Dynamic Characteristics And Reliability Analysis Of Transmission System Of Nitrogen Generating Unit

In the process of oil and gas storage and transportation,chemical process,natural gas exploitation and other processes,the use of nitrogen is increasing,making nitrogen production equipment play an increasingly important role in production.As the core component of the nitrogen generator transmission system,the transmission shaft is subjected to alternating load that changes periodically with time and direction during the operation of the unit.Due to t alternating load,the transmission shaft generates vibration,bending,fracture and other failure modes.Therefore,the dynamic characteristics of the shafting system not only affect the service life of the transmission shaft,but also directly affect the safety and stability of the unit,it will also have a significant impact on other parts of nitrogen production equipment.This paper mainly deals with failure analysis and shafting dynamics of nitrogen generator transmission system based on several shaft breaking accidents.As shown in the following major elements.The 3D modeling software Solid Works is used to build the assembly model of the drive shaft,diaphragm coupling,clutch and reciprocating compressor.Then importing the model into the finite element software ANSYS Workbench for static analysis.It is concluded that the maximum equivalent stress is 60.94 MPa,and it can be judged that the transmission shaft meets the static strength requirement.Obtaining the first 8th mode shape and natural frequency by using ANSYS Workbench to perform free modal analysis of the drive shaft.And performing resonance analysis to determine that the transmission system is not in the resonance zone and provide parameters for dynamic analysis and reliability assessment.The multi-body dynamics model of the assembly model was created by the multi-body dynamics software Recur Dyn.Then the elastic diaphragm was simplified into a spring,and the crankshaft and the drive shaft were simplified into a finite element flexible body to obtain a rigid-flexible coupled dynamic model.Through the simulation analysis,the kinematic parameters and dynamic parameters of the unit are obtained,and the stress,strain and deformation of the shaft system can be obtained.The calculation of Recur Dyn shows that the local stress concentration occurs when the transmission shaft is subjected to alternating load,and the maximum stress is 228.56 MPa.In addition,combining with system engineering,the reliability evaluation index system is established from the perspectives of personnel,transmission system status,infrastructure,environmental factors,management factors and maintenance status.In order to reasonably assign the index weights,this paper uses the combination of subjective weighting and objective weighting to calculate the weight coefficient of each index.Based on the characteristics of qualitative analysis and quantitative evaluation of extenics,the reliability of transmission system is qualitatively and quantitatively evaluated.