Computer Aided Optimization of Bearing and Sealing Gaps in Hydrostatic Machines—The Simulation Tool Caspar

The simulation tool CASPAR (Calculation of swash plate type axial piston pump and motor) is presented in this paper. Based on the simulation of the flow through the lubricating gaps in swash plate type axial piston machines the pressure, velocity and temperature fields in the considered gaps can be determined. This allows the calculation of the main losses generated in the machine due to viscous friction and gap flow. The individual gaps are connected in a complex way to each other. The calculation of the gap flow requires the determination of the instantaneous gap heights for all considered gaps. This is realized by solving the motion equation for all moveable parts of the rotating group. For determination of pressure dependent external forces the instantaneous pressure in the displacement chamber is calculated simultaneously. The program further calculates the instantaneous inlet and outlet flow of the swash plate machine for pumping and motoring mode as well as internal volumetric losses.