Numerical Analysis of the Flow Through in Centrifugal Pumps
In order to investigate the flow structure in centrifugal pump, a numerical model based on three dimensional (3D) incompressible Reynolds-Averaged Navier-Stokes equations has been developed. The turbulence viscosity is computed using the SST model (Shear Stress Transport). These transport equations associated with the appropriate boundaries conditions are solved by the CFX-13 finite-volume code. The computational domain composed by a single stator and rotor blade passages is discretized by a structured multi-block meshes. It describes in detail the numerical approach, based on an approach URANS (Unsteady Reynolds Average Navier Stokes) to predict the pressure fluctuations. On the other hand, simulations digital steady are made to construct the performance for centrifugal pump ( NS32). The unsteady simulations have allowed access to the temporal behavior of internal flow and compare the influence of two parameters in particular: mesh and conditions limits finding it difficult to model the pressure fluctuation The velocity and pressure fields show a radial thrust. Conformed to experimental visualization.
A Study on Multistage Centrifugal Pump Performance Characteristics for Variable Speed Drive System
Abstract Nowadays centrifugal pumps are being widely used in the commercial, industrial and power plant applications and most of pumps operated by constant speed drive system. Therefore, pump consumes a huge energy of each nation's total energy. But it could be operated in variable speed drive system which would be provided energy saving. The purpose of this study is to investigate the pump performance characteristics of the multistage centrifugal pump with the variable drive system. For this study an experimental set up of the system was constructed to achieve the centrifugal pump performances such as H-Q, η-Q, P-Q curves and operating points which interact between performance and system curves. In the variable speed drive system, a vector controlled inverter driving (variable voltage variable frequency) was installed in the experimental system. A numerical investigation also applied for getting the pump performances for the validation and reliability of the pump design development and also the pressure and velocity effects in internal flows of the pump are analyzed. For the numerical analysis, the Navier-Stokes equations were discretized by the finite volume method and two equations transport turbulence (SST) model accounts for three dimensional steady flows. In the experiment system, we also carried out system head performance of the three pumps in parallel to compare with one pump system head for its validation. In order to get the energy saving rate using the inverter control variable speed drive system instead of the constant speed drive system, it is necessary to identify the specific duty cycle of the pump operation cycle and operating system curve of the pump. Hopefully, this paper will be useful as a guide for identifying a method of implementing a variable speed drive system with inverter control in the variable flow and pressure system.
Detailed flow measurements within the impeller and the vaneless diffuser of a centrifugal turbomachine
Abstract The flow within the impeller and the vaneless diffuser of a centrifugal turbomachine model operating at the nominal point has been experimentally investigated. The radial and circumferential velocities and the associated turbulent fluctuations have been measured on seven cross-sectional circumferential surfaces, four within the impeller and three in the vaneless diffuser by means of a four-beam two-color fibre optic laser-Doppler velocimeter. To complete the flow investigation, LDV measurements have been performed on the blade-to-blade plane at mid-span. Data acquired have been processed by means of a phase locked ensemble-average technique in order to separate periodic from turbulent fluctuations. The results show the impeller flow structure, the development and decay of the blade and through-flow wakes and the main features of the diffusing flow. The present experimental work provides a well documented data base suitable for the assessment of turbomachinery flow prediction codes.