Estimating the optimal value of diameter of the inlet to the impeller of a centrifugal blood pump

The article is devoted to the optimization of the design of the inlet zone of a centrifugal blood pump. One of the disadvantages of such pumps is the generation of turbulence in the flow of the pumped fluid, which contributes to high blood hemolysis. The reason for turbulence lies in a combination of geometric and kinematic factors, in particular, a 90 degree turn of the flow in the inlet part of the impeller channels and a high circumferential speed of rotation of its channels. The hydrodynamic consequence of this is an increase in the hydraulic resistance of the pump flow path and separation of the boundary layer from the streamlined surface. As a result, the non-uniformity of the flow velocity field increases and separation flow zones appear, stimulating vortex formation and turbulence of the blood flow. The article provides the derivation of an equation for calculating the optimal diameter of the impeller D1, which does not have a bushing in the inlet. This design is typical for centrifugal blood pumps. As a criterion for the optimal value of D1, the minimum level of hydraulic resistance in the inlet zone of the pump was considered. Based on the derived formula, a graph of D1 values was constructed in the range of parameters: blood volume flow 3…6 liters per minute, speed 4000-10000 rpm. With an increase in blood flow and a decrease in the number of revolutions of the impeller, the diameter of the inlet to the impeller must be increased from 6.4 mm to 13.8 mm.