Simulation And Optimization Of Wet Compression For Piston Compressor In Cold Storage

At present,piston compressors are used in most small and medium-sized cold storages in China,and many refrigeration equipment have been aging,which poses serious safety risks.When the compressor is in working state,the thermal load of the system,the liquid supply control valve,the return steam valve and so on will have obvious changes,or when the refrigerant filling capacity is too large,will cause the compressor wet compression,and even liquid strike phenomenon.A slight hydraulic strike will crush the suction and exhaust valves,while a severe blow will cause the piston,connecting rod or crankshaft of the compressor to deform and even damage the cylinder head.Just under the above context,this thesis is begun.The main purpose of this thesis is to study wet compression mechanism of compressor deeply,and to try to provide theoretical basis for avoiding liquid hammer through automatic control in the future.At the same time,in order to reduce the impact of wet compression,it is necessary to optimize the refrigeration system.Then,we can reduce the power consumption of compressor,improve the system cop.This thesis mainly consists in the following aspects:(1)Determining the gas-liquid two-phase flow patterns of compressor in the wet compression operation based on theory.The effect of rectifying is analyzed throng mesoscopic thermodynamics,and the feasibility of adding rectifying structure in the suction pipe of piston compressor is demonstrated.(2)Based on CFD technology,the working process of wet compression of piston compressor is simulated,and the variation rule of working medium in the cylinder of compressor is analyzed.(3)The change rules of the suction and discharge pressure,pressure ratio,the suction and discharge temperature,outlet temperature of thermal expansion valve,outlet temperature of condenser,outlet temperature of fan,electric current and voice are studied under normal working and wet compression conditions of the compressor before and after rectification.The results show that the effect of rectification is not good when the compressor works normally,and the rectification can improve the wet compression when the wet compression is more obvious.(4)The change rules of specific entropy,specific enthalpy of getter,specific enthalpy of exhaust gas,specific enthalpy of condenser,the dryness of the suction and discharge,the power consumption of compressor,and system cop are analysed under normal working and wet compression conditions of the compressor before and after rectification.The results show that the power consumption of the compressor can be reduced and the cop of the system can beincreased by rectifying whether the compressor works normally or under wet compression condition.