Non-dimensional characteristics of open wet clutches for advanced drag torque and aeration predictions

The remaining torque of disengaged wet clutches is a major source of energy loss and, therefore, an objective of current research. The present contribution describes the necessary simplifications to obtain an analytical solution of the governing equations by means of an order-of-magnitude analysis. The obtained results are brought to a dimensionless frame of reference, where formerly unknown simple dependencies of the drag torque and the aeration onset have been uncovered. The dimensionless description serves as promising a means to achieve a quantitative comparison of experimental data. Additionally, a new modelling concept for grooves is introduced, which is based on the hydraulic-diameter concept. The combination of either approach offers a robust prediction method for drag torque and aeration onset. •Simplifications for governing equations seems justified as long urh2νR≪1 is valid.•The obtained equations are brought to a dimensionless frame of reference.•Drag torque and aeration onset can be described with ζm=πRel and Qcrit∗=π20•A model to consider grooves, which is based on the hydraulic diameter is presented.•Summarizing, a prediction method of drag torque and aeration onset is presented.