Numerical Investigation of the Fluid Flow Characteristics in the Hub Plate Crown of a Centrifugal Pump

Due to the lack of understanding in the flow mechanism of the hub plate crown, the current calculation of the disc friction loss and the axial thrust in the centrifugal pump often uses empirical formulas. Research on the flow characteristics of the hub plate crown is of practical significance. The shroud and hub cavities are respectively studied with regard to tangential and radial velocities at the four different angular positions(0°, 90°, 180°, and 270°) at the four different operational points(0.6 Qsp, 0.8 Qsp, 1.0 Qsp, and 1.2 Qsp). Results indicate that at the same operational point, the smaller the volute chamber sectional area is, the higher the tangential velocity of the fluid core zone of the shroud cavity is. Radial leakage flow from the volute to the seal ring at the same operational point appears in 0° and 90° direction;when the flow is large, the tangential and radial velocities of the shroud and hub cavities with the same radius tend to be equal with axial symmetry. The axial leakage flow through the balance holes significantly affects the radial distribution of both tangential and radial velocities of fluid flow in the hub cavity. The numerical calculation results of fluid leakage through the clearance of back sealing ring are in good agreement with the test results. Accordingly, the magnitude of leakage is closely related to the fluid pressure and velocity distribution in the hub plate crown of the centrifugal pump. The analysis of the flow characteristics in the hub plate crown of the centrifugal pump could reveal the cause of the disc friction loss from the mechanism, providing a significant guidance for improving the accuracy of calculation and balancing the axial thrust in the centrifugal pump.

Aerothermodynamic Design and Flow Characteristics for a S-CO_(2) Radial Inflow Turbine

In this paper,a radial inflow turbine is designed for the 150 kW S-CO_(2) Brayton cycle system,and flow characteristics and off-design performances are analyzed.The design results are accurate and high performances can be achieved for the S-CO_(2) power system,and the total-static efficiency of 86%and net output power about 285.2 kW can meet the design requirements of S-CO_(2) cycle system.The results of the flow characteristics show the streamlines of radial inflow turbine distribute uniformly,and the vortexes generated at the shroud of the blade suction surface have little influence on the turbine performances.The off-design performances show the total-static efficiency remains above 80%in the pressure ratio range of 1.6~2.9,and the output power and mass flow rate increase with the pressure ratio increasing.It is indicated that the designed turbine has excellent off-design performances and can meet the operation requirements.The study results can provide guidance for S-CO_(2) radial inflow turbine design and operation.