EP1598595B1 - Evaporator arrangement - Google Patents

Description

The present invention relates to an evaporator arrangement for delivering a fuel vapor into a mixing chamber according to the preamble of claim 1.

Such evaporator arrangements are used for example in fuel-operated heaters for motor vehicles, these heaters can be used in turn as a heater or as a heater. By the fuel to be evaporated and in a mixing chamber also to be introduced combustion air, a mixture of fuel vapor and combustion air is generated, which can be ignited and burned to generate heat. However, such evaporator arrangements are also used in so-called reformers to produce in a mixing chamber, a mixture of vaporized fuel, ie vaporized hydrocarbon, and other mixed material, for example, air or water vapor. This mixture is then passed to a catalyst assembly to produce a hydrogen-containing gas mixture by catalytic reaction.

In the case of evaporator arrangements or burners or / and reformers that use them, there is basically the problem that an impairment of both the evaporation operation per se and, for example, the combustion operation can be produced by not optimally running fuel evaporation or fuel feed into the mixing chamber. Thus, uneven introduction of the liquid fuel to be evaporated into a porous evaporator medium will result in correspondingly uneven fuel vaporization to the mixing chamber. Due to the supersaturation of certain areas of the porous evaporator medium with liquid fuel, the risk of leakage amplified by fuel droplets from the porous evaporator medium. If this occurs especially in the region between the porous evaporator medium and the associated heating device, this can lead to cracking, that is to the formation of deposits between the evaporator medium and the heating device, and the detachment and lifting of the evaporator medium. Furthermore, there is a risk that the fuel, which generally wets slightly in the liquid state, may move along surfaces as it exits the porous evaporator medium and may also get into the area of a fan for conveying air past the fan. The selective introduction of the liquid fuel in the porous evaporator medium continues to run the risk that a very nonuniform fuel distribution by gravity on the one hand and by capillary action on the other hand occurs and thus not the entire surface of the evaporator medium can be used for Brennstoffabdampfung, but for a defined mixture formation may be required.

An evaporator arrangement according to the preamble of claim 1 is known from DE 39 14 611 A1 known. In this known evaporator arrangement, a porous disk-like porous evaporator medium is received in a dish-like carrier. At the back of the cup-like carrier is a stick glow plug which is capable of heating the porous evaporator medium and the liquid fuel contained therein.

The DE 101 30 638 A1 discloses an evaporator assembly having a multi-layered porous evaporator medium disposed in a cup-like housing. In the region in which fuel is fed through a bottom region by means of a fuel feed line, a plate-like fuel deflector element may be arranged between two layers of the porous evaporator medium, which is the inlet region for the liquid fuel covered.

The US-A 5,082,175 discloses an evaporator arrangement in which a porous evaporator medium is arranged in a pot-like housing. Between a arranged at the back of the evaporator medium glow plug and the evaporator medium is a plate-like bottom portion.

The EP 1 484 552 A1 discloses an evaporator assembly having a pot-like housing. At a bottom region of the cup-shaped housing is arranged a combustion chamber facing a porous evaporator medium. At the back of the bottom region is an electrically energizable heating device, which can provide a projecting region for ignition conditions in the region of the porous evaporator medium which can be heated by the latter and penetrates the bottom region and the porous evaporator medium.

It is the object of the present invention to provide an evaporator arrangement for delivering a fuel vapor into a mixing chamber, which has an improved evaporation behavior.

This object is achieved by an evaporator arrangement for emitting a fuel vapor into a mixing chamber according to claim 1. This comprises a porous evaporator medium, a liquid fuel leading to the porous evaporator medium line arrangement and a heater on a side facing away from the mixing chamber or facing away from the back of the porous Evaporator medium, wherein between the porous evaporator medium and the heater is arranged a direct contact between these suppressive separating element.

To the fuel distribution in the porous evaporator medium and thus also To further influence the fuel evaporation from this, a fuel flow guide formation is formed in the porous evaporator medium. Such a fuel flow guide formation comprises compressed regions or recessed regions in the porous evaporator medium, which then have a different capillary flow behavior or locally prevent the occurrence of capillary flow and thus create barriers for the fuel flow.

It is essential in the present invention that between the liquid fuel receiving and the fuel vapor emitting porous evaporator medium and its associated heater is a separator that not only ensures a uniform heat input into the porous evaporator medium, but also ensures that an exit from Fuel vapor at the back of the porous evaporator medium can be prevented as well as the leakage of liquid fuel at the back of the porous evaporator medium.

It should again be noted that as "fuels" in the context of the present invention generally liquid hydrocarbons, such. Gasoline, diesel, biodiesel and the like, are considered, for example, are available for combustion, but nevertheless also be used to be implemented in a reformer for hydrogen production for a fuel cell system.

In order to be able to further support the above-mentioned improved heat introduction or distribution, it is proposed that the separating element be formed from a material that conducts heat well, preferably metal.

According to a particularly advantageous aspect, it can be provided that the separating element substantially the entire back of the porous evaporator medium covered. This ensures that practically the entire porous evaporator medium is thermally contacted and that over the entire rear side the escape of fuel or fuel vapor can be prevented.

In order to ensure at the outer edge region of the porous evaporator medium that liquid fuel can not escape from the porous evaporator medium there, it is proposed that the separating element overlap an outer edge region of the porous evaporator medium. This can be done, for example, in that, in the case of a planar design of the porous evaporator medium, the separating element is designed like a shell and is arranged with a dish bottom at the back of the porous evaporator medium, while the shell edge then overlaps the outer edge region of the porous evaporator medium, i. surrounds this outer edge region or rests there.

For fuel introduction into the porous evaporator medium, the separating element may have a fuel introduction opening for the line arrangement.

A further improved fuel distribution behavior can be obtained by providing a fuel distribution channel arrangement on the separating element starting from the fuel introduction opening.

In order to avoid leakage of liquid fuel, particularly in the region in which the porous evaporator medium receives liquid fuel from the fuel line arrangement, it is proposed that the line arrangement penetrate through the fuel introduction opening and be held under pressure against the porous evaporator medium with a discharge end.

Furthermore, taking into account the installation situation and thereby also acting on the liquid fuel in the porous evaporator medium Gravity proposed that the porous evaporator medium has a peripheral contour, which is adapted to a peripheral contour of a mixing chamber, preferably a bottom portion thereof, and that the line arrangement is introduced eccentrically to the porous evaporator medium.

Furthermore, the distribution behavior of the fuel in the porous evaporator medium to achieve improved Brennstoffabdampfung can be influenced by the fact that the porous evaporator medium is constructed in multiple layers and the layers at least partially have a different fuel conductivities.

The present invention further relates to a vehicle heater comprising an evaporation arrangement according to the invention.

Further, the present invention relates to a reformer assembly with an evaporator assembly according to the invention, as mentioned, to produce a mixture of fuel vapor, so hydrocarbon vapor, and air and / or water vapor and / or recirculated combustion or fuel cell exhaust gases.

Fig. 1

eine Längsschnittansicht der wesentlichen Komponenten einer Verdampferanordnung;

Fig. 2

eine der Fig. 1 entsprechende Ansicht einer alternativen Ausge- staltungsform;

Fig. 3

eine Detailansicht des mit einem schalenartigen Trennelement zusammenwirkenden porösen Verdampfermediums einer weiteren alternativen Ausgestaltungsform;

Fig. 4

das schalenartige Trennelement der Fig. 3 in perspektivischer An- sicht;

Fig. 5

eine der Fig. 3 entsprechende Darstellung einer weiteren alterna- tiven Ausgestaltungsform;

Fig. 6

eine der Fig. 3 entsprechende Darstellung einer erfindungsgemäßen Ausgestaltungsform;

Fig. 7

eine Draufsicht auf ein poröses Verdampfermedium, die das Brennstoffverteilungsverhalten darstellt.

The present invention will be described below in detail with reference to the accompanying drawings by way of preferred embodiments. It shows:

Fig. 1

a longitudinal sectional view of the essential components of an evaporator assembly;

Fig. 2

one of the Fig. 1 corresponding view of an alternative embodiment;

Fig. 3

a detailed view of the with a shell-like separator cooperating porous evaporator medium of a further alternative embodiment;

Fig. 4

the shell-like separating element of Fig. 3 in perspective view;

Fig. 5

one of the Fig. 3 corresponding representation of a further alternative embodiment;

Fig. 6

one of the Fig. 3 corresponding representation of an embodiment of the invention;

Fig. 7

a plan view of a porous evaporator medium, which represents the fuel distribution behavior.

In Fig. 1 an evaporator assembly is generally designated 10. This evaporator assembly 10 essentially provides a peripheral region 12 and a bottom region 14, which together define a mixing chamber 16. As will be explained below, a mixture of, for example, air and a fuel vapor can be generated in this mixing chamber 16. This mixture can be ignited by using a projecting into the mixing chamber 16 ignition element 18 to use the resulting in the then running combustion heat. When using the evaporator assembly 10 in a heater, the heat generated during combustion can be transferred to a medium to be heated, so for example air or water. When using the evaporator assembly 10 in a reformer arrangement, the heat generated during combustion can be used to preheat the reformer assembly. In the reforming operation, however, the combustion is stopped or suppressed in order to be able to convert the mixture of hydrocarbon vapor, air and / or possibly other mixed material constituents into a catalyst arrangement and thereby hydrogen for a fuel cell system to be able to produce.

The peripheral region 12 is at the in Fig. 1 shown embodiment provided by a substantially cylindrical peripheral wall member 20 having a plurality of inlet openings 22 for air or other mixed material. A further approximately cylindrical component 24 encompasses an axial end region-axially with respect to a longitudinal center axis of the peripheral wall component 20-of this peripheral wall component 20 and holds with a step-like region 26 a porous evaporator medium 28 configured like a disc here together with a dividing element 30 likewise configured as a disk on the circumferential wall component 20. The porous evaporator medium 28 may, as is well known, braid, knitted fabric, foamed ceramic or the like. which is capable of distributing the liquid fuel or hydrocarbon introduced therein by capillary action. The rear side 32 of the porous evaporator medium 28 here completely overlapping separating element 30 is preferably formed of metal material, such as sheet metal material. It has a nozzle 34 formed by forming, into which a fuel line 36 opens and thus promotes liquid fuel in the region of the porous evaporator medium 28.

On the side facing away from the porous evaporator medium 28 side of the partition member 30 is a configured in the form of a heating coil 38 heating device is provided, which touches the partition member 30 in the largest possible area and thus contributes to the most uniform heating of the partition member 30. In order to avoid thermal losses, the heating coil 38 is covered on its side facing away from the separating element 30 by insulating material 40, which in turn is covered by an insulating material 40 in a further uniform manner on the entire back side 32 of the porous evaporator medium 28 Holding plate 42 and a locking ring 44 is fixed to the component 24. Thus, the heating coil 38 is between the insulating material 40 and the separating element 30 locked in the direction of the longitudinal axis L.

By providing the separating element 30 on the rear side 32 of the porous evaporator medium 28, it is ensured that the liquid fuel introduced into it can evaporate only in the direction of the mixing chamber 16. A fuel evaporation to the rear, ie in the direction of the heating coil 38, is not possible, with the result that no deposits can be generated in this area. At the same time the risk of leakage of liquid fuel at the back 32 of the porous evaporator medium 28 is completely prevented. To this end, the separating element 30, which completely covers the porous evaporator medium 28, contributes to this. Furthermore contributes to that by cooperation of the line 36 with the nozzle 34 in this area fuel can not escape in liquid form. In the edge region of the porous evaporator medium 28 or the separating element 30, the escape of liquid fuel or a fuel vapor is prevented by the fact that this edge region is completely surrounded first by the component 24 and thus in cooperation with the peripheral wall member 20 is a virtually liquid and vapor-tight closure the porous evaporator medium 28 is provided to the outside. This can be further supported by the fact that the porous evaporator medium 28 is clamped together with the separating element 30 between the shoulder 26 and the peripheral wall member 28 and thus is compressed there. In this case, the escape of both liquid and vapor fuel over the outer peripheral edge 46 of the porous evaporator medium 28 is practically impossible.

One recognizes in Fig. 1 Furthermore, that the fuel line 36 with respect to the longitudinal center axis L is brought eccentrically to the porous evaporator medium 28. This contributes, for example, to the in Fig. 1 illustrated installation situation, taking into account the gravity occurring in this state, a very uniform fuel distribution over the entire volume range of the porous evaporator medium 28 will take place.

This in Fig. 1 shown porous evaporator medium 28 may be prepared together with the separating element 30, for example, characterized in that the provided for the construction of the porous evaporator medium 28, the chip-like or wire-like material is applied to a metal plate blank and then subjected to a sintering process. It is thus created a solid and stable composite, which can receive its final peripheral shape, such as a circular shape, only later in a punching process.

A modified embodiment is in Fig. 2 shown. Here, in the following, only to the embodiment according to Fig. 1 existing differences. In particular, it can be seen that the separating element 30 no longer has a planar, plate-like configuration, but a shell-like configuration with a bottom region 50 and a peripheral wall region 52. In this shell-like configuration now the porous evaporator medium 28 is fitted, so that its outer peripheral edge 46 is covered by the separating element 30. The heating coil 38 is again located on the rear side of the separating element 30, followed by the insulating material 40 and the holding plate 42. The separating element 30 is now held between this holding plate 42 or the securing ring 44 and a radially inwardly extending projection 54 of the component 24.

In this embodiment as well, it is thus ensured that the liquid fuel once introduced into the volume region of the porous evaporator medium 28 can only escape in the direction of the mixing chamber 16, but can not escape from the porous evaporator medium 28 on the rear side 32.

Of course, in this embodiment, the assembly comprising the porous evaporator medium 28 and the separator 30 may be manufactured as described above. In principle, however, it is also possible to insert the already prepared porous evaporator medium with its intended peripheral contour in the shell-like separator 30 and bring by compaction in its ready state, i. to produce the desired final porosity. The connection between the porous evaporator medium 28 and the separating element 30 can be realized for example by sintering. In principle, it is also conceivable to hold the porous evaporator medium 28 by gripping it with the circumferential wall region 52 of the separating element 30 also on the front side 56 facing the mixing chamber 16. The above-mentioned compression of the porous evaporator medium 28 in the separating element 30 can contribute to the fixation, since this can lead to an expansion of the evaporator medium 28 radially outward and thus pinching on the separating element 30.

Another variation is in the FIGS. 3 and 4 shown with their essential components. It can be seen again the shell-like designed partition member 30 with its bottom portion 50 and its peripheral wall portion 52. In the nozzle 34, the fuel line 36 is inserted. At the bottom region 50, an example circular depression 58 is formed. In this, a deflection element 60 is added to the rear side 32 of the porous evaporator medium 28. This is opposite to an outlet end 62 of the fuel line 36 and ensures that the liquid fuel emerging there can not enter the porous evaporator medium 28 directly in this area. Rather, the initially still liquid fuel is deflected to the outside and thus pre-distributed over a larger surface area of the back of the porous evaporator medium 28. This can also be supported by the fact that starting from the depression 58 in an approximately star-like configuration, channels 64 are formed on the bottom region 50, which further direct the liquid fuel outwardly toward the outer edge 46 of the porous evaporator medium and thus provide for a faster and more uniform pre-distribution before the liquid fuel enters the porous evaporator medium 28 at the rear 32 thereof.

One recognizes in Fig. 3 Furthermore, that the porous evaporator medium 28 is multi-layered, here, for example, three layers, with layers 66, 68 and 70 is constructed. The ply 66 provides the backside 32 while the ply 70 provides the frontal 56. Due to the layered structure of the porous evaporator medium 28, a further influence on its fuel distribution characteristic can be taken. In particular, it is possible, by building up the different layers of different materials, for example ceramic material, metal material or a mixture thereof, with different fiber length, different fiber shape and also different fiber orientation, to ensure that a desired fuel line behavior will occur. Thus, for example, the layer 66 may be formed so that it very quickly absorbs liquid fuel and makes a coarse distribution in its volume range. The then somewhat finely pored layer 68, for example, can make the liquid fuel already predistributed to it from the layer 66 uniform, while the layer 70 can also be optimized with regard to the thermal loads that occur.

Another variation is in Fig. 5 shown. Here, too, one recognizes again the shell-like configured separating element with its bottom region 30 and its wall 52. The fuel line 36 is introduced into the bottom region 50 or the connecting piece 34 provided thereon. The fuel line 36 passes through not only an inlet opening 72 on the separating element 30, but also a corresponding opening in the porous evaporator medium 28 completely. The fuel line 36 thus protrudes beyond the front 56 of the porous evaporator medium 28 in the direction of the mixing chamber 16 and holds by a disk 74 fixed thereto the porous At the same time, the disk 74 also serves to forcibly force an improved distribution of the liquid fuel emerging from the fuel line 36 and entering the volume range of the porous evaporator medium 28 directly, since this is not directly in the range the fuel line 36 can emerge from the porous evaporator medium 28 again.

In order to obtain a reliable introduction of the liquid fuel into the volume range of the porous evaporator medium 28 in this embodiment, the fuel line 36 has a plurality of radially outwardly extending passage openings 76, the liquid supplied by a central opening 78 liquid in the discharge end region 62 directly into the under pressure lead against the outside of the fuel line 36 held porous evaporator medium 28. It will be understood that the central opening 78 is sealed at the end of the fuel line 36 which is engaged in the mixing chamber 16.

At the in Fig. 6 shown embodiment of the invention, the fuel line 36 at its discharge end 62 has a blade-like edge 80. This is held under pressure against the back 32 of the porous evaporator medium 28. In this way, too, it is ensured that the entire fuel supplied via the central opening 78 of the fuel line 36 enters the volume region of the porous evaporator medium 28 and does not run out again at the rear in the area of the junction. This is further prevented by the fact that, as already stated above, substantially the entire rear side 32 is covered by the separating element 30, namely the bottom region 50 thereof. The solid bond between the fuel line 36 and the separator 30 in the region of the nozzle 34 can be done for example by soldering or by clamping fit. As in the embodiment according to Fig. 5 is in the range of Fuel introduction into the porous evaporator medium 28 of the line 36, a baffle 74 opposite.

In Fig. 7 Figure 3 is an axial view of a porous evaporator medium 28 as may be employed in the previously described embodiments. It can be seen with respect to the center of the here circular shaped contour of the porous evaporator medium 28 offset fuel injection in the fuel line 36. Next can be seen under the fuel inlet an approximately U-shaped formation 82 in the porous evaporator medium 28, which the flow behavior of the fuel in the porous evaporator medium 28th affected. This formation 82 can contribute, for example, by locally compacting the porous evaporator medium to build up a flow barrier, that is to say a region with increased flow resistance. The consequence of this is that much greater utilization of the volume range of the porous evaporator medium 28 can be enforced as compared to fuel spreading as obtained by the inner dashed area 84, so that the area 86 outlined in the outer dashed line in FIG Essentially contributes to the fuel intake, which is primarily considered the distribution under gravity. Of course, the capillary action also contributes to the fact that the fuel can still reach other regions of the porous evaporator medium 28. Such compressed or formed by impressions areas may also be provided on the back 32 of the porous evaporator medium 28, as shown by the depression 88 in Fig. 6 clarified. This depression 88 serves to pre-distribute the fuel before it is picked up in the volume range of the porous evaporator medium 28, ie, similar to the embodiment according to FIGS FIGS. 3 and 4 to provide a channel arrangement that allows a rough pre-distribution of the fuel.

The present invention provides an evaporator arrangement, which ensures that the fuel or hydrocarbon to be vaporized reaches the volume region of the porous evaporator medium as uniformly as possible, can practically no longer emerge from this volume region at the rear side facing away from a mixing chamber and at the front side facing a mixing chamber as uniformly as possible and with as efficient utilization as possible the entire surface of this front can evaporate.

It should be noted that, of course, the aspects shown in the various embodiments illustrated can be combined. So could of course also in the embodiments according to the FIGS. 1 to 3 Indentations or barriers are used for the defined fuel line in the volume range or for fuel pre-distribution on the porous evaporator medium.

Claims (11)

1. Evaporator arrangement for discharging fuel vapour into a mixing chamber, comprising a porous evaporator medium (28), a conduit arrangement (36) carrying liquid fuel to the porous evaporator medium (28) and a heating device (38) at a back side (32) of the porous evaporator medium (28) which is or may be positioned facing away from the mixing chamber (16), a separator (30) being arranged between the porous evaporator medium (28) and the heating device (38) preventing direct contact between the latter, characterized in a fuel flow guidance formation (82, 88) being formed in the porous evaporator medium (28) by means of parts of the porous evaporator medium (28) which are compressed by stamping.
2. Evaporator arrangement according to claim 1,
   characterized in the separator (30) being made of a material with good heat conductance, preferably of metal.
3. Evaporator arrangement according to claim 1 or 2,
   characterized in the separator (30) covering substantially the complete back side (32) of the porous evaporator medium (28).
4. Evaporator arrangement according to claim 1 to 3,
   characterized in the separator (30) overlapping an outer edge region (46) of the porous evaporator medium (28).
5. Evaporator arrangement according to claim 1 to 4,
   characterized in the separator (30) comprising a fuel insertion aperture (72) for the conduit arrangement (36).
6. Evaporator arrangement according to claim 5,
   characterized in a fuel distribution channel arrangement (64), extending from the fuel insertion aperture (72), being provided at the separator (30).
7. Evaporator arrangement according to claim 5 or 6,
   characterized in the conduit arrangement (36) extending through the fuel insertion aperture (72) and being held under pressure against the porous evaporator medium (28) with one discharge end (62).
8. Evaporator arrangement according to claim 1 to 7,
   characterized in the porous evaporator medium (28) comprising a circumferential outline matching a circumferential outline of a mixing chamber (16), preferably of a bottom part (14) of the latter, and in the conduit arrangement (36) being eccentrically directed towards the porous evaporator medium (28).
9. Evaporator arrangement according to claim 1 to 8,
   characterized in the porous evaporator medium (28) being multilayered, the layers (66, 68, 70) at least partly having different fuel supply capacities.
10. Vehicle heating device, comprising an evaporator arrangement according to one of claims 1 to 9.
11. Reformer arrangement, comprising an evaporator arrangement according to one of claims 1 to 9.

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