Study On Vibration Characteristics Of Centrifugal Pump Induced By Shafting Misalignment

The research was carried out under the support of the Zhenjiang Key Research and Development Program?GY2017001?and the project“Low Noise Manufacturing Technical Service of Vane Pump”?20190383?hosted by China Shipbuilding Industry Corporation 719.Centrifugal pump is a common rotating mechanical equipment.Due to installation errors,structural deformation after work and foundation settlement,there will be various degrees of misalignment in the rotor system.A series of dynamic effects harmful to the equipment will occur during the operation of the centrifugal pump due to the misalignment error fault,such as coupling connection bolt hole wear,oil film instability,shaft bending deformation,and so on.These dynamic effects lead to abnormal vibration of the system,and great harm.The misalignment of the rotor system is mainly divided into bearing misalignment and shaft misalignment?also known as coupling misalignment?.At present,great progress has been made in bearing misalignment control?such as automatic centering bearing,cold elevation pre-compensation,etc.?.However,the misalignment of shafting is a key problem that needs to be solved urgently at present,because the axis lines of two adjacent rotors do not coincide in the actual operation,even through the elastic coupling,it cannot be completely avoided,and the research on the vibration law and control of the misalignment system of the centrifugal pump is relatively lagging behind.Therefore,it is of great theoretical and practical value to study the causes and characteristics of centrifugal pump shaft misalignment fault in order to improve the reliability,vibration control and fault diagnosis of centrifugal pump unit.Now,theoretical derivation,test and simulation are combined to study the vibration characteristics of centrifugal pump when the transfer subsystem and shafting are out of alignment.The main research contents and conclusions are as follows:1.The research status and development trend of rotor system misaligned vibration mechanism,vibration characteristics and vibration characteristics of centrifugal pump with shaft system failure are summarized,and the significance of this research is expounded.2.Causes and vibration mechanism of misalignment in the rotor system of centrifugal pump was studied,fault rotor motion equation is established,the expression of misaligned exciting force was deduced.Moreover,the mechanical model and finite element model of the centrifugal pump rotor system in the misalignment are established based on the structure and mechanical characteristics of the rotor system of the centrifugal pump.The above work provides theoretical basis and analytical model for the follow-up study of vibration characteristics of the misaligned rotor system.3.The test bed of centrifugal pump external characteristics and shafting misalignment vibration is built,based on the test results,the influence of the flow field on the vibration of the centrifugal pump rotor system with different degrees of misadjustment is analyzed,and then solution strategy of the flow field calculation and the finite element calculation are determined.The results show that:?1?the established flow field calculation model is reasonable.Under the design condition,the head error is2.4‰and the efficiency error is 1.35%.?2?when the shafting is out of alignment,the vibration response of 1APF?Rotating frequency of motor?is enhanced,and the response of 2APF is obvious.The low-frequency vibration energy of the centrifugal pump increases,and the vibration level is significantly increased.?3?the flow field has little influence on the vibration change of centrifugal pump with misaligned rotor system.4.The dynamic model of the rotor system of the centrifugal pump was established,and the influence of the misaligned form,misaligned degree and speed of the rotor system on the vibration characteristics of the centrifugal pump was analyzed.The results show that:?1?at the rated speed,the main frequency of the parallel misaligned radial vibration is 2APF,and there is no axial vibration;The radial and axial vibration of angular misalignment showed obvious 2APF characteristics.When the angular misalignment was enlarged to 2°,the dominant frequency changed from 1APF to 2APF.In the synthetic misalignment,when the parallel misalignment is the smallest and the angular misalignment is the largest,the proportion of 2APF component is the largest.?2?the characteristic peak increases linearly with the increase of misaligned degree;?3?the main frequency of the misaligned rotor system is 1APF at low speed?n'/n?0.9?,and 2APF at high speed?n'/n?1?.?4?misalignment distorts the axis trajectory from an ellipse to a banana shape,and in severe cases,it is an inside figure 8.5.The finite element analysis model of the centrifugal pump was established and the vibration characteristics of the centrifugal pump were revealed under different centering states of the rotor system.The analysis results show that:?1?under the ideal alignment of the shafting,the shafting excitation source mainly causes the horizontal vibration of the inlet and outlet flanges of the centrifugal pump and the vertical vibration of the base accompanied by the main frequency of 1APF.The vibration intensity order of each measurement point is:the outlet flange M₂>inlet flange M₁>base M₃;?2?when the shafting is not parallel,the main frequency of horizontal and vertical vibration of M₁ and M₃ is 2APF,the main frequency of horizontal vibration of M₂ is 2APF,and the main frequency of vertical vibration is 1APF.The order of vibration intensity of each measurement point is:M₂>M₁>M₃.?3?when the misalignment angle is small,the main vibration frequency of each measurement point is consistent with the parallel misalignment.With the increase of the angular misalignment amplitude,the main frequency becomes the modal frequency.When the amplitude is?1°,the vibration intensity of each measurement point is ranked as:M₁>M₂>M₃.?4?the parallel misalignment of the rotor system mainly affects the vibration of M₂,and the misalignment of the angle affects the vibration change of M₁.The vibration level increases with the increase of the misalignment,and the growth rate is first fast and then slow.