Rotational Speed Of Rotor Research Articles

Effects of Wake Separation on Aerodynamic Interference Between Rotors in Urban Low-Altitude UAV Formation Flight

In recent years, unmanned aerial vehicle (UAV) formation flight has become an effective strategy for urban air mobility (UAM). However, close rotor separation during formation flight leads to complex aerodynamic interference between rotors, significantly affecting UAV flight performance and operational safety. This study systematically examines the effects of axial and lateral rotor separation on the rotor’s thrust performance through wind tunnel experiments. The tests simulate horizontal, vertical, and hovering states by generating relative airflow in the wind tunnel, focusing primarily on the thrust coefficient changes of the bottom rotor at various separations. The results are compared with a single rotor operating under the same conditions without wake interference. Additionally, computational fluid dynamics (CFD) simulations using the Fluent software were conducted to investigate the effect of wake interactions by analyzing the velocity flow field between the two rotors in different separations. Both the experimental and simulation results demonstrate that rotor aerodynamic performance is notably influenced by wake interactions. Under hovering and vertical states, substantial aerodynamic interference occurs in the region directly beneath the top rotor, within 1D ≤ Z ≤ 3D. This interference gradually diminishes as the rotor separation increases. Additionally, the thrust coefficient of the bottom rotor decreases with increasing flight speed due to the wake, and at higher flight speeds, the wake tends to contract. When the lateral separation is X = 0D, the mid-sectional flow field of the two rotors exhibits symmetry; however, with lateral separation, the symmetry of the bottom rotor’s wake velocity field is disrupted. During the horizontal flight, the rotor wake tilts backward due to the relative airflow, and the extent of this influence is governed by both rotor rotational speed and flight velocity. Therefore, when UAVs operate in formation, it is crucial to account for these factors affecting aerodynamic performance, and rotor separation must be optimized to enhance flight safety and efficiency.

Effect of shaft deflection on the dynamic behaviors of the ceramic bearing rotor system within wide temperature ranges

The shaft deflection has great impact on the dynamic characteristics of the ceramic bearing rotor system, which cannot be ignored within wide temperature ranges. This paper establishes a model considering the shaft deflection, and the impact of shaft deflection appears along with changes in bearing attitude. The interaction between the various components of the bearing is recalculated, and the dynamic behavior of the full ceramic bearing rotor system in wide temperature ranges is obtained based on the thermal deformation difference. The trends of dynamic behaviors with rotor mass, rotation speed and shaft length-diameter ratio are investigated, and comparisons between simulation and experimental results are conducted for verification. It is found that the shaft deflection makes impact by bringing in extra centrifugal force, and the effects are reflected in frequency components and trajectories. The simulation results with shaft deflection fit well with the experimental results, which proves that the dynamic model considering the shaft deflection better illustrates the dynamic behavior of the ceramic outer ring when the contact situations change with working temperature. The research carries out deep insight into the running of ceramic bearing rotor system, and provides guidance for the improvement of dynamic behaviors in wide temperature ranges.

SIMULATION OF TORQUE VARIATIONS IN A DIESEL ENGINE FOR LIGHT HELICOPTERS USING PI CONTROL ALGORITHMS

This article presents the results of simulation research of a diesel engine for a light helicopter. The simulations were performed using the 1D software AVL Boost RT. The engine model includes elements such as cylinders, turbine, compressor, inlet and outlet valves, ambient environment definition, and fuel injection control strategy. The simulations aimed to evaluate the engine's response to step changes in the main rotor load, both increasing and decreasing power demands. Parameters analyzed included power deviation, torque, engine rotational speed, and stabilization time of the main rotor rotational speed. All tests were conducted using a single set of PI controller settings. The results demonstrate that these parameters are dependent on the magnitude of the step change in the main rotor load demand. The study compares the maximum engine rotational speed deviation from the nominal value for both increasing and decreasing main rotor load demands. The findings indicate that using PI regulator to control rotational speed in the diesel engine in a light helicopter significantly depends on the change in the load torque on the rotor.

Optimising Flywheel Energy Storage Systems: The Critical Role of Taylor–Couette Flow in Reducing Windage Losses and Enhancing Heat Transfer

Amidst the growing demand for efficient and sustainable energy storage solutions, Flywheel Energy Storage Systems (FESSs) have garnered attention for their potential to meet modern energy needs. This study uses Computational Fluid Dynamics (CFD) simulations to investigate and optimise the aerodynamic performance of FESSs. Key parameters such as radius ratio, aspect ratio, and rotational velocity were analysed to understand their impact on windage losses and heat transfer. This study reveals the critical role of Taylor–Couette flow on the aerodynamic performance of FESSs. The formation of Taylor vortices within the airgap was examined, demonstrating their effect on temperature distribution and overall system performance. Through a detailed examination of the skin friction coefficient and Nusselt number under different conditions, this study identified a nonlinear relationship between rotor temperature and rotational speed, highlighting the accelerated temperature rise at higher speeds. The findings indicate that optimising these parameters can significantly enhance the efficiency of FESSs, reducing windage losses and improving heat transfer. This research provides valuable insights into the aerodynamic and thermal optimisation of FESSs, offering pathways to improve their design and performance. The results contribute to advancing guidelines for the effective implementation of FESSs in the energy sector, promoting more sustainable energy storage solutions.

Modeling the critical rotation speed of a bladed rotor with bent blades in a circulation mixer of feed mixtures

The purpose of the research is to substantiate the critical rotation speed of a rotor with bent blades based on force analysis and modeling the movement of mixture particles in a horizontal loader of a circulation mixer. The research method[1]ology included the substantiation of the highest rotation frequency of the loader blade rotor based on a force analysis of moving particles of forces when they were moved by the bent blades of the loader and compliance with the conditions for the entry of flying particles into the tray. The numerical analysis performed on the basis of the obtained expressions using the Mathcad mathematical package made it possible to establish the critical values of the rotation speed of the rotor-loader with bent blades based on the condition of the material coming off the blade and the condition of the flight of particles from the blade into the receiving tray. With radial blades, the limitation is the entry of particles into the receiving tray at a critical frequency of 43 min-1 , then for a blade bend of 30° – about 60 min-1 , for a blade bend of 45° – about 70 min-1, for a blade bend of 60° – about 80 min-1. The lowest critical values of the rotor-loader rotation frequency from the condition of particle movement along the blade correspond to the blade bend angle of 27–60° and are determined by the friction coefficient of the material, amounting to 83–78 min-1. With an increase in material friction, the critical values of the rotor rotation speed from the condition of material coming off the blade decrease slightly, and the bend angle for the rotation speed extremum increases. The highest rotation speed of the rotor - loader with a radius of 0.12 m is limited to 78 min-1 at a blade bending angle of the order of 30–60°, determined by the friction of the material on the blade.

Simulation of an induction generator for a wind farm

A pressing problem in the modern economy is still the problem of generating a sufficient amount of electricity. The situation is aggravated by environmental problems when using so-called carbon energy, as well as when using hydro and nuclear energy. The development of alternative sources of electricity is now impossible to imagine without the use of wind power plants. Wind energy is practically free energy, but its use involves the use of electric generators. Currently these are mainly synchronous generators, but induction (asynchronous) generators are also used. Despite the relative cheapness and reliability, however, induction generators occupy a very modest place in percentage terms among wind generators. One of the problems with using induction wind generators is that they require very significant reactive power during operation, which either comes from the network or is compensated by a capacitor bank. The latter is typical for autonomous induction generators. Computer modeling of induction wind generators is complicated by significant nonlinearity, which is caused by the magnetization curve or, what is the same, the no-load characteristics of the generator. As a rule, in computer modeling or simulation the inductive reactance of the magnetization branch is assumed to be constant, which is not entirely correct, since it is reliably known that it depends on the rotor rotation speed. A number of models of an induction generator are known, but so far there is no one most reliable mathematical model that allows computer studies of an induction generator with a squirrel-cage rotor, taking into account all its features. The MATLAB 2023b software package contains a mathematical model of an induction wind generator, which is of scientific and practical interest. The article examines the capabilities of this model, its advantages and disadvantages. The dependences of the influence of machine parameters on the generated active power and consumed reactive power were obtained, the influence of the inductive resistance of the magnetization branch and the influence of the nature of the load on the generated energy by the generator were assessed

Potential and Limitations of Anomaly Detection via Tower-Radar Monitoring of Wind Turbine Blades in Regular Operation with Convolutional Networks

The authors have already presented a first analysis of a field study on radar- based structural health monitoring of rotor blades on two operational wind turbines. This analysis will now be extended with measurements from a third operational wind turbine used as a case study for structural monitoring of individual rotor blades over different time intervals and blade modifications. More precisely, a sensor box with a 35 GHz FMCW radar and a highspeed camera was positioned at 90m height on the turbine tower, collecting radar data for structural information and videos for automatic ground truth labelling. After two months of collecting data, each individual rotor blade of that turbine was differently modified and measured again. The radar-facing surface of one rotor blade was partially coated with a microwave absorber foil, while an equivalent foil was applied to the backside of the second rotor blade. The third rotor blade was intentionally left unchanged for the sake of comparability. This study investigates potential limitations like general dataset complexity in radar-based anomaly detection for operational wind turbines. Furthermore, the discriminative ability of a convolutional neural network for classifying moving rotor blades is discussed when encountering feature drift through changing environmental and operational conditions, i.e. metadata like nacelle orientation, rotor blade pitch and rotation speed.

Use of Dampers to Improve the Overspeed Control System with Movable Arms for Butterfly Wind Turbines

To reduce the cost of small wind turbines, a prototype of a butterfly wind turbine (6.92 m in diameter), a small vertical-axis type, was developed with many parts made of extruded aluminum suitable for mass production. An overspeed control system with movable arms that operated using centrifugal and aerodynamic forces was installed for further cost reduction. Introducing this mechanism eliminates the need for large active brakes and expands the operating wind speed range of the wind turbine. However, although the mechanism involving the use of only bearings is simple, the violent movement of the movable arms can be a challenge. To address this in the present study, dampers were introduced on the movable arm rotation axes to improve the movement of the movable arms. To predict the behavior of a movable arm and the performance of the wind turbine with the mechanism, a simulation method was developed based on the blade element momentum theory and the equation of motion of the movable arm system. A comparison of experiments and predictions with and without dampers demonstrated qualitative agreement. In the case with dampers, measurements confirmed the predicted increase in the rotor rotational speed when the shorter ailerons installed perpendicularly to the movable arms were used to achieve the inclination. Field experiments of the generated power at a wind speed of 6 m/s (10 min average) showed relative performance improvements of 11.4% by installing dampers, 91.3% by shortening the aileron length, and 57.6% by changing the control target data. The movable arm system with dampers is expected to be a useful device for vertical-axis wind turbines that are difficult to control.

Colloid phase separation dynamics driven by chiral turbulent flows

Hydrodynamic interactions significantly influence phase-ordering kinetics in complex fluids. While passive fluid phase separation is well studied, the impact of active components remains relatively unexplored. We examine pure- and quasi-two-dimensional mixtures of attractive colloids and self-rotating particles in a solvent. Varying rotor rotational speed and area fraction yield diverse dynamic patterns such as percolated networks and round droplets composed of passive colloids alone. At intermediate rotation speeds, inertial chiral flows, accompanied by the inverse energy cascade, lead to self-similar power-law coarsening with a growth exponent of 1/2. The flows spontaneously organize within fluid domains, exhibiting turbulent and chiral characteristics. Surprisingly, these turbulent flows can sustain hexatic order hydrodynamically stabilized by the Magnus force under certain conditions. Conversely, at higher speeds, nonlinear hydrodynamic interactions impede phase separation. Our findings illuminate the intriguing dynamic interplay between phase separation and chiral turbulence, effectively bridging the realms of phase ordering and turbulent physics. Published by the American Physical Society 2024

LPT rotor speed after low-pressure shaft failure

When designing engine safety and compliance with airworthiness regulations, it is important to determine the variation of rotor rotational speed and other parameters of aero-engine under shaft failure scenarios. In this paper, a transient process simulation model is established using the component method for a high bypass ratio two-shaft direct-drive turbofan engine. It helps analyze the response of engine rotor speed and key temperature parameters after the failure of the low-pressure shaft, the influence of the fuel supply, low-pressure turbine efficiency, and rotor resistance torque on the response of the parameters. The results demonstrate that the sudden increase of the low-pressure shaft speed at the turbine end after the failure of the low-pressure shaft is the most important factor affecting the engine safety design. The fuel supply, LPT efficiency, and resistance torque have significant effects on this sudden increase in speed.

Modelling of aero-mechanical response of wind turbine blade with damages by computational fluid dynamics, finite element analysis and Bayesian network

Computational Fluid Dynamics and Finite Element Analysis structural models are developed for generation of large datasets of high-fidelity aerodynamic loading, displacement and stress for the NREL 5 MW wind turbine blade. Based on the datasets, analysis of structural responses of the turbine blade and their possible shifts with respect to a change in the operating conditions, e.g. rotor plane tilting and yawing, are performed. A Bayesian Network model is trained to produce ranges of values and likelihoods of occurrence of abnormal structural response or the most likely damage in the blade from inputs of operating conditions. The numerical analysis showed that yawing and tilting of rotor plane has very strong influence on the performance of a wind turbine. The out-of-plane bending is the dominant mode of the rotor blade while twisting and other complex modes of displacement could be more significant during some operating conditions such as at high tilt and yaw angles. The Bayesian Network is capable of computing probability mass functions of mechanical stress or displacement of the blade given a rotor rotation speed and a type of damage or vice versa, identifying a type of damage given a measured stress distribution level.

Effect of eccentric mass on rotor dynamics as a source of harvesting energy vibration

This research focuses on the potential for vibration energy from the use of eccentric masses in dynamic rotors to become an electrical energy source. Prior studies on eccentric mass in dynamic rotors were primarily concerned with examining the rotor's vibrational characteristics; however, little research was done on converting vibrational energy into electrical energy. The purpose of this study is to ascertain the maximum amount of electrical energy that can be produced by dynamic rotor vibrations using an eccentric mass. Utilizing an electromagnetic energy harvester, an experimental study is the methodology used. With a rotor rotation speed of 450 rpm, the eccentric mass variations used are 6.5 grams, 8.5 grams, and 10.5 grams. Matlab is used in this research to process data. The highest energy, using an eccentric mass of 8.5 grams, was found to be 24.15 mV. Nevertheless, this study shows that while the eccentric mass has an impact on the amplitude, it has no effect on the voltage. In order to increase and improve the efficiency of the electrical energy produced, further research on the utilization of vibration energy from dynamic rotors can be guided by the findings of this study

Vibration Mitigation Using 3D-PSTMD for the Offshore Wind Turbine Considering Self-Excitation Behaviors

The self-excitation behaviors can be triggered by the blade rotation of the wind turbine. To mitigate the excessive vibration of offshore wind turbine (OWT) tower under this self-excitation addition with wind–wave loadings, a three-dimensional prestressed TMD (3D-PSTMD) is extended in this study. First, based on the Lagrange equation, the analytical formulations of 1P (rotor rotational speed) and 3P (blade passing frequency) loads from self-excitations are deduced, and more factors under real operational conditions of the OWT are further analyzed using theoretical derivation and numerical simulation. Then, structural aero-hydrodynamic loadings are modelled, and self-resonance phenomenon of the uncontrolled OWT and resonance dissipation capability of 3D-PSTMD are discussed at startup–operation–shutdown state. Finally, the energy harvesting competence of 3D-PSTMD is quantitatively calculated via the classical Wilson-[Formula: see text] algorithm under self-excitations with wind–wave loadings. Results indicate that this dashpot is remarkably able to mitigate the structural resonance responses over 61.3% and 40.5% respectively when under the 1P and 3P loadings, and it can also effectively reduce the bi-directionally horizontal vibrations of OWT under aero-hydrodynamic loadings.

Nonlinear Dynamic Analysis and Forecasting of Symmetric Aerostatic Cavities Bearing Systems

Symmetric Aerostatic Cavities Bearing (SACB) systems have attracted increasing attention in the field of high-precision machinery, particularly rotational mechanisms applied at ultra-high speeds. In an air bearing system, the air bearing serves as the main support, and the load-carrying capacity is not as high as that of oil film bearings. However, the aero-spindle can operate at considerably high rotational speeds with relatively lower heat generated from rotation compared with that of oil film bearings. In addition, the operating environment of air bearings does not easily cause the rotor to deform. Hence, through adequate design, air pressure systems exhibit a certain level of stability. In general, the pressure distribution function of air bearings exhibits strong nonlinearity when there are changes in the rotor mass or rotational speed, or when the bearing system is inadequately designed. These issues may lead to instabilities in the rotor, such as unpredictable nonperiodic movements, rotor collisions, or even chaotic movements under certain parameters. In this study, rotor oscillation was analyzed using the maximum Lyapunov exponent to identify whether chaotic behavior occurred. Machine learning methods were then used to establish models and predict the rotor behavior. Especially, random forest and extreme gradient boosting were combined to develop a new model and confirm whether this model offered higher prediction performance and more accurate results in predicting tendencies with considerable changes compared with other models. The results can be effectively used to predict the SACB system and prevent nonlinear behavior from occurring.

The results of experimental research of a rotor seed-metering unit for sowing non-free-flowing seeds

The production and cultivation of new high-quality seed varieties are linked to the sowing of various crops with diverse physical and mechanical seed properties. Efficient seed-metering unit operation is critical during the technological process of fodder crop cultivation, predominantly when sowing non-free-flowing seeds. The quality of seed sowing and crop yield significantly rely on the design precision of seed-metering devices, technical maintenance and appropriate calibration. A rotary seed metering device was incorporated to ensure that non-friable seeds are uniformly sown, thus maintaining consistent seed supply and consumption at all stages of circulation. The study of the proposed device's productivity dependence on its operating parameters is justified because these variables affect crucial indicators such as the capacity to achieve and sustain the desired seeding rate over the entire operational duration. The study presents findings from an experimental investigation on sowing non-free-flowing (non-flowing) and finely dispersed seeds using a rotor seed-metering unit. The tests aimed to ascertain the precision and evenness of sowing such crops. It was observed that the speed of rotation of the seed-metering unit's vane disk is a key factor in the uniformity and supply of sown seeds. The limits of variation in rotor rotation speed and rotor seed-metering unit productivity per second were established to guarantee the desired seeding rate for various crops, including alfalfa, Agropyron, and Bromus inermis.

Understanding the fixed pitch RPM-controlled rotor modeling for the conceptual design of UAM vehicles

AbstractMost of the introduced eVTOL models in the UAM market utilize electrically driven rotors with fixed pitch blades, controlled by their rotational speed. This design approach brings new features and challenges that need to be considered during the conceptual design stage, taking new aspects into account, among them the rotor dynamic response. This paper presents an initial parameterization of the rpm-controlled rotors along with the electric motor, based on the conducted literature research. Several isolated rotor variants are modeled and analyzed in terms of performance, and the dynamic response of the rotor rotational speed. The relations between aerodynamics and inertia are discussed, and their effects on the rotor dynamic response are elaborated on.

Impact of solidity and speed ratio on the performance of a contra-rotating fan

In this study, the effects of solidity and rotor speed ratio on the performance of a contra-rotating fan are investigated numerically. Simulation results have been validated by experimental tests. The test stand construction and the measurements have been performed according to ISO-5801 standard. In order to investigate the effect of blade solidity, simulations have been conducted with constant blade count of the front rotor and four configurations of the rear rotor (having 6, 8, 12 and 16 blades), and also constant blade count of the rear rotor and three configurations of the front rotor (having 8, 12, and 16 blades). Results suggest that there is an optimum solidity for the rear rotor, which gives maximum pressure rise and efficiency. Furthermore, the effects of the rotor speed ratios have been investigated in this study. It is shown that the speed of the front rotor is more effective on the fan performance, as compared to the rear rotor. Results reveal that the performance drop caused by a 25% reduction in the rear rotor blade count, can be compensated by 5% increase of the front rotor rotational speed. Therefore, a suitable choice of the speed ratio can result in light-weight and high-performance contra-rotating stages.

Cooling of a synchronous electric motor using an axial air flow

The current work investigates the rate of cooling of an axial air flow through the gap between the stator and the rotor of a four-pole synchronous electric motor. The axial air is passing though the rotor's four longitudinal slots. The stator is considered insulated. The effect of the axial air flow rate, the rotor rotational speed and the slot size on the average Nusselt number has been investigated numerically using ANSYS-CFX. These effects have been studied considering a motor radius ratio (RR) in the range of 0.65–0.85, an axial Reynolds number (Rea) between 1750 and 40,000 and a rotational Reynolds number (Rer) of 1750 up to 35,000.Numerical results have been validated using published experimental data. The maximum deviation was less than 15 %. The present numerical results showed that increasing the axial air flow rate always enhances the rate of cooling. The effect of the axial Reynolds number was found to be more dominant than that of the rotational Reynolds number. Increasing the rotor rotational speed (Rer) enhanced the rate of heat transfer up to a certain limit beyond which a revered effect was observed. Such limit was investigated and found to depend on the motor radius ratio and the relative magnitude of the axial and rotational Reynolds numbers represented by X = Rea/Rer. The enhancement due to increasing Rer was reversed at X = 0.33 and 0.12 when RR was at 0.85 and 0.75, respectively. A new correlation of the average Nusselt number as a function of the axial and rotational Reynolds number has been developed.

Dry beneficiation of bentonite using dynamic separator

Beneficiated bentonites, which contain predominantly smectite minerals, have many uses, such as pharmaceuticals, cosmetics, and advanced composite materials. The beneficiation of bentonites using dry processes is essential to being economical, fast, and accessible. This study developed a new method for the dry beneficiation of bentonites, and for this, a laboratory-scale dynamic separator was used as beneficiation equipment. A stirred media mill was used for grinding raw bentonite before beneficiation studies. The effects of the airflow rate and rotor rotation speed, which are the operating parameters of the separator, on the separation and beneficiation efficiency according to the particle size were investigated in detail. Quartz, opal, muscovite, and feldspars were removed from the raw bentonite sample, while small amounts of calcite and clinoptilolite minerals remained. It was determined that the amount of concentrated product obtained in this way, which had the d90 value of 23.6 μm, was 19.4% compared to the amount of product fed.

Совершенствование проточной части газосепараторов с использованием мультифазного коэффициента относительной скорости движения дискретных частиц

The paper analyzes features of the flowing formation fluid that contains free gas bubbles in the flow part of a vortex-type separator with the movable screw. Expressions are derived for a dimensionless multiphase coefficient of the discrete particles relative separation rate and the multiphase similarity criterion, which are making it possible to evaluate the gas separator efficiency, design and develop new devices based on the previously created highly efficient models. The derived equations allow determining the main geometric dimensions of the gas separator flow part based on the given radial dimensions, nominal flow rate and permissible content of free gas at the inlet. For the obtained geometric dimensions of the gas separator flow part, it becomes possible to construct dependences of the separation coefficient and the permissible amount of free gas at the inlet on the rotor rotation speed, flow rate and physical properties of the multiphase mixture.