Design And Performance Analysis Of A New Nutation Ventricular Auxiliary Pump With Magnetic Driving And Levitation

Heart failure is one of the most fatal diseases in the 21 st century.One of the effective therapies for the patients is to pump blood by ventricular assistance device.Artificial heart pump is a core component of the ventricular assistance device,and Its pumping performance and hemolysis resistance are crucial for long-term working of ventricular assistance device.At present,most of the continuous-flow ventricular auxiliary pumps work with a high rotor speed(about 10000 r/min)which is prone to hemolysis.Based on the nutation principle,our research team designed a new nutation ventricular auxiliary pump with magnetic driving and levitation(hereinafter referred to as nutation pump)driven and supported by magnetic force,with a speed of 1450r/min.The magnetic driving is used instead of the direct driving of the motor,eliminating the wear and heat generated by the mechanical driving.The design of the magnetic levitation balances the gravity of the nutation disk,which reduces the wear on the pump body in working.The principle of the nutation is applied to the motion of the nutation disk,and the theoretical calculation formula of the internal flow of the nutation pump is derived.The nutation disk is driven by magnetic force.The magnetic levitation structure is formed by the corresponding magnets placed on the ball’s deputy of nutation disk and the upper and lower covers.On this basis,the overall design of structure and size for nutation pump is carried out.By analyzing the force on the nutation disk,the requirement of the driving magnetic moment MT for driving the nutation disk to perform the nutation motion is obtained.The calculation formula of the magnetic moment between the nutating disk and the driving magnet is obtained by using the magnetic calculation model in literature.The detailed calculation is performed by MATLAB codes.The dimensional parameters and relative position between the driving magnet and the nutation disk magnet are obtained by comparing the calculation results with the requirements mentional above.The COMSOL Multiphysics software is used to simulate the three-dimensional dynamic magnetic field between the driving magnet and the nutation disk magnet,and the variation of the driving magnetic moment MT in a cycle.The simulation results are compared with the theoretical one as a validation.Taking the residual magnetic flux density Br of the magnet as a variable,the three-dimensional dynamic analysis of the magnetic levitation structure is carried out,and the optimal residual magnetic flux density is selected by balancing the gravity of the moving parts.The non-Newtonian fluid characteristics of the blood are analyzed,and the motion formula of the nutation disk is derived,the non-Newtonian fluid model of the blood and the boundary motion of the nutation disk is incorporated into the Fluent software by User Defined Functions.The dynamic simulations of the flow field inside the nutating pump are carried out.The inlet and outlet pressure difference and the motor speed are varied in simulations to analyze the flow changes of the inlet and outlet of the nutation pump to verify the pumping performance of the nutation pump.The velocity field,distribute of pressure and shear stress are investigated to verify the hemolysis resistance of the nutation pump.