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A common assumption in the analysis of swashplate type axial piston machines (APMs) is to consider the relative rotation between the piston and cylinder block almost equal to the shaft speed. While this effect has been observed experimentally and confirmed by simplified models, an in-depth study and confirmation of the causes has never been undertaken. To address this, the presented work performs a simulation study of the piston and slipper spin in APMs. For this purpose, this work first develops a strongly coupled simulation model considering the displacing action of the machine coupled - with asynchronous time stepping - with the detailed simulation of its lubricating interfaces. The proposed approach accounts for the dynamics of the floating bodies in these machines, the ball-socket friction which couples the dynamic of each piston and slipper, and the impact on the fluid-structure induced cavitation and mixed lubrication in their tribological interfaces. As a consequence, the mutual interaction between the slipper-swash plate interface and the piston-cylinder interface of the APM is taken into account. After validating this model on a reference commercial unit, the impacts of the operating parameters (such as instantaneous displacement, pressure and shaft speed) and of the ball socket friction on the behavior of the machine are explored. It can be observed from the simulation results that the relative piston rotary motion in the cylinder bore varies with the operating conditions and the swashplate angle is one of the most influential parameters. • A novel piston machine simulation tool that considers coupled physics across multiple lubricating interfaces. • Ball joint friction modeling and coupled piston and slipper dynamics. • Numerical analysis of piston spin at various operating conditions using the proposed fully coupled model. [ABSTRACT FROM AUTHOR]

The understanding of the power loss contributions of each loss source is essential for an effective development of swash plate type axial piston pump. However, it is difficult to obtain the assessment of the power loss distribution due to the lack of methodologies that allow an independent evaluation of each source. This paper addresses this challenge using the most recent simulation methods. It describes the determination of each source, along with the corresponding loss of performance, and the principle of their prediction during the design phase. It also reports the validation of the simulation model by comparing the simulated dynamic displacement chamber pressure and the solid body temperature distribution with measurements obtained from a special pump prototype. This proposed virtual assessment of power loss contributions is demonstrated on a commercial hydraulic unit and the detailed results are reported in this paper. [ABSTRACT FROM AUTHOR]