Digital Displacement® (DD) machines are upcoming technology where the displacement of each pressure chamber is controlled electronically by use of two fast switching seat valves. The effective displacement and operation type (pumping/motoring) may be controlled by manipulating the seat valves corresponding to the piston movement, which has been shown to facilitate superior part load efficiency combined with high bandwidth compared to traditional displacement machines. However, DD machines need fast switching on-off valves with low pressure loss for efficient operation, especially in fast rotating operation, where switching times must be performed within a few milliseconds. These valve requirements make a simulation based design approach essential, where mechanical strength, thermal dissipation, fluid dynamics and electro-magnetic dynamics must be taken into account. In this paper a complete design method for DD seat valves are presented, taking into account the significant aspects related to obtaining efficient DD valves with basis in a given DD machine specifications. The seat area is minimized and the stroke length is minimized to obtain fast switching times while considering the pressure loss of the valves. A coupled optimization is finally conducted to optimize the electro-magnetic actuator, leading to a valve design based on the chosen valve topology. The design method is applied to an example DD machine and the resulting valve design fulfilling the requirements is presented.

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