直接空冷机组易受气象条件影响，运行时背压变化大，影响汽轮机的安全经济运行，但对直接空冷机组末级流场和湿蒸汽进行过实测研究鲜有报道。用联合探针对某300 MW 直接空冷机组低压缸末级流场和蒸汽湿度进行了测量试验，获得了不同背压等工况下的蒸汽湿度、水滴尺寸等参数，以及这些参数沿叶高的分布。实测表明空冷机组低压缸不仅排汽湿度远低于湿冷机组，1次水滴的平均粒度也小于湿冷机组，且不存在2次水滴，测得的低压缸相对内效率与同期进行的热力性能试验结果吻合较好。

The backpressure of the direct air-cooling steam turbine is easily affected by the change of the weather and varies in a larger range. For study the behavior of the low pressure (LP) turbine in the direct air-cooling steam turbine, the flow field and wet steam were measured in the different backpressure in a 300 MW direct air-cooling LP turbine with a newly developed combined pneumatic/optical probe. The measured profiles of wetness, droplet size and distribution in different pressure and these parameters along the height of the blade are presented. The measurement shows that not only the wetness is lower comparing to the water-cooling turbine, but also the diameter of fine droplet is smaller. No coarse water was found in the turbine. The relative inner-efficiencies of LP turbine in different operation conditions measured by the probe and the thermal performance tests agree well.