Based on the electric pitch system of large scale horizontal-axis wind turbines,the blade pitch loads coming mainly from centrifugal force,aerodynamic force and gravity are analyzed,and the calculation models for them...Based on the electric pitch system of large scale horizontal-axis wind turbines,the blade pitch loads coming mainly from centrifugal force,aerodynamic force and gravity are analyzed,and the calculation models for them are established in this paper.For illustration,a 1.2 MW wind turbine is introduced as a practical sample,and its blade pitch loads from centrifugal force,aerodynamic force and gravity are calculated and analyzed separately and synthetically.The research results showed that in the process of rotor rotating 360o,the fluctuation of blade pitch loads is similar to cosine curve when the rotor rotational speed,in-flow wind speed and pitch angle are constant.Furthermore,the amplitude of blade pitch load presents quite a difference at a different pitch angle.The ways of calculation for blade pitch loads are of the universality,and are helpful for further research of the individual pitch control system.展开更多
The hydrodynamic characteristics of free variable-pitch vertical axis tidal turbine are investigated by combining experimental and numerical simulations. The variations of hydrodynamics are obtained based on testing t...The hydrodynamic characteristics of free variable-pitch vertical axis tidal turbine are investigated by combining experimental and numerical simulations. The variations of hydrodynamics are obtained based on testing the kinematics and the dynamics of the turbine under different flow and structural conditions. Through analyzing the movement of the turbine and the characteristics of the flow field by numerical simulations, it is shown how the turbine＇s performance is improved.展开更多
There remains a need to develop improved VTOL techniques that are cost-effective and with minimum compromise on cruising flight performance for fixed-wing aircraft. This work proposes an elegant VTOL control method kn...There remains a need to develop improved VTOL techniques that are cost-effective and with minimum compromise on cruising flight performance for fixed-wing aircraft. This work proposes an elegant VTOL control method known as PTVC-M (pitch-axis thrust vector control with moment arms) for tailsitters. The hallmark of the approach is the complete elimination of control surfaces such as elevators and rudder. Computer simulations with a 1580 mm wing span airplane reveal that the proposed technique results in authoritative control and unique maneuverability such as inverted vertical hover and stall-spin with positive climb rate. Zero-surface requirement of the PTVC-M virtually eliminates performance tradeoffs between VTOL and high-speed flight. In this proof-of-concept study, the VTOL-capable aircraft achieves a VH of 360 km·h<sup>-1</sup> at near sea-level. The proposed technique will benefit a broad range of applications including high-performance spinsonde that can directly measure 10-m surface wind, tropical cyclone research, and possibly serving as the cornerstone for the next-generation sport aerobatics.展开更多
基金supported by the National Natural Science Foundation of China (Grant No.50975086)the National High Technology Research and Development Program of China ("863" Program) (Grant No.2006AA05Z401)
文摘Based on the electric pitch system of large scale horizontal-axis wind turbines,the blade pitch loads coming mainly from centrifugal force,aerodynamic force and gravity are analyzed,and the calculation models for them are established in this paper.For illustration,a 1.2 MW wind turbine is introduced as a practical sample,and its blade pitch loads from centrifugal force,aerodynamic force and gravity are calculated and analyzed separately and synthetically.The research results showed that in the process of rotor rotating 360o,the fluctuation of blade pitch loads is similar to cosine curve when the rotor rotational speed,in-flow wind speed and pitch angle are constant.Furthermore,the amplitude of blade pitch load presents quite a difference at a different pitch angle.The ways of calculation for blade pitch loads are of the universality,and are helpful for further research of the individual pitch control system.
基金Project supported by the National Natural Science Foundation of China(Grant No.51106034)the Marine Renewable Energy Special Foundation(Grant No.ZJME2010CY01)
文摘The hydrodynamic characteristics of free variable-pitch vertical axis tidal turbine are investigated by combining experimental and numerical simulations. The variations of hydrodynamics are obtained based on testing the kinematics and the dynamics of the turbine under different flow and structural conditions. Through analyzing the movement of the turbine and the characteristics of the flow field by numerical simulations, it is shown how the turbine＇s performance is improved.
文摘There remains a need to develop improved VTOL techniques that are cost-effective and with minimum compromise on cruising flight performance for fixed-wing aircraft. This work proposes an elegant VTOL control method known as PTVC-M (pitch-axis thrust vector control with moment arms) for tailsitters. The hallmark of the approach is the complete elimination of control surfaces such as elevators and rudder. Computer simulations with a 1580 mm wing span airplane reveal that the proposed technique results in authoritative control and unique maneuverability such as inverted vertical hover and stall-spin with positive climb rate. Zero-surface requirement of the PTVC-M virtually eliminates performance tradeoffs between VTOL and high-speed flight. In this proof-of-concept study, the VTOL-capable aircraft achieves a VH of 360 km·h<sup>-1</sup> at near sea-level. The proposed technique will benefit a broad range of applications including high-performance spinsonde that can directly measure 10-m surface wind, tropical cyclone research, and possibly serving as the cornerstone for the next-generation sport aerobatics.
