A New Magnetic Sealless Coupling Axial Flow Blood Pump

For rotating blood pump, the sealing problem is a very important one to solve. In this paper, it was introduced that we designed and made a small axial flow pump, applying the magnetic coupling method. The pump consisted of two pump housings, a brushless DC motor, an impeller with five wanes, a pair of magnetic discs, a spacer, an inlet and an outlet areas , bearings, a support frame, and etc. The pump is made of titanium and is 125 mm length, 147 ml volume, total 380g of weight. Performances of outputting, sealing, heat creating and damage to blood by the pump were investigated in vitro experiment. Results showed for external experiment that: (1)The pressure created by the pump was 90 mmHg, the flow rates were 1.2 L/min, 4 L/min, 5.9 L/min and 7.8 L/min correspondingly to 5000 rpm, 6000 rpm, 7000 rpm and 8000rpm rotation speeds. The hydrodynamic performance of the axial flow blood pump was enough to meet a patient need when the blood pump was used as a left ventricular assistant device. (2)The hemolysis test was studied by the normalized index of hemolysis(NIH). The NIH result of the axial flow pump was 0.08 g/100 L. (3)The outside temperature of the pump didnt change obviously in 120 hours of rotation, and the sealing function was very well.

Numerical Analyses of Idealized Total Cavopulmonary Connection Physiologies with Single and Bilateral Superior Vena Cava Assisted by an Axial Blood Pump

Our study evaluated the hemodynamic performance of an axial flow blood pump surgically implanted in idealized total cavopulmonary connection(TCPC)models.This blood pump was designed to augment pressure from the inferior vena cava(IVC)to the pulmonary circulation.Two Fontan procedures with single and bilateral superior vena cava(SVC)were compared to fit the mechanical supported TCPC physiologies.Computational fluid dynamics(CFD)analyses of two Pump-TCPC models were performed in the analyses.Pressure-flow characteristics,energy efficiency,fluid streamlines,hemolysis and thrombosis analyses were implemented.Numerical simulations indicate that the pump produces pressure generations of 1 mm to 24 mm Hg for rotational speeds ranging from 2000 RPM to 5000 RPM and flow rates of 2 LPM to 4 LPM.Two surgical models incorporated with the pump were found to be insignificant in pressure augmentation and energy boost.The risk assessment of blood trauma and thrombosis generation was evaluated representatively through blood damage index(BDI),particle resident time(PRT)and relative resistant time(RRT).The hemolysis and thrombosis analyses declare the advantage of the pump supported bilateral SVC surgical scheme in balancing flow distribution and reducing the risk of endothelial cell destruction and trauma generation.

Numerical Investigation of an Idealized Total Cavopulmonary Connection Physiology Assisted by the Axial Blood Pump With and Without Diffuser

In order to improve the surgical treatment of the congenital heart disease patient with single ventricle defect,two axial flow blood pumps,one with diffuser and the other without diffuser,were designed and virtually implanted into an idealized total cavopulmonary connection(TCPC)model to form two types of Pump-TCPC physiological structure.Computational fluid dynamics(CFD)simulationswere performed to analyze the variations of the hemodynamic characteristics,such as flow field,wall shear stress(WSS),oscillatory shear index(OSI),relative residence time(RRT),between the two Pump-TCPC models.Numerical results indicate that the Pump-TCPC with diffuser has better flow field stability,less damage on endothelial cell of vessel wall,and lower risk of vascular injury and thrombosis formation than that without diffuser.

主动脉穿刺型轴流血泵折边结构叶轮的数值模拟及溶血分析

为解决血泵因叶顶间隙泄漏而造成溶血和血栓等问题,引入了一种折边不等间距叶轮,采用计算流体力学(computational fluid dynamics, CFD)进行内部流场的数值模拟,并与非折边不等间距叶轮及折边等间距叶轮进行对比分析,研究了它们的内流场动力学特性和血液相容性.结果表明:折边叶片结构血泵避免了叶顶间隙泄漏流的产生,同时折边不等间距叶轮减少了叶轮入口和出口处的回流和涡流,流道内整体切应力低于其他2种叶轮;3种叶轮的溶血指数HI均满足血泵的溶血设计指标,其中,折边不等间距叶轮血泵壁面切应力在0~150 Pa的占比达96.84%,曝光时间相对集中且满足人工血泵设计要求,溶血指数较非折边不等间距叶轮血泵下降了3.50%,较折边等间距叶轮血泵下降了12.50%,溶血性能最优.提出的折边不等间距叶轮血泵可有效降低红细胞破损概率,减少溶血和血栓的发生,可为轴流血泵的结构设计和优化提供一定参考.

APPLICATIONS OF CFD TECHNIQUE IN THE DESIGN AND FLOW ANALYSIS OF IMPLANTABLE AXIAL FLOW BLOOD PUMP

Based on established numerical methods and hydrodynamic performance testing facilities,CFD technique are applied to improve the design of the implantable axial flow blood pump and the flow analysis.（1） Applying brushless machine magnet steel,reducing its thickness while increasing the length,the flow channel＇s cross-section is increased,with no space connection between the large and the small rotators,and with a cone transition segment from the bearing to the principal axis,the flow is made smoother.The rotating speed is lowered by 1000 rpm-1200 rpm under the same flow rate and pressure head,and thus the hemolysis can be avoided.（2） Different outlet stator guiding vanes are selected for the same blood pump for analyses of hydrodynamic performances and flow fields.An excellent design not only can regulate the rotating flow field into an axial one,reduce the circulation loss and improve the pump efficiency,but also can avoid backflow,vortex and secondary flow at the pump outlet,and thus the thrombus can be prevented.（3） The calf live tests show that some residual clots exist at the inner wall of the outlet connection bends,which are analyzed and explained by CFD techniques and the corresponding improvements are proposed.All results are verified by hydrodynamic performance tests and PIV flow field tests,and consistent conclusions are obtained.

DESIGN OF IMPLANTABLE AXIAL-FLOW BLOOD PUMP AND NUMERICAL STUDIES ON ITS PERFORMANCE

This article presents the design of a new implantable axial-flow blood pump. The special feature of the flow channel inside the blood pump is that the blood is driven by a big-small tandem impeller installed in the inner hole of the cylinder magnet of a brushless direct current motor. The inner hole makes the main flow channel possible, while the gap between the inner end of the stator and the outer end of the cylinder magnet gives the shape of the tributary flow channel. There is no motor magnet inside the main flow channel, therefore, more blood can pass through it. The gap of the tributary flow channel is very small, but the blood flow in it is not blocked. Thus, the efficiency is increased and the volume and weight of blood pump can be reduced greatly. The outer diameter, length and weight of the manufactured implantable axial-flow blood pump are 29.6 mm, 76 mm and 158 g, respectively. The impeller spins at the speed of 9000 rpm and can generate a pressure head of 100 mmHg and a flow rate of 8 L/rain. In an animal experiment, the blood pump has been successfully applied as a Ventricular Assist Device （VAD） in the chest of a small cow. Besides a mathematical model is established to simulate the flow inside an axial-flow blood pump of implantable VAD. The numerical studies on the performance of the implantable axial-flow blood pump are carried out by combining this mathematical model and the Fluent software. The numerical results agree well with those of experiments, with the maximum error less than 10%.

Ⅱ型叶片轴流血泵的研制及体外流量实验

在自制Ⅰ型离心血泵和借鉴国外同类血泵的基础上 ,我们通过改变泵的整体结构、叶片角度、材料、密封方式和加工手段等 ,又自行设计和加工另一微型轴流血泵 -Ⅱ型血泵 ,它由泵体、直流无刷电机、叶轮、一对磁片、导流槽和支撑架等部件构成 ,总长度 12 5mm ,容积 147ml,材料是TC4钛合金 ,总重量 380g。我们根据不同的压力、流量输出要求 ,设计、加工出五、四、三叶片的叶轮。在模拟试验台 ,我们分别测试此泵的动力学输出、产热和密封性能。结果显示 :(1)五叶片泵在 80 0 0rpm时输出为 6 .8L/min、12 0mmHg ;根据各叶片泵的输出曲线得出 :五、四、三叶片泵的压力和流量均随着转速的升高而升高。 (2 )当前负荷为 0mmHg时 ,五、四、三叶片血泵转速80 0 0rpm流量为 5 .0L/min时 ,所对应的最大的压力约为 170mmHg、16 0mmHg和 130mmHg ,可见在同流量输出情况下 ,随着叶片数的减少压力随之降低。 (3)五、四、三叶片泵的流量、压力输出受前负荷影响较小。 (4 )血泵的效率随着转速的升高而升高。 (5 )在 12 0h的连续运转过程中 ,血泵的表面温度变化较小 ;密封性能也较好。

轴流式磁悬浮血泵流场数值模拟及溶血预测

血泵流体动力分析是研发先进人工心脏泵的前提,血泵叶轮旋转时会对血细胞造成不同程度的机械损伤,从而导致溶血和血栓,严重时甚至危及患者生命。以设计的一种轴流式磁悬浮血泵为例,结合计算流体力学和结构优化设计,采用κ-ε模型、动网格技术和用户自定义函数技术,在轴流式磁悬浮血泵内部三维流场数值模拟的基础上,分析轴流式磁悬浮血泵流道的剪应力分布,探索血液流量与叶轮转速的关系,利用粒子追踪法获取血液细胞流动轨迹,建立一种轴流式磁悬浮血泵的溶血数学模型,阐述轴流式磁悬浮血泵溶血性能预测的方法和机理。研究结果可为轴流式磁悬浮血泵的结构设计和降低溶血提供重要依据。

植入式轴流血泵CFD仿真研究

近年来,血泵的研究已成为心脏外科和生物医学工程领域关注的焦点,对血泵中血液流动进行流体动力学仿真分析已忧为一种快速、经济的设计手段。本文针对所设计的微型轴流血泵,采用CFD技术,对血泵中的速度、压力、应力等分布进行了仿真分析。研究结果表明血泵中的流体具有非常复杂的流动情况,为了避免流动分离、压力变化过大等情况,减少剪切应力,对血泵叶轮结构提出了相应的改进意见。

轴流血泵叶轮结构CFD仿真优化研究

轴流血泵内部流场形态产生的高剪切力是导致血液溶血的重要因素,因此,对轴流血泵中血液的流体动力分析有助于血泵性能的优化及减少血液细胞的损伤。应用计算机求解RNGk-ε方程,对所设计的微型轴流血泵叶轮中血液的流线及速度、压力、应力等分布情况进行了仿真分析。研究结果表明:血泵中的流体具有非常复杂的流动情况,为了避免流动分离、压力变化过大等情况,减少切应力,对血泵叶轮结构提出了相应的改进意见,并给出了优化后的叶轮结构。

基于外磁场耦合的血泵驱动系统

基于横向旋转磁场的耦合原理,提出轴流式血泵外磁场驱动系统方案,设计一种泵机分离的结构。采用等效电流法建立了永磁体等效物理模型,计算血泵驱动系统的主动轮和从动轮之间的距离、相对转角以及磁极对数对血泵传动扭矩的影响。研究结果表明:在生理范围内,即主动轮与从动轮的安装距离小于60mm,设计的永磁体输出的扭矩大于血泵需要的扭矩(6.4N-mm),能够满足血泵的驱动要求。主动轮与从动轮的磁极对数是影响血泵系统性能的关键参数,主动轮与从动轮磁极对数越少,传动扭矩越大,但是扭矩波动也大;主动轮的磁极对数大于从动轮的磁极对数,驱动系统传动平稳,对控制有利。

两级轴流血泵CFD性能仿真

为了降低血泵转速,提高其溶血性能,将血泵设计为两级轴流式结构,其中前级叶轮采用一元流动理论设计为螺旋轴流结构,后级叶轮采用流线法设计为传统轴流结构。利用计算流体力学(CFD)的方法,对血泵的扬程、流量及其内部血液的流场、应力等分布情况进行了仿真分析。结果表明:血泵最大应力主要出现在其入口和出口处,且后级叶轮在前级叶轮的影响下,其入口处的最大应力明显减小。在相同条件下,两级血泵与普通血泵相比,其最大应力可明显降低。

大间隙磁力传动系统能量传递效率

为了解大间隙、高转速条件下磁力传动系统的能量传递规律,研究行波磁场驱动的大间隙磁力驱动技术;通过微型轴流式血泵外磁场驱动,对大间隙磁力驱动系统各部分能量耗散进行研究,建立系统能量传递效率的数学模型。通过轴流式血泵泵水实验,得到血泵在耦合距离20 mm和30 mm时的最大能量传递效率,即磁力传动系统的最佳工作点,并通过与理论解析值相比较,得到大间隙磁力驱动系统的能量传递效率的变化趋势,确定磁力驱动系统能量传递效率的主要影响因素,为提高磁力驱动系统的能量传递效率提供了途径和依据。

XZ-ⅡA型轴流血泵的研制及体外流体实验

在自制XA Ⅱ型轴流血泵的基础上 ,结合计算机辅助设计 (computer aideddesign ,CAD)以及计算机流场分析 (computationalfluiddynamics ,CFD) ,通过改变泵的结构、叶片螺距、密封方式、材料加工手段自行研制和加工出一款微型轴流血泵XA ⅡA型血泵。它由泵体、直流无刷电机、钛合金叶轮、陶瓷轴承等部件构成 ,材料TC4钛合金 ,总重量 2 4 5g。在体外流量实验中 ,分别测量血泵的动力学输出、流量输出要求、产热以及密封性能。结果显示XA ⅡA型血泵能够满足设计的要求 ,在 12 0h连续运转过程中 ,血泵表面温度变化较小 ,而且密封性能很好。

某轴流式血液泵的实验与改进设计

原型血液泵LAP-00的数值模拟及实验结果表明，在设计转速9000r／min下，最大效率点对应的设计点流量为11L／min，远大于临床所需3-8L／min的流量，致使血液泵在实际应用时效率偏低；而静子区域存在的流动分离与回流，极易造成血流停滞进而引发血栓。改进后的血液泵LAP-23，将设计转速从9000r／min降低至8000r／min，减小了转子叶尖切应力对血细胞的破坏；设计点流量降低至6L／min，并消除了静子区域内的分离和回流。

轴流式血泵流体特性CFD研究

在轴流式血泵的研发中,通常将血液当作牛顿流体来处理,考虑到当动脉存在局部狭窄等几何突变情况时,动脉局部流场中可能产生流动剪切率非常低的区域,因此有必要考虑血液的非牛顿特性.建立了轴流式血泵模型,通过CFD仿真分析得到血泵转速和流量的变化对血泵出入口流场的影响,以及血泵导叶对泵体内流场的影响规律,并通过对设计的血泵进行泵水实验,测量了轴流式血泵输出流量和压力参数.结果表明所设计的血泵在驱动性能上和仿真是相符的.

微型轴流血泵溶血的数值模拟

基于N-S方程和标准K-ε湍流模型,采用非结构网格技术,对微型轴流血泵内部三维流场进行了数值模拟,得到了速度场、压力场等流场细节;同时采用Lagrange粒子追踪法获得了沿不同流线的剪应力以及红细胞暴露接触时间的分布,并引入溶血计算的经验公式,计算对比了不同转速条件下血泵的溶血指标,重点分析了血泵在5L/min、8000r/min工况下的溶血性能,对于血泵溶血的估算,本方法是可行的。

轴流血泵最佳左心辅助下的速度变化及内流场分析

为解决轴流血泵恒压或恒转速辅助时产生的抽吸或反流现象,以自主研发的主动脉瓣轴流血泵为研究对象,建立“轴流血泵-血液循环系统”串联耦合多尺度参数模型,得到血泵变转速辅助时在各级心衰条件下达到最佳辅助状态时的转速变化曲线.相比恒转速辅助,变转速辅助的血流动力学结果与正常心脏的拟合度更高,也符合人体生理.采用CFD技术对Ⅳ级心衰下2种辅助状态在1个心动周期中的内流场进行比较分析,发现变转速辅助下,轴流血泵在等容收缩期、等容舒张期、充盈期会产生明显的涡流,过流时间较长,但剪切应力较小,不会造成溶血;在射血期,变转速辅助的流动更加稳定,没有涡流现象产生,但其剪切应力在0.10 s内高于临界值500 Pa,会产生溶血现象.

磁极位置对永磁轴流式血泵驱动能力影响的研究

为提高永磁轴流式血泵的驱动能力,利用ANSYS有限元分析软件仿真计算了大间隙磁力驱动系统的驱动力矩,通过实验计算了永磁轴流式血泵的最大负载力矩,得到了磁极相对位置(系统耦合距离、两电磁体间磁极距离、永磁体偏离两电磁体中心位置的距离、两电磁体间的相对夹角等)对系统驱动能力的影响。结果表明:通过减小系统耦合距离,减小两电磁体间磁极距离,将永磁体置于偏离电磁体中心位置8 mm左右的位置,将两电磁体垂直放置等方法,可以提高系统驱动能力。