Computational Parametric Study of the Axial and Radial Clearances in a Centrifugal Rotary Blood Pump

In centrifugal rotary blood pumps (RBP), clearances are a critical parameter in determining blood trauma. This study investigates the effect of axial clearance (C-ax) and radial clearance (C-rad) on the hydrodynamic and hemolytic performance of a centrifugal RBP. A centrifugal pump was parameterized so that it could be defined by geometric variables C-ax and C-rad. Optimal Latin hypercube sampling was used to determine design points based on C-ax, C-rad, and rotor speed (). For each design point, a computational simulation was conducted to determine efficiency () and normalized index of hemolysis (NIH). Next, a response surface (RS) was created to estimate these performance parameters based on the design variables. The results show that for a given C-ax, when C-rad is decreased, increases until C-rad = 0.15 mm, beyond which deceases. For a given C-rad, C-ax has a unimodal relationship with . The NIH has a unimodal relationship with both C-ax and C-rad. The mechanisms behind these relationships were investigated by various analytical methods. It was found that vortices in the secondary flow paths were a critical factor in determining efficiency and hemolysis. The optimal clearance values discerned in this study are only valid for the specific impeller geometry and operating conditions analyzed.