Research On Aerodynamic Characteristics And Pitching Laws Of Vertical Axis Wind Turbine

Wind is a kind of power with the best industrialization,having a dominant position in the renewable energy strategy of our country.As a kind of wind turbine,vertical axis wind turbine(VAWT)has advantages like vertical axis,no yaw,straight blade,and so on.But it can not start-up by itself and its power coefficient is lower than horizontal axis wind turbine(HAWT),which restrict its utilization.Variable pitch vertical axis wind turbine is one way to solve these two problems.However,some problems exist in this technology.For example,it is difficult to obtain experimental data about dynamic aerodynamic performance of blade,understanding about dynamic aerodynamic performance of blade is not clear in present theoretical research,effective pitching rules designed based on experiment is not systematic,mechanism of effective pitching rules is not clear,research on engineering utilization of pitching rules has not been involved,and so on.This paper focuses on above issues and come from two projects.First one is "Research on pitching rules for variable pitch vertical axis wind turbine",which is funded by Heilongjiang Province Natural Science Fund(E201216).Second one is "Research on Mechatronics Design and optimal pitching control for variable pitch Vertical axis wind turbine",which is funded by Fundamental research funds for the central universities(HEUCFZ1118).Operating mechanism of vertical axis wind turbine is analyzed,leading to design requirements of the platform for experimental study of VAWT.Typical wind characteristics of running environment of wind turbine,which is bottom of atmospheric boundary layer,are studied to determine design specifications of wind tunnel.Based on these,wind tunnels for testing airfoil and wind turbine respectively and measuring equipment of wind field are designed.In order to measure static aerodynamic performance of airfoil,an airfoil test bed and corresponding measuring method are designed.In order to study variable pitch VAWT experimentally,measuring method of dynamic aerodynamic driving moments of VAWT is designed,including two measuring method of angular acceleration and corresponding data processing method.Besides,a prototype of variable pitch VAWT is designed.Experiments on single fixed-pitch blade are conducted,in which dynamic driving moments of blade at different tip speed ratios and different pitch angles are measured systematically.Based on these experimental data,mechanism of aerodynamic force on blade is studied.Dynamic mechanical characteristics of blade is analyzed from points of dynamic stall angle,location of driving moment peak,location of maximum driving moment peak,and so on.Based on dynamic mechanical characteristics of blade,existing dynamic stall model is corrected.An assumption about moving streamtube is proposed.Combining with double-disks single-streamtube model and the corrected dynamic stall model,double-disks moving-streamtube model is built.Based on existing experimental data of VAWT,predictive accuracy of this model is verified.Based on Blade Element Theory,theoretical pitching rules are calculated,the relationship between theoretical pitching rules and static aerodynamic characteristics of airfoil is studied,and the correct method of pitching rules is also studied.Based on experimental dynamic driving moments of single fixed-pitch blade,its pitch laws are fitted.Contrasting fitted pitching laws with dynamic mechanical characteristics of blade,design principles of pitching rules are summarized.Three transition programs of pitch angle are proposed,leading to three pitching rule models respectively.To test the validity of pitching rule models,aerodynamic performance of single variable-pitch blade is measured.Engineering application research of pitching rules is studied.Influences of airfoil and chord-radius ratio on dynamic aerodynamic performance of blade are studied experimentally.Based on these,pitching rules for different airfoils and different chord-radius ratios are designed,and aerodynamic performances of blades with these rules are measured.Based on these,applicability of pitching rule model for other airfoils and chord-radius ratios is studied.Influences of pitching errors on aerodynamic performance of pitching blade are studied experimentally,including tip speed ratio error and azimuth angle error respectively.Allowable errors for tip speed ratio and azimuth angle are confirmed,providing design target for future pitching error control method.Experimental studies of variable pitch VAWT are conducted.Comparative experiments are done on fixed-pitch wind turbine and variable-pitch wind turbine respectively.Based on these experimental data,effectiveness of pitching rule model on variable pitch VAWT is verified.Performance of variable pitch VAWT with different blade numbers,different chord-radius ratios and different airfoils is measured.Based on these data,impacts of blade number,chord-radius ratio and airfoil on variable pitch VAWT are studied.