Experimental and numerical dynamic analysis of marine herringbone planetary gearbox supported by journal bearings

Previous studies supposed that planet bearings are springs with isotropic stiffness and damping, whereas the stiffness and damping of journal bearings are asymmetric and interactive. As a result, a coupled dynamic model of the herringbone planetary gear train (HPGT) with journal bearings is established, considering the planetary bearing eccentricities and the asymmetry and interaction of journal bearing dynamic parameters (stiffness and damping). Besides, the gearbox casing condensation model is proposed by the Component Mode Synthesis method, is verified by modal tests, and is incorporated into the established dynamic model. The dynamic performances of the marine gearbox for different operating conditions and planetary bearing parameters are explored under the uncoupled and coupled casing conditions. The result shows that different operating conditions may result in different effects of gearbox casing flexibility on meshing force and load -carrying capacity. Meshing forces and bearing capacities are positively correlated with width -diameter ratios, while they are inversely correlated with radial clearances of planet bearings. A test rig for the herringbone planetary gearbox with journal bearings is constructed for verifying the reliability of the proposed model. Experiments demonstrate the maximum relative error be-tween the measurement and prediction of structural noise of the gearbox casing is 1.72%. This work provides a theoretical basis for the optimal design of the marine gearbox.