Dynamic Analysis Of Air Compressor Rotor Considering The Effect Of Flange Bolt Connection

The new coal chemical coal-to-liquid and gas products can provide support and emergency guarantee for China's energy safety.The key to large-scale coal chemical processes is the air separation oxygen plant for which large compressors are the core device in air separation process.In engineering practice,beam-based shaft model is generally used for rotor dynamic analysis.However,it is not likely to combine the eigenvalue analysis considering the gyro effect with the nonlinear contact mechanics analysis,which becomes a difficult point in the actual rotor dynamic analysis.In this thesis,the bolt connection stiffness of the air compressor is studied.Based on the force characteristics of the bolt connection and considering the contact and friction effects of the bolt-flange joint,the stiffness parameters of the connection element are obtained.Instead of the bolt flange structure,the custom connection element is developed by ANSYS and embedded in the large air compressor.Then,dynamic analysis is performed on the rotor system.The main contents are as follows:Aiming at the thick flange-bolt connection in the rotor system of air compressor,a practical tool is developed to embed the bolt-connection stiffness into the rotordynamic analysis model.Considering the friction and contact problems of bolt and flange,the static analysis of single bolt flange under axial and transverse loads is studied,and the nonlinear displacement-force curve is obtained.The nonlinear mechanism is studied by the contour plot of stress,and the equivalent piecewise linear processing is carried out.A program in Fortran is provided in ANSYS for the connection element with UPFs tool.Then,the entire structure of bolt flange in the rotor of an air compressor is studied,and the stiffness curve of the integral bolt flange structure is obtained.According to the displacement method,the stiffness parameters are solved and put into the connection element to form the overall dynamic analysis model of the rotor.An error analysis of the stiffness parameters is carried out.Based on the dynamic model of the rotor of an air compressor,the dynamic characteristics of the rigid rotor structure and the embedded joint rotor structure are compared and analyzed.Modal analysis and harmonic response analysis are carried out to understand the influence of bolt flange structure on rotor dynamic model.Afterwards,the critical speed of different rotor systems is calculated respectively,and the API standard is checked through unbalanced response analysis of multiple operation conditions.Compared with the rigid rotor structure,the feasible range of operation speed of the rotor structure with connection el ement is smaller,which proves the risk of the critical speed check based on the rigid model,and also confirms the significance of studying the bolted flange connection structure of the rotor system.