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.
Flow in a Centrifugal Pump Impeller at Design and Off-Design Conditions—Part I: Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV) Measurements
Detailed optical measurements of the flow inside the rotating passages of a six-bladed shrouded centrifugal pump impeller of industrial design have been performed using particle image velocimetry (PIV) and laser Doppler velocimetry (LDV). Results include instantaneous and ensemble averaged PIV velocity vector maps as well as bin-resolved LDV data acquired in the midplane between hub and shroud of the impeller. The flow is surveyed at both design load and at severe off-design conditions. At design load, Q =Q d , the mean field of relative velocity is predominantly vane congruent, showing well-behaved flow with no separation. At quarter-load, Q=0.25Q d , a previously unreported two-channel phenomenon consisting of alternate stalled and unstalled passages was observed, with distinct flow congruence between every second of the six passages. A large recirculation cell blocked the inlet to the stalled passage while a strong relative eddy dominated the remaining parts of the passage. The stall phenomenon was steady, nonrotating and not initiated via the interaction with stationary components
Effect of flow rate on loss mechanisms in a backswept centrifugal impeller
Abstract Detailed measurements of the three velocity components, total, and static pressures on five measurement planes without a low speed shrouded backswept centrifugal impeller are presented. A comparison is made between the design flow field and the flow fields for both below and above design flow rates. The flow is dominated by a passage vortex that rotates in the opposite direction to the impeller. This vortex develops in the inducer, is strongest in the axial to radial bend, and then decays toward the outlet. The vortex is also most prominent at the lowest flow rate and is responsible for stabilizing the shroud boundary layer and hence reducing the large losses associated with the separation of this boundary layer in radial impellers. At the outlet, the wake is located on the shroud at all flow rates, but tends to be spread more evenly across the shroud than is the case in a radial machine. The impeller efficiency is also generally found to be higher at lower flow rates in contrast to observations for radial impellers.