Exhaust frame
An exhaust frame includes: an inner casing; an inner diffuser which defines, between the inner diffuser and the inner casing, an annular inner cooling passage connected to a final-stage wheel space; an outer diffuser which defines an exhaust passage between the outer diffuser and the inner diffuser; an outer casing which defines an annular outer cooling passage between the outer casing and the outer diffuser; a strut which connects the inner casing and the outer casing to each other while crossing the exhaust passage; a strut cover which connects the inner diffuser and the outer diffuser to each other, and defines, between the strut cover and the strut, an annular connection passage connecting the inner cooling passage and the outer cooling passage to each other; and a communication hole provided in a wall of the outer cooling passage at a position on the downstream side of a center line of the strut in the flow direction of a combustion gas.
1. An exhaust frame connected to an outlet for a combustion gas of a turbine, the exhaust frame comprising:
an inner casing;
an inner diffuser wall that covers an outer side of the inner casing and defines, between the inner diffuser wall and the inner casing, an annular inner cooling passage connected to a final-stage wheel space of the turbine;
an outer diffuser wall that covers an outer side of the inner diffuser wall and defines an exhaust passage for the combustion gas between the outer diffuser wall and the inner diffuser wall;
a downstream-side diffuser connected to the outer diffuser wall at a downstream end of the outer diffuser wall relative to a flow of the combustion gas;
an outer casing that covers an outer side of the outer diffuser wall and defines an annular outer cooling passage between the outer casing and the outer diffuser wall, an end portion of the outer cooling passage being closed with a flange that connects the outer diffuser wall and the downstream-side diffuser;
a strut that connects the inner casing and the outer casing to each other, wherein the strut crosses the exhaust passage;
a strut cover that connects the inner diffuser wall and the outer diffuser wall to each other, covers the strut, and defines, between the strut cover and the strut, an annular connection passage connecting the inner cooling passage and the outer cooling passage to each other; and
a communication hole that penetrates the flange at a position downstream of a center line of the strut, relative to the flow direction of the combustion gas, wherein
the outer cooling passage is provided with a cooling air introduction hole at a position upstream of the connection passage relative to the flow of the combustion gas,
a flow pathway is formed such that cooling air introduced into the outer cooling passage from the cooling air introduction hole passes through the connection passage and flows down to the final-stage wheel space from an outlet of the inner cooling passage, and
the communication hole is configured to allow part of the cooling air in the outer cooling passage flowing from the cooling air introduction hole toward an inlet of the connection passage to flow out to a space outside of the downstream-side diffuser from the outer cooling passage.
2. The exhaust frame according to claim 1 , wherein the communication hole is provided at a position that is downstream of a downstream edge of the strut.
3. The exhaust frame according to claim 1 , wherein the strut is one of a plurality of struts that are provided along the circumferential direction of the inner casing, the communication hole is one of a plurality of communication holes, and at least one of the communication holes is provided between each pair of adjacent struts of the plurality of struts.
4. The exhaust frame according to claim 1 , wherein the communication hole is formed in a closable manner.