A rotary valve-controlled pitch system is proposed to regulate the generator power and smooth power fluctuationsfor a wind turbine. Design details and dynamic modeling of this pitch system are presented and analyzed. ...A rotary valve-controlled pitch system is proposed to regulate the generator power and smooth power fluctuationsfor a wind turbine. Design details and dynamic modeling of this pitch system are presented and analyzed. A practical loadingcompensation approach is synthesized and involved in the pitch system to compensate for the external uncertain pitch loads. Theproposed pitch system and loading compensation approach have been experimentally evaluated in terms of generator powersmoothing and control accuracy. As demonstrated by the comparative experimental results, the proposed pitch system can beused to significantly smooth the generator power fluctuations and hence to improve the power quality as compared with a servovalve-controlled pitch system under the same operating conditions. The loading compensation approach can also be used to sig-nificantly attenuate the effects of external pitch loads and improve the robustness and reliability of the pitch system. The pro-posed pitch system features good control accuracy and cost-efficiency and hence is attractive for applications in modem large-scale wind turbines.展开更多
Based on the Navier-Stokes equations and the Spalart-Allmaras turbulence model,three dimensional turbulent flow fields in centrifugal pump with long-mid-short blade complex impeller are calculated and analyzed numeric...Based on the Navier-Stokes equations and the Spalart-Allmaras turbulence model,three dimensional turbulent flow fields in centrifugal pump with long-mid-short blade complex impeller are calculated and analyzed numerically.The relative velocity and pressure distributions in the flowpart are obtained.It is found that the flow in the passage of the complex impeller is unsymmetrical due to the joint action between volute and impeller.The back-flow region is at inlet of long-blade suction side,near middle part of long-blade pressure side and outlet of short-blade suction side.The flow near volute throat is affected greatly by volute.The relative velocity is large and it is easy to bring back flow at outlet of the complex impeller near volute throat.The static and total pressure rise uniformly from inlet to outlet in the impeller.At impeller outlet,the pressure periodically decreases from pressure side to suction side,and then the static pressure sharply rise near the throat.The experimental results show that the back flow in the impeller has an important influence on the performance of pump.展开更多
基金supported by the Science Fund for Creative Research Groups of the National Natural Science Foundation of China(No.51221004)the National Natural Science Foundation of China(No.51275448)the Fundamental Research Funds for the Central Universities(No.2015QNA4005),China
文摘A rotary valve-controlled pitch system is proposed to regulate the generator power and smooth power fluctuationsfor a wind turbine. Design details and dynamic modeling of this pitch system are presented and analyzed. A practical loadingcompensation approach is synthesized and involved in the pitch system to compensate for the external uncertain pitch loads. Theproposed pitch system and loading compensation approach have been experimentally evaluated in terms of generator powersmoothing and control accuracy. As demonstrated by the comparative experimental results, the proposed pitch system can beused to significantly smooth the generator power fluctuations and hence to improve the power quality as compared with a servovalve-controlled pitch system under the same operating conditions. The loading compensation approach can also be used to sig-nificantly attenuate the effects of external pitch loads and improve the robustness and reliability of the pitch system. The pro-posed pitch system features good control accuracy and cost-efficiency and hence is attractive for applications in modem large-scale wind turbines.
基金supported by National Natural Science Foundation of China granted No.20706049 and No.50976105Zhejiang Provincial Natural Science Foundation Granted No.R1100530 and No.R107635
文摘Based on the Navier-Stokes equations and the Spalart-Allmaras turbulence model,three dimensional turbulent flow fields in centrifugal pump with long-mid-short blade complex impeller are calculated and analyzed numerically.The relative velocity and pressure distributions in the flowpart are obtained.It is found that the flow in the passage of the complex impeller is unsymmetrical due to the joint action between volute and impeller.The back-flow region is at inlet of long-blade suction side,near middle part of long-blade pressure side and outlet of short-blade suction side.The flow near volute throat is affected greatly by volute.The relative velocity is large and it is easy to bring back flow at outlet of the complex impeller near volute throat.The static and total pressure rise uniformly from inlet to outlet in the impeller.At impeller outlet,the pressure periodically decreases from pressure side to suction side,and then the static pressure sharply rise near the throat.The experimental results show that the back flow in the impeller has an important influence on the performance of pump.
