Optimum design of seat region in valves suitable for digital displacement machines

Digital displacement fluid power is an upcoming technology setting new standards for the achievable efficiency in variable displacement fluid power pumps and motors. In the present work, an annular seat valve suitable for use in digital displacement units is considered, and the valve geometry is optimised considering both the mechanical strength during pressure loading and fluid flow restriction in the open valve state. Material stresses are modelled using finite element (FE) analysis including non-linear material behaviour, contact elements and fluid pressure penetrating load, closely reflecting the actual load of the seat valve connected to a fluid pressure chamber. Valve pressure losses are modelled using computational fluid dynamics (CFD). On basis of an overall physical size requirement and material specification, optimum valve geometry and stroke length are given as function of a defined normalised flow coefficient directly related to the machine efficiency.