CFD Simulation and Design Improvement of Internal Rotating Flow of Turbomachine

Designing a turbomachine comes with many challenges due to many parameters affecting its performance. This study presents a design to reduce losses in turbulence flow and surface friction by using a disk located between the rotating centrifugal impeller and the pump casing, which in turn enhances the centrifugal pump performance, upon rotating freely during normal operation. Under a constant operating speed of 3000 RPM, the new design is shown to improve the centrifugal pump performance. The turbulent flow between the rotating impeller and pump stationary walls increases the frictional losses. The highest friction occurs in the flow between two surfaces, one being close to zero velocity and the other one moving at high speed. Flow recirculation in the enclosure is a major problem that leads to a decrease in turbomachine’s performance. Two-dimensional Computational Fluid Dynamics (CFD) analysis is used to numerically simulate the rotating flow field inside the centrifugal pump chamber and to provide critical hydraulic design information. In this study, ANSYS-FLUENT R19.2 is used to analyze the input torque under different angular velocities by applying a disk with various thicknesses at four different locations to get the best results. The flow field in the chamber is investigated using 2-D Naiver-Stokes Equations with a Realizable k-ϵ turbulence model. Standard water was used as the working fluid. The numerical analysis gives an idea of how the freely rotating disks behave, and the results will be compared to find the most efficient case of centrifugal pump operation with an adjacent disk. The best-case new design will identify the highest reduction of input power by 24.4%. This study will introduce to the future work of a three-dimensional model.