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A gas turbine engine including a secondary air system with interconnected fluid passages defining at least one flow path between a common source of pressurized air and a common outlet. Some of the fluid passages deliver the pressurized air to components of the gas turbine engine. The fluid passages

A gas turbine engine including a secondary air system with interconnected fluid passages defining at least one flow path between a common source of pressurized air and a common outlet. Some of the fluid passages deliver the pressurized air to components of the gas turbine engine. The fluid passages include a common fluid passage through which all circulation of the pressurized air to the common outlet passes. The common fluid passage has a section including a venturi configured for controlling a flow of the pressurized air from the source to the outlet. In one embodiment, the venturi is provided in a common inlet or common outlet passage. A method of pressurizing a secondary air system is also discussed.

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1. A gas turbine engine comprising: a compressor providing a source of pressurized air;a secondary air system including at least one flow path defining a fluid communication between the source of pressurized air and a common outlet communicating with an environment of the gas turbine engine, and a p

1. A gas turbine engine comprising: a compressor providing a source of pressurized air;a secondary air system including at least one flow path defining a fluid communication between the source of pressurized air and a common outlet communicating with an environment of the gas turbine engine, and a plurality of fluid passages communicating with the at least one flow path and with components of the gas turbine engine for delivery of the pressurized air thereto, the at least one flow path including a common fluid passage defining a venturi with a single inlet and a single outlet and configured such that all the pressurized air circulated to the common outlet passes through the venturi before reaching the common outlet, the venturi configured for controlling a flow of the pressurized air from the source of pressurized air to the common outlet and through the plurality of fluid passages,wherein the common fluid passage is defined through a low pressure shaft of the gas turbine engine, the venturi being defined at one end of the low pressure shaft, driven by a low pressure turbine, the communication between the common outlet and the source of pressurized air being provided through the low pressure shaft, and wherein at least a portion of the pressurized air entering the common fluid passage and venturi enters the common fluid passage through holes in the low pressure shaft from a passage defined between the low pressure shaft and a high pressure shaft, driven by a high pressure turbine, wherein the holes are located aft of the high pressure turbine with respect to a longitudinal axis of the gas turbine engine. 2. The gas turbine engine as defined in claim 1, wherein the components of the gas turbine engine communicating with the fluid passages include one or more of oil cavity seals, rotors, blades and vanes. 3. The gas turbine engine as defined in claim 1, wherein the venturi is located downstream with respect to the fluid passages communicating with the components of the gas turbine engine. 4. The gas turbine engine as defined in claim 1, wherein the common fluid passage including the venturi is an outlet passage adjacent to and in communication with the common outlet. 5. The gas turbine engine as defined in claim 1, wherein the venturi is defined by a central opening of a hollow bolt received within an outlet passage at the one end of the low pressure shaft, the hollow bolt engaging the low pressure shaft to a blade disk of the gas turbine engine. 6. The gas turbine engine as defined in claim 1, wherein the venturi is configured to limit the flow through the plurality of fluid passages at a first power level of the gas turbine engine without limiting the flow through the plurality of fluid passages at a second power level lower than the first power level, and wherein the flow through the fluid passages is from the source of pressurized air at the first and second power levels. 7. The gas turbine engine as defined in claim 1, wherein the compressor includes a plurality of rotors having blades rotatable in an annular gas path, the source of pressurized air being defined by a plenum in fluid communication with the annular gas path of the compressor. 8. The gas turbine engine as defined in claim 7, wherein the plurality of rotors includes at least one low pressure rotor drivingly engaged to the low pressure shaft and at least one high pressure rotor downstream of the at least one low pressure rotor and drivingly engaged to the high pressure shaft, the low and high pressure shafts being independently rotatable in a concentric manner, the plenum communicating with the annular gas path in proximity of one of the at least one high pressure rotors. 9. A gas turbine engine comprising: a compressor defining a source of pressurized air;a low pressure shaft engaged to a blade disk of a low pressure turbine by an end bolt located at one end of the low pressure shaft, the low pressure shaft driven by the low pressure turbine;a high pressure shaft driven by a high pressure turbine;a secondary air system including: an inlet passage communicating with the source of pressurized air;an outlet passage defined through the low pressure shaft and by an opening defined through the end bolt, the opening of the end bolt communicating with an environment of the gas turbine engine; anda plurality of additional passages communicating with the inlet passage and with respective components of the gas turbine engine;wherein the outlet passage has a section of constricted internal cross-section defined by a venturi having a single inlet and a single outlet and configured for controlling a flow of the pressurized air through the venturi, the plurality of additional passages communicating with the inlet passage upstream of the venturi,and wherein at least a portion of the pressurized air entering the outlet passage and venturi enters the outlet passage through holes in the low pressure shaft from a passage defined between the low pressure shaft and the high pressure shaft, wherein the holes are located aft of the high pressure turbine with respect to a longitudinal axis of the gas turbine engine. 10. The gas turbine engine as defined in claim 9, wherein the venturi is defined in the opening of the end bolt. 11. The gas turbine engine as defined in claim 9, wherein the compressor includes a plurality of rotors having blades rotatable in an annular flow path, the source of pressurized air being defined by a plenum in fluid communication with the annular flow path of the compressor. 12. The gas turbine engine as defined in claim 10, wherein the plurality of rotors includes at least one low pressure rotor drivingly engaged to the low pressure shaft and at least one high pressure rotor downstream of the at least one low pressure rotor and drivingly engaged to the high pressure shaft, the low and high pressure shafts being independently rotatable in a concentric manner, the plenum communicating with the annular flow path immediately upstream of a most downstream one of the at least one high pressure rotors. 13. A method of pressurizing a secondary air system in a gas turbine engine, the method comprising: circulating pressurized air from a source of pressurized air, through at least one flow path defining a fluid communication between the source of pressurized air and a common outlet communicating with an environment of the gas turbine engine, and to a plurality of interconnected fluid passages communicating with the at least one flowpath;circulating the pressurized air through the fluid passages to deliver the pressurized air to a plurality of components of the gas turbine engine;exhausting the pressurized air from the fluid passages and the at least one flowpath to the environment of the gas turbine engine through the common outlet located downstream of the plurality of components, the at least one flow path including a common fluid passage defining a venturi with a single inlet and a single outlet and configured such that all the pressurized air exhausted through the common outlet circulates through the venturi before being exhausted through the common outlet, the venturi configured for controlling a flow of the pressurized air from the source of pressurized air to the common outlet and through the plurality of fluid passages;at low power, accelerating a flow of the pressurized air through the common fluid passage, the flow being accelerated by circulation through the venturi;and at high power, choking the flow of the pressurized air through the venturi, wherein accelerating and choking the flow controls a pressure drop of the pressurized air throughout the fluid passages;wherein the common fluid passage is defined through a low pressure shaft of the gas turbine engine, the venturi being defined at one end of the low pressure shaft, driven by a low pressure turbine, the communication between the common outlet and the source of pressurized air being provided through the low pressure shaft;wherein at least a portion of the pressurized air entering the common fluid passage and venturi enters the common fluid passage through holes in the low pressure shaft from a passage defined between the low pressure shaft and a high pressure shaft, driven by a high pressure turbine;and wherein the holes are located aft of the high pressure turbine with respect to a longitudinal axis of the gas turbine engine. 14. The method as defined in claim 13, wherein accelerating and choking the flow of the pressurized air is performed downstream of delivering the pressurized air to the plurality of components. 15. The method as defined in claim 13, wherein accelerating and choking the flow of the pressurized air is performed in the low pressure shaft of the gas turbine engine. 16. The method as defined in claim 13, wherein circulating the pressurized air from the source includes circulating the pressurized air from a plenum communicating with a gas path of the gas turbine engine between stages of a high pressure compressor thereof.