Flow Rate Distribution in Lubricating Systems with Rotating Shafts

This research focuses on predicting the distribution of lubricant flow through the outlets of a rotating shaft used in automotive power transmission systems. The study examines a typical configuration with closely spaced rows of holes, designed for the lubrication of multi-disc clutches. Both lumped parameter models and computational fluid dynamics (CFD) methods were employed and compared. A test rig, shown in figure 1, was developed for model validation, featuring a variable-speed shaft with an axial oil inlet and three pairs of radial outlet holes evenly distributed around the shaft (figure 2).

Figure 1

Figure 2

A key feature of the experimental setup is its ability to independently measure the flow rate through each outlet. The findings indicate that the three-dimensional model based on the multiple reference frame (MRF) approach accurately predicts the flow rate distribution. It was observed that the outlet closest to the inlet has the lowest flow rate, while the outlet farthest from the inlet provides the highest. The distribution of flow rates is only slightly influenced by the rotational speed of the shaft. An example of oil velocity field is shown in figure 3.

The study also explored how geometric parameters affect flow uniformity, revealing that a lower ratio between the diameter of the radial holes and the axial channel results in better flow balance. These results provide practical guidelines for accurately simulating similar systems, aiming to enhance the reliability of mechanical transmissions and improve the energy efficiency of the lubrication system.

Figure 3

More analyses and details are available in:

RUNDO M, FRESIA P, CASOLI P, 2023: Simulation Approaches for the Study of the Oil Flow Rate Distribution ...

FRESIA P, RUNDO M, 2022: Analysis of the flow rate through rotating shafts in lubricating circuits