600MW空冷汽轮机末级叶片脱流现象的研究

Research on the Phenomenon of Flow Separation of Last Stage in a 600MW Air-cooling Turbine

采用CFX软件对某600 MW空冷汽轮机低压缸内末级流道内湿蒸汽或工质的流动规律进行数值研究。结果表明:在同一质量流量工况下,随着背压的升高,末级动叶上的脱流越来越严重。在背压为11 k Pa(额定背压)工况时,叶片上未出现脱流现象。随着背压的升高,动叶叶片根部脱流区域未变,由叶根至5%叶高处,而顶部脱流区域增大,由90%叶高至叶顶处变为70%叶高至叶顶处。同一背压下,随着质量流量的减小,脱流区在叶顶处明显增大,可以扩展到70%叶高至叶顶处,背压升高或流量降低加剧了动叶上的径向流。

The flow pattern of wet steam of the last stage in low-pressure cylinder of a 600 MW air-cooling turbine was numerically researched by CFX software.The results show that with the increase of the back pressure,the phenomenon of flow separation in the last stage gets worse and worse under the same condition of mass flow.When the back pressure is 11 k Pa,the phenomenon of flow separation does not be observed on the blade in the last stage.With the increase of the back pressure,the flow separation in rotor blade root has not changed from the blade root to 5% blade height,but the flow separation area in the blade tip increases,and its distribution which is from 90% blade height to the blade tip becomes from 70% blade height to the blade tip.In addition,with the decrease of mass flow rate,flow separation area increases in the part of the blade tip,and its distribution extends from 70% blade height to the blade tip under the same back pressure.The radial flow can be exacerbated when back pressure increases or mass flow decreases.