Design And Optimization Of Carrier Platform For Half-Rotating Impeller Tidal Turbine

Tidal current energy is a kind of green renewable energy with large reserves and high energy density.Tidal current energy is mainly generated by turbine.The current velocity in most of the waters in China is low,so it has a good prospect for engineering application to design a kind of hydraulic machinery suitable for low velocity.Half-rotating Impeller Tidal Turbine(HRITT)was a new type of vertical axis turbine with lift drag combination,which had the advantages of excellent self starting performance and high energy harvesting efficiency.The design and optimization of the carrier platform of the HRITT were carried out to ensure the efficient and stable operation of the HRITT in the ocean.The main research contents and achievements of this paper were as follows.Firstly,the structure of Half-rotating mechanism(HRM)and HRITT was introduced,and the performance relationship between HRITT and carrier platform was explained.The rolling and pitching analysis model of HRITT was established in XFLOW.The data were processed to determine the allowable range of rolling and pitching angle of HRITT,so as to determine the performance requirements of HRITT on the carrier platform.Secondly,the carrier platform model of the HRITT was established,and two schemes were designed based on the floating barge platform — catamaran floating platform and six-side floating platform.Through the frequency domain analysis of the two schemes,the amplitude response operators of pitching and rolling were calculated and compared,and the scheme of the carrier platform of the HRITT was determined to be the catamaran floating platform.When the external excitation frequency was consistent with the natural frequency of the catamaran floating platform,the platform resonance occur,that was,the maximum motion response of the platform would be caused.Under the action of wave frequency(external excitation frequency),based on the frequency response method,the theoretical analysis model of the rolling and pitching of the catamaran floating platform was established,and the amplitude response operators of the rolling and pitching of the platform under different wave frequencies were obtained.ANSYS AQWA software was used to carry out numerical simulation of the catamaran floating platform,and the amplitude response operators of rolling and pitching under different wave frequencies were calculated.The numerical simulation results were compared with the theoretical analysis results to verify the credibility of the theoretical analysis,which provided a theoretical basis for the optimization of the main scale of the catamaran floating platform in the later stage.Thirdly,the main scale parameters of the catamaran floating platform were optimized to make the maximum value response operator of rolling and pitching within the allowable angle range of rolling and pitching of the HRITT.The optimized model was simulated to calculate the maximum amplitude response operators of rolling and pitching,and to verify whether the optimized catamaran floating platform could ensure the efficient and stable operation of the HRITT.The hydrodynamic performance of catamaran floating platform under the combined action of multiple loads was numerically simulated,and the wave force,added mass and motion response of the platform under three-level sea conditions were calculated.Finally,in order to improve the total power of the turbine,it was necessary to lay out several units.Therefore,the optimized platform modular plan—horizontal layout and circular arrangement,in the ANSYS AQWA two arrangement forms of catamaran floating platform were analyzed,and the calculation of two different layout of the rolling and pitching of the amplitude response of the operator,chose an appropriate layout,and the modular arrangement of platform and a single binary floating platform were analyzed.