Estimation of radial load in centrifugal pumps using computational fluid dynamics

The impeller of a centrifugal pump experiences a significant radial load when operating at off-design conditions. Its average magnitude can be reasonably estimated at the design stage by existing formulas. In contrast, the unsteady component is difficult to estimate since it is affected by the transient properties of the flow. This paper explores the use of a commercial CFD code to estimate the total radial load on the impeller of two test pumps. The full 3D-URANS equations were solved for several flow rates between 10%-130% of rated conditions. The predictions were validated with experimental data of global characteristics and unsteady pressure distribution round the impeller. The code was used to estimate the total radial load (steady and unsteady components) on the impellers as a function of flow rate. It was observed that the unsteady component can represent about a 40%-70% of the average magnitude when operating at off-design conditions.