The Analysis On The Dynamic Characteristics Of The Motor-driven Reciprocating Compressor

In the process of chemical technology,oil and gas storage and transportation,natural gas mining and so on,reciprocating compressor is mainly used to provide high pressure gas.As one of the most important parts of reciprocating compressor,it is subjected to cyclic alternating load during the operation of reciprocating compressor unit,whose magnitude and direction vary with the crankshaft angle.Besides,with the increasing demand of super large and multiple columns reciprocating compressor,the shaft system of unit has smaller stiffness and uneven mass distribution,resulting in reduction of natural frequency.If the speed of unit is within the critical speed range,it may occur resonance of the shaft system and even cause the failure of shaft system.According to the standard of API,users should adjust the working condition with the vibration analysis report made by manufacturer to avoid resonance,which has a good guiding significance for ensuring the normal operation of unit.According to the process parameters and natural gas composition of the compressor,the suitable compressor,coupling and driving machine are selected through thermodynamic calculation,and then the kinematic parameters and dynamic parameters of the unit can be obtained.The assembly model of reciprocating compressor,diaphragm coupler and three-phase asynchronous motor is built by using 3D modeling software Pro-E.Then,the model is introduced into the finite element software ANSYS Workbench,the statics analysis of the crankshaft and the rotor shaft of the reciprocating compressor can be made to judge the crankshaft and rotor shaft of the unit to meet the static strength requirements.The free modal analysis of crankshaft and motor rotor shaft of reciprocating compressor is carried out by using finite element software ANSYS Workbench,and the inherent characteristics are obtained.In addition,the selection software of Ariel Performance is used to analyze the working conditions and get the load data needed for vibration analysis.In addition,the equivalent rotational inertia of the shaft system of the unit is obtained in Pro-E,the equivalent stiffness of the shaft system is obtained in the ANSYS Workbench.The centralized mass model of the shaft system is established,the free vibration analysis is carried out by ANSYS APDL,and the critical speed and modal shape of the unit can be obtained,which can judge the unit to meet the speed requirements.The multi-body dynamics model of reciprocating compressor unit is established by RecurDyn,then convert the rotor shaft,crankshaft and elastic diaphragm into flexible bodies.Finally,the rigid-flexible coupling dynamic model is obtained.Through the simulation analysis,the kinematics parameter and dynamics parameters are obtained.Besides,the stress,strain and deformation of crankshaft and the rotor shaft can be obtained.Finally,it can predict that the unit meets the dynamic strength requirement.