Application of Fluid/Structure Interaction Methods to Determine the Impeller Orbit Curves of a Centrifugal Pump

Sewage water pumps very often are equipped with impellers featuring a small number of blades which therefore provide big cross sections of the flow channel. Single-blade impellers comprise the smallest possible number of blades and are known as non-clogging pumps. But severe disadvantages occur during operation, because the timevariant flow in such pumps results in periodic unsteady flow forces which affect the impeller producing strong radial deflections of it. In order to determine the oscillations of the pump rotor induced by the exciting forces a coupled solution of the flow field in the pump and the structural mechanics of the pump rotor (FSI method) is required. In the present paper simulations which accomplish different coupling methods of the fluid dynamics and the structural dynamics have been carried out for a single-blade pump. In a first approach an explicit partitioned coupling method with simple interchange of boundary conditions has been applied. This approach does not take the feedback of the structural analysis to the flow into account. The results comply only roughly with the measurements. In a second attempt a full coupling of fluid and structural dynamics has been carried out. The simulations were coupled by transferring the computed flow forces as a load for the structural mechanics and the calculated impeller deflection acts as a deformation of the computational grid for the solution of the fluid dynamics. The impeller orbit curves obtained by this method compare much better to the measurements. Key-Words: Fluid/structure interaction, centrifugal pump, impeller orbit curves