Rotor Speed Research Articles

Oscillating surge wave energy converter using a novel above-water power takeoff with belt-arc speed amplification

We investigate the performance of a novel power takeoff (PTO) featuring belt-arc speed amplification for oscillating surge wave energy converters (OSWECs), aiming to address the PTO design challenges of extremely low rotary speed and large torque under the low-frequency and large energy density ocean wave excitations. The belt-arc design significantly increases the rotary speed of the generator, enabling generator downsizing and decreasing the powertrain friction losses. The design also allows for placing the generator above water, eliminating the need for high Ingress Protection ratings for the generator and powertrain, and potentially leading to substantial reductions in capital and maintenance costs. Using the potential flow theory, the dynamics of the integrated system are analyzed, and key parameters are identified. To validate the numerical analysis, a 1:10 scale model is designed, fabricated, and tested in a wave tank. Performance evaluations are conducted under regular and irregular wave conditions, with quantified effects of parameter tuning. The results reveal an optimal wave-to-electric efficiency of 48% under regular wave excitation and 20% under irregular excitation. These findings underscore the effectiveness of the proposed novel PTO design in addressing the challenges of low rotation speed and large torque inherent in OSWECs, demonstrating its ability to efficiently convert wave power into electricity.

Hydraulic loss analysis of turbodrill blade cascades based on entropy production theory

Turbodrill is a kind of high-temperature resistant downhole motor which is commonly used in drilling deep and high-temperature wells. It belongs to multi-stage axial flow turbomachinery. There are complex flow losses in turbodrill blade cascades, but conventional flow-loss evaluation methods cannot obtain the location of losses in cascades. The entropy production method constructs the relationship between flow field parameters and flow losses, so the location where flow losses generate can be obtained, which is commonly used to analyze the flow losses in various flows. In this paper, entropy production method is used to obtain the magnitude and position of hydraulic losses in turbodrill blade cascades. The single passage calculation model of three-stage stator and rotor is established, and CFD method is employed to compute the flow field parameters at different viscosities and rotary speeds. Different kinds of entropy production rates and values are calculated. Finally, the total flow loss calculated by entropy production method is compared with that calculated by pressure difference method, and the contrastive result is very similar, which indicates the correctness of entropy production method. The results show that the high entropy production regions are mainly located near the walls and the position changes with variations in rotary speed and viscosity, and the stator entropy production value is always lower than that in rotor. In addition, when the fluid viscosity is low, the main types of entropy production are turbulent entropy production and wall friction entropy production, while when the fluid viscosity is high, the main types of entropy production are direct entropy production and turbulent entropy production. Furthermore, the rotary speed variation has a greater impact on turbulent entropy production and wall friction entropy production compared to viscosity change, while the viscosity change has a greater impact on direct entropy production than the variation rotary speed. This paper introduces entropy production method into flow losses analysis for turbodrill, presenting a new approach for studying flow losses and providing a reference for improving turbodrill design.

On the optimal multi-objective design of fractional order PID controller with antlion optimization

This study introduces an optimal multi-objective design approach for a robust multimachine Fractional Order PID Controller (FOPID) using the Antlion algorithm. The research focuses on the need for effective stabilizers in multimachine power systems by employing traditional speed-based lead-lag FOPID controllers. The study formulates a multi-objective problem, optimizing the damping factor and damping ratio of lightly damped electromechanical modes to maximize a composite set of objective functions, tackled through the Antlion algorithm. Stability analysis of Single-Machine Infinite-Bus (SMIB) and multimachine power systems is conducted based on rotor speed and power deviation minimization in the time domain response, along with damping ratio and eigenvalue analysis. The proposed approach is implemented and tested on three IEEE test cases, showcasing significant improvements in stability through the reduction of maximum overshoot (Mp) and settling time (ts) of speed deviation. Comparative analysis with other optimization-based FOPID controllers underscores the superiority of the proposed approach in enhancing stability in multimachine power systems. The main impact of this research lies in its contribution to the advancement of stability enhancement techniques in multimachine power systems, offering a systematic framework for optimal FOPID controller design and empowering decision-making processes in power engineering.

Time‐Frequency Analysis of Experimental and Analytical Rotor Thrust during a Rotor Speed Change

A study was conducted examining a small-scale, two‐bladed rotor undergoing a change in rotor speed. The data acquired consists of time histories of nonstationary signals; therefore, a Stockwell transform was employed to analyze the data in lieu of traditional Fourier transform-based methods. The analysis included extraction of time‐varying frequency content of the rotor thrust and hub motion, instantaneous rotor speed, damping ratios, and instantaneous phase difference between thrust and hub motion. This work is divided into two parts. First, an analytical study was conducted to understand how rotor transient response, determined using a time‐marching solution, is affected by the inclusion of a simplified elastic support structure model, and is used to demonstrate the utility of the Stockwell transform. The second part of the study compared the results from an analytical model of the NASA Multirotor Test Bed (MTB) undergoing a rotor speed change to wind tunnel data. The current analytical model of the MTB, including an elastic support structure, properly predicted the measured trends in the frequency content of the thrust; however, it underpredicted the amplitude of these unsteady loads.

Flow Field Analysis on Critical Feedback Information for UAV Autonomous High Speed Descent in Power Line Scenario

Abstract To improve the UAV efficiency in power line inspection, it must autonomously and rapidly descend to a specific height to complete the charging or landing task. This task requires the UAV to contain a stable control loop to face the specific airflow during autonomous and rapid descent: the vortex ring problem, and this specific airflow will reduce the UAV controllability. To implement the UAV autonomous high-speed descent, a control method must provide feedback information on the affected airflow and output a stable rotational speed. Hence, this paper designs a UAV autonomous high-speed descent control loop and proposes a variable rotor speed method to solve the feedback information in the control loop. This method reveals the relationship between the air movement caused by the rotor rotation and the controllability of the UAV high-speed descent. Therefore, with this method, the UAV control loop can obtain stable feedback on the air movement and achieve autonomous high-speed descent. To solve the UAV feedback information, we built the model to calculate the rotor speed in the autonomous high-speed descent UAV control loop and verified it by the CFD. The verification results showed that the model could reflect the actual fly condition. The proposed method solves the problem of UAV autonomous high-speed descent feedback information, improving the work efficiency of UAVs in power line inspection operations.

In-situ monitoring of an offshore wind turbine blade using acceleration and strain measurements

One of the most critical components of wind turbines is the blades. As blades are constantly exposed to weather and high loads, they can wear and become damaged. Performing in-situ continuous monitoring can help detect sudden damages and prevent further degradation, which is imperative to avoid economic losses and fatal accidents. However, monitoring a rotating rotor blade presents some challenges. One challenge is the consideration of lightning protection. Hence, a non-conductor measurement system must be used. Another challenge is system identification and modal tracking considering environmental and operational conditions (EOCs). Furthermore, vibration-based monitoring results from actual and operational rotor blades are scarce in the existing literature. This study centres on operational modal analysis (OMA) using covariance- driven stochastic subspace identification (SSI-COV) of an offshore wind turbine blade in operation employing eight months of data from fibre optic accelerometers (FOA) and fibre Bragg grating (FBG) strain gauges. The identification focuses on the first two bending modes in flapwise and edgewise directions and the first torsional mode. The study aims to determine which fibre optic sensor delivers better results. Furthermore, it addresses the effect of EOCs on the modal parameters, where system identification and modal tracking are discussed. It was found that tracked modes showed similar trends with respect to time, and a high connection was observed between wind speed, rotor speed, and pitch angle with frequency and damping. Additionally, acceleration and strain measurements deliver the same frequency and damping values. FBG better identified the first flapwise mode. On the other hand, FOA was superior in almost all other modes. This study points towards employing FOA for vibration-based monitoring of wind turbine blades using modal parameters.

Aero-engine performance evaluation model in the entire flight envelope

Abstract An aero-engine performance characteristics mathematical model in the entire flight envelope is proposed based on the stratification analysis method and multi-condition test data. The thrust, fuel flow, low/high-pressure rotor speed, exhaust temperature, and other engine output parameters can be calculated in the entire flight envelope, according to the engine operating characteristic model and input parameters of aircraft flight altitude, velocity, ambient temperature, throttle angle, etc. Based on the evaluation model proposed in this paper, the evaluation data of an aero-engine is consistent with the test data, and the error is less than 5%. The research and model can support flight performance calculation and mission planning and can be applied to flight simulator engine modules.

A comparison of static and rotordynamic characteristics for two types of liquid annular seals with and without helical grooved stator

Less leakage is a benefit of parallel grooved liquid seals (labyrinth seals). But researches show that the liquid seal with parallel grooves on the rotor harms the rotor stability. The seal with helical grooves on stator performs well in terms of rotordynamics, and its leakage is sensitive to the rotating speed. To make use of the advantages of both seals and improve seal stability, based on the Smooth-stator/Parallel Grooved-rotor (SPG) liquid seal, a Helical Grooved-stator/Parallel Grooved-rotor (HGPG) liquid seal is designed. To evaluate two liquid seals’ leakage, rotordynamic characteristics and drag power loss, a transient computational fluid dynamics-based method is employed. This method is based on the multi-frequency elliptical-orbit rotor whirling model and the mesh deformation technique. The published experimental data of the leakage and rotordynamic force coefficients for an SPG liquid seal are used to validate the accuracy and dependability of the current method. Seal leakage and force coefficients are presented and compared for the SPG liquid seal and the HGPG liquid seal at various pressure drops. The influences of parallel groove depth on the leakage and rotordynamic properties for the HGPG liquid seals at two rotational speeds (2000, 6000 r/min) are analyzed. The numerical findings demonstrate that the novel HGPG liquid seal has a lower leakage flow rate (by ∼22.3%) than the traditional SPG liquid seal. There is an optimal parallel groove depth that minimizes leakage. The presented novel HGPG liquid seal significantly improves rotordynamic stability, due to the similar effective stiffness and the obviously larger positive effective damping. Reducing parallel groove depth can increase the positive effective damping. In terms of leakage and rotordynamic characteristics, the novel HGPG liquid seal is a better seal design for liquid turbomachinery.

Method for Two-Stage Radar Measurement of the Blade Repetition Rate of a Propeller-Driven Aircraft

Introduction. Radar images of aircraft propellers can significantly improve the quality of their recognition and protection against simulating interference. Such images can be obtained using algorithms based on an inverse antenna aperture synthesis. A key factor determining the quality of image acquisition is the accuracy of the rotor blade rotation frequency measurement. In 2019, a method for measuring the blade repetition rate was proposed, which is based on convolution of the "secondary" signal modulation spectrum while simultaneously eliminating the influence of the Doppler frequency of the signal reflected from the aircraft body. In sequential analysis, the number of cycles is determined by the ratio of the maximum blade repetition rate (hundreds of hertz) to the discrete frequency shift (thousandths of hertz). In this case, to solve the measurement problem, the required number of cycles should be hundreds of thousands, which is expensive in terms of practical implementation.Aim. Development of a two-stage method for measuring the blade repetition rate, which allows the number of signal convolution cycles to be reduced by hundreds of times.Materials and methods. The proposed method is aimed at implementing adaptation circuits to an a priori unknown rotor speed of an aircraft, which can be determined based on the blade rotation frequency. The method involves measuring the blade frequency in two stages: a rough measurement of the blade frequency rate followed by its accurate measurement within the limits of the maximum errors of the rough measurement.Results. A method for a two-stage measurement of the blade repetition rate as applied to the construction of radar images of aircraft propellers is proposed. The feasibility of the method is illustrated by the example of a signal reflected from a Mi-8 helicopter. The requirements to the measurement error of the blade repetition rate and to the frequency analysis step at the precise measurement stage are formulated. The requirement to the repetition rate of probing signals is substantiated, the fulfillment of which ensures an unambiguous restoration of the spectrum of "secondary" modulation of the signal reflected from the blades of a propeller-driven aircraft.Conclusion. The developed method for a two-stage measurement of the blade repetition rate ensures the adaptation of algorithms for constructing radar images of aircraft propellers to their rotation frequency.

Modeling the Coupling of Rotor Speed, primary Frequency Reserve and Virtual Inertia of Wind Turbines in Frequency Constrained Look-Ahead Dispatch

Modeling the Coupling of Rotor Speed, primary Frequency Reserve and Virtual Inertia of Wind Turbines in Frequency Constrained Look-Ahead Dispatch

Research on Mathematical Model of Energy Storage Assisted Wind Turbine Frequency Regulation Control Strategy

Abstract This paper proposes an improved frequency regulation strategy for the Doubly-Fed Induction Generator (DFIG) to mitigate the impact of wind power integration on system frequency. An energy storage system is used on the wind side to participate in the frequency regulation. The influence of wind power integration on the power system frequency is analyzed and an improved frequency control strategy for the DFIG is proposed. A control strategy for energy storage devices to support wind turbine frequency control is proposed. An energy storage device model is established that considers power correction based on the state of charge to avoid excessive charging and discharging. According to the operating state of the DFIG, a control strategy for the frequency regulation of the energy storage device is proposed. According to different wind speeds, a control strategy is proposed for the participation of the joint wind storage system in the frequency regulation. This control strategy can provide frequency support to the system when the wind turbine cannot participate in frequency regulation according to the different operating conditions of the wind turbine. After the wind turbine uses the improved frequency control strategy, it accelerates the recovery of the DFIG rotor speed while avoiding a secondary drop in the system frequency. In addition, when the energy storage device has a poor state of charge and the system frequency is good, it charges to restore the state of charge.

Rotor speed signature analysis‐based inter‐turn short circuit fault detection for permanent magnet synchronous machines

AbstractA rotor speed signature analysis‐ (RSSA‐)based inter‐turn short circuit (ITSC) fault diagnostic method is proposed, which is robust with regard to speed‐ and current‐loop bandwidths of permanent magnet synchronous machine (PMSM) drive systems. Conventional ITSC fault detection solutions that rely on current signals or extra devices. Thus, an initial step of investigation on the validity of RSSA is taken for residual insulation capacity monitoring of the ITSC fault at the incipient stage. The Vold–Kalman filtering order tracking method is employed for the real‐time extraction of fault features. Besides, the impact of speed‐ and current‐loop controller bandwidths on ITSC fault diagnosis is also analysed and an Adaline estimator is designed to decouple their impacts. Finally, the effectiveness of the proposed method is verified on a faulty PMSM, which exhibits satisfying results in tracking the degradation of residual insulation, even if the phase currents are significantly distorted due to low switching frequency of the inverter.

Rolling Bearing Fault Diagnosis Based on MResNet-LSTM

In response to the challenges of weak fault characteristics and complex and variable working conditions of roll-ing bearings in strong noise environments, a diagnostic methodology is proposed. This method integrates a multi-scale residual neural network (MResNet) and a long short-term memory (LSTM) neural network to achieve fault diagnosis of bearings under both constant and variable rotational speed working conditions. First, complete an ensemble empirical mode decomposition with adaptive noise (CEEMDAN) that is applied for vibration signal denoising. Secondly, a dropout layer is introduced between multi-scale residual blocks to prevent net-work overfitting, and the powerful time series information capture ability of LSTM is combined to improve di-agnostic accuracy. Finally, experimental verification is conducted using constant and variable speed bearing data sets. The results show that the proposed approach maintains strong diagnostic capabilities when the rotat-ing speed conditions change, and the signal is heavily polluted by noise.

RMSE POWER COEFFICIENT OF WIND TURBINES WITH INVERSE TOQUE-SPEED CONTROL

The Blade Element Momentum (BEM) method stands out among various turbine modelling techniques due to its integration of airfoil aerodynamics with momentum theory, allowing detailed force calculations on blade elements. While traditional methods like BEM and Wake Models are efficient for initial turbine design, advancements in computational power have enabled the use of Computational Fluid Dynamics (CFD) for more accurate simulations. Although these models are precise, they are computationally intensive, leading to the continued use of simpler empirical methods, such as the static power coefficient approach, in power system studies. Future research aims to validate and implement dynamic estimation models to account for wind variability and turbine control dynamics. Traditional constant torque-speed control strategies maintain a constant generator speed by using a fixed electromagnetic torque command and adjusting the pitch angle when wind speed exceeds the rated value. However, if the pitch control does not respond quickly enough, rotor acceleration can occur, leading to increased power beyond the generator’s rating. To mitigate this, the pitch control mechanism must react promptly to adjust the turbine's torque profile, ensuring convergence to the rated operating point and avoiding prolonged generator overload. To reduce the burden on the pitch-control system, an inverse torque-speed control approach is proposed, where the electromagnetic torque is dynamically adjusted based on real-time rotor speed data. This method aims to achieve rated power operation with improved responsiveness and reduced stress on the pitch-control mechanism.

Development of a control co-design optimization framework with aeroelastic-control coupling for floating offshore wind turbines

Sequential design optimization is frequently used to design floating offshore wind turbines. This method simplifies the design problem by implementing each of the disciplines successively and independently with the direct/dynamic coupling between them neglected. However, if the coupling between disciplines is strong, the global optimum may not be found by sequential design. Control co-design optimization is an approach that integrates all physics in a single optimization formulation to achieve the global optimum. However, it is challenging to achieve due to the highly complex system-control coupling in floating offshore wind turbines. This paper describes a control co-design optimization framework developed for floating offshore wind turbines. In particular, the blade airfoil chord and twist distributions are parameterized to change aerodynamics while the blade structural characteristics can be updated. The rotor speed and blade pitch controllers are tuned automatically based on the properties of the new plant model. For demonstration, a 10 MW reference wind turbine is used in the case study. The annual energy production is maximized, and the blade mass is minimized. The blade shape and control parameters are optimized simultaneously, subject to constraints on geometric design variables, fatigue loads, ultimate loads, and blade deflection. To solve this high-dimensional, nonlinear, and constrained problem, a genetic algorithm is used, and the Pareto front of the design space is found. The design solutions on the Pareto front showed an improvement in the blade mass and annual energy production. These design alternatives also showed reduced structural ultimate and fatigue loads, and generator torque. This revealed the potential of control co-design to reach a better performance than the sequential method.

Vibration characteristics of dual-rotor system with staggered-type double elastic ring squeeze film dampers under maneuvering flight

The vibration of the rotor system is significantly intensified during maneuvering flight, rendering traditional elastic ring squeeze film dampers (ERSFDs) insufficient or unstable. To improve the applicability of dampers, a novel structure of staggered-type double elastic ring squeeze film dampers (SDERSFD) is proposed in this paper. Through the synergistic effect of double elastic rings, the damping effect is significantly enhanced, and the circumferential stiffness anisotropy of the damper is improved, which is more suitable for vibration reduction requirements under complex working conditions. Utilizing the Reynolds equation, the internal and external pressure field control equations of the double elastic rings are established. The finite difference method is then employed to solve the dynamic characteristics of the damper. Additionally, a finite element model of the dual-rotor system with SDERSFDs considering complex dynamic factors such as unbalanced force, oil film force, gravity, and additional inertial force caused by maneuvering flight is established for the study of nonlinear rotor dynamic characteristics and the analysis of SDERSFDs vibration reduction effect. Based on the model, the influence of various factors such as maneuvering speed, maneuvering radius, rotor speed and unbalance on the transient response of dive-pull up condition is analyzed. The results reveal that during dive-pull up, the vibration of the rotor system intensifies significantly. When compared with the ERSFDs, the SDERSFDs effectively reduce the vibration amplitudes of the rotor system under maneuvering flight condition, achieving the maximum vibration reduction ratio of 48.9%. Furthermore, the SDERSFD exhibits robustness against large maneuvering loads, enhancing the stability of the rotor system under extreme conditions.

Coordinated Frequency Modulation Control Strategy of Wind Power and Energy Storage Considering Mechanical Load Optimization

When a doubly fed induction generator (DFIG) participates in primary frequency modulation by rotor kinetic energy control, the torque of the generator is changed sharply and the mechanical load pressure of the shaft increases rapidly, which aggravates the fatigue damage of shafting. In order to alleviate the fatigue load of shafting, energy storage was added in the primary frequency modulation of a wind turbine, and a coordinated frequency modulation control strategy of wind power and energy storage based on fuzzy control was proposed. The wind-storage frequency modulation power command was allocated to reduce the response speed of the wind turbine to alleviate the load pressure on the shafting by the fuzzy controller considering the rotor speed range and the state of energy storage charge, and the remaining demand power was supplemented by energy storage. Finally, the joint simulation model based on GH Bladed–Matlab was used to verify the effectiveness of the proposed control strategy. Compared with the traditional integrated control of virtual inertia, the proposed method can reduce the load pressure and fatigue damage of the shafting while satisfying the requirement of frequency modulation.

Distributed coordinated speed control of flywheel energy storage matrix systems with model uncertainties and disturbances

SummaryThis paper studies a coordinated rotor speed control of flywheel energy storage matrix systems (FESMS) in the presence of model uncertainties and unknown disturbances. We consider the scenarios that the torque variation during the operation of flywheel energy storage system (FESS) cannot be accurately measured and the coordinated operation of FESMS is realized without the measurements of accurate rotor speeds. We design a distributed extended state observer (ESO) only using local rotor position measurements to estimate the rotor speeds and unknown disturbances. Based on the estimated states, a coordinated control strategy with the compensation of model uncertainties and unknown disturbances is proposed. The proposed control strategy has the advantage of speed‐free feature and active disturbance rejection. By using Lyapunov stability theory, sufficient conditions are given to ensure that the FESMS can achieve the reference tracking. The performance of the control strategy is verified by simulations.

Improved Design and Simulation of an Integrated Ridge-Breaking Earth Cultivator for Ratoon Sugarcane Fields

Ridge-breaking earth cultivation is a new agronomic technology that simplifies and efficiently cultivates ratoon sugarcane. However, traditional cultivators cannot adapt to the distribution of residual stumps, inter-row specifications, and hardened clay soil. This results in substandard soil fragmentation, poor ridge quality, and reduced operational reliability. To address these issues, this article proposes an integrated earth cultivator structure capable of breaking ridges, loosening soil, and raising ridges simultaneously. It is designed to enhance the breaking of tillage layers and the filling of ridges through the coordinated action of multiple soil-engaging components. The effects of pre-loosening by the ridge-breaking plow, high-energy crushing, and throwing by the spirally arranged dense rotary blade group, and soil gathering by the deflector are comprehensively utilized. Additionally, lateral pushing by the ridging plough is employed. Discrete element and finite element simulation results show that densely toothed blades can improve soil supply capacity and structural reliability. This is achieved by increasing the amount of soil throwback and reducing concentrated stress levels. Soil fragmentation rate (SFR) and ridge height (RH) were further used as indicators. Field experiments were conducted to study the effects of operating parameters on breaking and ridging performance. The optimal parameter solution was determined as a forward speed of 0.85 m·s−1 and rotary speed of 289.7 r·min−1. With this adaptive configuration, SFR and RH were improved by 12.4% and 38.5%, respectively, compared with conventional earth cultivators. Additionally, the RSM value of rotary tillage power (Pr) was reduced by 39.6%. Improvements in crushing hardened fields, constructing ridges, and reducing cutting energy consumption have proven effective. This study can provide a reference for the development of earth cultivators based on new agronomy and specific field characteristics.

Development of Active Wind Vane for Low-Power Wind Turbines

This paper proposes the development of an active control system to control the power output of a low-power horizontal-axis wind turbine (HAWT) when operating at wind speeds above the rated wind speed. The system is composed of an active articulated vane (AAV) in charge of the orientation of the wind turbine, which is driven by an electric actuator that changes the angle of the AAV to maintain a constant power output. Compared with the passive power regulation systems most often used in low-power HAWTs, active systems allow for better control and, therefore, greater stability of the delivered power, which reduces the structural stresses and allows for controlled braking in any wind condition or during system failures. The control system was designed and simulated using MATLAB R2022b software, and then built and evaluated under laboratory conditions. For the control design, the transfer function (TF) between the pulse width modulation (PWM) and the AAV angle (θ) was determined via laboratory tests using MATLAB’s PIDTurner tool. For the simulation, the relationship between the power output and the AAV angle was determined using the vector decomposition of the wind speed and wind rotor area. Wind speed step and ramp response tests were performed for proportional–integral–derivative (PID) control. The results obtained demonstrate the technical feasibility of this type of control, obtaining settling times (ts) of 6.7 s in the step response and 2.8 s in the ramp response.