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.
Numerical simulation of unsteady flow in a multistage centrifugal pump using sliding mesh technique
In this work, three-dimensional, unsteady Reynolds-Averaged Navier?Stokes (RANS) equations with standard k-e turbulence models are solved by employing sliding mesh technique within an entire stage of a multistage diffuser pump to investigate transient flow field and pressure fluctuations due to the interaction between impeller and diffuser vanes. Sliding mesh calculation is carried out as the impeller zones slide (i.e., rotate) relative to diffuser zone along the grid interface in discrete time steps. The complicated time-periodic and spatial-periodic characteristics as well as rotor?stator interaction phenomena inside the pump stage are simulated and analysed to understand dynamic variation of the interior flow field and interference and finally to aim at optimal design.
Effect of antioxidants, on deterioration by partial discharge in LDPE and XLPE [insulation materials]
The effect of antioxidants in low-density polyethylene (LDPE) and cross-linked polyethylene (XLPE) on deterioration by partial discharge (PD) was investigated. Experiments were conducted using LDPE and XLPE samples containing phenolic antioxidants. Samples subjected to the PD were analyzed using atomic force microscopy and Fourier transform infrared analysis (AFM and FTIR). AFM images demonstrated that the magnitude of pits created in the sample containing antioxidants was smaller than that in samples containing no antioxidant. FTIR showed that oxidative degradation occurred on LDPE and XLPE surfaces when they were subjected to PD. These results confirmed that the amount of oxidized substances was smaller in samples containing phenolic antioxidants than in those containing no antioxidant. This report elucidates the mechanism of antioxidant action on deterioration by PD.