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

本研究是研制下一代人工心脏磁悬浮叶轮离心式血泵的研究课题之一。与传统的工业泵相比，这种泵体积很小，血液的粘性对泵内的流动有很大的影响，由于摩擦和盖板间隙泄漏造成的功率损失占主导地位。因此，本文研究了这种导流罩间隙内的流动。这就是所谓的“转盘粘性流动问题”。影响这种间隙流动的因素有三：(L)泵进出口压差，(2)转盘产生的离心力，(3)泵I主流引起的射流泵效应。虽然实际泵中的流量从叶轮的出口侧到进口侧的盖板间隙漏回，但泵壳的一部分被改装以绕过泄漏流动。实验结果表明，当叶轮转速较高时，泄漏受到离心力的抑制，而在主流量较高时，则受到射流泵效应的抑制。当然，泄漏取决于压差。此外，测量了叶轮外缘和内缘周围的压力分布作为边界条件。将该叶轮更换为盲盘，并与双蜗壳和无蜗壳(开口出口)的泄漏量进行了比较。这一流动表明了上述两种效应(L)，(2)和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.