Turbine Rotor System Research Articles

Numerical Simulation and Experimental Study on Dynamic Characteristics of Gas Turbine Rotor System Subjected to Ship Hull Excitation

Numerical Simulation and Experimental Study on Dynamic Characteristics of Gas Turbine Rotor System Subjected to Ship Hull Excitation

Numerical simulation and experimental study of the dynamic characteristics of a gas turbine rotor system with beam sea and head sea excitation

Vibration analysis is crucial for studying rotor dynamics. The gas turbine rotor system is subjected to complex alternating loads during navigation, resulting in vibrations transmitted to the bearings that alter the system’s dynamic characteristics. Based on the similarity law of the wave resistance test, a hull model was established. Beam sea and head sea tests were conducted in the towing pool to measure the acceleration response at the key positions. A finite element model of the turbine rotor system was established, and the test data were imported into the model after wavelet noise reduction and resampling to calculate the vibration response at the front and rear bearing points. The vibration responses transmitted to different locations and directions caused by beam sea and head sea conditions were analyzed. A comparison and analysis were conducted on the acceleration responses in various locations and directions under beam sea or head sea conditions. The equivalent von Mises stress distribution of the gas turbine rotor system under beam sea and head sea loads was obtained. The vibration transfer model was verified for accuracy and can be used to quickly analyze the vibration response of bearings under wave load transfer. This study provides a theoretical basis and reference for enhancing the stability of the gas turbine rotor system.

Nonlinear modeling and vibration response analysis of rod fastening rotor-bearing system with curvic coupling

Rod fastening combined rotor system (RFCR) are particularly popular in gas turbine rotor systems. The bolted connection introduces a discontinuity in this RFCR, which has a substantial influence on system performance.Traditional models of RFCR tend to neglect the influence of the connection structure, especially failing to fully consider the contribution of the curvic coupling to the rotor dynamics. To address this problem, this study proposes a new nonlinear analytical model of the rotor system, which focuses on the impact of the curvic coupling. This study provides a detailed analysis of the structural parameters and load forces of the curvic coupling. Based on this analysis, a mechanical model is created to assess how bolt preload and torque impact the stiffness of the curvic connection. The stiffness matrix of the curvic coupling is derived by the gear stiffness analysis method, and the accuracy of the model is confirmed using the finite element method. Furthermore, the model also considers the viscous and sliding state between the curvic coupling, which effectively describes the damping effect of the curvic coupling. On this basis, the motion control equations for the RFCR are formed, and a dynamic model considering the curvic connection in the RFCR system is introduced. The results show that the curvic coupling results in a decrease in stiffness and the occurrence of nonlinear damping phenomena in the RFCR.The RFCR exhibits a significant stiffness loss compared to the continuous rotor system, resulting in a decrease in the critical rotor speed. The nonlinear damping is mainly excited at high friction coefficient conditions and may lead to a self-excited vibration component in the rotor response at supercritical speeds. The negative impact of structural discontinuities on rotor dynamic performance can be reduced by increasing the bolt preload, decreasing the friction coefficient, and adjusting the amount of imbalance. This study offers a theoretical foundation for predicting curvic coupling-induced instability and serves as a reference for enhancing rotor system stability.

A Hybrid Testing Framework for Wind Turbine Mechanical Components

As wind turbines continue to increase in size, hybrid testing is emerging as a key-enabling solution for experimental assessment of their large mechanical components. Hybrid testing is conducted using a hybrid model which combines physically tested and numerically simulated components. In this work, the Kane method is proposed to formulate the equation of motion for the hybrid model of a wind turbine rotor system where one single blade is physically tested. The Kane method allows for formulating the equation of motion of multi-body-dynamic models efficiently and, therefore, it is widely used in state-of-art simulation software. The hybrid model of the rotor is successfully implemented on a single-degree-of-freedom test bench with a cantilever steel beam serving as the physical substructure. The performance of the implemented hybrid model is assessed through a comparison with a pure numerical simulation of the same system. The main finding of the study emphasizes the efficiency of incorporating physically measured restoring force as model parameters while formulating the equation of motion of a hybrid model.

Analysis of frequency characteristics of power system with wind farm-energy storage coordinated inertial control

With the increasing penetration level of wind power in the power system, the decoupling of wind turbine rotor speed and system frequency has led to the loss of the inertia of wind farms (WF), which can no longer be neglected. With the continuous development of energy storage (ES) technology, WF-ES coordinated inertial control has attracted attention as an effective means for wind turbines (WT) to participate in inertia response. How to build a WF-ES coordinated inertial control strategy and analyze system frequency characteristics has become a key research issue. In this paper, the frequency response model of a power system with WF-ES is established using the system frequency characteristic analysis method. The wind speed zones of the WF are taken into account, and different WF-ES control schemes are adopted under different wind speeds, aiming to ensure the active participation of WTs in the system frequency process across all wind speed conditions and effectively prevent frequency secondary drop. Finally, a power system frequency response simulation model is built in Matlab/Simulink to analyze the frequency characteristics of the power system with WF-ES coordinated inertial control and verify the feasibility of the proposed WF-ES coordinated inertial control strategy under various wind speeds.

Dynamic investigation of 650 W roof-top horizontal wind turbine rotor system supported by radial permanent magnet bearings

Dynamic investigation of 650 W roof-top horizontal wind turbine rotor system supported by radial permanent magnet bearings

Dynamic modeling and vibration analysis of offshore wind turbine rotor system with insulated bearing under inclined shaft current damage

The offshore wind turbine is a device that uses the wind energy on the ocean to generate electricity. The voltage generated by offshore wind turbine can break down the insulated bearing and cause inclined shaft current damage. To explore the dynamic characteristics and influencing factors of offshore wind turbine rotor system, a dynamic model of offshore wind turbine rotor system is proposed. The insulating coating, inclined shaft current damage and contact characteristics are considered in the model. Through numerical simulation, the mapping relationship between vibration response and damage length is studied, the influence of the interaction between inclination angle and radial clearance on vibration response is analyzed, and the influence of the mass of insulating coating and speed on vibration response is discussed. The practicability of the model is proved by the experiment of physical prototype. The results show that, as the length of the shaft current damage increases from 10 × 10−5 m to 50 × 10−5 m, the strength of the vibration response increases. The coupling of the inclination angle of the shaft current damage and the radial clearance jointly promotes the enhancement of the vibration response. The enhancement effect of radial clearance is more significant than that of inclination angle. The increase of speed worsens the state of operation, and the state transitions from stable quasi-period to chaos.

Numerical and experimental study of the preload induced period-1 and chaotic vibration of a rotor system considering contact effects

Contact effects are one of the primary nonlinear sources of vibrations in the gas turbine rotor systems. Specifically, the nonlinear stiffness between the disk interface from the contact effects has an important influence on the vibration characteristics. In this study, a contact model that accounts for the elastoplastic deformation of asperity is established based on the contact theory. To improve the macroscopic contact model of the bolted structure, we integrate the tested morphology results and modified the skewed distribution function. Subsequently, a dynamic model of the rod fastened rotor-bearing system that incorporates the nonlinear oil film force is established. The influence of the preload on the vibration characteristics of the rotor bearing system is analyzed. The results demonstrate that the improved contact model accurately describes the distribution of asperities on rough surface. The contact effects weaken the rotor lateral stiffness to a certain extent. According to the numerical results and experimental results, it can be found that changes in preload significantly affects the occurrence conditions from periodic vibration to chaotic vibration, a higher preload is conducive to maintaining the stable period-1 motion state at high speed. Additionally, as the preload is decreased, the speed range with obvious periodic-doubling frequencies gradually increases and the amplitude of vibration response decreases. This work provides a practical guidance for the dynamic design and preload adjustment of gas turbine rod-fastened rotor considering contact effects.

Multi-scale contact induced period-doubling vibrations in rotor systems: Numerical and experimental studies

Bolted disk structure has the advantages of easy production and assembly and it is widely adopted in the design of gas turbine rotors. However, the discontinuity of bolted structure and the contact effects between the disks produce complex nonlinear properties to the rotor system, resulting in difficulties in solving the vibration dynamics of the rotors. In this paper, in order to reflect the contact effect between the rotor disks more accurately, a multi-scale contact mechanics model considering the whole deformation process of the material is deduced based on the skewed distribution theory. The contact effect between disks is considered by introducing an equivalent material layer. Newmark-β method is applied to obtain the dynamic response of the rotor system under different preloads. A multi-disk rotor-bearing test bench is designed to conduct dynamic tests to verify the accuracy of the contact modeling method and obtained dynamic results. Numerical and experimental results show that adjusting the preloads has the effect to change the bifurcation state of the rotor system and the increase in the preloads leads to the period-doubling bifurcation phenomenon moving toward low speed, and leads to the early appearance of some combined frequency components (such as 2fn-fr, where fn is the working frequency and fr is the oil film whirl frequency). This research provides a theoretical reference for the modeling, dynamic behavior prediction as well as fault diagnosis of rod-fastened gas turbine rotor systems.

Effect of Unbalanced Magnetic Pull of Generator Rotor on the Dynamic Characteristics of a Pump—Turbine Rotor System

In pumped storage units, the rotor-bearing electromagnetic system is under the joint influence of hydraulics, mechanics, and electromagnetics, and the mechanism of unit vibration problems is very complex to investigate. ANSYS software is used to establish a three-dimensional model of a pumped storage power plant’s rotor-bearing electromagnetic system, and the stiffness coefficient of the unbalanced magnetic traction forces is calculated using the Fourier series of the magnetic conductivity of the air gap. This shows that the nonequilibrium magnetic attraction increases non-linearly with increasing excitation current and eccentricity of the rotor. At each order, the critical velocity of the rotor system increases as the stiffness factor of the bearing increases, with the greatest increase in critical velocity at the third and fourth orders. In the first-order mode-oscillation pattern, the unbalanced magnetic attraction has an effect on the intrinsic frequency of the transverse oscillation, with a reduction in the amplitude of the intrinsic frequency by 34.65%. Axial and transverse modal vibrations manifest themselves as upward and downward motions and transverse oscillations in different portions of the rotor system, respectively, whereas torsional modal vibrations manifest as a radial broadening or reduction in the generator rotor, runner, and coupling portions of the rotor system. The results of the study provide a theoretical foundation and a computational method for the dynamic analysis and design of the rotor system of pumped storage power stations.

Operation Security Prediction for Wind Turbines Using Convolutional Neural Networks: A Proposed Method

A wind turbine rotor system is a typical networked industrial control system. The security of its operation is very important to energy systems and users. In this article, the artificial intelligence algorithm is used to predict the security operation of a wind turbine rotor system, and a prediction method of system security monitoring based on a convolutional neural network (CNN) is proposed. First, the dynamic analysis of the operation principle of the wind turbine rotor system is carried out, and the industrial control model of the rotor system is established by using the relevant data of the wind turbine. The relevant data required for the security prediction of the wind turbine rotor system are obtained, and its dataset is established. Then, the CNN is trained with limited datasets, and the trained CNN is used to accurately predict the pitch angle. The residual information is obtained by comparing the predicted pitch angle with the real output pitch angle of the wind turbine rotor changing system. Finally, the security prediction results are obtained according to the residual and the decision index. The proposed security trend prediction method for wind turbine rotor systems can accurately and effectively predict the change of the fault amplitude, provide detection and estimate decision results, and improve the system security.

Vibration Simulation of the Turbine Rotor System of an Underwater Vehicle Considering the Bearing Radial Clearance

The turbine rotor system (TRS) is one important part of an underwater vehicle (UV). Its vibration and noise characteristics can greatly affect the performance and service life of the UV. To study the influence of radial clearance of supporting bearings on the vibrations of the whole TRS of the UV, a flexible dynamic model of the TRS is established by using the finite element and multi-body methods. Vibrations of the TRS from the rigid and flexible dynamic models under different bearing clearance conditions are analyzed. Note that the TRS with the flexible body model can obtain more accurate vibrations than the rigid one. The maximum vibration amplitude increases with the increment of bearing clearance. The bearing clearance of 5 micrometers to 20 micrometers is more reasonable for controlling the system vibration. The smaller clearance of supporting bearings of the TRS can cause more stable vibration responses. This paper can provide additional guidance for the accurate simulation analysis method of the TRSs of the UVs.

Stability analysis of the turbine rotor system with foundation support under impact excitation

Considering the stability changes of the whole steam turbine system with and without shock excitation, based on the combined methods of modeling simulation, multi-point analysis and multi-feature map analysis, the support structure of the whole steam turbine rotor under the action of unbalance and shock excitation is analyzed. Stability changes were analyzed. By analyzing the time-domain waveform, frequency spectrum and axis locus of the model casing, the typical support points of the high-pressure rotor section and the low-pressure rotor section under the sudden shock excitation and unbalanced force, the time-domain waveform, frequency spectrum and axis locus of the axis can be grasped. The influence on the structural stability and vibration characteristics of the steam turbine can provide a reference for the shock resistance design of the whole steam turbine system.

Nonlinear dynamic response on multi-fault rod fastening rotor with variable parameters

A multi-fault nonlinear model of rod fastening rotor is proposed considering the structural properties of rod fastening and the integration of multiple factors. The nonlinear analysis is performed to present the nonlinear characteristics of gas turbine rotor system with multi faults. The fault dynamics of rod fastening rotor is exposed for interaction and failure mechanism of multiple faults. The variable parameter analysis reveals the impact of system parameters variation on vibration response in multi-fault rod fastening rotor system. Analysis results reflect that multi faults enhances the nonlinearity of the system and makes dynamic characteristics more complicated. Complex nonlinear characteristics of the dynamical system are presented under different system parameters. The multi-fault nonlinear dynamic model and the nonlinear analysis of variable parameter contribute to the fault identification and stability research in the rod fastening rotor of gas turbine, which will provide the reference for the design and application of rod fastening rotor system.

Research on Improved Deep Convolutional Generative Adversarial Networks for Insufficient Samples of Gas Turbine Rotor System Fault Diagnosis

In gas turbine rotor systems, an intelligent data-driven fault diagnosis method is an important means to monitor the health status of the gas turbine, and it is necessary to obtain sufficient fault data to train the intelligent diagnosis model. In the actual operation of a gas turbine, the collected gas turbine fault data are limited, and the small and imbalanced fault samples seriously affect the accuracy of the fault diagnosis method. Focusing on the imbalance of gas turbine fault data, an Improved Deep Convolutional Generative Adversarial Network (Improved DCGAN) suitable for gas turbine signals is proposed here, and a structural optimization of the generator and a gradient penalty improvement in the loss function are introduced to generate effective fault data and improve the classification accuracy. The experimental results of the gas turbine test bench demonstrate that the proposed method can generate effective fault samples as a supplementary set of fault samples to balance the dataset, effectively improve the fault classification and diagnosis performance of gas turbine rotors in the case of small samples, and provide an effective method for gas turbine fault diagnosis.

Flexural vibration of multistep rotating Timoshenko shafts using hybrid modeling and optimization techniques

In this paper, the flexural vibration of uniform and non-uniform rotating shafts based on the Timoshenko beam theory is investigated. Considering shear deformation and gyroscopic effects to build an exact framework of a solution, the fourth-order differential equation of vibration is solved by an analytical method. The overall transfer matrix of the system formed by a series of flexible distributed in addition to lumped elements is achieved. The results obtained by the distributed lumped modeling technique (DLMT) are verified with other techniques. The damped frequencies obtained by the hybrid modeling method for a multistep gas turbine rotor system using the Euler–Bernoulli and Timoshenko beam theories are compared with the results of the transfer matrix method (TMM). It is shown that the presented method provides highly accurate results, while with no compromise, it can be simply and effectively employed for complex systems. It is also shown how the Hooke and Jeeves and the ant colony optimization (ACO) besides the direct enumeration method can be applied to obtain the damped natural frequencies of complicated vibrational systems such as the gas turbine rotors. The comparison between the frequency and damping ratio values obtained by the optimization and direct enumeration methods shows less than 1% error for different cases.

Dynamic analysis of composite rod fastening rotor system considering multiple parameter influence

Dynamic performances of composite rod fastening rotor system are analyzed considering the integration of multiple parameters. A dynamic modeling method of multi-disk rod fastening rotor system is proposed based on the composite rotor structure and the influences of multiple parameters. The interaction of system parameters and fault features are revealed in the composite rod fastening rotor system. The dynamic analysis discloses the influence of fault degree and multiple parameters on the nonlinear behaviors. The results show that the dynamic characteristics of the rod fastening rotor system alter under the crack fault. The evolution of nonlinear performances is displayed in the analysis of multiple parameters. The analysis results contribute to the identification of dynamic characteristics for rod fastening rotor system and fault detection of gas turbine rotor system.

Nonlinear analysis of a dual-disk rotor system considering elastoplastic contact

The contact effect of disk interfaces has an important influence on the dynamic response of the gas turbine rotor system. In order to improve the accuracy of the contact model, this paper proposes a modified contact model for the full deformation stage based on verified experimental results by considering the influence of elastoplastic deformation, the experimental results and the theoretical results of contact model are compared. In order to simplify the modeling process of the contact interface, the equivalent material layer was introduced to establish the finite element model of the dual-disk rotor-bearing system, and the dynamic response of the rotor system was solved by the Newmark-β method. The validation of the proposed contact model is verified by comparing the time-domain waveform diagram. The dynamic characteristics of the rotor system under different preloads and speeds are analyzed. Results demonstrate that the contact model proposed in this paper can reflect the actual contact state accurately, a certain amount of preload will cause the appearance of multiple combined frequency components, such as fr-2fn, 3fr-4fn (fr is rotating frequency, fn is oil film oscillation frequency). The work provides a theoretical reference for contact effect modeling of rotor system, and has prospective application in gas turbines.

Multi-objective optimization of a small scale SCO2 turbine rotor system with a shaft cooler

The SCO2 turbine machines exchange energy through supercritical carbon dioxide. Their impeller has the features of high-temperature and −speed to enhance energy conversion efficiency, but the rotor needs to be cooled to be compatible with bearings and seals. The paper introduces a pivotal parameter optimization of a concentrating solar SCO2 turbine rotor and seeks to control the harmonic response amplitude while preserving the distance between the critical speed and the working speed. The optimization considers several parameters including bearing span, stiffness, effective mass and damping of the bearing hub, and gas film stiffness coefficients of the cooler. The optimization is accomplished using a multi-objective and −scale quantum harmonic oscillator algorithm (mMQHOA) that couples an information interaction algorithm and transfer matrix model. The application of information interaction accelerates the convergence speed of the objective functions. The verification results from the three-dimensional finite element (3D-FE) indicate that the non-dominant design reduces resonance amplitude of the disc by approximately 71.91%, while the critical frequency increases by about 34.33% in the direction away from the operating frequency, and imply a trade-off relationship between harmonic response amplitude and critical speed. It is further reveal that the increased gas film stiffness of cooler in the primary level interval (<1E6 N/m) has no significant effect on the harmonic response of the system. The optimization is based not only on the analysis of design parameters, but also focuses on the sensitivity of objective functions that can significantly affect dynamic performance. The models with a single variable of bearing span and film stiffness are investigated respectively, and then the sensitivity of the system response is analyzed. In addition, three different objective functions are proposed, with the purpose of constructing a universally applicable model that can be further used to optimize the analogous bearing rotor system.

Experimental study of a winglet added small wind turbine with a flanged diffuser for domestic applications

Wind power is a reliable form of energy, and increasing the performance of wind turbines has helped to provide an ever-growing portion of the globe with cost-effective power in energy production. However, there are a few limits to the amount of energy that can be extracted using the wind turbine rotor system from an air stream (Wind). The research focuses on the characteristics of a bare and diffuser winglet horizontal axis wind turbine rotor. During the development of the rotor models, the following design parameters of rotor models such as twist, blade angle, chord length, tower height were taken into account. Experiments for rotor models with and without diffuser conditions were performed in the wind tunnel. For different wind speeds in the wind tunnel, rotation rates were measured for each rotor model. For all rotor models, the power coefficient (Cp ) and tip speed (Vc ) were calculated and reported. For the RW2 rotor with winglet and the corresponding power coefficient of 0.433 in the diffuser configuration, a maximum rotation rate of 2460 rpm was observed. The power coefficient for rotor models with winglet configuration (RW1) was increased by 10% and the power coefficient for rotor models with winglet configuration (RW3 & RW4) decreased by 18% in bare configuration as well as the power coefficient for rotor models increased by 4.9% in diffuser configuration.