IMPROVEMENT AND EVALUATION OF AN ENCLOSED-IMPELLER TYPE AXIAL FLOW BLOOD PUMP WITH HYDRODYNAMIC CONICAL BEARINGS

Abstract

The main purpose of this study is to develop the enclosed-impeller type axial flow blood pump that enables an enclosed-impeller to be levitated using hydrodynamic conical bearings. This time we report on improvements including the miniaturization and the results of in vitro experiments. The enclosed-impeller type axial flow blood pump consists of a spindle rotor with the enclosed-impeller, a pump housing, a blushless DC motor stator, a flow straightener and a diffuser. The shape of vane was designed according to a CFD analysis. The enclosed-impeller length is 35 mm, and the diameter is 14 mm. The diameter of the hydrodynamic conical bearing included into the spindle rotor is 15 to 27 mm, the height is 9 mm, the taper angle is 35 degrees, the number of grooves are 11, and the groove depth is 200 μm. The prototype pump length is 109 mm, and the diameter is 60 mm. We performed the levitation and hydraulic performance test by using a mock circulation loop. A glycerol solution was used for the working fluid. The spindle rotor is moved to the inlet side according to the pressure head, so three eddy-current sensors were attached at the inlet side of the pump to measure the levitation distance of the hydrodynamic conical bearing. The levitation distance of about 30 μm was obtained at a rotational speed of 12,000 rpm. A flow rate of 5 L/min at 100 mmHg pressure head was achieved at the rotational speed of about 9,000 rpm. The enclosed-impeller type axial flow blood pump is expected to be applicable in implantable rotary blood pumps.