Study On The Stability Evaluation And Instability Fault Diagnosis Of The Centrifugal Compressor

With the pressure, power and speed of centrifugal compressor increasing,the stability of compressor is becoming more and more important. Theinstability fault of centrifugal compressor occasionally happens, which canbring serious economic loss to the turbomachinery end-users. Therefore, howto evaluate the rotor stability during operation and how to identify potentialinstability during operation are becoming the problems to be solved for thecompanies. The paper studies the methods of identifying the damping of rotorsystem under operational condition which is the key to evaluate stability of thecentrifugal compressor. Meanwhile, according to the feature of instability, asystem is developed to identify potential instability. The main contributions ofdissertation are summarized as follows:1. Based on the half-power point method and by applying twosynchronized unidirectional trigonometric forces using AMB, the rotationfrequency-sweep force which has the same direction with the speed isconstructed and a forward frequency-sweep rotating incentive is formed. Amethod of half power points, which is based on forward frequency-sweeprotating incentive to identify the first forward damping of the rotor-bearingsystem, is presented. The feasibility and correctness of this method has beenconfirmed by theoretical analysis, numerical stimulation and experimentalanalysis.2. By employing theoretical analysis, numerical stimulation andexperimental analysis, A method to identify the damping ratio for arotor-bearing system based on BAR model is studied. The singular valuedecomposition and the unit circle in z-plane are used to distinguish the realmodals and noise modals, and the de-noising threshold which has a greataffect on parameter identification accuracy is introduced. All the analysis results could provide a good foundation for the further application research ofthis method.3. The method of identifying potential instability is studied and a methodof fault diagnosis for identifying instability is finally formed, which is basedon analysis of the characteristics of vibration and fault instability diagnosis.By employing this method, the reliability of the instability diagnosis could beimproved.4. According to the actual needs, the subsynchronous vibrationsrecognition and the stability diagnosis system is completed and is proved to beeffective. And this system could deal with various data acquisition no matterin the industry or in the laboratory environment.