Impeller (straight blade) design variations and their influence on the performance of a centrifugal blood pump

Introduction: The miniaturization of blood pumps has become a trend due to the advantage of easier transplantation, especially for pediatric patients. In small-scale pumps, it is much easier and more cost-efficient to manufacture the impeller with straight blades compared to spiral-profile blades. Methods: Straight-blade impeller designs with different blade angles, blade numbers, and impeller flow passage positions are evaluated using the computational fluid dynamics method. Blade angles (θ = 0°, 20°, 30°, and 40°), blade numbers (N = 5, 6, 7, and 8), and three positions of impeller flow passage (referred to as top, middle, and bottom) are selected as the studied parametric values. Results: The numerical results reveal that with increasing blade angle, the pressure head and the hydraulic efficiency increase, and the average scalar shear stress and the normalized index of hemolysis decrease. The minimum radial force and axial thrust are obtained when θ equals 20°. In addition, the minimum average scalar shear stress and normalized index of hemolysis values are obtained when N = 6, and the maximum values are obtained when N = 5. Regarding the impeller flow passage position, the axial thrust and the stagnation area forming in the impeller eye are reduced as the flow passage height declines. Conclusion: The consideration of a blade angle can greatly improve the performance of blood pumps, although the influence of the blade number is not very easily determined. The bottom position of the impeller flow passage is the best design.