WO2012069338A1

WO2012069338A1 - Fuel filter

Info

Publication number: WO2012069338A1
Application number: PCT/EP2011/070144
Authority: WO
Inventors: Martin Klein; Jochen Reyinger; Martin Veit; Stefan Eichinger
Original assignee: Mann+Hummel Gmbh
Priority date: 2010-11-25
Filing date: 2011-11-15
Publication date: 2012-05-31
Also published as: DE112011103920A5; DE102010052329A1

Abstract

The invention relates to a fuel filter (1) for filtering fuel, in particular diesel fuel, comprising: a filter element (2) for filtering particles out of the fuel, a coalescing element (3) for coalescing water present in the fuel, and a housing, in particular a cup-shaped housing (4), having an inner space (5), wherein in a base region (6) of the inner space (5) through which the fuel flows a water-collecting chamber (7) for collecting water separated from the fuel is formed, and wherein means (8) for binding the separated water are provided in the base region (6). The degree of separation of water from the fuel can be improved especially easily by means of the fuel filter (1) according to the invention.

Description

Fuel filter

Technical area

The invention relates to a fuel filter for filtering fuel, especially diesel fuel.

In the filtering of fuel, unfiltered (raw) fuel, e.g. Diesel fuel, taken from a fuel storage tank and freed of solid particles in the fuel filter, among other things. Subsequently, the filtered (pure) fuel is supplied to a heat engine for combustion.

Unfiltered fuel typically contains various types of contaminants, e.g. Rust particles that have formed by moisture in a fuel tank. If these substances are not removed before the fuel enters the engine, premature wear and defects, for example in the fuel pump and the injection system at the high pressures used there are the result.

However, the filtering of fuels is not limited to the filtering of impurities. It is also desirable from a technical point of view to separate the water contained in the fuel, especially in diesel fuel, in order to maintain its lubricity. The fact that water is heavier than the fuels typically used, gravity separation can take place, in which the water gravitationally accumulated in designated Wasserammeiräumen melt, whereby the lighter fuel floats on the water and thus can be separated from the water.

State of the art

From WO 2008/077954 A2 is a fuel! Iter, in which the water collecting space is formed in a container which is arranged below a Siebgewebeelements, which serves as a hydrophobic barrier layer at which the water in the fuel connects to water droplets, which fall by gravity down. During operation of the fuel filter, therefore, increasingly deposited water accumulates in the region of the bottom of the container. If the water reaches a certain water level, the water is discharged via a blower into a separate collecting space. The catchment space is located below the container and structurally separated from the container by a wall, i. the outlet communicates with the Wasserammei raum only via a check valve. In the collecting space, a bed of absorbent solids can be provided, which absorbs the water in the manner of a sponge. The absorbed water preferably evaporates by supplying air or heat, while leaving debris such as hydrocarbons in the bed.

From DE 10 2007 039 679 it is known to use so-called coalescence filters as means of water separation, in which a typically hydrophilic filter material layer contains water from the Fuel transformed by adhesion to larger drops of water. In DE 10 2007 039 679, the coalescing filter is arranged between two particle filters made of hydrophobic material, but it is also possible to carry out the particle filtration and the transformation of larger drops of water on one and the same element.

Increasing environmental awareness has led in recent years to an increased use of biofuels. However, biofuels, especially biodiesel, have an increased propensity to form stable water-fuel emulsions compared to conventional fuels, imposing increased demands on the separation of water from biofuels. But also in the filtration of conventional fuels, the separation of water has become the focus of development.

The invention is therefore based on the object, the deposition of

To improve water from a fuel.

Disclosure of the invention

This object is achieved by a fuel filter of the type mentioned, comprising: a filter element for filtering particles from the fuel, a coalescing element for coalescing befindlichem in the fuel water, and a particular pot-shaped housing with an interior, said in a ground area of the fuel flowed through the interior of a water collecting chamber for collecting is formed of water separated from the fuel, and wherein in the bottom region means for binding the separated water are provided.

By the means for binding the separated water can be achieved in a particularly simple manner that once separated water does not re-enters the fuel, so that an improvement of the separation efficiency of water can be obtained from the fuel. This is particularly beneficial for biofuels in which the already separated water has an increased tendency to re-mix with the fuel at the interface between water and fuel.

By the means for binding the water in the bottom portion of the interior, the water is held, which gravitationally gets into the bottom portion of the interior, i. E. the means for binding the water attracts or absorbs the water and stores it.

The storage of water in the Wasserammeiraum can be designed such that the means for binding the water, for example in the form of an absorbent solid or more absorbent solids, for example in the form of a bed, have a correspondingly high capacity, which makes it possible to store the entire accumulating in the course of operation of the fuel filter water. In this case, no replacement of the means for binding the water is required. In one embodiment, the separated water is absorbed or absorbed by the means for binding the separated water.

However, it is also possible to make the capacity of the means for binding the water less than 7U and to take measures to prevent the discharge of the bound water e.g. allow for an inspection, for example by the absorbent solid can be removed from the housing and pressed. If the bound water can not or only with great effort can be removed from the funds, the funds may also be exchanged for new, unused funds, which bind re-deposited water.

The fuel filter according to the invention also comprises, for filtering particles from the fuel, a filter element, which is typically connected upstream of the coalescing element in the flow direction of the fuel. The filter element divides the fuel filter into a raw-side and a clean-side region. The coalesced water collected in the water collection chamber is typically water secreted by gravitational force, the deposition being assisted by the coalescing element.

It is also possible that instead of the filter element and the coalescing element structurally separate therefrom, a common filter unit is provided which has both the fuel-filtering and the water coalescing properties. In other words: the particle Filtering and the transformation to larger drops of water can also be carried out on one and the same element.

In any case, an improvement of the degree of separation of water from the fuel to be filtered by a corresponding configuration of the filter unit or of the coalescing element to achieve: So kann z. by a coalescing element having a very high internal surface, i. With many very fine fibers and a very narrow fiber distribution, improved transformation from small to larger water droplets can be achieved.

In a preferred embodiment of the fuel filter, the means for binding the water comprise an absorbent solid. The absorbent solid may be provided in the form of a filling in the Wasserammeiraum. Fillings or possibly also beds of an absorbent solid can be adapted particularly easily to the shape of the water collection chamber and fill the room evenly. Thus, a particularly uniform binding of the water.

In a development of the preceding embodiment, the absorbent solid comprises hydrophilic fibers, which are preferably formed from defatted cellulose and / or surface-treated. Hydrophilic and / or surface-treated fibers exhibit a particularly pronounced binding action on water, so that such a filling in particular contributes to improving the degree of water separation of the fuel filter. wearing. An example of defatted cellulose is wound wadding. By surface-treated fibers, for example, hydrophilized fibers are understood.

In one embodiment, a fiber mixture is used which comprises at least 20% by weight of viscose fibers.

In an alternative embodiment, a water-absorbing granules (superabsorber) is used instead of or in addition to the hydrophilic fibers.

In a further embodiment of the fuel filter, the filter element for particle filtration is connected upstream of the coalescing element and formed as a pre-coalescing filter element. If the filter element already has precoalescing properties, then a transformation from small to larger water droplets already takes place in the filter element, as a result of which a higher degree of coalescence is achieved overall in the fuel filter, which in turn enables improved water separation. The Vorkoaleszieren can take place in the ultrafine medium of the filter element itself or by an additional downstream filter layer, such as. a thin, in particular hydrophilized nonwoven, which can be applied in particular to a particulate filter medium.

Also preferred is an embodiment of the fuel filter, which is characterized in that a water outlet device is connected upstream of a fuel outlet of the fuel filter. By the water retention device is achieved in an advantageous manner that not separated Water or water which has not been completely retained by the means for binding the water and threatens to escape via the fuel outlet is retained at the water retention device. The water retention device thus prevents or reduces the escape of water components or water droplets from the fuel filter according to the invention.

In a preferred embodiment of the previous embodiment, the water retention device is arranged in the region of an ittelrohrs associated with the fuel outlet, which supports the filter element and possibly also the coalescing element. Typically, a filter medium of the filter element (eg, a bellows or a wicking filter) is disposed about the center tube of the fuel filter with the center tube supporting the filter element and the cleaned fuel rising above the center tube and the fuel outlet formed at the top thereof is discharged from the fuel filter. At the other lower end of the central tube is typically the water collection room for separated water. In an embodiment of the fuel filter according to this development, the water retention device is therefore arranged in an advantageous manner on the separate water in the water collection chamber. In this way, the danger is that separated water is contrary to the weight from the water collection chamber through the central tube passes in the direction of fuel outlet, greatly reduced.

In a further likewise preferred development, the water retention device comprises a barrier layer, which consists of a hydrophobic material. Due to the hydrophobic material of the barrier layer, the Wasserrückhaiteeinrichtung is particularly effective. The barrier layer can consist, for example, of a sieve with a mesh size of less than or equal to 25 μm or of a fleece.

Another development is characterized in that the water retention device comprises a barrier in the central tube, wherein the barrier is formed as a stuffing ung and / or grid of hydrophobic material. Due to the barrier made of hydrophobic material, water that has entered the central tube and threatens to leak out of the fuel filter via the fuel outlet can still be caught and retained. On the other hand, the stuffing leaves the pure and freed of Waser fuel unhindered escape through the center tube.

Pure or water-repellent treated fibers or mesh of PTFE (polytetrafluoroethylene), PA (polyamide) or polyester are preferably provided as the hydrophobic material. Such fibers show a particularly high water repellency.

In a further preferred embodiment of the fuel filter, the coalescing element is a flow guide for the deposition followed by water by gravity. In the optimized flow guidance, for example, in a flow section of the fuel, the flow velocity and, if appropriate, a change in the direction of the flow are selected such that the water fractions which are heavier in comparison to the fuel are separated off. Alternatively, in the section of the flow guidance at correspondingly low flow velocities, only a gravitational separation of the water may occur.

In a further development of the previous embodiment, the flow guidance takes place through an annular gap. The annular gap, i. the available flow cross-section is larger in size compared to conventional annular gaps in fuel filters and supports the separation of water due to the effect of gravity, wherein the dimensioning of the flow guide and the flow velocity are coordinated so that for a given droplet size, the weight of the droplets is greater than the sum of buoyancy force and (speed-dependent) friction force.

Finally, in a likewise preferred embodiment, the coalescing element is followed by a water trap. The water trap prevents the coalesced water from escaping to the fuel filter. The water trap can do so as a circumferential, annular, vertical or in particular obliquely radially inward to the outflow direction be arranged out of the coalescing element and advantageously have radially circumferential grooves or ribs. Already separated or enlarged drops of water remain attached to the water trap, are enlarged by subsequent water and then fall by gravity into the water collection chamber.

Further features and advantages of the invention will become apparent from the following description of embodiments of the invention, with reference to the figures of the drawing, which show details essential to the invention, and from the claims. The individual features can be realized individually for themselves or for several in any combination in a variant of the invention.

Brief description of the drawings

Embodiments are illustrated in the schematic drawing and are explained in the following description. FIG. 1 shows a schematic cross section through a fuel filter according to the invention.

Embodiment of the invention

In the single figure, a fuel filter 1 is shown in a schematic sectional view. The flow path of the fuel through the fuel filter 1 is indicated by directional arrows.

The fuel filter 1 has a filter element 2 for filtering particles from the fuel, which comprises, for example, a star-shaped or wound filter medium. In addition, in the fuel! iter 1 a coalescing of the element 3 for coalescing water in the fuel. The fuel! Iter 1 further comprises a housing 4 with an inner space 5, wherein in a bottom portion 6 of the inner space 5, a Wasserammeiraum 7 is formed for collecting water separated from the fuel. In the bottom region 6 of the inner space 5 there is an absorbent solid in the form of a filling 8 made of hydrophilic fibers or another water-binding solid, by means of which separated water can be bound in the water collection chamber 7 or the bottom region 6.

For filtering fuel, it flows into the fuel filter 1 through a fuel inlet, not shown, and initially strikes the filter element 2 on the raw side. During the subsequent passage of the fuel through the filter element 2 from the radially outer side of the raw to the radially inner side clean smallest particles or particles are filtered out of the fuel (first stage). For this purpose, the filter element 2 has a very high filter fineness. By the elimination of dirt particles from the fuel to be cleaned all downstream stages of the fuel filter 1 are protected. The filter element 2 is designed as a pre-coalescing filter element 2, so that even before reaching the coalescing element 3, there is a transformation from small to larger water drops in the filter element 2. For this purpose, the filter medium of the filter element 2 itself (pre) coalescing Have properties, or it may optionally be a downstream additional filter stage, for example, be provided in the form of one or more thin, especially hydrophobic nonwoven layers.

On the clean side of the filter element 2, the liberated from dirt particles fuel enters an annular space 9 and flows down in the direction of the coalescing element 3. During the anschießenden flowing through the coalescing element 3 in the radial direction from the inside to the outside small connect in the Fuel (pre-coalesced) water drops to larger water retention (second stage).

Thereafter, the fuel flows together with the water droplets now become larger in a flow channel, not shown, wherein a standing in the flow path water trap 10 is flowed through, which prevents the water droplets are transported to the outlet of the fuel filter 1.

Following the water trap 10, the fuel flows through a flow guide 11 for the separation of water by gravity (third stage). In the case of this flow guide 11, the flow velocity and change in direction are selected in a flow section in such a way that the water droplets which are heavier in comparison to the fuel are deflected more strongly and can thus be deposited downwards into the water collection chamber 7. The flow guide 11 may be formed, for example, in the form of an annular gap whose outer boundary tion forms the housing 4 and whose diameter is chosen so that the gravity separation is favored.

Subsequently, the fuel enters the inner space 5 of the housing 4, wherein the water droplets or the water, which was deposited by the flow guide 1 1, in the bottom portion 6 of the interior 5 accumulates (fourth stage). The lighter fuel flows through the interior 5 above the bottom portion 6 and thus floats above the water. The fuel effectively forms a second phase above the water level. In the bottom region 6 of the interior 5 or in the water collection chamber 7, the hydrophilic fibers of the filling 8 bind the separated water, i. the water is absorbed by the hydrophilic fibers. It is understood that possibly the flow guide 1 can also be formed so that the fuel flows not only above the filling 8, but also the filling 8 is flowed through by the fuel and in this case the water is absorbed by the hydrophilic fibers.

On the way through the fuel filter 1, the fuel passes through a central tube 12 in the interior of the fuel filter 1, on which the filter element 2 and the coalescing element 3 are mounted, in the direction of a fuel outlet 13. In this case, the fuel first passes through a barrier layer 14 of hydrophobic material (fifth stage). Due to the water-repellent effect of the barrier layer 14 and the tens The tendency of water droplets to sink in the surrounding fuel prevents water from getting into the upper tube 12 arranged above it.

In the event that water is nevertheless entrained in the central tube 12, a stuffing 15 (sixth step) is provided in the central tube 12, which is also made of hydrophobic material, e.g. made of PTFE fibers, is formed and which prevents further transport of water to the fuel outlet 13 final.

In the manner described above, i. using the first to fifth stage or the first to sixth stage, a separation tion of water with high efficiency, especially in bio-diesel fuels can be realized.

Claims

claims

1 . A fuel filter (1) for filtering fuel, in particular diesel fuel, comprising: a filter element (2) for filtering particles from the fuel, a coalescing element (3) for coalescing water in the fuel, and a particularly cup-shaped housing (4 ) having an interior space (5), wherein a water collecting space (7) for collecting water separated from the fuel is formed in a bottom area (6) of the fuel-trapped internal space (5), and wherein means (8) are provided in the floor area (6) ) are provided for binding the separated water.

2. Fuel filter (1) according to claim 1, characterized in that as means for binding of water an absorbent solid (8) in the Wasserammeiraum (7) is provided.

3. Fuel filter (1) according to claim 2, characterized in that the absorbent solid (8) comprises hydrophilic fibers, which are preferably formed from defatted cellulose and / or surface-treated.

4. Fuel filter (1) according to one of claims 1 to 3, characterized in that the filter element (2) is connected upstream of the coalescing element (3) and is designed as a pre-coalescing filter element (2).

5. Fuel filter (1) according to one of the preceding claims, characterized in that a fuel outlet (13) of the fuel filter (1) is preceded by a water retention device (14,15).

6. Fuel filter (1) according to claim 5, characterized in that the water retention device (14, 15) in the region of a fuel outlet (13) in communication with the central tube (12) is arranged, which supports the filter element (2).

7. Fuel filter (1) according to claim 6, characterized in that the water retention device comprises a barrier (14), which consists of a hydrophobic material.

8. Fuel filter (1) according to claim 6 or 7, characterized in that the water retention device comprises a plug (15) in the central tube (12), wherein the plug (15) is formed of hydrophobic material.

9. Fuel filter (1) according to any one of claims 7 or 8, characterized in that provided as a hydrophobic material is pure or water-repellent treated fibers or mesh of PTFE (polytetrafluoroethylene), PA (polyamide) or polyester.

10. Fuel filter (1) according to one of the preceding claims, characterized in that the coalescing element (3) is followed by a flow guide (11) for the separation of water by gravity.

1 1. Fuel filter (1) according to claim 10, characterized in that the flow guide (11) takes place through an annular gap.

12. Fuel filter (1) according to one of the preceding claims, characterized in that the coalescing element (3) is followed by a water trap (10).