Torque Drop Research Articles

Investigation of a Modified Wells Turbine for Wave Energy Extraction

The Oscillating Water Column (OWC) is the most promising self-rectifying device for power generation from ocean waves; over the past decade, its importance has been rekindled. The bidirectional airflow inside the OWC drives the Wells turbine connected to a generator to harness energy. This study evaluated the aerodynamic performance of two hybrid airfoil (NACA0015 and NACA0025) blade designs with variable chord distribution along the span of a Wells turbine. The present work examines the aerodynamic impact of the variable chord turbine and compares it with one with a constant chord. Ideally, Wells rotor blades with variable chords perform better since they have an even axial velocity distribution on their leading edge. The variable chord rotor blade configurations differ from hub to tip with taper ratios (Chord at Tip/Chord at Hub) of 1.58 and 0.63. The computation is performed in ANSYS™ CFX 2023 R2 by solving three-dimensional, steady-state, incompressible Reynolds Averaged Navier–Stokes (RANS) equations coupled with a k-ω Shear Stress Transport (SST) turbulence model in a non-inertial reference frame rotating with the turbine. The accuracy of the numerical results was achieved by performing a grid independence study. A refined mesh showed good agreement with the available experimental and numerical data in terms of efficiency, torque, and pressure drop at different flow coefficients. A variable chord Wells turbine with a taper ratio of 1.58 had a peak efficiency of 59.6%, as opposed to the one with a taper ratio of 0.63, which had a peak efficiency of 58.2%; the constant chord Wells turbine only had a peak efficiency of 58.5%. Furthermore, the variable chord rotor with the higher taper ratio had a larger operating range than others. There are significant improvements in the aerodynamic performance of the modified Wells turbine, compared to the conventional Wells turbine, which makes it suitable for wave energy harvesting. The flow field investigation around the turbine blades was conducted and analyzed.

Investigation of Torque and Reduction of Torque Ripples through Assisted-Poles in Low-Speed, High-Torque Density Spoke-Type PMSMs

In this article, rotor designs utilizing assisted-poles are investigated for a high-torque density spoke-type permanent magnet synchronous machine (PMSM) with fractional slot concentrated winding (FSCW) to explore the rich air-gap magnetic field harmonics and torque generation mechanism. Due to their higher average torque output, spoke-type PMSMs with FSCW are increasingly used in high-torque density applications. However, slot harmonics generate torque ripples that are difficult to eliminate in FSCW spoke-type PMSMs. Removing slot harmonics from the stator or winding results in a large drop in torque since their winding factors are identical to those of the main harmonic. Therefore, rotor designs having assisted-poles (symmetrical and asymmetrical) are investigated in this work to mitigate slot harmonics and minimize torque ripples. Firstly, the air-gap flux density is analyzed for the machines having assisted-poles, and a model of interaction between the stator and rotor-MMF harmonics is created and validated through Finite element analysis (FEA) to analyze the torque production mechanism. In addition, an analytical relationship between the assisted-poles’ dimensions and the generated torque harmonics is proposed. Furthermore, a generalized torque ripple reduction concept for the FSCW spoke-type PMSM having asymmetrically designed assisted-poles is presented. The proposed design and optimization method are validated through analytical calculations and FEA simulations, and a brief comparative analysis is presented for the analyzed machine prototypes. It has been established that the machine designed by applying the proposed asymmetrical assisted-poles can achieve a reduction in torque ripples while also significantly lowering cogging torque in comparison to the conventional spoke-type PMSMs and other spoke-type PMSMs with rotor having symmetrical assisted-poles.

Thermal management improvement in electric vehicles through design optimization of coolant distributor valves

On battery electric vehicles a precise control of heat flows is required for passenger comfort and for both performance and safety of battery packs. This is typically achieved with a thermal management system which employs some type of liquid coolant to transfer heat. Coolant distributor valves are used to regulate coolant flows through the exchangers, for example to recover heat from hot sources, thus to increase vehicle energy efficiency. The development of this type of component is high-priced and the design is generally complex since several operating functions and manufacturing constraints should be satisfied. Despite this complexity and the positive impact such valves have on the thermal management of electric vehicles, a few works are currently available in the literature on design procedures for this component, where only a partial overview of the topic is provided and a comprehensive design methodology considering the effective operating conditions is still missing. In this work we construct a physical model of the valve for torque, internal leakage and pressure drop, and we build an optimization procedure to improve the global performance of the valve. We compare the obtained designs with a simpler approach that optimizes performance parameters independently and we show that designs which severely under-perform with respect to the uncontrolled performance parameters can be produced if an over-simplified design approach is followed. We then show with a global vehicle thermal model that the impact of valve design on global vehicle performance crucially depends on the thermal exchanges at vehicle level and, thus, on its operating conditions. In particular, the impact is considerable when mixing of cold and hot flows through the valve occurs. For a specific example vehicle evaluated in a type-3a cycle of the Worldwide Harmonized Light Vehicle Test Procedure, a valve determined with the proposed optimization procedure allows us to obtain in this condition an increase of about 1 km in the vehicle driving range with respect to a valve defined with the simpler approach.

Comparison of Effect of Conventional Fuel with Newly Developed Biofuel in Operation and Emission Conditions of Piston Combustion Engine

Abstract The present paper deals with the evaluation of the impact of newly developed biofuels together with a comparison with conventionally produced fuel, diesel, in terms of their impact on the technical and emission condition of a studied vehicle. The main energy and emission parameters of the internal combustion diesel engine were evaluated. For laboratory experiments, a discrete test method was used for comprehensive assessment, the procedure of which is described in the methodology of the paper together with a description of the measurement chain designed to achieve the determined results. The paper deals with the evaluation of the measured results of power, torque, consumption, and emissions such as CO2 and absorption coefficient. Among the technical parameters, the power and torque drop were observed for each biofuel. The decrease is attributed to lower values of calorific value, viscosity, and density. A positive effect was observed for the CO2 and absorption coefficient emission parameters, i.e., a decrease for each of the newly developed biofuels studied.

ANALYSIS OF THE POSSIBILITY OF APPLICATION OF HYDRAULIC MOTOR-WHEELS IN TRANSMISSIONS HIGH-SPEED TRACTORS

Goal. The purpose of the article is to assess the possibility of developing a hydraulic fluid power in accordance with the standard traction-speed characteristics of the KhTZ-17021 wheeled tractor with the of using gearless drives of the driving wheels. For this purpose, the calculation of the hydraulic fluid power of the wheeled tractor was performed when using the latest radial piston multi-cycle hydraulic motor-wheels with a wide range of rotation frequency and adjustment of the working volume. Research methodology. An analysis of the traction-speed characteristics of the KhTZ- 17021 wheeled tractor and, based on it, a review of modern high-torque radial-piston multi-cycle hydraulic motors from the point of view of meeting the characteristics of torque and rotation frequency with power limitations relative to the serial model in the full speed range of the tractor. The maximum values of the working volumes of the 4 driving hydraulic motor-wheels and the power supply pump of these hydraulic motors, the torque and pressure drop in the hydraulic drive are calculated, and the modes in which it is necessary to change the working volume of the hydraulic motors from the maximum to the minimum values to work out the traction-speed characteristics. A comparative analysis of radial-piston multi-cycle hydraulic motors was carried out, and for the hydromotor-wheel model MHP27 of the "Poclain Hydraulics" company, which was chosen for the study, the hydraulic principle diagrams were considered with the use of a hydraulic regulation system of four stages of the working volume in hydraulic motors, the use of combined parking and service brakes, as well as an anti-skid system using means of proportional electro-hydraulic automation. The results. High-torque hydraulic motor-wheels of the radial piston type were selected, which make it possible to ensure the operation of the tractor transmission without intermediate gearboxes between the hydraulic motors and wheel hubs, and the calculated value of the working volume of the axial piston pump, which ensures the operation of the tractor transmission in the full speed range. Based on the results of the calculations, it was established that the pressure in the hydraulic drive does not exceed 35 MPa, while values from 40 MPa to 50 MPa are achieved in modern pumps and hydraulic motors. The possibility of increasing the speed of the tractor from standard 35 km/h to promising 50 km/h is shown.

Flow characteristics of radial inflow in impeller rear cavity with baffle plate

The research purpose of this paper is to explore the influence of the baffle plate on the airflow in the rear cavity of the centrifugal impeller and optimize the performance of the secondary air system's air bleed section. In this paper, a comprehensive experimental study was carried out on the flow characteristics in the impeller rear cavity with baffle plate. The windage torque, flow structure and pressure drop between inlet and outlet were measured respectively. The experiment was carried out with the condition that the range of rotational Reynolds number was from 8.33 × 105 to 22.2 × 105 and the range of mass flow rate coefficient was from 0.92 × 104 to 2.92 × 104. The results show that the static cavity and the narrow stator-rotor cavity formed by the baffle plate effectively suppress the overall swirl coefficient in the cavity. Thus, the static pressure and total pressure drop in the rotor–stator cavity were reduced. The influence of the baffle plate on the windage torque of the rotary disk is related to the turbulence parameters. Under large turbulence parameters, the windage torque would be reduced with baffle plate, while under small turbulence parameters, the baffle plate would increase with baffle plate. In general, the baffle plate can improve the flow capacity and optimize the bleed air performance with proper structure and operation conditions.

The effect of emergency engine mode on the fuel consumption of a passenger car

Vehicles with a combustion engine are characterized by different fuel consumption. The aim of the research is to determine the fuel consumption during the operation of the internal combustion engine. Consumption is monitored in the state when the vehicle is without a fault and in the state when the vehicle's engine is operating in emergency mode. The aim of the research is to carry out driving tests on a personal vehicle. The course of fuel consumption is monitored at various sections. In the first section of the route, consumption is monitored when driving in an urban environment, the second section represents driving outside the village and the third section on the highway. With the help of a diagnostic device, it is possible to monitor current consumption data via the engine control unit. The emergency state of the engine is caused by the disconnection of the electronic component that enters into the preparation of the fuel mixture. The cause of such disconnection is the engine being put into emergency mode, which in real operation may mean a drop in engine power and torque. The measurement results actually show an increase in fuel consumption when the engine is working in emergency mode. However, consumption is lower when driving on a highway section. This is due to the vehicle not being able to reach the required speed. The research carried out thus points to the impact of operating a vehicle with an emergency engine condition in relation to fuel consumption.

CFD Simulation of Tesla Turbines Performance Driven by Flue Gas of Internal Combustion Engine

The reduced production of fossil energy, especially petroleum, has encouraged researchers to continuously increase the role of new and renewable energy as part of energy security and independence. A Tesla turbine is a device that can be used to recover wasted energy from exhaust gases, thereby increasing the overall energy use. The purpose of this study was to assess the performance of a Tesla turbine using various parameters such as engine speed, the gap between the disks, the diameter of the disks, and the number of disks. In this study, the performance of a Tesla turbine was simulated using computational fluid dynamics (CFD). The reference dimensions of this Tesla turbine are made with a slit diameter of 44 mm, a hole diameter of 10 mm, disc diameter of 140 mm, a disc width of 1.5 mm, a disc gap of 35 mm, a disc gap width of 4 mm, and a shaft length of 50 mm. The results of this study were in the form of torque and pressure drop values. In the variation of engine speed, the highest torque was at 1800 rpm with a torque value of 0.422 Nm, and the highest pressure drop was at 1800 rpm with a pressure drop value of 79161.5 Pa. In the disk gap variation, the highest torque is at a 7 mm disk gap with a torque value of 0.54 Nm and the highest pressure drop is at a 4 mm disk gap with a pressure drop value of 79161.5 Pa. In the variation of disk diameter, the highest torque was found on the disk with a diameter of 180 mm and a torque value of 0.831 Nm, and the highest pressure drop was on a disk with a diameter of 180 mm and a pressure drop value of 86753.5 Pa. In the variation of the number of disks, the highest torque was found at eight disks with a torque value of 0.765 Nm, and the highest pressure drop was found at eight disks with a pressure drop value of 82031.3 Pa. After performing this simulation, it can be concluded that at variations in engine speed, the higher the engine speed, the higher the value obtained and the variations in the disk gap, disk diameter, and number of disks. There are several values of torque that increase and decrease because the input value given cannot always increase the torque value in these variations.

Performance Improvement of the Hybrid Switch Reluctance Motor by Notching Method

Hybrid switch reluctance motors are the family of switch reluctance motors (SRMs) that attenuate the magnetic saturation and increase the air gap magnetic flux by exploiting permanent magnets. The permanent magnet auxiliary air gap flux can affect the average torque and ripple. Commonly, the torque ripples reduction comes with the average torque drop. In this paper, the torque ripple reduction and average torque improvement are achieved for a 6/10 pole hybrid switch reluctance motor by inserting two symmetrical notches on its rotor. Also, the lengths of magnet and rectangular notches are optimized by the finite element method and sensitivity analysis. The comparison of the optimized design with the initial one carried out by finite element proves the efficiency of the proposed model.

A Novel Algorithm for Hydrostatic-Mechanical Mobile Machines with a Dual-Clutch Transmission

Mobile machines using a hydrostatic transmission is highly efficient under lower working-speed condition but less capable at higher transport velocities. To enhance overall efficiency, we have improved the powertrain design by combining a hydrostatic transmission with a dual-clutch transmission (DCT). Compared with other mechanical gearboxes, the DCT avoids the interruption of torque transmission in the process of shifting without sacrificing more transmission efficiency. However, there are some problems of unstable torque transmission during the shifting process, and an excessive torque drop occurring at the end of the gear shift, which result in a poor drive comfort. To enhance the performance of the novel structural possibility of powertrain design, we designed a novel control strategy, which maintains the sliding in the torque phase and reduces the difference before and after the engagement, for the motor torque and the clutch torques during the shifting process, and then validated the control effect with model-based simulation. As a result, the control strategy employing clutch and motor torque control achieve a smooth shifting process since the drive torque is well tracked, and highly dynamical actuators are not required. As another benefit, only two calibration parameters are designed and actually needed to adjust the control performance systematically, even for any different sizes machines. Our research indicates the possibility to adopt dual-clutch in the field of construction machines.

PRODUCTION CHARACTERIZATION AND TESTING OF SOYBEAN BIODIESEL IN A DIESEL CYCLE ENGINE

The characteristics of the biodiesel produced by the transesterification reaction of soybean oil with anhydrous ethanol, catalyzed by sodium hydroxide and its thermo-oxidative stability, were investigated by thermal analysis and viscosity. It was analyzed density at 20 °C, sulfur content, cetane number, carbon residue, iodine index, acidity, sulphated ash, the total content of glycerin and unreacted fatty acids. The synthesis of biodiesel via ethanolic processed in a Pyrex glass reactor with 2/1 molar ratio triglyceride/anhy-drous ethanol and 1% of catalyst, 60 °C. After the reaction, the phases were separated and glycerin was removed. The biodiesel was washed with 0.1M HCl solution, at ~ 70 oC for neutralization. The physicochemical analysis, all parameters for biodiesel met the requirements of the ANP Technical Standards. From the produced biodiesel, binary mixtures were made with diesel in the proportions of 2, 5, 10, 15, 20 and 30%. The objective was to study the behavior of mixtures in a diesel cycle engine coupled to a dynamometer of Eddy Current. In this study of burning biodiesel blends in diesel engine were analyzed and compared with pure diesel parameters: consumption, efficiency, performance, torque and power. The results showed that the mixtures had very similar properties and performance to pure diesel by mixing 20%. To the mixture with 30% there has been a significant drop in torque and power and slight increase in consumption. Thus, it was shown that soybean oil biodiesel, mixtures of 2% to 30%, is applicable as an alternative fuel aptly, for the diesel cycle engines, because it is a renewable and environmentally friendly fuel.

Development of an Automatic Elastic Torque Control System Based on a Two-Mass Electric Drive Coordinate Observer

Development of control system based on digital twins of physical processes is a promising area of research in the rolling industry. Closed-loop control systems are developed to control the coordinates of two-mass electromechanical systems in order to limit the dynamic loads on the equipment of main rolling lines. These control systems are based on observers (digital shadows) that indirectly detect (reconstruct) the roll speed and the elastic torque of the shaft (spindle) in real time. Notably, observers are required to work fast in order to reconstruct transients attributable to shock (impact) loads. Literature review shows that the known observers, which use complex algorithms to compute coordinates, do not respond fast enough. The paper analyzes the kinematic diagram of Mill 5000, a plate rolling mill. It presents oscillograms that prove that the elastic torque does oscillate as the rolls grip the strip dynamically. The authors hereof have developed an observer that reconstructs the coordinates of the uncontrolled mass (the shaft) and the spindle torque from the parameters of the controlled mass, namely the torque and speed of the motor. The paper further rationalizes an approach that consists of simulating the processes on a model to further directly configure them on the object. The authors analyze the transients of the reconstructed two-mass system coordinates, which are associated with the rolls gripping the strip. The paper compares data against oscillograms recorded on the mill itself. The accuracy is satisfactory. The proposed observer has been used to developed a three-loop automatic speed control system for the uncontrolled mass. Controller configurations are substantiated. The paper shows coordinates obtained by simulation modeling as functions of time. It further presents experiments run on Mill 5000; the conclusions are that the amplitude and oscillations of the elastic torque drop significantly. The paper concludes with recommendations on industrial adoption of the observer and the novel electric drive coordinate control system. Study presented herein substantiates and implements a concept of developing algorithms that solve specific problems and are readily implementable on the existing equipment without need for additional computing devices. The contribution of the paper consists of stating and solving the problem of developing and testing an automatic elastic torque control system for the shaft of a heavy-duty rolling mill. This system has been implemented in the form of algorithms that run in the software of the existing industrial controllers (PLCs). It is simple and performs well. It does not need additional sensors or computers to be implemented, nor does it rely on complex computational algorithms. Such algorithms are based on computational tables that require a priori data on numerous process parameters. In our literature review, we have not come across any industrial implementation of such algorithms on hot-rolling mills.

Analysis of electromagnetic torque for induction motors with a novel non-skewed rotor structure

PurposePulsating torques cause a number of problems in electrical machines, including mechanical vibrations, acoustic noise and the depreciation of mechanical equipment. In induction motors, the slot skewing method is an effective way to solve these issues; however, it has some drawbacks such as output torque drop, stray loss intensification due to inter-bar currents and iron loss increment. Besides, slot skewing may not be practical in higher-rated induction motors. In this regard, this paper introduces a modified non-skewed rotor (MNSR) structure as a possible alternative to the skewed designs.Design/methodology/approachThe proposed structure includes a two-segmented rotor with an intermediate ring between the rotor parts that are mounted on the shaft with a relative shift angle. Detailed information about the idea and structure of the MNSR as well as its manufacturing aspects will be presented in the second section of the paper. First, the working principle of the proposed design is described via analytical equations to provide an insight into the concept. The shifting angle will then be calculated by analyzing the harmonic contents of the electromagnetic torque. Finally, the validity of the analytical method will be verified by developing three-dimensional finite element models.FindingsIt is demonstrated that by using the proposed rotor structure, the torque ripple has been reduced to a satisfactory level without significantly affecting the mean torque, unlike the skewing method. Furthermore, the new method could avoid the disadvantages of the skewing method while enhancing other motor characteristics such as iron loss. Also, the total volume of the MNSR is equal to the initial design, and the mass and material differences are also negligible.Originality/valueIn this paper, a MNSR is introduced as a possible alternative to the skewed patterns. The study mainly focused on electromagnetic torque profile characteristics, i.e. the mean torque enhancement and the ripple reduction. The MNSR structure can be used for general purposes and high-performance applications, especially where excellent torque characteristics are required.

Research on design and numerical optimization of bowed-twisted-swept cascade of low aspect ratio hydraulic turbine

The bowed-twisted-swept modeling technology of three-dimensional blade has been widely used in the gas impeller machinery and achieved good results. This paper introduces the two-dimensional flow theory and the bowed-twisted-swept modeling ideology into hydraulic turbine design. Simultaneously combined with the popular NSGA-II multi-objective optimization algorithm, a complete set of hydraulic turbine cascade design method was proposed. Taking the last-stage low aspect ratio hydraulic cascade of Ф175 type turbine as an example, the parametric model of this cascade was reconstructed by a high-precision automatic bridge coordinate measuring machine. The multi-objective optimization design of three-dimensional modeling of cascade was completed with the single-stage turbine output torque, efficiency and pressure drop as the objective targets. Finally the influence of the bowed-twisted-swept modeling technology on the hydraulic turbine performance was explored in detail by a professional rotating machinery CFD software. Numerical analysis shows that the twisted blade design achieves a 1.5 times increase in torque and 2 to 4 times increase in pressure diff at same working condition. Moreover, when bowing optimization design and sweeping optimization design are applied on the twisted blade individually, the output torque and the stage efficiency of the hydraulic turbine are respectively improved, and when both two methods are simultaneously applied on the twisted blade, it is beneficial to reduce the pressure drop loss. However, it is noticeable that when the bowed-swept modeling technology used in a straight blade using almost have no effect on the turbine performance.

Cyclic eccentric stretching induces more damage and improved subsequent protection than stretched isometric contractions in the lower limb.

Controversy remains about whether exercise-induced muscle damage (EIMD) and the subsequent repeated bout effect (RBE) are caused by the stretching of an activated muscle, or the production of high force at long, but constant, muscle lengths. The aim of this study was to determine the influence of muscle fascicle stretch elicited during different muscle contraction types on the magnitude of EIMD and the RBE. Fourteen participants performed an initial bout of lower limb exercise of the triceps surae. One leg performed sustained static contractions at a constant long muscle length (ISO), whereas the contralateral leg performed a bout of eccentric heel drop exercise (ECC). Time under tension was matched between the ECC and ISO conditions. Seven days later, both legs performed ECC. Plantar flexor twitch torque, medial gastrocnemius (MG) fascicle length and muscle soreness were assessed before, 2h and 2days after each exercise bout. MG fascicle length and triceps surae surface electromyography were examined across the bouts of exercise. We found that both ECC and ISO conditions elicited EIMD and a RBE. ISO caused less damage 2h after the initial bout (14% less drop in twitch torque, P = 0.03) and less protection from soreness 2days after the repeated bout (56% higher soreness, P = 0.01). No differences were found when comparing neuromechanical properties across exercise bouts. For MG, the action of stretching an active muscle seems to be more important for causing damage than a sustained contraction at a long length.

Observation of off-axis sawtooth oscillations during the presence of nonlinear mode couplings in HL-2A NBI heated plasmas

Off-axis sawtooth oscillations during the presence of nonlinear coupling between toroidal Alfvén eigenmodes (TAEs) and tearing mode are firstly observed in the plasma without two q = 2 rational surfaces on HL-2A tokamak. Those low frequency oscillations always take place followed by nonlinear interaction processes and the off-axis features have been confirmed by multiple diagnostics, such as soft x-ray arrays and electron cyclotron emission imaging systems. A possible physical mechanism is proposed for interpretation of those off-axis oscillations. That is, nonlinear interaction between TAEs and tearing mode causes significant losses of fast ions though the spacial overlapped global mode structure, then makes a drop in torque and leads to rotation braking or even mode locking. When magnetic fluctuation becomes large enough during braking or locking, the resulting high amplitude saturated mode leads to subsequent or immediate collapse at the q = 2 rational surface.

A Study on the Shape of the Rotor to Improve the Performance of the Spoke-Type Permanent Magnet Synchronous Motor

This paper describes a study on the improvement of the dehydration performance of the conventional washing machine model. Recently, as interest in improving the dehydration performance of washing machines has increased, the need for a study on a high-speed electric motor has emerged. However, this conventional spoke-type PMSM has difficulty in speeding up due to the following problems. First, field weakening control is indispensable for high-speed operation of an electric motor. This control method is a big problem in causing torque drop and irreversible demagnetization of the motor. Moreover, the centrifugal force increases during high-speed operation, which adversely affects the stiffness of the motor. Therefore, in this paper, a new rotor shape of spoke-type PMSM was proposed to solve the above problem.

Practical Aspects of Cylinder Deactivation and Reactivation

Cylinder deactivation is an effective measure to reduce the fuel consumption of internal combustion engines. This paper deals with several practical aspects of switching from conventional operation to operation with deactivated cylinders, i.e., gas spring operation with closed intake and exhaust valves. The focus of this paper lies on one particular quantity-controlled stoichiometrically-operated engine where the load is controlled using the valve timing. Nevertheless, the main results are transferable to other engines and engine types, including quality-controlled engines. The first aspect of this paper is an analysis of the transition from fired to gas spring operation, and vice versa, as well as the gas spring operation itself. This is essential for mode changes, such as cylinder deactivation or skip-firing operation. Simulation results show that optimizing the valve timing in the last cycle before deactivating/first cycle after reactivating a cylinder, respectively, is advantageous. We further show that steady-state gas spring operation is reached after approximately 6 s regardless of the initial conditions and the engine speed. The second aspect of this paper experimentally verifies the advantage of optimized valve timings. Furthermore, we show measurements that demonstrate the occurrence of an unavoidable torque ripple, especially when the transition to and from the deactivated cylinder operation is performed too quickly. We also confirm with our experiments that a more gradual mode transition reduces the torque drop.

Optimization of Wells turbine performance using a hybrid artificial neural fuzzy inference system (ANFIS) - Genetic algorithm (GA)

Renewable energy resources are considered as alternative sources of energy for future generations. Wells turbines can be used to convert the reciprocating energy of waves in oceans and seas into rotational energy. Low aerodynamic efficiency is the main drawback of Wells turbines. The present study showed that the addition of the guide vanes, endplate, or end ring to the base blade significantly enhanced the performance of Wells turbines. Also, we used ANFIS-GA-CFD for optimization of the several design variables (the blade tip thickness, the blade form, and the input-output angels of guide vanes) simultaneously. Therefore, artificial neural fuzzy networks were used to forecast the three benchmark parameters (pressure drop coefficient, torque coefficient, and efficiency) and a genetic algorithm was utilized to approximate the optimized design variables when there are maximum torque, maximum efficiency, and minimum pressure drop. The optimal blade increased the upper limit of efficiency up to 18%, torque coefficient up to 8%, and reduced the pressure drop coefficient up to almost 3.45% compared to the best previous models. Moreover, flow separation was delayed.

Design of Three-Phase Induction Motor Starting Drive Based on Electromagnetic Torque Analysis

The process of starting a three-phase induction motor consumes a very largecurrent from the power grid, which can cause voltage drops and damage the coilinsulators due to the heat generated. However, this has been overcome by using severalstarting methods including star-delta starter, starter with autotransformer, soft starter,and drive frequency or better known as VFD or VSD. In conventional soft starters, asmall reduction in voltage results in a sizable drop in electromagnetic torque. This cancause a motor with a certain load to fail to start. In this research, a three-phase inductionmotor soft starter modeling will be carried out using the method of setting the sourcevoltage and frequency, designed to overcome the low electromagnetic torque generatedby conventional soft starters. The modeling of the soft starter with thyristor control isexpected to produce high and stable electromagnetic torque. So that the soft starter withthyristor control can be a solution for conventional soft starters.