The principle of moving blade adjustment :
Liquid flow through the airfoil, the liquid will produce a lift on the blade, the direction and the direction of the flow velocity of liquid phase vertical; liquid has the resistance of the blade, the direction and the direction of the flow velocity of liquid phase parallel.
The lift coefficient and the drag coefficient are related to the geometry of the airfoil and the angle of the airfoil when the shape of the airfoil and the Reynolds number are certain. The drag coefficient increases with the increase of the impact angle, and the lift coefficient increases with the increase of the impact angle. When the impact angle is increased to a certain value, the resistance coefficient increases to the maximum. If the impact angle increases, the lift coefficient decreases sharply, and the lift force decreases rapidly, which is due to the separation of the back boundary layer of the airfoil blade, which is the result of the separation of the fluid from the blade. At this time in the formation of a large vortex behind the vortex area, so that the lift down, this situation is called stall. When the impact angle increases to the stall point, the aerodynamic characteristics are greatly deteriorated, the working condition is poor, the efficiency is reduced, and the noise and the violent vibration are accompanied. Therefore, be sure to avoid work under the stall.
Through the analysis of leaf fluid is conducted, and the above is basically the same. The flow velocity in the formula of the lift and drag coefficient should be replaced by the geometric mean value of the relative velocity of the Ye Zhajin and the exit. The relationship between lift coefficient and drag coefficient and impact angle is consistent.
In summary, if the angle between the airfoil blade and the flow velocity direction is changed, the lift coefficient is changed, and the lift force is changed. After the lift change, the flow and head of the axial flow pump is changed, so that the purpose of regulating the axial flow pump is achieved.
At present, the large axial flow pump and mixed flow pump with movable blade has been widely used. Movable blade adjustment, that is, the installation angle of the movable blade can be changed with different conditions, so that the pump at a low load efficiency greatly improved. When the blade mounting angle increases, the flow, head, power of the performance curve increases, and vice versa. When starting the installation angle can be reduced to reduce the starting power. When the blade angle is changed, the efficiency curve is changed, but the high efficiency can be kept in a large flow range, and the throttling loss of the valve regulating flow can be avoided, and the economic benefit is improved.
