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 2D NUMERICAL AND EXPERIMENTAL INVESTIGATION ON THE PRESSURE FLUCTUATIONS INSIDE A DOUBLE VOLUTE CENTRIFUGAL PUMP AT THREE DIFFERENT RADIAL GAPS
Pressure fluctuations in centrifugal pumps are one of the most traumatic issues that exist as a result of the interaction between the rotor "impeller" and stator "volute". The experiments that were carried out on the double volute pump model in Saudi Arabia have proved that the radial gap "clearance" between the impeller and the tongue of the volute plays a major role in increasing and decreasing that vibrations that are generated due to the pressure fluctuations. Unsteady 2D simulations were carried out on the model to study the pressure fluctuations especially at the critical locations such as around the impeller , the cutwater, and the volute tongue. The results show that the sliding mesh technique is a very useful procedure for simulating these kinds of simulations. The results also show that the peak of the pressure fluctuations occurs at the first blade passing frequency for the 3 gaps "2, 3.6, 7"mm. Numerical static pressure was captured accurately for each gap but the amplitude of the pressure fluctuations were overestimated due to the inaccurate nature of the 2D simulations. The highest gap "7 mm" is the best solution for the vibrations and noise reduction due to the decrease in the pressure fluctuations without affecting the performance of the pump greatly. The performance curves are discussed.
Properties of a monopivot centrifugal blood pump manufactured by 3D printing
An impeller the same geometry as the impeller of a commercial monopivot cardiopulmonary bypass pump was manufactured using 3D printing. The 3D-printed impeller was integrated into the pump casing of the commercially available pump to form a 3D-printed pump model. The surface roughness of the impeller, the hydraulic performance, the axial displacement of the rotating impeller, and the hemolytic properties of the 3D-printed model were measured and compared with those of the commercially available model. Although the surface roughness of the 3D-printed model was significantly larger than that of the commercially available model, the hydraulic performance of the two models almost coincided. The hemolysis level of the 3D-printed model roughly coincided with that of the commercially available model under low-pressure head conditions, but increased greatly under high-pressure head conditions, as a result of the narrow gap between the rotating impeller and the pump casing. The gap became narrow under high-pressure head conditions, because the axial thrust applied to the impeller increased with increasing impeller rotational speed. Moreover, the axial displacement of the rotating impeller was twice that of the commercially available model, confirming that the elastic deformation of the 3D-printed impeller was larger than that of the commercially available impeller. These results suggest that trial models manufactured by 3D printing can reproduce the hydraulic performance of the commercial product. However, both the surface roughness and the deformation of the trial models must be considered to precisely evaluate the hemolytic properties of the model.