300MW直接空冷汽轮机低压末级鼓风态流场及湿度测量

Measurement of Flow and Wetness in Windage Condition in a 300 MW Direct Air-cooling Low Pressure Steam Turbine

研制了基于多波长消光法和4孔楔形气动探头的改进型联合探针,用该探针测量了某电厂300MW直接空冷机组低压汽轮机末级后在满负荷40kPa背压运行时末级后的流场和湿蒸汽。测量结果表明该汽轮机在该工况运行时低压缸末级产生鼓风,并有叶片根部的回流,鼓风区域约占叶高的51%,在鼓风区蒸汽湿度为零,鼓风状态时末级平均湿度仅0.23%,低压缸效率84.9%,次末级也存在鼓风现象。鼓风时运行表计指示的第7级抽汽温度不是汽缸内汽流的真实温度,而是鼓风温度。

A new probe was developed based on the principle of multi-wavelength light extinction and 4 holes wedge probe. Flow field and wetness behind the last stage in a 300MW direct air-cooling low pressure（LP） steam turbine were measured with this probe. The load and back pressure of the turbien were 300 MW and 40 kPa, respectively. The results show that there is windage in the last stage and the 2nd last stage. The region of the windage is about 51% in the total height of the last blade. The avarege wetness of the exhaust steam is only 0.23%. In the windage region the wetness is even zero. The internal efficiency of the LP turbine is 84.9% that agrees well with the thermal performance test. Temperature of 7th extraction steam indicated by the operating gauge is not the real temperature of the main steam tream, but the temperature of windage steam.