrip antenna with an omnidirectional radiation pattern for an artillery-launched observation round. The proposed antenna consists of one centered hexagonal patch for a feeding network and six periodic arrays of a trapezoid patch for a radiator. The trapezoid patch is equal to a half-sized hexagonal patch based on geometrical symmetry. A gap-coupled one-hexagonal patch and six trapezoid patches are supported on a nonfundamental TM02 mode for vertically polarized omnidirectional radiation patterns. In addition, a meshed ground structure for the proposed antenna is employed to improve the impedance bandwidth. The thin metal wires that are formed by the meshed ground structure yield six trapezoid slot arrays for the feeding network and three triangular slot arrays for the radiator on the ground plane. To verify the feasibility of the meshed ground structure, the mesh width, denoted by w, was investigated theoretically and optimized carefully to enlarge the impedance bandwidth of the proposed antenna. Finally, the proposed antenna, with a mesh width of 0.2 mm, successfully demonstrated excellent monopolar radiation at a resonant frequency of 5.84 GHz, a realized gain of 5.27 dBi, and an impedance bandwidth of 452 MHz from 5.583 GHz to 6.035 GHz with respect to 7.78% at a center frequency of 5.809 GHz.

Быстроходные электромеханические преобразователи энергии: оптимизация геометрии активной зоны ротора на основе требований механической прочности

AC machines with the nominal rotation frequency higher than 3000 rpm find increasingly growing use. These machines are made with bulky rotors for ensuring mechanical strength, and the slots in them are made with a rectangular shape, usually with a wedge (for retention of the field winding or permanent magnets, or short-circuited winding bars), or with a trapezoid shape. An investigation of the bulky rotor tooth zone design has shown that, given a specified stress at the tooth base, the maximal area of rotor slots with their optimal height can be obtained. In this way, the maximum MMF of the rotor (at the specified current density) and, hence, the maximum value of the machine nominal power are achieved. In the article, the problem of determining the optimal tooth zone geometry in a bulky rotor is solved for the general case of using a trapezoid slot with any ratio of the slot widths at the base and under the wedge, and with any value of the averaged specific mass. The problem has been solved for arbitrary runaway rotation frequency (n≥3600 rpm). An example of optimizing the rotor tooth zone is given.

An Insight into Impact of Partial Ground and Dual Trapezoidal Slots on Bandwidth and Gain considerations for a Microstrip Antenna Array for WiMax Application

In this work, design and analysis of microstrip patch antenna is carried out. A (2 X 1) antenna array is considered, with dimensions (W x L) as 35.11 mm x 27.13 mm. The dielectric substrate is taken to be FR4 epoxy with dielectric constant as 4.3 and loss tangent of 0.02. Dual trapezoidal slots are introduced to improve the gain considerations for the considered antenna array. The simulations are carried out and it is observed that the gain is improved. As a second stage in the work, to improve the bandwidth of operation for the dual trapezoidal antenna array, the concept of partial ground is taken into consideration. The simulations are carried in HFSS. It is found out that the introduction of partial ground improved the bandwidth of the antenna structure considered while preserving the gain to the maximum extent possible. The gain was found to be 7.0875 dB with centre frequency 2.4020 GHz. The frequency range below -10dB for the considered antenna array structure with partial ground was around 2.3 GHz to 2.6 GHz. This range is utilized in the WiMax application which covers the frequency ranges (2.3 GHz to 2.4 GHz) and (2.496 GHz to 2.690 GHz).

Analytical Modelling of Open-Circuit Flux Linkage, Cogging Torque and Electromagnetic Torque for Design of Switched Flux Permanent Magnet Machine

Magnetic saturation and complex stator structure of Switched Flux Permanent Magnet Machine (SFPMM) compels designers to adopt universally accepted numerical method of analysis i.e. Finite Element Analysis (FEA). FEA is not preferred for initial design due to its computational complexity and is time consuming process because of repeated iterations. This paper presents an accurate analytical approach for initial design of proposed twelve-stator-slot and ten-rotor-tooth (12/10) with trapezoidal slot structure SFPMM. Air-gap Magnetic Equivalent Circuit (MEC) models with Global Reluctance Network (GRN) methodology is utilized for calculation of open-circuit flux linkage. Fourier Analysis (FA) for cogging torque, and Maxwell Stress Tensor (MST) method for electromagnetic torque where radial and tangential components of the air-gap flux density are produced by the currents flowing in three phase armature winding. Analytical predictions are validated by FEA utilizing JMAG software and shows errors less than ~2% for open-circuit flux linkage, ~4.2% for cogging torque, and ~2% for average electromagnetic torque.

Design and analysis of a novel dual trapezoidal slot‐based rectangular microstrip antenna for wide area network using WiMax application

AbstractIn this article, a novel microstrip rectangular patch antenna is designed which involves dual trapezoidal slots. The proposed microstrip patch antenna is used in the S band range of 2–4 GHz, used for various wireless applications. The resonant frequency is calculated theoretically at 3.5 GHz with patch dimensions being 25.4 mm × 19.4 mm in terms of width × length (in mm). Using the theoretical parameters, the proposed patch antenna is designed using HFSS software. The results are also compared to the conventional regular patch antenna. The results show that the proposed patch antenna with dual trapezoidal slot has better return loss and VSWR and can be used for WiMax application services. The observations and findings are tabulated.

English

In this paper, a multiband printed antenna has been proposed. The antenna structure is inspired from that of the classical multi-cavity magnetron resonator. The antenna structure is composed of a slot annular ring structure etched on the ground plane of a substrate. The outer circle of the annular ring is loaded with radially arranged small trapezoidal slots. While on the other side of the substrate, the antenna is fed with a 50-Ohm microstrip line. A parametric study has been conducted to explore the effect of the different antenna dimensions on its performance. The results show that the proposed antenna offers triple band resonant responses with considerable frequency ratios of f3/f2, and f2/f1. Measured results of the input reflection coefficient responses of a fabricated prototype are found to agree well with the theoretical findings. The antenna has an input reflection coefficient response enables it to serve the 2.4/5.2 GHz WLAN and the 3.5/4.5 GHz WiMax applications. Besides, the antenna offers reasonable radiation characteristic with acceptable values of the gain throughout the four resonant bands.

A Multiband Printed Slot Antenna Loaded with Trapezoidal Slots for WLAN and WiMax Applications

In this paper, a multiband printed antenna has been proposed. The antenna structure is inspired from that of the classical multi-cavity magnetron resonator. The antenna structure is composed of a slot annular ring structure etched on the ground plane of a substrate. The outer circle of the annular ring is loaded with radially arranged small trapezoidal slots. While on the other side of the substrate, the antenna is fed with a 50-Ohm microstrip line. A parametric study has been conducted to explore the effect of the different antenna dimensions on its performance. The results show that the proposed antenna offers triple band resonant responses with considerable frequency ratios of f3/f2, and f2/f1. Measured results of the input reflection coefficient responses of a fabricated prototype are found to agree well with the theoretical findings. The antenna has an input reflection coefficient response enables it to serve the 2.4/5.2 GHz WLAN and the 3.5/4.5 GHz WiMax applications. Besides, the antenna offers reasonable radiation characteristic with acceptable values of the gain throughout the four resonant bands.

A multiband reconfigurable slot antenna for wireless applications

This research presents a novel four band frequency reconfigurable antenna for 1.6 (Global Navigation Satellite system (GNSS)), 2.5 (Lower Worldwide Interoperability for Microwave Access (WiMAX)), 5.8 (Wireless local area network (WLAN)) and 9.8 GHz (X-band) frequency bands. The antenna has a compact size of 0.18λ0×0.18λ0×0.0096λ0 at lower resonance of 1.8 GHz and is printed on FR4 material with height (h) = 1.6 mm, dielectric constant ((εr)=4.4 and loss tangent (δ) = 0.02. Multiband phenomenon in the antenna is achieved by etching trapezoidal slot in the radiating monopole and rectangular slots in the ground plane. Frequency reconfiguration in the proposed structure is achieved by placing PIN diode switch between rectangular slot placed in the ground plane. During OFF state, the antenna exhibit quad band with S11 < −10 dB bandwidth of about 11.1% (1.7–1.9 GHz), 10.52% (2.7–3.0 GHz), 5.52% (5.6–5.9 GHz) and 9.3% (9.2–10.1 GHz) under simulation and of about 6.06% (1.6–1.7 GHz), 11.76% (2.4–2.7 GHz), 3.44% (5.7–5.9 GHz) and 6.25% (9.3–9.9 GHz) in measurement respectively. During ON state of PIN diode, the antenna operates at dual bands (5.8 and 9.5 GHz) with S11 < −10 dB bandwidth of about 3.44% (5.7–5.9 GHz) and 7.65% (8.8–9.5 GHz) under simulation and of about 8.54% (5.6–6.1 GHz) and 3.17% (9.3–9.6 GHz) in measurement respectively. The antenna exhibits good impedance matching, radiation characteristics and gain across their operational bandwidths.