Design Considerations of Volute Geometry of a Centrifugal Blood Pump

Abstract

This article compares two different design techniques that are conventionally used in the design of volutes for centrifugal pumps. The imbalanced forces due to the geometry of the volute need to be taken into consideration especially in centrifugal blood pumps with magnetically suspended impeller. A reduction of these forces can reduce the instability of the impeller motion as well as the power needed to counteract its influence. Volutes using the constant angular momentum (CAM) and the constant mean velocity (CMV) methods were developed and modeled numerically. The computational results on the effect of volute geometry on the performance of a centrifugal blood pump impeller for six different volutes are presented here. For volutes designed using the CAM method, model B (volute expansion angle of 3 degrees ) had the lowest radial force of 0.26 N while the pressure head generated was 12,900 Pa. For volutes designed using the CMV method, model F (1.6 m/s) had the lowest imbalanced force of 0.45 N. However, the pressure developed by this pump was also one of the lowest at 10,652 Pa. Furthermore, when the peak scalar stresses and the mean exposure time of particles for all designs were determined using Lagrangian particle tracking method, it was observed that in general, the peak scalar stresses in CAM designed volutes are lower than those designed using CMV method. The mean exposure time of particles in the pump ranged from 400 to 500 ms. The simulation results showed that the volute designed using CAM method was superior to that of a CMV volute in terms of the magnitude of the radial force and the peak scalar stresses for the same pressure head generated. Results show that the design of volutes for blood pumps should go beyond conventional empirical methods to obtain optimal results.

Prediction of Leakage Flow in a Shrouded Centrifugal Blood Pump

“…Mass flow rate was prescribed at the inlet boundary and static pressure at the outlet boundary. It was verified that a good agreement was achieved between the current CFD solution and previously published experiments performed on a similar setup with less than 5% deviation in pump head (14).…”

Effects of Tongue Position and Base Circle Diameter on the Performance of a Centrifugal Blood Pump

“…Details of the boundary conditions and computational settings are described by Chan et al (9). The simulation results using fine grid (150 000 cells) and coarse grid (100 000 cells) were compared with experimental data and have been validated in the study by Chan et al (9). Figure 3 illustrates the flow patterns at the midplane for three radial gaps.…”

“…640 the volute profile, the base circle diameter D3 and the tongue shape and position play an important role in determining the flow pattern and overall pump performance. Investigations of the effect of the volute profile on blood pumps performance are described in Chan et al (9).…”

“…Although the actual volute flow would not completely follow the angular momentum conservation, this method also yields rather good performance. The performance of volute designed by constant angular momentum method also relies on selecting appropriate empirical constants.A comparison of the two methods applied to the design of blood pump volutes is presented by Chan et al (9).…”

“…This is particularly critical to the operation of MSCBP and may lead to pump failure. From literature (9,10), the radial force is dependent on two factors: the volute casing geometrical parameters and the flow pattern leaving the impeller outlet. At the design flow rate, the volute geometry plays a key role in determining the magnitude and direction of the radial force.…”