Dynamic lubrication analysis for a spherical pump

Abstract

Dynamic lubrication analyses for a spherical pump, consisting of a piston and cylinder, are presented. Contact forces between piston and cylinder are modeled first using an equivalent ball-on-plane model. Both the effects of external loads and operating conditions are considered in a dynamic elastohydrodynamic lubrication model, which is derived from Reynolds equation. Two assumed time-dependent sine-wave and square-wave loads are applied to the model. Fluid film thicknesses are estimated using the model and assumed loads, effects of different structural, and operational parameters, such as piston diameter, radial clearance, applied load, piston speed, lubricant viscosity, and surface roughness, on fluid film thickness are investigated. Fluid film thickness reactions of more realistic smooth and continuous sine wave loads are compared to discontinuous ones in order to verify whether or not assumed ideal loads are acceptable and reliable. Results indicate that piston diameter, speed, lubricant viscosity have positive relations on the dynamic lubrication performance, and increasing these values can improve the dynamic lubrication regime. While the parameters such as radial clearance, applied load, and surface roughness have the verse effects. Furthermore, the impacts of all the above parameters on fluid film are different either. These obtained results can be used to effectively optimize spherical pump lubrication performance.

Friction and wear behavior of single-phase high-entropy alloy FeCoNiCrMn under MoS2-oil lubrication

“…f displays a tendency to decrease in approximate linear relation (Figure 4(d)). Higher speeds will change the lubricity of the ball-on-disc pair (Guan et al, 2019a(Guan et al, , 2019b. As the reciprocating velocity increases, the thickness of the lubricating film increases, implying that higher speeds can effectively improve the lubrication performance.…”

“…The friction coefficient has a second falling edge during the 4-8 min phase, especially when F N is 40 N and 50 N. Moreover, As F N increases, f exhibits a slight downward trend [Figure 4(e)]. Given that the increase of load has little influence on the lubrication state, the size of the contact area may become the main factor (Guan et al, 2019a(Guan et al, , 2019bGuan et al, 2018aGuan et al, , 2018bGuan et al, , 2018c. Since the amplification of the contact area is higher than the growth of F N , that is, the actual contact area is nonlinearly related to F N (Oden and Pires, 1983), f decreases as F N increases.…”

Theoretical modeling and numerical simulation of dynamic contact characteristics of a spherical pump with variable friction coefficient

“…The spherical pump is a new type of hydraulic pump, which has the advantages of compact design, low vibration, and low noise emission. [1][2][3][4][5][6][7][8] Guan et al 1 studied the kinematics principle of the spherical pump by establishing the kinematic model. Both vibration and noise properties of the spherical pump were compared with a solenoid pump, and the inherent mechanism was analyzed as well.…”

“…Besides, Liu and coauthors 3 developed the portable electro-hydraulic actuator (EHA) using a spherical pump; the EHA is expected to be used as the power source of walking robots and exoskeleton robots. Recent studies on the spherical pump mainly focus on the tribology properties, [4][5][6][7] including the normal 6 and tangential 4 contact characteristics between a piston and a cylinder block. Besides, both the static 7 and dynamic 5 lubrication performance in spherical pumps were also studied comprehensively.…”

Friction and wear modeling of rotary disc in spherical pump

“…Different from the traditional hydraulic pumps (Ma et al, 2014), spherical pump is a new concept of positive displacement pump whose discharge pressure is between the gear pump and piston pump (Guan et al, 2016;Guan et al, 2018a;Guan et al, 2018b;Guan et al, 2018d;Guan et al, 2018c;Wu et al, 2016;Niu et al, 2016). Spherical pump has the properties of compact, lightweight, low noise and slight vibration as a result from no reciprocating parts (Guan et al, 2015c;Guan et al, 2015b;Guan et al, 2015a).…”