EP3841295A1

EP3841295A1 - Fuel system

Info

Publication number: EP3841295A1
Application number: EP19762312.7A
Authority: EP
Inventors: Michael Bippes; Thomas Garbe
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 2018-08-23
Filing date: 2019-08-20
Publication date: 2021-06-30
Also published as: WO2020038529A1; DE102018120589A1

Abstract

The invention relates to a fuel system (1) comprising a fuel tank (2) and a main flow branch (3) leading into the fuel tank (2) and through which a fluid mixture flows, wherein a separation device (4) for a fluid containing the fluid mixture is arranged in the main flow branch (3). The fluid is a reaction fluid that chemically reacts with a fuel, parts or constituents of the fuel stored in the fuel tank (2), and the separation device (4) comprises a storage element (5) for separating said reaction fluid from the fluid mixture and receiving same.

Description

description

Fuel System

The invention relates to a fuel system with a fuel tank and a main flow branch through which a fluid mixture can flow and which opens into the fuel tank. Here, a separating device for a fluid containing the fluid mixture is arranged in the main flow branch.

The use of fossil fuels such as petrol or diesel fuels in

Internal combustion engines, with the emission of combustion gases into the environment, have the well-known disadvantage of releasing carbon dioxide into the atmosphere.

In the case of diesel fuels in particular, combustion also occurs when

Associated pollutants in the form of soot particles and nitrogen oxides, the amount of these pollutants in the combustion exhaust gas before the emission into the environment by means of combustion downstream, each matched to the pollutant exhaust gas cleaning processes must be significantly minimized. The downstream of the combustion

Exhaust gas purification processes are caused in particular by the fact that such a quantity is present between the amount of pollutants that arise during combustion

There is an interaction, so that the combustion process can practically not be optimized with regard to a quasi-absolute minimum of both pollutants. For example, high temperatures promote the combustion of soot particles and thus their minimization, but the amount of nitrogen oxides produced increases in a coherent manner.

In view of the above-mentioned disadvantages, efforts to provide an alternative, in particular for diesel fuel, prove to be sensible. Such

An alternative to the partial or complete replacement of diesel fuel is

Polyoxymethylene dimethyl ether, also called oxymethylene ether or OME in short. OME burns almost soot-free, which means that the combustion process in the engine is reduced to one

Minimization of nitrogen oxide emissions can be optimized. It is also possible to use OME with regard to a closed and therefore neutral carbon dioxide cycle

use. For this purpose, the production of OME from carbon dioxide and water separated from the atmosphere is provided, the energy to be used for this being made available by regenerative energy sources. Due to its chemical composition, however, OME exhibits instability with regard to acid-catalyzed depolymerization. It should be mentioned that due to the given equilibrium reaction and an associated incomplete

Polymerization always contains small amounts of formaldehyde - a monomer component of the OME - which cannot be removed from the OME with economically reasonable effort. This formaldehyde can with z. B. during a refueling process and via storage and / or tank walls penetrated into the OME react oxygen to formic acid. The resulting formic acid dissociates into the OME in the presence of

entrained water in acid residues of formic acid and oxonium ions, which are also known as hydronium ions. These act as an acid catalyst and initiate depolymerization of the OME. The formaldehyde, which is now present in larger amounts due to the depolymerization, can in turn polymerize to polyformaldehyde, which, by flocculation and accumulation, can lead to a reduction in line cross-sections and / or to the closure of the lines and / or nozzles and bearings.

In the adjacent area there are already systems to prevent leakage from

Fuel vapors are known, such as in DE 10 2012 018 558 A1

Tank ventilation system is described. In order to prevent fuel vapors consisting of unburned hydrocarbons from escaping into the environment, this has an adsorption filter which is usually used for this purpose. To prevent water from entering and the associated corrosion of the adsorption filter or

Impairment of the adsorption material arranged in the adsorption filter is

Intake opening with the adsorption filter during its regeneration phases

Ambient air supply ventilation line arranged in the interior of the motor vehicle, so that it is essentially protected from external weather conditions.

The task pursued by DE 10 2012 018 558 A1 to prevent water from entering the adsorption filter and thus the impairment of the adsorption material in the course of ventilation of the adsorption filter during its regeneration phases is achieved by the adsorption filter shown in DE 10 2013 019 328 A1 solved in another configuration. For this purpose, the adsorption filter has a seal, which expands when it comes into contact with water and thereby closes a ventilation channel of the adsorption filter in such a way that the adsorption material arranged in a receiving space downstream of the channel of the seal does not come into contact with the water entering the ventilation channel on the inlet side can reach. However, both of the above publications describe ventilation systems which are not suitable for venting a tank.

DE 10 2014 010 728 A1, on the other hand, discloses a tank ventilation filter for connection to a fuel tank, which essentially consists of a constriction, downstream of the constriction of air drawn in in the direction of flow

Sedimentation chamber and a particle filter consisting of a fiber material is constructed. Here the constriction and the sedimentation chamber are

Separation of water entering the filter with the sucked-in air is provided, which primarily serves to protect the particle filter against moisture and only secondarily to protect the tank contents from penetrating water. The separation of the water also takes place unspecifically and not to a large extent, since the change in cross-section and therefore the pressure increase is not sufficient for pressure change separation, which means that the tank ventilation filter is only suitable for condensing moisture, such as during rain events.

Against this background, the invention has for its object to design the fuel system of the type mentioned in such a way that water or

Water vapor in the fuel is avoided.

This object is achieved with a fuel system according to the characteristics of the

Claim 1. The subclaims relate to particularly expedient developments of the invention.

According to the invention, a fuel system is therefore provided, in particular for storing and supplying fuel to an internal combustion engine of a motor vehicle, which has a fuel tank and a main flow branch through which a fluid mixture can flow and which opens into the fuel tank, the main flow branch in particular being designed to be exclusively through-flowable. A separating device for a fluid containing the fluid mixture is also arranged in the main flow branch. In this case, this fluid is a reaction fluid which chemically reacts with the fuel, parts and / or constituents of the fuel, the chemical reaction of the fuel, parts and / or constituents of the fuel also being able to take place in a chemical chain reaction. For separating and receiving this chemically with the fuel, parts and / or

The separating device has constituents of the reaction fluid that reacts with fuel Storage element, whereby the supply, penetration or introduction of the reaction fluid to or into the fuel can be completely or almost completely eliminated. In order to fulfill the function intended for the separating device, it is arranged upstream of the fuel tank in the main flow branch or, starting from the supply of the fluid mixture and an associated flow in the direction of the fuel tank, upstream of the fuel tank. The separating device arranged in the main flow branch also forms a component of the main flow branch. It is conceivable here that the main flow branch has further components arranged in the main flow branch, at least some of the components of the

Main flow branch should be fluidly connected to one another via lines.

The fluid mixture consists of at least two fluids, one of which is the reaction fluid. In this case, a fluid is considered to be of a single type, as a result of which the fluid mixture could be made up of an atomically or molecularly present gas and the reaction fluid. In general, however, the fluid mixture consists of more than two fluids, the fluid mixture usually being air present in the atmosphere surrounding the fuel system. The fluid that forms the reaction fluid is regularly water in the air in liquid and / or gaseous phase, the water in the gaseous phase accordingly being present as water vapor. If the fluid mixture is configured as air in such a constellation, the supply of the fluid mixture is the ventilation of the fuel tank with air, which the water or the water vapor by means of the

Separation device was withdrawn.

In an extremely advantageous development of the invention, the storage element is a

Adsorber or absorber, but in a preferred embodiment the storage element is designed as an adsorber. Such an embodiment of the storage element as an absorber or preferably an adsorber enables complete or almost complete separation and absorption of the reaction fluid in the adsorber or absorber. In this context, the adsorber should contain an adsorbent or also an adsorbent, which preferably has a porous or highly porous structure and / or the reaction fluid with high selectivity, e.g. B. in the form of water and / or water vapor, but none or almost none

Hydrocarbons or fuel binds.

In a further profitable embodiment of the invention, there is no supply of the reaction fluid via a filler device which enables a supply of fuel through a fuel line connected to the fuel tank to the fuel tank containing fluid mixture. The filling device is generally a tank neck arranged on a motor vehicle for the purpose of the refueling process. The fact that no fluid mixture containing the reaction fluid is supplied via the filler device, for example in the form of the filler neck, can ensure that the fluid mixture is supplied to the fuel tank exclusively via the separating device and thus prevents the reaction fluid from penetrating into the fuel. If the fluid mixture is designed as ambient air, the ventilation of the

Fuel tanks only via the separator, ventilation via the filler, z. B. in the form of the tank neck is excluded.

It also proves to be extremely advantageous if, in a further development of the invention, the fuel system supplies and supplies fuel to and from one

Comprises internal combustion engine supply and return and a separator for separating the reaction fluid present in the fuel is arranged in the flow or return. This separator, which is preferably arranged in the return, is particularly important when parts of the fuel are renewable

Biofuel obtained from raw materials. This applies in particular to so-called biodiesel, which has a hygroscopic effect. To separate the water contained in the fuel, fuel filters are usually integrated into the fuel filter

Water separator used. However, it cannot be ruled out that water or water vapor will be entrained from these and be present again in the fuel. To avoid a reaction with the fuel, parts and / or components of the fuel contained in the fuel tank, it is considered profitable to separate the reaction fluid, which is present, for example, in the form of water or water vapor, from the fuel returned to the fuel tank. Likewise, the separation device can be provided to separate reaction products which have already been converted from the fuel to be recycled.

If the fuel system is also designed in such a way that it has at least two separating devices, which can be flowed through in particular in the main flow branch, z. B. always in the event of a defect or malfunction of a separation device or in the case of regeneration of a separation device, separation and absorption of the reaction fluid from the fluid mixture can be ensured. It should be noted here that preferably only two separating devices in the fuel system and these particularly preferably in the main flow branch parallel to one another

are arranged to flow through. However, it is also conceivable that there are two main flow branches with a separating device arranged in the respective main flow branch. Furthermore, an embodiment of the invention is to be regarded as advantageous, in which the storage element is exchangeably arranged in the separating device, whereby an exchange of the storage element is made possible, for example, in the event of a defect or a malfunction, but especially if the storage element is saturated with the reaction fluid. The storage element can be used to ensure exchangeability

Exchangeable cartridge, the separating device can thus be designed as an interchangeable cartridge system.

In the embodiment of the invention with at least two separating devices and the exchangeable arrangement of the storage element in each of the separating devices, there would also be the possibility of saturating one of the storage elements

To replace the storage element of the first separation device, wherein a separation and absorption of the reaction fluid from the fluid mixture by the storage element of the second separation device would still be guaranteed.

An embodiment of the invention is also very promising

characterized when the separating device has a regeneration device for releasing the reaction fluid received in the storage element, wherein a possible embodiment of the regeneration device can be a heating device expelling the reaction fluid from the storage element. When regenerating the storage element by means of the regeneration device, it should be noted that the release of the reaction fluid takes place opposite the fuel tank, into the atmosphere surrounding the fuel system, so that a supply of the reaction fluid to the fuel is avoided.

If the fuel system also has at least one fuel vapor retention system arranged in the main flow branch - in particular through which the separating device or the separating devices can flow, or alternatively the separating device has a separating element that stores fuel vapors, then this can be seen as a very promising embodiment of the invention, in addition to the supply of

Reaction fluid in the fuel prevents fuel vapors from escaping from the fuel tank. The fuel vapor retention system, if arranged in the main flow branch, would also be regarded as a component of the main flow branch. In a further extremely advantageous development of the invention, in

Main flow branch, here starting from the supply of the fluid mixture and a flow associated therewith in the direction of the fuel tank, in particular upstream or downstream of the separating device, a conveying device for the fluid mixture

arranged, the conveyor also being a component of the

Main flow branch forms. The conveyor can in the simplest case

For example, be designed as a fan, which, starting from the supply of the fluid mixture and a flow associated therewith, is arranged upstream of the separating device in the direction of the fuel tank.

Is an embodiment of the invention characterized in that in

Main flow branch between the separator and the fuel tank at least one influencing the flow of the fluid mixture - and a component of the

Main flow branch-forming valve is arranged, by blocking the flow by means of the valve, for example, during a regeneration or an exchange of the storage element, a supply of the fluid mixture with reaction fluid contained in the fluid mixture, for example in the form of ventilation of the fuel tank with air containing water vapor, can be profitably avoided ,

Is further - the invention further - one to influence the flow of the fluid mixture in the main flow branch between the separator and the

Fuel tank arranged armature over a forming a secondary flow branch

Ventilation line connected to the fuel line and / or the filling device, it is possible that a supply of the fluid mixture containing the reaction fluid during a filling process of the fuel by means of a through the ventilation line and generating a counterflow in the fuel line and / or the filling device

Fluid mixture is prevented, the counter-flowing fluid mixture contains no reaction fluid.

In this context, the fitting or fittings can be designed as a valve, possibly also in the form of a check valve, as a multi-way valve such as a 3/2 or 3/3-way valve or as a simple blocking slide. In the case of the design as a reusable valve, the arrangement of more than one fitting could advantageously be dispensed with, since the flow of the

Fluid mixtures can be influenced in more than one way. It is conceivable that the valve is designed as a 3/3-way valve, with a connection to the separating device second connection is connected to the ventilation line and a third connection to the fuel tank. The supply of the fluid mixture to the

Fuel tank or to the ventilation line as well as blocking the flow.

When one, two or even more fittings and a conveying device are arranged between the separating device and the fuel tank, the conveying device is in the direction facing away from the fuel tank before or starting from the supply of the fluid mixture and an associated flow in the direction of the fuel tank upstream of the fitting or the fittings in the main flow branch. Again starting from the supply of the fluid mixture and a flow connected thereto in the direction of the fuel tank, the delivery device can be arranged downstream of the separating device, but preferably upstream of the separating device in the main flow branch.

It should also be mentioned that at least two of the components mentioned in the preceding sections, such as the separating device, the fitting or the fittings, the

Fuel vapor retention system and the conveyor device of the main flow branch, which are arranged in this, in one of the at least two or all

Component comprising unit, in particular in a compact unit, can be executed.

In a particularly practical manner, the fuel is at least partially an alternative fuel and / or the fuel designed as an alternative fuel can be decomposed by acid-catalyzed hydrolysis. The alternative fuel can in particular be an ether such as

Polyoxymethylene dimethyl ether, also oxymethylene ether (OME), and / or esters such as

Carbonic acid dimethyl ester, also dimethyl carbonate or methyl formate, also methyl formate.

The invention permits numerous embodiments. To further clarify its basic principle, one of these is shown in the drawing and is described below. This shows in

Fig. 1 is a schematic representation of the fuel system.

FIG. 1 shows a schematic illustration of a fuel system 1 according to the invention for storing and supplying fuel to the internal combustion engine 8. Here, the fuel system 1 has the fuel tank 2 and a fluid mixture through which and can flow main flow branch 3 opening into the fuel tank 2, it being assumed that the fluid mixture is in the form of air surrounding the fuel system 1. In addition, the separating device 4 for a fluid containing the fluid mixture is arranged in the main flow branch 3. The fluid is a reaction fluid which chemically reacts with the fuel, parts or components of the fuel stored in the fuel tank 2, this reaction fluid being present in the form of water vapor contained in the fluid mixture in the form of air. In addition, the separator 4 has a

Water vapor from the air separating and receiving storage element 5, which is designed as an adsorber for the water vapor. The fuel system 1 is designed such that the fluid mixture is supplied to the fuel tank 2, that is to say, the fuel tank 2 is vented with air from the atmosphere surrounding the fuel system 1 exclusively via the main flow branch 3 and thus via the separating device 4. This is also achieved in that in the main flow branch 3 between the

Separation device 4 and the fuel tank 2, the armature 14 influencing the flow of the fluid mixture in the form of air and shaped as a reusable valve, and furthermore the armature 14 shaped as a reusable valve via one

Aeration line 15 forming secondary flow branch is connected to the filling device 7. In the case of a filling process of the fuel via the filling device 7 designed as a tank neck, insofar as the fuel tank 2 is refueled, the delivery device 13, which is also arranged in the main flow branch 3 in front of the separating device 4, and a switching position of the fitting 14 designed as a returnable valve, which is a

Flow of the fluid mixture present as air via the separating device 4, the reusable valve and the ventilation line 15 to the filling device 7 enables one

Counterflow of water vapor-free air is generated in the filling device 7, so that no reaction fluid, ie water vapor-containing fluid mixture or air, enters the fuel via the fuel line 6. A second switching position, here a blocking division, of the valve 14 designed as a reusable valve also enables the storage element 5 to be regenerated with the regeneration device 12 of the separating device 4 designed as a heating device, without the expelled from the storage element 5

Reaction fluid in the form of water vapor enters the fuel tank 2 and is released into the atmosphere surrounding the fuel system 1. In normal operation, the reusable valve is in a switch position open in the direction of the fuel tank 2, so that the fuel tank 2 can be ventilated with steam-free air. The fuel system 1 now also has the flow 9 to the internal combustion engine 8 and return 10 from the internal combustion engine 8, the transport of the fuel from the fuel tank 2 being initiated by the fuel delivery unit 16. In the lead 9, the fuel filter 17 and In the return 10, the separating device 11 for separating reaction fluid, water or water vapor, which may have been carried into the fuel, is arranged.

LIST OF REFERENCE NUMBERS

Fuel System

Fuel tank

Main flow branch separator storage element fuel line

Filling device internal combustion engine flow

Return separation device regeneration device conveyor device armature

Ventilation line fuel delivery unit fuel filter

Claims

claims

1. Fuel system (1) with a fuel tank (2) and one of a fluid mixture

Main flow branch (3) which can flow through and opens into the fuel tank (2), a separating device (4) for a fluid containing the fluid mixture being arranged in the main flow branch (3), characterized in that the fluid is mixed with a fluid in the fuel tank (2). stored fuel, parts or components of the fuel is chemically reactive reaction fluid and the separating device (4) is a

Has reaction fluid separating and receiving storage element (5) from the fluid mixture.

2. Fuel system (1) according to claim 1, characterized in that the

Storage element (5) is an adsorber or absorber.

3. Fuel system (1) according to claims 1 or 2, characterized in that via a supply of fuel through a connected to the fuel tank

Fuel line (6) to the fuel tank (2) enabling filling device (7) no supply of the fluid mixture containing the reaction fluid takes place.

4. Fuel system (1) according to at least one of the preceding claims, characterized

characterized in that the fuel system (1) enables supply and return of fuel to and from an internal combustion engine (8) flow (9) and

Return (10) and in the flow (9) or the return (10) one

Separating device (11) for separating reaction fluid present in the fuel is arranged.

5. Fuel system (1) according to at least one of the preceding claims, characterized

characterized in that the fuel system (1) has at least two separating devices (4) and / or the storage element (5) is exchangeably arranged in the separating device (4).

6. Fuel system (1) according to at least one of the preceding claims, characterized in that the separating device (4) has a regeneration device (12) for releasing the reaction fluid received in the storage element (5).

7. Fuel system (1) according to at least one of the preceding claims, characterized

characterized in that the fuel system (1) has at least one fuel vapor retention system arranged in the main flow branch (3) or the separating device (4) has a separating element that stores fuel vapors.

8. Fuel system (1) according to at least one of the preceding claims, characterized

characterized in that a conveying device (13) for the fluid mixture is arranged in the main flow branch (3).

9. Fuel system (1) according to at least one of the preceding claims, characterized

characterized in that in the main flow branch (3) between the separating device (4) and the fuel tank (2) at least one fitting (14) influencing the flow of the fluid mixture is arranged and / or one for influencing the

Flow of the fluid mixture in the main flow branch (3) between the

Separation device (4) and the fuel tank (2) arranged fitting (14) via a ventilation line (15) forming a branch of flow is connected to the fuel line (6) and / or the filling device (7).

10. Fuel system (1) according to at least one of the preceding claims, characterized

characterized in that the fuel is at least partially an alternative fuel and / or the fuel formed as an alternative fuel by acid-catalyzed

Hydrolysis is decomposable.