An Investigation of Design Parameters Influencing the Fluid Film Behavior in Scaled Cylinder Block/Valve Plate Interface

Abstract

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 Criteria for Axial Piston Machines Based on Thermo-Elastohydrodynamic Effects in the Tribological Interfaces

“…According to Figures 5-7, by proportionally scaling the axial piston machine, the performance of the three lubricating interfaces does not match the pre-scaled one, which agrees with the result published before [27,28]. The reasons that were found through the analysis and demonstrated through the simulation are that:…”

“…According to Ivantysyn and Ivantysynova [1], the energy efficiency of the three lubricating interfaces is determined by the power loss due to the leakage losses and friction losses. As described by Shang and Ivantysynova [27], the power loss due to the leakage and friction in a parallel gap as shown in Figure 3a,b yield:…”

“…According to Ivantysyn and Ivantysynova [1], the energy efficiency of the three lubricating interfaces is determined by the power loss due to the leakage losses and friction losses. As described by Shang and Ivantysynova [27], the power loss due to the leakage and friction in a parallel gap as shown in Figure 3a,b yield: Not only are the three interfaces required to fulfill a sealing function; they also have a bearing function. The hydrostatic and hydrodynamic pressures generated in the gap have to bear the external load.…”

“…Together with a pump flow temperature prediction model [26], Shang and Ivantysynova proposed a concept for nonlinearly scaling a number of key design parameters in order to compensate for the performance loss due to the size variation; the concept is based on a full factory simulation study [27,28]. According to their research, nonlinearly scaled design parameters are able to bring the scaled pump and motor performance closer to the pre-scaled one.…”

“…For the piston/cylinder interface, use a lower normalized clearance for up-scaling, and use a higher normalized clearance for down-scaling [28]. For the cylinder block/valve plate interface, increase the sealing land area for up-scaling, and decrease the sealing land area for down-scaling [27].…”