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％.
A new heavy oil thermal recovery mode is proposed for an oilfield development project in Bohai Sea,to build a moveable steam injection platform,which is connected with the thermal recovery platform through bridge,and alternately provide qualified steam for multiple thermal recovery platforms.The steam pipeline will be stretched,compressed or twisted duo to relative movement of platforms caused by wind,wave,current and other factors.Therefore,compared with the conventional design of steam pipeline or bridge pipeline,the design difficulties of the bridge steam pipeline of the moveable steam injection platform are:high temperature and high pressure steam can not be connected by flexible hose,but only by steel pipe;large bridge displacement will cause large displacement stress and large sustained stress;alternating stress,which is produced by temperature change and displacement change duo to random wave movement,gradually accumulates,resulting in fatigue failure of the pipeline.Combined with ASME B31.3 and DNV specifications,and based on CAESAR Ⅱ stress analysis software,detailed static analysis and fatigue analysis of the steam pipeline are carried out.The above difficulties are solved,and the feasibility of transporting steam for thermal recovery platform through movable platform and bridge is demonstrated.
For the development of offshore solar energy resources,a lightweight single-layer frame floating photovoltaic supporting structure is proposed.In order to address the great challenges in the design of the floating offshore photovoltaic array mooring system brought by the environmental conditions of extremely shallow water with large tidal ranges,the time-domain coupled dynamic analysis is adopted to simulate the whole dynamic response of the floating photovoltaic array and mooring system and the influence of different mooring parameters on the motion response of the module array and the tension of the mooring lines are investigated considering the combined effects of the environmental loads such as wind,wave and current.The results indicate that the motion response and mooring line tension of the floating offshore photovoltaic module array can be effectively improved by reasonable selection of the mooring radius,buoy location,buoy net buoyancy and pre-tension.Based on this,the optimal design of the mooring system is carried out and the mooring system design meeting the engineering requirements is given.
The normal laying of Steel Catenary Riser(SCR)with a pipe-laying vessel in a gas field of the South China Sea is simulated with OrcaFlex so that the threshold environmental conditions for the safe operation of the riser are determined.The influence of wave direction,surface velocity,outer diameter and wall thickness of the riser on the operation window is investigated.Further,the applicability of the riser with different outer diameters and wall thicknesses under different water depths is analyzed to determine the limit laying water depth of the riser with S-lay.The results show that the installation window of the riser is sensitive to the wave direction,and it is safer to lay pipe under the following wave condition.With the increase of the surface velocity and the outer diameter and wall thickness of the riser,the height-period operation window decreases and the limit laying water depth decreases.
In order to solve the problem of deviation accumulation generated during the construction of floating body structures of semi-submersible platforms,Lingshui 17-2 Floating Production Unit(FPU)is taken as the research object.The construction accuracy data chain model of the floating body structure is built according to the deviation transmission relationship of the product accuracy control elements.According to the logical relationship between the related elements in the accuracy data chain,the data management system for the FPU floating structure construction accuracy course control is investigated,which can achieve the correlation and decoupling of data flow,data processing,data storage and data reuse among functions such as data collection,data analysis and problem handling,as well as the accuracy control mapping process corresponding to the actual production process.The system is extensible for other types of structures construction.
Aiming at the problems of unstable output power and low coupling efficiency of the offshore wind-wave complementary power generation system,a scheme of coupling wind and wave energy using differential gear mechanism is proposed.With the power generation of 20 kW as the design goal,the differential gear mechanism in the scheme is designed,and the dynamic equation of the differential gear mechanism is established.The sub-model of the differential gear mechanism is created by the secondary development platform of AMESim,and the simulation model of the wind-wave complementary power generation system is constructed.By optimizing and matching the model parameters,the stable power output of the coupled generation system is realized.The average generation power is 18.4 kW,the average power generation efficiency is 92％.Compared with the independent power generation of the two systems,the efficiency is increased by 7.5％,which provides a new set of solutions for efficient energy coupling of wind-wave complementary power generation system.
Based on the process analysis on the single point construction of the internal turret type Floating Production Storage and Offloading(FPSO),in the three-dimensional model of the structure,different module constructions are combined to establish scaffolding models for different construction stages,and the design parameters and difficulties of each scaffolding are analyzed.The analysis results can provide reference for scaffolding of the internal turret type single point construction,and also provide reference for the construction of similar projects.
The horizontal bearing characteristics of large diameter monopile in the radial sandbar of Jiangsu Province is studied.Based on the research method combining the field test and finite element numerical simulation,the numerical analysis of the horizontal ultimate bearing capacity of the monopile is carried out.The main conclusions are as follows:the deflection along the test pile tends to be zero near the pile toe,characterized as the flexible pile;with the increase of the horizontal load,the maximal bending moment of the test pile increases gradually,and its position gradually moves down,which is from 2.2D to 2.5D(D is the pile diameter)below the soil surface;the prediction model of the horizontal ultimate bearing capacity of the large diameter monopile is proposed,the predicted values of the horizontal ultimate bearing capacity of the monopiles based on the model are in good agreement with the numerical simulation results,the average relative error is only 4.9％,and the maximal relative error is less than 11％.
The key problems of the near-field interference,wave climb and air gap distribution of a semi-submersible platform are systematically studied by model test method.Under the guidance of the marine engineering hydrodynamic test regulations,the tank model test of the semi-submersible platform in the mooring mode is conducted.Through the deployment of the optical non-contact six degree-of-freedom sensor,resistance type tantalum wire,force sensor,wave height meter and other measuring equipment,the transient motion response of the platform,the wave run-up of the column wall and the air gap distribution in the internal field are obtained.The effects of different wave steepness parameters and scattering parameters on the air gap response characteristics of the platform are analyzed systematically.The results show that:the wave steepness is of great influence on the air gap distribution in the inner field,when the wave steepness parameter is from 0.12 to 0.15,the amplitude of the platform motion is large and the air gap at the platform edge is small;due to the wave climbing effect of the column,the air gap near the column is smaller than that in the inner field.The research conclusions can serve as a guidance for the design and safe operation of the platform.
The mechanical characteristics of the offshore wind turbine tower under combined loads are studied.Based on the data of 6 MW offshore wind turbine in Qidong sea area of Jiangsu Province,GH Bladed software is used to carry out the numerical simulations on the mechanical characteristics of the offshore wind turbine tower under combined loads.The main conclusions are as follows:the peak shear force on the bottom of the wind turbine tower under combined loads caused by the wind and wave increases by 72.0％and the peak bending moment by 8.3％compared with those under the wind load;the wave load is of a significant effect on both the shear force and bending moment on the bottom of the wind turbine tower,when the relative wave height is 4,the relative shear force and the relative bending moment on the bottom of the wind turbine tower are 3.04 and 1.44,respectively;the peak shear force on the bottom of the wind turbine tower under the combined loads caused by the wind and earthquake increases by 76％and the peak bending moment by 21％compared with those under the wind load.The research results can provide theoretical support for the design and construction of offshore wind turbines.
Aiming at the problems such as structural instability,fatigue failure and shortened service life of the submarine cable suspension section,based on the Vortex-Induced Vibration(VIV)mechanism of the submarine cable under the ocean current and combined with the structural characteristics of submarine cable,a vibration simulation model suitable for the submarine cable is established by the hydrodynamic method.Based on the simulation model,the effects of the current velocity,cable mechanical properties(cross section,quality,self damping characteristics,etc.),suspension section length on cable vibration and fatigue damage are studied.Combined the modified fatigue curve and rain flow count method,the fatigue damage of the submarine cable is calculated.According to the linear damage accumulation theory,the fatigue life of the submarine cable is gotten.The influence factors of the fatigue life of the submarine cable are analyzed.The results show that increasing the elastic modulus and damping ratio of the submarine cable and shortening the cable suspension section length can effectively extend the fatigue life of the submarine cable.
A collision accident between an offshore wind turbine jacket foundation and an engineering ship in the South China Sea is chosen as the research case.Based on the current damage assessment methods of the offshore wind turbine jacket structure,a series of researches,such as residual strength analysis and fatigue analysis,are conducted by the finite element simulation to give an insight view of the status of the impaired jacket structure.The stresses in each bar and node before and after damage to the jacket foundation,as well as the damage values of the damaged members under fatigue loading in compression and tension conditions,are obtained by calculation.In conjunction with the relevant industry standards,the calculation results are discussed and analyzed to comprehensively evaluate the damage situation of the jacket to provide basis for further repair engineering.The analysis outcomes will provide reference for subsequent research and practical engineering.
Based on the characteristics of the jackets in the potential removal market,a new type of general lifting clamp is designed for the removal of jackets.The clamp is prefabricated on land,does not need welding for offshore installation and can be reused.Using two options as examples,the feasibility of the clamp design is demonstrated and the range of the applicable jacket of the clamp is analyzed.The structural form of the newly designed clamp is proved to be practical,feasible,safe and reliable by software calculations,and the economy and operability of the clamp are analyzed.The results show that the clamp is of less installation workload,higher economy and stronger applicability.The new general lifting clamp is patented and will be widely used for jacket removal.
分析由3艘船[原油转驳船(Crude Transfer Vessel,CTV)、常规油船和拖船)]组成的多浮体原油转驳系统在卸载作业过程中的稳定性.根据船舶定位和拖曳模式,考虑多浮体系统所受的复杂环境载荷(包括风载荷、海流载荷和波浪载荷),研究原油卸载过程中多浮体系统在不同环境条件下保持准静态平衡的可能位置,得出保持准静态平衡时CTV推进器所需的最小推进力.结果表明,对于特定的风、流和波浪载荷方向,3艘船之间的夹角必须位于一定的范围内才能保持多浮体系统的平衡.
简要介绍水下生产系统用飞线国内外发展现状,分析飞线的类型、功能构造及常见的安装方法.在此基础上,针对南海1 500 m水深油气开发项目的不同类型飞线,进行安装方法概述,包括主要安装设备、安装步骤及关键安装技术要点分析.研究结果可为我国未来油气开发或其他水下工程飞线安装施工提供借鉴.
将水下探测声呐应用于半潜式采油平台对非法入侵的水下蛙人、潜行器和水下外来人员等目标进行实时探测预警,必要时采用防卫机制人工将目标驱离限定水域.从声呐图像预处理、运动目标检测和轨迹跟踪等3个方面详细设计水下声呐探测方案,并对探测方案进行应用试验.结果表明该方案可有效检测目标并进行轨迹跟踪,验证了水下探测声呐应用于半潜式平台水下安防系统中的有效性.
