Zhao Yongsheng

Research and practice of offshore wind turbine model test platform and technology

The abundance of offshore wind energy resources has promoted the development of offshore wind turbine. With the increase of wind turbine power, the fixed foundation for shallow sea area no longer meets the design requirements, and the floating foundation for deep sea area has been developed rapidly. In this paper, the development process, types and particularity are introduced, and it demonstrates that the model experiment is indispensable in the development of floating offshore wind turbine (FOWT). Firstly, key technologies of basin model test are concluded, such as similarity criteria, scale ratio determination technology, model blade design technology, mooring system processing technology and environmental conditions simulation technology. Then object of 6 MW SPAR-type FOWT proposed by Shanghai JiaoTong University is researched, and production process of model is summarized, including model blade, model nacelle and model tower. Finally, the construction of the deep water test tank of marine engineering of Shanghai JiaoTong University is introduced, and the test results of the new multi-column TLP FOWT model test in the test tank are shown. The test results have great agreement with software simulation results. The results show that the deep water test tank of marine engineering of Shanghai JiaoTong University can be well developed as basin model test of FOWT. This paper supplies some guidance for the following model test and provides a theoretical basis for the development of the FOWT.

Numerical simulation of tower shadow effectof upwind horizontal axis wind turbine

The tower-blade interaction is one of key reasons that would seriously affect the wind turbine aerodynamic performance. Simulation of tower shadow effect for a three-bladed, upwind offshore wind turbine using STAR-CCM+ software is researched. The model of national renewable energy laboratory (NREL) 5 MW baseline wind turbine is used in this simulation by computational fluid dynamics (CFD) method. Based on the reynolds averaged navier-stokes (RANS) equations and the shear-stress transport (SST) k - ω turbulence model, aerodynamic simulations for NREL 5 MW turbine have been studied. Model validation and grid-independence verification are conducted in order to have more accurate results. The aerodynamic simulations of wind turbine model with tower and rotor model without tower are carried out separately. The impacts of tower shadow effect on aerodynamic performance are obtained by comparison of two models. The method of blade element momentum (BEM) is also used to study tower shadow effect, and two research methods are compared. Simulation results demonstrate that the tower shadow effect is remarkable. Mutation caused by tower shadow effect of aerodynamic performance is emerged and it will cause some adverse results for blades and tower. Impact of tower shadow effect on average value of wind turbine aerodynamic load is not significant. As is shown by simulation results, average thrust of wind turbine is declined by 0.46% and average power is declined by 0.87%. This paper could also provide some references for further research about the influence of tower shadow effect on aerodynamic performance.

Experimental study of a new multi-columntension leg-type floating wind turbine concept

Offshore deep-water region is rich in high-quality wind energy. Currently offshore floating wind turbine is the most potential equipment to exploit it. The relevant scaling laws need to be considered during the offshore floating wind turbine model test were analysed and a proper scaling methodology was established according to the loading conditions. The wave tank model test was conducted for the proposed new multi-column tension leg-type floating wind turbine concept in SKLOE’s wave basin with the geometric scaling factor of 50 according to the main dimensions and environmental conditions. By using a modified blade design based on the same wind turbine thrust coefficient, the aerodynamic Reynolds number scaling effect was dissimilated during the model test. Still water tests, white noise wave tests and combined wind wave and current tests were carried out. During the combined wind, wave and current tests, both the turbine operating (DLC01-05) and parked conditions (DLC06, DLC07) were investigated. To identify the dominate load of the dynamic responses, each design load case was further separated into four different sub-load cases: wind only case, wave only case, current only case and combined load case. Global response variables including platform motion, tendon tension, rotor thrust, and nacelle accelerations were examined. In summary, the proposed WindStar TLP system showed relatively small dynamic motion responses to environmental loads due to its natural frequencies are well kept away from the dominant wave periods and the tendons still holds a sufficient safety factor, and the minimum tendon tensions remain positive under all the selected DLCs. The model testing results could serve as a reference for the further research.