He Yongyong

Simulation and experiment of viscous torque for disengaged wet clutches of tracked vehicle

In order to predict the viscous drag loss for tracked vehicles, the drag torque of the friction pair with different grooves was investigated in this paper. The traditional computation method is difficult to adapt for the new kinds of friction plates with complex grooves. A numerical method with the help of CFD models is adopted to simulate the fluid flow status in the grooves and the drag torque was obtained by the accumulation of the discrete viscous force. The simulation results implied that the plates with different kinds grooves were provided with various characteristics of viscous torque and these characteristics could be affected by the rotation direction for the plate with spiral grooves, which are proved in experiment. Meanwhile, it was also found that the two kinds of plates with double arc or spiral grooves, which have different sensitive parameters in drag dissipation, have to perform accurate flow control and clearance design respectively. The simulations and experiments showed that the ‘positive spiral grooves’ friction plates had minimum drag torque in regular heavy-duty conditions. It can be used in transmission system with requirements of limited space and high mobility, which can lead to better heat dissipation and less power loss.

Blind identification of threshold auto-regressive model for machine fault diagnosis

A blind identification method was developed for the threshold auto-regressive (TAR) model. The method had good identification accuracy and rapid convergence, especially for higher order systems. The proposed method was then combined with the hidden Markov model (HMM) to determine the auto-regressive (AR) coefficients for each interval used for feature extraction, with the HMM as a classifier. The fault diagnoses during the speed-up and speed-down processes for rotating machinery have been successfully completed. The result of the experiment shows that the proposed method is practical and effective.