The topic of offshore wind energy is attracting more and more attention as the energy crisis heightens.The blades are the key components of offshore wind turbines,and their dynamic characteristics directly determine t...The topic of offshore wind energy is attracting more and more attention as the energy crisis heightens.The blades are the key components of offshore wind turbines,and their dynamic characteristics directly determine the effectiveness of offshore wind turbines.With different rotating speeds and blade length,the rotating blades generate various centrifugal stiffening effects.To directly analyze the centrifugal stiffening effect of blades,the Rayleigh energy method (REM) was used to derive the natural frequency equation of the blade,including the centrifugal stiffening effect and the axial force calculation formula.The axial force planes and the first to third order natural frequency planes which vary with the rotating speed and length were calculated in three-dimensional coordinates.The centrifugal stiffening coefficient was introduced to quantitatively study the relationship between the centrifugal stiffening degree and the rotating speed,and then the fundamental frequency correction formula was built based on the rotating speed and the blade length.The analysis results show that the calculation results of the fundamental frequency correction formula agree with the theoretical calculation results.The error of calculation results between them is less than 0.5%.展开更多
The stability control of surrounding rock for large or super-large section chamber is a difficult technical problem in deep mining condition.Based on the in-site geological conditions of Longgu coal mine,this paper us...The stability control of surrounding rock for large or super-large section chamber is a difficult technical problem in deep mining condition.Based on the in-site geological conditions of Longgu coal mine,this paper used the dynamic module of FLAC3D to study the response characteristics of deep super-large section chamber under dynamic and static combined loading condition.Results showed that under the static loading condition,the maximum vertical stress,deformation and failure range are large,where the stress concentration coefficient is 1.64.The maximum roof-to-floor and two-sides deformations are 54.6 mm and 53.1 mm,respectively.Then,under the dynamic and static combined loading condition:(1)The influence of dynamic load frequency on the two-sides is more obvious;(2)The dynamic load amplitude has the greatest influence on the stress concentration degree,and the plastic failure tends to develop to the deeper;(3)With the dynamic load source distance increase,the response of surrounding rock is gradually attenuated.On this basis,empirical equations for each dynamic load conditions were obtained by using regression analysis method,and all correlation coefficients are greater than 0.99.This research provided reference for the supporting design of deep super-large section chamber under same or similar conditions.展开更多
The paper is devoted to mathematical modelling of static and dynamic stability of a simply supported three-layered beam with a metal foam core. Mechanical properties of the core vary along the vertical direction. The ...The paper is devoted to mathematical modelling of static and dynamic stability of a simply supported three-layered beam with a metal foam core. Mechanical properties of the core vary along the vertical direction. The field of displacements is for- mulated using the classical broken line hypothesis and the proposed nonlinear hypothesis that generalizes the classical one. Using both hypotheses, the strains are determined as well as the stresses of each layer. The kinetic energy, the elastic strain energy, and the work of load are also determined. The system of equations of motion is derived using Hamilton＇s principle. Finally, the system of three equations is reduced to one equation of motion, in particular, the Mathieu equation. The Bubnov-Galerkin method is used to solve the system of equations of motion, and the Runge-Kutta method is used to solve the second-order differential equation. Numerical calculations are done for the chosen family of beams. The critical loads, unstable regions, angular frequencies of the beam, and the static and dynamic equilibrium paths are calculated analytically and verified numerically. The results of this study are presented in the forms of figures and tables.展开更多
In order to control the low frequency vibration of railway vehicles, a vertical two degrees of freedom(2DOF) low frequency dynamic vibration absorber(DVA) based on acceleration is proposed. Parameters of the dynamic v...In order to control the low frequency vibration of railway vehicles, a vertical two degrees of freedom(2DOF) low frequency dynamic vibration absorber(DVA) based on acceleration is proposed. Parameters of the dynamic vibration absorber are put forth to control the low frequency vibration of car body bouncing and pitching. Next, the acceleration power spectrum density(PSD)and ride quality of the car body are calculated based on the pseudo excitation method(PEM) and covariance algorithm,respectively. According to the requirement of 2DOF low frequency DVA, the isolators with high static low dynamic stiffness(HSLDS) are designed. A high-speed train dynamic model containing HSLDS isolators is established to validate the effects on the car body vibration. The results reveal that the 2D low frequency DVA can significantly reduce the vibration of the car body bouncing and pitching. Thus, the ride quality of the vehicle is increased, and passenger comfort is improved.展开更多
为解决风机叶片故障诊断的音频信号特征有效提取问题,文章提出了一种融合梅尔频率倒谱系数(Mel-frequency cepstral coefficients,MFCC)和本征能量比(intrinsic energy ratio,IER)的故障诊断方法。其首先分别提取了风机叶片音频信号的M...为解决风机叶片故障诊断的音频信号特征有效提取问题,文章提出了一种融合梅尔频率倒谱系数(Mel-frequency cepstral coefficients,MFCC)和本征能量比(intrinsic energy ratio,IER)的故障诊断方法。其首先分别提取了风机叶片音频信号的MFCC和IER特征,并采用动态时间规整实现故障特征降维,形成复合MFCC特征;然后,对由叶片声脉冲提取的复合MFCC特征进行去噪并采用支持向量机实现对风机叶片故障的分类。实验结果表明,采用基于MFCC与IER的特征提取方法,可实现风机叶片故障识别性能,其正确率达到97.06%,对于风机稳定运行与维护具有重要意义。展开更多
Dynamic instability of decentralized wind energy farms is a major issue to deliver continuous green energy to electricity consumers.This instability is caused by variations of voltage and frequency parameters due to i...Dynamic instability of decentralized wind energy farms is a major issue to deliver continuous green energy to electricity consumers.This instability is caused by variations of voltage and frequency parameters due to intermittencies in wind power.Previously,droop control and inverter-based schemes have been proposed to regulate the voltage by balancing reactive power,while inertial control,digital mapping tech-nique of proportional-integral-differential(PID)controller and efficiency control strategy have been developed to regulate the frequency.In this paper,voltage stability is improved by a new joint strategy of distribution static compensator(DSTATCOM)six-pulse controller based reactive power management among decentralized wind turbines and controlled charging of capacitor bank.The frequency stability is ensured by a joint coordinated utilization of capacitor bank and distributed wind power turbines dispatching through a new DSTATCOM six-pulse controller scheme.In both strategies,power grid is contributed as a backup source with less priority.These new joint strategies for voltage and frequency stabilities will enhance the stable active power delivery to end users.A system test case is developed to verify the proposed joint strategies.The test results of the proposed new schemes are proved to be effective in terms of stability improvement of voltage,frequency and active power generation.展开更多
针对现有850 k W风力机叶片,分析其材料、结构及铺层状态,对比传统叶片有限元模型,将描述叶片主要结构的弦长、扭角采用分段函数形式表达,采用MATLAB编程并结合ANSYS二次开发建立风力机叶片参数化几何模型.基于动量-叶素理论的BLADED软...针对现有850 k W风力机叶片,分析其材料、结构及铺层状态,对比传统叶片有限元模型,将描述叶片主要结构的弦长、扭角采用分段函数形式表达,采用MATLAB编程并结合ANSYS二次开发建立风力机叶片参数化几何模型.基于动量-叶素理论的BLADED软件计算叶片各截面处的极限载荷,并于叶片分段施加载荷增量.动力学分析得到叶片前三阶挥舞和摆振频率及一阶扭转频率,其与实测固有频率比较,分析并验证叶片于共振区外运行.静力分析得到叶片挥舞位移及关键部位应力分布,通过最大应力准则和蔡-胡(Tsai-Wu)准则对翼面进行强度校核(其他部位同理校核),表明叶片在极限状态下仍能保持安全运行.该研究描绘了叶片主要力学性能,为叶片进一步优化奠定了基础.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No.50708015the foundation of State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology
文摘The topic of offshore wind energy is attracting more and more attention as the energy crisis heightens.The blades are the key components of offshore wind turbines,and their dynamic characteristics directly determine the effectiveness of offshore wind turbines.With different rotating speeds and blade length,the rotating blades generate various centrifugal stiffening effects.To directly analyze the centrifugal stiffening effect of blades,the Rayleigh energy method (REM) was used to derive the natural frequency equation of the blade,including the centrifugal stiffening effect and the axial force calculation formula.The axial force planes and the first to third order natural frequency planes which vary with the rotating speed and length were calculated in three-dimensional coordinates.The centrifugal stiffening coefficient was introduced to quantitatively study the relationship between the centrifugal stiffening degree and the rotating speed,and then the fundamental frequency correction formula was built based on the rotating speed and the blade length.The analysis results show that the calculation results of the fundamental frequency correction formula agree with the theoretical calculation results.The error of calculation results between them is less than 0.5%.
基金Project(2018YFC0604703)supported by the National Key R&D Program of ChinaProjects(51804181,51874190)supported by the National Natural Science Foundation of China+3 种基金Project(ZR2018QEE002)supported by the Shandong Province Natural Science Fund,ChinaProject(ZR2018ZA0603)supported by the Major Program of Shandong Province Natural Science Foundation,ChinaProject(2019GSF116003)supported by the Key R&D Project of Shandong Province,ChinaProject(SDKDYC190234)supported by the Shandong University of Science and Technology,Graduate Student Technology Innovation Project,China。
文摘The stability control of surrounding rock for large or super-large section chamber is a difficult technical problem in deep mining condition.Based on the in-site geological conditions of Longgu coal mine,this paper used the dynamic module of FLAC3D to study the response characteristics of deep super-large section chamber under dynamic and static combined loading condition.Results showed that under the static loading condition,the maximum vertical stress,deformation and failure range are large,where the stress concentration coefficient is 1.64.The maximum roof-to-floor and two-sides deformations are 54.6 mm and 53.1 mm,respectively.Then,under the dynamic and static combined loading condition:(1)The influence of dynamic load frequency on the two-sides is more obvious;(2)The dynamic load amplitude has the greatest influence on the stress concentration degree,and the plastic failure tends to develop to the deeper;(3)With the dynamic load source distance increase,the response of surrounding rock is gradually attenuated.On this basis,empirical equations for each dynamic load conditions were obtained by using regression analysis method,and all correlation coefficients are greater than 0.99.This research provided reference for the supporting design of deep super-large section chamber under same or similar conditions.
基金Project supported by the Ministry of Science and Higher Education of Poland(Nos.04/43/DSPB/0085and 02/21/DSPB/3464)
文摘The paper is devoted to mathematical modelling of static and dynamic stability of a simply supported three-layered beam with a metal foam core. Mechanical properties of the core vary along the vertical direction. The field of displacements is for- mulated using the classical broken line hypothesis and the proposed nonlinear hypothesis that generalizes the classical one. Using both hypotheses, the strains are determined as well as the stresses of each layer. The kinetic energy, the elastic strain energy, and the work of load are also determined. The system of equations of motion is derived using Hamilton＇s principle. Finally, the system of three equations is reduced to one equation of motion, in particular, the Mathieu equation. The Bubnov-Galerkin method is used to solve the system of equations of motion, and the Runge-Kutta method is used to solve the second-order differential equation. Numerical calculations are done for the chosen family of beams. The critical loads, unstable regions, angular frequencies of the beam, and the static and dynamic equilibrium paths are calculated analytically and verified numerically. The results of this study are presented in the forms of figures and tables.
基金supported by the National Natural Science Foundation of China(Grant No.51805373)
文摘In order to control the low frequency vibration of railway vehicles, a vertical two degrees of freedom(2DOF) low frequency dynamic vibration absorber(DVA) based on acceleration is proposed. Parameters of the dynamic vibration absorber are put forth to control the low frequency vibration of car body bouncing and pitching. Next, the acceleration power spectrum density(PSD)and ride quality of the car body are calculated based on the pseudo excitation method(PEM) and covariance algorithm,respectively. According to the requirement of 2DOF low frequency DVA, the isolators with high static low dynamic stiffness(HSLDS) are designed. A high-speed train dynamic model containing HSLDS isolators is established to validate the effects on the car body vibration. The results reveal that the 2D low frequency DVA can significantly reduce the vibration of the car body bouncing and pitching. Thus, the ride quality of the vehicle is increased, and passenger comfort is improved.
文摘为解决风机叶片故障诊断的音频信号特征有效提取问题,文章提出了一种融合梅尔频率倒谱系数(Mel-frequency cepstral coefficients,MFCC)和本征能量比(intrinsic energy ratio,IER)的故障诊断方法。其首先分别提取了风机叶片音频信号的MFCC和IER特征,并采用动态时间规整实现故障特征降维,形成复合MFCC特征;然后,对由叶片声脉冲提取的复合MFCC特征进行去噪并采用支持向量机实现对风机叶片故障的分类。实验结果表明,采用基于MFCC与IER的特征提取方法,可实现风机叶片故障识别性能,其正确率达到97.06%,对于风机稳定运行与维护具有重要意义。
文摘Dynamic instability of decentralized wind energy farms is a major issue to deliver continuous green energy to electricity consumers.This instability is caused by variations of voltage and frequency parameters due to intermittencies in wind power.Previously,droop control and inverter-based schemes have been proposed to regulate the voltage by balancing reactive power,while inertial control,digital mapping tech-nique of proportional-integral-differential(PID)controller and efficiency control strategy have been developed to regulate the frequency.In this paper,voltage stability is improved by a new joint strategy of distribution static compensator(DSTATCOM)six-pulse controller based reactive power management among decentralized wind turbines and controlled charging of capacitor bank.The frequency stability is ensured by a joint coordinated utilization of capacitor bank and distributed wind power turbines dispatching through a new DSTATCOM six-pulse controller scheme.In both strategies,power grid is contributed as a backup source with less priority.These new joint strategies for voltage and frequency stabilities will enhance the stable active power delivery to end users.A system test case is developed to verify the proposed joint strategies.The test results of the proposed new schemes are proved to be effective in terms of stability improvement of voltage,frequency and active power generation.
文摘针对现有850 k W风力机叶片,分析其材料、结构及铺层状态,对比传统叶片有限元模型,将描述叶片主要结构的弦长、扭角采用分段函数形式表达,采用MATLAB编程并结合ANSYS二次开发建立风力机叶片参数化几何模型.基于动量-叶素理论的BLADED软件计算叶片各截面处的极限载荷,并于叶片分段施加载荷增量.动力学分析得到叶片前三阶挥舞和摆振频率及一阶扭转频率,其与实测固有频率比较,分析并验证叶片于共振区外运行.静力分析得到叶片挥舞位移及关键部位应力分布,通过最大应力准则和蔡-胡(Tsai-Wu)准则对翼面进行强度校核(其他部位同理校核),表明叶片在极限状态下仍能保持安全运行.该研究描绘了叶片主要力学性能,为叶片进一步优化奠定了基础.
