具有分流和悬臂叶片尾导的轴流血泵设计分析

Design of an axial blood pump of diffuser with splitter blades and cantilevered main blades

根据中国终末期心衰患者对左心辅助泵辅助人体血液循环的要求,设计以3L/min流量、100mmHg压升为设计点,流量范围为2~7L/min的微型可植入轴流血泵。该血泵采用纺锤形的转子叶轮结构以及带分流叶片、悬臂叶片的尾导结构,以使血泵在较宽的压力流量范围内具有良好的溶血和抗血栓特性。本文用数值模拟及粒子成像测速(PIV)的方法分析血泵的水力学特性、流场及溶血特性。结果表明:血泵转速为7000~11000r/min时,在2~7L/min的流量范围内可提供60.0~151.3mmHg的压升;分流叶片抑制了尾导的尾缘吸力面处的流动分离;悬臂式叶片结构将转子叶片的叶尖间隙变为尾导叶片的叶根间隙,间隙的切线速度由6.2m/s降至4.3~1.1m/s;血泵的最大标量剪切应力值为897.3Pa,平均剪切应力值为37.7Pa;采用Heuser溶血模型得到的溶血指数为0.168%;PIV试验所得泵内尾导区域的流场速度分布与数值计算得到的流场特征吻合良好。本研究所设计的轴流血泵的尾导具有分流叶片和悬臂叶片,流道内血流无较大分离流动,降低了剪切力对血液的破坏,溶血性能良好,压力流量性能满足临床需要。

An implantable axial blood pump was designed according to the circulation assist requirement of severe heart failure patients of China.The design point was chosen at 3 L/min flow rate with 100 mm Hg pressure rise when the blood pump can provide flow rates of 2-7 L/min.The blood pump with good hemolytic and anti-thrombogenic property at widely operating range was designed by developing a structure that including the spindly rotor impeller structure and the diffuser with splitter blades and cantilevered main blades.Numerical simulation and particle image velocimetry(PIV)experiment were conducted to analyze the hydraulic,flow fields and hemolytic performance of the blood pump.The results showed that the blood pump could provide flow rates of 2-7 L/min with pressure rise of 60.0-151.3 mm Hg when the blood pump rotating from 7 000 to 11 000 r/min.After adding the splitter blades,the separation flow at the suction surface of the diffuser has been reduced efficiently.The cantilever structure changed the blade gap from shroud to hub that reduced the tangential velocity from 6.2 m/s to 4.3-1.1 m/s in blade gap.Moreover,the maximum scalar shear stress of the blood pump was 897.3 Pa,and the averaged scalar shear stress was 37.7 Pa.The hemolysis index of the blood pump was 0.168%calculated with Heuser’s hemolysis model.The PIV and simulated results showed the overall agreement of flow field distribution in diffuser region.The blood damage caused by higher shear stress would be reduced by adopting the spindle rotor impeller and diffuser with splitter blades and cantilevered main blades.The blood could flow smoothly through the axial blood pump with satisfactory hydraulics performance and without separation flow.