Wet Clutch Drag Loss Simulation for Different Clutch Patterns 2022-01-1118

Wet clutches drag loss simulation is essentially linked to the clutch friction surface patterns in addition to the main geometry and conditions of the interface (relative speed, separation, inner and outer radius, viscosity and boundary pressures). The clutch patterns promote cooling flow and micro-hydrodynamic effects to aid clutch separation but greatly complicate the simulation of drag loss during separation. These drag losses are important in understanding the system losses as well as finding the most effective clutch cooling strategy. Typical clutch models either only consider simple patterns, such as radial grooves, or require significant simulation efforts to evaluate. Additionally, many simple models require calibration to measurement of the actual clutch they try to model before they provide a useful model.

A methodology utilizing smooth particle CFD (PreonLab) will be demonstrated to provide a fast and effective solution to any given clutch pattern, capturing the fundamental viscous drag region and film rupture point and subsequent reducing curve and the operating temperature effect on drag losses. A post-processing solution will be shown in which a segment of the overall clutch interface area is discretized, and surface wetted area is extracted to allow a calculation of the resulting lubricant shear stresses. The methodology easily compliments other simulation for the flow rate and distribution of lubricant in single or dual wet clutch packs within transmission systems. It will be shown that the proposed method provides reasonable results in comparison to literature and existing analytical models of simple clutch geometry.