A Probe type PIV was developed in order to investigate behavior of liquid droplet in a steam turbine. Basically, this probe is composed from both a light sheet optics system and a bore-scope with purge function. The outer diameter of this probe is 〓48mm and length is 925mm. This probe can estimate particle size from relation between the gaseous phase velocity, the liquid phase velocity, and the liquid droplet size. This relation was derived by the wind-tunnel test. Furthermore, it was shown that the liquid phase velocity is measured with appling of the PIV probe to steam turbine, the gaseous phase velocity is measured using a pitot tube, and liquid droplet diameter can be derived. As a result, that the droplet size in main stream is larger than the droplet size atomized from trailing edge.
