磁流体动压润滑机械密封的自适应控制方法研究
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摘要
基于磁流体的黏度受磁场强度控制这一特性,设计一种采用磁流体作为润滑介质的流体动压润滑机械密封结构,并提出密封性能的自适应控制方法。设计的自适应控制系统主要由参数监控系统、粗调系统、微调系统和补液系统组成。粗调系统可缩短自适应系统的响应时间,而微调系统可提高调节精度,两者结合,可保证密封系统的稳定性;控制系统通过比较液膜压力和被密封介质的压力,来判断密封性能是否满足要求;若侦测到动环转速或被密封介质压力发生变化,系统则会根据预置的策略调节磁场发生器的电压以改变磁流体黏度,进而调节液膜压力,同时调节磁流体的输入流量,根据工况波动实时地调节机械密封的密封性能。以煤油作为基载液,对控制程序进行了测试,测试结果表明,该控制程序能精确调节机械密封的密封性能。
Based on the characteristic of magnetic fluid whose viscosity can be manipulated by external magnetic field,a mechanical seal hydrodynamically lubricated by magnetic fluid was developed and the adaptive control method of sealing performance was proposed.The adaptive control system designed is mainly composed of parameter monitoring system,coarse adjustment system,micro-adjusting system and fluid replenishing system.The coarse adjustment system can shorten the response time of the adaptive system,while the micro-adjusting system can improve the precision of adjustment.The combination of them can ensure the stability of the sealing system.By comparing the pressure of lubrication film and the pressure of sealing medium,the control system can judge whether the sealing performance of the mechanical seal can meet the sealing requirement.If the rotational speed of rotating ring or the pressure of sealing medium are changed,the system will adjust the voltage of the magnetic field generator according to the preset strategy to change the viscosity of the magnetic fluid,so as to regulate the hydrodynamic pressure of the liquid film and adjust the input flow rate of the magnetic fluid.Then the sealing capability of the mechanical seal can be adjusted according to fluctuations of operating conditions in real time.The control program was tested with kerosene as base fluid.The test results show that the control program can accurately adjust the sealing performance of mechanical seals.
Based on the characteristic of magnetic fluid whose viscosity can be manipulated by external magnetic field,a mechanical seal hydrodynamically lubricated by magnetic fluid was developed and the adaptive control method of sealing performance was proposed.The adaptive control system designed is mainly composed of parameter monitoring system,coarse adjustment system,micro-adjusting system and fluid replenishing system.The coarse adjustment system can shorten the response time of the adaptive system,while the micro-adjusting system can improve the precision of adjustment.The combination of them can ensure the stability of the sealing system.By comparing the pressure of lubrication film and the pressure of sealing medium,the control system can judge whether the sealing performance of the mechanical seal can meet the sealing requirement.If the rotational speed of rotating ring or the pressure of sealing medium are changed,the system will adjust the voltage of the magnetic field generator according to the preset strategy to change the viscosity of the magnetic fluid,so as to regulate the hydrodynamic pressure of the liquid film and adjust the input flow rate of the magnetic fluid.Then the sealing capability of the mechanical seal can be adjusted according to fluctuations of operating conditions in real time.The control program was tested with kerosene as base fluid.The test results show that the control program can accurately adjust the sealing performance of mechanical seals.
引文
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[2]彭旭东,王玉明,黄兴,等.密封技术的现状与发展趋势[J].液压气动与密封,2009,29(4):4-11.PENG X D,WANG Y M,HUANG X,et al.State-of-the-art and future development of sealing technology[J].Hydraulics Pneumatics and Seals,2009,29(4):4-11.
[3]孙见君,何小元,魏龙,等.接触式机械密封端面经济加工分形维数[J].摩擦学学报,2010,30(4):414-418.SUN J J,HE X Y,WEI L,et al.Fractal dimension of seal end face for cost-effective finishing contacting mechanical seals[J].Tribology,2010,30(4):414-418.
[4]魏龙,顾伯勤,孙见君,等.机械密封端面摩擦机制与摩擦状态[J].润滑与密封,2008,33(6):43-46.WEI L,GU B Q,SUN J J,et al.Friction mechanism and friction state of end face of mechanical seals[J].Lubrication Engineering,2008,33(6):43-46.
[5]王之珊,陈建平,赵丕智.一种新型组合密封系统的实验研究[J].北京航空航天大学学报,2000,26(4):451-453.WANG Z S,CHEN J P,ZHAO P Z.Experimental Study on a New Type of Combined Seal System[J].Journal of Beijing University of Aeronautics and Astronautics,2000,26(4):451-453.
[6]范浩亮,周剑锋,汪宇.磁流体润滑非接触式机械密封系统的设计分析[J].润滑与密封,2016,41(1):90-95.FAN H L,ZHOU J F,WANG Y.Design of non-contact mechanical seal lubricated by magnetic fluid[J].Lubrication Engineering,2016,41(1):90-95.
[7]郝木明.机械密封技术及应用[M].北京:中国石化出版社,2010.
[8]周剑锋,顾伯勤.机械密封环的传热特性分析[J].机械工程学报,2006,42(9):201-206.ZHOU J F,GU B Q.Heat transfer characteristics analysis of rings of mechanical seal[J].Journal of Mechanical Engineering,2006,42(9):201-206.
[9]唐龙,卢利平,岳恩,等.磁流变液的研究与应用[J].重庆理工大学学报,2013(12):44-48.TANG L,LU L P,YUE E,et al.Research and applications of magnetorheological fluids[J].Journal of Chongqing University of Technology,2013(12):44-48.
[10]邹继斌,陆永平.磁流体密封原理与设计[M].北京:国防工业出版社,2000.
[11]池长青,王之珊,赵丕智.铁磁流体力学[M].北京:北京航空航天大学出版社,1993.
[12]张文格,李永泰,李鲲.机械密封环端面变形的有限元计算及实验研究[J].石油化工设备,1993(4):33-36.ZHANG W G,LI Y T,LI K.Calculation on sealing face deformation of mechanical seal ring by finite element method and lts experimental research[J].Petrochemical Equipment,1993(4):33-36.
[13]顾伯勤.流体力学[M].北京:中国科学文化出版社,2006.
[14]周剑锋.机械密封中的热流体动力效应研究[D].南京:南京工业大学,2006.
[15]BEHERA L,GOPAL M,CHAUDHURY S.Inversion of RBFnetworks and applications to adaptive control of nonlinear systems[J].IEE Proceedings-Control Theory and Applications,1995,142(6):617-624.
[16]WISE K A,LAVRETSKY E,HOVAKIMYAN N.Adaptive control of flight:theory,applications,and open problems[C]//Proceedings of American Control Conference.Minneapolis:IEEE,2006.