Optimized Design And Evaluation Of A Novel Injection Syspension Blood Pump

Heart failure has become one of the biggest threats to human health.Ventricular assist device(VAD)has become an important treatment for end-stage heart failure patients.The trend for VAD development nowadays is the third-generation VADs with suspended impellers,which imply either hydrodynamic or magnetic suspension methods to levitate the rotor.The elimination of mechanical contact bearing could prevent mechanical wearing and heat generation,which can help to improve the safety,reliability and lifespan of VADs.However,there are still problems need to be solved.Due to the limitation of the lubrication theory,the gaps of the hydrodynamic bearings need to be around 100 ?m or less.High shear stress would occur in such narrow gaps,which could damage blood cells.As the magnetic suspension system occupies a bigger space,complicated active control system and extra energy consumption,it would affect the safety,reliability and endurance of the blood pump.These problems all limit the development of VADs.This thesis aims to development a novel injection suspension method which could be applied in VADs.The principle of the method was theoretically analyzed.A prototype blood pump model was built and evaluated.The geometric parameters of the blood pump was optimized and evaluated.The double-inlet design was also applied in blood pump design.The specific research includes:(1)Aimed at solving the challenges faced by existed rotor levitation technology,namely extra energy consumption and complex control system of the maglev system,and blood trauma caused by high shear stress of the hydrodynamic levitating method,the theory and design of the injection suspension method applied in the blood pump design were studied in this paper.The principle of the injection suspension method was analyzed,which built the theoretic foundation of the research.According to the demand of human circulation,the parameters of a centrifugal blood pump were calculated,and the pump was designed and modeled.The injection suspension method was then applied in the pump design.Finally a prototype of an injection suspension blood pump was built,which was passively controlled and has a bigger gap.(2)Aimed at optimizing the injection suspension blood pump,an evaluation system was established which could assess both the suspension property and the hemocompatibility of the blood pump.The blood pump could then be evaluated both qualitatively and quantitatively.The flow field of the injection suspension blood pump was calculated and evaluated using computational fluid dynamics(CFD)methods.The nominal working point of the pump was then chosen according to the calculated hydraulic curves.At the nominal working point,the levitation forces on the rotor at different positions were calculated to evaluate the suspension property of the pump.A prototype pump was manufactured for experiment,which validated the accuracy of the calculation.The minimum gap between the rotor and the pump casing was also measured to validate the rotor suspension method.According to the theory of blood cell damage due to shear stress,thresholds of shear stress were set for different types of blood damage.A qualitative investigation was then conducted accordingly.A power-law method and the Lagrangian approach were combined to quantitatively evaluate the hemolysis of the pump.Blood damage was integrated along pathlines to calculate the hemolysis index of the pump.The influence of the injection flow on hemocompatibility was then discussed.The blade outlet angle,injection channel outlet angle and the width of the blade were chosen as geometric parameters in the optimization process.The relationship between the three parameters and the pump properties was then revealed using CFD methods.An optimized blood pump was accordingly modeled.The suspension property and hemocompatibility of the optimized pump model were calculated and compared with the initial blood pump,which proved the effectiveness of the optimization.The accuracy of the calculation was validated through experiments.(3)Aimed at balancing the axial thrust force occurred in single-suction blood pump,the double-suction structure was applied in the blood pump design,and its feasibility,advantages and disadvantages were discussed.A double-suction injection suspension blood pump was designed and modeled.The flow field of the pump was calculated and compared with that of the previous single-suction pump.It is concluded that the axial thrust force on the rotor of the double-suction pump was auto-balanced due to its axially symmetric structure.It is revealed that the hemocompatibility of the double-suction pump was superior to that of the single-suction pump at the same nominal working point using qualitative analysis methods.The hemolysis indices of the two pumps were also calculated which proved a better hemolysis property of the double-suction design.Overall,this thesis focused on the problems occurred in current suspension methods applied by VADs.It aims to develop a novel suspension method to overcome those problems.A blood pump using the novel injection suspension methods was design and modeled.The suspension property and hemocompatibility of the pump were evaluated using CFD and experimental methods.The properties of the blood pump were improved with optimization of geometric parameters.The feasibility of applying double-suction structure to blood pump design was also studied.This paper provides theoretic guidance and technical support to future blood pump development.