Device for cleaning fuel and use thereof

Abstract

The invention relates to a device (1) for cleaning fuel in a tank (92) of an aircraft (90), and use thereof. The device has a predetermined flow direction (2) for the fuel and comprises units arranged in a fluid-connected manner to forward the fuel from one to another, namely: – an extraction unit (10) for extracting fuel from a tank (92) of an aircraft (90); - a filter unit (30) for filtering the extracted fuel; and - a recirculation unit (70) for returning the filtered fuel to the tank (92) of the aircraft (90), comprising a hose (71) for selective fluid connection of the device (1) to the tank (92) of the aircraft (90), wherein a pump (80) is provided for conveying the fuel at least through the hose (71) of the recirculation unit (70).

Description

[0001] Device for cleaning fuel and its use

[0002] The invention relates to a device for cleaning fuel in an aircraft tank and to the use thereof.

[0003] Contamination can occur in aircraft fuel tanks. In addition to contaminants such as metal shavings, pieces of sealing compound and other production or maintenance residues that have entered the tank through openings, for example during refueling or maintenance, bacteria, mold and fungi can form in the tank, particularly when aircraft are idle for extended periods. These fungi - at least if they are not firmly attached to the inside of the tank - can also result in fuel contamination. At the latest when microbial contamination of the inside of the tank is treated with suitable, toxic biocides known from the state of the art, the fuel is contaminated by biomass - in the form of killed microbes. Excretions from still living microbes can also lead to fuel contamination.

[0004] To prevent fuel contaminants from reaching the aircraft's engine, fuel filters are known that filter out solids above a specified size from the fuel during operation. A disadvantage of this state-of-the-art technology is that, particularly in cases of severe fuel contamination, the fuel filter can become clogged during operation, which poses a safety risk.

[0005] If there is significant contamination of the tank or the fuel it contains, particularly by microbes, it is known - particularly to avoid the risk of filter clogging - to clean the affected tank by opening the tank and conducting a tank inspection. Such tank inspections are complex, which is why they can only be carried out by specially qualified and trained personnel. They usually take several days, also due to upstream defueling and ventilation steps, during which a space in a hangar is regularly occupied continuously.

[0006] The object of the present invention is to provide a device for cleaning fuel in an aircraft tank and the use thereof, in which the disadvantages known from the prior art no longer occur or only occur to a reduced extent.

[0007] This object is achieved by a device according to the main claim and its use according to the subordinate claim. Advantageous further developments are the subject of the dependent claims.

[0008] Accordingly, the invention relates to a device for cleaning fuel in a tank of an aircraft, with a flow direction for the fuel and fluid-connected units for forwarding the fuel, comprising in the flow direction:

[0009] - a withdrawal unit for withdrawing fuel from an aircraft tank;

[0010] - a filter unit for filtering the extracted fuel; and a return unit for returning the filtered fuel to the aircraft tank, comprising a hose for selectively fluidly connecting the device to the aircraft tank, a pump being provided for conveying the fuel at least through the hose of the return unit.

[0011] Furthermore, the invention relates to the use of the device according to the invention, in which the extraction unit (10) and the return unit (70) are connected to the same tank of an aircraft.

[0012] First, some terms used in connection with the invention will be explained.

[0013] A "predetermined flow direction" through a device is the direction along which a fluid - in this case fuel - mainly flows through its individual units when the device is used correctly. The flow direction does not provide any information about the actual flow direction of the fluid within the device, but merely serves to identify the order in which the fluid flows through the individual units. It is also not excluded that the fluid may be at rest in some areas and / or temporarily or may even flow against the flow direction.

[0014] Two units are "fluidly connected" if the units are connected in such a way that a fluid can flow from one unit to the other, particularly in the specified flow direction.

[0015] The device according to the invention creates the possibility of cleaning the fuel in the tank of an aircraft on the ground using a circulation process with little effort in order to filter out any solids that may be present in the fuel, so that the aircraft's fuel filter is relieved during operation of the aircraft: If at least some, preferably a large part of the solids in the fuel have already been removed from the fuel by the device according to the invention, fewer solid particles have to be filtered out by the aircraft's fuel filter during operation. The reliability of the fuel filter and thus of the aircraft's fuel supply during operation is thereby increased. The early removal of fuel contamination also counteracts contamination of the interior surfaces of the tank, thus reducing the risk of damage to the aircraft, e.g.by corrosion occurring or at least accelerated due to contamination.

[0016] The device according to the invention comprises - in the order in which the flow passes through the units in the flow direction predetermined for the device - at least one extraction unit, a filter unit and a return unit, wherein the units are each fluidly connected to one another. The fuel from the tank of an aircraft reaches the device according to the invention via the extraction unit and then passes through the filter unit, in which the fuel is filtered, i.e. freed from solid particles above a predetermined size. The filtered fuel is then returned to the tank of the aircraft from which the fuel originally originated via a return unit and a hose. The device comprises a pump, with which the filtered fuel can be pumped back into the aircraft tank.

[0017] The pump can be part of the recirculation unit. In this case, the flow through the units upstream of the recirculation unit, such as the filter unit, can be ensured by gravity, by additional pumping devices, or by the suction effect of the recirculation unit's pump.

[0018] Alternatively, it is possible to arrange the pump at a different location within the device, for example, upstream of the filter unit in the flow direction. With such an arrangement, it is only necessary to ensure that the pump also pumps the fuel through at least the hose of the return unit.

[0019] If the device is designed accordingly, the fuel can be cleaned continuously in direct circulation, i.e. fuel that has been removed via the removal unit is returned to the tank via the return unit immediately after passing through the filter unit or the device. However, it is also possible to provide an intermediate storage unit between the filter unit and the return unit of the device, with which the filtered fuel can be briefly stored in an intermediate storage unit before it is returned. By means of appropriate intermediate storage, the return of the fuel can take place at a time staggered from the removal of the fuel, which can reduce the mixing of uncleaned fuel that has not yet been removed and the already filtered, returned fuel in the aircraft tank.If the intermediate storage tank is sufficiently large, the return can only take place after the fuel has been completely removed from the aircraft tank, so that the mixing mentioned is completely avoided.

[0020] The intermediate storage unit can directly comprise an intermediate storage device, for example in the form of a tank. However, it is preferred if the intermediate storage unit comprises a connection module for connecting an external intermediate storage device, such as the tank of a tanker vehicle. As the actual intermediate storage device is not a direct part of the intermediate storage unit, this, like the entire device, can be made smaller and therefore easier to handle. An external intermediate storage device then only needs to be connected to the connection module of the intermediate storage device if an intermediate storage device is actually required for a specific cleaning process. It is also possible for the intermediate storage module to have its own intermediate storage device and a connection module. If necessary, a further intermediate storage device can then be connected via the connection module to expand the storage volume.In addition to at least one connection for connecting an external buffer storage device, the connection module can comprise a pump for pumping fuel into and / or out of the buffer storage device.

[0021] The withdrawal unit is preferably connected to the aircraft tank independently and separately from the return unit, as will be explained below. However, it is also possible to use the return unit's hose to withdraw the fuel from the tank, for example in aircraft tanks with only one or at least only one easily accessible tank opening. In this case, a switching module can be provided with which the return unit hose can be fluidly connected not only to the return unit but also to the withdrawal unit. The hose can therefore be used for fuel withdrawal and return as required. Since withdrawal and return cannot take place simultaneously in this case, an intermediate storage unit will generally have to be provided for this variant.

[0022] As an alternative to using the hose of the return unit, the extraction unit can comprise at least one hose fluidly connected thereto for fluid coupling to a fuel drain opening and / or another opening of the fuel tank. A "fuel drain opening" is an opening on the fuel tank that is located at the lowest point(s) of the fuel tank when an aircraft is parked on a level surface, so that the fuel escapes from it due to gravity when the fuel drain opening is open. To connect the hose of the extraction unit, it may be sufficient if a funnel is provided at its free end to collect the fuel escaping from the fuel drain opening.However, to reduce the risk of fire, it is also preferable if a hose coupling is provided at the free end of the hose of the extraction unit, with which the hose can be sealed to an opening in the fuel tank.

[0023] As already explained, the fuel can be withdrawn from the fuel tank of an aircraft purely by gravity. However, it is also possible for the withdrawal unit to be designed to extract fuel through at least one hose that is fluidically connected to the withdrawal unit. Such extraction can both support a fundamentally possible fuel extraction by gravity and also allow fuel to be withdrawn through openings in the fuel tank through which gravity extraction is fundamentally not possible. The hose can have a hose coupling at its free end for connection to an opening in the aircraft tank or can be designed as a suction hose for open aircraft tanks. By means of suction, the flow rate of fuel through at least one hose can also be controlled. Preferred flow rates are 0.3 m / s to 7 m / s, preferably 2 m / s to 3 m / s.Extraction can be achieved solely through the suction action of the pump designed to convey the fuel through the return unit's hose. Alternatively, the extraction unit may include a separate extraction pump.

[0024] It is preferred if a water separation unit for separating water from the extracted fuel is arranged in fluid connection upstream or downstream of the filter unit in the direction of flow. The water separation unit can remove any water contained in the fuel, which could, for example, cause corrosion on metal parts that come into contact with the fuel. The separation of water and fuel can, for example, be achieved in a known manner by swirling. In this case in particular, it is preferred if the water separation unit is externally driven so that the swirling required for water separation does not depend on the flow rate of the fuel through the water separation unit. The water separation unit can also be sensor-controlled in order to be able to adapt the operating parameters of the water separation unit to the actual water content in the fuel.

[0025] If it can be assumed that the fuel and any water present are already present in the tank in separate phases and are also drawn off separately from one another, the water separation unit can also be designed as a sensor-controlled three-way valve with one inlet and two switchable outlets. If a suitable sensor in the water separation unit detects that water is flowing in at the valve inlet, the valve can be set to one outlet which is, for example, connected to a collecting container; if fuel is detected at the valve inlet, the valve can be set to the outlet via which the fuel reaches the unit arranged downstream of the water separation unit in the direction of flow, e.g. the filter unit.

[0026] The filter unit can comprise one or more filters connected in series. The filter or filters can preferably have a fineness of 0.2 gm to 15 gm, with the fineness of several filters connected in series preferably decreasing in the predetermined flow direction, so that filtration occurs from coarse to fine. To filter out microbiological components in the fuel, a filter fineness of 0.2 gm should generally be aimed for. Depending on the tank volume and contamination level, a filter with this fineness can become clogged quickly, which means that such a filter is only suitable for certain applications.

[0027] The filters can be made of any material suitable for use with aviation fuels. The filters are preferably made of metal to ensure a long service life.

[0028] It is preferred if the filter unit has one or more filter sampling points. Samples of the fuel flowing through the filter unit can be taken via corresponding sampling points in order to analyze the fuel in the laboratory and, for example, to evaluate the function of the filter unit or the entire device.

[0029] The filter unit can include a differential pressure measuring device, which measures the differential pressure before and after the filter unit or individual filters within it. The differential pressure can be used to detect a blockage of the filter unit or an individual filter within it. By observing the increase in the differential pressure over the filtered fuel volume, initial conclusions can be drawn about the degree of fuel contamination.

[0030] A UV disinfection unit can be arranged in fluid connection downstream of the filter unit in the flow direction. Such a UV disinfection unit can kill or inactivate microbes in the fuel that, due to their size, were not filtered out by the filter unit.

[0031] The device can also comprise at least one conductivity measuring unit for measuring the conductivity of the fuel flowing through the device. By measuring the conductivity, for example, after the filter unit, it can be verified whether the purified fuel meets the conductivity requirements for aircraft fuel.

[0032] The device can also include a mixing unit for admixing additives to the fuel flowing through the device. For example, additives to increase the conductivity of the fuel (Static Dissipator Additive SDA) can be added, for example, depending on a conductivity measurement. Biocides to kill microbes still present in the fuel tank and / or antifreeze (FS II, Fuel System Icing Inhibitors or antifreeze) can also be added.

[0033] The hose of the return unit and / or a hose of the withdrawal unit can have a known aircraft refueling coupling at its free end to ensure a simple and secure connection of the device to the aircraft tank. The aircraft refueling coupling can be a standard component and / or a coupling tailored to a specific aircraft type. One or more adapters can also be provided to enable the aircraft refueling coupling at the free end of the hose of the return unit to be connected to different aircraft types. In particular, an aircraft refueling coupling corresponding to the civil standard SAE AS5887 can preferably be provided at the free end of a hose of the return unit and / or the withdrawal unit.

[0034] The device can preferably have a central control unit, which controls the controllable units or their controllable components, possibly providing measured values ​​or the like that provide information about the cleaning process or the function of the individual units. The control unit can be programmable, for example, to carry out fuel cleaning in a manner tailored to specific aircraft or their tanks.

[0035] The device can preferably be mounted entirely on a frame so that it is easily transportable, for example, by air. It can also be mounted directly on a vehicle.

[0036] Furthermore, the device can have its own energy source, for example, an accumulator or a generator. Alternatively, the device can be designed for connection to an existing energy network, for example, a hangar power supply.

[0037] For an explanation of the use according to the invention, reference is made to the above explanations. Any units of the device used are generally operated as intended. The only exception to this is the intermediate storage unit, if present. Even if an intermediate storage unit is provided which basically makes it possible to decouple the return of fuel from its removal, direct circulation cleaning can also be achieved with a corresponding device by ensuring that the intermediate storage always remains empty through suitable control of the various units and their components.

[0038] Irrespective of this, in the use according to the invention - depending on the desired cleaning - the removal and / or return of fuel from or into the tank of an aircraft can be carried out continuously or intermittently.

[0039] The invention will now be described by way of example using an advantageous embodiment with reference to the accompanying drawings. In the drawings:

[0040] Figure 1: a schematic representation of the use of a first embodiment of a device according to the invention;

[0041] Figure 2 : a schematic detailed representation of the device according to the invention according to Figure 1 ; and

[0042] Figure 3 : a schematic detailed representation of a second

[0043] From an exemplary embodiment of a device according to the invention.

[0044] Figure 1 schematically shows the use of a first embodiment of a device 1 according to the invention, which is shown in detail in Figure 2, for cleaning fuel in the tank 92 of an aircraft 90. The tank 92 is integrated into the wing 91 of the aircraft 90.

[0045] The device 1 is connected to a fuel drain opening of the tank 92 of the aircraft 90 by a hose 11 associated with its extraction unit 10. For this purpose, the hose 11 has an adapter at its free end for connection to a tank bottom valve, which is arranged at the lowest point of the tank 92.

[0046] Furthermore, in front of the device 1, a hose 71 associated with the return unit 70 is connected to a tank opening that is normally used for refueling the aircraft 90. For this purpose, the hose 71 has an aircraft refueling coupling 72 at its free end in accordance with the SAE AS5887 standard.

[0047] For the device 1, a basic flow direction 2 for the fuel is specified, namely from the tank 92 through the hose 11 of the extraction unit 10 back into the tank 92 via the hose 71 of the return unit 70. Along this flow direction 2, the fuel in the device 1 passes through various units 10, 20, 30, 40, 50, 60, 70 that are fluidly connected in series with one another, which are explained in more detail below with reference to Figure 2.

[0048] The extraction unit 10 comprises a suction pump 13, with which fuel is sucked through the hose 11. Regardless of whether the fuel would flow through the hose 11 on its own due to gravity, the suction pump 13 ensures a constant fuel flow of approximately 1 m / s through the hose 11. The suction pump 13 also ensures a constant fuel flow through the units following the extraction unit 10.

[0049] A water separation unit 20 is provided adjacent to the extraction unit 10. The water separation unit 20 comprises a filter-water separator, preferably with an automatic drain 21. The water separation unit 20 can also comprise a sensor (not shown) for determining the water content of the fuel flowing into or out of the filter-water separator 21.

[0050] The fuel then enters a filter unit 30. In the illustrated embodiment, the filter unit 30 comprises two filters 31, 32 connected in series, the filter 31 through which the flow passes first in the flow direction 2 having a fineness of 5 pm, while the other filter 32 has a fineness of 1 pm. Between the two filters 31, 32, which are made of metal, there is a filter sampling point 33 with which samples of the fuel that has been partially filtered - namely only through the first filter - can be taken in order to examine them in the laboratory. For example, such an examination can be used to determine whether the ratio of the finenesses of the two filters 31, 32 has been selected sufficiently to ensure an adequate filtering result on the one hand, and to avoid premature clogging of one of the two filters 31, 32 on the other.If the first filter 31 is too fine compared to the second filter 32, which largely determines the overall filtering result, the first filter 31 may clog quickly; if the first filter 32 is too coarse, the second filter 32 will clog sooner. Ideally, the fineness of the filters 31 and 32 should be selected so that they clog at a similar rate.

[0051] The filter unit 30 further comprises a pressure difference measuring device 34, with which the pressure difference upstream of the first filter 31 and downstream of the second filter 32 is detected. Based on the pressure difference, possible blockages in one of the two filters 31, 32 can be detected and, for example, a warning can be issued prompting the cleaning or replacement of the filters 31, 32. As an alternative to a common pressure difference measuring device 34, a pressure difference measuring device can also be provided separately for each filter 31, 32.

[0052] Following the filter unit 30, a UV disinfection unit 40 is provided, in which fuel flowing through is exposed to UV radiation, in particular UVC radiation, along a UV disinfection section 41, with which any vegetative microbes contained in the fuel are killed or inactivated even after filtering.

[0053] Adjacent to this is a mixing unit 50, into which an additive—in this case, an additive for increasing conductivity—can be added from the reservoir 52 via a controllable valve 51 as needed. A conductivity measuring unit 53 is provided to measure the amount of additive added. Based on the measured conductivity of the fuel after the UV disinfection unit 40, the additive addition can be specifically controlled via the valve 51.

[0054] After the mixing unit 50, the fuel reaches an intermediate storage unit 60. The intermediate storage unit 60 comprises an intermediate storage 61 in which a certain amount of fuel can be temporarily stored in order to be able to fundamentally decouple the withdrawal of fuel and its return. In the event that the intermediate storage 61 should not be sufficient, the intermediate storage unit 60 also comprises a connection module 62 with which, if necessary - and therefore only shown in dashed lines - an external tank 95, for example the tank 95 of a tank truck 96, can be connected with a hose 97 if required (see Figure 1). The connection module 62 comprises a pump device with which fuel can be transferred from the intermediate storage 61 into the connected tank 95 and vice versa.Fuel to be returned from the intermediate storage 61 of the intermediate storage unit 60 to the tank 92 of the aircraft 90 is pumped back through the return unit 70 and its hose 71. For this purpose, the return unit 70 comprises a suitable pump 80.

[0055] The mode of operation of the device 1 follows directly from the above: fuel withdrawn via the withdrawal unit 10 passes through the various purification units - water separation unit 20, filter unit 30 and UV disinfection unit 40, before an additive to increase conductivity is added to the fuel in the admixing unit 50 if required and the fuel thus purified and having a desired conductivity is temporarily stored in the intermediate storage unit 60 - either in its intermediate storage 61 or in the external tank 95. From the intermediate storage unit 60, the fuel is then returned to the tank 92 of the aircraft 90 via the return unit 70 or pumped back using the pump 80.Depending on the type of cleaning required, an immediate return can take place, whereby the intermediate storage 61 remains practically empty and the device 1 carries out a circulating cleaning; however, it is also possible to temporarily store part or even all of the fuel from the tank 92 and thus decouple the removal and return of the fuel in time.

[0056] A central control unit (not shown) can be provided to control the above-described controllable components of the individual units 10-70 and the pump 80. This central control unit can also be connected to the various sensors, etc., in order to control the functions of the individual units 10-70 and the device 1 as a whole. The control unit can be programmable, whereby individual cleaning sequences tailored to specific aircraft or their tanks 92 can be programmed.

[0057] As shown in Figure 1, the device 1 can be arranged on a trolley. For power supply, the device 1 has a connection (not shown) for the power grid of a hangar.

[0058] Figure 3 shows a second exemplary embodiment of a device 1 according to the invention. The device 1 can be used in accordance with Figure 1, but compared to the device 1 in Figure 2, it has only the minimum number of required units 10, 30, 70.

[0059] In the flow direction 2, a withdrawal unit 10 is initially provided in the device 1, to which the pump 80 is connected, before fuel flowing through the device flows through a filter unit 30 and is then returned via the return unit 70 and its hose 71 into the tank 92 of the aircraft 90 from which the fuel was withdrawn (cf. Figure 1).

[0060] While the filter unit 30 in the device 1 according to Figure 3 is constructed identically to the filter unit 30 of the device 1 from Figure 2, for which reason reference is made to the explanations there, the extraction unit 10 and the return unit 70 are designed as purely passive units: the extraction unit 10 does not comprise a suction pump 13 (cf. Figure 2), the pump 80 is arranged outside the return unit 70.

[0061] In order to ensure the flow direction 2 of the device 1 and at least the return of the fuel, the pump 80 is provided, which is arranged upstream of the filter unit 30 in the flow direction 2. The pump 80 is designed such that it delivers sufficient fuel across the filters 31, 32 of the filter unit 30, at least up to a defined pressure drop, so that the filtered fuel can be returned through the hose 71. Of course, the pump 80 is also designed such that it does not become clogged by the impurities to be expected in the fuel.

[0062] In the illustrated embodiment according to Figure 3, the fuel can be extracted solely by gravity. However, the pump 80 can also be designed to exert a suction effect through the hose 11 of the extraction device 10.

[0063] The device 1 according to Figure 3 can also have a central control device (not shown) with which proper operation of the device 1 is ensured.

Claims

Patent claims 1. Device (1) for cleaning fuel in a tank (92) of an aircraft (90), with a predetermined flow direction (2) for the fuel and units arranged in fluid communication with one another for the forwarding of the fuel, comprising in the flow direction (2): - a withdrawal unit (10) for withdrawing fuel from the tank (92) of an aircraft (90); - a filter unit (30) for filtering the extracted fuel; and - a return unit (70) for returning the filtered fuel to the tank (92) of the aircraft (90), comprising a hose (71) for selectively fluidly connecting the device (1) to the tank (92) of the aircraft (90), wherein a pump (80) is provided for conveying the fuel at least through the hose (71) of the return unit (70).

2. Device according to claim 1, characterized in that an intermediate storage unit (60) for intermediate storage of fuel in an intermediate storage unit (61) is provided between the filter unit (30) and the return unit (70).

3. Device according to claim 2, characterized in that the intermediate storage unit (60) is a connection module (62) for connecting an external intermediate storage device (95). Device according to claim 2 or 3, characterized in that a switching module is provided, with which the hose (71) of the return unit (70) can be selectively fluidically connected to the extraction unit (10). Device according to one of the preceding claims, characterized in that the extraction unit (10) comprises at least one hose (11) fluidly connected thereto for fluid coupling to a fuel drain opening and / or a tank opening of the tank (92). Device according to one of the preceding claims, characterized in that the extraction unit (10) has a suction pump (13) for sucking out fuel through at least one hose (11, 71) fluidly connected to the extraction unit (10), with which suction pump, preferably controlled flow velocities of fuel through the at least one hose (11, 71) of 0.3 m / s to 7 m / s, preferably of 2 m / s to 3 m / s, can be produced.Device according to one of the preceding claims, characterized in that a water separation unit (20) for separating water from the withdrawn fuel is arranged in a fluid-connected manner upstream or downstream of the filter unit (30) in the flow direction (2), wherein the water separation unit (20) is preferably externally driven (22) and / or sensor-controlled.

8. Device according to one of the preceding claims, characterized in that the filter unit (30) comprises one or more series-connected filters (31, 32) with a fineness of 0.2 pm to 15 pm and / or made of metal.

9. Device according to one of the preceding claims, characterized in that the filter unit (30) has one or more filter sampling points (33).

10. Device according to one of the preceding claims, characterized in that the filter unit (30) comprises a differential pressure measuring device (34).

11. Device according to one of the preceding claims, characterized in that a UV disinfection unit (40) is arranged in fluid connection downstream of the filter unit (30) in the flow direction (2).

12. Device according to one of the preceding claims, characterized in that the device (1) comprises at least one conductivity measuring unit (53) with which the conductivity of the fuel flowing through the device (1) can be measured.

13. Device according to one of the preceding claims, characterized in that the device (1) comprises a mixing unit (50) for mixing additives into the fuel flowing through the device (1).

14. Use of the device according to one of claims 1 to 13 for cleaning in a tank (92) of an aircraft (90) located fuel, wherein the extraction unit (10) and the return unit (70) is connected to the same tank (92) of an aircraft (90). Use according to claim 14, characterized in that the removal and / or return of fuel from or into the tank (92) of an aircraft (90) occurs continuously or intermittently.

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