Application of CFD in the Design and Analysis of a Piezoelectric Hydraulic Pump

Smart materials' ability to deliver large block forces in a small package while operating at high frequencies makes them extremely attractive for converting electrical to mechanical power. This has led to the development of hybrid actuators consisting of co-located smart material actuated pumps and hydraulic cylinders that are connected by a set of fast-acting valves. The overall success of the hybrid concept hinges on the effectiveness of the coupling between the smart material and the fluid. This, in turn, is strongly dependent on the resistance to fluid flow in the device. This paper presents the results of two and three dimensional simulations of fluid flow in a prototpype hybrid actuator being developed for aerospace applications. The steady simulations show that losses in the device result primarily from three dimensional effects and that two dimensional approaches can underestimate losses by approximately a factor of 40. The effects of varying design parameters like the pumping chamber height, discharge port location, and discharge port chamfer are also explored and are found to have significant impacts on performance. Three dimensional, unsteady simulations demonstrate how resistance to fluid flow in the pump reduces the amplitude of the piezo displacement and thus limits the flow rate of the device.