Experimental Study On Dynamic Characteristics Of Micro Gas Turbine Gas Bearing Rotor System

Because of the energy storage shortage and high emphasis on environment protection,distributed energy supply system with energy conservation,environment protection,and high security becomes an important development tendency of future energy system.Micro gas turbine(MGT)has advantages of compact structure,high cycle efficiency,and large power density.These make the MGT attractive for the distributed energy supply system.The need for high performance and high stability leads the research on MGT becomes a world research hotspot.The MGT rotor system consists of single-stage radial compressor,turbine,high speed permanent magnet rotor and gas bearings.Because of low damping and low carrying capacity of the gas bearing,low frequency whirl,whip and other instability responses occur easily for the rotor system.It is valuable to do the research on how to improving the dynamic stability of gas bearing-rotor system by modifying components'parameters for stability and high performance of MGT rotor system.The main works of this paper are as following:1.According to Muszynska model,theoretical model of typical gas bearing rotor system is constructed.The influence of gas bearing rotor system stiffness and damping to rotordynamics are theoretically analyzed.Rotordyanmics of gas bearing rotor system with nitrile-butadiene "O,rings and fluorine rubber "O" rings supported respectively,and fluid circumferential average velocity of gas bearing with different radial clearances and rotor eccentricities are analyzed numerically.The results show that increasing the external damping of gas bearing system can help to reduce vibration amplitude.Improving rotor eccentricity with constant radial clearance or improving raidial clearance at constant eccentricity can decrease fluid circumferential average velocity,improve the stability of gas bearing-rotor system,and inhibit low frequency vibrations.2.Based on gas bearing rotor system test bench,experiments of rotor system with different materials "O" rings,different bearing radial clearances,axial clearances and different rated load are conducted.The results show that "O" rings with large stiffness and damping can help to inhibit low frequency whirl at the first bending critical speed and "O" rigns with small stiffness and damping can help to suppress low frequency oscillation at speed higher than the first bending critical speed.Decreasing radial clearance can help to eliminate the low frequency oscillation.Increasing rated load of high speed permanent magnet rotor leads to the increasing of unbalance magnet pull,results in the low frequency whirl changing into double low frequencies and rubbing deceleraton.3?Based on the conclusions of above researches,the micro gas turbine rotor system with appropriate parameters is designed and the testrig is constructed.The static characteristics experiments are conducted to explore the gas bearing supply pressure scheme.Dynamics of MGT rotor system with different state parameters and structural parameters,coupling of rotor dyanmics with electricity parameters are researched and effective measures to improving the rotordyanmic stability are put forward.Compressor surge,tripping speed,self sustaining speed,rub impact fault characteristics are experimently researched and coupling of rotor dynamics with electricity and thermaldyanmic parameters are studied in hot experiments.The experiments show that the outlet pressure of compressor fluctuates at compressor surge speed and it cann't affect the rotor radial responses;the step change of fuel flow rate and pressure leads to rotor rubbing and instability;the drive current increases at the critical speed and rubbing speed.