Research On Coupling Characteristics Of Work Status Of Ship Stern Shaft And Mechanical Seal Device

The mechanical seal is widely used in the stern seal of shaft. Meanwhile, the size of marines and the weight & length of stern shaft are becoming large, and dynamic properties of stern shaft are more complicate. So as to insure the reliability of operating, reasonable analysis of factors, which influences the dynamic properties of stern shaft, should be taken. It is gradually known that bearings and seals influence the vibration characteristics of stern shaft, and oil-film force and seal fluid force are two key factors among the given nonlinear ones.The model of Jeffcott rotor is applied, and the dynamic response of rotor under the ict of seal fluid force is analyzed. Conclusions are summarized as follows:(1) Because the shaft system in the dissertation is nonlinear dynamic system, it is introduced basic nonlinear theory used frequently in the study on dynamics of rotor, model of nonlinear oil-film force and seal-fluid force in the paper.(2) Nonlinear response of single Jeffcott rotor excited by seal force is studied. It comes out that the amplitude varies with the rotor speed. The time histories, tracks of the rotor center, power density and Poincare maps are used to illustrate the dynamic characteristics and the influences of varying pressure, eccentricity, seal length and clearance.(3) The response of the rotor-bearing-mechanical seal system is solved under the seal fluid force coupled with oil-film force. The discussion shows the amplitude is varied with the rotor speed. Time histories, tracks of the rotor center, power density and Poincare maps are used to demonstrate the dynamic features. The influences of varying pressure, eccentricity, seal length and clearance, rotor clearance and length are analyzed, and the range of parameters used to keep the system stable is gotten, which provides theoretical basis for design and choice of devices.(4) Three methods to judge the stability of rotors are introduced, which are Phase plane method, Maximum Lyapunov exponent and Floquet multipliers. In final the methods of getting Maximum Lyapunov exponent and Floquet multipliers of corresponding systems are introduced.At the end of the dissertation, research works to bring forth new ideas for the dissertation are summarized, and the research problems to go to a step further are pointed out.