| At present,for the patients with end-stage heart failure,the method of blood pump transplantation can be used to cure when drug treatment does not work well.However,the blood pump is easily to cause hemolysis and thrombus in the work,which is seriously restricts the practical application of the blood pump.There are some problems exist in the study of blood pump performance,such as the difficulty of measuring the flow field,the high cost of the experiment and the interference of external factors.By using the CFD(Computational Fluid Dynamics)method can obtain the flow characteristics of the flow field directly and get the blood damage degree of the blood pump.Therefore,this study will use CFD technology to study the hydraulic performance and blood damage of blood pump and provide a theoretical basis for the structural optimization and clinical application of blood pump.Firstly,the working principle is introduced according to the structure of centrifugal blood pump,describes the blood damage phenomena which is can be caused in the operation of blood pump and analyzes the effects of shear stress and exposure time on blood damage.In order to simulate the blood flow process and calculate the damage of blood pump to blood,this paper use the standard k-?turbulence model and blood damage prediction model combined with the method of Lagrange to simulate flow process of blood pump and calculate blood cell damage degree.The blood pump model is established in the SolidWorks and the model is pretreated by Gambit.The motion reference frame model is used to simulate the relative motion between the impeller and the pump shell and then the flow field is calculated by Fluent software.Secondly,the flow field of the blood pump in the design condition is analyzed and the damage degree of blood is determined in this paper.This paper also simulates the flow field of blood pump under different working conditions,obtainsthe H-Q curve of blood pump and analyzes the effect of impeller speed on the blood pump's pressure head as well.Based on the size of blood pump head pressure and the principle of blood damage,the impeller model with different structural parameters is simulated and the optimal impeller structure is determined.This paper also studies the effect of the gap between the impeller and the pump shell on the blood damage and the suspension position of impeller with minimal damage to blood is determined.Thirdly,the blood pump entrance flow fluctuation will have a huge impact on the flow field.In this paper,the variation of velocity and pressure field in the blood pump flow field at different time is studied by using the flow fluctuation in a human cardiac cycle as the inlet boundary condition of blood pump and get the pressure changes with the fluctuation of flow at the gap between the impeller and the pump shell.This paper analyzes the axis force on the impeller with the flow fluctuation in the secondary flow channel.The characteristics of the flow field of the blood pump with flow fluctuation of inlet and the start-up in the form of linear acceleration is studied and the phenomena of vortex and turbulence in the flow field is analyzed.This paper also studies the effect of irregular blood flow on the formation of thrombus.Finally,measurement platform of the blood pump hydraulic characteristics is set up,and the pressure head is measured under different working conditions.The actual H-Q curve of blood pump is got and the actual pressure head is in the range of20~136mmHg.The result shows that the blood pump can well meet the need of pumping blood for the patients with heart failure.Compared with the actual measured H-Q curve,the results show that the simulation results can better predict the hydraulic characteristics of the pump. |
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