基于电磁激励的柔性转子系统轴承等效参数辨识
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摘要
随着高端透平机械的发展,迫切需要准确预测转子系统的模态阻尼以确保在工作条件下稳定运行,而准确可靠的辨识出轴承的动力学性能参数是先决条件。通过电磁轴承作为激振器给柔性转子施加激励力,并综合多截面测点的转子振动信息准确识别转子的轴承参数。将转子-轴承系统转换为被控对象和控制器的闭环控制系统,从而把轴承参数的识别问题转为控制系统的控制器参数识别,解决传统识别方法转子轴承中心和振动位移测量点不一致的情况,并且可提高参数识别的准确度。建立高精度的转子有限元模型进行基于模型的参数识别,并开展试验研究以验证该方法的可行。通过使用识别的轴承刚度阻尼参数预测的转子稳定性参数(固有频率与对数衰减率)与通过传统的扫频激励的测量方法得到的结果相比较,验证该方法的准确性。该识别方法可为轴承参数的辨识提供便捷的方法并为提高高端透平机械的稳定性设计提供理论和技术基础。
With the increasing need for the high-end turbomachinery, an accurate prediction for mode damping is urgently needed to ensure the machinery stably operates under the operation condition, and the accurate and reliable prediction and identification of bearing dynamic performance parameters are the prerequisites. The magnetic bearing as the actuator is used to apply excitation force on the flexible rotor system, and the response vibration is measured to accurately identify the parameters of bearings. The rotor-bearing system is transformed to a closed-loop control system in which the rotor shaft and bearings are taken as controlled plant and controller respectively; thus, the identification of bearing parameters is transferred to the problem of identifying the parameters of controller in a control system. This transformation solves the problem that the measured sensor was not located at the center of the bearing pad in traditional method, and the information from multi-section sensors can be used to increase the identification accuracy. A high accurate finite element model is developed for the model-based parameter identification, and the experiment is also carried out to verify the feasibility of this method. The accuracy of this method is verified by comparing the rotordynamic stability parameters(natural frequencies and log decrements) which are predicted by the estimated bearing stiffness and damping, and the measured values estimated by the sine-swept excitation. This method can provide convenient method to identify the bearing coefficients and can provide theoretical and technical basis for the stability design of high-end turbomachinery.
With the increasing need for the high-end turbomachinery, an accurate prediction for mode damping is urgently needed to ensure the machinery stably operates under the operation condition, and the accurate and reliable prediction and identification of bearing dynamic performance parameters are the prerequisites. The magnetic bearing as the actuator is used to apply excitation force on the flexible rotor system, and the response vibration is measured to accurately identify the parameters of bearings. The rotor-bearing system is transformed to a closed-loop control system in which the rotor shaft and bearings are taken as controlled plant and controller respectively; thus, the identification of bearing parameters is transferred to the problem of identifying the parameters of controller in a control system. This transformation solves the problem that the measured sensor was not located at the center of the bearing pad in traditional method, and the information from multi-section sensors can be used to increase the identification accuracy. A high accurate finite element model is developed for the model-based parameter identification, and the experiment is also carried out to verify the feasibility of this method. The accuracy of this method is verified by comparing the rotordynamic stability parameters(natural frequencies and log decrements) which are predicted by the estimated bearing stiffness and damping, and the measured values estimated by the sine-swept excitation. This method can provide convenient method to identify the bearing coefficients and can provide theoretical and technical basis for the stability design of high-end turbomachinery.
引文
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[12]XU Y,ZHOU J,DI L,et al.Active magnetic bearings dynamic parameters identification from experimental rotor unbalance response[J].Mechanical Systems and Signal Processing,2016,83:228-240.
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[14]PAN X,WU H,GAO J,et al.Study on online active balancing system of rotating machinery and target control method[J].WSEAS Transaction on Systems,2014,13:302-311.
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[16]李启行,王维民,齐鹏逸,等.转子轴承系统稳定性分析与识别方法[J].机械工程学报2014,50(7):54-59.LI Qihang,WANG Weimin,QI Pengyi,et al.Stability analysis and identification method for rotor-bearings system[J].Journal of Mechanical Engineering,2014,50(7):54-59.
[2]DIMOND T,SHETH P,ALLAIRE P,et al.Identification methods and test results for tilting pad and fixed geometry journal bearing dynamic coefficients–a review,Shock and Vibration,2009,16(1):13-43.
[3]BENCKERT H,WACHTER J.Flow induced spring coefficients of labyrinth seals for application in rotor dynamics[C]//Rotordynamic Instability Problems in High-Performance Turbomachinery,1980,NASA Lewis Reserch Center,Ohio.1980:189-212.
[4]GOODWIN M,OGRODNIK P,ROACH M,et al.Calculation and measurement of the stiffness and damping coefficients for a low impedance hydrodynamic bearing[J].Journal of Tribology,1997,119(1):57-63.
[5]CHILDS D,HARRIS J.Static performance characteristics and rotordynamic coefficients for a four-pad ball-in-socket tilting pad journal bearing[J].Journal of Engineering for Gas Turbines and Power,2009,131(6):062502.
[6]DELGADO A,VANNINI G,ERTAS B,et al.Identification and prediction of force coefficients in a five-pad and four-pad tilting pad bearing for load-on-pad and load-between-pad configurations[J].Journal of Engineering for Gas Turbines and Power,2011,133(9):092503.
[7]JIANG G,HU H,XU W,et al.Identification of oil film coefficients of large journal bearings on a full scale journal bearing test rig[J].Tribology International,1997,30(11):789-793.
[8]SANTIAGO O D C,ANDRéS L S.Field methods for identification of bearing support parameters part ii:Identification from rotor dynamic response due to imbalances[J].Journal of Engineering for Gas Turbines and Power,2007,129(1):213-219.
[9]TIWARI R,LEES A,FRISWELL M.Identification of speed-dependent bearing parameters[J].Journal of S ound and Vibration,2002,254(5):967-986.
[10]ZHOU J,DI L,CHENG C,et al.A rotor unbalance response based approach to the identification of the closed-loop stiffness and damping coefficients of active magnetic bearings[J].Mechanical Systems and Signal Processing,2016,66:665-678.
[11]SANTIAGO O D,SAN An DRéS L.Experimental identification of bearing dynamic force coefficients in a flexible rotor further developments[J].Tribology Transactions,2007,50(1):114-126.
[12]XU Y,ZHOU J,DI L,et al.Active magnetic bearings dynamic parameters identification from experimental rotor unbalance response[J].Mechanical Systems and Signal Processing,2016,83:228-240.
[13]CLOUD C H.Stability of rotors supported by tilting pad journal bearings[D].University of Virginia,USA,2007.
[14]PAN X,WU H,GAO J,et al.Study on online active balancing system of rotating machinery and target control method[J].WSEAS Transaction on Systems,2014,13:302-311.
[15]WANG W,LI Q,GAO J,et al.An identification method for damping ratio in rotor systems[J].Mechanical Systems and Signal Processing,2016,68:536-554.
[16]李启行,王维民,齐鹏逸,等.转子轴承系统稳定性分析与识别方法[J].机械工程学报2014,50(7):54-59.LI Qihang,WANG Weimin,QI Pengyi,et al.Stability analysis and identification method for rotor-bearings system[J].Journal of Mechanical Engineering,2014,50(7):54-59.
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