Research on the Mechanical Efficiency of High-Speed 2D Piston Pumps

Abstract

Since many studies on axial piston pumps aim at enhancing their high power-weight ratio, many researchers have focused on the generated mechanical losses by the three friction pairs in such pumps and attempted to diminish them through abundant and new structural designs of the pump’s components. In this paper, a high-speed 2D piston pump is introduced and its architecture is specifically described. Afterward, a mathematical model is established to study the pump’s mechanical efficiency, including the mechanical losses caused by the viscosity and stirring oil. Additionally, in this study the influences of the rotational speed, the different load pressures, and the rolling friction coefficient between the cone roller and the guiding rail are considered and discussed. By building a test rig, a series of experiments were carried out to prove that the mechanical efficiency was accurately predicted by this model at low load pressures. However, there was an increasing difference between the test results and the analytical outcomes at high pressures. Nevertheless, it is still reasonable to conclude that the rolling friction coefficient changes as the load pressure increases, which leads to a major decrease in the mechanical efficiency in experiments.

Investigation of the Churning Loss Reduction in 2D Motion-Converting Mechanisms

“…The last generation of 2D motion-converting mechanisms, which were applied in both 2D pumps and 2D flowmeters [10,14], adopts a fixed cam guiding rail and pairs of active cone rollers. Contrarily, the new 2D motion-converting mechanism makes the cone rollers fixed on the cylinder, where the cam guiding rails are the active parts rotating and reciprocating in the oil chamber, as shown in Figure 3.…”

“…Contrarily, the new 2D motion-converting mechanism makes the cone rollers fixed on the cylinder, where the cam guiding rails are the active parts rotating and reciprocating in the oil chamber, as shown in Figure 3. More specifically, compared with the last 2D pump design in reference [10], as shown in Figure 2, the unique change here was that the new 2D pump had pairs of cone rollers fixed on the cylinder block in addition to cam guiding rails fixed on the ends of both the driving and balancing sets. The reciprocating stroke of the 2D piston keeps the same as well as the pump's displacement for every stroke.…”

“…The reciprocating stroke of the 2D piston keeps the same as well as the pump's displacement for every stroke. Since the same working principle was introduced in references [10,15], the distribution function was still provided through the windows and the rotating slots on the rotating 2D piston, whereas the opposite reciprocation motion from the 2D piston and piston rings provides the discharging and sucking functions. The driving rail is inside the balancing rail, and they keep a simultaneous rotational speed due to the fork.…”

“…Due to the requirements of higher power-weight ratio for 2D pumps and higher resolution for 2D flowmeters, the designs of either pumps or flowmeters undergo a trend of applying higher rotational speeds. Moreover, to balance the inertial force produced by single 2D pistons, a more complicated 2D motion-converting mechanism was presented with two supports and four cone rollers, as shown in Figure 2 [10]. The above two improvements imply that a rotational speed-related phenomenon, so-called the churning loss, occurs at the stirring of the 2D motion-converting mechanism in hydraulic oil, and it accounts for unneglectable energy losses, especially at high rotational speeds.…”

“…Structure of the 2D motion converting mechanism and its simplified simulation model for studying churning losses[10,15]: (1) The driving rollers support; (2) Cone rollers; (3) Balancing rollers support; (4) Cam guiding rail (fixed with the cylinder).…”