| Rotating machinery is an indispensable part of mechanical system,centrifugal compressor as a kind of rotating machinery,its running stability directly determines the performance of mechanical equipment,but because of mass eccentricity,bearing support of its own nonlinear factors such as unbalanced excitation seriously limited the development of centrifugal compressor.Therefore,it is particularly urgent to analyze the vibration characteristics of shafting considering the action of bearing oil film flow field.The traditional analysis of shafting vibration characteristics is based on the dynamic characteristic coefficients of plain bearings,which are the results of the idealized calculation of bearing structural parameters,which leads to the deviation between the theoretical prediction of compressor vibration characteristics and the actual operating conditions.Therefore,in this paper,a single axis five-stage centrifugal compressor is taken as the research object,and a coupling dynamics model of shafting including the oil film flow field is established.On this basis,the fluid-structure coupling between the oil film flow field and the rotor system is carried out,and the coupling vibration characteristics of shafting under the action of the oil film force is analyzed.Specific work contents and conclusions are as follows:(1)Make a comprehensive and com Parative analysis of the effects of cavitation effect,viscotemperature characteristics,oil film thickness and rotation speed on the bearing oil film carrying ca Pacity.Furthermore.At the same time,calculate the bearing state characteristic coefficient by Dy Ro Be S.The results show that bearing ca Pacity decreases with the increase of oil film thickness,and the effect of oil film thickness on bearing ca Pacity weakens with the increase of rotational speed.The bearing ca Pacity and the maximum pressure of the oil film decrease in different amplitude when the viscosive-temperature characteristic is introduced.The main stiffness coefficient of the bearing increases nonlinearly with the increase of the rotating speed,while the rest of the dynamic characteristic coefficients show a nonlinear decreasing trend with the increase of the rotating speed,and eventually all tend to be stable.(2)The Campbell diagram of shafting under different bearing support modes is calculated,and the results are com Pared with the test values,and the feasibility of using oil-film force-fluid-solid coupling method for bearing support simulation was determined.The variation of vibration characteristics of rotor system with bearing Parameters is investigated.The critical speed of rotor system decreases with the increase of bearing clearance(within 1%),while the shafting stability decreases first and then increases.In other words,the clearance ratio mainly affects the stability of shafting rather than the critical speed.With the increase of bearing width to diameter ratio,the first and second order critical speed of shafting increases in different amplitude,but the shafting stability does not change regularly with the increase of bearing width to diameter ratio,and the stability of shafting is the best when the bearing width to diameter ratio is 0.8.The critical speed of shafting decreases(by more than 10%)with the increase of bearing support s Pacing,which provides a new idea for adjusting the critical speed and stability of shafting.(3)The unbalance response of shafting is analyzed.The results show that the unbalance is proportional to the stability of shafting.Shafting is sensitive to different unbalance at different positions.Different combination modes of unbalance phase Angle and unbalance size have different effects on shafting stability.There is an optimal combination mode that makes shafting stability best.Therefore,the unbalanced vibration of shafting can be suppressed by adjusting the mounting Angle of the shaft components. |
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