Abstract
In the design of rotary blood pumps, the optimization of design parameters plays an essential role in enhancing the hydrodynamic performance and hemocompatibility. This study investigates the influence of the volute tongue angle as a volute geometric parameter on the hemodynamic characteristics of a blood pump. A numerical investigation on five different versions of volute designs is carried out by utilizing a computational fluid dynamics (CFD) software ANSYS-FLUENT. The effect of volute tongue angle is evaluated regarding the hydrodynamic performance, circumferential pressure distribution, the radial force, and the blood damage potential. A series of volute configurations are constructed with a fixed radial gap (5%), but varying tongue angles ranging from 10 to 50°. The relative hemolysis is assessed with the Eulerian based empirical power-law blood damage model. The pressure-flow rate characteristics of the volute designs at a range of rotational speeds are obtained from the experimental measurements by using the blood analog fluid. The results indicate an inverse relationship between hydraulic performance and the tongue angle; at higher tongue angles, a decrease in performance was observed. However, a higher tongue angle improves the net radial force acting on the impeller. The pump achieves the optimized performance at 20° of the tongue angle with the relatively high hydrodynamic performance and minor blood damage risk.
Highlights
Continuous-flow cardiac assist pumps have been successfully used to treat end-stage heart failure patients as destination therapy, bridge-to-transplantation or bridgeto-recovery [1,2,3]
Even though the impeller geometry plays an essential role in the overall performance of a centrifugal blood pump [4], the volute structure is critical for assuring steady flow lines and good kinetic energy to potential energy conversion for achieving greater hydraulic performance and a lower hemolysis risk [5, 6]
The poorest hydraulic performance was realized in the 50° tongue angle with an efficiency of 44.8% and a pressure head of 93.2 mmHg, but the radial force was lowest at 0.2 N among all cases
Summary
Continuous-flow cardiac assist pumps have been successfully used to treat end-stage heart failure patients as destination therapy, bridge-to-transplantation or bridgeto-recovery [1,2,3]. Hemolysis reduction is still a significant design challenge for blood pumps [2, 3]. Even though the impeller geometry plays an essential role in the overall performance of a centrifugal blood pump [4], the volute structure is critical for assuring steady flow lines and good kinetic energy to potential energy conversion for achieving greater hydraulic performance and a lower hemolysis risk [5, 6]. Non-axisymmetric nature of the volute geometry generates a non-uniform pressure distribution around the impeller, inducing a radial force critical for the magnetic suspension of pumps. A few researchers have numerically investigated the hydraulic effect of volute parameters such as the volute tongue in rotary blood pumps [5], yet in these studies the effect of volute tongue position on the hemolytic characteristics is missing
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