Average Rotational Speed Research Articles

Experimental study on single-cylinder two-stroke piston expander based on in-cylinder spray heat transfer

Compressed air energy storage stands as a highly promising technology within the realm of energy retention. The piston expander finds applicability in smaller-scale compressed air energy storage systems. In compressed air energy storage systems, the expansion process is critical in energy discharge and significantly impacts overall performance. Isothermal expansion techniques are effective in enhancing the operational efficiency of piston expanders, in contrast to adiabatic expansion methodologies. Previous simulations by our research group show that the isothermal expansion model has a lower power output than the adiabatic expansion model due to its higher exhaust pressure. To further validate the accuracy of the simulation results, an experimental platform was constructed and the uncertainty of the experimental system as well as the measured data was evaluated. This study conducted experimental research using the single-variable method, focusing on different load conditions and spray parameters. The study findings indicate that the exhaust pressure during isothermal expansion consistently exceeds that of adiabatic expansion. The exhaust pressure of isothermal expansion increased by 3.85 % to 14.9 %. Under varying load conditions, the average rotational speed and output power of isothermal expansion were noted to be inferior to those of adiabatic expansion. Despite changes in nozzle diameter or spray temperature when the spray timing is set at 0°-180°, the average rotational speed and output power of isothermal expansion remain lower than that of adiabatic expansion. The average output power of isothermal expansion decreased by 1.29 % to 5.24 %. Nevertheless, if the spray timing is set between 0°-120°, the average output power of the isothermal expansion surpasses the adiabatic expansion with an improvement of 1.84 %.

Design and Experiment of In-Situ Bionic Harvesting Device for Edible Sunflower

In view of the low degree of mechanization and poor quality of harvesting of edible sunflower after drying, an in situ bionic harvesting device was designed, which can achieve low-loss harvesting of edible sunflower without removing the edible sunflower disc. According to the physical characteristics of sunflower stalks in the field, influencing factors of in situ low-loss feeding were obtained, and the structural parameters of the in situ feeding mechanism were determined. Based on bionic technology and static analysis, the influencing factors on the performance of the bionic threshing mechanism were obtained. By analyzing the mechanical characteristics of edible sunflower seed, the operation parameters of the seed collection mechanism were determined. Based on the structural analysis results of the harvesting device, a response surface optimization test was carried out. The test results show that when the average rotation speed of the bionic loosening roller was 113.57 rpm, the average rotation speed of the simulated artificial striking roller was 230.80 rpm, the average forward speed of the harvesting device was 0.58 m/s, the working quality of the harvesting device was the best, the seed loss rate was 2.12%, and the edible sunflower disc threshing rate was 98.96%. A field verification test further confirms that under the optimal working parameters, the relative deviation between test indexes and response surface optimization test results was less than 2%. During the operation process, the movement of key components of the harvesting device was coordinated and stable. The research results can provide new ideas for the mechanized harvesting of the edible sunflower disc after drying.

A New Order Tracking Method for Fault Diagnosis of Gearbox under Non-Stationary Working Conditions Based on In Situ Gravity Acceleration Decomposition

Rotational speed measuring is important in order tracking under non-stational working conditions. However, sometimes, encoders or coded discs are not easy to mount due to the limited measurement environment. In this paper, a new in situ gravity acceleration decomposition method (GAD) is proposed for rotational speed estimation, and it is applied in the order tracking scene for fault diagnosis of a gearbox under non-stationary working conditions. In the proposed method, a MEMS accelerometer is locally embedded on the rotating shaft or disc in the tangential direction. The time-varying gravity acceleration component is sensed by the in situ accelerometer during the rotation of the shaft or disc. The GAD method is established to exploit the gravity acceleration component based on the linear-phase finite impulse response (FIR) filter and complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) methods. Then, the phase signal of time-varying gravity acceleration is derived for rotational speed estimations. A motor–shaft–disc experimental setup is established to verify the correctness and effectiveness of the proposed method in comparison to a mounted encoder. The results show that both the estimated average and instantaneous rotational speed agree well with the mounted encoder. Furthermore, both the proposed GAD method and the traditional vibration-based tacholess speed estimation methods are applied in the context of order tracking for fault diagnosis of a gearbox. The results demonstrate the superiority of the proposed method in the detection of tooth spalling faults under non-stationary working conditions.

Single-pixel imaging for a high-speed rotating object with varying rotation speed

We report a single-pixel imaging method that can capture high-quality images of a high-speed rotating object with varying rotation speed. Recently, single-pixel imaging methods for high-speed rotating objects were proposed, but the methods commonly require the object should rotate at a constant speed, which limits their practical use. Here we report an improved method that adopts synchronized rotation angle detection to ease the requirement of constant rotation speed of the target object. With the synchronized rotation angle detection, the single-pixel measurements at the same rotation angle can be extracted in the data post-processing, so that the target object and the structured patterns remain relatively motionless. We successfully demonstrate the reported method in imaging a central-process-unit cooling fan whose average rotation speed is 14,402 revolutions per minute (rpm) with a varying speed from 14,357.50 to 14,436.96 rpm. The method provides continuous and high-resolution imaging of a high-speed rotating object with a practical and robust solution. It might find various potential applications such as health monitoring of high-speed rotating machines in operation.

Analysis of Rotational Speed Variation of Umbi Teki Skin Peeling Machine in Chips Making Process

The Umbi teki skin peeling machine is a machine used to assist in the process of making chips. Umbi teki, which will be processed into chips, will go through several processing processes, such as soaking the material with clean water first and then peeling the fiber and skin until it is clean, then roasting until the texture of the seeds starts to soften and then pounded using a hammer, after which it is dried in the sun until it is scorched. One of these production processes is carried out using this peeling machine to peel the skin of the Umbi teki. Factors affecting peeling include engine rotation speed (rpm), while some researchers state that the best average rotation speed on a peeling machine is 250-500 rpm. This study aims to determine the effect of engine rotation speed on stripping results and find the best rotation speed on an Umbi teki peeling machine with a load of 121 grams/minute. The method used in this research is an experimental study conducted with ten rotation speed variations. Data were analyzed using ANOVA to determine the best variation treatment. Results show that using engine rotation speed variables affects the average difference in skin stripping. The best engine rotation speed of 626 rpm produces the best percentage of stripping results, with a value for TB (Well Peeled) and TS (Not Perfectly Peeled) being 87.3% and 9.3%, respectively.

Analysis of the Effect of Temperature on Testing of Unidirectional Generator Rotation Speed and Wind Speed in Wind Power Plants

Renewable power plants and alternative power are the best options to meet the world's electricity needs considering the expensive and scarce of petroleum power which has remained the main option in the power generation system. Electric power is something of the main need used by humans. Nationally, the demand for electricity continues to increase to coincide with the rate of population growth, but the rate of demand for very fast power is not matched by the real creation of power zones. Currently, national energy is still focused on fossil energy, namely coal, petroleum, and natural gas. With the increasing use of energy, especially petroleum, until in the future the amount also continues to be limited, fossil energy reserves will decrease and will not be relied on to meet energy needs, because its non-renewable nature requires to quickly explore renewable energy sources. The results of the research tried at an average voltage of 5.12 Volts. As well as the average wind speed of = 4.88 m/s on the contrary, the average rotation speed of the generator is = 8.4 rpm

Experimental Study of The Fan Turbine Performance in Oscillating Water Column with Airflow System in Venturi Directional

The Indonesian Ocean Energy Association has ratified the potential for ocean wave energy in Indonesia with a theoretical potential of 141,472 Megawatts. Unfortunately, this vast potential has not yet been utilized optimally in the Indonesian seas. Ocean wave energy technology has developed rapidly in various countries worldwide. One of the most famous ocean wave power generation technologies is the Oscillating Water Column (OWC), which utilizes airflow from ocean waves oscillating movement. Inspired by OWC, an innovative ocean wave power generation technology model was designed using a simpler fan turbine because it is directly integrated with an electric dynamo and an internal flow system in a venturi tube which can increase airspeed based on the concept of continuity theory. The experiment's results succeeded in creating up and down movements of ocean waves with a high tide of 15 cm and a low tide of 12 cm. Ocean wave oscillations can produce gusts of air with a speed of 1.56 m/s. The final result is obtained by model performance with an average turbine rotation speed of 42.191 rpm, an average electric voltage of 0.809 volts, and a more optimal turbine efficiency of 67.9%.

A complex model of a drilling rig rotor with adjustable electric drive

A modified mathematical model of an asynchronous electric drive of the rotor – a drill string – a bit – a rock is considered and implemented, which develops and generalizes the results of previously performed studies. The model includes the following subsystems: a model of an asynchronous drive with vector control; a model of formation of the resistance moment at the bottom of the bit, taking into account the peculiarities of the interaction between the bit and the rock; a model of a multi-mass mechanical part that takes into account the deformation of the drill string; subsystem for the drilling rig energy-technological parameters formation. The integrated model makes it possible to calculate and evaluate the selected drilling modes, taking into account their electro-mechanical, energy and technological efficiency and the dynamics of drilling processes. The performed computer simulation of drilling modes confirmed the possibility of a stick-slip effect accompanied by high-frequency vibrations during bit stops, which may change the direction of rotation of the bit, its accelerated wear and unscrewing of the drilling tool. Long bit stops lead to a significant decrease in the average bit rotation speed, which can explain the decrease in the ROP and increase in energy consumption when drilling in the zone of unstable bit rotation. The model can be used as a base for further improvement of rotary drilling control systems.

Condition Assessment and Analysis of Bearing of Doubly Fed Wind Turbines Using Machine Learning Technique

Condition monitoring of wind turbines is progressively increasing to maintain the continuity of clean energy supply to power grids. This issue is of great importance since it prevents wind turbines from failing and overheating, as most wind turbines with doubly fed induction generators (DFIG) are overheated due to faults in generator bearings. Bearing fault detection has become a main topic targeting the optimum operation, unscheduled downtime, and maintenance cost of turbine generators. Wind turbines are equipped with condition monitoring devices. However, effective and reliable fault detection still faces significant difficulties. As the majority of health monitoring techniques are primarily focused on a single operating condition, they are unable to effectively determine the health condition of turbines, which results in unwanted downtimes. New and reliable strategies for data analysis were incorporated into this research, given the large amount and variety of data. The development of a new model of the temperature of the DFIG bearing versus wind speed to identify false alarms is the key innovation of this work. This research aims to analyze the parameters for condition monitoring of DFIG bearings using SCADA data for k-means clustering training. The variables of k are obtained by the elbow method that revealed three classes of k (k = 0, 1, and 2). Box plot visualization is used to quantify data points. The average rotation speed and average temperature measurement of the DFIG bearings are found to be primary indicators to characterize normal or irregular operating conditions. In order to evaluate the performance of the clustering model, an analysis of the assessment indices is also executed. The ultimate goal of the study is to be able to use SCADA-recorded data to provide advance warning of failures or performance issues.

Effect of blade chord length on startup performance of H-type tidal current turbine rotor

This study aims to reveal the effect of the blade chord length on the startup performance of the lift rotor that converts the kinetic energy of tidal currents. The computational fluid dynamics technique was used to simulate unsteady flows around the rotor. The six degrees of freedom method was adopted to model the correlation between the rotational speed of the rotor and influential torques acting on the rotor. A comparative analysis of transient flows, rotational speed, and output torque was implemented at different initial azimuthal angles. The results show that as the rotor starts up at the minimum torque, the time required to attain the maximum rotational speed is longer than that associated with the maximum torque. As the maximum rotational speed is reached, low-pressure elements are produced in the area enclosed by the rotor blades, which is insensitive to the initial setting angle. A large area of low pressure is responsible for low output torque. During the startup process, the rotational speed experiences stages of sharp increase, fluctuating decrease, and moderate fluctuation, as is common at different blade chord lengths. As the chord length increases from 0.16 to 0.24 m, the startup process is extended by 0.63 s, and the average rotational speed in the stabilization stage decreases.

Wind-Tunnel Experiments on the Interactions among a Pair/Trio of Closely Spaced Vertical-Axis Wind Turbines

To elucidate the wind-direction dependence of the rotor performance in closely spaced vertical-axis wind turbines, wind-tunnel experiments were performed at a uniform wind velocity. In the experiments, a pair/trio of three-dimensional printed model turbines with a diameter of D = 50 mm was used. The experiments were performed systematically by applying incremental adjustments to the rotor gap g and rotational direction of each rotor and by changing the wind direction. For tandem layouts, the rotational speed of the downwind rotor is 75–80% that of an isolated rotor, even at g/D = 10. For the average rotational speed of the rotor pair, an origin-symmetrical and a line-symmetrical distribution are observed in the co-rotating and inverse-rotating configurations, respectively, thereby demonstrating the wind-direction dependence for the rotor pair. The inverse-rotating trio configuration yields a higher average rotational speed than the co-rotating trio configuration for any rotor spacing under the ideal bidirectional wind conditions. The maximum average rotational speed should be obtained for a wind direction of θ = 0° in the inverse-rotating trio configuration. The wind-direction dependence of the rotational speeds of the three turbines was explained via flow visualization using a smoke-wire method and velocity field study using two-dimensional computational fluid dynamics.

Instantaneous amplitude and phase signal modeling for harmonic removal in wind turbines

We present a novel approach to harmonic disturbance removal in single-channel wind turbine acceleration data by means of time-variant signal modeling. Harmonics are conceived as a set of quasi-stationary sinusoids whose instantaneous amplitude and phase vary slowly and continuously in a short-time analysis frame. These non-stationarities in the harmonics are modeled by low-degree time polynomials whose coefficients capture the instantaneous dynamics of the corresponding waveforms. The model is linear-in-parameters and is straightforwardly estimated by the linear least-squares algorithm. Estimates from contiguous analysis frames are further combined in the overlap-add fashion in order to yield overall harmonic disturbance waveform and its removal from the data. The algorithm performance analysis, in terms of input parameter sensitivity and comparison against three state-of-the-art methods, has been carried out with synthetic signals. Further model validation has been accomplished through real-world signals and stabilization diagrams, which are a standard tool for determining modal parameters in many time-domain modal identification algorithms. The results show that the proposed method exhibits a robust performance particularly when only the average rotational speed is known, as is often the case for stand-alone sensors which typically carry out data pre-processing for structural health monitoring. Moreover, for real-world analysis scenarios, we show that the proposed method delivers consistent vibration mode parameter estimates, which can straightforwardly be used for structural health monitoring.

A Distributed Method for Self-Calibration of Magnetoresistive Angular Position Sensor within a Servo System

Magnetoresistive angle position sensors are, beside Hall effect sensors, especially suitable for usage within servo systems due to their reliability, longevity, and resilience to unfavorable environmental conditions. The proposed distributed method for self-calibration of magnetoresistive angular position sensor uses the data collected during the highest allowed speed shaft movement for the identification of the measurement process model parameters. Data acquisition and initial data processing have been realized as a part of the control process of the servo system, whereas the identification of the model parameters is a service of an application server. The method of minimizing of the sum of algebraic distances of the sensor readings and the parametrized model is employed for the identification of parameters of linear compensation, whereas the average shaft rotation speed has been used as a high precision reference for the identification of parameters of harmonic compensation. The proposed method, in addition to a fast convergence, provides for the increase in measurement accuracy for an order of magnitude. Experimentally obtained measurement uncertainty was better than 0.5°, with the residual variance less than 0.02°, comparable to the sensor resolution.

Design of Portable Nano-hydro Generator for Lighting in Mountain Areas

Electricity needs in mountainous areas have not been optimal, so there need to be alternative power plants to meet the electricity supply in the mountainous area. For this reason, this study made an alternative power plant tool with the title Nano-hydro Generator Design Easy to Carry For Lighting In Mountainous Areas. The creation of this tool has several stages, including the first stage of making graphic design through SketchUp applications, then the second stage of the tool assembly in the form of mechanical design and civilian build, then the third stage of testing tools through water media, and the last stage of data retrieval to see if this tool works optimally. Based on the results of trials and data collection obtained, the average rotation speed of the turbine of 48.6 rpm, the rotation speed of the generator of 194.3 rpm, and a voltage of 6.3 volts.

Manufacturing process and experimental study of a small scale archimedes hydro powerplant by varying the number of blade

This study investigated the optimum value of Archimedes Screw Turbine (AST) performance by taking into account blades number. This paper also addressed the design approach based on a fixed incline angle of 30°, where this paper also addressed the design approach. Variations of the single and double blades were experimentally carried out concerning the turbine power output, torque, and rotation speed. This study's aim was related to the optimum power output between two blade variations, while the manufacturing and design steps were addressed as well. In the design process, the obtained blade length dimension was 0.180 m and 0.269 m for the single and double blades. Furthermore, the overall turbine's length was 1.7m, and the inner and outer of the turbine's radius were 0.069m and 0.128m. Meanwhile, the manufacturing process began with turbine modeling, plate cutting, plate withdrawal (thread formation), welding, and attained finishing process. Based on the experimental result, a double blade turbine generated turbine power by 48.8W at an average rotational speed of 115.3 rpm. Moreover, a single blade turbine produced 37.5W with turbine power averaging a rotational speed of 109.8 rpm. It was obtained that the values of turbine efficiency were 42% and 38% for double and single turbine types, respectively. Based on this finding, it can be suggested that a double blade was more efficient than a single one. This study is beneficial for the design consideration of the AST system.

ПРИМЕНЕНИЕ ТАХОГЕНЕРАТОРА И РЕГУЛИРУЕМОГО ЭЛЕКТРОПРИВОДА ДЛЯ ЗАМЕНЫ МЕХАНИЧЕСКОГО УПРАВЛЯЮЩЕГО КАНАЛА ДЛЯ СИНХРОННО-СЛЕДЯЩИХ СОРТИРОВОЧНЫХ УСТРОЙСТВ КРУГЛОГО ЛЕСА

Relevance Automated sorting of timber is one of the main types of work in modern timber warehouses, timber processing and woodworking enterprises. The choice of a sorting device is determined by the cargo turnover of the warehouse, the assortment composition, the sorting fraction and the conditions for the shipment of timber to consumers, as a rule, when sorting round timber, chain timber transporters (log haulers) are mainly used. The main elements of longitudinal sorting timber transporters are: drive, traction and tension devices, overpass with timber storage. With automated sorting, longitudinal conveyors are equipped with log ejectors and command devices (sorting devices) that provide automatic control of their work. Command devices are divided into two groups: local and synchronous-tracking sorting devices. The group of synchronously-tracking sorting devices contains an analog or discrete carrier, the information on which must move synchronously with the movement of the chain conveyor of the log haul. However, to fix the movement of the conveyor, one element of the kinematic scheme of the conveyor is available – this is the shaft of the driven or driving hexagonal wheel of the chain conveyor. For a group of synchronously tracking sorting devices, the synchronization of the sorting device with the movement of logs to storage bins and dumpers is of great importance. The average rotational speed of the driving and driven wheels of the chain conveyor and, consequently, the linear speed of movement of round wood on the chain conveyor is constant. Thus, the following positions can be attributed to the positive properties of synchronous- tracking sorting devices: automatic maintenance of all forest storages by one sorting device without additional elements that correct the process of turning on log throwers. The negative points include a significant inaccuracy in the control of log throwers, which predetermined the small introduction of a mechanical ball drum of orders. Therefore, further research into the technology of transporting logs on timber conveyors, taking into account the synchronization of the operation of the log sorting device, is an urgent scientific and technical task. Aim of research To identify new solutions and trends in their development in the field of development and research of ways to control the sorting device on sorting timber conveyors. Research methods Bibliographic analysis, statistical processing methods, simulation modeling. Results To control discrete and continuous synchronously-tracking sorting devices, a method for implementing a control channel based on a tachogenerator and an adjustable electric drive is proposed, the possibility of controlling the speed of the control channel and controlling continuous sorting devices without the use of additional means is considered and proved. In the study, a simulation method was used in MatLab 2021a, which makes it possible to verify the operability of the developed implementation of the control channel, and to evaluate the errors in the performance of the control channel. The simulation results confirmed the possibility of practical application of the proposed method for implementing the control channel. Based on the results obtained, it can be concluded that this method of implementing the control channel can be used to control discrete sorting devices. The study used the simulation method in MatLab 2021a, which allows you to verify the operability of the developed implementation of the control channel, and evaluate the errors in the performance of the control channel.

Analysis of Influence of Tilt Angle on Variable-Speed Fixed-Pitch Floating Offshore Wind Turbines for Optimizing Power Coefficient Using Experimental and CFD Models

This study focused on optimization of the power coefficient of floating offshore wind turbines (FOWTs) to maintain their wind power performance in order to overcome problems with the tilt angle resulting from an unstable wind turbine platform, which can reduce the effective area of wind turbine energy extraction. FOWTs with a variable-speed fixed-pitch control strategy were investigated using an experimental model in a wind tunnel and a CFD simulation model for analysis and comparison, using wind speeds of 2–5.5 m/s and tilt angles of 3.5–6.1°. The results showed that average rotational speed differences of 16.4% and optimal power coefficients of 0.35–0.36 could be maintained at tip speed ratios of 7.7–9.6 during wind speeds of 3–5 m/s with tilt angles of 3.9–5.8°. The results of this study provide insights into a new concept of power coefficient optimization using variable tilt angle for small to medium fixed pitch FOWTs, to reduce the cost of pitch control systems.

Bi-directional impulse chaos control in crystal growth.

Mono-silicon crystals, free of defects, are essential for the integrated circuit industry. Chaotic swing in the flexible shaft rotating-lifting (FSRL) system of the mono-silicon crystal puller causes harm to the quality of the crystal and must be suppressed in the crystal growth procedure. From the control system viewpoint, the constraints of the FSRL system can be summarized as not having measurable state variables for state feedback control, and only one parameter is available to be manipulated, namely, the rotation speed. From the application side, an additional constraint is that the control should affect the crystallization physical growth process as little as possible. These constraints make the chaos suppression in the FSRL system a challenging task. In this work, the analytical periodic solution of the swing in the FSRL system is derived using perturbation analysis. A bi-directional impulse control method is then proposed for suppressing chaos. This control method does not alter the average rotation speed. It is thus optimum regarding the crystallization process as compared with the single direction impulse control. The effectiveness and the robustness of the proposed chaos control method to parameter uncertainties are validated by the simulations.

Heat Transfer Coefficient Distribution on Oil Injection Cooled Gears: Experimental Method, Uncertainty, and Results

Abstract To design gearboxes with very high power densities, an effective means of cooling the gears and knowledge of the achievable heat transfer coefficients are necessary. In this paper, a method to measure heat transfer coefficients for oil injection cooled gears is presented. Contrary to other experimental investigations, a single hollow spur gear is used. To measure heat transfer coefficients, a temperature gradient between the gear and the hot oil needs to be induced. This is achieved by injecting hot oil at realistic temperatures and cooling the inside diameter of the gear. This enables the measurement of heat transfer coefficients in absence of any dissipative or frictional losses, decreasing the measurement uncertainty. In addition, the novel method yields spatially resolved HTC data. The uncertainty of the method is assessed using Monte Carlo simulations. Experimental results for various operating conditions are presented. For all investigated oil flowrates, the same characteristic behavior of the average heat transfer coefficient versus rotational speed was observed. This observation can be explained by using a kinematic model of the oil jet. The geometry of the gear and the cooling arrangement and the spatially resolved HTC data presented in this paper provide a complete basis for the validation of numerical simulations.

The Formation and Eruption of a Sigmoidal Filament Driven by Rotating Network Magnetic Fields

Abstract We present the formation and eruption of a sigmoidal filament driven by rotating network magnetic fields (RNFs) near the center of the solar disk, which was observed by the 1 m aperture New Vacuum Solar Telescope at the Fuxian Solar Observatory on 2018 July 12. Counterclockwise RNFs twist two small-scale filaments at their northeastern foot-point region, giving a rotation of nearly 200° within about 140 minutes. The motion of the RNF has a tendency to accelerate at first and then decelerate obviously, as the average rotation speed increased from 10 to 150° hr−1, and then slowed down to 50° hr−1. Coalescence then occurs between filaments F1 and F2. Meanwhile the fine structures in the southwestern region of the filament was involved in another interaction of coalescence. The subsequent EUV brightening due to plasma heating is observed in the two interaction regions. These interacting structures, including F1, F2 and the fine structures in the southwestern region, eventually evolve into a larger-scale sigmoidal filament twisted in the same direction as the RNFs gave. The twist of the sigmoidal filament has exceeded 4π and the filament finally erupted. The motion of the sigmoidal filament remains uniform until a nearby jet collides, causing the filament to erupt faster. These results provide evidence that RNF plays an important role in the formation and eruption of the sigmoidal filament. The phenomena also suggests that the kink instability is the trigger mechanism for the filament eruption.