Static Torque Research Articles

Wind tunnel experimental study on static aerodynamic performance of SB-VAWT without intermediate support axes

Wind power generation is considered an effective way for ships to harness wind energy, and the aerodynamic characteristics of wind turbines determine wind energy utilization and efficiency. However, traditional vertical axis wind turbines have intermediate shafts and support rods, which result in large negative effects in the research of the wind turbine aerodynamic characteristics. To address this issue, a Straight-Bladed Vertical Axis Wind Turbine (SB-VAWT) without intermediate support axes is proposed. The turbine can flexibly change the number of blades, rotor diameter, and installation position of blades. The static aerodynamic performance of the wind turbine with different combinations was tested in a wind tunnel laboratory at 10 m/s. The results show that the radius of the wind turbine has a greater effect on the drag coefficient for the same number of blades, with an inverse relationship between the drag coefficient and radius, and a positive association between lift coefficient, static torque coefficient, and radius. The drag coefficient is proportional to the number of blades at the same radius, while the static torque coefficient is inversely proportional to the number of blades. According to the results, placing the initial location in the azimuth range between 30° and 50° can obtain the maximum initial starting torque. Moreover, a wind turbine with a radius of 16 cm can achieve a higher average torque. Changes in the number of blades can significantly impact turbine properties, resulting in wind turbines with distinct features.

Comparison Study On Pinch-Hitting Vibration Signal Analysis for Automotive Bearing: I-KazTM and I-Kaz 3D

Rotating machines are now an essential part of the automotive industry. Meanwhile, a bearing is playing the most important component of rotating machinery. To sustain the system's smooth running, maintenance methods such as preventive maintenance, breakdown maintenance, and predictive maintenance are used. Under preventive maintenance, vibration analysis is used to diagnose machines bearing faults. The main objective is to recognize bearing defects in a mechanical device by acquiring signals from the bearing using data acquisition hardware. This analysis is conducted under various load torque conditions, speeds, and defect types. A modular hardware configuration consisting of an accelerometer acquires the vibration signal. The signals are analyzed by using I-kazTM and I-kaz 3D signal analysis and its main objective is to observe the degree of dispersion data from its mean point. This analysis resolves the issues associated with time domain analysis. This pinch-hitting analysis research was conducted in two stages. The first stage is an experimental process that uses 3 types of bearings, the healthy (BL), inner race fault (IRF), and defect at outer race (ORF) bearing on the Machine Fault Simulator and forces with a different type of speed (1000, 1500 and 2500 rpm) and load variation (0.0564, 0.564 and 1.1298 N-m). In the second stage, computing the coefficient value and plots of signal’s I-kazTM and I-kaz 3D based on the bearings type were done accordingly. As a result, the analysis for detecting inner race fault, the deviation percentage averages calculation obtained the I-kazTM coefficient shows a better result with 96.86% by comparing to the I-kaz 3D that achieves 94.20%. Similarly, for the outer race defect, I-kazTM lead with 65.40% compared to I-kaz 3D with only 54.82%.

Enhancing vertical axis wind turbine efficiency through leading edge tubercles: A multifaceted analysis

This research paper aims to investigate the impact of leading edge tubercles (LET) on the performance of hybrid vertical axis wind turbine (VAWT). The study involves both experimental and computational analysis of a novel hybrid VAWT configuration. The proposed VAWT design is characterized by a high power coefficient and self-starting capability. To provide a basis for comparison, an existing hybrid VAWT without tubercles and a conventional H-Rotor Darrieus design were also examined. The findings indicate that the proposed hybrid VAWT achieved the highest power coefficient (Cp) of 0.475 at a tip speed ratio (TSR) of 3. Furthermore, the proposed wind turbine demonstrated superior Cp values at both low TSRs (1 to 2.1) and high TSRs (4.1 to 5) compared to the existing hybrid VAWT and the H-Rotor Darrieus turbine. The positive static torque coefficient (Cts) values observed at all azimuths, with a maximum value of 0.319, highlight the self-starting capability of the proposed hybrid wind turbine. The enhanced power coefficient and the ability to harness wind energy even at low wind speeds make the proposed hybrid wind turbine suitable for a wide range of power projects, from small to large-scale. This approach offers a means to determine the optimal design configuration for a hybrid VAWT and facilitates a detailed analysis during the early design stages, along with its high-fidelity characteristics.

Transient Electromyographic Responses by Isokinetic Torque Release during Mechanically Assisted Elbow Flexion.

Power assistance on joint torque may not be beneficial to all the related muscles. We investigated the effects of power assistance on torque release during isokinetic elbow flexion. An isokinetic dynamometer system was used to simulate dynamic elbow flexion with power assistance, which altered the exercise conditions of baseline isometric torque (greater and lower) and rotation speed (faster and slower) of the lever arm. Ten male right-handed participants performed exercise tasks using the system. We measured (1) the electromyogram (EMG) amplitudes of the biceps brachii (BB), brachioradialis (BR), and triceps brachii (TB) muscles, (2) torque output and its variability, and (3) the perceived assistance level. Transient responses of the objective measurements were analyzed by observing three time epochs before and after power assistance. Greater variability and lower perceived assistance levels were observed when greater torque was released at a faster rotation speed. The torque output and EMG amplitudes of BB and BR muscles decreased over time. However, EMG amplitudes in the TB muscle were relatively constant until 200 ms after power assistance resulting in greater muscle co-contraction. This could be attributed to the increased postural stability of the human musculature system when the external perturbation on joint movement occurred by power assistance, independent of exercise conditions.

An improved time-varying mesh stiffness calculation method and dynamic characteristic analysis for helical gears under variable torque conditions

Based on the slice theory and numerical calculation methods, the time varying meshing stiffness (TVMS) calculation method of the gear pair was constructed for the helical gear pair of a electric continuously variable transmission (ECVT), and the TVMS of the helical gear were calculated under different constant and time-varying torque in this study. The obtained stiffness values were introduced into the established dynamics model of helical gear system, and the influence of changed TVMS, resulting from the variable speed and torque, on the nonlinear dynamic characteristics of gear pair was analyzed using the Runge-Kutta method. The results show that the proposed TVMS calculation method is very effective in computing the TVMS of helical gear pair under time-varying condition. The TVMS and dynamic transmission error (DTE) increase as the torque increase, and vice versa. Meanwhile, the system exhibits a diverse range of periodic, sub-harmonic, and chaotic behaviors at high speed and at low speed when torque is low, whereas not appear at steady high torque under low speed range. This study offers a method for gaining the TVMS of helical gear pair to analyze the dynamic characteristics of gear pair under actual working condition, and the influence of torque that change with the speed ratio on the dynamic performance of a gear system should be considered in the industrial applications.

Novel revolving heat pipe cooling structure of permanent magnet synchronous motor for electric vehicle

The high temperature rises and uneven axial temperature distribution of permanent magnet synchronous motors applied in electric vehicles can lead to demagnetization of permanent magnets and turn-to-turn short circuit failures in the windings. Thus, a cooling structure based on revolving and fixed annular heat pipes is proposed. That is the revolving heat pipes are installed in the rotor, which are further increasing the rotor's heat transfer efficiency under the centrifugal force of rotor rotation. The fixed annular heat pipes are installed in the stator to cool the windings, especially the end of the windings. The experiments are designed to derive the equivalent thermal conductivity of the proposed revolving and fixed annular heat pipes on this basis. The effectiveness of the proposed cooling structure is verified by computational fluid dynamics simulations which are conducted in three typical operating conditions of the motor used in electric vehicles. The results show that the temperature rise of the rotor, permanent magnet and winding are decreased by up to 70.39%, 69.4%, and 46.18% respectively by the proposed cooling structure. It indicated that the axial temperature rises distribution of heat generating parts can be effectively equalized, and the operating time under maximum torque condition can be effectively extended, that from 30 s to 100 s.

The effect of contaminating media on the static and dynamic mechanical resilience of dental implant abutments' screws: In vitro study.

This in vitro study aims to biomechanically evaluate the influence of medium contamination for example, saliva, blood, chlorhexidine (liquid and gel), and fluoride mouthwash on the biomechanical behavior of implant abutments' screws under static and dynamic loading. Forty five Ti6Al4V commercial dental implants and abutments were tested in this study. Two main mechanical tests were carried out in the selected media. The first, static, aimed to evaluate the torque loss after the first tightening. The second, dynamic, involved a random cyclic load range between 0 and 200 N to evaluate torque loss due to mastication. In addition, metallographic longitudinal and cross-sections of the abutment-implant apparatus were examined to evaluate the abutment screw-abutment-implant interface. The static torque test showed that irrespective of the media, no statistical difference in static torque loss was found prior to dynamic loading. For the dynamic tests, torque-angle evolution analysis during tightening to 30 Ncm and after the spectrum loading, showed the same global mechanical behavior for all media, but the statistical analysis indicated a difference between the groups in reverse torque values (RTV) and in the torque loss due to dynamic loading. The medium groups CHX, CHX-gel, and Fluoride mouthwash, showed a meaningful torque loss due to loading, but the medium groups, control (no medium), blood and saliva showed an opposite trend and required a higher torque to open the abutment screws. The microstructural analysis revealed clear signs of cold-welding/galling, post-dynamic loading in these latter groups. The presence of lubrication/contamination media (CHX mouthwash/CHX-gel/Fluoride mouthwash) reduces the preload generated due to tightening but prevents damage due to galling. The observed reduction of RTV clearly emphasizes the need for frequent abutment screw retightening for implant-supported prosthetic long-term stability.

Novel performance enhancement of straight blade vertical axis wind turbines through cross-flow fan integration

In this study, a novel technique for enhancing the output power of Vertical Axis Wind Turbines (VAWTs) is introduced through the integration of a cross-flow fan (CFF) for active flow control, a first-of-its-kind approach. The CFF, positioned on the airfoil's trailing edge, employs suction to regulate flow separation. A thick airfoil with a 35% thickness-to-chord ratio is utilized to accommodate the CFF. A VAWT, featuring a diameter of 1 m and a height of 0.5 m, is designed, fabricated, and subjected to experimental testing in a wind tunnel. Additionally, a standard NACA 0018 wind turbine with identical dimensions and solidity is manufactured for performance comparison purposes. A custom test rig is developed to measure turbine output, encompassing a fixation mechanism, torque measurement system, and a mechanical brake mechanism for load variation. The impact of the CFF on the wind turbine performance is investigated by measuring turbine static torque due to the fan, fan motor power consumption, turbine torque, and rotational speed across various wind speeds. Power assessments are conducted to estimate the real turbine power increase, taking into account the power consumed by the fans. A fan map is generated to determine the optimal conditions and rotational speeds for fan operation.

A Multi-Mode High-Efficiency Fault-Tolerant Permanent Magnet Machine

This article proposes a new multi-mode high-efficiency fault-tolerant permanent magnet machine with an inner stator to place AC field windings. The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis current in the field windings enables the proposed machine to be driven individually or together with the armature windings. On the other hand, the flux can be regulated by applying the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis current to the field windings. As a result, multiple operation modes are realized. The proposed machine can run in different modes at different torque and speed operating conditions, implementing the multi-zone high-efficiency operation. Meanwhile, a new fault-tolerant control method can be applied in the proposed machine by combining the mode switching and compensation current in the healthy windings, thus improving the efficiency under fault-tolerant operation. Moreover, the multi-zone high-efficiency regions of the proposed and conventional machines are investigated. The proposed and traditional fault-tolerant methods for the proposed machine are compared. The results reveal that the proposed machine offers a larger high-efficiency region and is capable of stronger fault tolerance. Furthermore, since the double stators in the proposed machine need to operate individually, a swallow-shaped rotor with auxiliary salient poles is adopted to reduce outer torque ripple and inner torque ripple. Finally, the experiments are performed to verify the predicted performances.

Multiparameter Estimation-Based Sensorless Adaptive Direct Voltage MTPA Control for IPMSM Using Fuzzy Logic MRAS

This paper introduces a parameter-estimation-based sensorless adaptive direct voltage maximum torque per ampere (MTPA) control strategy for interior permanent magnet synchronous machines (IPMSMs). In direct voltage control, the motor’s electrical parameters, speed, and rotor position are of great significance. Thus, any mismatch in these parameters or failure to acquire accurate speed or position information leads to a significant deviation in the MTPA trajectory, causing high current consumption and hence affecting the performance of the entire control system. In view of this problem, a fuzzy logic control-based cascaded model reference adaptive system (FLC-MRAS) is introduced to mitigate the effect of parameter variation on the tracking of the MTPA trajectory and to provide precise information about the rotor speed and position. The cascaded scheme consists of two parallel FLC-MRAS for speed and multiparameter estimation. The first MRAS is utilized to estimate motor speed and rotor position to achieve robust sensorless control. However, the speed estimator is highly dependent on time-varying motor parameters. Therefore, the second MRAS is designed to identify the quadratic inductance and permanent magnet flux and continuously update both the speed estimator and control scheme with the identified values to ensure accurate speed estimation and real-time MTPA trajectory tracking. Unlike conventional MRAS, which uses linear proportional-integral controllers (PI-MRAS), an FLC is adopted to replace the PI controllers, ensuring high estimation accuracy and enhancing the robustness of the control system against sudden changes in working conditions. The effectiveness of the proposed scheme is evaluated under different speed and torque conditions. Furthermore, a comparison against the conventional PI-MRAS is extensively investigated to highlight the superiority of the proposed scheme. The evaluation results and our quantitative assessment show the ability of the designed strategy to achieve high estimation accuracy, less oscillation, and a faster convergence rate under different working conditions. The quantitative assessment reveals that the FLC-MRAS can improve the estimation accuracy of speed, permanent magnet flux, and quadratic inductance by 19%, 55.8% and 44.55%, respectively.

Arithmetic optimization algorithm based torque ripple minimization technique for solar fed sensorless BLDC drive for domestic applications

The high efficiency feature of the Brushless Direct Current (BLDC) motor can be used for industrial drive applications to minimize the power consumption. The BLDC motor suffers with torque ripple issues during medium and high-speed applications which minimizes the use of BLDC in various applications. This paper proposes an Arithmetic Optimization Algorithm (AOA) tuning to enhance the gain of the controller to mitigate the torque ripple of the BLDC drive. This improves the application of BLDC in domestic and industrial applications viz., compressor, air conditioner. The proposed algorithm is tested in a solar fed compressor using MATLAB simulation and the results shows that the AOA advances the behavior of BLDC motor at different speed, torque conditions with minimum power consumption and low vibrations.

Processing and Friction Properties Evaluation of Multilayer CU Matrix Hybrid Composite Brake Pads for a Trainer Aircraft

We have developed three types of multi layer Cu matrix composite brake pads, namely, Copper-silica-BN, Copper-Si3N4-graphite, and Copper-mullite-MoS2 to solve the problem of static torque, friction coefficient in the upgraded version of Trainer aircraft. These composite brake pads were tested in a full scale brake dynamometer and static torque testing unit at ARDC, HAL. Our results shows that the braking requirements of static torque (~ 204 Kgfm), friction coefficient (~0.3-0.45) were very well met in the multilayer Copper-mullite-MoS2 composite brake pads. The role of MoS2 and Mullite in improving static torque, friction coefficient and stabilizing frictional properties in this composite brake pads were explained in detail.

Wind tunnel test and numerical analysis of wooden-bladed Darrieus wind rotor at low wind speed conditions

The present study aims to conduct wind tunnel tests and numerical analyses to comprehensively assess the performance of wooden-bladed Darrieus wind rotors, specifically focusing on their behavior at low wind speeds. Limited investigation exists on the aerodynamic behavior of wooden-bladed Darrieus wind rotors under low wind speed conditions, necessitating comprehensive analysis to understand their performance characteristics and address this research gap. The present study is undertaken to address this gap. In addition, the paper also presents airfoil and blade material selection and fabrication of the rotor. The study is conducted on the NACA 0018 airfoil profile of the blades at low wind speeds of 4 and 6 m/s, commonly encountered in urban areas. The wind tunnel tests measure various rotor performance parameters such as the Static torque coefficient (Cts) and Power coefficient (Cp). At the same time, numerical simulations are used to study the flow behavior around the rotor blades. The Cts of the rotor is calculated at 12 different azimuthal positions between 0° to 360°. The Cp of the rotor is calculated at different tip speed ratios (λ). The present rotor exhibited maximum Cts of 0.64 and 0.66 and maximum Cp of 0.132 (at λ = 1.26) and 0.141 (at λ = 1.29) for 4 m/s and 6 m/s, respectively. Finally, it can conclude that the constructed wooden Darrieus rotor is working positively at low wind speeds, and the results may be used to develop wooden wind turbines for small-scale power generation.

Performance, Emissions, and Combustion Characteristics of a Hydrogen-Fueled Spark-Ignited Engine at Different Compression Ratios: Experimental and Numerical Investigation

This paper investigates the performance of hydrogen-fueled, spark-ignited, single-cylinder Cooperative Fuel Research using experimental and numerical approaches. This study examines the effect of the air–fuel ratio on engine performance, emissions, and knock behaviour across different compression ratios. The results indicate that λ significantly affects both engine performance and emissions, with a λ value of 2 yielding the highest efficiency and lowest emissions for all the tested compression ratios. Combustion analysis reveals normal combustion at λ ≥ 2, while knocking combustion occurs at λ &lt; 2, irrespective of the tested compression ratios. The Livenwood–Wu integral approach was evaluated to assess the likelihood of end-gas autoignition based on fuel reactivity, demonstrating that both normal and knocking combustion possibilities are consistent with experimental investigations. Combustion analysis at the ignition timing for maximum brake torque conditions demonstrates knock-free stable combustion up to λ = 3, with increased end-gas autoignition at lower λ values. To achieve knock-free combustion at those low λs, the spark timings are significantly retarded to after top dead center crank angle position. Engine-out NOx emissions consistently increase in trend with a decrease in the air–fuel ratio of up to λ = 3, after which a distinct variation in NOx is observed with an increase in the compression ratio.

Multi-Objective Optimization of the Structural Design of a Combustion Chamber of a Small Agricultural Diesel Engine Fueled with B20 Blend Fuel at a High Altitude Area

This study focuses on a small agricultural diesel engine fueled with B20 (20% biodiesel and 80% diesel by volume) blend fuel in a plateau area. The combustion chamber’s structural parameters and fuel injection angle were taken as variables at peak torque conditions. First, a full factorial design was used for experimental design. Second, the back-propagation (BP) neural network was employed to predict the indicated thermal efficiency and the indicated specific NOx emission. Third, the non-dominated sorting genetic algorithm-II (NSGA-II) was utilized to optimize the indicated thermal efficiency and the indicated specific NOx emission. Finally, the technique for order of preference by similarity to ideal solution (TOPSIS) method was applied to obtain optimal solutions, and a three-dimensional numerical simulation was conducted to verify the optimization results. The optimization results indicate that the shape characteristics of the combustion chamber have a certain influence on the engine’s performance. The optimized design significantly reduces NOx emissions, by 22.83%, compared to the original engine, whilst maintaining the engine’s performance.

Equations for estimating the static supportive torque provided by upper-limb exoskeletons

Upper-limb exoskeletons are gaining traction in industrial work environments. However, other than advertised general specifications (e.g., peak support angle), the support torque provided throughout the reach envelope is largely unknown to end users. As such, this paper describes a methodology for measuring the specific supportive torque provided by upper-limb exoskeletons. The support of four commercially available passive upper-limb exoskeletons was quantified using an isokinetic dynamometer for all support ranges and levels (n = 68). Tests were repeated four times to determine between-session reliability. Intraclass correlation coefficients demonstrated ‘Good’ to ‘Excellent’ reliability, except for one condition. Polynomial regression equations were developed for each condition to predict exoskeleton support for any upper-limb elevation angle between 10° and 180°. These equations can be used to approximate upper-limb exoskeleton support in digital human modeling assessments, or to aid selection of exoskeleton settings specific to a worker's anthropometry and work task location.

Static Characteristics of Friction Block Teeth of Coiled Tubing Drilling Robot

Conventional downhole traction robots only provide axial traction, while coiled tubing drilling (CTD) robots must not only overcome the axial force but also overcome the reaction torque generated by the drill bit breaking the rock. Therefore, the tooth profile of the friction block of the conventional downhole traction robot cannot achieve effective support under the simultaneous action of the axial load and circumferential load. In this paper, based on the actual reaction torque conditions generated by CTD, a mechanical model of the friction block teeth of the CTD robot under the conditions of axial traction and reverse torque is established. This reveals the influence of different tooth slope angles, axial-included angles and friction coefficients on the mechanical properties. It provides guidelines for the design of the inclination of the tooth slope, the axial angle of the tooth and the friction coefficient of the friction block of the CTD robot. It has scientific and engineering significance for the promotion of downhole robots in drilling engineering.

Power performance and self-starting features of H-rotor and helical vertical axis wind turbines with different airfoils in turbulence

Wind tunnel tests were conducted to systematically assess the aerodynamic performance of both H-rotor and helical vertical axis wind turbines (VAWTs) in smooth and turbulent flows. The effects of airfoil section and pitch angle β on the power and self-starting performance were examined for both types of turbines. The helical turbine had a wider operating range of tip speed ratios (TSR λ) and much lower power performance than its H-rotor counterpart. This phenomenon was attributed to the flow deflection of helical blades due to their three-dimensional features, as well as that dynamic stall of a helical blade would not occur simultaneously for all blade elements. The helical turbine did not exhibit notably improved self-starting performance despite of the high manufacturing cost. Moreover, the start-up process was analyzed by using the static torque coefficient CT of both single-bladed and three-bladed turbines. It was found that turbulence intensity exercised a significant impact on CT. Turbulence would cause serious fatigue issues for H-rotor turbines and change the driving mechanism of helical turbines though it enhanced the self-starting performance. Recommendations were finally provided for the design of VAWTs in built environments.

Experimental investigation of solidity and blade profile effects on H-Darrieus wind rotor: Performance and self-starting analysis

The present study investigates the impact of rotor solidity and blade profile on the self-starting characteristics and performance of H-Darrieus wind rotors (H-rotors) through subsonic wind tunnel experiments. Three symmetrical (NACA 0018) and three unsymmetrical (NREL S823) H-rotors were analyzed to determine the coefficient of static torque (Cts) and coefficient of power (Cp) across three solidities (σ = 0.25, 0.3, and 0.35) and two free stream wind speeds (Uf = 6 and 8 m/s). The findings revealed that the NREL S823-bladed H-rotor outperformed the NACA 0018-bladed H-rotor, displaying 13% and 11% higher Cts values at σ = 0.25 (Uf = 6 and 8 m/s), 9% and 9% at σ = 0.3 (Uf = 6 and 8 m/s), and 13% and 11% at σ = 0.35 (Uf = 6 and 8 m/s). The NREL S823-bladed H-rotor achieved a maximum Cp of 0.197 at σ = 0.3 and Uf = 8 m/s, which is 6% higher than the maximum Cp obtained by the NACA 0018-bladed H-rotor. Furthermore, the trend of maximum Cp values for both H-rotors followed the order of Cp, max σ = 0.25 &amp;lt; Cp, max σ = 0.3 &amp;gt; Cp, max σ = 0.35. Based on the experimental findings, it is inferred that the NREL S823-bladed H-rotor with a solidity of 0.3 is suitable for small-scale wind turbines.

Improved startup control of aero doubly salient electromagnetic starter generator based on optimised currents distribution with advanced angle commutation

AbstractDoubly salient electromagnetic machine (DSEM) can constitute a competitive rugged starter generator (SG) system. But under the traditional startup control method, the field current is set to the rated value regardless of speed or load torque conditions, and the phase currents are controlled with standard angle commutation, bringing in large power loss as well as non‐negligible torque ripple. To overcome these shortcomings, based on the established DSEM power loss calculation model, a currents distribution strategy is proposed according to the obtained quantitative relationship between DSEM power loss and field current under multiple speed and load torque conditions. Then, to identify the load torque for practical implementation, a novel torque observer is designed based on back propagation (BP) neural network algorithm. Afterwards, to further improve the startup torque performance, currents distribution with advanced angle commutation (AAC) strategy is put forward, where the optimal advanced angle is selected from a 3‐D lookup table to achieve the minimal commutation torque ripple. Under the proposed control strategies, DSEM power loss as well as the output torque ripple are desired to be decreased, the simulation and experimental results on a 12/8‐pole DSEM prototype verify the correctness and feasibility of the proposed strategies under multiple operating conditions.