Vibration Characteristics Of Typical Fault Shell Of Small Hermetic Compressor

As the power source and heart of refrigeration equipment such as refrigerators and air conditioners,the working state of hermetic reciprocating compressors can interfere with the performance of refrigerators directly.Vibration is an inevitable phenomenon in the working process of compressors,and the vibration information contains a wealth of information about the state of operation.Changes of compressor performance can be expressed through vibration.Hermetic reciprocating compressor has a complex structure with many vulnerable parts,and the vibration response corresponding to the fault is complex.Once the fault occurs,there will be a lot of impact and friction,and the running speed will become very unstable,and the load will constantly change,which can cause serious damage to the equipment.Through lots of experiments,the correlation between the vibration performance of typical component faults at different measuring points and in different directions is studied in this paper.The vibration position,vibration signal and other characteristic relations of typical faults of compressor parts are analyzed.The main work and achievements are as follows:(1)Four algorithms of signal time from domain transform into frequency domain were studied,the simulation and performance of several algorithms were compared,and then the chirp Z transform was selected as the frequency refinement algorithm.(2)The rigid-flexible coupling model of the key transmission mechanism of the compressor was established according to the connection relationship among the parts of the compressor.The force of the key transmission mechanism on the seat spring was solved by simulation.(3)The finite element model of the compressor shell was established,and the natural frequency and mode of compressor were solved by modal analysis.The displacement distribution of the shell vibration response of the key transmission mechanism of the compressor was solved based on the modal analysis results of the compressor via the modal superposition method with the force of the spring as the excitation,which provides a theoretical basis for the distribution of the experimental points.(4)The test platform for vibration characteristics of hermetic compressor was set up.The typical fault types of the hermetic reciprocating compressor were set,that is,the crank contacts the internal exhaust pipe,the support spring shedding,inadequate installation of suction muffler and foreign body of suction valve.The vibration measurement points were distributed on the top and side of the compressor shell according to the simulation results of vibration response and the direction of vibration.The vibration signal of shell of 5 compressors under no-load condition were measured by programming.(5)The vibration characteristics of typical faults in the time domain and the location of the measuring points were obtained via comparing and analyzing the time domain signals of several measuring points.The vibration characteristics of typical faults in frequency domain were obtained by transforming the selected measuring points to frequency domain for further analysis.The fault mechanism was analyzed by combining the time-frequency domain fault characteristics of the fault component vibration signal.The mapping relationship between four typical faults and the vibration characteristics of compressor shell was established based on the above research.The best fault monitoring point corresponding to each typical fault was obtained according to the intensity of mapping of each distribution measuring point.The fault diagnosis method of the compressor crank contacting internal exhaust pipe,the support spring shedding,the suction muffler installation not in place and foreign body on suction value were proposed.The research results of vibration characteristics of typical fault shell of hermetic compressor can not only guide the judgment of faults and the selection of fault monitoring points in the production process of small hermetic compressor,but also judge the corresponding fault types of compressors according to the fault characteristics.It greatly saves the time of compressor fault diagnosis and improves the production efficiency of compressor.