The authors have invented a unique counter-rotating type tidal stream power unit, which is composed of tandem propellers and a double rotational armature type generator without a stator. The front and the rear propell...The authors have invented a unique counter-rotating type tidal stream power unit, which is composed of tandem propellers and a double rotational armature type generator without a stator. The front and the rear propellers drive, as for an upstream type, the inner and the outer rotational armatures in the counter-rotating directions respectively, which keep the rotational torques counter-balanced between both propellers and armatures. This paper investigates experimentally the output and forces acting on a pile in a water channel, to get design materials of the mono-pile type tidal stream power unit. The output is maximal at the moderate rotational speed, as the same as a wind turbine. The force acting on the pile is affected by the drag, the Karman vortex and the dynamic balances of the tandem propellers, and has dominant frequencies due to not only the individual but also the interacting rotation of the front and the rear propellers.展开更多
Small propeller-type wind turbines have a low Reynolds number,limiting the number of usable airfoil materials.Thus,their design method is not sufBciently established,and their performance is often low.The ultimate goa...Small propeller-type wind turbines have a low Reynolds number,limiting the number of usable airfoil materials.Thus,their design method is not sufBciently established,and their performance is often low.The ultimate goal of this research is to establish high-performance design guidelines and design methods for small propeller-type wind turbines.To that end,we designed two rotors:Rotor A,based on the rotor optimum design method from the blade element momentum theory,and Rotor B,in which the chord length of the tip is extended and the chord length distribution is linearized.We examined performance characteristics and flow fields of the two rotors through wind tunnel experiments and numerical analysis.Our results revealed that the maximum output tip speed ratio of Rotor B shifted lower than that of Rotor A,but the maximum output coefficient increased by approximately 38.7%.Rotors A and B experienced a large-scale separation on the hub side,which extended to the mean in Rotor A.This difference in separation had an impact on the significant decrease in Rotor A's output compared to the design value and the increase in Rotor B's output compared to Rotor A.展开更多
文摘The authors have invented a unique counter-rotating type tidal stream power unit, which is composed of tandem propellers and a double rotational armature type generator without a stator. The front and the rear propellers drive, as for an upstream type, the inner and the outer rotational armatures in the counter-rotating directions respectively, which keep the rotational torques counter-balanced between both propellers and armatures. This paper investigates experimentally the output and forces acting on a pile in a water channel, to get design materials of the mono-pile type tidal stream power unit. The output is maximal at the moderate rotational speed, as the same as a wind turbine. The force acting on the pile is affected by the drag, the Karman vortex and the dynamic balances of the tandem propellers, and has dominant frequencies due to not only the individual but also the interacting rotation of the front and the rear propellers.
文摘Small propeller-type wind turbines have a low Reynolds number,limiting the number of usable airfoil materials.Thus,their design method is not sufBciently established,and their performance is often low.The ultimate goal of this research is to establish high-performance design guidelines and design methods for small propeller-type wind turbines.To that end,we designed two rotors:Rotor A,based on the rotor optimum design method from the blade element momentum theory,and Rotor B,in which the chord length of the tip is extended and the chord length distribution is linearized.We examined performance characteristics and flow fields of the two rotors through wind tunnel experiments and numerical analysis.Our results revealed that the maximum output tip speed ratio of Rotor B shifted lower than that of Rotor A,but the maximum output coefficient increased by approximately 38.7%.Rotors A and B experienced a large-scale separation on the hub side,which extended to the mean in Rotor A.This difference in separation had an impact on the significant decrease in Rotor A's output compared to the design value and the increase in Rotor B's output compared to Rotor A.
