Study On Rotating Stall And Surge Fault Mechanism Modeling And Response Characteristics Of Certain Aero Engine Rotor System

Aero-engine is the power plant of the aircraft. With its continuous improvement of modern aviation technology, aero-engine's structure is becoming more and more complicated, moreover, severe working conditions increase engine failure incidence such as rotating stall and surge which has become the major cause of threat of flying safely.Therefore, this dissertation focuses on studying rotating stall and surge fault on a certain aero-engine to analyze factor's sphere of influence and extract fault characteristics, moreover, the influences of faults upon the stability of rotor systems has been studied simultaneously.Based on the structure of the compressor, the surge model has been proposed and affecting factors such as throttle parameter, B parameter, rotor speed, time delay parameter have been calculated and analysed separately to extract critical parameters. Secondly, using stability and bifurcation theory, we derive the expression of critical B-parameter precisely, moreover, we propose a new method of monitoring surge by using all states crB parametric surface. In addition, the surge boundry is obtained based on B-parameter to the further precaution of surge.Rotating stall is an auspice signal of surge, so stall model has been set up to analyse responses of rotating stall for diagnosis based on method of discretization. The expressions of radial force and tangential force excited by the fluctuation of pressure and flow coefficient according to the distribution characteristics has been proposed to constitute stall transverse load in the whole cross section of compressor. Furthermore, based on analysis and calculation of stability of small perturbation, critical inlet angle and critical flow coefficient is derived as rotating stall boundry which provides reference for rotating stall fault precaution and monitoring.Given that rotating stall fault on engine rotor vibration characteristics have obvious reaction. Based on the structural features of a certain twin-spool-aero-engine without intermediate bearing, this dissertation sets up a single-rotor-support system and dual-rotorsupport system coupling with case respectively to analyse the impact on rotor's vibration whenever the stall fault occurs, building on the study of rotating stall mechanism combined with Newton's law of motion and rotor dynamics. It indicates that vibration of compressor caused by stall is nonlinear and mainly low frequency; different components of compressors in the event of rotating stall can cause various characteristic responses of vibration on rotors and case. This dissertation provides a certain basis and methods for reference for aircraft engine design and vibration monitoring.