Hydrostatic Pressure Distribution of Oil Lubrication Film for Internal Gear Motors and Pumps: Solution of Resistance Network and Compare to CFD

Oil thin film lubrication is very popular and important in the field of fluid power and tribology science. It is widely used in all kinds of rotating machines. Its role is to separate the relative rotating surfaces to reduce friction, absorb vibration, protect surfaces, and produce load-carrying against an external load. The capacity of the oil lubrication film plays an important role in dynamic behavior, the life-cycle performance of the rotating machinery as well as the systems. During operation, if the oil film is damaged, it will cause the relative rotating surfaces to fail much sooner before the damage of components of the machine. This paper introduces the resistance network model to calculate the hydrostatic pressure distribution of the oil lubrication film. The effect of geometry and working parameters on the pressure distribution is then analyzed. Among these parameters, the calculation results point out that the radial and axial clearance, as well as the eccentricity of the ring gear, have a significant effect on the hydrostatic pressure distribution. The pressure profile is also simulated by using the CFD software in order to compare and validate the accuracy of the calculation results. With the solution of resistance network model, it is easy and quick to calculate the hydrostatic pressure distribution comparing to CFD. It saves time for designers at the early design stage.

Numerical and experimental studies on the thermal characteristics of the clutch hydraulic system with provision for oil flow

PurposeThis paper aims to investigate the thermal characteristics of the clutch hydraulic system under various oil flow conditions. Increasing the oil flow is one of the most important approaches to reduce the clutch temperature. However, the effect of the oil flow on the clutch temperature remains to be explored.Design/methodology/approachThe thermal resistance network model and the lumped parameter method are used to study the thermal characteristics of the clutch hydraulic system. The predicted temperature variations of the clutch and the oil are compared with experimental data.FindingsResults demonstrate that the larger the friction power is, the higher the temperatures of the clutch and the oil are. However, the temperature growth rates of the clutch and oil present different trends: the former decreases gradually and the latter increases constantly. Additionally, increasing the oil flow within a certain range gives rise to the decrease of clutch temperature and the increase of oil temperature; nevertheless, their variation trends are gradually weakening. When the oil flow is large enough, it brings a slight effect on the clutch temperature rise.Originality/valueThis paper extends the knowledge into the oil flow supply of the clutch hydraulic system. The conclusions can provide a theoretical guidance for the oil management of the transmission system. Additionally, the thermal resistance network model is also effective and efficient for other hydraulic equipment to predict the temperature variation.