| 摘要 |
A freeze-lock phenomenon where water drops in a gap between a blade wheel (1a) and a shroud (1c) freeze to cause the blade wheel (1) not to rotate is prevented from occurring. A water discharge opening (1m) is provided over a range of about 20 degrees to one side from the lower end side of a ring section (1h) of the shroud (1). This makes it possible that, even if water drops that adhere on the surface of the blade wheel (1a) and the shroud (1c)(the ring section, particularly) gather on the lower side by gravity, the water can be quickly discharged. As a consequence, water drops are prevented from pooling in the gap between the blade wheel (1a) and the ring section (1h) (shroud (1c)). This prevents a freeze-lock phenomenon in time where temperature is low, or in wintertime.
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