Compressor bleed air system with an actuator driven backflow valve for an aircraft engine

1 . A system for bleeding air from a compressor of an aircraft engine, the system comprising:

a bleed off valve fluidly connected to the compressor;

a plenum downstream of the bleed off valve for receiving bleed air from the compressor via the bleed off valve, the plenum having a first outlet for discharging the bleed air from the plenum into the atmosphere, and a second outlet fluidly connected to the compressor at a location upstream from the bleed off valve relative to a flow of air through the compressor the second outlet in fluid flow communication with piccolo holes define in one or more hollow inlet vanes of the compressor; and

a backflow valve having a closure for selectively closing the first outlet of the plenum, and an actuator operable to displace the closure from a closed position to an open position upon a fluid pressure inside the plenum reaching a pressure threshold, wherein the backflow valve has a larger flow area than a total flow area of the piccolo holes.

2 . The system of claim 1 , wherein the actuator is a fluid driven actuator operatively connected to a source of fluid pressure of the aircraft engine.

3 . The system of claim 2 , wherein the source of fluid pressure is the bleed air inside the plenum.

4 . The system of claim 2 , wherein the fluid driven actuator comprises a piston mounted for reciprocal movement inside a piston housing, the piston dividing the piston housing into a first chamber and a second chamber, the first chamber fluidly connected to the source of fluid pressure, and a biasing member mounted inside the second chamber for biasing the piston towards a first position in which the closure assumes its closed position.

5 . The system of claim 4 , wherein the actuator further comprises a piston rod extending from the piston axially through the first chamber, the piston rod mechanically connected to the closure for causing movement of the closure between its open and closed positions, and wherein the biasing member comprises a spring held captive inside the second chamber against the piston.

6 . The system of claim 1 , wherein the closure includes a metering plate movable in a plane normal to an axis of the first outlet of the plenum.

7 . The system of claim 6 , wherein the metering plate is pivotable about a pivot axis parallel to and offset from the axis of the first outlet of the plenum.

8 . The system of claim 7 , wherein the metering plate is mechanically connected to the actuator via a linkage, the linkage connected to the metering plate at a location spaced from the pivot axis.

9 . An aircraft engine comprising:

a compressor section fluidly connected to an air intake including a plurality of inlet struts, one or more of the inlet struts having piccolo holes; and

a compressor bleed air system including:

one or more bleed off valves for bleeding air from the compressor section;

a plenum in fluid communication with the one or more bleed off valves for receiving compressor bleed air from the one or more bleed off valves, the plenum having a first outlet fluidly connected to the atmosphere and a second outlet fluidly connected to the piccolo holes for reinjecting a portion of the compressor bleed air received in the plenum into the air intake; and

a backflow valve at the first outlet, the backflow valve including a closure displaceable between a closed position in which the first outlet of the plenum is closed and an open position in which the first outlet is opened, and an actuator configured to displace the closure from the closed position to the open position when the piccolo holes are choked;

wherein the actuator is a fluid driven actuator fluidly connected to a source of compressor bleed air and wherein a flow area of the piccolo holes is smaller than that of the backflow valve.

10 . The aircraft engine of claim 9 , wherein the actuator is responsive to an increase of fluid pressure inside the plenum beyond a predetermined pressure threshold.

11 . The aircraft engine of claim 10 , wherein the actuator is a fluid driven actuator having a control port fluidly connected to the plenum.

12 . The aircraft engine of claim 11 , wherein the fluid driven actuator includes a spring-loaded piston having a spring force tuned to maintain the closure in its closed position until a pressure inside the plenum reaches the predetermined pressure threshold.

13 . The aircraft engine of claim 12 , wherein the spring-loaded piston is connected to the closure via a linkage.

14 . The aircraft engine of claim 13 , wherein the closure includes a metering plate mounted for pivotal movement in a plane normal to an axis of the first outlet of the plenum.

15 . The aircraft engine of claim 14 , wherein the metering plate has a pivot axis located outside of a boundary of the first outlet.

16 . The aircraft engine of claim 13 , wherein the closure includes a pair of coplanar plates linearly moveable relative to one another between a first position in which respective airflow passages in the coplanar plates are aligned and a second position in which their respective air flow passages are offset.

17 . An aircraft engine comprising:

a compressor section fluidly connected to an air intake including a plurality of inlet struts, one or more of the inlet struts having piccolo holes; and

a compressor bleed air system including:

one or more bleed off valves for bleeding air from the compressor section;

a plenum in fluid communication with the one or more bleed off valves for receiving compressor bleed air from the one or more bleed off valves, the plenum having a first outlet fluidly connected to the atmosphere and a second outlet fluidly connected to the piccolo holes for reinjecting a portion of the compressor bleed air received in the plenum into the air intake; and

a backflow valve at the first outlet, the backflow valve including a closure displaceable between a closed position in which the first outlet of the plenum is closed and an open position in which the first outlet is opened, and a fluid driven actuator configured to displace the closure from the closed position to the open position when the piccolo holes are choked, the fluid driven actuator having a control port fluidly connected to the plenum, the fluid driven actuator responsive to an increase of fluid pressure inside the plenum beyond a predetermined pressure threshold, the fluid driven actuator including a spring-loaded piston having a spring force tuned to maintain the closure in its closed position until a pressure inside the plenum reaches the predetermined pressure threshold, and wherein the spring-loaded piston is connected to the closure via a linkage.

18 . A system for bleeding air from a compressor of an aircraft engine, the system comprising:

a bleed off valve fluidly connected to the compressor;

a plenum downstream of the bleed off valve for receiving bleed air from the compressor via the bleed off valve, the plenum having a first outlet for discharging the bleed air from the plenum into the atmosphere, and a second outlet fluidly connected to the compressor at a location upstream from the bleed off valve relative to a flow of air through the compressor; and

a backflow valve having a closure for selectively closing the first outlet of the plenum, and an actuator operable to displace the closure from a closed position to an open position upon a fluid pressure inside the plenum reaching a pressure threshold, the closure including a metering plate movable in a plane normal to an axis of the first outlet of the plenum, the metering plate pivotable about a pivot axis parallel to and offset from the axis of the first outlet of the plenum.