DIFFUSER AND STEAM TURBINE INCLUDING THE SAME

To suppress formation of a peeling generation region in a diffuser space.SOLUTION: A diffuser includes an outside ring 30 and an inside ring. Out of an inner peripheral surface 30i of the outside ring 30, a portion in which the position closest to an axial line downstream side Dad out of a tip 14t of a final rotor blade row 13a and the position of an axial direction Da are the same becomes an inlet edge 38. Out of the inner peripheral surface 30i, an end of the axial line downstream side Dad is an outlet edge 39. Out of the inner peripheral surface 30i, a region spreading to an axial line upstream side Dau from the outlet edge 39 is a downstream region Rd. Out of the inner peripheral surface 30i, a region spreading to the axial line downstream side Dad from the inlet edge 38 is an upstream region Ru. The outside ring 30 has a peeling suppression structure 40. The peeling suppression structure 40 includes: a suction port 41 opening in the downstream region Rd out of the inner peripheral surface 30i; a discharge port 42 opening in the upstream region Ru out of the inner peripheral surface 30i; and a steam return flow passage 43 for communicating the suction port 41 and the discharge port 42.SELECTED DRAWING: Figure 4 【課題】ディフューザ空間内での剥離発生領域の形成を抑制する。【解決手段】ディフューザは、外側環３０と、内側環と、を備える。外側環３０の内周面３０ｉ中で、最終動翼列１３ａの先端１４ｔ中で最も軸線下流側Ｄａｄの位置と軸線方向Ｄａの位置が同じ部分が入口縁３８を成す。内周面３０ｉ中で、軸線下流側Ｄａｄの端が出口縁３９を成す。内周面３０ｉ中で、出口縁３９から軸線上流側Ｄａｕに広がる領域が下流領域Ｒｄを成す。内周面３０ｉ中で、入口縁３８から軸線下流側Ｄａｄに広がる領域が上流領域Ｒｕを成す。外側環３０は、剥離抑制構造４０を有する。剥離抑制構造４０は、内周面３０ｉ中の下流領域Ｒｄ内で開口している吸込口４１と、内周面３０ｉ中の上流領域Ｒｕ内で開口している吐出口４２と、吸込口４１と吐出口４２とを連通させる蒸気戻し流路４３と、を有する。【選択図】図４