applied by the steam burst.
In many cases of this kind of steam turbine, a gap in a radial direction is formed between tip sections of the turbine blades and the casing surrounding the turbine blades to form a flow path of the steam, and a gap in the radial direction is also formed between tip sections of the turbine vanes and the shaft body.
However, leaked steam passing through the gap of the turbine blade tip section toward a downstream side does not apply a rotational force to the turbine blades. In addition, since the leaked steam passing through the gap of the turbine vane tip section toward the downstream side does not convert the pressure energy into the velocity energy by the turbine vanes, the rotational force isconfiguration, as a leakage flow passing through the micro gap H101, H102 and H103 of the seal fins 504 (504A, 504B, 504C) collides with end edge sections (edge sections) 505 (505A, 505B, 505C) forming step surfaces 506 (506A, 506B, 506C) of the step sections 502 (502A, 502B, 502C), a flow resistance can be increased. In addition, steam separated by the end edge sections 505 (505A, 505B, 505C) of the step surfaces 506 (506A, 506B, 506C) becomes a separation vortex Y100. The separation vortex Y100 generates a downflow from tips of the seal fins 504 (504A, 504B, 504C) toward the tip section 501 of the turbine blade 500. The downflow exhibits a contraction flow effect of the steam passing through the micro gap H101, H102 and H103. For this