Influence of circumferential annular grooving design of impeller on suspended fluid force of axial flow blood pump

Aiming at insufficient suspension force on the impeller when the hydraulic suspension axial flow blood pump is start at low speed, the impeller suspension stability is poor, and can’t quickly enter the suspended working state. By establishing the mathematical model of the suspension force on the impeller, then the influence of the circumferential groove depth of the impeller on the suspension force is analyzed, and the annular groove depth on the impeller blade in the direction of fluid inlet and outlet was determined as (0.26, 0.02 mm). When the blood pump starts, there is an eccentricity between the impeller and the pump tube, the relationship between the suspension force and the speed of the impeller under different eccentricities is analyzed. Combined with the prototype experiment, the circumferential annular grooving design of the impeller can make the blood pump rotate at about 3500 rpm into the suspension state, when the impeller is at 8000 rpm, the impeller can basically achieve stable suspension at the eccentricity of 0.1 mm in the gravity direction, indicating that the reasonable circumferential annular grooving design of the impeller can effectively improve the suspension hydraulic force of the impeller and improve the stability of the hydraulic suspension axial flow blood pump.

Analysis of a Novel Magnetic-Hydrodynamic Double Levitated Motor for an Implantable Axial Flow Blood Pump

This paper presents a novel design for a bearingless axial flow blood pump based on the magnetic-hydrodynamic double levitated concept. In the axial direction, the magnetic levitation system consisted of two pairs of permanent magnet rings offsets the force of fluid. The hydrodynamic shell mounted on the impeller rotor is designed for generating dynamic pressure, which can balance the radial force like gravity when the blood pump is working. Because of the unsteady force and torque acting on the rotor and the passive suspension, the position of the rotor is not steady. The suspension force, stiffness, and torque of the rotor are calculated by the theoretical method and finite element method. Then, the dynamics of the rotor are analyzed. Arrangements of Hall-effect sensors with the corresponding data acquisition system which can measure the axial displacement of the rotor are explained. The sensorless drive control system for the blood pump is described too. With a prototype pump, an external circulation experiment system is built and then the axial and radial displacements of the rotor are measured by using Hall-effect sensors and the laser vibrometer under different working conditions.

Numerical analysis of the effect of the design of axial-flow pump cannula tip on stagnation and recirculation zones in the left ventricle

Objective: to analyze the inflow cannula of an implantable axial-flow blood pump for a long-term left ventricular assist system in order to minimize thromboembolic complications. Materials and methods. Hemodynamics was considered for 4 different designs of the inflow cannula, from 0 mm to 25 mm long. Areas at the base of the cannula received the most attention. Analysis was performed using the OpenFOAM software. Results. It was revealed that sizes of stagnation and recirculation zones directly depended on the length of the cannula when placed in the left ventricle. Accordingly, longer cannula increases the risk of thrombosis. Conclusion. The design of an inflow cannula determines the likelihood of thrombosis in the cannula. Longer inflow cannula increases stagnation and recirculation zones. This provides a basis for a search for other possible modifications.

Analysis of flow field and hemolysis index in axial flow blood pump by computational fluid dynamics–discrete element method

To fully study the relationship between the internal flow field and hemolysis index in an axial flow blood pump, a computational fluid dynamics–discrete element method coupled calculation method was used. Through numerical analysis under conditions of 6000, 8000, and 10,000 r/min, it was found that there was flow separation of blood cell particles in the tip of the impeller and the guide vane behind the impeller. The flow field has a larger pressure gradient distribution, which reduces the lift ratio of the blood pump and easily causes blood cell damage. The study shows that the hemolysis index obtained by the computational fluid dynamics—discrete element method is 4.75% higher than that from the traditional computational fluid dynamics method, which indicates the impact of microcollision between erythrocyte particles and walls on hemolysis index and also further verifies the validity of the computational fluid dynamics–discrete element coupling method. Through the hydraulic and particle image velocimetry experiments of the blood pump, the coincidence between numerical calculation and experiment is analyzed from macro and micro aspects, which shows that the numerical calculation method is feasible.

Multi-parameter analysis of the effects on hydraulic performance and hemolysis of blood pump splitter blades

The splitter blade can effectively optimize pump performance, but there is still insufficient research in blood pumps that cover both hydraulic and hemolysis performance. Thus, the aim of this study was to investigate the effect of key factors related to splitter blade on the performance and flow field of axial flow blood pump. In this study, the number of splitter blades, the axial length, and the circumferential offset were chosen as three objects of study. An analysis of the flow field and performance of the pump by orthogonal array design using computational fluid mechanics was carried out. A set of hydraulic and particle image velocimetry experiments of the model pumps were performed. The result showed that the pump had greater hydraulic performance without sacrificing its hemolytic performance when it had two splitter blades, the axial length ratio was 0.6, and the circumferential offset was 15°. Based on these reference data, the splitter blade may contribute to greater hydraulic performance of the pump and cause no side effect on the velocity distribution of the flow field. This finding provides an effective method for the research, development, and application of structural improvement of the axial flow blood pump.

Study on the influence of dynamic/static interface processing methods on CFD simulation results of the axial-flow blood pump

Computational fluid dynamics is an essential tool for the flow field analysis of the blood pump. The interface processing method between the dynamic/static regions will affect the accuracy of simulation results, but its influence on the simulation results is still unclear. In this study, the axial-flow blood pump was taken as the research object, and the effects of the mixing plane, frozen rotor, and sliding mesh methods on the following results were compared: flux conservation at the interface, hydraulic characteristics, and velocity field distribution. In parallel, the particle image velocimetry experiment was carried out to measure the velocity field of the impeller, the inlet, and the outlet area of the blood pump. The results show that the above methods have significant differences in flux conservation between the impeller and the back vane. The average surface energy flux’s error of frozen rotor and sliding mesh are 0.7% and 0.72%, respectively, while the mixing plane method reaches 3.6%. This nonconservative transfer affects the distribution of the downstream velocity field, and the velocity field predicted by the mixing plane at the outlet is quite different. It is suggested to use the frozen rotor method and the sliding mesh method in the simulation of the blood pump.