大型立式水轮发电机闭路循环通风系统仿真研究

Simulation Study on Closed-circuit Ventilation System of Large Vertical Hydraulic Turbine Generator

大型立式水轮发电机通风冷却对其安全稳定运行影响很大,研究发电机闭路循环通风流场特征是非常有必要的。目前,由于发电机内通风流道多、尺寸差异大,进行全流道建模模拟计算量过大,而给数值研究全流道通风流场带来一定的困难。该文提出了一种利用最小周期性单元建模研究发电机闭路循环流场的方法,并在CFX软件中引入了多重参考系坐标和冷却器多孔介质模型进行数值模拟计算。计算结果表明:轴向中心位置的定子通风沟风量较小,建议采用增大其横截面积的方法以增大风量,改善定子通风均匀性;磁轭风沟入口面流场存在一定的不均匀性,证明局部建模给定边界条件是不准确的;发电机上下端部流场存在不利涡。该文进一步对上下端部设置过渡圆弧板改造,并达到消除电机端部不利涡,通风量比原设计增大15.3%的效果。研究结果可为发电机通风系统的优化设计提供参考依据。

ABSTRACT：The ventilation cooling system of large vertical hydro-generator is of great significance to its safe and stable operation, and it is very necessary to study on the flow field characteristics of the generator closed-circuit ventilation system. At present, due to the structural complexity of the stator ventilating ducts in generator, full port modeling simulation needs large amount of calculation, which brings certain difficulties to the numerical study on the full port flow field. This paper proposes a method to study the circulating flow field by modeling the minimal periodic unit, and adopts the multiple reference frame coordinates, as well as porous media model of cooler in CFX software during the numerical calculation. The calculation results show that air flow rate of ventilating ducts is small at the generator neutral position, so a method of increasing the cross-sectional area is recommended to improve the uniformity of the stator ventilation. The flow field of the section at yoke ventilating duct entrance presents certain inhomogeneity, which proves that it is not accurate to set boundary condition in the local modeling calculation. There is disadvantageous vortex in the flow field of the generator end. This paper further sets the transition arc plates at the generator end to achieve the results of disadvantageous vortex eliminated and the air flow rate increased by 15.3% compared with the original design. The research results can provide reference for the optimization design of the generator ventilation system.