WO2009019109A1

WO2009019109A1 - Device for introducing fuel

Info

Publication number: WO2009019109A1
Application number: PCT/EP2008/059182
Authority: WO
Inventors: Andreas Genssle; Markus Gloeckle
Original assignee: Robert Bosch Gmbh
Priority date: 2007-08-07
Filing date: 2008-07-14
Publication date: 2009-02-12
Also published as: DE102007037218A1

Abstract

The invention relates to a device for introducing fuel into combustion chambers of an internal combustion engine, comprising a fuel tank (3) for storing fuel, and means for introducing the fuel into the combustion chambers of the internal combustion engine. An adsorber (7) is arranged between the fuel tank (3) and the means for introducing the fuel into the combustion chambers of the internal combustion engine, which adsorber (7) comprises at least one adsorbent and/or molecular sieve in which acidic components and/or water are removed from the fuel. The invention also relates to a method for removing acidic components and/or water from fuels for internal combustion engines, wherein biogenic fuels are admixed to the fuel and the fuel is stored in a fuel tank (3). Before being introduced into combustion chambers of the internal combustion engine, the fuel is conducted through an adsorber (7), wherein acidic components and/or water are removed from the fuel at the adsorber (7).

Description

July 31, 2007

description

title

Device for introducing fuel

State of the art

The invention relates to a device for introducing fuel into combustion chambers of an internal combustion engine according to the preamble of claim 1. Furthermore, the invention is based on a method for the removal of acidic components and / or water from fuels according to the preamble of claim 10.

With regard to an ever more important CO ₂ -saving, fossil fuels are blended with fuels of biological origin. Biofuels are referred to as "biogenic fuels." Biogenic fuels are mixed with both diesel fuel and gasoline.

Biogenic fuels that are added to diesel fuel are, for example, esters of long-chain, often unsaturated fatty acids, which are obtained by transesterification of various biogenic oils and fats. For example, diesel fuel with a share of 5% biogenic fuels is currently available on the market. A biogenic fuel in its pure form is also marketed under the name "biodiesel." A known representative of the biogenic fuels is, for example, rapeseed oil methyl ester.

Biogenic fuels that are added to gasolines are usually alcohols.

The disadvantage of biogenic fuels is that they are subject to aging or biodegradability or decomposition. As degradation products often arise organic acids that can cause corrosion of metallic materials. The corrosive effect of biogenic fuels or the acid degradation products on hydraulic components of injection systems, as these are commonly used today in internal combustion engines, must be prevented. In particular, fuel injectors are manufactured extremely precisely to meet the functional requirements. However, corrosion can cause small, unpredictable changes in the fuel quantity measurement. play occur at an injection nozzle. This has significant effects on both fuel consumption and pollutant emissions. In the worst case, corrosion can even lead to the failure of the entire injection system.

Generally, the chemical and biochemical degradation reactions of biogenic fuels are initiated by a reaction with atmospheric oxygen, an oxygenation. In particular, unsaturated organic compounds are susceptible to such reactions with atmospheric oxygen.

In addition to acid-induced corrosion, water dissolved in the fuel or water entrained in the fuel and recondensed again also has a very corrosive effect. Water can be introduced, for example, during refueling of the motor vehicle. At higher temperatures during operation of the vehicle, water z. B. in the fuel tank. This is because the solubility of water in the fuel increases with temperature. When parking the vehicle and cooling the fuel, the entrained water can condense in the injection system and unfold there its corrosive effect.

Due to their higher polarity compared to pure diesel fuel, biogenic fuels show an increased water absorption capacity. For this reason, the water-related corrosion is also further increased compared to pure diesel fuel.

In addition, reaction of the esters of the biogenic fuel with water by hydrolytic ester cleavage results in the formation of free carboxylic acids and short chain alcohols. The ester cleavage is in turn catalyzed by acids, so that in the presence of water, a self-catalyzing process takes place. During the degradation of the fuel, alcohols are released which are also susceptible to oxidative degradation, which can lead to the free acid.

Typical of the aging behavior of biogenic fuels is that after an induction period, the acidity of the fuel increases sharply. The duration of the induction time, during which no significant change in acidity is observed, is a measure of the oxidation stability of the fuel. The higher the admixture proportion of biogenic fuel in the fuel used, the shorter the induction phase. It can be observed that the induction phase decreases faster in relation to an increasing proportion of the biogenic fuel than the proportion of biogenic fuel increases. Disclosure of the invention

Advantages of the invention

An inventively designed device for introducing fuel into combustion chambers of an internal combustion engine comprises a fuel tank for storing fuel and means for introducing the fuel into the combustion chambers of the internal combustion engine. Between the fuel tank and the means for introducing the fuel into the combustion chambers of the internal combustion engine, an adsorber is arranged, which comprises at least one adsorbent and / or molecular sieve, are removed and bound in the acidic components and / or water from the fuel.

For the purposes of the present invention, fuel is understood to mean commercial or generally known fuels for internal combustion engines, which contain predominantly different boiling fractions of aliphatic and aromatic hydrocarbons and also other additives, so-called additives. Furthermore, it is also possible that the fuels are of biogenic origin. Further, the fuels may include other synthetically produced hydrocarbon compounds, so-called SynFoels, BTL or GTL propellants, e.g. produced by the Fischer-Tropsch synthesis. The term fuels also includes oxygen-containing hydrocarbons, e.g. alcoholic compounds, ethers, for example the ethylene glycol dimethyl ethers, esters, ketones, ketals, aldehydes, acetals and others. The aforementioned fuels may each be contained individually or in mixtures with a proportion of the individual types of fuel between 0 and 100% in the fuel.

By removing the acidic components and / or the water from the fuel by means of the adsorber, the corrosive effect of the fuel is reduced. This leads to an increase in the compatibility of the device for introducing fuel against a high proportion of biogenic fuels in the fuel used. In addition, the device according to the invention makes it possible to reduce the negative effects of incorrect refueling on the device. Misfueling is understood to mean the refueling of a non-certified, oxidation-unstable fuel and / or refueling with a fuel containing more water.

With the aid of the adsorbent and / or the molecular sieve, acid components dissolved in the fuel and water are retained and bound before the fuel is conveyed to the means for introduction into the combustion chambers of the internal combustion engine. The means for introducing the fuel into the combustion chambers of the internal combustion engine For example, injection systems are used in modern combustion engines. These generally include, for example, electromechanically actuated fuel injectors, with which the fuel is injected into the individual combustion chambers.

In a preferred embodiment, the adsorbent comprises a basic Adsorbermate- rial. The acidic components or the water are adsorbed on the basic adsorber material. Alternatively, the separation of the acidic components or of the water takes place by molecular filtration with the aid of the molecular sieve.

In a preferred embodiment, the adsorbent comprises a structurally voluminous, basic adsorber material. This will result in an ester cleavage, if any, occurring on the basic adsorber material, that is, undesired fuel cleavage, e.g. suppressed by transesterification. In addition, there is also a limitation of the ester cleavage by the voluminous, long-chain residues of the constituents of the biogenic fuel.

Preferably, the adsorbent comprises at least one sterically hindered base. These can not react with the ester due to their spatially spreading molecular structure. However, they can deprotonate the acidic decomposition products of the biogenic fuels and / or water. This also works if the decomposition products have a molecular size comparable to the ester. The steric hindrance can be realized in particular in that the sterically hindered base is part of a polymeric, structurally voluminous carrier material. As carriers, e.g. crosslinked polystyrene or its derivatives, such as divinylbenzene can be used. Such carriers are insoluble in organic media.

Particularly suitable basic compounds as adsorbent are polymeric compounds. Most suitable are basic resins which may be neutral or ionic. Ionic resins are also referred to as basic ion exchangers. These are commercially available in different base strengths. The ion exchangers can be present either as a solid or as a viscous liquid.

In general, ion exchangers comprise a crosslinked resin matrix in gel structure with incorporated fixed ions and usually moveably bound counterions. The counterions can be exchanged for other counterions of the same polarity.

If weakly acidic, inorganic materials are used as a molecular sieve, these can be basified, for example, with strong bases. Modify in this way These then also act as strongly basic adsorber and are advantageous in the context of the invention.

Furthermore, surface-based metal oxides, for example basic alumina, can also be used as the adsorber.

For the purposes of the present invention, particularly suitable as adsorbent and / or molecular sieve are all organic or inorganic materials which have basic surfaces or centers and thereby firmly bind acidic components.

If a molecular sieve is used for separating off the biogenic decomposition products, that is to say the acidic components, and / or the water, inorganic ion exchange materials are generally used for this purpose. Such inorganic ion exchanger materials are, for example, zeolites, silicates or clay minerals. Frequently the molecular sieves are cation exchangers. However, this is not required according to the invention. In particular, when using a cation exchanger as molecular sieve, it must be ensured that all acidic centers of the cation exchanger are exchanged for non-acidic cations. If this is not the case, the remaining acidity of the adsorbent material could favor the degradation of the biogenic fuel by acid catalysis.

When using basic adsorber materials, care should be taken that the reaction of an ester with a strong, mobile base leads to cleavage of the ester. For example, in the classic ester saponification, caustic soda is reacted with an ester and irreversibly converted to the sodium salt of the acid and a free alcohol. However, the ester cleavage may also occur, for example, by means of the water contained in the fuel in the presence of a basic material. This too leads to an irreversible cleavage of the ester constituents of the biogenic fuel. However, since only relatively small amounts of water are generally contained in the fuel and the ester cleavage with a strong base is an irreversible reaction, the water is efficiently from the fuel under BiI- düng a weakly basic carboxylate, which is firmly bound to the adsorber away. This makes it possible to use the irreversible cleavage of the ester constituents by water contained in the fuel to protect against corrosion.

In order to avoid the occurrence of corrosion in the entire device for introducing fuel into the combustion chambers of the internal combustion engine, the adsorber is preferably arranged between the fuel tank and a pump, with which the fuel is conveyed to the combustion chambers and compressed. The adsorber can in this case be arranged, for example, between the fuel tank and a fuel filter or itself connect to the fuel filter. In a preferred embodiment, the adsorber is part of the fuel filter. For this purpose, the adsorbent and / or the molecular sieve is contained in the fuel filter. In general, a fuel filter comprises an annular filter substrate through which the fuel flows. In general, screw-on filters are used with star-folded or wound filter substrate. Increasingly, fuel filters are used with aluminum / plastic and all-plastic housing. As a replacement part remains only a metal-free filter insert. In the interior, a support tube is generally accommodated, which is enclosed by the filter substrate. The fuel, after passing through the filter substrate, flows back through the support tube. In a particularly preferred embodiment, the adsorbent and / or the molecular sieve is contained in the support tube. Alternatively, however, it is also possible to arrange the adsorbent and / or the molecular sieve in the filter substrate. In a further alternative embodiment, the adsorbent and / or the molecular sieve is used as filter material of the fuel filter. In this case, the filter substrate is made of the adsorbent and / or the molecular sieve.

In a preferred embodiment, the freed of acidic components and / or water fuel is completely or at least partially returned to the fuel tank. This protects the entire contents of the fuel tank from autocatalytic decomposition of the fuel. Also, the content of free acids and / or water in the fuel is kept to a minimum.

When used in self-igniting internal combustion engines common rail systems, that is, injection systems that operate with a high-pressure accumulator, the fuel is passed on the way from the fuel tank in the high-pressure accumulator through the adsorber and freed in this of acid and / or water. On the high pressure side of the injection module acid and / or water-free fuel is supplied in this way. As a result, the individual components of the common rail system are efficiently protected against corrosion. Through the fuel return of the common rail system, the freed of acid and / or water fuel flows back into the fuel tank.

Brief description of the drawings

Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description.

Show it FIG. 1 shows a schematic representation of a high-pressure accumulator injection system,

Figure 2 is a three-dimensional sectional view of a fuel filter.

Embodiments of the invention

1 shows a schematic representation of a high-pressure accumulator injection system (common rail injection system) is shown, in which a possible position of the adsorbent material is shown.

A high-pressure accumulator injection system 1 comprises a fuel tank 3 in which fuel is stored. A fuel line 5 opens out of the fuel tank 3. According to the invention, an adsorber 7 adjoins the fuel tank 3 in the fuel line 5. The adsorber 7 contains an adsorbent and / or a molecular sieve with which acidic components and / or water are removed from the fuel. As already described above, the adsorbent preferably comprises a sterically hindered base.

If strongly basic anion exchangers are used, they have as functional fixed bed ions, for example, quaternary ammonium compounds which are embedded in a crosslinked resin matrix in gel structure. For example, cross-linked polystyrene is used as the matrix. Particularly suitable as a matrix is crosslinked divinylbenzene. The anion of the ion exchanger used according to the invention is RO. Herein, R represents an organic, structurally bulky residue, e.g. a tertiary butyl or the polymeric support structure per se, preferably the polymeric support structure per se.

The fixed bed of this anion exchanger acts as a sterically hindered base capable of neutralizing acidic constituents of the decomposition products present in the fuel in an acid-base reaction and of binding them firmly in the adsorbent material with salt formation.

It is particularly preferred if both ionic species are immobile. In this case, both ion types are polyionic. This results in all reactants being firmly bound in the adsorber.

Characterized in that the acidic components and / or the water are removed from the fuel in the adsorber 7, the subsequent parts of the high-pressure storage injection system 1 are effectively protected against corrosion. The adsorber 7 is followed by a fuel filter 9. In the fuel filter 9, solid components and impurities are removed from the fuel. Moreover, in general, in the fuel filter 9, especially when used in auto-ignition internal combustion engines, water contained in diesel fuel is largely precipitated. Since water is heavier than the diesel fuel, this accumulates in a water storage space of the fuel filter. 9

The fuel filter 9 is generally followed by a prefeed pump 11. This is followed by a high pressure pump 13, with which the fuel is compressed to the accumulator pressure. In high-pressure accumulator injection systems, as used in auto-ignition internal combustion engines, the accumulator pressure to which the fuel is compressed by the high-pressure delivery pump 13 is generally in the range of e.g. 1600 to 2000 bar. By means of a pressure regulating valve 15, the pressure is kept constant. The fuel compressed to system pressure is then conveyed into a high-pressure accumulator 17. So that the fuel contained in the high-pressure accumulator 17 has system pressure during the entire operating time of the internal combustion engine, a pressure sensor 19 is arranged on the high-pressure accumulator 17. The pressure sensor 19 is connected to an electronic control unit 21. With the electronic control unit 21 and the high-pressure pump 13 is still connected. Depending on the measured pressure, the high-pressure pump 13 is controlled by the electronic control unit 21.

High-pressure lines 23 fuel injectors 25 are connected to the high-pressure accumulator 17. The fuel injectors 25 are supplied with fuel via the high-pressure lines 23. The fuel is then injected via the fuel injectors 25 into combustion chambers, not shown here, of an internal combustion engine. The sequence of injection is also controlled by the electronic control unit 21. For this purpose, the fuel injectors 25 are connected to the control unit 21. In general, the fuel injectors 25 operate hydraulically, and for switching the valves, the fuel under system pressure is used in conjunction with an electrical drive. Not injected into the combustion chambers of the internal combustion engine fuel is fed back via a fuel return line 27 into the fuel tank 3. Since in the adsorber 7 acidic components and / or water has been removed from the fuel, substantially acid-free and anhydrous fuel is transported into the fuel tank 3 via the fuel return line 27.

In addition to the embodiment shown in Figure 1, in which the adsorber 7 is placed between the fuel tank 3 and the fuel filter 9 in the fuel line 5, it is also possible to place the adsorber 7 between the fuel filter 9 and the prefeed pump 11. A placement of the adsorber 7 in front of the prefeed pump 11 is preferred so that corrosion-promoting constituents are removed from the fuel before they enter the prefeed pump 11. In this way it is also avoided that the pre-feed pump 11 corroded.

Alternatively, it is also possible that the adsorber 7 is part of the fuel filter 9.

FIG. 2 shows a three-dimensional sectional view of a fuel filter.

A fuel filter 9, as used in self-igniting internal combustion engines, comprises a filter substrate 31, which is traversed by the fuel and are separated in the impurities from the fuel. The flow of the fuel is shown by an arrow 33. At the top of the fuel filter 9 are inlet openings 35 through which the fuel enters the filter. The inlet openings 35 are formed in a filter cover 37. Between the filter cover 37 and the filter substrate 31 there is a space 39 through which the fuel is distributed into the filter substrate 31. The filter substrate 31 contains e.g. Multi-layer filter media that filters out impurities contained in the fuel.

The filter substrate 31 encloses a support tube 41, through which the filtered fuel flows to an outlet opening 43. In the embodiment shown here, the outlet opening 43 is located centrally within the inlet region in which the inlet openings 35 are formed. Thus, no unfiltered fuel can flow to the outlet opening 43, this is sealed against the inlet region by a sealing element 45. Another sealing element 47 seals the inlet region of the fuel filter 9 against the environment.

The filter substrate 31 is enclosed by a filter housing 49. Usually, the filter cover 37 is connected by means of a double flanging 51 with the filter housing 49.

As a result, a liquid-tight connection is achieved. Below the filter substrate 31 is a water storage space 53. Since free water is heavier than diesel fuel, this sinks and collects in the water storage space 53. The diesel fuel is in the

Water storage space 53 is deflected and flows out of the filter substrate 31 via the support tube 41 back up to the outlet opening 43. To the separated in the fuel filter 9

To remove water from the water storage space 53, this is provided with a water drainage screw 55 and a drain tube 57. According to the invention, the adsorber 7 is arranged in a preferred embodiment in the support tube 41 of the fuel filter 9. The already filtered fuel flows through the adsorber 7. Optionally, in the fuel contained (dissolved) water that was not removed in the fuel filter 9 and collects in the water storage chamber 53 and acidic components of the fuel are removed in the adsorber 7. Alternatively to the embodiment shown here, in which the adsorber 7 is placed in the support tube 41, it is also possible to position the adsorber 7 in the space surrounding the support tube 41. In this case, it is possible, on the one hand, for the adsorber to be positioned, for example, in the space 39 or to connect to the filter substrate 31 in the form of a circular ring. Furthermore, it is also possible for the filter substrate 31 itself to be designed as an adsorber and / or molecular sieve for removing water and acidic components.

In order to remove the acidic components and / or the water from the fuel, it is necessary in each case for the fuel to have a sufficient contact time with the adsorber or the molecular sieve.

Suitable adsorbents are, for example, weakly basic, neutral adsorbers, strongly basic, polycationic and polyanionic adsorbers and surface-based metal oxides.

For a weakly basic, neutral adsorber, the following applies:

[(RiR ₂ R ₃ ) N] + HR ₅ <-> [(RiR ₂ R ₃ ) NH ⁺ + R ₅ ] (I)

In Equation I, the solid adsorber material or the adsorbate formed therefrom and held in square brackets. R 1 to R _{3 are} in particular organic, long-chain radicals or the polymeric support structure of the weakly basic, neutral adsorber. R _{5 represents} the remainder of an acidic component. In general, this is an organic radical. R ₅ is for example OOCR ₇ . In this case, the acidic component is a carboxylic acid and R ₇ is an organic radical as contained in biogenic fuels. The organic radical R ₇ can be both long-chain and short-chain.

For a strongly basic, polycationic or polyanionic adsorber, the following applies:

[(RiR ₂ R ₃ R ₄ ) N ⁺ + OR ₆ ] + HR ₅ -> [(RiR ₂ R ₃ R ₄ ) N ⁺ + R ₅ + HOR ₆ ] (II)

Here too, the solid adsorber material or the adsorbate formed therefrom and held in square brackets. Ri to R ₄ mean organic, long-chain radicals or the polymeric support structure of the adsorbent material. R ₅ means, as above, the organic residue of an acidic component. R ₅ is an organic or inorganic, polymeric and thus insoluble in the fuel, strongly basic radical. Preferably, for example, is a sterically bulky polyalkyl alcoholate ORβ.

For a surface-based metal oxide, for example an aluminum oxide, the following applies:

[OAlO + Na ⁺ ] + HR ₅ -> [OAl (OH) + Na ⁺ + R ₅ ] (III)

In equation (III), R ₅ as above also means the organic residue of an acidic component.

Furthermore, for the purposes of the present invention, an inorganic or metal oxide carrier material may also be surface-modified with a preferably sterically hindered base. The sterically hindered base may be inorganic or organic, preferably organic.

The amount of adsorber material needed to remove acidic components and / or water can be estimated by a simple design calculation. The amount depends on the period of time after which the adsorber is to be changed.

For example, the target is a service interval of 20000 km. An on-market self-igniting internal combustion engine with four cylinders with a capacity of about 2 1 results in an average diesel fuel consumption of about 7 1 per 100 km. In the future, this will contain about 10% by volume of biogenic fuel. For the estimation, it is further assumed that the fuel contains 10 ppm of free acid from the oxidative decomposition of the biogenic fuel. This is represented, for example, by the oleic acid CnH ₃₃ COOH.

In order to realize the service interval of 20000 km, the capacity of the adsorber material at the consumption of 7 1 per 100 km must suffice for 1400 1 diesel fuel. With a proportion of 10% by volume of biogenic fuel, diesel contains 140 l of the biogenic fuel. This has a density of about 0.9 kg / 1 (for rapeseed oil methyl ester at 20 ⁰ C). At a mass fraction of 10 ppm, this therefore contains 140 1 * 0.9 kg / 1 * 10 ppm = 1.26 g of corrosive decomposition products. This results in the assumed oleic acid to be neutralized amount of 1.26 g per 220 g / mol = 0.0044 mol = 4.4 mmol. For the further exemplary design, 5 mmol of acid equivalent are assumed.

With a technically feasible total capacity of the anion exchanger for the loading of about 1.5 eq / 1 bed and an actual technically usable capacity of about 60%, that is about 1 val / 1 bed volume, one obtains a required volume of the anion exchanger of 5 mmol / 1 val / 1 = 5 ml.

The amount of adsorbent material can be designed for a full service interval duration, or even beyond, for a corresponding adsorber capacity. When using an adsorber material produced in this way results in a small installation volume due to the small amount required.

Claims

claims

1. A device for introducing fuel into combustion chambers of an internal combustion engine, comprising a fuel tank (3) for storing fuel and means for introducing the fuel into the combustion chambers of the internal combustion engine, characterized in that between the fuel tank (3) and the means for introducing the Fuel is arranged in the combustion chambers of the internal combustion engine, an adsorber (7) comprising at least one adsorbent and / or molecular sieve, are removed in the acidic components and / or water from the fuel.

2. Device according to claim 1, characterized in that the adsorbent comprises a basic adsorber material.

3. A device according to claim 1 or 2, characterized in that the adsorbent comprises a structurally voluminous, basic adsorber material.

4. Device according to one of claims 1 to 3, characterized in that the adsorbent comprises a sterically hindered base.

5. The device according to claim 4, characterized in that the sterically hindered base is part of a polymeric, structurally voluminous carrier material.

6. Device according to one of claims 1 to 5, characterized in that the adsorbent and / or the molecular sieve are present as ion exchangers.

7. Device according to one of claims 1 to 6, characterized in that further comprises a fuel filter (9) is included, wherein the adsorber (7) and the fuel filter (9) are two separate components.

8. Device according to one of claims 1 to 6, characterized in that further comprises a fuel filter (9) is comprised, wherein the adsorbent and / or the molecular sieve in the fuel filter (9) are arranged.

9. Device according to claim 8, characterized in that the adsorbent and / or the molecular sieve are used as filter material of the fuel filter (9).

10. The device according to claim 8, characterized in that the adsorbent and / or the molecular sieve in addition to a filter substrate (31) in the fuel filter (9) are included.

11. A method for removing acidic components and / or water from fuels for internal combustion engines, wherein the fuel biogenic fuels are admixed and the fuel in a fuel tank (3) is stored, characterized in that the fuel prior to introduction into combustion chambers of the internal combustion engine by a Adsorber (7) is passed, wherein in the adsorber (7) acidic components and / or water are retained from the fuel.

12. The method according to claim 12, characterized in that the fuel passed through the adsorber (7) is at least partially returned to the fuel tank (3).

13. The method according to claim 11 or 12, characterized in that water is removed from the fuel to form a weakly basic carboxylate which is firmly bound to the adsorbent.