After long-term operation, the material loss due to slurry erosion often leads to significant changes in the impeller geometry. This change can, in turn, affect the flow characteristics and the erosion mechanism in a centrifugal pump. To investigate this matter, we consider two geometric models based on a prototype stainless steel impeller, which failed due to huge erosion problems from the pulp slurry. These two models are different in the degree of wear, with one model at the pre-erosion stage and the other with worn blades. For both models, the flow characteristics have been obtained in the Eulerian reference frame by means of the SST k-ω model. Then, in order to determine the erosion patterns, the particles have been tracked in the Lagrangian reference frame. In this way, the influence of the flow characteristics on the erosion patterns has been analyzed. Results show that the geometric variations greatly affect the flow characteristics, and consequently the erosion patterns. Particularly, it has been found that the clearance flow plays a significant role in defining erosion characteristics, such as erosion distribution, areas, and rates. Interestingly, the simulation results for current study show that the erosion rates after long-term operation greatly decrease near both the outlet edge and the blade bottom. It follows also that for accurate erosion predictions, these geometric variations have to be considered in the numerical model. This paper provides a better understanding of the complex erosion mechanism in centrifugal pumps, which can help to reduce the wear in future designs.

The hydraulic performance of Pelton turbine is different from reaction turbines due to its unsteady flow of rotating buckets with time and space. The water sheet flow in Pelton turbine is also very complex as the jet flow is often interacted with air and itself. This paper numerically investigates the dynamic hydraulic performance of a Pelton under super-high head. Unsteady numerical simulations were performed using SST k-ω. Two-phase homogeneous model and VOF were adopted to model he free surface flow. The evolution history of water sheet flow in the buckets were presented. The distribution of pressure coefficient on the bucket surface were also analysed. The results indicate that the development of water sheet flow on the bucket surface can be divided into three stages, corresponding to the output power variation process. This calculation can be used to illustrate the hydraulic mechanism of water sheet flow evolution.

The bulb turbine is widely used in low-head hydropower stations. Due to its relatively short inflow channels, the flow patterns inside the turbines are easily affected by the upstream conditions. The oblique inflow may occur when then the overflow gates are closed, and the oblique angle differs with different installation positions for the turbines. In this paper, the effect of oblique inflow conditions on the turbine performances is numerically investigated for the low-head bulb turbine. Firstly, the effect of inflow conditions on the flow patterns inside the turbine was predicted. Secondly, the hydro performances of the turbines under different oblique angles are discussed. Results show that the oblique inflow can sufficiently affect the turbine flows patterns and turbine performances. A positive oblique angle would lead to a lower efficiency for the turbines compared to a negative oblique angle.