汽轮机抽汽缝宽度对邻近透平级流场的影响

Influence of Steam Extraction Slot Width on the Flow Fields of Neighboring Steam Turbine Stages

用数值模拟的方法对汽轮机抽汽口前透平级、抽汽口和抽汽口后透平级的流场进行了研究,介绍了流场模拟的数学模型及其解法。描述了不同抽汽缝宽度时抽汽缝内和抽汽口透平级的流场结构。指出:抽汽使得抽汽缝内形成了一个惯性涡区,改变抽汽缝宽度将明显改变抽汽量和抽气口透平级内沿叶高的压力和速度分布;在抽汽量不变时,增大抽汽缝宽度,会使惯性涡区的尺寸加大而涡强度减弱;在抽汽端压差不变时,增大抽汽缝宽度将使抽汽口前透平级的轴向推力和扭矩增大、并降低抽汽口前后透平级的轮周效率,同时降低了整个抽汽道内的流动阻力。

A numerical flow field simulation model for a turbine stage＇ s flow field in front of and next to an extraction slot as well as within the slot itself is presented together with the way of getting solutions, The flow field structure within the extraction slot and in the neighboring stages are depicted for various slot widths, pointing out that steam extraction causes a lasting vortex zone to appear and that the amount of steam extracted, as well as the pressure and velocity distribution along the blade＇s height of the neighboring stage, all vary with changing slot width. If the amount of extracted steam is kept constant, the dimensions of the lasting vortex zone extend with increasing slot width, while its intensity gets less, If the pressure difference over the extraction nozzle is kept constant, an increase of the slot＇ s width causes the axial thrust and the torsional moment of the preceding turbine stage to increase as well, while reducing the wheel efficiency of both the preceding and the following turbine stage; the flow resistance in the whole extraction tract is being reduced simultaneously. Figs 10, tables 2 and refs 6.