Analysis Of Internal Flow Characteristics And Blood Damage In Centrifugal Blood Pump

With the acceleration of the aging society and urbanization,the risk factors for cardiovascular failure in the residents of China are generally exposed.Therefore,the blood pumps have been widely used for patients with end-stage heart failure.However,the complex flow field in the blood pump is three-dimensional,viscous and rotating,is a,which is prone to hemolysis and thrombosis during operation.It often directly affects the life safety of patients.The study on the internal flow characteristics of the blood pump is helpful to solve the problem of blood damage,and it is of great significance to promote the development of artificial heart.In this paper,the theoretical analysis,experimental research and numerical simulation are combined to study the flow characteristics and blood injury inside the centrifugal blood pump.Based on the principle of bionics,the structure of impeller blade is optimized.The conclusions can be drawn as follows:(1)Flow characteristics of the centrifugal blood pump under steady state condition were studied.At the same flow rate,the wall pressure of the volute at low speed is lower than that at high speed,and with the increase of flow rate,the wall pressure of the volute increases gradually along the flow direction.There is a low-pressure area at the exit of the blade back,which results in the increase of flow velocity in other areas of the impeller channel.When the rotating speed is the same,the wall shear stress at the blade outlet increases with the increase of flow rate;when the flow rate is the same,the wall shear stress at the blade outlet increases with the increase of rotating speed.(2)Flow characteristics of centrifugal blood pump under unsteady condition during cardiac cycle were studied.During a cardiac cycle,when the inlet flow increases,the head of the blood pump decreases,and when the inlet flow decreases,the head of the blood pump rises.The head of the blood pump with high speed is higher than that at low speed.The pressure increment at low speed is lower than that at high speed,and at low speed is less than that at high speed,the maximum flow velocity at low speed is 6.1 m/s when the blood pump runs smoothly and at high speed is 8.7 m/s when the blood pump runs smoothly.The shearstress on the impeller blade wall at high speed is higher than that at low speed.The shear stress on the front end of impeller blade is lower.The distribution range of high shear stress is mainly concentrated at the tail of blade.The shear stress at the monitoring point at high speed is obviously higher than that at the corresponding monitoring point at low speed,and the shear stress at the tongue separator is higher than that at the monitoring point near the blade outlet.(3)The blood damage of centrifugal blood pump under different working conditions was studied.Based on DPM discretization model,the flow and stress of red blood cells in centrifugal blood pumps are simulated by releasing particles from the inlet.It is found that the shear stress of red blood cells is the lowest and the exposure time is medium under the conditions of low flow rate and high speed,so the hemolysis value and thrombosis value of red blood cells are the lowest.Under the conditions of high flow rate and low rotational speed,the shear stress of erythrocyte is high and the exposure time is long,which results in the highest hemolysis and thrombosis value of erythrocyte under the combined action.The shear stress of erythrocyte is the highest under high flow rate and high rotational speed,but the action time on erythrocyte is short,so the hemolysis value and thrombosis value of erythrocyte are high.(4)The influence of blade structure on flow characteristics of centrifugal blood pump was studied.Based on the principle of bionics,the structure of impeller blade was optimized,and its influence on velocity field and wall shear stress of centrifugal blood pump impeller was studied.Compared with the results of the original model,the non-smooth element reduces the wall shear stress of the blade and volute,changes the velocity distribution near the wall,reduces the velocity gradient near the wall,reduces the Reynolds stress near the wall,and reduces the wall viscous resistance.The research results obtained in this paper provide some significant guidance for the optimizing design of the impeller and avoiding the hemolysis.