SAE International New Development of a Gas Cavitation Model for Evaluation of Drag Torque Characteristics in Disengaged Wet Clutches 2016-01-1137

A significant reduction of C0 2 emission can be achieved by improving the efficiency of transmission of cars. A reduction of drag torque or spin loss of disengaged clutches can improve the efficiency of transmissions. Generally, the drag torque is measured by conducting drag test which needs making samples, manpower, power and wastage of raw materials. In this paper, an analytical model is proposed to predict the drag torque of a disengaged wet clutch at different rotation speeds, clearances, disk sizes and oil temperatures without making any samples and conducting any drag tests. Various assumptions are made from the results of visualization investigations. Visualization results show that the volume of oil existed in between the clutch disk and clutch plate decreases with increasing speed due to centrifugal force. It is also noticed that several visible air bubbles are formed in the oil film at lower speeds and the size of the bubbles increase with increasing speeds. We consider that the gas cavitation has a significant role in air bubble formation. The model is validated with test results and it shows that they are almost coincident with each other.