Design And Aerodynamic Analysis Of Low-speed Wind Turbine With Lobed Ejector Based On Its Ejection Characteristics

National 13 th Five-Year Plan emphasizes the necessity of optimizing the structure of energy supply, improving energy utilization efficiency, and increasing the use of renewable green energy. As one type of common renewable energy, the development and utilization of wind energy resource should be given more attention. Working at low wind speed condition, energy utilization efficiency of traditional wind turbine is quite small. Based on the ejection characteristic of lobed mixer, this paper designed a kind of ejecting wind turbine, which combined lobed mixer with wind wheel, so as to achieve the purpose of efficient utilization of low-grade wind energy.Firstly, Wilson model of Blade Element Momentum Theory was adopted to establish the objective function and constraints, and computer programming was conducted to solve the problem in the duration of designing blades of wind turbine. Then CFD method was used to analyze the flow field which provided guidance for the subsequent design process.Secondly, quantitative relations of geometry parameters of “arch-like” lobed mixer was derived for parametric modeling by changing a few parameters conveniently. Numerical Simulation was applied to study the formation and development of streamwise vortex and normal vortex and reveal the mechanism of fluid of external duct sucks and accelerates the fluid of inner passage. Then the effects of swirl angle on vortex structure and comprehensive performance of lobed mixer were studied. The results show that within the swirl angle range from 0° to 30°, the greater swirl angle is, the greater nonuniformity of the outlet pressure and total pressure loss coefficient will be, while the ejection coefficient will be smaller. So the swirl angle should be reasonable controlled in the design process.Finally, on the foundation of mechanism studied above, the paper designed a new kind of ejecting wind turbine, which used lobed mixer as external duct. Considering the detrimental influence of outlet flow angle of wind blades on the ejection characteristics of the lobed mixer, lobe was twisted around the central axis. Numerical method was adopted to analyze and compare the aerodynamic characteristics of original wind turbine, untwist-lobe wind turbine and twist-lobe wind turbine. The simulation reveals that stream-wise vortex and normal vortex induced by lobed mixer, tip spiral vortex and root vortex caused by wind wheel and edge vortex incurred by external duct pull and screw each other and constitute complex vortexes structure of flow field. These vortexes reduce the static pressure of the outlet of wind wheel, strengthen the ejection ability and enhance the mass flow and enthalpy drop of fluid through the wind turbine, thus effectively increasing the energy utilization efficiency of low-grade wind energy whose velocity varies from 3.0m/s to 6.0m/s. As for untwist-lobe wind turbine, the wind energy utilization coefficient is 61.57% ~ 63.70%, while twist-lobe wind turbine has better ejection performance and its value is 64.06%~66.23%.