Research On Dynamic Characteristics Of Journal Bearing Gear System With Ship Rolling And Pitching Motions

In warship high-powered engine system,gear reducer is used to transfor the high-speed power of the engine to the low-speed of the propeller shaft,so that to push the warship ahead by driving the propeller.Gear journal bearing systems are setted in the gear box as basic configuration units.According to the power level,transmission ratio,ordinary gear train or planetary gear train is assembled.On one hand,due to large bearing clearances,large amplitude whirling motion of the rotor causes time-variation of the contact ratio,mesh angle and other meshing parameters,leading to a larger fluctuation of the mesh stiffness.Under different exicitations,system dynamic behaviour becomes more complex.On the other hand,stormy waves induce low frequency rolling and pitching motions of the ship-body,making influence on the system through oil-film forces of the journal bearings.This work aimed at gear journal bearing system,which is mounted on a warship with rolling or pitching motion,established a system dynamic model involving time-variation of contact ratio,nonlinearity of bearing oil-film force,inertia force induced by ship motion and other factors.Studies on dynamics of ordinary gear system and planetary gear system are made under different kind of ship motions.Main work includes(1)Mesh force model of external gearing and internal gearing in spur gear system are derived involving time-variation of contact ratio.Nonlinear oil-film force model of journal bearing is introduced in.Anti-rotational form of the model is given.Demonstration is given to show the validity of the oil-film force model when the bearing pads are mounted inner the gear.Dynamic model of the basic gear journal bearing system is established.(2)Aiming at ordinary gear system with journal bearings mounted on fixed base,analysis about the influence on contact ratio by equilibrium positions are made.Study on system dynamic response,instability are made by changing the operation conditions and bearing center distance.Comparison between results dominated by different mesh force models are made,interaction among bearing clearances and backlashes are examined.(3)Motion equations of a rotor system in non-inertia system are derived by setting up different reference frames,kinematic analysis and Lagrange Equaiton.Rotor gear journal bearing system dynamic mdoel considering warship rolling and pitching motion are established.Dynamic study are made about the system excited by ship-body motion.Analyses on response components of rotational frequencies and ship motion frequencies are examined by applying constant mesh stiffness model.Analyses on response components of mesh frequencies are made by applying time-varying mesh stiffness model.Interactions between bearing clearances and backlashes are examined under the ship-body motion excitation.(4)Dynamic response of planetary gear system under ship-body motion excitations are studies.Resorting to equiations derived ahead,planetary system dynamic model are established on the rotating frame,which is fixed on the carrier.By introducing the ship-body motion,system model is given with ship rolling motion.Based on these models,dynamic studies about the system are made under the combination between carrier rotation and ship-body motion.(5)Test rigs of rotor gear journal bearing system,which is mounted on fixed base and rolling base,are designed and built.Corresponding tests are made to study the dynamic characteristics of the system under different base motion excitations.The theoretical analyses and numerical results are compared to show the validity of the former theoretical models and analyses.