Study On Dynamics Of Herringbone Gear-rotor-journal Bearing System With Lubrication Effects

Due to many advantages,such as large transmission power,high stability,low noise,etc,the herringbone gear-rotor-journal bearing(called HGRB for short)system is widely used in high duty and power machines of ships,aerospace,petroleum and other industry applications.As the development of modern industry,which requires larger transmission power,higher reliability,lower noise and other improvements,it presents stringent requirements on performance of HGRB system,such as dynamics,lubrication design and so on.In HGRB system,there are oil-films between meshing teeth and in the clearance of journal bearings.The operating states of oil-films not only has influence on the friction,wear and temperature of teeth and bearings,but also has influence on the dynamics of HGRB system.The original lubrication condition and friction state of oil-films between meshing teeth can affect the tooth friction force,meshing stiffness and damping directly,and the nonlinear oil-film force of oil-film in journal bearing has been recognized as an important nonlinear excitation for gear-rotor-journal bearing system.But in studies now available,the influence of oil-films between meshing teeth is neglected in most cases,and the nonlinearity of oil-film in journal bearing is often neglected or simplified.The above treatments on lubrication effects cause the deficiency of nonlinear characteristics and reduce the accuracy of dynamic analysis,which make current dynamic analysis of HGRB system cannot meet the engineering requirements.Therefore,in present paper,HGRB system lubricated with spray lubrication is focused,and a study on dynamics of HGRB system with lubrication effects is carried out,including lubrication effects of oil-films between meshing teeth and in the clearance of journal bearings.The contents of present paper are as follows:(1)For the fact of time-varying and nonlinear load operating on journal bearings produced by gear mesh,a model used on calculating nonlinear oil-film force and oil-film friction torque is developed based on the hydrodynamic lubrication theory,and the effects of eccentricity ratio,rotating and shift speed of shaft on the performance characteristics of journal bearing are analyzed.Then a fast algorithm for calculating nonlinear characteristics of journal bearing is built with genetic algorithm and BP neural network technique(called GA-BP neural network for short).The GA-BP neural network represents the functional relationship between location and shift parameters of shaft and nonlinear characteristics of journal bearing,including nonlinear oil-film force,oil-film friction torque.GA-BP neural network presents an algorithm for the subsequent dynamic analysis of HGRB system to calculate nonlinear characteristics of journal bearing with high-efficient and high-precision.(2)Focused on spray lubrication,which is widely used for lubrication of gear train systems at high speed,the lubrication process that oil flows,deposits and spreads on tooth surface is simulated,and the deposition thickness of oil-film on tooth surface is obtained.Then,combined with geometrical and kinematic analysis of gear mesh,the minimum oil-film thickness and friction state of different mesh points on tooth surface are obtained.At last,according to the elastic-hydrodynamic lubrication theory,the time-varying and multi-friction states algorithm of tooth friction characteristics,meshing stiffness and damping is built,considering the effects of original lubrication condition and friction state of oil-films between meshing teeth.And the effects of parameters of spray lubrication on tooth friction characteristics,meshing stiffness and damping are studied.The work in this section provides the algorithm of tooth friction characteristics,meshing stiffness and damping for subsequent dynamic analysis of HGRB system.(3)Based on all the studies above,considering the effects of oil-films between meshing teeth and in the clearance of journal bearings,a dynamic model of HGRB system,including tooth friction characteristics,meshing stiffness and damping,nonlinear oil-film force and oil-film friction torque of journal bearings,is proposed.Then,the dynamic model is used to study the effects of oil-films,some excitations,geometrical parameters of journal bearing and parameters of spray lubrication on dynamics of HGRB system.(4)To evaluate the theoretical methods and results in present paper,a test rig of HGRB system is developed with mechanical closed power flow.On the test rig,the oil-film pressure of journal bearings and relative vibration in meshing line direction are measured.And the experimental results are compared with their theoretical results.Lastly,the rationality of theoretical methods and results is supported by experimental results.The analysis of present paper shows that,the dynamic model with lubrication effects is more suitable to describe practical engineering;the oil-film between meshing teeth have notable effect on dynamics of gear-rotor-journal bearing system,due to its effects on tooth friction characteristics,meshing stiffness and damping;the effects of nonlinear oil-film force of journal bearings also have impact on the dynamics,but the effects of oil-film friction torque of journal bearings is small;due to nonlinear oil-film force of journal bearings,the structural parameters of journal bearing affect the dynamics significantly;the parameters of spray lubrication affect the dynamics less;and the lubrication effects increase with the raising of speed or load.In present paper,an algorithm with high-efficient and high-precision for calculating nonlinear characteristics of journal bearing is obtained based on hydrodynamic lubrication theory and GA-BP neural network model;the relationship from parameters of spray lubrication to deposition thickness of oil-film on tooth surface to minimum oil-film thickness and friction state on tooth surface,and to tooth friction characteristics,meshing stiffness and damping is presented firstly,which builds a bridge between lubrication parameters and dynamics;the analysis method of dynamics with lubrication effects is built,and effects of structural parameters of journal bearing and parameters of spray lubrication on dynamics is studied.The studies in present paper can enrich theoretical system of dynamics for gear train system,and provide reference for design of lubrication and journal bearings in gear train system.