Simulation Study On Dynamic Characteristics Of Valve And Crankshaft Components Of Reciprocating Compressor Under Variable Operating Conditions

Reciprocating compressor has been widely used in petroleum and petrochemical industry,and plays an extremely important role in the process of petrochemical refining and natural gas pipeline transportation.The reciprocating compressor is a positive displacement compressor with fixed flow rate and high power consumption.The stepless gas volume regulation system can make it operate under variable load to meet different process gas demand.However,after the gas valve and crankshaft of some large compressors are introduced into the gas volume regulation device,the force state of the compressor changes due to the change of gas force in each cylinder,As a result,the incidence of crankshaft failure,Bush burning,valve rupture or valve leakage increases,resulting in unpredictable economic losses.Aiming at the problem that the failure rate of gas valve and crankshaft of large compressor increases after the introduction of gas regulating device,the influence of gas regulating system on the characteristics of reciprocating compressor and the causes of failure are deeply studied through mechanical analysis and computer modeling and simulation technology.This paper mainly studies the following aspects(1)The finite element model of reciprocating compressor valve and unloader was established,and the movement law of valve and unloader under variable working conditions was analyzed by transient dynamics analysis software workbench/LS-DYNA,as well as the movement and strength characteristics of unloader under two kinds of limit modes of valve plate and valve seat.(2)Aiming at the dynamic characteristics of crankshaft,the core transmission part of six cylinder multi-stage double acting reciprocating compressor,under the condition of air volume regulation,the mechanical model of transmission mechanism is constructed,and the variation law of whole cycle alternating load of crankshaft under the condition of variable working conditions is analyzed.In this paper,the deformation,static strength and fatigue strength characteristics of connecting rod journals at all levels during the off design operation of crankshaft are checked and analyzed by using finite element method.It is proposed that the load regulation range for effectively avoiding premature fatigue fracture of crankshaft is 20～40%.(3)The dynamic load change of the crankshaft when the load adjustment of the crankshaft within and between the stages is deviated is calculated by the mechanical model.The deformation and strength characteristics of the crankshaft under normal and fault conditions are studied by the multi-body dynamics rigid-flexible coupling analysis method.Based on this,it is proposed that the allowable intra-stage load adjustment deviation of the unit is within 15%and the inter-stage load adjustment deviation 10%when the load adjustment deviation occurs due to a fault.The research results of this paper reveal the law of motion and characteristic changes of the actuator,intake valve and transmission mechanism of the reciprocating compressor under variable working conditions,and put forward an effective way to extend the life of the unloader and valve plate of the reciprocating compressor.The optimal load control interval of the compressor under normal load regulation and fault conditions,and provides a theoretical basis for the subsequent parameter optimization of the key components of the compressor.