HTR-10氦气气轮机电磁轴承系统控制器研究

10 MW高温气冷实验堆(HTR-10)氦气气轮机直接循环发电系统将使用电磁轴承支承气轮机转子和发电机转子.由于正常工况下气轮机转子转速高于二阶挠性临界转速,因此,需要研究挠性转子在电磁轴承支承下过临界转速的控制方法.在根据相似原理设计的模拟气轮机转子-电磁轴承实验系统上,采用PID和相位补偿相结合的控制方法,通过仿真和实验,研究并设计了低刚度和高刚度控制器.在两种控制器分别作用下,转子都能够稳定悬浮,并且顺利地超越前两阶挠性临界转速,最高转速达到450 r/s.实验表明,与低刚度控制器相比,50～300 r/s转速内,高刚度控制器作用下的转子振幅明显减小,具有更好的控制性能.     

HTR-10氦风机磁悬浮转子跌落在辅助轴承上的数值分析

辅助轴承是10 MW高温气冷堆(HTR-10)氦风机磁力轴承-转子系统中的辅助支承结构,其主要任务是在磁力轴承因失电而失效时支承高速转动的转子,是整个系统安全运行的保证。本研究以HTR-10磁力轴承氦风机实验台架中的辅助轴承为研究对象,使用ABAQUS有限元软件数值模拟转子跌落,分析滚动辅助轴承内圈与滚动体的变形及能量损耗特性,并与初步的实验结果进行比对,验证辅助轴承的可靠性,为磁力轴承在高温气冷堆核电厂中的应用提供重要的技术保障。     

氦气透平轴向磁力轴承承载力-转速的内在关系

本文研究了轴向磁力轴承承载力与转速、材料强度之间的内在关系。轴向磁力轴承采用控制电流所产生的电磁力,使转子维持在悬浮工作位置不变,因此其工作原理决定了它的承载力与推力盘面积成正比。通过对推力盘的强度分析,找出了最大切应力和径向应力的位置。分析发现,推力盘的面积受轮缘处最大切应力的限制,与材料许用应力成正比、与转速成反比。本文给出的推力盘最大承载力与材料强度和最高转速的内在关系可用于指导氦气透平压气机轴向磁力轴承的设计。     

双圆盘柔性转子内阻尼对动力学稳定性的影响

转子内阻尼是导致其高速运转状态下发生失稳的诱因之一。本文针对典型的细轴连接双圆盘柔性转子，采用等效黏性阻尼耗散能表达式和拉格朗日方法，建立了考虑细轴内阻尼作用的动力学计算模型。系统性开展了不同内阻尼以及转速条件下的动力学稳定性分析，给出了不同转速阶段内阻尼对转子系统稳定性的影响规律。研究结果表明：当转子跨越临界转速后，内阻尼的存在将导致转子运动稳定性劣化；内阻尼数值越大，转子的失稳转速越低。本研究为柔性转子内阻尼分析提供了一种快速计算分析方法。     

一种磁力载荷模拟器的设计和研究

在研制10MW高温气冷堆氦气透平发电系统(HTR-10GT)过程中,需开展透平压气机转子的动力学性能试验。为了模拟透平压气机转子在运转过程中受到的气动力和不平衡力,需对转子施加一定载荷。本文介绍了一种磁力载荷模拟器的设计,该载荷模拟器采用与磁力轴承相似的技术,通过电流产生磁力直接在模拟转子上加载轴向和径向载荷。磁力载荷模拟器包括轴向载荷模拟器和径向载荷模拟器两部分,轴向气动力载荷用轴向载荷模拟器模拟,叶片气动周向力载荷和不平衡力离心载荷用径向载荷模拟器来模拟。轴向载荷模拟器可施加载荷设计值为10kN,径向载荷模拟器载荷设计值为715N,气隙均为1mm。通过分析计算,磁力载荷模拟器完全可满足本试验中的加载要求。同时,磁力载荷模拟器可灵活加载,在线加载,快速改变载荷大小和形式,为电磁轴承的应用开发了一个新领域。     

磁力轴承转子动力学分析中不平衡载荷的设定

参考航空发动机上常用的关于不平衡响应的分析方法,结合磁力轴承支承刚度远低于普通轴承的特点,提出了设定磁轴承支承下转子不平衡载荷的一种工程方法.这一方法可为进一步研究磁力轴承-转子系统设计中的转子不平衡响应、转子运行的稳定域度及进行转子动平衡设计等打下良好基础.     

HTR-10磁力轴承氦风机辅助轴承承载特性分析

基于Hertz接触理论,提出一种由转子轴心位移数据推算球轴承内部接触应力以及外部载荷的计算方法,将其应用于HTR-10磁力轴承氦风机转子跌落实验,并分析转子跌落后不同阶段辅助轴承的承载特性。结果表明,辅助轴承能很好地抵御转子跌落产生的轴向冲击,不会在辅助轴承内部产生严重的塑形变形,对辅助轴承工作性能不会产生影响。另一方面,转子的回转运动以及初始急加速时内圈上的热积聚是转子惰转过程中辅助轴承径向载荷的主要来源,也是导致辅助轴承失效的重要因素。文中分析了径向载荷的影响,结果表明所选辅助轴承方案仍可以满足跌落要求。     

HTR-10磁力轴承氦风机辅助轴承承载特性分析

基于Hertz接触理论,提出一种由转子轴心位移数据推算球轴承内部接触应力以及外部载荷的计算方法,将其应用于HTR-10磁力轴承氦风机转子跌落实验,并分析转子跌落后不同阶段辅助轴承的承载特性。结果表明,辅助轴承能很好地抵御转子跌落产生的轴向冲击,不会在辅助轴承内部产生严重的塑形变形,对辅助轴承工作性能不会产生影响。另一方面,转子的回转运动以及初始急加速时内圈上的热积聚是转子惰转过程中辅助轴承径向载荷的主要来源,也是导致辅助轴承失效的重要因素。文中分析了径向载荷的影响,结果表明所选辅助轴承方案仍可以满足跌落要求。     

HTR-10GT辅助轴承结构特性研究

在10 MW高温气冷堆氦气透平发电系统(HTR-10GT)中,辅助轴承用于失去磁力轴承主支承后的临时辅助支承,是整个转子系统重要的安全保障.本文综述了辅助轴承的研究现状,针对已建立的辅助轴承实验台架,采用有限元建模分析,讨论了辅助滚动轴承保持架的结构特性,为辅助轴承的结构设计提供了重要参考.     

基于拟静力学方法的HTR-10磁轴承氦风机辅助轴承抗冲击特性研究

对清华大学10 MW高温气冷堆(HTR-10)磁轴承氦风机辅助轴承抗冲击特性进行研究,计算立式转子跌落的冲击作用力,并采用拟静力学分析方法对辅助轴承变形量进行计算。计算结果表明:在不同转速下,立式转子跌落在一定时间后对辅助轴承作用力大致相同,跌落后期接触力达到仅与跌落前转子(包括转子转速、质量等)有关的恒定值;跌落后期辅助轴承变形量与该接触力有关,而辅助轴承变形量在宏观上表现为轴承系统的振动位移。因此,辅助轴承的振动位移量可作为衡量辅助轴承自身状态的参数。     

Characteristic analysis of rotor dynamics and experiments of active magnetic bearing for HTR-10GT

A 10 MW high-temperature gas-cooled reactor (HTR-10) was constructed by the Institute of Nuclear and New Energy Technology (INET) at Tsinghua University of China. The helium turbine and generator system of 10 MW high-temperature gas-cooled reactor (HTR-10GT) is the second phase for the HTR-10 project. It is to set up a direct helium cycle to replace the current steam cycle. The active magnetic bearing (AMB) instead of ordinary mechanical bearing was chosen to support the rotor in the HTR-10GT. This rotor is vertically mounted to hold the turbine machine, compressors and the power generator together. The rotor's length is 7 m, its weight is about 1500 kg and the rotating speed is 15,000 rpm. The structure of the rotor is so complicated that dynamic analysis of the rotor becomes difficult. One of the challenging problems is to exceed natural frequencies with enough stability and safety during reactor start up, power change and shutdown. The dynamic analysis of the rotor is the base for the design of control system. It is important for the rotor to exceed critical speeds. Some kinds of softwares and methods, such as MSC.Marc, Ansys, and the transfer matrix method (TMM), are compared to fully analyze rotor dynamics characteristic in this paper. The modal analysis has been done for the HTR-10GT rotor. MSC.Marc was finally selected to analyze the vibration mode and the natural frequency of the rotor. The effects of AMB stiffness on the critical speeds of the rotor were studied. The design characteristics of the AMB control system for the HTR-10GT were studied and the related experiment to exceed natural frequencies was introduced. The experimental results demonstrate the system functions and validate the control scheme, which will be used in the HTR-10GT project.     

Design aspects and achievements of active magnetic bearing research for HTR-10GT

The project of direct helium turbine power conversion cycle of the 10 MW high-temperature gas-cooled reactor (HTR-10GT) program is to set up a direct helium cycle with a helium turbine and generator system to replace the current heat exchange system and steam cycle. This program is supported by Chinese government and will be assumed by the Institute of Nuclear and New Energy Technology (INET) at Tsinghua University of China. Instead of ordinary mechanical bearing, active magnetic bearing (AMB) has been chosen to support the helium turbine and generator rotors in this project. Until now, no experience on AMB running in reactor or in helium environment has been performed. So, the AMB research and experiment would at least go through several convictive stages to finally match the requirements of the HTR-10GT program. The magnetic bearing laboratory of INET has begun to work on this project in 2002. Till now, a control method of exceeding two bending frequency has been successfully tested on a small test rig. A high load AMB for 3500 kg generator rotor suspension has been constructed and long-term running tests have just been finished. In addition, the general design of a high-temperature AMB test rig has already been finished. All these achievements on AMB research show that we are well on the way to the ultimate goal of direct helium cycle. Today the final joint experiment of turbine and generator is already under detailed planning.     

A contribution on the investigation of the dynamic behavior of rotating shafts with a Hybrid Magnetic Bearing Concept (HMBC) for blower application

Within a subproject of the RAPHAEL-Program, which was part of the 6th EURATOM Framework Program supervised by the European Commission, it was investigated whether the use of a Hybrid Magnetic Bearing Concept (HMBC) will be beneficial for a blower application. Within the RAPHAEL program, the subproject “Component Development” is dealing with R&D of components of High Temperature Reactor Technology (HTR), where a major focus is on safety- and reliability-related issues. That implies special requirements for the support of high speed rotating shafts in HTR-Applications that only can be satisfied by using Active Magnetic Bearings (AMB). Regarding safety and competitiveness, AMBs are considered to be key components for the support of rotating HTR-components due to their technical features. AMBs are characterized by an electromagnetic actuator that is generating the bearing force depending on the clearance between stator and rotor, in which the rotor is levitated. Therefore an active control of the coil current is necessary. Furthermore, Touch Down Bearings (TDB) are needed to avoid damages in case of an emergency shut down or in case of energy supply losses.This contribution provides an internal insight on the advantages of a Hybrid Magnetic Bearing Concept that is characterized by a completely Active Magnetic Bearing-supported vertical arranged rotor and an additional permanent magnetic radial orientated bearing. One benefit of the HMBC is an additional radial guidance of the shaft that may reduce the loads while dropping into the Touch Down Bearings e.g. in case of energy supply losses of the AMBs. Reduced loads on the TDBs will increase their life cycle and the availability of the AMB supported component.The scope of this R&D-Project, which will be described more detailed in this contribution, includes: the analytical modeling and simulation of the dynamic behavior of the Hybrid Magnetic Bearing System; the modification of the completely AMB-supported test facility FLP 500 with a radial PMB; the experimental tests and validation of the analytical models to provide recommendations for the investigated blower application as a HTR-component. Furthermore, the effects occurring during the modification of the test facility and the approach that was necessary to solve unexpected problems will be described.     

高温堆磁悬浮轴承备用氦风机热工实验研究

高温堆磁悬浮轴承支承的备用氦风机是国内首次磁悬浮轴承的工业级应用,也是世界上首次将磁悬浮轴承应用在反应堆领域.为了验证磁悬浮轴承氦风机在热态工况下的性能以及整套系统的可靠性,进行了磁悬浮轴承氦风机的台架实验.在磁悬浮轴承氦风机的热工实验中,通过静态加热、动态加压、动态加热等实验,证明系统能够在热态工况下稳定运行,最后,磁悬浮轴承氦风机顺利通过了100 h热态考核出厂实验.     

内阻尼对柔性连接转子系统稳定性的影响

工作在高速柔轴下的柔性连接转子容易发生转子动力学失稳,柔性连接处内阻尼是引起失稳的主要因素。采用Kelvin-Voigt黏弹性理论建立转子柔性连接的复刚度内阻尼模型,通过Kelvin-Voigt黏弹性理论损耗因子与转子模态测试得到复刚度模型中代表内阻尼的虚部系数,应用拉格朗日方法建立柔性连接转子系统的动力学方程。结合试验结果验证了模型的合理性,研究了连接处内阻尼和减振器动力学参数对转子系统稳定性的影响。结果表明,增大柔性连接处内阻尼会极大降低转子系统的稳定性,增大减振器中的刚度系数和减小折合质量可有效提高稳定性,系统的稳定性需从连接处和减振器两方面协调设计。     

轴承摩擦磨损对柔性支承转子动力响应特性的影响

柔性支承转子中唯一的动静接触组件为轴承,由轴和窝组成。轴和窝之间的摩擦对转子的动力响应特性有直接影响,研究其影响机理是轴承设计和优化的重要前提。本文建立了轴承的非刚性连接模型,并将其引入柔性支承转子模型中;从理论上研究不同轴承摩擦磨损程度对转子动力响应的影响;计算并分析了轴承摩擦磨损状态下转子的动力响应特性;分析了轴承磨损导致转子进动失效时转子释放的最大能量。研究结果表明,随着轴承摩擦磨损程度的加深,转子的振幅增大,转子出现二阶进动现象,磨损严重时伴随出现拟周期运动。轴承摩擦磨损可能导致转子出现不同的失效模式,转子做二阶进动和拟周期运动时会使失效转子释放的最大能量大幅增加。研究结果可为柔性支承转子的轴承优化设计提供理论依据。     

Numerical analysis of the static performance of an annular aerostatic gas thrust bearing applied in the cryogenic turbo-expander of the EAST subsystem

The EAST superconducting tokamak,an advanced steady-state plasma physics experimental device,has been built at the Institute of Plasma Physics,Chinese Academy of Sciences.All the toroidal field magnets and poloidal field magnets,made of NbTi/Cu cable-in-conduit conductor,are cooled with forced flow supercritical helium at 3.8 K.The cryogenic system of EAST consists of a 2 kW/4 K helium refrigerator and a helium distribution system for the cooling of coils,structures,thermal shields,bus-lines,etc.The high-speed turbo-expander is an important refrigerating component of the EAST cryogenic system.In the turbo-expander,the axial supporting technology is critical for the smooth operation of the rotor bearing system.In this paper,hydrostatic thrust bearings are designed based on the axial load of the turbo-expander.Thereafter,a computational fluid dynamics-based numerical model of the aerostatic thrust bearing is set up to evaluate the bearing performance.Tilting effect on the pressure distribution and bearing load is analyzed for the thrust bearing.Bearing load and stiffness are compared with different static supply pressures.The net force from the thrust bearings can be calculated for different combinations of bearing clearance and supply pressure.     

HTR-10磁轴承转子动力学的初步研究

采用有限元方法和MSC．Marc软件，分析了10MW高温气冷堆(HTR-10)能量转换系统磁轴承转子的模态，研究了磁轴承支承刚度与固有频率的关系。研究结果表明，可以通过改变支承刚度和转子材料来调整固有频率，为转子过两阶弯曲频率及磁轴承控制系统设计提供了依据。