| Heart failure is one of the considerable reasons of death in heart disease, more attentions of cardiovascular medicine and surgey have been taking to solve the diffcult problem——the treatments of terminal heart failure. Heart support devices have been developing rapidly because of the limitation of medical therapy and surgery and the shortage of donor heart. Artificial heart helps or replaces nature heart to pump blood by a micro mechanic pump. Micro-axial blood pump has been the research hotspot of artificial heart for the advantages, including simple structure, small in size and easy to implant.There are a couple of factors that give rise to hemolysis and thrombus when blood flows through the blood pump. Therefore, it has important significance in the using of artificial heart in medical field to study the flowing situation of blood in the pump.This article designs a new axial blood pump based on traditional axial blood pump design theory, established a numerical simulation method with RNG κ-ε turbulence model acting as the flow field in blood pump. CFD software has been used in the numerical simulation of the three dimensional incompressible flow field in the blood pump. And the simulation shows the pressure, velocity, shear stress and turbulence effects. This article has analyzed some areas that hemolysis and thrombus easy to appear, and improved the structure of blood pump based on the analysis.The analysis shows that:(1) The flow output performance of the improved blood pump gets an improvement compared with the original one, it is able to meet the requirement of 6L/min flow output and 100mmHg afterload pressure output for human body at low revolving speed.(2) In the blood pump, higher pressure and shear stress appear near the rotating impeller and the entrance of diffuser. After the optimization, the maximum flow field pressure and shear stress have a decrease compared with the original pump, and pressure gradient is more uniform.(3) Blood flow quickly in the area near the impeller in original blood pump, but the flow velocity of blood is lower in the improved pump, the improved pump reduces the flow velocity of blood by 9.5 percentage points.(4) Higher turbulent kinetic energy and turbulent kinetic energy dissipation rate appear at the area near pump impeller and the border of diffuser, after the improvement, the turbulent kinetic energy is lower, but there is no significant improvement in turbulent kinetic energy dissipation rate.(5) In the traditional blood pump, obvious flow stagnation appear at the area near the diversion-cone, after optimization, the flowing situation of blood has been improved to avoid the formation of thrombus caused by flow stagnation.The following conclusion is obtained:compared with the original blood pump, the probability for hemolysis and thrombus formation is lower in improved blood pump. |
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