Design Aspects of a Cardiac Action Hydraulic Pump

This paper presents some design aspects of a high pressure cardiac action hydraulic pump consisting of several pumping heads. Each head has a set of followers that completely encircle a cam. The followers separate a pumping chamber, formed between the cam and the followers, from a control chamber existing outside the followers. With the cam rotation the followers move outwards and inwards with respect to the cam, causing the pumping chamber volume to increase and decrease to suck and pump oil. The pump geometric volume can be controlled by controlling the stroke of the followers through the control of the oil volume in the control chamber. Three different methods are proposed to transmit the motion from the cam to the followers. In the first method the followers are in direct contact with the cam, while in the second intermediate cylindrical rollers are inserted between the followers and the cam. In the third method, specially shaped pads are inserted between the cam and the followers. Finite element analysis (FEA) using ANSYS Mechanical software is carried out to compare between these methods regarding the generated contact stresses between the cam and the followers. FEA is also utilized to design a self-integrated priming spring in the external lips of the followers in order to allow smooth pump start up at all operating conditions. The suction and delivery valves of this pump are crucial for its reliability and high performance. They should allow high flow rates at small pressure drop and should be compact, of low inertia to operate at high frequency, and of minimum deformation under high pressures. A CFD analysis for a proposed design for these valves is performed using ANSYS/FLUENT program on three-dimensional models, where the flow rates, the pressure and velocity distributions, and the deformations of these elements are calculated.