Numerical and experimental investigation of drag torque in a two-speed dual clutch transmission

• Theoretical and experimental study of the losses in a dual clutch transmission.
• The test results for DCT efficiency agree well with the simulation results, especially the critical speed prediction.
• Efficiency of DCT grows with the input torque increasing, and decreases with the rise of input speed.
• The entire drag torque is dominated by the viscous shear in the wet clutch pack, followed by the differential gear churning and windage losses.

The theoretical analysis of drag torques within a two-speed dual clutch transmission is presented in this article. The numerical models are developed to study the different sources of drag torques in dual clutch transmission. Simulations are performed in Matlab/Simulink platform to investigate the variation of drag torques under different operating conditions. Then an experimental investigation is conducted to evaluate the proposed model using an electric vehicle powertrain test rig. Outcomes of experimentation confirm that simulation results agree well with test data. Therefore the proposed model performs well in the prediction of drag torque for the transmission, and can be applied to assess the efficiency of the transmission. Results demonstrate that the entire drag torque is dominated by the viscous shear in the wet clutch pack and gear churning losses. This lays a theoretical foundation to future research on reducing drag torque and applications of drag torque in powertrain system efficiency optimization.