Slot Design Research Articles

Mathematical and Computer Simulation of Hex Head Screws for Implementation on a 3D Printer

In this paper, based on the R-functions theory, methods have been developed and equations have been constructed for the 3D printing of hex-head screws with Bristol, Pentalobe, Polydrive and other types of screw slots. Such screws are used both in personal computers and other high-end equipment. The Bristol slot has four or six radial grooved beams. The advantage of the design of this slot is the correct perpendicular, rather than tangential, vector of force application when the slot is rotated by a tool, which minimizes the risk of stripping out the slot. For this reason, the Bristol slot is used in soft metal screws. Compared to the internal hex, the Bristol slot allows a noticeably higher torque, only slightly higher than that of the Torx slot. This type of slot is used in aviation, high-end telecommunications equipment, cameras, air brakes, agricultural equipment, astronomical equipment, and foreign military equipment. Variations with a pin in the center are found in game consoles to prevent the use of a flat-blade screwdriver as an improvised key. The Pentalobe slot is a five-point slot designed by Apple and used in its products to limit unauthorized disassembly. It was first used in mid 2009 to mount MacBook Pro batteries. Its miniature version was used in the iPhone 4 and later models, in the MacBook Air (available since late 2010 models), and the MacBook Pro with Retina screens. The Polydrive slot is a starlike slot with rounded star points, used in the automotive industry for applications requiring high tightening torque. The Torq-set slot is a cross slot for fasteners requiring high tightening torque. The grooves are slightly offset, not intersecting at one point. Fasteners with this type of slot are used in military aviation, for example, in E-3, P-3, F-16, Airbus, Embraer, and Bombardier Inc. The Phillips Screw Company owns the trademark and manufactures fasteners with this type of slot. The slot design standards are National Aerospace Standard NASM 3781 and NASM 4191 for the ribbed version. The resulting equations for the surfaces of screws were checked during the modeling of the screws before 3D printing. The 3D printing technology allows us to reduce the cost and labor intensity of manufacturing products, including complex slot screws. The analytical recording of designed objects makes it possible to use alphabetic geometric parameters, complex superposition of functions, which, in turn, allows us to quickly change their design elements. The positivity property of the constructed functions at the internal points of an object is very convenient for the implementation of 3D printing.

Substrate integrated waveguide leaky wave antenna with circular polarization and improvement of the scan angle

AbstractIn this paper, a leaky wave antenna is presented based on the substrate integrated waveguide structure. The proposed antenna has a periodic structure with a combination of rectangular and H‐shaped slots on the top of the antenna. By providing this new design for slots, a better angular scanning achieved rather than the previous designs from broadside to end‐fire, so that with this design, the leaky wave antenna can scan from 2.5 to 87° by changing the feeding frequency, which is the highest scanning angle relative to the design of uniform rectangular slots, the butterfly shaped slots and the H‐shaped slots. The proposed antenna was designed to have circular polarization in the entire operating frequency range.

Aerodynamic Analysis and Optimization of Embedded Slot for Smooth Morphing Trailing Edge

Smooth morphing trailing edge (SMTE) has been receiving more attention as a new wing design concept in the past few years due to its high potential in reducing cruise drag, structural weight, aerodynamic noise, and fuel consumption. Apart from the necessity of using new flexible materials and compact actuation mechanisms, it is also faced with the challenge of providing sufficient lift as conventional high-lift devices did during low-speed flight phases. Insufficient low-speed aerodynamics could compromise aircraft takeoff and landing performance. In light of this, a concept of the embedded slot is proposed for use with SMTE. To study the full benefits of the embedded slot, constrained single-objective optimization is first conducted on a two-dimensional airfoil using kriging surrogate models built from Reynolds-averaged Navier–Stokes solutions. The final optimal results show that the maximum lift coefficient from SMTE with a slot is only slightly lower than that of a typical three-element Fowler flap. The parametric analysis showed the strong coupling effects on the aerodynamic performance of slot entry and exit geometry dimensions. Based on the optimal two-dimensional slot design, computer-aided design models of three-dimensional SMTE configurations are built and analyzed. Comparisons among High-Lift Common Research Model SMTEs with and without slot show that the embedded slot improved high-lift performance. After introducing the embedded slot, the maximum lift coefficient for SMTE is raised by 7.9% from 2.277 to 2.457, and the stall angle is increased by 2 deg. This is in comparison with the maximum lift coefficient of 2.572 for the conventional Common Research Model Fowler flap configuration. The results demonstrated the benefits of introducing embedded slot into SMTE for future high-lift designs.

Exploiting the Coandă effect for wind-driven reciprocating RO desalination

The urgent need for fresh water remains a strong driver for reverse-osmosis (RO) desalination, but present-day systems are energy-inefficient and produce significant green-house gas emissions. This motivated our research, which introduces and investigates a novel concept for wind-driven RO desalination. It is based on the Coandă effect, applied periodically by blowing slots on a spring-stabilized vertical cylinder, to produce reciprocating motion that drives RO piston pumps. The Coandă-based Reciprocating (CoRe) system converts wind energy directly to mechanical pumping energy thereby eliminating generator and motor inefficiencies. A small-scale (2-m high) system was constructed and evaluated in an open-jet wind tunnel. It delivered 2–6 bars of water pressure with a net power efficiency of up to 4% depending on wind speed and circulation control parameters. A mathematical model of the system produced excellent correspondence with the experimental data. It was determined that the experimental setup and slot design biased the results negatively and model predictions based on published Coandă data indicated net power efficiencies up to 20%. It was also determined that the slot design details had a decisive effect on performance.

A Novel Transmission Policy for Intelligent Reflecting Surface Assisted Wireless Powered Sensor Networks

This paper proposes a novel transmission policy for a wireless powered sensor network (WPSN) assisted by an intelligent reflecting surface (IRS) to enhance the performance of wireless energy transfer (WET) and wireless information transfer (WIT) with certain phase shifts. To achieve its self-sustainability, IRS collects energy from the energy station to support its own control circuit operation. Our proposed policy for the considered WPSN is called IRS assisted harvest-then-transmit time switching (IRS-HTT-TS), which is capable to schedule the transmission time slots by switching between energy collection and energy reflection modes. We provide a joint design of the transmission time slots, the power allocation as well as the discrete phase shifts of the WET and WIT, aiming to maximize the system sum throughput. This formulates a problem as a mixed-integer non-linear program (MINLP), which is NP-hard and non-convex. To effectively solve this problem, we first relax it to the one with continuous phase shifts, and then propose a two-step approach and decompose the original problem into two sub-problems. We address the first sub-problem in closed form with respect to the phase shifts of the WIT. For the second sub-problem, we apply the Lagrange dual method and Karush-Kuhn-Tucker conditions to derive the optimal closed-form transmission time slots, power allocation, and phase shift of the WET, respectively. The optimal discrete phase shifts can be obtained by quantizing the continuous values. Numerical results demonstrate the effectiveness of the proposed policy and validate the beneficial role of the IRS in comparison to the benchmark schemes.

Reduction of Torque Ripple and Rotor Eddy Current Losses by Closed Slots Design in a High-Speed PMSM for EHA Applications

Reduction of Torque Ripple and Rotor Eddy Current Losses by Closed Slots Design in a High-Speed PMSM for EHA Applications

Optimum Slot and Pole Design for Vibration Reduction in Permanent Magnet Synchronous Motors

Permanent Magnet Synchronous Motors (PMSMs) are increasingly being used and are required to satisfy noise and vibration specifications. Thus, it is necessary to develop design guidelines for electric motors that consider vibration response as a key output of the design. This work shows the influence of the main design parameters regarding PMSMs: the number of slots and the number of poles. First, the influence of the number of slots in the natural frequencies is analysed by Finite Element calculations, which are experimentally verified. Then, the analytical calculation of the vibration response is explained. This is applied for several combinations of the number of slots and the number of poles, and the results are compared. Considering the analytical development, a procedure to choose the most adequate combination of the number of slots and poles is proposed. The analytical predictions are validated according to experimental measurements in two machines.

A CFD Simulation on the Performance of Slotted Propeller Design for Various Airfoil Configurations

The usage of slots has gained renewed interest in aerospace, particularly on propeller design. Most of the works have focused on improving the aerodynamic performance and efficiency. Modern research on propeller design aims to design propellers with high thrust performance under low torque conditions without any weight penalty. Although research on slotted design has been done before, none has been done to understand its impact on different airfoils on the propeller blade. Thus, this study aims to provide extensive research on slotted propeller design with various airfoil of different properties such as high Reynolds number, low Reynolds number, symmetrical, asymmetrical high lift, and low drag. This work has been investigated using computational fluid dynamics method to predict propeller performance for a small-scale propeller. The slotted blade designs' performance is presented in terms of thrust coefficient, power coefficient, efficiency, and thrust to power ratio. Here, the slotted APC Slow Flyer propeller blade's performance has been investigated for diverse types of airfoils with the shape and position of the slot is fixed which is a square-shaped at 62.5% of the chord length. The flow simulations are performed through three-dimensional computational fluid dynamic software (ANSYS Fluent) to determine the thrust coefficient, power coefficient, efficiency, and thrust to power ratio measured in advancing flow conditions. Findings show that the slotted propeller design composed of symmetrical, high Reynolds number, high lift airfoils can benefit the most with slots' implementation. These improvements were 19.49%, 69.13%, 53.57% and 111.06% in terms of thrust, power, efficiency and trust to power ratio respectively.

Effects of Geometric Dimension Variations on Efficiency of 3-phase Squirrel Cage Induction Motors Considering Economic Evaluation

There are different approaches to improve the efficiency of induction motors. In this paper, the considered approaches include, design of the rotor slot, rotor slot shape, and stator and rotor diameters which are applied on a 30-kW 3-phase, 4-poles, 48-stator slots, and 44-rotor squirrel cage induction motor. Comparison of analytical, simulation and experimental results confirm the proposed FEM-based model of set-up induction motor. The sensitivity analysis of efficiency considering the variations of rotor slot dimensions, stator outer diameter, and stator and rotor diameters have been applied on the case-study. The results of the GA-based optimal design of the rotor slot dimensions showed a 0.32% improvement in motor efficiency. On the other hand, changing the motor core diameters has more effects on motor efficiency so that, when the stator and rotor outer diameters were increased simultaneously, the efficiency was increased by 0.55%. However, if the stator outer diameter just increased, motor efficiency increased by 0.76%. Finally, the economic evaluation was accomplished to validate the optimal approach of motor design for three cases of electricity consumption per kWh.

Fatigue Analysis and Structural Optimization Design of the Slot of Knotted Frame of the Square Baler

The frame is a key part to ensure the reliability and life of the knotting device of the square bale baler, and it is also the difficulty of localizing the knotting device. The inner wall of the frame slot of the frame is at a right angle structure, and the stress concentration is obvious. Under the impact load, the stopper will cause premature shear failure, delay the timing of forage bale, increase maintenance costs, and reduce the operating efficiency of the baler. This paper analyzes the failure characteristics of the D-type knotter frame slot, uses ANSYS-nCode joint method to simulate the fatigue life of the knotter frame slot, and uses the response surface method to optimize the design of a U-shaped slot. The simulation results show that when the radius of the U-shaped slot is 2mm and the gap between the bottom of the slot and the first rope clearing piece is 1mm, the fatigue life of the U-shaped slot increases. This research is of reference value to improve the fatigue performance of the knotter frame and enhance the durability of the knotter.

Design and Analysis of Dual Frequency Microwave Moisture Sensor Based On Rectangular Microstrip Antenna

The two proposed design microstrip patch antenna as a sensor are analysed with the help of CST software for detecting the moisture. The proposed design is T-Shape rectangular shape with slotted in the ground plane and without slotted in the ground plane. It is operated at two frequencies 2.2GHz and 4.6GHz. It is designed on FR4 substrate and thickness is 1.676mm. The moisture can be detected with the help of oven drying technique. It will be helpful for measuring the moisture content. This technique is very easy, less time consuming, versatile and compact. The ground parameter of the proposed design is 20mm, as well as the length and width of the patch dimensions are 15mm and 10mm, which will be very portable. The designs is simulated on CST software and gets the good return loss, which is -16dB at 2.2GHz and -45dB at 4.6GHz. The gain is also the important parameter of the sensor; the proposed slotted ground plane design gain is 4.99dB at 4.6GHz as well as without slotted ground plane design gain is 5.1dB at 4.6GHz. It will be fabricated and measure the moisture in rice grains with the help of vector network analyser. The calibration equation and regression equation is also the important role of detecting the moisture content.

Design, Analysis, and Optimization of the Array of Axial Rectangular Slots on a Cylindrical Waveguide

In the current work, for the first time, the design equations for an array of rectangular slots axially placed on a cylindrical waveguide are driven and presented, making it possible to attain asymmetrical and non-broadside patterns with higher bandwidths. The method of least squares is then used for both the radiation pattern synthesis with the specified side lobe level and the array input impedance matching. For optimization, the error function comprised of the three terms of impedance matching, array pattern synthesis, and slot design equations is constructed. To minimize the error function, the genetic algorithm combined with the conjugate gradient method is utilized and the geometrical characteristic of the slots defined. This procedure increases the design speed and provides the means to synthesize any desired pattern for an array of axial rectangular slots on a cylindrical waveguide. Numerical and fabrication examples are presented as illustrations of the proposed synthesis method. The results of the proposed method are verified by using the commercial software High-Frequency Structure Simulator (HFSS) in comparison to measurement results obtained out of the proposed prototype of a fabricated antenna operating at the frequency of 9 GHz.

Numerical analysis on impact of choice of number of rotor slots on performance of three phase induction motor

Abstract This paper gives an insight of the geometrical configuration of a three phase induction motor based on classical design approach and has focused on the design of stator and rotor slots. A thorough investigation on the performance analysis of a sample motor is carried out using its finite element model, by varying the number of rotor slots. It explores the power, torque, current, speed, efficiency and power factor. In addition, the losses and torque ripple are also studied using equivalent circuit analysis and motion analysis respectively. For the chosen three phase induction motor, the optimum design parameters which provide a compromise between torque ripple and good overall performances, are recognized to be that for rotor slots 19. The performance of the motor is analysed for three different rotor bar materials namely, copper, aluminium and titanium. The simulation results show that the use of copper and aluminium as rotor bar material gives good efficiencies of 90.3% and 90.2% respectively. The efficiency of the motor with titanium rotor bars is only 75.8%. It is observed that, three phase induction motor with titanium rotor bars exhibits linear torque speed characteristics and good thermal stability. These findings can be adapted for the design of three phase induction motor for industrial applications based on their needs.

Design, Optimization and Prototype of a Multi-Phase Fractional Slot Concentrated Windings Surface Mounted on Permanent Magnet Machine

The multi-phase permanent-magnet motors are suitable choices for certain purposes like aircrafts, marine, and electric vehicles due to the fault tolerance and high-power density capabilities. The paper aims to design and prototype an optimized five-phase fractional slot concentrated windings surface mounted permanent magnet motor. To optimize the designed multi-phase motor, a multi-objective optimization technique based on the genetic algorithm method has been applied. The machine design objectives are to minimize mass and loss, subsequently, to determine the best choice of the designed machine parameters. Afterwards, 2-Dimensional Finite Element Method (2D-FEM) has been used to verify the performance of the optimized machine. Finally, the optimized machine has been prototyped. The results of the prototyped machine have validated the results of the theatrical analyses of the machine, and accurate consideration of the parameters improved the performance of the machine. &nbsp

Numerical simulation of the liquid film suction process through the slots of various geometry in the last stages of steam turbines

The liquid film suction process through the slot is considered. The stator blade row of the last stage of the steam turbine was used as an object of study. Based on the CFD modelling of two-phase flow in blades cascade the boundary conditions for slots modelling have been obtained. The numerical analyses of film removal were conducted in a domain including only a flow zone near the studied slot. The multi-phase VOF model was used to calculate the interaction between liquid and steam phases and model the interface evolution during the water removal process. Four different geometries of the slots were considered. For each of them, the unsteady calculations at two different operating regimes have been performed. The numerical results provide information about film suction details in a space of the slot. The behaviour of the film flow was analysed for each slot shape. The conditions of the film separation and its further breakup have been considered. For the studied slot designs efficiency analysis was performed. The results have shown how the way the liquid film moves in the slot effects on the removed water and steam mass flow rates.

Electric Field Evaluation Using the Finite Element Method and Proxy Models for the Design of Stator Slots in a Permanent Magnet Synchronous Motor

The efficiency of electric motors is being improved every day and projects with design variations can improve their performance. Among electric motors, the Permanent Magnet Synchronous Machine (PMSM) is being increasingly used, because of its growing use in electric vehicles. Simulating design variations using the Finite Element Method (FEM) can improve PMSM design, and by optimizing the parameters based on the FEM, even better results can be achieved. The design of the PMSM stator slots must be evaluated, as conductors are accommodated and an electrical potential is applied at this location. The FEM parameters are varied, and the results can be used to build an approximate model, known as a proxy model. The proxy model can then be used in a mathematical programming problem to optimize the design of stators that have less electric field in certain regions, thus reducing the chance of developing a failure. The results of the proposed methodology show that its application is promising for machine design and can also be used for the design of other systems.

Electromagnetic noise analysis and optimization for permanent magnet synchronous motor used on electric vehicles

PurposeElectromagnetic noise of permanent magnet synchronous motor (PMSM) seriously affects the sound quality of electric vehicles (EVs). This paper aims to present a comprehensive process for the electromagnetic noise analysis and optimization of a water-cooled PMSM.Design/methodology/approachFirst, the noises of an eight-pole 48-slot PMSM in at speeds up to 10,000 rpm are measured. Furthermore, an electromagnetic-structural-acoustic model of the PMSM is established for multi-field coupling simulations of electromagnetic noises. Finally, the electromagnetic noise of the PMSM is optimized by using the multi-objective genetic algorithm, where a multi-objective function related to the slot width of PMSM stator is defined for radial electromagnetic force (REF) optimization.FindingsThe experimental results show that main electromagnetic noises are the 8n-order (n = 1, 2, 3, …) and 12-order noises. The simulated results show that the REFs are mainly generated by the 8n-order (n = 1, 2, 3, 4, 5, 6) vibrations, especially those of the 8th, 16th, 24th and 32th orders. The 12-order noise is a mechanical noise, which might be caused by the bearings and other structures of the PMSM. Comparing the simulated results before and after optimization, both the REFs and electromagnetic noises are effectively reduced, which suggests that an appropriate design of stator slot is important for reducing electromagnetic noise of the PMSM.Originality/valueIn view of applications, the methods proposed in this paper can be applied to other types of PMSM for generation mechanism analysis of electromagnetic noise, optimal design of PMSM and thereby noise improvement of EVs.

A Study on the Rotor Design of Line Start Synchronous Reluctance Motor for IE4 Efficiency and Improving Power Factor

As international regulations of motor efficiency are strengthened, the line-start synchronous reluctance motor (LS-SynRM) is being studied to improve the efficiency of the electrical motor in industrial applications. However, in industrial applications, the power factor is also an important performance index, but the LS-SynRM has poor power factor due to the saliency characteristic. In this paper, the rotor design of LS-SynRM is performed to improve the efficiency and power factor. First, the barrier design is performed to improve the efficiency and power factor using the response surface method (RSM). Second, the rotor slot design is performed according to the length of bar for synchronization. Lastly, the rib design is performed to satisfy the power factor and the mechanical reliability. The final model through the design process is analyzed using finite element analysis (FEA), and the objective performance is satisfied. To verify the FEA result, the final model is manufactured, and experiment is performed.

An Improved Set of Design Criteria for Slotted Liners in Steam Assisted Gravity Drainage Operation

Slotted liners are widely used in steam-assisted gravity drainage (SAGD) wells to control sand production and sustain wellbore productivity. The slotted liner can provide desirable performance when appropriately designed. A literature review indicates a limited number of studies that offer design criteria specifically for SAGD wells. Moreover, past criteria seem to neglect some key factors, which may lead to inadequate slot design. This paper proposes a set of graphical design criteria for slotted liners in SAGD production wells, using prepacked sand retention testing (SRT) data. The SRT is designed to incorporate several essential factors that are not present in the past design criteria, such as slot density, steam breakthrough, and particle size distribution (PSD). The proposed design criteria are presented graphically for normal and aggressive conditions, where the aggressive condition accounts for the potential occurrence of the steam breakthrough. It is found that the upper bound of the design window is substantially lower for the aggressive condition due to the higher sand production after the steam breakthrough. The design criteria also indicate that the slotted liner is suitable only for the formations with low fines content.

Slot Design Optimization for Copper Losses Reduction in Electric Machines for High Speed Applications

The need of a wide operating range and a high power density in electric machines for full- and hybrid electric vehicles in traction applications has led to an increase in the operating frequency of the machine. When the electric frequency increases, the additional losses in stator windings become an issue and they have to be taken into account in the design of the electric machine. This issue is more critical when hairpin windings are employed, due to the the skin and proximity effects which produce increased copper losses. In this paper, the relationships between different stator slot parameters (tooth width, slot opening, etc.) and stator winding copper losses have been analysed in order to identify an optimal design of a single stator slot.