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A gas turbine engine includes a pre-swirl structure. Inner and outer wall structures of the pre-swirl structure define a flow passage in which swirl members are located. The swirl members include a leading edge and a circumferentially offset trailing edge. Cooling fluid exits the flow passage with a

A gas turbine engine includes a pre-swirl structure. Inner and outer wall structures of the pre-swirl structure define a flow passage in which swirl members are located. The swirl members include a leading edge and a circumferentially offset trailing edge. Cooling fluid exits the flow passage with a velocity component in a direction tangential to the circumferential direction, wherein a swirl ratio defined as the velocity component in the direction tangential to the circumferential direction of the cooling fluid to a velocity component of a rotating shaft in the direction tangential to the circumferential direction is greater than one as the cooling fluid exits the flow passage outlet, and the swirl ratio is about one as the cooling fluid enters at least one bore formed in a blade disc structure. An annular cavity extends between the flow passage and the at least one bore formed in the blade disc structure.

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1. A gas turbine engine comprising: a supply of cooling fluid;a rotatable shaft;shaft cover structure;blade disc structure coupled to said shaft having at least one bore for receiving cooling fluid;a pre-swirl structure disposed about said shaft, said pre-swirl structure comprising: radially inner w

1. A gas turbine engine comprising: a supply of cooling fluid;a rotatable shaft;shaft cover structure;blade disc structure coupled to said shaft having at least one bore for receiving cooling fluid;a pre-swirl structure disposed about said shaft, said pre-swirl structure comprising: radially inner wall structure coupled to said shaft cover structure, said inner wall structure extending about said shaft;radially outer wall structure spaced from said inner wall structure, said outer wall structure coupled to said shaft cover structure and extending about said shaft, said inner and outer wall structures defining a flow passage therebetween, said flow passage including an inlet and an outlet and receiving a first portion of cooling fluid from said supply of cooling fluid; anda plurality of swirl members extending in said flow passage between said inner and outer wall structures, said swirl members each including a leading edge at said flow passage inlet and a trailing edge at said flow passage outlet and offset from said leading edge in the circumferential direction;a plurality of bypass passages associated with said shaft cover structure, said bypass passages in fluid communication with said supply of cooling fluid for supplying a second portion of cooling fluid from said supply of cooling fluid to a turbine rim cavity defined between said blade disc structure and an upstream stator support structure, said plurality of bypass passages including a first set of bypass passages and a second set of bypass passages, the first and second sets of bypass passages having inlets that are located respectively in separate chambers of the gas turbine engine and in different radial locations; anda static metering structure associated with an outlet of each said bypass passage, said metering structure comprising at least one flow passageway formed therein for permitting the second portion of cooling fluid in each said bypass passage to pass into the turbine rim cavity;wherein said supply of cooling fluid supplies the first portion of cooling fluid to said pre-swirl structure such that the cooling fluid exiting said flow passage outlet has a velocity component in a direction tangential to the circumferential direction;wherein a swirl ratio defined as the velocity component in the direction tangential to the circumferential direction of the first portion of cooling fluid to a velocity component of said shaft in the direction tangential to the circumferential direction is greater than one as the cooling fluid exits said flow passage outlet and the swirl ratio is about one as the first portion of cooling fluid enters said at least one bore formed in said blade disc structure; andwherein an annular cavity extends between said flow passage outlet and said at least one bore formed in said blade disc structure. 2. The gas turbine engine according to claim 1, wherein the swirl ratio is between about 1.15 and about 1.25 when the first portion of cooling fluid exits said pre-swirl structure. 3. The gas turbine engine according to claim 1, further comprising a particle separator including particle deflecting structure located downstream from said pre-swirl structure, said particle deflecting structure coupled to and extending radially inwardly from said blade disc structure, wherein said particle separator separates solid particles from the first portion of cooling fluid after the first portion of cooling fluid exits said pre-swirl structure. 4. The gas turbine engine according to claim 3, wherein said particle separator further comprises a particle collection chamber upstream from said particle deflecting structure, said particle collection chamber receiving the solid particles separated from the first portion of cooling fluid. 5. The gas turbine engine according to claim 3, wherein said pre-swirl structure remains stationary with said shaft cover structure and does not rotate with said shaft during operation of the gas turbine engine, and said particle deflecting structure rotates with said shaft during operation of the gas turbine engine. 6. The gas turbine engine according to claim 3, wherein said annular cavity is substantially defined by said blade disc structure, said pre-swirl structure, and said particle deflecting structure. 7. The gas turbine engine according to claim 1, further comprising sealing structure located axially between said flow passage outlet and said at least one bore formed in said blade disc structure, said sealing structure limits leakage between said annular cavity and the turbine rim cavity, which is located radially outwardly from said annular cavity. 8. The gas turbine engine according to claim 1, wherein said swirl members are configured such that the first portion of cooling fluid exiting said flow passage flows at an angle of from about 65° to about 85° relative to a central axis of the gas turbine engine. 9. The gas turbine engine according to claim 1, wherein said swirl members are arranged such that spacing between a first sidewall at said trailing edge of each said swirl member and a second sidewall of an adjacent swirl member causes a Venturi effect as the first portion of cooling fluid flows through said flow passage, the Venturi effect resulting in a pressure drop and a velocity increase of the first portion of cooling fluid flowing through said flow passage. 10. The gas turbine engine according to claim 9, wherein the Venturi effect is effected by converging sidewalls of adjacent swirl members. 11. The gas turbine engine according to claim 1, wherein the second portion of cooling fluid flowing from said supply of cooling fluid to the turbine rim cavity does not interact with the first portion of cooling fluid once the second portion of cooling fluid reaches said bypass passages. 12. The gas turbine engine according to claim 11, wherein each said flow passageway is formed in said metering structure at an angle such that the second portion of cooling fluid flowing out of each said flow passageway has a velocity component in the direction tangential to the circumferential direction. 13. The gas turbine engine according to claim 12, wherein said at least one flow passageway formed in said metering structure comprises at least one linear flow passageway such that the second portion of cooling fluid passes linearly into the turbine rim cavity. 14. A gas turbine engine comprising: a supply of cooling fluid;a rotatable shaft;a non-rotatable shaft cover structure disposed about said shaft;blade disc structure having at least one bore for receiving cooling fluid;a pre-swirl structure disposed about said shaft, said pre-swirl structure comprising: radially inner wall structure coupled to said shaft cover structure and extending circumferentially about said shaft;radially outer wall structure spaced from said inner wall structure, said outer wall structure coupled to said shaft cover structure and extending circumferentially about said shaft, said inner and outer wall structures defining a flow passage therebetween, said flow passage including an inlet and an outlet and receiving a first portion of cooling fluid from said supply of cooling fluid; anda plurality of swirl members extending in said flow passage between said inner and outer wall structures, said swirl members each including a leading edge at said flow passage inlet and a trailing edge at said flow passage outlet and offset from said leading edge in the circumferential direction;sealing structure located axially between said flow passage outlet and said at least one bore formed in said blade disc structure, said sealing structure limits leakage between said annular cavity and a turbine rim cavity located radially outwardly from said annular cavity;a plurality of bypass passages associated with said shaft cover structure, said bypass passages in fluid communication with said supply of cooling fluid for supplying a second portion of cooling fluid from said supply of cooling fluid to the turbine rim cavity, said plurality of bypass passages including a first set of bypass passages and a second set of bypass passages, the first and second sets of bypass passages having inlets that are located respectively in separate chambers of the gas turbine engine and in different radial locations; anda static metering structure that does not move relative to said shaft cover structure, said metering structure associated with an outlet of each said bypass passage and comprising at least one linear flow passageway formed therein per bypass passage for permitting the second portion of cooling fluid in each said bypass passage to pass linearly into the turbine rim cavity;wherein said supply of cooling fluid supplies the first portion of cooling fluid to said pre-swirl structure such that the first portion of cooling fluid exiting said flow passage outlet has a velocity component in a direction tangential to the circumferential direction;wherein a swirl ratio defined as the velocity component in the direction tangential to the circumferential direction of the first portion of cooling fluid to a velocity component of said shaft in the direction tangential to the circumferential direction is greater than one as the first portion of cooling fluid exits said flow passage outlet; andwherein an annular cavity extends between said flow passage outlet and said at least one bore formed in said blade disc structure coupled to said shaft, wherein an axial flow distance of the first portion of cooling fluid within said annular cavity is at least about 50 mm. 15. The gas turbine engine according to claim 14, wherein the second portion of cooling fluid flowing from said supply of cooling fluid to the turbine rim cavity does not interact with the first portion of cooling fluid once the second portion of cooling fluid reaches said bypass passages. 16. The gas turbine engine according to claim 15, wherein a pressure within said annular cavity is greater than a pressure within the turbine rim cavity and is greater than a pressure within a cavity located between said shaft and said shaft cover structure. 17. The gas turbine engine according to claim 14, wherein each said flow passageway is formed in said metering structure at an angle such that the second portion of cooling fluid flowing out of each said flow passageway has a velocity component in the direction tangential to the circumferential direction. 18. The gas turbine engine according to claim 14, further comprising a particle separator comprising: particle deflecting structure located downstream from said pre-swirl structure, said particle deflecting structure coupled to and extending radially inwardly from said blade disc structure, wherein said particle deflecting structure separates solid particles from the first portion of cooling fluid after the first portion of cooling fluid passes out of said pre-swirl structure; anda particle collection chamber upstream from said particle deflecting structure, said particle collection chamber defined at least in part by a portion of said shaft cover structure and receiving the solid particles separated from the first portion of cooling fluid by said particle deflecting structure. 19. The gas turbine engine according to claim 14, wherein the swirl ratio is about one as the cooling fluid enters said at least one bore formed in said blade disc structure. 20. The gas turbine engine according to claim 14, wherein: said swirl members are arranged such that spacing between a first sidewall at said trailing edge of each said swirl member and a second sidewall of an adjacent swirl member causes a Venturi effect as the cooling fluid flows through said flow passage, the Venturi effect resulting in a pressure drop and a velocity increase of the cooling fluid flowing through said flow passage, wherein the Venturi effect is effected by converging sidewalls of adjacent swirl members.