| Scroll compressor is a kind of fluid machinery widely used in air conditioning refrigeration,gas compression and pressurization,transportation and other fields.It has the characteristics of high efficiency,stable operation and low noise.It plays an important role in daily life and industrial production.Due to the machining,assembly errors and friction losses of the system parts,the gaps of different sizes appear in the moving pairs during the operation of scroll compressor,which leads to gas leakage or collision of moving and static scroll parts.The dynamic stiffness of the contact pair changes with the rotation of the crankshaft,which leads to vibration and noise in the rotor system,aggravates the friction and wear of zero components,and reduces the reliability and service life of the rotor mechanism.Therefore,dynamic analysis of contact pair of scroll compressor under time-varying stiffness and error conditions is carried out in this paper.The main research content of this paper is as follows:(1)Establishment of time-varying stiffness excitation model.Solidworks was used to draw the compressor rotor system model and complete the assembly.Based on Herts nonlinear elastic contact theory,the time-varying stiffness of the contact pair is obtained by using the finite element method and the energy method according to the periodic stress of the contact pair,and the time-varying stiffness periodic variation diagram was drawn to obtain the stiffness variation rule.The results show that the stiffness of the contact pair is affected by the gas force of the compression cavity and the complex profiles of the vortex disk.(2)Establishment of error excitation model.The expression form of error excitation is analyzed,and the possible error of electric scroll compressor is analyzed.The influence of rotor mass and position eccentricity on rotor subsystem is studied.in the eccentricity case,the electromagnetic gap between the rotor and the stator changes,the change of magnetic gap makes the radial magnetic force in the state of balance produce imbalance,Then,the law of unbalance magnetic tension was obtained,and the variation curve of unbalance magnetic tension was obtained by adding the unbalance magnetic tension into the system differential equation,and the three-dimensional model of error excitation was established.(3)Simulation analysis of rotor rigid-flexible coupling system with time-varying stiffness and error excitation.The rotor system model was imported into Adams for virtual assembly,and the system responses under different excitation were simulated.Firstly,simulation analysis of coupling time-varying stiffness and clearance excitation between drive bearing and crank shaft contact pair is carried out.The results show that: The impact force amplitude of the contact pair increases with the time-varying stiffness and clearance excitation.The impact force is 1.16 times of the fixed stiffness at the clearance of 0.003 mm,and the number of periodic collisions of the contact pair increases from 71 to 265.When the clearance is 0.01 mm,the contact pair collision force is close to the ideal state.Secondly,after the flexibility treatment of the main bearing,the dynamic response of the rotor subsystem under the error single excitation and the multi-excitation factors of comprehensive error and timely variable stiffness was analyzed.The results showed that the impact force on the main bearing of the rotor system under load was 1.014 times of that under no load,and the error caused the increase of the number of drive bearing collisions and aggravated its vibration.If the eccentricity radius and eccentricity Angle of the rotor are different,the dynamic phenomena are different.When the error is inevitable,the eccentricity Angle should be controlled to be opposite to the gravity direction of the rotor.In order to avoid the loss of stability of the scroll compressor under multiple excitation,the machining and installation errors of the rotor system should be reduced. |
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