3-Dimensional Viscous Fluid Flow In A Volute Of Centrifugal Oil Pump

The work is one part of a project that was supported formerly by the Key Research and Development Program for Outstanding Groups in 2003 at Lanzhou University of Technology.The volute centrifugal oil pump, which is widely used in petrochemical process, is one kind of centrifugal oil pumps. The volute of the pump is an important component for liquid delivery. Because liquid presents viscosity, the energy (hydraulic) losses exist in the volute. In addition, the internal flow in the volute affects the pressure distribution around the impeller, as a result, the radial force is generated and the impeller operation reliability is impacted. In order to make the centrifugal oil pump having a better hydraulic performance and higher reliability, the detailed studies on the internal flow and hydraulic performance of volute have been performed by researchers at home and abroad. However, the 3D turbulent and laminar viscous flow in the volute is not investigated currently. This complex 3D flow and hydraulic performance of the volute of centrifugal oil pumps attempt to be studied in this thesis with Computation Fluid Dynamics (CFD) method to explore the internal flow features of viscous fluid as well as to provide a theoretical basis for performance analysis and hydraulic design of the volute of centrifugal oil pumps.The 3D turbulent and laminar internal flow fields have been calculated in a 90° square-sectional bend,two curved and around-sectional diffusers with different diffusing angles and the volute of a centrifuge oil pump for various fluid viscosities by using CFD software FLUENT6.1.2 CFD and geometry and mesh builder GAMBIT2.0, respectively. The numerical results have been compared with the corresponding experimental data. The effects of both number of grid and turbulent models on the numerical results have been conducted. The flow patterns in the volute, pressure recovery coefficient and hydraulic loss coefficient of the volute have been given for various fluid viscosities. The effects of flow rate, fluid viscosity, volute wall roughness on the internal flow, hydraulic performance have been examined. The following results may be shown:(1)The minor loss coefficient of the 90° bend is related to Reynolds number. (2)The pressure recovery ability is degraded as Reynolds number reduces for the curved diffuser, and the hydraulic losses rise.(3)The flow in the volute is uneven and the secondary flow exists.(4)The internal flow, pressure recovery coefficient and hydraulic loss coefficient in volute are affected by the flow rate.(5) The viscosity of liquid pumped affects significantly on the volute internal flow field, pressure recovery coefficient and hydraulic loss coefficient and radial force. The high viscosity not only raises the hydraulic losses in volute and causes strong radial force, but also leads the diffuser to lose its pressure recovery function and the hydraulic performance is deteriorated.(6)The hydraulic losses mainly occur in the spiral part of volute, but the proportion of the losses in the diffuser of volute rises when the liquid viscosity increases. Thus, the more attention should be paid on the design of diffuser for the liquid with high viscosity.(7)The blade middle-span at impeller outlet not in the symmetrical plane of the volute has a certain influence on the secondary flow patterns in volute section, but less on the hydraulic performance and radial force.(8)The volute wall roughness has relatively small influence on the volute internal flow field, hydraulic performance and radial force.