# US 7,611,093 B2 · Dual flow APU inlet and associated systems and methods

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- Number: US 7,611,093 B2
- Document ID: US7611093B2
- Status: Granted
- Kind: B2
- Application number: 11/829,497
- Filed: 2007-07-27
- Published: 2008-07-31
- Granted: 2009-11-03
- Earliest claimed: 2004-10-26
- Assignees: The Boeing Company
- Inventors: Thomas A. Campbell; David S. Chambers; Robert H. Willie; Charles W. Rust
- Web page: https://patentgrep.com/patent/US7611093B2

## CPC

- F02C 7/04: Air intakes for gas-turbine plants or jet-propulsion plants
- B64D 41/00: Power installations for auxiliary purposes
- F02C 6/06: providing compressed gas (F02C6/10 takes precedence)
- F02C 7/042: having variable geometry
- B64D 2033/0213: {specially adapted for auxiliary power units (APU's)}
- B64D 2041/002: {Mounting arrangements for auxiliary power units (APU's)}
- Y02T 50/40: Weight reduction
- Y02T 50/60: Efficient propulsion technologies, e.g. for aircraft
- Y10T 137/0536: Highspeed fluid intake means [e.g., jet engine intake]
- F02C: GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS (construction of turbines F01D; jet-propulsion plants F02K; construction of compressors or fans F04; generating combustion products of high pressure or high velocity F23R; using gas turbines in compression refrigeration plants F25B11/00)
- B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

Dual flow auxiliary power unit (APU) inlets and associated systems and methods are disclosed. An inlet in accordance with one embodiment of the invention includes an entrance aperture and a divider positioned in the inlet and located to separate a first portion of the inlet from a second portion of the inlet. The first portion can be configured to couple to an engine air intake of an APU, and the second portion can be configured to direct air away from the air intake. The divider can be positioned to direct air having a first total pressure level and a first distortion level to the first portion of the inlet, and direct air having a second total pressure level and second distortion level to the second portion of the inlet. The first total pressure level can be approximately the same as or higher than the second total pressure level, or the second distortion level can be approximately the same as or higher than the first distortion level, or both.

## Claims

### Claim 1

An inlet system for an aircraft auxiliary power unit, comprising:
an inlet having an entrance aperture; and
a divider positioned in the inlet, the divider being located to separate a first portion of the inlet from a second portion of the inlet, the first portion being configured to couple to an engine air intake of an aircraft auxiliary power unit, the second portion being configured to direct air away from the air intake, the divider being positioned to direct air having a first total pressure level and a first distortion level to the first portion of the inlet, and direct air having a second total pressure level and a second distortion level to the second portion of the inlet, with
(a) the first total pressure level higher than the second total pressure level, and
(b) the second distortion level higher than the first distortion level.

### Claim 2 (depends on 1)

The system of claim 1 wherein the inlet includes an inlet duct elongated in a direction generally transverse to a plane of the entrance aperture.

### Claim 3 (depends on 1)

The system of claim 1, further comprising:
the auxiliary power unit, and wherein the air intake of the auxiliary power unit is coupled to the first portion of the inlet; and
a compartment disposed around the auxiliary power unit, wherein the second portion of the inlet is positioned to direct air into the compartment.

### Claim 4 (depends on 1)

The system of claim 1, further comprising an inlet door positioned at least proximate to the entrance aperture of the inlet, the inlet door being movable relative to the entrance aperture between an open position and a closed position.

### Claim 5 (depends on 1)

The system of claim 1, further comprising an inlet door positioned at least proximate to the entrance aperture of the inlet, the inlet door being movable relative to the entrance aperture between an open position and a closed position, and wherein at least part of the inlet door sealably engages the divider when the inlet door is in the closed position.

### Claim 6 (depends on 1)

The system of claim 1 wherein the divider is a first divider and wherein the system further comprises a second divider positioned to separate a third portion of the inlet from the first and second portions and direct a portion of the air away from the air intake.

### Claim 7 (depends on 1)

The system of claim 1 wherein the inlet has an aperture edge, and wherein the divider is positioned at least approximately parallel to at least a portion of the aperture edge.

### Claim 8 (depends on 1)

The system of claim 1 wherein the inlet has an aperture edge, and wherein the divider is oriented obliquely to the nearest portion of the aperture edge spaced apart from divider.

### Claim 9

An inlet system for an aircraft auxiliary power unit, comprising:
an aircraft fuselage portion;
an inlet having an entrance aperture, the entrance aperture having a first surface portion positioned proximate to a surface of the aircraft fuselage portion, a second surface portion spaced apart from the first surface portion and located aft of the first surface portion, and third and fourth surface portions extending between the first and second surface portions; and
a divider positioned in the inlet and generally aligned with the third surface portion, wherein the inlet includes a first flow channel between the divider and the fourth surface portion, and a second flow channel between the divider and the third surface portion, the first flow channel being configured to couple to an engine air intake of an aircraft auxiliary power unit, the second flow channel being configured to direct air away from the air intake, the first flow channel being positioned to direct air having a first total pressure level and a first distortion level, the second flow channel being positioned to direct air having a second total pressure level and a second distortion level, with
(a) the first total pressure level higher than the second total pressure level, and
(b) the second distortion level higher than the first distortion level.

### Claim 10 (depends on 9)

The system of claim 9 wherein the inlet aperture has a generally rectangular shape.

### Claim 11 (depends on 9)

The system of claim 9, further comprising:
the auxiliary power unit, and wherein the air intake of the auxiliary power unit is coupled to the first flow channel of the inlet; and
a compartment disposed around the auxiliary power unit, wherein the second flow channel of the inlet is positioned to direct air into the compartment.

### Claim 12 (depends on 9)

The system of claim 9, further comprising an inlet door positioned at least proximate to the entrance aperture of the inlet, the inlet door being movable relative to the aperture between an open position and a closed position.

### Claim 13

An inlet system for an aircraft auxiliary power unit, comprising:
an aircraft fuselage portion;
an inlet having an entrance aperture, the entrance aperture having a first surface portion positioned proximate to a surface of the aircraft fuselage portion, a second surface portion spaced apart from the first surface portion and located aft of the first surface portion, and third and fourth surface portions extending between the first and second surface portions; and
a divider positioned in the inlet and generally aligned with the first surface portion, wherein the inlet includes a first flow channel between the divider and the second surface portion, and a second flow channel between the divider and the first surface portion, the first flow channel being configured to be coupled to an engine air intake of an aircraft auxiliary power unit, the second flow channel being configured to direct air away from the air intake, the first flow channel being positioned to direct air having a first total pressure level and a first distortion level, the second flow channel being positioned to direct air having a second total pressure level and a second distortion level, with:
(a) the first total pressure level higher than the second total pressure level; or
(b) the second distortion level higher than the first distortion level; or
(c) both (a) and (b).

### Claim 14 (depends on 13)

The system of claim 13 wherein the inlet aperture has a generally rectangular shape.

### Claim 15 (depends on 13)

The system of claim 13 wherein the inlet includes an inlet duct elongated in a direction generally transverse to a plane of the entrance aperture.

### Claim 16 (depends on 13)

The system of claim 13, further comprising:
the auxiliary power unit, and wherein the air intake of the auxiliary power unit is coupled to the first flow channel of the inlet; and
a compartment disposed around the auxiliary power unit, wherein the second flow channel of the inlet is positioned to direct air into the compartment.

### Claim 17

An inlet system for an aircraft auxiliary power unit, comprising:
an inlet having an entrance aperture; and
separation means for separating flow in the inlet into a first portion directed to an engine air intake of an aircraft auxiliary power unit and a second portion directed away from the air intake, the first portion having a first total pressure level and a first distortion level and the second portion having a second total pressure level and a second distortion level, with
(a) the first total pressure level higher than the second total pressure level, and
(b) the second distortion level higher than the first distortion level.

### Claim 18 (depends on 17)

The system of claim 17 wherein the separation means includes a divider positioned in the inlet.

### Claim 19 (depends on 17)

The system of claim 17 wherein the separation means includes a first divider and a second divider and wherein the first portion of the flow passes between the two dividers.

### Claim 20

An aircraft, comprising:
a fuselage;
a wing;
an auxiliary power unit compartment carried by at least one of the fuselage and the wing;
an auxiliary power unit having an air intake and being housed in the auxiliary power unit compartment;
an inlet having an entrance aperture; and
a divider positioned in the inlet, the divider being located to separate a first portion of the inlet from a second portion of the inlet, the first portion being coupled to the air intake of aircraft auxiliary power unit, the second portion being positioned to direct air away from the air intake and into the auxiliary power unit compartment, the divider being positioned to direct air having a first total pressure level and a first distortion level to the first portion of the inlet, and direct air having a second total pressure level and a second distortion level to the second portion of the inlet, with
(a) the first total pressure level higher than the second total pressure level, and
(b) the second distortion level higher than the first distortion level.

### Claim 21 (depends on 20)

The aircraft of claim 20 wherein the entrance aperture of the inlet for the auxiliary power unit is positioned in an aft portion of the fuselage.

### Claim 22 (depends on 20)

The system of claim 20 wherein the inlet aperture has a generally rectangular shape.

### Claim 23 (depends on 20)

The system of claim 20 wherein the inlet includes an inlet duct elongated in a direction generally transverse to a plane of the entrance aperture.

### Claim 24 (depends on 20)

The system of claim 20 wherein the divider includes a first divider and wherein the system further comprises a second divider, with the first portion of the inlet being positioned between the first and second dividers.

### Claim 25 (depends on 20)

The system of claim 20, further comprising an inlet door positioned at least proximate to the entrance aperture of the inlet, the inlet door being movable relative to the aperture between an open position and a closed position.

### Claim 26

An aircraft, comprising:
a fuselage;
a wing;
an auxiliary power unit compartment carried by at least one of the fuselage and the wing;
an auxiliary power unit having an air intake and being housed in the auxiliary power unit compartment;
an inlet having an entrance aperture, the entrance aperture having a first surface portion positioned to be proximate to a surface of the fuselage, a second surface portion spaced apart from and aft of the first surface portion, and third and fourth surface portions extending between the first and second surface portions;
a first divider positioned in the inlet and generally aligned with the third surface portion;
a second divider positioned in the inlet and generally aligned with the fourth surface portion, wherein the inlet includes a first flow channel between the first and second dividers, a second flow channel between the first divider and the third surface portion, and a third flow channel between the second divider and the fourth surface portion, the first flow channel being coupled to the engine, air intake of the aircraft auxiliary power unit, the second and third flow channels being directed into the auxiliary power unit compartment; and
an inlet door positioned at least proximate to the entrance aperture of the inlet, the inlet door being movable relative to the inlet aperture between an open position and a closed position, and wherein at least part of the inlet door sealably engages the first and second dividers when the inlet door is in the closed position.

### Claim 27 (depends on 26)

The aircraft of claim 26 wherein the entrance aperture of the inlet has a generally rectangular shape.

### Claim 28

A method for providing flow to an aircraft auxiliary power unit, comprising:
receiving flow in an inlet;
providing a first portion of the flow having a first total pressure level and a first distortion level to an engine air intake of an auxiliary power unit; and
directing a second portion of the flow having a second total pressure level and a second distortion level away from the engine air intake, wherein
(a) the first total pressure level is higher than the second total pressure level, and
(b) the second distortion level is higher than the first distortion level.

### Claim 29 (depends on 28)

The method of claim 28 wherein directing a second portion of the flow includes directing a vortex flow away from the engine air intake.

### Claim 30 (depends on 28)

The method of claim 28 wherein directing a second portion of the flow includes directing a vortex while the aircraft operates on the ground.

### Claim 31 (depends on 28)

The method of claim 28 wherein directing a second portion of the flow includes directing a second portion of the flow while the aircraft is in flight.

### Claim 32 (depends on 28)

The method of claim 28 wherein directing a second portion of the flow includes directing the second portion of the flow into a compartment housing the auxiliary power unit.

### Claim 33

A method for providing flow to an aircraft auxiliary power unit, comprising:
receiving a flow of air in an inlet having a first surface portion positioned to be proximate to an aircraft fuselage, a second surface portion spaced apart from the first surface portion, and third and fourth surface portions extending between the first and second surface portions;
a first divider positioned in the inlet and generally aligned with the third surface portion;
a second divider positioned in the inlet duct and generally aligned with the fourth surface portion;
separating flow in a first flow channel between the first and second dividers from flow in a second flow channel between the first divider and the third surface portion, and from flow in a third flow channel between the second divider and the fourth surface portion;
directing the flow in the first flow channel to an engine air intake of an aircraft auxiliary power unit; and
directing the flows in the second and third flow channels to a compartment in which the auxiliary power unit is housed.

### Claim 34

An inlet system for an aircraft auxiliary power unit, comprising:
an inlet having an entrance aperture; and
first and second dividers positioned in the inlet, the dividers being located to separate a first portion of the inlet from second and third portions of the inlet, the first portion being configured to couple to an engine air intake of an aircraft auxiliary power unit, the second and third portions being configured to direct air away from the air intake, the dividers being positioned to direct air having a first total pressure level and a first distortion level to the first portion of the inlet, and direct air having a second total pressure level and a second distortion level to the second portion of the inlet, with
(a) the first total pressure level higher than the second total pressure level, or
(b) the second distortion level higher than the first distortion level, or both (a) and (b).

### Claim 35

An inlet system for an aircraft auxiliary power unit, comprising:
an inlet having an entrance aperture; and
separation means for separating flow in the inlet into a first portion directed to an engine air intake of an aircraft auxiliary power unit and a second portion directed away from the air intake, wherein the separation means includes a first divider and a second divider and wherein the first portion of the flow passes between the two dividers, the first portion having a first total pressure level and a first distortion level and the second portion having a second total pressure level and a second distortion level, with
(a) the first total pressure level higher than the second total pressure level, or
(b) the second distortion level higher than the first distortion level, or both (a) and (b).

### Claim 36

An aircraft, comprising:
a fuselage;
a wing;
an auxiliary power unit compartment carried by at least one of the fuselage and the wing;
an auxiliary power unit having an air intake and being housed in the auxiliary power unit compartment;
an inlet having an entrance aperture; and
first and second dividers positioned in the inlet to separate a first portion of the inlet from a second portion of the inlet, the first portion being positioned between the first and second dividers and being coupled to the air intake of aircraft auxiliary power unit, the second portion being positioned to direct air away from the air intake and into the auxiliary power unit compartment, the divider being positioned to direct air having a first total pressure level and a first distortion level to the first portion of the inlet, and direct air having a second total pressure level and a second distortion level to the second portion of the inlet, with
(a) the first total pressure level higher than the second total pressure level, or
(b) the second distortion level higher than the first distortion level, or both (a) and (b).