Turbine blade and gas turbine

A turbine blade, comprising:

• a blade body;
• and
• a plurality of cooling passages each of which extends inside the blade body along a blade height direction and which are connected to each other via return portions, each return portion being disposed at alternating ones of two opposite end portions in the blade height direction to form a serpentine passage,
• wherein the plurality of cooling passages includes:
• a most upstream passage disposed on a most upstream side in a flow of a cooling fluid among the plurality of cooling passages;
• a most downstream passage disposed on a most downstream side in the flow of the cooling fluid among the plurality of cooling passages;
• and
• at least one intermediate passage disposed between the most upstream passage and the most downstream passage among the plurality of cooling passages,
• wherein the most upstream passage is disposed at a position closest to a leading edge in a chord direction of the blade body among the plurality of cooling passages formed inside the blade body and extending along the blade height direction,
• wherein the turbine blade comprises:
• a plurality of first turbulators disposed on an inner wall surface of the most upstream passage and arranged along the blade height direction;
• a plurality of second turbulators disposed on an inner wall surface of the at least one intermediate passage and arranged along the blade height direction;
• and
• a plurality of third turbulators disposed on an inner wall surface of the most downstream passage and arranged along the blade height direction,
• wherein an average value of first angles of the plurality of first turbulators with respect to a flow direction of the cooling fluid in the most upstream passage is smaller than an average value of second angles of the plurality of second turbulators with respect to a flow direction of the cooling fluid in the at least one intermediate passage,
• wherein the blade body has a radially outer end and a radially inner end in the blade height direction, and extends along the blade height direction within a range that includes a central region including a middle position of the blade body in the blade height direction, an outer-diameter-side region between the central region and the radially outer end in the blade height direction, and an inner-diameter-side region between the central region and the radially inner end in the blade height direction,
• wherein [P2/e2]OD is a first ratio of a pitch P2 between a first pair of adjacent second turbulators of the plurality of second turbulators to a height e2 of the first pair of second turbulators with respect to the inner wall surface of the at least one intermediate passage, the first pair of adjacent second turbulators being in the outer-diameter-side region,
• wherein [P2/e2]ID is a second ratio of the pitch P2 between a second pair of adjacent second turbulators of the plurality of second turbulators to the height e2 of the second pair of second turbulators with respect to the inner wall surface of the at least one intermediate passage, the second pair of adjacent second turbulators being in the inner-diameter-side region,
• wherein [P2/e2]MEAN is a third ratio of the pitch P2 between a third pair of adjacent second turbulators of the plurality of second turbulators to the height e2 of the third pair of second turbulators with respect to the inner wall surface of the at least one intermediate passage, the third pair of adjacent second turbulators being in the central region, and
• wherein the first, second and third ratios satisfy a relationship of:
• [P2/e2]OD<[P2/e2]MEAN and [P2/e2]OD<[P2/e2]ID.