Dynamic Characteristics Of Reciprocating Compressor Pipeline And Engineering Application

As essential powered equipment in natural gas industry,reciprocating compressors are widely used for natural gas exploitation,gathering,processing and other fields.However,pipeline connected to reciprocating compressor always has vibration because of the intermittent suction/discharge flow in compressor.An excessive pipe vibration could cause an increase in the power consumption of compressor,fatigue damage for pipe and piping accessories,distortion of test instruments,an increase in noise,pipeline rupture,gas leakage,pipe explosions and other accidents.At present,engineers put much emphasis on pipe process design,give little attention on the relationship between compressor operating condition and pipeline design,rarely think about the dynamic characteristics of pipeline.Thus,there are many problems due to no FSI(fluid structure interaction)analysis of compressor pipeline and construction defects.In this paper,a comprehensive research on the dynamic characteristics of pipeline,the dynamic characteristics of fluid in pipe,and FSI pipeline vibration are conducted on the basis of the typical L-type,?-type and spacial pipe in 3D.The effects of pipeline structure parameters,pipeline material parameters and fluid parameters on the FSI dynamic characteristics of pipeline are investigated based on sensitivity analysis method.A vibration analysis method of compressor pipeline is proposed to provide theoretical guidance for compressor pipeline vibration reduction and analysis.The research contents are as follows.(1)Research on dynamic characteristics of pipeline.Based on the force balance condition of pipe,the mode shape,frequency equation,and displacement-frequency response function of uniform cross section pipe with different constrained boundary conditions are obtained.The first six natural frequencies and mode shapes of fixed-fixed pipeline,and the displacement-frequency response curve of fixed-free pipe are solved theoretically and numerically.The influences of pipe structural parameters and material parameters on the modal characteristics and frequency response characteristics of pipeline are studied,which relationships among them are obtained by parameter sensitivity analysis.(2)Research on dynamic characteristics of fluid in pipe.The generation and propagation mechanism of gas pulsation in pipe are analyzed on the basis of the working principle of reciprocating compressor.By analyzing the transfer matrix of pipeline components,the acoustic frequency characteristics of typical piping component are studied.The effects of the pipe structure parameters and fluid parameters on the dynamic characteristics of fluid in pipe with steady flow boundary conditions are studied.The relationships among the velocity amplitude,frequency and pressure amplitude of pulsating flow in pipe are obtained with unsteady flow boundary conditions.(3)Study on FSI vibration of pipeline and fluid.The axial motion and radial motion equations of fluid in pipe,the axial motion and radial motion equations of pipe are established.Then,the FSI equations of pipe and fluid in pipe are obtained.The influences of fluid pressure,velocity,density and viscosity on the modal characteristics of pipeline when considering FSI of pipe and fluid are studied.The relationships among fluid pressure,flow velocity and the RMS(root meam square)value of total pipe vibration velocity,and the effects of pipe structural parameters and fluid parameters on the vibration response of pipe under steady flow boundary are obtained.The relationships among velocity amplitude,frequency of pulsating flow in pipe and total vibration velocity of pipe are gained.The relationships among pressure amplitude,frequency of pulsating flow in pipe and total vibration velocity of pipe are obtained.(4)Pipe vibration analysis method and field application.By combining pipeline process design with its dynamic characteristic,dynamic characteristic of fluid in pipe,and FSI vibration of pipeline and fluid,a pipeline vibration analysis method of pipe connected to compressor are proposed.Due to the occurrence of abnormal vibration of reciprocating compressor inlet pipelines during the commissioning of a booster station,the root cause of severe vibration problem is diagnosed,which included modal analysis,resonant piping length calculation,velocity frequency spectrum analysis,and pressure pulsation measurement.Three elimination countermeasures against vibrations of pipe are developed.Pipe vibration response analysis for each countermeasure is evaluated under the maximum production capacity of compressor by vibration analysis method.Then a recommended vibration reduction measurement is proposed.After remodeling of pipe,the vibration level of the inlet piping system is reduced to an acceptable level defined by API 618 standard.The application results show that the vibration analysis method of pipeline in the paper is practicable.