Patent ID: 11905848
Assignee: MITSUBISHI ELECTRIC CORPORATION
Field: Engines, pumps, turbines (Mechanical engineering)
Classification: CPC F  B | IPC B  F

Claim 10:
11. A manufacturing method for a turbine blade including a plurality of cooling passages along a blade height direction that are disposed at intervals in a front and rear direction of a blade, the manufacturing method comprising:
forming a first cooling passage by electrolytic machining while adjusting at least one of a current value and a machining speed from a front end toward a base end of the turbine blade, the first cooling passage having
a first cooling hole that has a first end opening toward the front end, and that has an inner diameter that is constant along the blade height direction, and
a second cooling hole that has a first end communicating with a second end of the first cooling hole without a level difference, and that has an inner diameter that is increased by a first expansion ratio toward the base end; and

forming a second cooling passage by electrolytic machining while adjusting at least one of a current value and a machining speed from the front end toward the base end of the turbine blade, the second cooling passage having an inner diameter that is increased by a second expansion ratio along the blade height direction, the second expansion ratio being smaller than the first expansion ratio, wherein
a length from the first end of the first cooling hole on the front end of the turbine blade to a position where the first cooling hole and the second cooling hole are communicated with is 40% to 60% of a length from the first end of the first cooling hole to a gas path surface on the base end of the turbine blade.