GB2545688A

GB2545688A - Aircraft jet pump

Info

Publication number: GB2545688A
Application number: GB1522625.1A
Authority: GB
Inventors: Wheelwright Jay; Vicker-Craddock Jonathan; Telford Kingdom Hutchings Job
Original assignee: Airbus Operations Ltd
Current assignee: Airbus Operations Ltd
Priority date: 2015-12-22
Filing date: 2015-12-22
Publication date: 2017-06-28
Also published as: GB201522625D0

Abstract

An aircraft jet pump 100 in an aircraft fuel system comprises a suction fluid inlet 102, a motive fluid inlet 104 arranged circumferentially around the suction fluid inlet 102, a converging/diverging chamber 106 in communication with both the suction 102 and motive 104 fluid inlets and a jet pump outlet 108 in communication with the converging/diverging chamber 106. In use, motive fluid passes through the motive fluid inlet 104 such that suction fluid is drawn in and entrained through the suction fluid inlet 102 and converging/diverging chamber 106 and directed though the outlet 108. The cross sectional area of the motive fluid inlet 104 may narrow in the direction of motive fluid flow. The suction fluid inlet 102 may comprise a wall 109 extending into the motive fluid inlet 104 and defining an orifice 110. The motive fluid inlet 104 may comprise a circumferential nozzle 112 which may be defined by the wall 109. The circumferential nozzle 112 may be an annular nozzle arranged circumferentially around the wall 109. The suction fluid inlet 102, converging/diverging chamber 106 and outlet 108 may be arranged along a common axis. This arrangement may be less susceptible to blockage by foreign object debris.

Description

AIRCRAFT JET PUMP

FIELD OF THE INVENTION

[0001] The present invention relates to an aircraft pump, an aircraft fuel system and an aircraft comprising the aircraft fuel system. In particular the present invention relates to an aircraft jet pump and a water and/or fuel scavenge system for an aircraft comprising the aircraft jet pump.

BACKGROUND OF THE INVENTION

[0002] Fuel in an aircraft is typically stored in one or more fuel tanks or sealed compartments located in the interior space of the wings and fuselage of the aircraft. Commercial aircraft often employ a centre fuel tank and separate wing fuel tanks. Weight and balance requirements as well as fuel usage by the engines or other operational considerations may require fuel from the centre fuel tank to be burned prior to fuel in the wing fuel tanks. Fuel pumps in the centre fuel tank may not able to completely drain the centre fuel tank and so a separate fuel/water scavenge system may be installed to transfer the small amount of fuel remaining in the centre fuel tank to the wing fuel tanks. The fuel/water scavenge system can also be used to remove the water from the fuel tanks, thereby preventing freezing of the water.

[0003] It is known to use a Venturi nozzle jet pump in the fuel/water scavenging system of an Aircraft. Figure 1 schematically shows a Venturi nozzle jet pump 10. Venturi nozzle jet pump 10 comprises a jet nozzle 12 having an inlet through which motive fluid is received and an outlet aperture 14 of a small diameter, through which the motive fluid is passed into a chamber 16. A suction inlet 18 is provided adjacent to the jet nozzle 12, through which suction fluid is drawn into the chamber 16 when the jet pump 10 is in use. The small diameter of the outlet aperture 14 causes the pressure of the motive fluid to increase as it exits the jet nozzle 12. A converging-diverging chamber 20 is provided in fluid communication with the jet nozzle 12 and the suction inlet 18 and is arranged such that the Venturi effect of the converging-diverging chamber 20 causes the velocity of the high pressure motive fluid to increase, which creates a low pressure zone that draws in and entrains suction fluid through the converging-diverging chamber 20 and out through the outlet of the Venturi nozzle jet pump 10.

[0004] In order for a Venturi nozzle jet fuel pump 10 to operate, it is necessary for the jet nozzle 12 to have a small diameter aperture 14 in order to increase the pressure of the motive fluid to a level, such that there is a large enough pressure decrease as the motive fluid passes through the converging-diverging chamber 20, to draw the suction fluid into the pump.

However, due to the single point constriction in the motive flow caused by the very small aperture 14, Venturi nozzle jet fuel pumps, such as that shown in Figure 1, tend to readily block with very small amounts of Foreign Object Debris (FOD). Further, the entrained suction flow also passes through a relatively small aperture and this too has a tendency to readily block.

[0005] It is therefore desirable to provide an improved aircraft jet pump for use in an aircraft fuel system.

SUMMARY OF INVENTION

[0006] According to a first aspect, there is provided an aircraft jet pump for use in an aircraft fuel system, the aircraft jet pump comprising: a suction fluid inlet; a motive fluid inlet arranged circumferentially around the suction fluid inlet; a converging/diverging chamber in fluid communication with the suction fluid inlet and the motive fluid inlet; and a jet pump outlet in fluid communication with the converging/diverging chamber, wherein in use, motive fluid passes through the motive fluid inlet such that suction fluid is drawn in and is entrained through the suction fluid inlet and converging-diverging chamber, and is directed through the jet pump outlet.

[0007] Traditional venturi nozzle jet pumps, such as jet pump 10 in Figure 1, tend to readily block with very small amounts of FOD due to the single point constriction in the motive flow due to the very small aperture. In the jet pump of the first aspect, the motive flow is provided through an inlet provided circumferentially around the suction fluid inlet. This circumferential inlet is significantly more resilient to FOD due to the lack of single point constriction while the entrained suction flow is through a rather large central orifice, again significantly more resilient to blockage. Should a piece of FOD make its way to the jet pump of the first aspect, a partial blockage can occur in the motive flow, but the jet pump can continue to function with minimal disruption.

[0008] The cross sectional area of the motive fluid inlet may narrow in the direction of motive fluid flow. The suction fluid inlet may comprise a wall portion defining an orifice, the wall portion extending into the motive fluid inlet. The motive fluid inlet may comprise a circumferential nozzle. The wall portion of the suction fluid inlet may be arranged within the motive fluid inlet to define the circumferential nozzle. The circumferential nozzle may be an annular nozzle arranged circumferentially around the wall portion of the suction fluid inlet.

[0009] The suction fluid inlet, the converging/diverging chamber and the jet pump outlet may be arranged along a common axis. As the entrained suction fluid flow is through proceeds through a central inlet (orifice) that is axially arranged with the converging/diverging chamber and the jet pump outlet, the entrained suction fluid flow is resilient to FOD blockage.

[0010] Motive fluid may be provided to the motive fluid inlet from an engine feed boost pump.

[0011] According to a second aspect, there is provided an aircraft fuel system comprising the jet pump according to the first aspect.

[0012] According to a third aspect, there is provided an aircraft fuel scavenge system comprising the jet pump according to the first aspect.

[0013] According to a fourth aspect, there is provided an aircraft water scavenge system comprising the jet pump according to the first aspect.

[0014] According to a fifth aspect, there is provided an aircraft comprising the aircraft fuel system of the second aspect.

[0015] According to a sixth aspect, there is provided an aircraft comprising the aircraft fuel scavenge system of claim of the third aspect.

[0016] According to a seventh aspect, there is provided am aircraft comprising the aircraft water scavenge system of the fourth aspect.

[0017] It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects. For example, the method of the present invention may incorporate any of the features described with reference to the apparatus of the present invention and vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, of which: [0019] Figure 1 schematically shows a prior art jet pump; [0020] Figure 2 schematically shows a cross-section of an aircraft jet pump in accordance with an embodiment; and

[0021] Figure 3 shows a front view of an aircraft in accordance with an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] Figure 2 schematically shows a cross-section of an aircraft jet pump 100 according to an embodiment. Aircraft jet pump 100 comprises a suction fluid inlet 102, a motive fluid inlet 104, a converging/diverging chamber 106 in fluid communication with the suction fluid inlet 102 and the motive fluid inlet 104 and a jet pump outlet 108 in fluid communication with the converging/diverging chamber 106.

[0023] The suction fluid inlet 102 is in fluid communication with a fluid reservoir (not shown) in which fluid to be pumped is retained. In an embodiment, the fluid reservoir is an aircraft fuel tank. The aircraft fuel tank may be a centre fuel tank or a wing fuel tank. The suction fluid may be aircraft fuel. The suction fluid may be water that is present in the fuel tank. The suction fluid inlet 102 comprises a wall portion 109 that defines a suction inlet aperture 110 that allows suction fluid to pass from the suction fluid inlet 102 to the converging/diverging chamber 106. In the embodiment of Figure 2, the wall portion 109 defines a circular suction inlet aperture 110.

[0024] The motive fluid inlet 104 is provided in fluid communication with a motive fluid source (not shown). In an embodiment, the motive fluid source may be an engine feed boost pump, although it will be understood that any other suitable motive fluid source in the aircraft fuel system may be used. The motive fluid may be aircraft fuel. The motive fluid inlet 104 is arranged with a chamber 111 surrounding the wall portion 109 of the suction fluid inlet 102. The chamber 111 is shaped such that a circumferential motive fluid aperture 112 is provided circumferentially around the wall portion 109 of the suction fluid inlet 102. As the suction inlet aperture 110 in Figure 2 is circular, the circumferential motive fluid aperture 112 in Figure 2 is an annular aperture. The circumferential motive fluid aperture 112 may be referred to as a circumferential motive fluid nozzle.

[0025] As motive fluid passes through the motive fluid inlet it is accelerated due to the constricted cross-sectional area of the flow path. In other words, the circumferential motive fluid aperture 112 acts to accelerate the flow of the motive fluid as it passes through the circumferential motive fluid aperture 112, according to Bernoulli’s continuity equation: A1V1 = A2V2

Where: A = Flow area V= Fluid Velocity [0026] In the embodiment of Figure 2, the wall portion 109 of the suction fluid inlet extends at least partially into the converging/diverging chamber 106 such that the circumferential motive fluid aperture 112 is a narrowing aperture. The narrowing of the circumferential aperture 112 causes the motive fluid flow to accelerate further as passes through the aperture 112. For the sake of clarity, it should be understood that in some embodiments, the wall portion 109 does not extend into the converging/diverging chamber 106 and the chamber portion 111 of the motive fluid inlet itself could be shaped to provide the narrowing circumferential aperture 112. Further, it should be understood that in some embodiments, the circumferential aperture 112 need not be a narrowing aperture.

[0027] On leaving the motive fluid inlet, the accelerated motive fluid passes into the converging/diverging chamber 106 and reduces the localized pressure in the region of the suction inlet aperture 110, in accordance with Bernoulli’s equation:

Where: p = Pressure V= Fluid Velocity P = Fluid Density [0028] The localised reduced pressure causes a suction through the suction fluid inlet 102, such that fluid from the fluid reservoir (not shown) is sucked through the suction fluid inlet 102 and is entrained by the motive fluid through the converging/diverging chamber 106, before it is discharged though the jet pump outlet 108.

[0029] As described above, the aircraft jet pump 100 provides motive fluid flow through a circumferential aperture/nozzle 112. The circumferential aperture 112 is significantly more resilient to FOD than the motive fluid nozzle of the Venturi jet pump of Figure 1 in which the aperture 14 can be blocked by a single piece of FOD. This is because the circumferential aperture 112 does not have a single point of constriction. For example, should a piece of FOD make its way to the aircraft jet pump 100 of Figure 2, a partial blockage of the circumferential aperture 112 can occur in the motive flow, but the system can continue to function with minimal disruption.

[0030] Further, as can be seen in Figure 2, the cross-sectional area of the suction inlet aperture 110 is substantially larger than the cross-sectional area of the circumferential motive fluid aperture 112. As the entrained suction flow is through a large central orifice, the suction fluid inlet is more resilient to FOD blockage than the suction fluid inlet 18 of Figure 1. Also, in aircraft jet pump 100, the suction fluid inlet 102, converging/diverging chamber 106 and jet pump outlet 108 are all provided along a common axis, again making the aircraft jet pump 100 more resilient to FOD blockage as the suction fluid does not need to change direction upon entering the jet pump before being ejected, thereby reducing the risk of FOD blockage.

[0031] The aircraft jet pump 100 can ensure continued operation even if it is exposed to an amount of FOD that would block traditional Venturi Jet pumps.

[0032] Aircraft jet pump 100 may be used in the fuel system of an aircraft. Jet pump 100 may be used in the fuel scavenging system of an aircraft and/or the water scavenging system of an aircraft. When aircraft Jet pump 100 is used in the water scavenge system of an aircraft, the burden of regular water drainage tasks can be removed from the Aircraft operator, as the water scavenge system will continue to work regardless of FOD content. In other words, operational interrupt due to necessary water drains can be avoided. When aircraft jet pump 100 is used in a fuel scavenge system of an aircraft, a large amount of unusable fuel can be avoided as the system will continue to scavenge fuel to its designed low levels, even if the aircraft jet pump 100 operates in a fuel tank that is less clean than would be hoped for and contains FOD. In other words, even when the aircraft jet pump is used in the real world of imperfect tank cleanliness, fuel scavenge systems can still operate, resulting in less unusable fuel in aircraft fuel systems and therefore weight saving for the aircraft.

[0033] Although Figure 2 shows a circular suction fluid inlet aperture 110 with corresponding annular motive fluid aperture 112, it will be understood that any suitable shaped apertures may be provided that allows sufficient fluid of suction fluid whilst providing the above mentioned advantages of the embodiments of the present invention.

[0034] Figure 3 shows an aircraft 200 including an embodiment of the fuel system of the present invention. The aircraft has a fuselage 202 and two wings 203 extending from either side of the fuselage 202. Each wing 203 extends in a spanwise direction from a wing root 205 where the wing meets the fuselage 202 to a wing tip 206. Each wing 203 is a dihedral wing, so the wing 203 is angled upwardly as it extends towards the wing tip 206. Engines 204 are located on the underside of each wing 203. Figure 3 shows a single engine 204 on each wing, however the number and location of the engines may vary depending on the type of aircraft.

[0035] Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.

Claims

1. An aircraft jet pump for use in an aircraft fuel system, the aircraft jet pump comprising: a suction fluid inlet; a motive fluid inlet arranged circumferentially around the suction fluid inlet; a converging/diverging chamber in fluid communication with the suction fluid inlet and the motive fluid inlet; and a jet pump outlet in fluid communication with the converging/diverging chamber, wherein in use, motive fluid passes through the motive fluid inlet such that suction fluid is drawn in and is entrained through the suction fluid inlet and converging-diverging chamber, and is directed through the jet pump outlet.

2. An aircraft jet pump according to claim 2 or 3, wherein the cross sectional area of the motive fluid inlet narrows in the direction of motive fluid flow.

3. An aircraft jet pump according to claim 1 or 2, wherein the suction fluid inlet comprises a wall portion defining an orifice, the wall portion extending into the motive fluid inlet.

4. An aircraft jet pump according to claim 3, wherein the motive fluid inlet comprises a circumferential nozzle.

5. An aircraft jet pump according to claim 4, wherein the wall portion of the suction fluid inlet is arranged within the motive fluid inlet to define the circumferential nozzle.

6. An aircraft jet pump according to claim 4 or 5, wherein the circumferential nozzle is an annular nozzle arranged circumferentially around the wall portion of the suction fluid inlet.

7. An aircraft jet pump according to any preceding claim, wherein the suction fluid inlet, the converging/diverging chamber and the jet pump outlet are arranged along a common axis.

8. An aircraft jet pump according to any preceding claim, wherein motive fluid is provided to the motive fluid inlet from an engine feed boost pump.

9. An aircraft fuel system comprising the jet pump according to any of claims 1 to 8.

10. An aircraft fuel scavenge system comprising the jet pump according to any of claims 1 to 8.

11. An aircraft water scavenge system comprising the jet pump according to any of claims 1 to 8.

12. An aircraft comprising the aircraft fuel system according to claim 9.

13. An aircraft comprising the aircraft fuel scavenge system of claim according to claim 10.

14. An aircraft comprising the aircraft water scavenge system of claim according to claim 11.

15. An aircraft jet pump substantially as described with reference to the accompanying drawings.