Fuel tank ventilation system

Abstract

The present invention relates to a fuel tank ventilation system for an aircraft, the system comprising a fuel collecting tank positioned within the fuselage of the aircraft; a main fuel tank comprising an independent first fuel tank and a second fuel tank, the first fuel tank and the second fuel tank being positioned adjacent to each other and separated by a rib, the first fuel tank being adjacent to the fuel collecting tank; a ventilation fuel tank located on the outside of the second fuel tank and independent of the second fuel tank, the ventilation fuel tank comprising an air inlet; a first ventilation line, the first ventilation line being connected between the second fuel tank and the ventilation fuel tank so that air can enter the second fuel tank from the air inlet via the first ventilation line; a second ventilation line, the second ventilation line being located below the first ventilation line and independent of the first ventilation line, and connected between the second fuel tank and the ventilation fuel tank, the second ventilation line comprising a valve; and a third ventilation line, the third ventilation line being independent of the first ventilation line and the second ventilation line, and connected between the second fuel tank and the first fuel tank through the rib.

Description

Technical Field

[0001] The present invention relates to the field of aircraft fuel tank system design, and in particular to a fuel tank ventilation system suitable for aircraft with a two-fuel tank layout. Background Art

[0002] Aircraft such as the ARJ21-700 model are two-tank layout aircraft. The fuel tanks of such aircraft are usually arranged in the fuselage and on both wings, and the two tanks are arranged symmetrically with rib 0 as the central axis.

[0003] The main function of the fuel tank ventilation system is to ensure that the fuel tank is connected to the atmosphere to avoid the fuel tank from being pressurized. The schematic diagram of the fuel tank ventilation system of a typical two-tank layout civil aircraft is as follows: Figure 1 As shown, this fuel tank ventilation system architecture includes: a fuel collecting tank 1 positioned within the aircraft's fuselage; a main fuel tank comprising an independent first fuel tank 2 (inner fuel tank) and a second fuel tank 3 (outer fuel tank); and a vent tank 4 positioned near the wingtip. For the main fuel tank, the fuel tank ventilation system also includes a long vent pipe 5 connecting the inner area of ​​the main fuel tank with the vent tank, and a vent line 6 with a float vent valve. This vent line is positioned at the interface between the main fuel tank and the vent tank to ensure smooth ventilation of the main fuel tank at any attitude and altitude. To reduce the risk of foreign matter clogging the vent hole and causing tank pressure buildup, two air outlets 7 and 8 are provided at one end of the long vent pipe near the inner area: one outlet 7 is located in the first fuel tank 2, and the other outlet 8 is located in the second fuel tank 3.

[0004] The current method of arranging the vents adjacent to the No. 1 rib on both sides of the interface between the inner and outer fuel tanks has the following problems:

[0005] a) Risk of massive oil overflow from the ventilation system in a lateral overload scenario:

[0006] When the first fuel tank 2 (the fuel tank inside the fuselage) is at a high oil level (as shown by the dotted line), the ventilation system's ability to prevent oil spills is weak. Under lateral overload, the oil level can easily flood the fuel tank vents inside the fuselage, causing an oil spill risk. Especially in the ventilation system flight test assessment, the presence of an oil spill risk is not conducive to the ventilation system passing the airworthiness certification. Take the aircraft's left roll uncoordinated turn scenario as an example. Figure 2 As shown, when the aircraft is lateral overloaded, the oil level is at an angle to the horizontal plane of the fuselage. The vent 7 in the first fuel tank 2 is submerged in fuel, and the left vent tank 4 is located lower than the submerged vent. The fuel in the fuselage will be transferred to the vent tank 4 through the vent pipe 5 and cannot flow back to the second fuel tank (external fuel tank) 3. After this situation continues for a period of time, oil overflow will occur.

[0007] b) The ventilation system is not compatible with the inerting system, which significantly reduces the performance of the inerting system:

[0008] The air inlet 9 of the first fuel tank 2 and the ventilation tank 4 are located in the same ventilation pipe 5, and the vent hole of the first fuel tank 2 is at the end of the ventilation pipe 5. The first fuel tank 2 and the ventilation tank 4 of the outer wing are connected in space. Therefore, during the descent of the aircraft, the external environmental pressure is higher than the gas phase space pressure of the fuel tank. The existing ventilation system architecture has a fuel tank intake process during descent. Figure 3 As shown, the outside fresh air enters the fuel tank through the vent pipe 5. Due to the flow characteristics of the vent pipe 5, excessive fresh air enters the first fuel tank 2 (see Figure 3 The arrow in the middle of the fuselage significantly increases the oxygen concentration in the fuel tank, and the inerting state of the first fuel tank 2 is destroyed. The test flight data shows that the oxygen concentration in the fuel tank of the fuselage exceeds the limit value during the descent process, such as Figure 4 shown.

[0009] Therefore, a fuel tank ventilation system is needed that can reduce the risk of oil spills and is compatible with the inerting system. Summary of the Invention

[0010] In order to solve the problem of oil overflow in the current fuel tank ventilation system, the present invention designs a fuel tank ventilation system, which can eliminate the risk of oil overflow in the ventilation system and avoid excessive dilution of the inert gas in the fuel tank in the fuselage during descent.

[0011] Specifically, this fuel tank ventilation system includes a fuel collecting tank, which is positioned in the fuselage of the aircraft; a main fuel tank, which includes an independent first fuel tank and a second fuel tank, which are positioned adjacent to each other and separated by a rib, and the first fuel tank is positioned adjacent to the fuel collecting tank; a ventilation tank, which is located on the outside of the second fuel tank and independent of the second fuel tank, and the ventilation tank includes an air inlet; a first ventilation line, which is connected between the second fuel tank and the ventilation tank so that air can enter the second fuel tank from the air inlet via the first ventilation line; a second ventilation line, which is located below the first ventilation line and independent of the first ventilation line, and is connected between the second fuel tank and the ventilation tank, and the second ventilation line includes a valve; and a third ventilation line, which is independent of the first ventilation line and the second ventilation line, and is connected between the second fuel tank and the first fuel tank through the rib.

[0012] Preferably, the first vent line extends proximally from the vent tank into the second tank, proximate the rib.

[0013] Preferably, the valve of the second ventilation line is a float valve, which is positioned in the second oil tank.

[0014] In one embodiment, the third ventilation line is a U-shaped tube, which is arranged through the rib at an upper portion of the rib, and an opening of the U-shaped tube is upwardly close to the upper wall plate of the first oil tank.

[0015] In another embodiment, the third ventilation line is an opening, which is provided on the rib and close to the upper wall plate of the first oil tank.

[0016] In yet another embodiment, the third ventilation line is a plurality of through holes, which are provided along the upper portion of the rib between the first oil tank and the second oil tank.

[0017] In various embodiments, the first oil tank is positioned proximate to the front beam, and the oil collecting tank is positioned proximate to the rear beam.

[0018] In addition, the fuel tank ventilation system further includes an NEA distribution line, which extends into the first fuel tank through an upper wall panel of the first fuel tank.

[0019] Additional features and advantages of the described fuel tank vent system will be set forth in the following detailed description, which includes the following detailed description and the accompanying drawings, and will be apparent to those skilled in the art from the following description or learned by practicing the embodiments described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] With reference to the above objects, the technical features of the present invention are clearly described in the following claims, and its advantages are apparent from the following detailed description with reference to the accompanying drawings, which show preferred embodiments of the present invention by way of example without limiting the scope of the inventive concept.

[0021] Figure 1 A bottom view schematically shows a prior art fuel tank venting system for a civil aircraft with a two-tank layout;

[0022] Figure 2 A front view schematic diagram of a fuel tank venting system of the prior art during a left rolling uncoordinated turn flight is shown;

[0023] Figure 3 A schematic diagram showing the fuel tank air intake process of a fuel tank ventilation system in the prior art during a descent process;

[0024] Figure 4 a graph showing the oxygen concentration in the fuel tanks within the fuselage during descent for a prior art fuel tank venting system;

[0025] Figure 5 A bottom view schematically shows a fuel tank venting system according to an embodiment of the present invention;

[0026] Figure 6 A schematic front view of a fuel tank venting system according to an embodiment of the present invention is shown during a left rolling uncoordinated turn flight;

[0027] Figure 7A schematic diagram showing a fuel tank air intake process during a descent of a fuel tank ventilation system according to an embodiment of the present invention is shown;

[0028] Figure 8 A graph showing the oxygen concentration in the fuel tank of the fuselage during descent according to a fuel tank ventilation system according to one embodiment of the present invention;

[0029] Figure 9 A bottom view schematically shows a fuel tank ventilation system according to another embodiment of the present invention;

[0030] Figure 10 A schematic diagram of a fuel tank ventilation system according to another embodiment of the present invention is shown in the case of a left rolling uncoordinated turn flight;

[0031] Figure 11 A front view schematic diagram showing a fuel tank air intake process during a descent of a fuel tank ventilation system according to another embodiment of the present invention; and

[0032] Figure 12 A bottom view schematically shows a fuel tank ventilation system according to yet another embodiment of the present invention.

[0033] Reference numerals

[0034] 1 oil tank

[0035] 2First fuel tank

[0036] 3 Second fuel tank

[0037] 4 vented fuel tank

[0038] 5 ventilator

[0039] 6. Ventilation line

[0040] 7, 8 air outlet

[0041] 9 air intakes

[0042] 10 aircraft

[0043] 11 Zero Rib

[0044] No. 12 rib

[0045] 13 front beam

[0046] 14 Hou Liang

[0047] 15 semi-sealed ribs

[0048] 20 oil collection tanks

[0049] 30 first fuel tank

[0050] 31 Upper wall panel

[0051] 40 Second fuel tank

[0052] 50 vent fuel tank

[0053] 51 air intake

[0054] 100 First ventilation line

[0055] 200 Second ventilation line

[0056] 201 float valve

[0057] 300, 300', 300" third ventilation line

[0058] 400NEA distribution pipeline DETAILED DESCRIPTION

[0059] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings so that the objects, features and advantages of the present invention can be more clearly understood. It should be understood that the embodiments shown in the accompanying drawings are not intended to limit the scope of the present invention, but are only intended to illustrate the essential spirit of the technical solution of the present invention.

[0060] The directional terms “upper”, “lower”, “left”, “right”, “front”, “rear”, etc. used in this document are used to describe the positions of various parts or elements when looking straight at the aircraft.

[0061] The directional terms "near side" and "far side" used in this article are defined according to whether they are close to the center of the fuselage. In other words, "outer side" refers to the direction away from the center of the fuselage, while "inner side" refers to the direction close to the center of the fuselage.

[0062] For ease of explanation, in the following description, the same reference numerals are used to designate the same or similar components.

[0063] Figure 5 A schematic diagram of a fuel tank ventilation system according to an embodiment of the present invention is shown. Note that in order to make the layout of the components of the fuel tank ventilation system clearer, the relative positions and opening directions of the components of the fuel tank ventilation system are schematically shown in this figure. Figure 6 A front view schematic diagram of a fuel tank ventilation system according to an embodiment of the present invention is shown during a left rolling uncoordinated turn flight.

[0064] It should be understood that since the fuel tank vent system of the present invention can be arranged symmetrically on both wings of the aircraft with rib zero 11 as the central axis, this document only describes the fuel tank vent system on the left wing, and the same features can be symmetrically applied to the fuel tank vent system on the right wing.

[0065] like Figure 5As shown, the fuel tank venting system for an aircraft 10 of the present invention includes a collecting tank 20, a main fuel tank, and a vent tank 50. The collecting tank 20 is positioned within the aircraft's fuselage. Specifically, one side of the collecting tank 20 is bounded by the rear spar 12. The main fuel tank includes a first independent tank 30 and a second independent tank 40. The first independent tank 30 is an internal fuel tank, one side of which is bounded by the front spar 11. The collecting tank 20 is positioned adjacent to the first independent tank 30. The second independent tank 40 is an external fuel tank, positioned adjacent to the first independent tank 30 (and the collecting tank 20) ​​and separated by a rib (rib 12 of the aircraft in the figure). The vent tank 50 is located outside and independent of the second independent tank 40. Specifically, it is located at the aircraft's wingtip and separated from the second independent tank 40 by a semi-sealed rib 15. The vent tank 50 includes a ram air intake 51 for receiving fresh air.

[0066] Reference Figure 5 and optionally refer to Figure 6 , shows three independent ventilation lines arranged in the oil collecting tank 20, the first oil tank 30, the second oil tank 40 and the ventilation tank 50: a first ventilation line 100, a second ventilation line 200 and a third ventilation line 300.

[0067] like Figure 6 As shown, the first vent line 100 communicates between the second fuel tank 40 and the vent tank 50, allowing air to enter the second fuel tank 40 from the air inlet 51 of the vent tank 50 via the first vent line 100. Specifically, the first vent line 100 extends proximally from the vent tank into the second fuel tank, near the first rib 12. The opening at one end of the first vent line 100, near the first rib 12, curves upward to prevent oil spillage at the highest possible oil level.

[0068] Continue to refer to Figure 6 The second vent line 200 is located below and independent of the first vent line 100 and communicates between the second fuel tank 40 and the vent tank 50. The second vent line 200 includes a valve, preferably a float valve 201, positioned within the second fuel tank 40. The function of the second vent line 200 is to ensure smooth ventilation of the main fuel tank at any posture and altitude.

[0069] Reference Figure 6 and optionally refer to Figure 7 The third ventilation line 300 is independent of the first ventilation line 100 and the second ventilation line 200 , and passes through the first rib 12 to communicate between the second oil tank 40 and the first oil tank 30 .

[0070] In this embodiment, the third vent line 300 is a U-shaped tube, extending through the rib (rib number 12) at its upper portion. It maintains a sealed separation between the second fuel tank 40 and the first fuel tank 30 on either side of the rib, except for the U-shaped tube. The two legs of the U-shaped tube are perpendicular to the upper wall 31 of the first fuel tank 30, and the opening of the U-shaped tube faces upward, maximally close to the upper wall 31 while maintaining a minimum allowable clearance.

[0071] The fuel tank ventilation system further includes a nitrogen enriched air (NEA) distribution line 400 , which extends through the upper wall plate 31 into the first fuel tank 30 to distribute nitrogen or other inert gas, thereby achieving inerting in the first fuel tank 30 .

[0072] like Figure 6 As shown, if the oil level is high (as shown by the dotted line), in the case of a left rolling uncoordinated turn flight, the U-shaped tube design of the third ventilation line 300 isolates its vent from the vent of the first ventilation line 100, thereby preventing oil from flowing directly from the first fuel tank 30 to the ventilation tank 50, eliminating the risk of oil overflow in the ventilation system caused by the high oil level in the fuel tank inside the fuselage.

[0073] like Figure 7 As shown, if the oil level is low, the U-shaped tube design of the third ventilation line 300 allows only a small portion of the air from the first ventilation line 100 to enter the first oil tank 30, rather than most of the air entering the first oil tank in the existing design (see FIG. Figure 3 This can prevent the inerting state of the fuel tank inside the fuselage from being destroyed, improve the performance of the inerting system, and reduce the flammability of the fuel tank inside the fuselage.

[0074] After adopting the ventilation system architecture of the present invention, the test flight showed that the phenomenon of excessive air intake in the fuel tank of the fuselage during the descent process was significantly suppressed. The oxygen concentration in the fuel tank of the fuselage during the descent phase was always below the limit value of 12% to 14%, and the inert state could be maintained. The performance test flight data of the inerting system corresponding to this patent architecture is as follows Figure 8 shown.

[0075] Figure 9 A schematic diagram of a fuel tank ventilation system according to another embodiment of the present invention is shown. Figure 10 A schematic diagram of a fuel tank ventilation system according to another embodiment of the present invention is shown during a left rolling uncoordinated turn flight.

[0076] Reference Figure 9-10, shows another embodiment of a fuel tank ventilation system including a fuel collecting tank 20, a first fuel tank 30, a second fuel tank 40 and a ventilation tank 50, and three independent ventilation lines arranged in the fuel collecting tank 20, the first fuel tank 30, the second fuel tank 40 and the ventilation tank 50: a first ventilation line 100, a second ventilation line 200 and a third ventilation line 300'.

[0077] The oil collecting tank 20, first oil tank 30, second oil tank 40, ventilation oil tank 50, first ventilation pipeline 100, second ventilation pipeline 200 and their components in this alternative embodiment are the same or similar to those in the previously described embodiment and are therefore not described in detail below. The specific structure of the third ventilation pipeline 300' is described below.

[0078] In this embodiment, the third ventilation pipe 300' is in the form of an opening, which is provided at the upper portion of the first rib 12, close to the upper wall plate 31 of the first oil tank 30. The diameter of the opening is substantially the same as the diameter of the U-shaped pipe in the previous embodiment.

[0079] like Figure 10 As shown, if the oil level is high (as shown by the dotted line), in the case of a left rolling uncoordinated turn flight, the opening isolates its vent from the vent of the first vent line 100, thereby preventing oil from flowing directly from the first fuel tank 30 to the vent tank 50, eliminating the risk of oil overflow in the ventilation system caused by the high oil level in the fuel tank in the fuselage.

[0080] like Figure 11 As shown, if the fuel level is low, this opening allows only a small portion of the air from first vent line 100 to enter first fuel tank 30, rather than the majority of air entering the first fuel tank as in conventional designs. This prevents the inerting state of the in-flight fuel tank from being compromised, improves inerting system performance, and reduces the flammability of the in-flight fuel tank.

[0081] Figure 12 A bottom view schematically shows a fuel tank ventilation system according to yet another embodiment of the present invention.

[0082] Reference Figure 12 The fuel tank ventilation system includes a fuel collecting tank 20, a first fuel tank 30, a second fuel tank 40 and a ventilation tank 50, and three independent ventilation lines arranged in the fuel collecting tank 20, the first fuel tank 30, the second fuel tank 40 and the ventilation tank 50: a first ventilation line 100, a second ventilation line 200 and a third ventilation line 300.

[0083] The oil collecting tank 20, first oil tank 30, second oil tank 40, vent tank 50, first vent line 100, second vent line 200, and their components in this alternative embodiment are identical or similar to those in the previously described embodiments and are therefore not described in detail below. The specific construction of the third vent line 300 is now described.

[0084] The third ventilation line 300" is in the form of a plurality of through-holes. These through-holes are preferably arranged along the upper portion of the rib (rib number 12) between the first fuel tank 30 and the second fuel tank 40. The diameter of the through-holes is smaller than the diameter of the U-shaped tube and the diameter of the opening in the previous embodiment. If the oil level is high, during left roll, uncoordinated turn flight, these through-holes isolate its vent from the vent of the first ventilation line 100, thus preventing oil from flowing directly from the first fuel tank 30 to the vent tank 50 and eliminating the risk of oil overflow in the ventilation system caused by high oil levels in the fuselage fuel tanks. If the oil level is low, these through-holes allow only a small portion of the air from the first ventilation line 100 to enter the first fuel tank 30, rather than the majority of the air entering the first fuel tank as in the existing design. This prevents the inerting state of the in-fuselage fuel tank from being damaged, improves the performance of the inerting system, and reduces the flammability of the in-fuselage fuel tanks.

[0085] Beneficial effects of the above scheme:

[0086] The present invention provides a fuel tank ventilation system for an aircraft, which eliminates the risk of oil overflow in the ventilation system caused by a high oil level in the fuselage fuel tank by isolating the vent of the fuel tank in the fuselage from the ventilation tank; the path for excess fresh air to enter the fuel tank in the fuselage during descent is blocked, thereby preventing the inerting state of the fuel tank in the fuselage from being destroyed, improving the performance of the inerting system, and reducing the flammability of the fuel tank in the fuselage.

[0087] Although the structure and installation method of the present invention have been described above in conjunction with preferred embodiments, those skilled in the art will recognize that the above examples are for illustration only and are not intended to limit the present invention. Therefore, modifications and variations are possible, and all such modifications and variations will fall within the scope of the appended claims.

Claims

1. A fuel tank vent system for an aircraft, the fuel tank vent system comprising: an oil collection tank positioned within the fuselage of the aircraft; a main fuel tank comprising independent first and second fuel tanks, the first and second fuel tanks being positioned adjacent to each other and separated by a rib, and the first fuel tank being positioned adjacent to the fuel collecting tank; a vent oil tank, the vent oil tank being located outside the second oil tank and independent of the second oil tank, the vent oil tank comprising an air inlet; a first ventilation line, the first ventilation line communicating between the second fuel tank and the ventilation tank, so that air can enter the second fuel tank from the air inlet via the first ventilation line; a second ventilation line, the second ventilation line being located below and independent of the first ventilation line and communicating between the second oil tank and the ventilation oil tank, the second ventilation line comprising a valve; and A third ventilation line is independent of the first ventilation line and the second ventilation line and passes through the rib to communicate between the second oil tank and the first oil tank.

2. The fuel tank vent system according to claim 1, wherein: The first vent line extends proximally from the vent tank into the second tank, proximate the rib.

3. The fuel tank vent system according to claim 1, wherein: The valve of the second vent line is a float valve, which is positioned in the second oil tank.

4. The fuel tank vent system according to claim 1, wherein: The third ventilation line is a U-shaped tube, which is arranged through the rib at the upper part of the rib, and the opening of the U-shaped tube is upward and close to the upper wall plate of the first oil tank.

5. The fuel tank vent system according to claim 1, wherein: The third ventilation line is an opening, which is arranged on the rib and close to the upper wall plate of the first oil tank.

6. The fuel tank vent system according to claim 1, wherein: The third ventilation line is a plurality of through holes, which are provided along the upper portion of the rib between the first oil tank and the second oil tank.

7. The fuel tank vent system according to claim 1, characterized in that The first oil tank is arranged close to the front beam, and the oil collecting tank is arranged close to the rear beam.

8. The fuel tank ventilation system according to any one of claims 4 to 6, characterized in that: Also included is an NEA distribution line extending into the first oil tank through an upper wall panel of the first oil tank.

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