Preliminary design of offshore wind turbines requires high precision simplified methods for the analysis of the system fundamental frequency. Based on the Rayleigh method and Lagrange’s Equation, this study establish...Preliminary design of offshore wind turbines requires high precision simplified methods for the analysis of the system fundamental frequency. Based on the Rayleigh method and Lagrange’s Equation, this study establishes a simple formula for the analysis of system fundamental frequency in the preliminary design of an offshore wind turbine with a monopile foundation. This method takes into consideration the variation of cross-section geometry of the wind turbine tower along its length, with the inertia moment and distributed mass both changing with diameter. Also the rotational flexibility of the monopile foundation is mainly considered. The rigid pile and elastic middle long pile are calculated separately. The method is validated against both FEM analysis cases and field measurements, showing good agreement. The method is then used in a parametric study, showing that the tower length Lt, tower base diameter d0, tower wall thickness δt, pile diameter db and pile length Lb are the major factors influencing the fundamental frequency of the offshore wind turbine system. In the design of offshore wind turbine systems, these five parameters should be adjusted comprehensively. The seabed soil condition also needs to be carefully considered for soft clay and loose sand.展开更多
A new concept, namely, the equivalent mobility matrix of coupling subsystem is proposed, and the corresponding threesubsystem coupling progressive approach is explored. With the new efficient approach presented, the c...A new concept, namely, the equivalent mobility matrix of coupling subsystem is proposed, and the corresponding threesubsystem coupling progressive approach is explored. With the new efficient approach presented, the complexity in dealing with a more complicated dynamic coupling system is greatly reduced. The new modeling method is then combined with the theory of power flow to investigate the dynamics of the overall non rigid isolation system from the viewpoint of energy. The interaction between the resilient machine of its main modes and the resonant behavior of the flexible foundation on power flow transmission is studied. Taking a machine tool mounted on a multi story working plant as an example, the dynamic characteristics of the machine foundation coupling system are analyzed, and their effects on power flow transmission are revealed under various service frequency bands. Some advisable control strategies and the design principle for machinery mounted on flexible structure are proposed.展开更多
In this paper we present the effect of vibration source on the power flow transmission in a compound flexible system. Considering the internal impedance of the source, a general model is here proposed, and the general...In this paper we present the effect of vibration source on the power flow transmission in a compound flexible system. Considering the internal impedance of the source, a general model is here proposed, and the generalized transfer equations of the system and the closed form solutions for power flow in the fiexible system are then developed, with which the effects of the source characteristics on power flow transmission are discussed. The investigation shows that when the source and receiver impedances are comparable, substantial error can occur in the power flow estimation if the source is assumed to be an ideal constant force source (CFS)or a constant velocity source (CVS).展开更多
基金National Natural Science Foundation of China under Grant Nos.51678346 and 51038007the State Key Laboratory of Hydroscience and Engineering Project under Grant Nos.2014-KY-03 and 2015-KY-03
文摘Preliminary design of offshore wind turbines requires high precision simplified methods for the analysis of the system fundamental frequency. Based on the Rayleigh method and Lagrange’s Equation, this study establishes a simple formula for the analysis of system fundamental frequency in the preliminary design of an offshore wind turbine with a monopile foundation. This method takes into consideration the variation of cross-section geometry of the wind turbine tower along its length, with the inertia moment and distributed mass both changing with diameter. Also the rotational flexibility of the monopile foundation is mainly considered. The rigid pile and elastic middle long pile are calculated separately. The method is validated against both FEM analysis cases and field measurements, showing good agreement. The method is then used in a parametric study, showing that the tower length Lt, tower base diameter d0, tower wall thickness δt, pile diameter db and pile length Lb are the major factors influencing the fundamental frequency of the offshore wind turbine system. In the design of offshore wind turbine systems, these five parameters should be adjusted comprehensively. The seabed soil condition also needs to be carefully considered for soft clay and loose sand.
文摘A new concept, namely, the equivalent mobility matrix of coupling subsystem is proposed, and the corresponding threesubsystem coupling progressive approach is explored. With the new efficient approach presented, the complexity in dealing with a more complicated dynamic coupling system is greatly reduced. The new modeling method is then combined with the theory of power flow to investigate the dynamics of the overall non rigid isolation system from the viewpoint of energy. The interaction between the resilient machine of its main modes and the resonant behavior of the flexible foundation on power flow transmission is studied. Taking a machine tool mounted on a multi story working plant as an example, the dynamic characteristics of the machine foundation coupling system are analyzed, and their effects on power flow transmission are revealed under various service frequency bands. Some advisable control strategies and the design principle for machinery mounted on flexible structure are proposed.
文摘In this paper we present the effect of vibration source on the power flow transmission in a compound flexible system. Considering the internal impedance of the source, a general model is here proposed, and the generalized transfer equations of the system and the closed form solutions for power flow in the fiexible system are then developed, with which the effects of the source characteristics on power flow transmission are discussed. The investigation shows that when the source and receiver impedances are comparable, substantial error can occur in the power flow estimation if the source is assumed to be an ideal constant force source (CFS)or a constant velocity source (CVS).
