Flow investigation in a centrifugal pump

Abstract

The alarming escalation in statistics of patients suffering and dying from cardiovascular diseases around the world raises the importance of the treatments available. The ventricular assist device is one option and its demand is on the rise due to the shortage of heart donors. Increased demand of the ventricular assist device has also resulted in the emergence of centrifugal blood pump due to its simplified design and economical cost. However, concerns of problems like haemolysis as well as thrombus formation in the leakage gaps of the centrifugal blood pump are hindering the prospects of permanent implantation. Knowledge and analysis on the leakage flow will help in the improvements of the pump design, thus reducing the effects of haemolysis and thrombus formation.

A computational fluid dynamics analysis of a centrifugal blood pump model using ANSYS CFX 11.0 was conducted in this study. The leakage flow characteristics of the pump model with impeller rotating at 2000 rpm were investigated. Four parallel gaps with sizes ranging from 0.2mm to 0.5mm were employed in investigation.

The pump performance was reported to be independent of the gap size as all four curves generated using the results obtained from the four gap sizes collapsed into a single curve. Leakage flow rate increases with increasing gap sizes as well as throttling effects. A higher leakage flow rate was noted at the front leakage gap with reference to the rear leakage gap due to the presence of washout holes.

Besides a higher leakage flow rate, a greater pressure difference is also experienced at the front leakage gap. Maximum pressure difference was reported at the region near the throat of the pump and pressure difference was found to decrease with increasing operating flow rate.