generate traces of smoke when they are electrically heated by power from a variable voltage transformer. A laser sheet expanded from a He-Ne laser beam by a glass rod is used to illuminate the cross-sectional plane inside the turbine cascade. Different planes can be easily illuminated by manipulating the orientations and positions of the glass rod. In the study, the light sheet is often positioned at planes parallel to the leading edge of the cascade (X/Cx = 0.15, 0.45 and 0.90) or a plane parallel to the incoming flow {x/C « 0.45).

For the smoke wire flow visualization, the mainstream flow speed must be low enough for easy-identifying the vortices on the illuminated plane but high enough to avoid the smoke traces being affected by buoyancy as well as the back flow from the exit of the wind tunnel and to obtain straight smoke traces. In this study, the inlet main flow speed is about 2.7m/s, resulting a laminar flow on the tip-endwall with an exit Reynolds number of 7.0 x 104.

The vortex patterns produced the smoke wire are video-taped by a Panasonic camera at different viewing angles.

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