In the design of centrifugal pump, generally need to be given the design parameters of this: flow Q, head H, speed N, cavitation margin NPSHr and efficiency, etc.. According to the above parameters can be determined preliminarily centrifugal tip structure scheme and calculate the impeller of specific speed ns, and then use some empirical data (formula) to determine the impeller of the main geometric dimensions. In the hydraulic design of centrifugal and mixed flow pump impeller, it is assumed that the impeller fluid flow is axisymmetric flow, the flow velocity of any point can be decomposed into axial plane (including the impeller axis plane) within the axial components of velocity and circumferential velocity component. The distribution of the axial velocity component is determined by the rotation of the impeller flow channel and the boundary condition at the entrance of the impeller, and the distribution of the circumferential velocity is determined by the distribution of the axial velocity component and the angle of the blade. Therefore, the first step in the design of the impeller is to determine the axial velocity and circumferential velocity.
