Inverse modulation of secondary bleed
A cooling arrangement for a gas turbine engine according to an example of the present disclosure includes, among other things, an offtake duct that has an offtake inlet coupled to a cooling source, the offtake duct defining a throat, and a valve downstream of the throat. The valve couples the offtake duct and a first cooling flow path. The valve is operable to selectively modulate flow through the offtake duct. A bleed passage includes a bleed inlet coupling the offtake duct and a second cooling flow path. The bleed inlet is defined at a location between the offtake inlet and the throat, inclusive.
1. A cooling arrangement for a gas turbine engine, comprising:
an offtake duct including an offtake inlet coupled to a cooling source, the offtake duct defining a throat;
a valve downstream of the throat, the valve coupling the offtake duct and a first cooling flow path, the valve operable to selectively modulate flow through the offtake duct;
a bleed passage including a bleed inlet coupling the offtake duct and a second cooling flow path, the bleed inlet defined at a location between the offtake inlet and the throat, inclusive; and
wherein the cooling source is a bypass flow path defined by a fan nacelle.
2. The cooling arrangement as recited in claim 1 , wherein the bleed inlet is defined at the throat.
3. The cooling arrangement as recited in claim 2 , wherein the offtake duct defines a duct axis between the offtake inlet and the valve, the offtake duct converges along the duct axis from the offtake inlet to the throat.
4. The cooling arrangement as recited in claim 3 , wherein the offtake duct diverges along the duct axis from the throat towards the valve.
5. The cooling arrangement as recited in claim 1 , wherein the bleed passage defines a passage axis oriented transversely relative to a localized surface region of the offtake duct.
6. The cooling arrangement as recited in claim 5 , wherein the bleed inlet is spaced from the offtake inlet.
7. The cooling arrangement as recited in claim 1 , further comprising a second valve in the bleed passage.
8. A propulsion system, comprising:
a fan section coupled to a core engine;
a nacelle assembly mounted at least partially about at least one of the core engine and the fan section; and
a cooling assembly comprising:
an offtake duct including an offtake inlet coupled to the nacelle assembly, the offtake duct defining a throat;
a valve coupling the offtake duct and a first cooling flow path, the valve operable to selectively modulate flow through the offtake duct; and
a bleed passage including a bleed inlet coupling the offtake duct and a second cooling flow path, the bleed inlet defined at a location between the offtake inlet and the throat, inclusive; and
wherein the nacelle assembly includes a fan nacelle, and the cooling source is a bypass flow path defined by the fan nacelle.
9. The propulsion system as recited in claim 8 , wherein the offtake inlet is defined at an inner diameter of the bypass flow path.
10. The propulsion system as recited in claim 9 , wherein the offtake inlet is substantially flush with surfaces of the nacelle assembly defining the bypass flow path.
11. The propulsion system as recited in claim 9 , wherein the bleed inlet is spaced from the offtake inlet.
12. The propulsion system as recited in claim 11 , wherein the offtake duct and the bleed inlet are configured such that flow through the first cooling flow path is greater than flow through the second cooling flow path when the valve is in an open position.
13. The propulsion system as recited in claim 12 , wherein the offtake duct defines a duct axis between the offtake inlet and the valve, and the offtake duct converges along the duct axis from the offtake inlet to the throat.
14. The propulsion system as recited in claim 13 , wherein the offtake duct diverges along the duct axis from the throat towards the valve.
15. The propulsion system as recited in claim 13 , wherein the bleed passage defines a passage axis oriented transversely relative to a localized surface region of the offtake duct such that the bleed passage slopes towards an upstream portion of the offtake duct.
16. The propulsion system as recited in claim 8 , wherein the bleed inlet is defined at the throat.
17. The propulsion system as recited in claim 8 , wherein the first cooling flow path is coupled to a first system, the second cooling flow path is coupled to a second system, and the second system is configured to modulate flow through the first cooling flow path.
18. The propulsion system as recited in claim 17 , wherein the bleed inlet is defined at the throat.
19. The propulsion system as recited in claim 8 , wherein the offtake duct and the bleed inlet are configured such that flow through the first cooling flow path is greater than flow through the second cooling flow path when the valve is in an open position.
20. The propulsion system as recited in claim 8 , further comprising a second valve in the bleed passage.