Abstract: A pulsatile axial pump and a pulsatile centrifugal pump are developed. The pulsatile flow of impeller pump is discussed. In the pulsatile axial pump, the impeller reciprocates axially and rotates simultaneously. The reciprocation is driven by a pneumatic device and the rotation by a DC motor. For 5.3 kPa pulsatility of pressure, about 50 mm axial reciprocating amplitude of the impeller is desirable. In order to reduce the axial amplitude, the pump inlet and the impeller both have cone-shaped heads, and the gap between the impeller and the inlet pipe changes only 2 mm, namely, the impeller reciprocates 2 mm, a pressure pulsatility of 5.3 kPa can be produced. As the impeller rotates with constant speed, low turbulence in axial pulsatile pump may be expected. In centrifugal pulsatile pump, the impeller changes its rotating speed periodically, the turbulence is reduced by designing an impeller with twisted vanes which enable the blood flow to change its direction rather than its magnitude during the periodic change of the rotating speed. In this way , a pulsatile flow is produced and the turbulence has been minimized. Compared to the axial pulsatile pump, the centrifugal pulsatile pump needs only one driver and thus has more reality for application. The centrifugal pulsatile pump is used in animal experiments. The pump assisted the circulation of the calves for several months without harm to the blood elements and the organ functions of the experimental animal. The experiments demonstrated furthermore that the pulsatile impeller pump is the most efficient assist pump for heart recovery.

Key words: Axial pump, Centrifugal pump, Hemolysis, Impeller pump, Pulsatile flow, Turbulence shearing stress