Research On Gear Vibration Characteristics At The State Of Oscillation Coupling Torsional Vibration And Speed Control Of Diesel Engine

Since the rotational speed oscillation caused by shafting torsion vibration coupling with speed control of diesel engine happens widely. The fault directly leads to the large fluctuation of engine speed and the sever vibration of gearbox because of the process of gear engagement and the vibration characteristics of gearbox are affected by the fluctuation of rotational speed.In this paper,aimed at the vibration characteristics of gear system at the state of oscillation,a model coupling the three parts containing the characteristics of gear system, shafting torsional vibration and speed control of diesel engine was established. A method of analyzing the excitation source of vibration of the gearbox and the shafting at the fault state.(1) The three-dimensional finite element model of gearbox was built. The model was verified by comparing the calculation results with the test of modal analysis. Besides, based on the theoretical formula of Y.Cai, the dynamic excitations of gear engagement are simulated numerically which are periodic without affected by coupling oscillation.(2) The model of the gear system was refined, and characteristics of the gear engagement were added into the existed coupling simulation model. Finally,a new model coupling the characteristics of gear system, shafting torsional vibration and speed control of diesel engine was established. It was proved that the coupling model built in this paper could not only accurately check the effect on speed control of PID control parameters and predict the reasonable PID parameters to keep engine running steadily, but also update the excitations of the gear system at the state of oscillation.(3) The vibration responses of the gearbox were calculated under the action of periodic excitations of gear system which could match the testing results at the normal state, rather than the fault state. Then, the updated excitations were used as the excitation source. The new group of vibration responses could reflect the vibration characteristics of the gearbox at the fault state.To sum up, the coupling model built in this paper can be used to analysis and research the real vibration characteristics of gear system at the fault state of speed oscillation.