Fluid-structure interaction analysis of an impeller for a high-pressure booster pump for seawater desalination

A High-pressure booster pump (HPBP) is an essential piece of equipment in a Seawater reverse osmosis (SWRO) system. As the corerotating component in the HPBP, the impeller operates extensively in a high-pressure and corrosive environment and its work status directly affects the reliability of the pump device. The vibration characteristics of the rotor were analyzed using fluid-structure interaction theory to determine the characteristics that would ensure the long-term safe operation of the HPBP. The stress and deformation analysis was performed on a partitioned solution for an impeller in a moving fluid, and the modal analysis of the impeller was conducted in still fluid based on a monolithic solution. The influence of the impeller shroud thickness on the resulting vibration characteristics was investigated by using three modifications of the impeller. A comparison of the results with the initial impeller geometry was then carried out under partial load operations. Three commonly used materials for an impeller were also evaluated. The three-dimensional turbulent flow was modeled utilizing the SST k-ω turbulence model, and the numerical results were verified by the experimental data. The results show that natural frequency of the 20CrMnTi is the highest among the three materials for each order mode, followed by 00Cr17Ni14Mo2Ti (316L) and HT250Ni2Cr. Increasing the rear shroud thickness would result in a notable reduction in its deformation. Evidently, the thicker the front and rear shrouds, the lower the shroud deformations. Among the three operating points, the displacement fields of the impeller were quite akin. An outward displacement growth was observed within the impeller hub to the outer diameter, thereby leaving both shrouds with a local maximum on the blade passage. Additionally, higher equivalent stress values were observed at the junction between the blade and the shroud. These results reveal the deformation and stress affecting the impeller, which then enables identification of and provides specific theoretical guidance for the optimization of the structural design of the pump.