Dynamic analysis of offshore wind turbines

Jianping Zhang,Mingqiang Wang,Zhen Gong,Fengfeng Shi 한국풍공학회 2020 Wind and Structures, An International Journal (WAS Vol.31 No.4

For large-scale 5MW offshore wind turbines, the discrete equation of fluid domain and the motion equation of structural domain with geometric nonlinearity were built, the three-dimensional modeling of the blade considering fluid-structure interaction (FSI) was achieved by using Unigraphics (UG) and Geometry modules, and the numerical simulation and the analysis of the vibration characteristics for wind turbine structure under rotating effect were carried out based on ANSYS software. The results indicate that the rotating effect has an apparent effect on displacement and Von Mises stress, and the response and the distribution of displacement and Von Mises stress for the blade in direction of wingspan increase nonlinearly with the equal increase of rotational speeds. Compared with the single blade model, the blade vibration period of the whole machine model is much longer. The structural coupling effect reduces the response peak value of the blade displacement and Von Mises stress, and the increase of rotational speed enhances this coupling effect. The maximum displacement difference between two models decreases first and then increases along wingspan direction, the trend is more visible with the equal increase of rotational speed, and the boundary point with zero displacement difference moves towards the blade root. Furthermore, the Von Mises stress difference increases gradually with the increase of rotational speed and decreases nonlinearly from the blade middle to both sides. The results can provide technical reference for the safe operation and optimal design of offshore wind turbines.

Study on the Mechanical Properties of Functional Graphene/Polyethylene Composites by Molecular Dynamics Simulation

Yuanyuan Qin,Yifei Wang,Jin Liu,Fengfeng Chen,Aiying Yao,Zhanchun Chen,Fu Junyu 한국고분자학회 2022 Macromolecular Research Vol.30 No.12

The mechanical properties of functionalized graphene/polyethylene (f- GRA/PE) composites and graphene/polyethylene (GRA/PE) composites were studied based on the crystallized models with the molecular dynamics simulation in this paper. The effects of GRA and f-GRA with different mass fractions on the mechanical properties of polyethylene were considered. The results showed that the adsorption capacity of polyethylene molecular chains of f-GRA is stronger, the compatibility of f-GRA/PE system is higher with decreasing the interface distance, and the dynamic property of molecular chain is weaker with reducing the radius of gyration of f-GRA/ PE. Furthermore, the reduction of mechanical energy consumption results in the increase of wear resistance of the system, which is more obvious when the mass fraction of f-GRA increases. Finally, the influence of different tensile rates on the composite system was studied. It was found that during the tensile process, the ability of the composite material to resist deformation in the stretching direction is enhanced, and the functionalized graphene inhibits the movement of the molecular chain due to the adsorption force, which improves the yield stress of the f-GRA/PE composite material, thereby increasing the tensile strength. Tensile rate has a certain effect on mechanical properties, and elastic modulus and yield stress increase with the increase of strain rate.

Analysis and research on dynamic characteristics of 3D braided composite two-stage reducer case

Weiliang Zhang,Xupeng Wang,Xiaomin Ji,Xinyao Tang,Fengfeng Liu,Shuwei Liu,Mingjun Liu,Xiao-Long Gao 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.6

Based on the analysis of the movement rule of 3D five-way braided yarn, the 3D five-way braided case model is divided into three parts: base, case bottom plate and case wall. According to the characteristics of each part, the braiding and forming principle of a 3D five-way composite case was analyzed. Under the assumption of ignoring the influence of friction, bearing and other factors on the system, the differential equations of motion of the two-stage gear transmission system with case were established. The two-stage gear transmission system was numerically analyzed by Euler method, and the influence of dimensionless meshing frequency, clearance, case mass and damping on the dynamic characteristics of the transmission system was studied. After that, high and low frequency disturbance was applied to the input case. The research shows that the damping ratio of the composite case increases and the low frequency attenuation is accelerated due to the decrease of the case mass, so the composite case has better shock resistance to low frequency interference.

The design and fabrication of 81.25 MHz RFQ for Low Energy Accelerator Facility

Bo Zhao,Shuping Chen,Tieming Zhu,Fengfeng Wang,Xiaofeng Jin,Chenxing Li,Wei Ma,Bin Zhang 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.2

To provide high shunt impendence with low power losses, an 81.25 MHz continuous wave (CW) radiofrequency quadrupole (RFQ) accelerator has been designed and machined as parts of the Low EnergyAccelerator Facility (LEAF). In this paper, the mechanical structure and the main processing technology ofthe RFQ cavities are described according to the physical and geometric parameters requirements of theRFQ. The fabrication of the RFQ has been completed and the test results agree well with the designrequirements. The RFQ accelerator will work in Institute of Modern Physics, Chinese Academy of Sciencesin 2018.

Influence of structure coupling effect on damping coefficient of offshore wind turbine blades

Jianping Zhang,Zhen Gong,Haolin Li,Mingqiang Wang,Zhiwei Zhang,Fengfeng Shi 한국풍공학회 2019 Wind and Structures, An International Journal (WAS Vol.29 No.6

The aim of this study was to explore the influence of structure coupling effect on structural damping of blade based on the blade vibration characteristic. For this purpose, the scaled blade model of NREL 5 MW offshore wind turbine was processed and employed in the wind tunnel test to validate the reliability of theoretical and numerical models. The attenuation curves of maximum displacement and the varying curves of equivalent damping coefficient of the blade under the rated condition were respectively compared and analyzed by constructing single blade model and whole machine model. The attenuation law of blade dynamic response was obtained and the structure coupling effect was proved to exert a significant influence on the equivalent damping coefficient. The results indicate that the attenuation trend of the maximum displacement response curve of the single blade varies more obviously with the increase of elastic modulus as compared to that under the structure coupling effect. In contrast to the single blade model, the varying curve of equivalent damping coefficient with the period is relatively steep for the whole machine model. The findings are of great significance to guide the structure design and material selection for wind turbine blades.

Design, fabrication and test of a taper-type half-wave superconducting cavity with the optimal beta of 0.15 at IMP

Yue Weiming,Zhang Shengxue,Li Chunlong,Jiang Tiancai,Liu Lubei,Wang Ruoxu,Huang Yulu,Tan Teng,Guo Hao,Zaplatin Evgeny,Xiong Pingran,Wu Andong,Wang Fengfeng,Zhang Shenghu,Huang Shichun,He Yuan,Yao Zeen 한국원자력학회 2020 Nuclear Engineering and Technology Vol.52 No.8

As a part of R&D work for the high intensity proton linac of China Accelerator Driven Sub-critical System project, a superconducting half-wave cavity with a frequency of 162.5 MHz and an optimal beta of 0.15 (HWR015) has been developed at Institute of Modern Physics (IMP), Chinese Academy of Sciences. In this paper, the design and test results will be described in detail. We introduced a new stiffening strategy for the HWR cavity, the simulation results show that the cavity has much lower frequency sensitivity coefficient (df/dp), Lorentz force detuning coefficient (KL), and can achieve more stable mechanical properties. The performance of the HWR cavity operated in cryostat will be also reported.

Low beta superconducting cavity system design for HIAF iLinac

Mengxin Xu,Yuan He,Shengxue Zhang,Lubei Liu,Tiancai Jiang,Zehua Liang,Tong Liu,Yue Tao,Chunlong Li,Qitong Huang,Fengfeng Wang,Hao Guo,Feng Bai,Xianbo Xu,Shichun Huang,Xiaoli Li,Zhijun Wang,Shenghu Zha Korean Nuclear Society 2023 Nuclear Engineering and Technology Vol.55 No.7

A superconducting ion-Linac (iLinac), which is supposed to work as the injector in the High Intensity heavy-ion Accelerator Facility project, is under development at the Institute of Modern Physics (IMP), Chinese Academy of Sciences. The iLinac is a superconducting heavy ion linear accelerator approximately 100 meters long and contains 96 superconducting cavities in two types of 17 cyromodules. Two types of superconducting resonators (quarter-wave resonators with a frequency of 81.25 MHz and an optimal beta β = v/c = 0.07 called QWR007 and half-wave resonators with a frequency of 162.5 MHz and an optimal beta β = 0.15 called HWR015) have been investigated. The cavity design included extensive multi-parameter electromagnetic simulations and mechanical analysis, and its results are described in details. The fundamental power coupler and cavity dynamic tuner designs are also presented in this article. The prototypes are under manufacturing and expected to be ready in 2023.

Numerical Study of Coherent Structures and Sound Radiation in a High Subsonic Jet

Feng Feng,Qiang Wang 한국전산유체공학회 2014 한국전산유체공학회 학술대회논문집 Vol.2014 No.10

The noise radiated by subsonic turbulent jet with a Mach number of 0.9 is investigated by the high-order accuracy parallel compressible LES (Large Eddy Simulation) method, and the far field sound is solved and analyzed by the permeable FW-H (Ffowcs Williams-Hawkings) wave extrapolation method. The jet mean flow and turbulence statistics is verified carefully to ensure the fidelity and accuracy of the simulation. Applying the frequency domain permeable FW-H method educe the predominant sound mode of the jet flow, and it is found that the coherent structures or the instability waves at the potential core end region form the low wave number wave packets lead to the predominant sound modes radiation.