The Blockage Effect Of Vertical Axis Tidal Current Turbine In The Tank

For vertical axis turbine test in the tank,the size of tank working area is limited,and the influence of tank blockage effect,three-dimensional effect and free surface effect is inevitable,which cause the abnormal change of the turbine performance in test.So far,there is no fully and systematically research of tank blockage effect,and lack of performance correction model of turbine test which can correct the above effects.Therefore,it is of great practical significance to research the influence rule and correction method of tank blockage effect,three-dimensional effect and free surface effect on turbine performanceFirst of all,the mechanical characteristic,operating principle and main dimensionless parameters of vertical axis tidal turbine are introduced.The effectiveness of two-dimensional and three-dimensional numerical simulation of vertical axis turbine is verified from gird independence and time step independence point of view,by CFD method based on RANS approach.Tank blockage effect can be divided into sidewall blockage and bottom blockage effect.The influence rule of sidewall blockage effect on turbine performance and load is researched by two-dimensional numerical simulation method,results show that the dimensionless parameters of sidewall blockage effect are blockage ratio,solidity and tip speed ratio;sidewall blockage efffect has no effect on turbine power coefficient when blockage ratio is less than 0.083.Then,the influence rule of three-dimensional effect,free surface effect and bottom blockage effect on turbine performance are researched by three-dimensional numerical simulation method,results show that the dimensionless parameters of three-dimensional effect is the ratio of span to radius or aspect ratio;the influence of three-dimensional effect on turbine performance is small when the ratio of span to radius is 6 or aspect raio is 20;the dimensionless parameters of free surface effect is the ratio of immersion to span or the ratio of immersion to chord length;turbine performance is most obviously improved by free surface effect when the ratio of immersion to span is 0.1 or the ratio of immersion to chord length is 0.6;the dimensionless parameters of bottom blockage effect is the ratio of bottom-turbine length to span or the ratio of bottom-turbine length to chord length;the influence of bottom blockage effect on turbine performance is small when the ratio of bottom-turbine length to span is 2 or the ratio of bottom-turbine length to chord length is 13.33.At last,the correction formulas of the turbine performance in tank test under sidewall blockage effect,three-dimensional effect,free surface effect and bottom blockage effect are given respectively,and correction model of tank blockage effect which can comprehensively correct the above effects are concluded.The research indicate the main dimensionless parameters of tank blockage effect,three-dimensional effect and free surface effect,providing the correction method and correction procedure of the turbine performance in tank test under the above effects for each kinds of vertical axis turbine,moreover,providing the correction formulas of the turbine performance in tank test under above effects for "Wan Xiang ?" turbine,which has great research significance and practical value.