【作者】 王新；

【导师】 许良军； Bogdan Miedzinski；

【作者基本信息】 北京邮电大学 ， 机械电子工程， 2009， 博士

【摘要】 随着我国高速、重载铁路的大面积推广,无缝线路乃至超长无缝线路被人们接受并得到实际应用,是世界铁路轨道结构的发展方向。为了保证无缝线路轨道的使用寿命及确保行车安全,对于无缝线路技术的研究显得越发重要。自然环境条件下的温度变化会在钢轨内部产生拉伸应力,影响无缝线路轨道的稳定性。因此在铺设无缝线路时,钢轨温度需要保持在一定的范围内,以避免恶劣气候条件下钢轨内部产生的拉伸应力对其产生的损害。锁定轨温即在钢轨内部没有应力时,对钢轨进行锁定时的轨温,也叫零应力轨温。对于我国北部寒冷地区,一年内有较长时间环境温度低于锁定轨温(25～30℃),在此种情况下铺设无缝线路轨道时若不进行锁定轨温的控制,钢轨在日后会由于温度变化过大积蓄过量的温度应力,从而影响轨道寿命、危及行车安全,因此对于无缝线路轨道铺设作业过程中的锁定轨温控制技术是我国无缝线路轨道发展亟需解决的课题之一。目前,欧洲通常采用温度控制法进行无缝线路轨道锁定轨温的控制。该方法利用丙烷-丁烷混合气体火焰加热无缝线路轨道,该方法易于操作、工序简单,但由于其是通过热传导方法加热钢轨,因此对钢轨表面伤害较大,且热传导方式易导致钢轨内部应力不均的问题。在我国最为常用的方法是利用拉伸机拉伸钢轨以达到锁定轨温允许的长度范围。拉伸法具有轨温控制准确、受施工环境条件影响较小等特点;但存在操作工序相对复杂、施工时间较长、钢轨内部应力分布不均匀等缺点。本文采用低频横向磁通感应加热技术在钢轨内部通过涡流的热效应加热钢轨以达到控制钢轨锁定轨温的目的,该方法解决了长期以来锁定轨温控制技术中钢轨内部应力分布不均匀的问题。电磁感应加热技术具有非接触式加热、高效、环保、节能等一系列优点,且由于被加热工件成为热源对自身进行加热,其热量传递变得更加高速快捷。本文主要对低频横向磁通感应加热系统在无缝线路轨道控制锁定轨温技术上的实用性和可靠性进行了理论分析及实验验证,主要研究内容如下:1.研究了低频横向磁通感应加热系统的工作频域范围,利用集肤效应理论及透热深度计算公式,结合钢轨材料磁饱和特性分析,确定了系统工作频率范围(50～600Hz),使低频横向磁通感应加热系统的加热效率及工作质量得到保证。2.利用有限元软件建立了低频横向磁通感应加热系统模型,采用电磁-热间接耦合方法分析被加热工件(钢轨)的涡流场、温度场分布情况以及系统工作过程中的热流走势,并利用测温实验验证、校正了有限元分析模型。根据有限元计算结果优化了低频横向磁通感应加热系统结构设计、加载激励参数,提出了有效提高系统加热效率的可行性方案,为低频横向磁通感应加热系统性能的进一步提高提供了经验指导。3.利用内外力矩平衡理论建立了无缝线路轨道静态稳定性模型。结合压杆稳定性分析及温度力公式计算钢轨模型失稳临界边界条件,通过计算分析,给出了钢轨静态稳定性模型失稳临界温升,用以限定、优化低频横向磁通感应加热系统在控制锁定轨温作业时的工作模式。4.对低频电磁感应加热方法应用于无缝线路铺设作业锁定轨温控制技术的可行性进行了评估,为低频电磁感应加热方法在无缝线路轨道铺设作业锁定轨温控制技术中的应用提供了理论依据和数据支持。更多还原

【Abstract】 High speed, Heavy load railway is a common trend for world railway and has become an important sign of railway modernization. In order to guarantee the safety and stability of high-speed train, the study of continuous welded rail (CWR) tracks has become more and more important.The variability of weather and climate is a cause of considerable stress to CWR track which has influence on the stability of rail. Therefore, rigid jointless track laying must be carried out under specific thermal conditions to avoid dangerous tensile and compressive stress in the rails during extreme weather. The specific thermal condition so called neutral temperature is the temperature where no thermal forces are acting upon the CWR track. In north of China, it is common that the daily mean temperature is lower than the required neutral one (25～30℃). Thus, in order to guarantee the service life and safety of rail track, it is necessary to heat the rigid CWR track during track-laying to control stress-free temperature of rail. The control technology of stress-free temperature (CSFT), as one of the key technologies on CWR track laying, needs to be considered and researched seriously.In Europe, CSFT is very frequently done with propane-butane gas heaters which use heat transfer method to heat the rail. This technology is easy to operate and do not have any complex process. The main disadvantage of this method is the high thermal stress gradient generated in the rail cross-section and overheating of the surface.In China, stretching method is the most popular CSFT which uses stretching machine to draw the rail and make the length of it reach the standard one. This method can control the stress-free temperature of rail accurately and do not have too much influence of environment condition. But it will also cause the uneven distribution of thermal stress and the process of it is much more intricate.These problems may be eliminated by using low frequency transverse flux induction heating in which the heat (eddy current losses) is generated inside a selected volume of the rail. In comparison with other methods the induction heating (by eddy current losses) is an alternative that has numerous attractive features. Lack of any butt joints, isolation of the heating inductor from the rail and a simple way of transporting the energy to the rail are the most important advantages. This method imposes qualitatively different heat conditions than normally, (because the rail itself becomes the heat source) which influences directly the thermal processes (heating and cooling). Thus, it is possible to achieve both heat transfer and improved temperature distribution in the rail body.The main objective of the dissertation is to analyze theoretically and confirm experimentally possibility of employment of a low frequency transverse flux induction heating for CWR under track laying. The main results achieved are as follows:1. Theoretical analysis of frequency character of induction heating, using skin effect theory and magnetic saturation principle to interpret the necessity of low frequency application in the induction heating of CSFT and calculate the effective frequency domain of low frequency transverse flux induction heating (50～600Hz) to guarantee the heating efficiency and heating quality of the system.2. Theoretical three dimensional FEM analysis of magnetic field and temperature field distribution inside volume of a railway rail under low frequency heating for different structure of the heater applied. Experimental investigations for physical model of the low frequency induction heater of the railway rail to verify the theoretical approach. Analysis of heating efficiency related to heating frequency, structure of the heater and variable environmental conditions.3. Established stability model of CWR track, using inner and external moments’ equilibrium theory and Hook’s law calculate the critical temperature rise value of CWR track to limit and optimize the heating mode.4. Formulation of conclusions and recommendations for use of the low frequency transverse flux induction heating for CWR under track laying in practice.更多还原