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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.

The efficiency of an axial piston pump or motor is dominated by the volumetric and torque losses of the three main lubricating interfaces (piston/cylinder, cylinder block/valve plate, and slipper/swash plate). The research study in this paper only focuses on the cylinder block/valve plate interface. The goal of this research is to investigate a novel approach for scaling the cylinder block/valve plate interface to have the same percentage of volumetric and torque losses of the baseline interface. To achieve this research goal, many design parameters influencing the performance of the interface are investigated. An in-house developed fluid structure and thermal interaction model was used to analyze the cylinder block/valve plate interface including the resulting parts temperature, the parts elastic deformation due to pressure and thermal load, the fluid film properties and resulting energy dissipation, friction torque, and leakage of cylinder block/valve plate interfaces. This model is utilized to simulate the cylinder block/valve plate interface performance of different sizes of the displacement units. In this paper, the displacement volume of the biggest unit is sixty-four times larger than the smallest unit. The computational study reveals the design parameters influencing the elastic deformations of the solid parts and the energy dissipation and stability of the fluid film in cylinder block/valve plate interface of different sizes. Based on these investigations, a novel scaling approach to scale the cylinder block/valve plate interface is discussed.

Scaling three main lubricating interfaces (piston/cylinder interface, cylinder block/valve plate interface, and slipper/swash plate interface) of swash plate type axial piston machine while remaining the pump performance is a rewarding but challenging task. Instead of designing a new unit for the desired displacement, scaling a well-designed existing unit to the desired size requires much less computational and experimental cost. However, scaling all the components linearly is far from enough to remain the original sized unit’s performance due to the unscalable fluid properties and material properties. This paper proposes a novel scaling method for the piston/cylinder interface which is able to achieve the baseline performance at some of the operating conditions, and closing the gap between the scaled unit performance and the baseline performance at the rest of the operating conditions. The authors use a special in-house developed simulation tool to study the design parameters of the piston/cylinder interface impacts on the performance in terms of leakage flow rate, and the energy dissipation. This in-house developed tool is able to model the lubricating fluid film behavior considering the complex fluid and structure interaction, the macro and micro motion of the piston, the three-dimensional fluid heat-transfer, the three-dimensional solid part heat-transfer, and the solid part deformation due to both the pressure and the thermal load. This paper includes a brief introduction of the simulation tool, the results of the design parameters investigation, the proposed scaling method, and the simulation results comparison between the baseline unit and the scaled unit using the proposed method.