Floating wind turbine technologies have worldwide applications. Regarding the wind turbine floater stability, there are three principal design philosophies: ballast-, buoyancy- and mooring-stabilized. Although linear hydrostatic stiffness coefficient has been applied in most hydro-aero-elastic codes, accurate calculation of the nonlinear hydrostatic restoring forces is important for the floating stability evaluation and load. This study selects a 5-megawatt spar floating wind turbine as a representative floater. The nonlinear hydrostatic stiffness coefficient for different heeling angles is analytically calculated and compared against those obtained by a hydrodynamic software, and an excellent match is shown. A sensitivity study is carried out to consider the uncertainties in the hydrostatic stiffness due to varying geometry and weight distribution. The present results can be applied in the time-domain simulations for floating wind turbines.
The physical model tests on anti-scouring of monopile foundation are carried out by two anti-scouring methods,the anti-scouring effect of different anti-scouring methods under sea conditions of an offshore wind farm is studied,and the cost analysis of different anti-scouring methods is conducted.The results show that:the concrete interlocking row protection is of stronger protection effect than riprap protection;the concrete interlocking row protection can adapt to soil deformation through flexible deformation and achieve the effect of effectively preventing sand and soil loss.Under comprehensive consideration,the riprap with concrete interlocking row protection is the most suitable protection method for the hydrological environment of this wind farm.
The running condition of the offshore wind turbine gearbox is judged by monitoring the oil debris of the gearbox.The most important debris parameters in the oil are monitored based on the inductance principle detection method according to different electromagnetic properties of ferromagnetic and non-ferromagnetic debris.The test bench is built,the iron and copper debris with radius of 200 μm,300 μm,500 μm,700 μm is tested,and the voltage changes caused by the iron and copper debris are found to be 57.5 mV and-23.0 mV,273.0 mV and-109.0 mV,1 175.0 mV and-470.0 mV,3 500.0 mV and-1 400.0 mV.It can be concluded that the oil debris detection method based on inductance principle is feasible,the voltage and polarity can be used to detect the size and electromagnetism of the debris,and the coil voltage change caused by the debris can be obtained.The negative voltage represents the detection of non-ferromagnetic debris,and the peak voltage is corresponding to the size of the detected debris.The positive voltage represents the detection of ferromagnetic debris,and the peak voltage value is corresponding to the size of the detected debris.The method does not need to stop the gearbox for inspection,reducing the economic loss caused by the shutdown,which is of engineering application value.
Based on the limit working state and cumulative damage theory of the structure,the safety evaluation standard for the increased load of the jacket platform is established.For the jacket platform,the mechanical model of the offshore platform under the joint action of the marine environment-rod pumping is established.Taken the LD jacket platform as an example,the extreme oceanic environmental load of 50 years is selected,and the loading threshold of the target platform is obtained based on the safety criterion.According to the design rated load of the rod pumping,the safety factor of the platform after loading is reduced by no more than 3％compared with that before loading,so that the jacket platform with similar structure is of sufficient structural strength to withstand the additional loads generated by the rod lifting process.
A dynamic analysis model of the polymer injection platform under the action of multiple polymer injection pumps is established with the Abaqus software,and the influence of the pump location,pump number and pump start instant on the vibration intensity of the platform is investigated in detail.A labyrinthine constrained damping isolation base is proposed according to the passive vibration isolation principle,and the performance of the damping base is numerically studied.The numerical results show that the vibration intensity of the platform increases linearly as the number of pumps increases,the vibration loads will cancel each other for the pumps start up at different instants,resulting in a significant reduction in the vibration intensity of the platform,the labyrinthine constrained damping isolation base can reduce the vibration intensity of the platform in multiple degrees of freedom significantly,and the isolation efficiency can reach 20％.
