| Reciprocating compressor is widely used in petroleum,metallurgy,chemical industry,natural gas transportation and other industrial fields.In view of the reciprocating compressor belongs to the positive displacement compressor,the design value of the compressor's exhaust volume has a margin.The exhaust volume is a fixed value.When the end process demand of the compressor fluctuates and the intake volume of the source is unstable,it is required that the compressor should have a good control function of the exhaust volume.In recent years,more and more compressors are equipped with part of the stroke into the valve capacity control system.The energy saving effect is obvious.However,the domestic and foreign stepless capacity control system which has been successfully applied has some problems,such as high cost,complicated structure of key mechanical components,high difficulty in inspection and maintenance,and blockade of technical achievements.The actuator of the stepless capacity control system determines the reliability of the system and the actual control effect.Theoretical research on the actuators of the capacity control system is deeply studied by domestic researchers,including working principle,transient characteristics of the valve,analysis of parameter impact and optimization.However,most traditional design methods of the actuator are single-objective optimization,and the optimization of a single parameter may lead to the degradation of other parameters,and the optimization design is limited.Moreover,the margin of traditional design is large,and the cost of system and the design is difficult.Therefore,the study of actuator performance and multi-objective optimization technology is of great significance for the low cost,high reliability and high safety of reciprocating compressor stepless capacity control system.In this paper,the key mechanical components of the reciprocating compressor stepless capacity control system are studied.The mathematical model of the actuator and the working model of the compressor under capacity regulation control conditions were established,the correlation among the multi-parameters of the stepless capacity regulation system was analyzed,the parameter calculation and structural design of the actuator prototype were completed,and a multi-objective optimization method of the actuator parameters based on NSGA-? was proposed.The performance and reliability experiments of the actuator were carried out,and the theoretical research results were verified.Through experiments and engineering application research,a self-recovery control method based on adaptive optimization compensation of control parameters is proposed for the regulation instability fault of stepless gas volume regulation.The research results of this paper play an important role in improving the design level of stepless capacity regulation system and enhancing the practicability of the system.Specific research contents are as follows:Firstly,the working model of reciprocating compressor under different working conditions is constructed,and the working model of the actuator including oil pressure,cylinder pressure,reset spring force and valve plate force is established,the motion equation of the actuator parameter design is obtained,and the relationship among the parameters is revealed.By integrating the motion equation of the actuator into the working model of the compressor,the working model of the compressor under the condition of capacity regulation is constructed,the influence of the actuator parameters on the working cycle of the compressor is analyzed,and the cylinder pressure corresponding to different withdrawal speeds is simulated.Further,the 3D model of compressor cylinder and valve was built by CFD to simulate the cylinder pressure under different backflow clearance,and the relationship between backflow clearance and the resultant force of valve plate was obtained.Secondly,based on the parameter analysis of the mathematical model of the actuator,the DW2/12 reciprocating compression test bench is taken as the design object.An oil cylinder for gas-liquid separation and an unloader which can prolong the life of the valve are designed under the premise of meeting the control and use requirements.Finally,the design requirements of the actuator such as high frequency action,sealing and reliability are realized.A set of actuators were developed to meet the requirement of stepless capacity regulation.Based on the actuator prototype system,the performance and reliability experiments of the actuator were carried out to verify the correctness and feasibility of the mathematical model and structural design.Then,in view of the relationship between the key parameters of the actuator and the hydraulic system of the reciprocating compressor stepless capacity control system,the traditional method cannot obtain the optimal solution of multiple parameters.Taking the actuator and reciprocating compressor as the research objects,based on the model of actuator and reciprocating compressor,the spring stiffness,hydraulic force,impact velocity and deviation value of indicating power were taken as objective functions to carry out the multi-objective optimization research on the actuator based on NSGA-? method.The proposed method can solve the problem of parameter optimization design of stepless capacity control system,which makes the stepless capacity control system run safely and efficiently,and lays a foundation for the overall optimization design of the capacity control system.Finally,the multi-objective optimized design of the actuator has been successfully applied in domestic petrochemical enterprises,achieving good effects of control and energy saving.High frequency action of actuator and solenoid valve causes fatigue,wear and other deterioration of moving parts.Fatigue of spring,parameter deviation of electromagnetic valve and so on lead to the instability of capacity control.The multi-parameter dynamic feedback model is adopted to realize the fault diagnosis and fault type identification.This paper presents a self-recovery control method based on neural network for actuator failure of capacity control system.The experimental results show that the proposed self-recovery control method can actively apply the compensation amount of control parameters after the occurrence of instability fault,so as to restore the capacity control system to the normal state and realize online fault self-recovery. |
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