Effect of the Center Post Establishment and Its Design Variations on the Performance of a Centrifugal Rotary Blood Pump.

PURPOSE

The main purpose is to compare the characteristics and performance of a centrifugal blood pump with and without center post. Furthermore, to propose a center post design guide for the development of centrifugal blood pumps: finding the appropriate height and diameter of the center post.

METHODS

A centrifugal blood pump with different center post configurations is investigated using Computational Fluid Dynamics (CFD) in an extensive parametric approach. Height and diameter of the center post are varied on 4 levels each. Pressure head and hydraulic efficiency curves, pressure and velocity contours and volumetric histograms of scalar shear stress (SSS) distribution are discussed in detail.

RESULTS

The simulation results show uniform pressure distribution around the casing in the baseline design. Although obtaining the minimum Normalized Index of Hemolysis (NIH), average scalar shear stress (ASSS), and volumetric percentage ratios (SSS > 9, 50 and 150 Pa), a stagnation and recirculation zone in the impeller eye above the casing bottom is detected in center post free (H = 0 mm) pump. With the establishment and further increase of the center post height, the stagnation zone disappears gradually. The results also indicate that flow recirculation and stagnation around the circumference of the center post occurs when the center post has a small diameter. As the diameter increases, a reversed flow is formed between the impeller and the center post.

CONCLUSIONS

The center post can greatly reduce the stagnation zone occurring in the center post free pump. The diameter of center post makes a difference to the flow field in the gap between the impeller and the center post.