计及旋转状态的全空冷水轮发电机多物理场耦合计算与分析

发布时间：2019-02-12 14:39

【摘要】：随着对可再生清洁能源的深入开发利用,水力发电的发电容量一直呈增长趋势。作为将能量转换的关键电力设备—水轮发电机,其单机容量正处于上升趋势。随着单机容量的不断增大,大容量水轮发电机的通风冷却与传热问题成为其设计的关键性问题之一。本文以五强溪电站中的一台250MW全空冷水轮发电机为例,根据发电机的实际结构尺寸及电磁场理论,建立了发电机的二维电磁场数学模型。采用有限元计算方法对发电机的电磁场模型进行求解计算,计算分析了发电机的磁场分布、阻尼绕组中的涡流分布及气隙磁场的分布。基于此,确定出阻尼绕组的涡流损耗和气隙磁场的各次谐波幅值的大小。并通过数值解析方法计算出转子内的附加损耗。基于以上的理论分析,根据水轮发电机内部传热、冷空气流动及特殊的通风冷却系统结构等特点,在计及转子旋转的条件下,建立了 250MW水轮发电机转子求解域内的三维流体-温度耦合场的物理和计算模型,并利用有限体积数值计算方法对转子求解域内的耦合场进行了计算。首先,分析了转子内热源构件的温度随时间的变化规律和热源构件的稳态温度分布情况,进一步研究了热源构件的稳态温度沿轴向的变化规律。并将计算得到的励磁绕组平均温度与实测数据进行对比,验证了方法的正确性。其次,对比分析了非热源构件和转子求解域内冷空气的最高温度和平均温度,研究了温度分布不均匀的极身绝缘、磁极压板、上下托板、端部流体以及极间流体的温度分布。在此基础上,研究了支架入口空气温度变化对励磁绕组表面散热系数的影响。最后,对求解域内流体流动进行了研究,计算分析了极间流体迎、背风侧的速度分布、极间流体在磁轭通风道处和相邻磁轭通风道之间的轴向截面速度分布以及转子热源附近流体的动压分布。针对转子磁轭通风道结构改变的情况,研究了相邻磁轭通风道距离的增大对励磁绕组温度分布和励磁绕组迎、背风侧附近流体的速度分布情况的影响。并分析了磁轭通风道出口宽度变小的程度对励磁绕组迎、背风侧外表面的温度分布、极间流体在周向和轴向的截面流速分布以及极间流体迎、背风侧的温度分布的影响。对于转子磁轭通风道发生堵塞故障时,计算了磁轭通风道在不同程度和不同位置发生堵塞故障时的励磁绕组最高温度。由于磁轭通风道全堵塞对励磁绕组最高温度影响较大,因此研究了各磁轭通风道全堵塞对极身绝缘温度、极间流体速度及气隙内流体速度的影响。
[Abstract]:With the further development and utilization of renewable clean energy, the power generation capacity of hydropower has been increasing. As the key power equipment to convert energy-hydrogenerator, its single unit capacity is on the rise. With the increasing of single unit capacity, the ventilation cooling and heat transfer of large capacity hydrogenerator becomes one of the key problems in its design. Taking a 250MW all-air-cooled hydrogenerator in Wuqiangxi Hydropower Station as an example, according to the actual structure size of generator and the theory of electromagnetic field, the mathematical model of 2-D electromagnetic field of generator is established. The electromagnetic field model of generator is solved by finite element method, and the distribution of magnetic field, eddy current in damping winding and air gap magnetic field are calculated and analyzed. Based on this, the eddy current loss of damping windings and the amplitude of each harmonic of air-gap magnetic field are determined. The additional losses in the rotor are calculated by numerical analysis. Based on the above theoretical analysis, according to the characteristics of internal heat transfer, cold air flow and special ventilation and cooling system structure of hydrogenerator, under the condition of rotor rotation, The physical and computational model of three-dimensional fluid-temperature coupling field in the solution domain of 250MW hydrogenerator rotor is established, and the coupling field in the rotor solution domain is calculated by using finite volume numerical method. Firstly, the variation law of temperature with time and the steady state temperature distribution of heat source member in rotor are analyzed, and the variation law of steady state temperature of heat source member along axial direction is studied. The calculated average temperature of the excitation winding is compared with the measured data to verify the correctness of the method. Secondly, the maximum temperature and average temperature of cold air in the solution domain of non-heat source components and rotors are compared and analyzed, and the temperature distributions of pole-body insulation, magnetic plate, up-and-down plate, end fluid and inter-pole fluid with uneven temperature distribution are studied. On this basis, the influence of air temperature at the inlet of the bracket on the surface heat dissipation coefficient of the excitation winding is studied. Finally, the fluid flow in the solution domain is studied, and the velocity distribution of the interpolar fluid facing and leeward is calculated and analyzed. The axial cross section velocity distribution and the hydrodynamic pressure distribution near the rotor heat source of the interpolar fluid at the yoke vent and between the adjacent yoke vents. In view of the change of the structure of the rotor yoke ventilation channel, the influence of the distance between the adjacent yoke vents on the temperature distribution of the excitation winding and the velocity distribution of the fluid near the excitation winding and the leeward side is studied. The influence of the smaller outlet width of the yoke on the temperature distribution of the excitation winding, the outer surface of the leeward side, the velocity distribution of the cross-section of the interpolar fluid in the circumferential and axial direction, and the temperature distribution of the interpolar fluid and the side of the leeward are analyzed. The maximum temperature of the excitation winding of the rotor yoke is calculated when the fault of the rotor yoke ventilation occurs in different degrees and at different locations. Because the full blockage of the yoke ventilation channel has a great influence on the maximum temperature of the excitation winding, the effect of the full blockage of the yoke ventilation duct on the polar insulation temperature, the velocity of the fluid between the poles and the velocity of the fluid in the air gap is studied.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM312

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