Design Optimization of Moving Magnet Actuated Valves for Digital Displacement Machines

High-efficiency hydraulic machines using digital valves are presently a topic of great focus. Digital valve performance with respect to pressure loss, closing time as well as electrical power consumption, is key to obtaining high efficiency. A recent digital seat valve design developed at Aalborg University utilizing moving coil actuation, meets these performance demands but is challenged by practical issues. This paper builds upon that design by proposing a retrofit which preserves both the seat valve topology and the outer dimensions, but utilizes moving magnet actuation. Through constrained multi-objective optimization, six initial topologies and three derived topologies, including designs with one, two and four coils, are optimized with respect to overall efficiency. Apart from the actuator, the flow forces on the seat valve geometry is modeled using CFD and included in optimization. In simulation the final optimized design closes in 2.1 ms, has a pressure drop of 0.8 bar at 150 l/min and yields a digital displacement machine average chamber efficiency of 98.9%. The design is simple in construction and uses a single coil, positioned outside the pressure chamber, eliminating the need for an electrical interface to the pressurized valve chamber.