The low-noise optimisation method for gearbox in consideration of operating conditions
This paper presents a comprehensive procedure to calculate the steady dynamic response and the noise radiation generated from a stepping-down gearbox. In this process, the dynamic model of the cylindrical gear transmission system is built with the consideration of the time-varying mesh stiffness, gear errors and bearing supporting, while the data of dynamic bearing force is obtained through solving the model. Furthermore, taking the data of bearing force as the excitation, the gearbox vibrations and noise radiation are calculated by numerical simulation, and then the time history of node dynamic response, noise spectrum and resonance frequency range of the gearbox are obtained. Finally, the gearbox panel acoustic contribution at the resonance frequency range is calculated. Based on the conclusions from the gearbox panel acoustic contribution analyses and the mode shapes, two gearbox stiffness improving plans have been studied. By contrastive analysis of gearbox noise radiation, the effectiveness of the improving plans is confirmed. This study has provided useful theoretical guideline to the gearbox design.
NUMERICAL SIMULATION OF DYNAMIC RESPONSE AND SHOCK RESISTANCE OF MARINE GEARBOX
The time-variable meshing stiffness of the geer and the impact excitation between meshing teeth pairs are calculated by finite element method for 3-D impact/dynamic contact problem, the gear error and the external acceleration excitation being described by simple harmonic functions. Considering the internal dynamic excitation produced by stiffness excitation, error excitation and mesh impact excitation as well as the external excitation brought by impulsive acceleration, the dynamic finite element model of gearbox is established. Using the software of I-DEAS, the normal modes of gearbox are calculated, the dynamic responses of gearbox under the internal and external excitation are simulated, and the dynamic stresses are determined. The research results lay down a theoretical basis to determine the shock resistance of marine gearbox.
Ground Fault Protection for Electric Utility Generating Station Medium Voltage Auxiliary Power Systems
Most generating station designs have medium voltage auxiliary power systems with low resistance grounded neutrals.1 In order to provide even higher reliability, the auxiliary power distribution system configurations supply increasingly redundant process equipment.