Studies on Rotating Disc Flow in Narrow Clearance For Low Specific Speed-Small Centrifugal Magnetically suspended Blood Pump

本研究为开发下一代人工心脏磁悬浮叶轮离心血泵的研究课题之一。与传统的工业泵相比，这种泵体积小，血液粘性对泵内流动的影响很大，主要是由于摩擦和护罩间隙泄漏造成的功率损失。因此，本文研究了该间隙内的流动。这就是所谓的“旋转圆盘粘性绕流问题”。以下三个因素影响这种间隙流动：（1）泵进出口压差;（2）转盘产生的离心力;（3）泵I主流产生的射流泵效应。虽然在实际泵中，流体从叶轮的出口侧到入口侧通过护罩间隙泄漏回来，通过对泵壳的一部分进行改造，使泄漏流绕过泵壳，然后测量流量，再返回叶轮进口侧，实验结果表明，在叶轮高转速时，离心效应抑制泄漏，在高主流量时，射流泵效应抑制泄漏。此外，还测量了叶轮外缘和内缘的压力分布作为边界条件。将该叶轮用盲盘代替，并对双蜗壳和无蜗壳（开式出口）的泄漏流进行了比较。这种流动表明了上述两种效应（1）、（2）以及通过螺旋蜗壳的角动量效应。

This study treats with one of research subjects for development of a centrifugal blood pump with magnetically suspended impellers as an artificial heart of next generation. This kind of pump is so small, compared with conventional industrial pumps, that blood viscousity much influences on flows in the pump.Power loss due to friction and leakage in the shroud clearance is dominant. So the flow in this shroud clearance is investigated. This is so called "the problems on viscous flow around rotating disc".The following three factors influence on this clearance flow : (l) pump pressure difference between outlet and inlet, (2) centrifugal force induced by rotating disc, (3) jet pump effect induced by pump I main flow.Though the flow, in the actual pump, leaks back through the shroud clearance from outlet side to inlet side of the impeller, a part of the pump casing is modified to bypass the leak flow, then to measure flow rate and return to the inlet side of the impeller.Experimental results shows the above three effects - leakage is surpressed by centrifugal effects at high rotational speed of impeller and by jet pump effect at high main flow rate. Of cause, leakage depends on pressure difference.In addition, the pressure distributions around outer edge and inner edge of the impeller are measured as the boundary conditions. This impeller was replaced by a blind disc, and the leakage flows were compared with double volute and without volute (open outlet). This flow indicated the above mentioned two effects (l), (2) and the angular momentum effect through spiral volute.