Research On Coupling Theory And Its Experiments Between Vibration And Lubrication Of Ship Propeller Shaft

Propeller shaft is a critical component of the ship propulsive system. Being loaded complex and instable load, its axis is seriously deformed and hard to be concentric. Besides, main engine and propeller, which both have large mass and inertia, are fixed on the two sides of journal bearings. All of these will result in propeller shaft vibration and lubricant film oscillation under the external interference. So, it is very important to study the dynamic stability and reliability of propeller shaft for ship design and ship building.Based on study of propeller shaft, the paper, one the one hand, analyzes the load and deformation of propeller shaft, calculates the dynamic lubrication parameters of bearing and the frequency and vibration model of propeller shaft under the condition of bearing lubricant film coupling, on the other hand, the paper also gives a non-linear dynamic analysis of propeller shaft journal under the condition of bearing lubricant film supporting, analyzes the curve and torsional vibration coupling of propeller shaft under the action of impulsive load and verifies some results by experiments. According to the study, conclusion is druwn as follow:1. The propeller shaft is loaded the thrust torque and rotation inertia force, the bearing lubricant film supporting force, the propulsive force of propeller and other forces and torques, all of these fluctuant and instable loads will curve the axis, be partial that its quality exists in the axis and induce the vibration of propeller shaft and destroy the bearing lubricant film. As a result, keeping the stability of load and reducing the axis deformation will refrain the vibration effectively.2. The supporting capability of propeller shaft bearing lubricant film, dynamic stiffness and damping coefficient are closely related to the included angle between the centerline of journal and the centerline of bearing, and the eccentric rate of the center of journal. Two results can be druwn from the calculated curve variation tendency: (1) the relationship between the included angle, the eccentric rate of the center of journal and the propeller shaft bearing lubrication parameter is strongly non-linear. With an increase of the includedangle and eccentric rate, the supporting force of bearing and the damping coefficient will be increased accordingly, while the cross damping coefficient will decrease, and cross stiffness coefficient will increase or decrease. (2) Compared with the influence of included angle on bearing lubrication property, the eccentric rate is stronger.3. The vibration frequencies and vibration models of different ranks are interrelated to the rotation velocity. With an increase of the velocity, the stiffness of bearing lubricant film and the frequencies of different rank shaft vibration will decrease, and the vibration models will change accordingly. However, the changes of stiffness of bearing lubricant film make different influence on vibration frequencies with different rank. What can be seen from the acquired data table is that the influence of the change of film stiffness on low rank vibration frequency is stronger than the influence on high rank.4. It makes a strong non-linear relationship between the motion condition of journal and the viscosity of lubricant, the rotation velocity and mass eccentric rate of journal .The motion condition of journal will be co-period, double-period, resemble- period and chaotic under different parameters. The change of motion condition of journal is sensitive to the change of parameters. The calculation result indicates that the stability of porpeller shaft motion can be improved by means of increasing lubricant viscosity, decreasing mass eccentric rate and rotation velocity.5. The curve and torsional vibration response and coupling behavior are related to lubricant' viscosity, rotation velocity and mass eccentric rate when propeller shaft be under the action of impulsion load. The propeller shaft will be easily resulted in curve and torsional coupling vibration under the condition of low rotation velocity, low viscosity and large mass eccentric rate .At the same time, the influence of percussive load on propeller shaft is stronger.6. Tested the property parameter and curve of simulated propeller shaft on the dynamic simulation test board and proved the above-mentioned conclusions.