EP2752620A1 - Catalytic burner, particularly for a vehicle heating system - Google Patents

Abstract

The catalytic burner (10) has a mixing chamber (24), a combustion air supply arrangement for supplying of combustion air to the mixing chamber, a fuel supply arrangement for supplying of fuel to the mixing chamber and a catalyzer arrangement (46) with a catalyzer unit (48). The catalyzer arrangement is arranged downstream the mixing chamber and the catalyzer unit is flow-throughable by the fuel-combustion air mixture. The fuel supply arrangement receives a liquid fuel from a fuel supply line (34) and comprises porous evaporator arrangement (28) emitting fuel vapor in the mixing chamber. The catalyzer unit comprises a grid-like carrier with catalyzer material at its surface.

Description

The present invention relates to a catalytic burner, in particular for vehicle heating, for the catalytically assisted combustion of a fuel / combustion air mixture comprising a mixing chamber, a Verbrennungsluftzuführanordnung for supplying combustion air to the mixing chamber, a Brennstoffzuführanordnung for supplying fuel to the mixing chamber, downstream of the Mixing space a catalyst arrangement with at least one of the fuel / combustion air mixture can flow through the catalyst unit.

In motor vehicles, fuel-powered heaters are used to provide heat as auxiliary heaters or auxiliary heaters. In these a mixture of fuel and combustion air is ignited and burned. The resulting heat is transferred to a heat transfer medium, for example the air to be introduced in a vehicle interior or the coolant circulating in an engine coolant circuit. In order to meet the increasingly stringent requirements for pollutant emissions, especially in a startup phase of combustion, it is known to use catalytic burners. In these systems, the combustion of fuel and combustion air is achieved by a process catalytically supported on the surface of catalytic material.

Such a catalytic burner is from the WO 2007/003649 A1 known. In this catalytic burner, the fuel supplied in droplet form through a fuel supply line is introduced into a pot-shaped evaporator. This is open opposite to the flow direction of the combustion air supplied to the combustion air for combustion. Due to the combustion air flowing into the pot-like evaporator, a turbulence arises in the interior of this pot-like evaporator, which causes mixing of the combustion air with the combustion air which accumulates therein Fuel leads. The mixture of combustion air and fuel thus formed emerges from this over an edge region of a peripheral wall of the pot-like evaporator and then passes on to a combustion chamber in which a catalyst arrangement with a plurality of catalyst units following one another in the flow direction and through which the fuel / combustion air mixture can flow this fuel / combustion air mixture is provided.

It is the object of the present invention to provide a catalytic burner, in particular for a vehicle heater, with which an efficient catalytically assisted combustion process can be achieved.

According to the invention, this object is achieved by a catalytic burner, in particular for a vehicle heater, for the catalytically assisted combustion of a fuel / combustion air mixture comprising a mixing chamber, a combustion air supply arrangement for supplying combustion air to the mixing space, a fuel supply arrangement for supplying fuel to the mixing space, downstream of the mixing chamber, a catalyst arrangement with at least one of the fuel / combustion air mixture can flow through the catalyst unit.

It is further provided that the Brennstoffzuführanordnung comprises a liquid fuel from a Brennstoffzuführleitung receiving and fuel vapor in the mixing chamber dispensing porous evaporator assembly, and / or that at least one catalyst unit comprises a grid-like carrier with catalyst material on its surface.

In the case of the catalytic burner constructed according to the invention, measures are provided individually and in combination which significantly increase the quality of the catalytically assisted combustion of the fuel / combustion air mixture. By providing a porous evaporator arrangement, efficient mixing of fuel and combustion air is ensured since it is generally supplied in liquid form Incorporated in the porous evaporator assembly, therein by Kapillarförderwirkung, possibly also supported by the influence of gravity, distributed and delivered to the comparatively large surface area of this porous evaporator assembly in the mixing chamber. This fuel vapor may mix with the combustion air in the mixing chamber and, if appropriate, downstream of the following spatial region. The risk that larger liquid fuel accumulations arise or fuel in droplet form is carried in the combustion air, thereby substantially completely excluded. The provision of at least one catalyst unit with a lattice-type support and catalyst material on its surface can also improve the catalytically assisted combustion process. By means of a catalyst unit designed in this way, it is possible to provide the lattice-type support in a spatial configuration adapted to the structural conditions in the catalytic burner, possibly to deform it, on the one hand improving the flow characteristics, and on the other hand providing the catalytically assisted combustion Surface of such a catalyst unit can be increased.

In an efficient mixing of the combustion air with fuel, especially from a porous evaporator assembly discharged fuel vapor, ensuring configuration is proposed that a burner housing bounded by a peripheral wall at least one catalyst unit containing combustion chamber, wherein on a bottom wall of the burner housing an approach with a peripheral wall and a provided to the bottom wall of the burner housing offset in the direction of a longitudinal axis disposed bottom wall, wherein at least a portion of the porous evaporator assembly is supported on the peripheral wall and / or the bottom wall of the neck.

In order to use the inner volume region of the approach as a mixing chamber or at least a portion of the mixing chamber, it is proposed that in the peripheral wall of the approach at least one leading to the combustion chamber Throughflow opening is provided and that at least part of the porous evaporator arrangement is provided on the peripheral wall and / or the bottom wall of the projection on a side facing away from the combustion chamber side.

The passage of fuel and combustion air from the mixing chamber to a downstream region, in which the catalyst assembly is arranged, can be ensured that at least one flow opening is provided in a region of the peripheral wall of the approach approaching the bottom wall of the approach and / or in that at least one through-flow opening is provided in a region of the circumferential wall of the neck close to the bottom wall of the burner housing.

In this case, advantageously at least one, preferably each flow opening in the peripheral wall of the approach is covered by a catalyst unit.

In order to be able to provide this catalyst unit with the largest possible surface usable for the catalytic reaction, it is proposed that at least one, preferably each throughflow opening in the peripheral wall of the projection is covered by a catalyst unit.

In an alternative embodiment of the inventively constructed catalytic burner can be provided that at least one part of the porous evaporator assembly is provided on one of the peripheral wall of the burner housing side facing the peripheral wall of the neck and that in the peripheral wall of the burner housing in the axial extension region of the neck at least one to the mixing chamber leading flow opening is provided. In this structure, a volume area between the peripheral wall of the burner housing and the peripheral wall of the neck is used as a mixing chamber. The resulting mixture of fuel and combustion air can then in the direction be promoted downstream of the catalyst assembly. In particular, it can be provided that a space formed between the peripheral wall of the burner housing and the peripheral wall of the neck at its end remote from the bottom wall of the burner housing end is at least partially limited by a catalyst unit. Thus, this catalyst unit essentially limits the mixing space and thus ensures that a first stage of the catalytically assisted combustion can take place directly at the outlet of the fuel / combustion air mixture from the mixing space.

In a particularly advantageous embodiment, it is further proposed that at least one flow aperture with at least one flow opening is provided on the circumferential wall of the burner housing and that at least one, preferably each flow opening is covered by a catalyst unit. The provision of one or more flow orifices and catalyst units in association with this ensures that the heat release in the region of a respective catalyst unit positioned there can be controlled by a comparatively high flow rate of the fuel / combustion air mixture to be combusted, thus avoiding local overheating ,

The efficiency of the catalytically assisted combustion can be further increased by dividing a space formed axially between the projection and a flow aperture by a catalyst unit into a radially outer space area and a radially inner space area. In an alternative construction of the catalytic burner constructed according to the invention, it is proposed that a burner housing with a circumferential wall delimits a combustion chamber containing at least one catalyst unit and at least one part of the porous evaporator arrangement is provided on the circumferential wall of the burner housing and / or a bottom wall of the burner housing. In the case of such a structure, the approach discussed above can thus be essentially dispensed with. The peripheral wall and / or the bottom wall The burner housing can also simultaneously assume the functionality as a carrier for at least part of the porous evaporator arrangement.

In this case, it may be provided, for example, that the porous evaporator arrangement is provided on an outer side of the bottom wall facing away from the combustion chamber and that at least one throughflow opening leading to the combustion chamber is provided in the peripheral wall of the burner housing, preferably in a region near the bottom wall. In this construction, therefore, essentially the entire volume enclosed by the peripheral wall and the bottom wall of the burner housing can be used as the combustion chamber. The mixing of the fuel with the combustion air takes place upstream or outside of this volume.

In this structure, the catalytically assisted combustion can be carried out particularly efficiently if at least one, preferably each flow-through opening is covered by a catalyst unit. In particular, the catalyst unit can be provided on an inner side of the peripheral wall of the burner housing facing the combustion chamber, so that large parts of the surface of the catalyst unit face the combustion chamber and can be used for the catalytically assisted reaction.

In an alternative embodiment, it is proposed that the porous evaporator arrangement is provided on an inner side of the bottom wall of the burner housing facing the combustion chamber and that at least one throughflow opening leading to the mixing chamber is provided in the circumferential wall of the burner housing, preferably in a region near the bottom wall. In this case, therefore, a region of the volume enclosed by the circumferential wall and the bottom wall of the burner housing near the bottom wall of the burner housing forms the mixing space or part of the mixing space, which supports a compact construction.

In a further alternative embodiment, it is proposed that the porous evaporator arrangement, which is essentially pot-shaped or cup-shaped and has a peripheral wall area and a bottom wall area, is supported on the circumferential wall. Due to the configuration of the porous evaporator arrangement with pot-like or dish-like configuration, the volume which can be used for distributing the initially liquid-supplied fuel and also the surface which can be used for fuel evaporation is increased. This also supports the efficient mixing of the fuel vapor emitted over a comparatively large surface area with the combustion air flowing around this surface.

In order to use the catalytically assisted combustion process as efficiently as possible in this construction of the porous evaporator arrangement, it is proposed that a catalyst unit be arranged on the porous evaporator arrangement. In particular, it may be provided that the catalyst unit comprises catalyst material applied to the building material of the porous evaporator arrangement. The porous material of the evaporator arrangement thus forms the carrier for catalyst material, so that an additional carrier can be dispensed with here.

Even if the burner housing is constructed without a neck provided on the bottom wall of the same, an efficient support of the combustion by the catalytic reaction can be achieved by providing at least one flow aperture with at least one flow opening on the circumferential wall of the burner housing and at least one, Preferably, each flow-through opening is covered by a catalyst unit.

In order to be able to increase the surface available for the catalytic reaction, it is proposed that at least one catalyst unit be formed in the upstream or downstream direction is, preferably vault-like, conical or cylindrical. Particularly suitable for this purpose is the construction of a respective catalyst unit with a grid-like support, which can then be deformed to obtain the installation form of the catalyst unit. This deformation can take place before or after the application of catalyst material to the lattice-type support not constructed from catalyst material. In principle, however, a lattice-type support constructed entirely of catalyst material could also be brought into the built-in form by deformation. Such a grid-like carrier constructed entirely of catalyst material also has catalyst material on its surface for the purposes of the present invention.

In order to be able to assist in the inventive construction of a catalytic burner with a porous evaporator arrangement, the fuel evaporation, in particular in a start phase of the combustion process, it is proposed that the porous evaporator assembly is associated with an electrically energizable heater.

Fig. 1

eine Längsschnittdarstellung eines in einem Fahrzeug einsetzbaren katalytischen Brenners;

Fig. 2

eine Abwandlung des in Fig. 1 dargestellten katalytischen Brenners im Längsschnitt;

Fig. 3

eine weitere Abwandlung des in Fig. 1 dargestellten katalytischen Brenners im Längsschnitt;

Fig. 4

eine weitere Abwandlung des in Fig. 1 dargestellten katalytischen Brenners im Längsschnitt;

Fig. 5

eine alternative Ausgestaltung eines katalytischen Brenners im Längsschnitt;

Fig. 6

eine weitere alternative Ausgestaltung eines katalytischen Brenners, im Längsschnitt;

Fig. 7

eine Abwandlung des in Fig. 6 dargestellten katalytischen Brenners, im Längsschnitt;

Fig. 8

eine weitere Abwandlung des in Fig. 6 dargestellten katalytischen Brenners, im Längsschnitt;

Fig. 9

eine weitere Abwandlung des in Fig. 6 dargestellten katalytischen Brenners, im Längsschnitt;

Fig. 10

eine weitere alternative Ausgestaltungsart eines katalytischen Brenners im Längsschnitt.

The present invention will be described below in detail with reference to the accompanying drawings. It shows:

Fig. 1

a longitudinal sectional view of a usable in a vehicle catalytic burner;

Fig. 2

a modification of the in Fig. 1 shown in longitudinal section of the catalytic burner;

Fig. 3

another variation of the in Fig. 1 shown in longitudinal section of the catalytic burner;

Fig. 4

another variation of the in Fig. 1 shown in longitudinal section of the catalytic burner;

Fig. 5

an alternative embodiment of a catalytic burner in longitudinal section;

Fig. 6

a further alternative embodiment of a catalytic burner, in longitudinal section;

Fig. 7

a modification of the in Fig. 6 shown catalytic burner, in longitudinal section;

Fig. 8

another variation of the in Fig. 6 shown catalytic burner, in longitudinal section;

Fig. 9

another variation of the in Fig. 6 shown catalytic burner, in longitudinal section;

Fig. 10

a further alternative embodiment of a catalytic burner in longitudinal section.

In Fig. 1 For example, a catalytic burner that can be used as a parking heater or auxiliary heater in a vehicle is generally designated 10. The catalytic burner 10 comprises a burner housing 12 elongated in the direction of a longitudinal axis L with a substantially cylindrical peripheral wall 14 and a bottom wall 16. At the bottom wall 16, for example, a projection 18 is provided in a central area, which has a circumferential wall 20 which is also substantially cylindrical, for example and a in the direction of the longitudinal axis L to the bottom wall 16 of the burner housing 12 offset bottom wall 22 includes.

Inside the neck 18, a mixing space generally designated 24 is provided. At the mixing chamber 24 side facing the bottom wall 22 of the projection 18, a porous evaporator assembly 28 is provided or supported. This porous evaporator arrangement 28 comprises a disk-like evaporator element 30 constructed of porous material. Between this and the bottom wall 22 of the projection 18, an electrically energizable heater 32 is provided. The evaporator element 30 may be constructed, for example, of nonwoven or braided material, foamed ceramic, metal foam or the like.

For example, concentric with the longitudinal axis L, a fuel supply line extends in the direction of the longitudinal axis L through a volume region lying upstream of the mixing chamber 24 into the mixing chamber 24 or into the evaporator element 30 provided on the bottom wall 22. Via the fuel feed line 34, it is conveyed by a fuel pump (not shown) , For example, metering pump, liquid fuel fed into the evaporator element 30. Due to the capillary action of the porous evaporator element 30, the liquid fuel is distributed in the internal volume thereof and evaporated at the side of the evaporator element 30 facing the mixing chamber 24 into the mixing space 24.

The volume traversed upstream of the mixing chamber 24 by the fuel supply line 34 forms a combustion air flow space 36. Through this combustion air flow space 36, the air to be mixed in the mixing space 24 with the fuel evaporated there is supplied by a combustion air blower. In order to achieve efficient mixing of this combustion air with the fuel vapor provided in the mixing chamber 24, a swirl device 38 can be carried on the bottom wall 16 of the burner housing 12, which ensures swirling of the combustion air introduced into the mixing chamber 24. Farther upstream of the swirl device 38, a non-return valve 40 may be provided which prevents flames resulting in the combustion process from striking back into a further upstream region of the combustion air flow space 36.

The fuel / combustion air mixture generated in the mixing chamber 24 passes through a plurality of formed in the peripheral wall 20 of the projection 18, slot-like flow openings 42 in a generally 44th designated combustion chamber of the catalytic burner 10. The flow-through openings 42 are for example elongated in the direction of the longitudinal axis L and adjacent to the bottom wall 22 of the projection 18 at.

In the combustion chamber 44, a catalyst arrangement 46 is arranged. This includes in the example shown the Fig. 1 three catalyst units 48, 50, 52. The catalyst unit 48 is substantially cylindrical and surrounds the peripheral wall 20 of the projection 18 at its the peripheral wall 14 of the burner housing 12 facing the outside. The mixture flowing through the flow openings 42 into the combustion chamber 44 passes through the catalyst unit 48, so that part of the mixture reacts on the surface of the catalyst unit 18 with the catalyst material provided therein or is supported by this catalyst material. Since the catalyst unit 48 is arranged around the projection 18 over the entire circumference, a comparatively large surface area is usable for a catalytically assisted reaction.

The mixture passing through the flow-through openings 42 passes, after passing through the catalyst unit 48, into a space 54 formed between the peripheral wall 20 of the projection 18 and the peripheral wall 14 of the burner housing 12, which end region is located in a bottom area of the catalyst unit 50 close to the bottom wall 22 of the projection 18 is axially limited. The catalyst unit 50 may be designed in the manner of an annular disk and be supported on the inner surface of the circumferential wall 14 of the burner housing 12 or / and the bottom wall 22 of the attachment 18 or / and the catalyst unit 48. The mixture entering the space 54 can thus react when flowing through the flow openings 42 or when flowing in the space 54 on the surface of the catalyst unit 48 and can continue to react on leaving the space 54 and thus on passing through the catalyst unit 50 on the surface.

Farther downstream of the catalyst unit 50, a flow screen 56, for example designed as an annular disc, is carried on the circumferential wall 14 of the burner housing 12. This has, for example, in its central region on a flow-through opening 58, which is covered by the disk-like catalyst unit 52. The downstream of the catalyst unit 50, ie downstream of the space 54, flowing toward the flow orifice 56 and not yet burned on the catalyst units 48, 50 can be burned catalytically supported in a final stage of the catalytic reaction to the catalyst unit 52, so that after the Flow through the three successive in the flow direction of the catalyst units 48, 50, 52 is burned substantially all of the fuel / combustion air mixture generated in the mixing chamber 24. The downstream of the flow restrictor 56 lying, so on the third catalyst unit 52 still following part of the peripheral wall 14 of the burner housing 12, the combustion gases with the heat of combustion transported in the manner of a flame tube in the direction of a in the Fig. 1 to guide heat exchanger assembly, not shown, where at least a portion of the heat can be transferred to a heat transfer medium.

The catalyst units 48, 50, 52 of the catalyst arrangement 46 can in principle be constructed with a lattice-type support, preferably of metal material, which is coated on its surface with catalyst material. Such a grid-like carrier allows the passage of mixture to be combusted by catalytically assisted reaction, but at the same time is easily brought into the desired installation configuration by deformation. Thus, for example, the catalyst unit 48, which has a generally cylindrical configuration, can be bent out of a strip-like blank whose mutually facing end regions can be connected to one another in a suitable manner, for example by material fit or by deformation. Before or after this shaping process, the grid-like carrier can be coated with the catalyst material.

In principle, however, the structure of the catalyst units 48, 50, 52 could also be such that the lattice-type support itself is already constructed from catalyst material and thus, of course, also has on its surface catalytic material to support the combustion.

With the in Fig. 1 shown construction of a catalytic burner 10 is on the one hand by the very efficient mixing of the fuel vapor generated in the porous evaporator assembly 28 with the introduced into the wiper space 24 combustion air, on the other hand by positioning the catalyst units 48, 50, 52 in areas with comparatively high flow velocity and strong \ / vortexing of the emerging from the mixing chamber 24 mixture a very efficient combustion process with comparatively low pollutant emissions are guaranteed. Because of the positioning of the same, in the area of the catalyst units 48, 50, 52, a comparatively high flow velocity of the fuel / combustion air mixture or of the combustion exhaust gases resulting from combustion proceeding further upstream is ensured that overheating of the catalyst units does not occur occurs. Furthermore, the electrically energizable heating device 32, which is provided in association with the evaporator element 30 of the porous evaporator arrangement 28, ensures efficient fuel evaporation even in the starting phase, so that pollutant emissions can also be reduced in this phase at the beginning of combustion. This can be further assisted by the fact that an ignition device 60, for example Glühzündstift, is provided in the mixing chamber 24, which can support an ignition of the mixture provided in the mixing chamber 24 and thus already taking place in the mixing chamber 24 combustion.

The Fig. 2 shows a modified embodiment of the in Fig. 1 shown catalytic burner. Here and in the following Fig. 3 to 5 are components or assemblies, which components described above or modules correspond, denoted by the same reference numerals. It is referring to the Fig. 2 or on the following figures essentially only on existing to previous embodiments existing differences.

At the in Fig. 2 As shown, the evaporator element 30 of the porous evaporator arrangement 28 is supported directly on the inside of the bottom wall 22 of the projection 18 facing the mixing space 24. So here no additional electrically energizable heater is provided. The fuel evaporation can also be achieved in the start phase by the heat generated by the ignition device 60 or the combustion also taking place in the mixing chamber 24.

At the in Fig. 3 The design shown in the peripheral wall 20 of the projection 18 slot-like flow openings 42 are provided at a distance from the bottom wall 22 of the projection 18, but adjacent to the bottom wall 16 of the burner housing 12. The catalyst unit 48 covering the throughflow openings 42 also lies in this longitudinal region of the circumferential wall 20 and surrounds it on its outer side facing the circumferential wall 14 of the burner housing 12, but here adjacent to the bottom wall 16 of the burner housing 12.

It should be noted that, of course, in the in Fig. 3 illustrated embodiment variant between the evaporator element 30 and the bottom wall 22 of the projection 18 in Fig. 1 provided electrically energizable heater provided a could.

At the in Fig. 4 illustrated embodiment, the Bo-denwandung 22 of the projection 18 extends radially - relative to the longitudinal axis L-beyond the peripheral wall 20 of the approach, so that the space 54 at its side facing away from the bottom wall 16 of the burner housing 12 end not only by the catalyst unit 50, but is also limited by a radially projecting part of the bottom wall 22. This leads to a flow throttling or an increase in the flow speed of the mixture flowing out of the mixing chamber 24 into the combustion chamber 44 and there through the catalyst unit 50 and thus to improved heat removal from the region of the catalyst unit 50.

In Fig. 5 a construction of the catalytic burner 10 is shown, in which the mixing chamber 24 is provided substantially in the radially formed between the peripheral wall 14 of the burner housing 12 and the peripheral wall 20 of the projection 18 space 54. In this axial region of the circumferential wall 14, a plurality of flow-through openings 62 are provided distributed in the circumferential direction, through which the air flowing in in the combustion air flow space 36 now enters the mixing space 24 from radially outside. On the peripheral wall 14 of the burner housing 12 facing the outside of the peripheral wall 20, the substantially formed with a cylindrical shape evaporator element 30 of the porous evaporator assembly 28 is supported. The fuel supply line 34 feeds the liquid supplied fuel through branch lines 64 into the evaporator element 30. The fuel vapor is evaporated from the surface of the evaporator element 30 facing the mixing space 24 and mixed in the mixing space 24 with the combustion air fed into it.

At the end region facing away from the bottom wall 16 of the evaporator housing 12, the space 54, in this case the mixing space 24, is axially delimited by a region of the bottom wall 22 of the projection 18 radially projecting beyond the peripheral wall 20 of the projection 18 and the catalyst unit 48 the fuel mixing chamber 24 resulting fuel / combustion air mixture flows through the annular space between the peripheral wall 14 of the burner housing 12 and the bottom wall 22 of the projection 18 and thus passes through the catalyst unit 48 into the combustion chamber 44. There are in axial distance two flow louvers 56, 66 are each provided with a flow-through opening 58, 68 and a catalyst unit 52, 70 covering this.

Downstream of the catalyst unit 48, the catalyst unit 50, which now has a substantially cylindrical design, is arranged. This lies in the radial region of the circumferential wall 20 of the projection and divides the space 72 located axially between the bottom wall 22 of the projection 18 and the flow diaphragm 56 into a radially outer space region 74 and a radially inner space region 76. The mixture passing through the catalyst unit 48 Combustion gases produced at the catalyst unit 48 enter the space 72 and the radially outer space 74, respectively, and flow radially inwards through the substantially cylindrical catalyst unit 50 so as to enter the central area and thus the area of the flow opening 58 in the flow aperture 56 arrive. Thereby, an additional stage of the catalytic reaction in the region between the upstream flow orifice 56 and the exit from the mixing chamber 24 is achieved, in particular in a region of comparatively high flow velocity.

It should be noted that the heating of the evaporator element can be achieved by heat transfer. Of course, in this embodiment, too, an electrically energizable heating device could be provided on the rear side of the evaporator element 30 facing away from the mixing chamber 24.

An alternative embodiment of a catalytic burner is shown in U.S. Patent Nos. 4,946,675 Fig. 6 shown. Components or assemblies which correspond to the components or assemblies described above are designated by the same reference numerals with the addition of an appendix "a".

At the in Fig. 6 the construction of a catalytic burner 10a shown, the burner housing 12a is formed without recognizable in the figures described above approach. The peripheral wall 14a and the Bottom wall 16a define the combustion chamber 44a. Upstream of this combustion chamber 44a, bounded by a further housing portion 78a of the burner housing 12a, the mixing space 24a is formed. By through openings 80a formed near the bottom wall 16a of the burner housing 12a in the circumferential wall 14a of the burner housing 12a, the fuel / combustion air mixture generated in the mixing chamber 24a passes into the combustion chamber 44a. In the axial region in which the through-flow openings 80a are formed in the peripheral wall 14a, the here essentially cylindrically shaped catalyst unit 48a is provided on the inner side of the circumferential wall 14a facing the combustion chamber 44a, so that a first stage already enters the combustion chamber 44a the catalytic reaction can take place. This is followed by the first flow orifice 56a with the catalyst unit 58a provided thereon and the second flow orifice 66a with the catalyst unit 70a provided thereon.

The porous evaporator arrangement 28a or its porous evaporator element 30a is carried on the side facing away from the combustion chamber 44a and the mixing chamber 24a facing side of the bottom wall 16a of the burner housing 12a. The evaporator element 30a can be heated by the combustion heat generated in the combustion chamber 44a. Of course, an electrically energizable heating device could also be provided here between the evaporator element 30a and the bottom wall 16a. The evaporator element 30a is substantially planar, disk-like and advantageously covers the entire outside of the bottom wall 16a.

The Fig. 7 shows a modification of the in Fig. 6 shown construction. In this construction, the evaporator element 30a of the porous evaporator arrangement 28a is provided on the side of the bottom wall 16a of the burner housing 12a facing the combustion chamber 44a. The throughflow openings 80a provided near the bottom wall 16a in the peripheral wall 14a of the burner housing 12a pass over the combustion air flow space 36a supplied combustion air into the mixing chamber 24a, which is limited in this embodiment variant of the peripheral wall 14a and the bottom wall 16a of the burner housing 12a and the first flow restrictor 56a in the flow direction. The fuel / combustion air mixture produced in the mixing chamber 24a can pass through the flow-through opening 58a in the flow diaphragm 56a and thus the catalyst unit 52a into the combustion chamber 44a.

Also in this embodiment could be provided for heating or for additional heating of the evaporator element 30a between this and the bottom wall 16a of the burner housing 12a, an electrically energizable heater. Alternatively or additionally, the heating by heat conduction or heat radiation from the region of the combustion chamber 44a or these limiting assemblies, in particular the flow orifice 56a or the catalyst unit 58a and also the peripheral wall 14a of the burner housing 12a, take place.

In Fig. 8 is a variation of the in Fig. 7 shown embodiment of the catalytic burner 10a. Clearly visible in Fig. 8 in that the two catalyst units 52a, 70a carried on the flow orifices 56a, 66a are no longer in a planar configuration but in a curved configuration. The curvature here is oriented upstream. As a result of this curved configuration of the catalyst units 52a, 70a, the surface area of the catalyst units 52a, 70a can be significantly increased while the size of the flow-through openings 58a, 68a is otherwise unchanged, which increases the efficiency of the catalytically assisted combustion. Furthermore, in Fig. 8 it can be seen that the flow-through openings 58a, 68a provided in the flow orifices 56a, 66a can have mutually different sizes. Accordingly, the two catalyst units 52a, 70a are dimensioned differently from each other.

It should be noted that, of course, in all other embodiments, in particular the catalyst units supported on the flow orifices, but of course also the catalyst units positioned at other locations, may be provided with such curvature and the surface enlargement generated thereby. This embodiment is particularly easy to achieve, if, as stated above, the catalyst units are constructed with a lattice-like support, preferably of metal material, which before or after the application of the catalyst material, or possibly even constructed of catalyst material by forming into the desired Installation configuration can be brought. Of course, other shapes, for example a conical or a cylindrical shape of the catalyst units, are also possible. It is also possible to buckle in the downstream direction while maintaining the principle of enlarging the surface usable for the catalytic reaction.

The Fig. 9 shows another modification of the catalytic burner 10a. In this case, a plurality of flow-through openings 58, 58a 'are provided in the mixing chamber 24a axially delimiting flow aperture 56a. These are eccentric to the longitudinal axis L and can be provided, for example, in a ring-like pattern about the longitudinal axis L at the same distance and / or each other the same or different size. In association with each flow-through opening 58a, 58a ', a catalyst unit 52a, 52a' is provided. These can, as previously with reference to the Fig. 8 set out to be bulged here towards the mixing chamber 24a.

Between the evaporator element 30a of the porous evaporator arrangement 28a and the catalyst units 52a, 52a ', web elements 82a, 82a' constructed of metal material, for example, provide enhanced heat transfer from the catalyst units 52, 52a to the evaporator element 30a and thus the fuel evaporation from the evaporator element 30a support.

It should be noted that these web elements 82, 82a 'may be provided independently of the shaping and also of the number or positioning of the catalyst units 52a, 52a'. It should also be pointed out that, of course, a different number of throughflow openings and catalyst units assigned to them can also be provided in the case of the flow orifices of the other embodiments. In particular, a centrally, ie concentrically to the longitudinal axis L concentric flow opening and surrounding a plurality of eccentrically positioned flow openings could be provided.

Another alternative embodiment of a catalytic burner is disclosed in U.S. Patent Nos. 4,136,866 Fig. 10 shown. Components or assemblies which correspond to components or assemblies described above with regard to construction or function are described by the same reference numerals with the addition of an appendix "b".

At the in Fig. 10 the further housing portion 78b of the burner housing 12 forms substantially the mixing chamber 24b upstream of the peripheral wall 14b or the bottom wall 16b of the burner housing 12b which acts as a flow diaphragm 56b. In this further housing section 78b, the porous evaporator arrangement 28b provided with cup-shaped shaping is carried by a plurality of webs 84b, 84b '. This comprises a circumferential wall region 86b and a bottom wall region 88b which is formed integrally therewith, for example, and which is positioned axially opposite the bottom wall 16b of the evaporator housing 12b.

The fuel supply line 36b ends in a nozzle area 90b, which is designed, for example, in the manner of a Venturi tube, already in front of the porous evaporator arrangement 28b. The fuel discharged from the fuel supply pipe 36b in a liquid form, for example, in a droplet shape, is passed through a portion of the combustion air supplied in the combustion air flow space 36b through the nozzle portion 90b toward the Interior promoted the cup-shaped porous evaporator assembly 28b. The fuel impinges on the inner surface of the porous evaporator assembly 28b, is absorbed by the latter and removed on its surface, in particular the outwardly facing surface, by the combustion air flow flowing therealong in vapor form.

For heating the porous evaporator assembly 28b, an electrically energizable heater 32b carried on the outside of the bottom wall portion 28b may be used. Their energization can take place via the webs 84b, 84b ', which carry the electrical insulation of the porous evaporator arrangement 28b.

In order to carry out a first stage of the catalytic reaction already where the mixing of combustion air and fuel begins, that is to say on the surface of the porous evaporator arrangement 28b, the porous evaporator arrangement can be provided on its surface with catalyst material, for example coated, so that in this area already a first catalyst unit 48b is formed. It can thus be seen here that the volume area which is used on the one hand as mixing space 24b, namely the volume area containing porous porous evaporator arrangement 28b in additional housing section 78b, can also be used partly as combustion chamber or part of combustion chamber 44b. So here is a Funktionszusammenmelzung in the production of fuel vapor on the one hand and the provision of a catalyst unit on the other hand provided in the porous evaporator assembly 28b. There is also a combination of functions in the use of a volume range on the one hand as a mixing space 24b and on the other hand as part of the combustion chamber 44b. It should be pointed out that, in particular, these functional blending can also be realized in the preceding embodiments by virtue of the fact that complete mixing of the fuel vapor with the combustion air can take place not only in the mixing chamber but also in parts of the combustion chamber still following thereon.

Claims (22)

A catalytic burner, in particular for vehicle heating, for the catalytically assisted combustion of a fuel / combustion air mixture, comprising a mixing space (24, 24a, 24b), a combustion air supply arrangement (36, 36a, 36b) for supplying combustion air to the mixing space (24, 24a 24b), a fuel supply arrangement (28, 34, 28a, 34a, 28b, 34b) for supplying fuel to the mixing space (24, 24a, 24b), downstream of the mixing space (24, 24a, 24b) comprises a catalyst arrangement (46, 46a 46b) having at least one catalyst unit (48, 50, 52, 70, 48a, 52a, 70a, 48b, 52b, 70b) through which the fuel / combustion air mixture can flow;
characterized, in that the fuel feed arrangement (28, 34, 28a, 34a, 28b, 34b) comprises a porous evaporator arrangement (28, 28a, 28b) receiving a liquid fuel from a fuel feed line (34, 34a, 34b) and discharging fuel vapor into the mixing space (24; 24a; 24b) 28b), or and - That at least one catalyst unit (48, 50, 52, 70, 48a, 52a, 70a, 48b, 52b, 70b) comprises a grid-like carrier with catalyst material on its surface. Catalytic burner according to claim 1,
characterized in that a burner housing (12) with a peripheral wall (14) delimits a combustion chamber (44) containing at least one catalyst unit (48, 50, 52, 70), wherein a shoulder (16) of the burner housing (12) 18) having a peripheral wall (20) and a bottom wall (16) of the burner housing (12) offset in the direction of a longitudinal axis (L) arranged bottom wall (22) is provided, wherein at least a portion of the porous evaporator assembly (28) on the peripheral wall ( 20) and / or the bottom wall (22) of the projection (18) is worn. Catalytic burner according to claim 2,
characterized in that in the peripheral wall (20) of the projection (18) at least one to the combustion chamber (44) leading flow opening (42) is provided and that at least a portion of the porous evaporator assembly (28) on the peripheral wall (20) and / or Bottom wall (22) of the projection (18) is provided on a side remote from the combustion chamber (44) side. Catalytic burner according to claim 3,
characterized in that at least one flow opening (42) in one of the bottom wall (22) of the projection (18) near the peripheral wall (20) of the projection (18) is provided and / or that at least one flow opening (42) in one of Bottom wall (16) of the burner housing (12) near the region of the peripheral wall (20) of the projection (18) is provided. Catalytic burner according to claim 3 or 4,
characterized in that at least one, preferably each flow-through opening (42) in the peripheral wall (20) of the projection (18) by a catalyst unit (48) is covered. Catalytic burner according to claim 5,
characterized in that the catalyst unit (48) on one of the combustion chamber (44) facing outside of the peripheral wall (20) of the projection (18) is provided. Catalytic burner according to claim 2,
characterized in that at least a part of the porous evaporator arrangement (28) is provided on a side of the circumferential wall (20) of the projection (18) facing the peripheral wall (14) of the burner housing (12) and in that in the circumferential wall (14) of the burner housing (14). 12) in the axial extension region of the Approach (18) at least one to the mixing chamber (24) leading throughflow opening (62) is provided. Catalytic burner according to one of claims 2 to 7,
characterized in that between the peripheral wall (14) of the burner housing (12) and the peripheral wall (20) of the projection (18) formed space (54) at its from the bottom wall (16) of the burner housing (12) remote end portion at least partially a catalyst unit (48; 50) is limited. Catalytic burner according to one of claims 2 to 8,
characterized in that on the peripheral wall (14) of the burner housing (12) at least one flow aperture (56, 66) with at least one flow opening (58, 60) is provided and that at least one, preferably each flow opening (58, 60) of a catalyst unit (52, 70) is covered. Catalytic burner according to claim 9,
characterized in that an axially formed between the shoulder (18) and a flow aperture (56) space (72) by a catalyst unit (50) in a radially outer space portion (74) and a radially inner space portion (76) is divided. Catalytic burner according to claim 1,
characterized in that a burner housing (12a, 12b) with a peripheral wall (14a, 14b) delimits a combustion chamber (44a, 44b) containing at least one catalytic converter unit (58a, 52a, 70a, 48b, 52b, 70b) and that on the peripheral wall ( 14a; 14b) of the burner housing (12a; 12b) and / or a bottom wall (16a; 16b) of the burner housing (12a; 12b) at least part of the porous evaporator arrangement (28a; 28b) is provided. Catalytic burner according to claim 11,
characterized in that the porous evaporator arrangement (28a) on one of the combustion chamber (44a) facing away from the outer wall (16a) is provided and that in the peripheral wall (14a) of the burner housing (12a), preferably in one of the bottom wall (16a) approach Region, at least one to the combustion chamber (44 a) leading throughflow opening (80 a) is provided. Catalytic burner according to claim 12,
characterized in that at least one, preferably each flow-through opening (80a) is covered by a catalyst unit (48a). Catalytic burner according to claim 13,
characterized in that the catalyst unit (48a) on one of the combustion chamber (44a) facing inside of the peripheral wall (14a) of the burner housing (12a) is provided. Catalytic burner according to claim 11,
characterized in that the porous evaporator arrangement (28a) is provided on an inner side of the bottom wall (16a) of the burner housing (12a) facing the combustion chamber (44a) and in that in the circumferential wall (14a) of the burner housing (12a), preferably in one of the bottom walls (16a) near the area, at least one to the mixing chamber (24a) leading throughflow opening (80a) is provided. Catalytic burner according to claim 11,
characterized in that on the peripheral wall (12b) with a peripheral wall portion (86b) and a bottom wall portion (88b) is substantially cup-shaped or cup-shaped porous evaporator assembly (28b) is supported. Catalytic burner according to claim 16,
characterized in that a catalyst unit (48b) is provided on the porous evaporator arrangement (28b). Catalytic burner according to claim 17,
characterized in that the catalyst unit (48b) comprises catalyst material applied to the building material of the porous evaporator arrangement (28b). Catalytic burner according to one of claims 11 to 18,
characterized in that at least one flow aperture (56a, 66a, 56b, 66b) with at least one through-flow opening (58a, 68a; 58b, 68b) is provided on the circumferential wall (14a, 14b) of the burner housing (12a, 12b) and at least one , Preferably, each flow-through opening (58a, 68a, 58b, 68b) of a catalyst unit (52a, 70a, 52b, 70b) is covered. Catalytic burner according to one of claims 1 to 19,
characterized in that at least one catalyst unit (52a, 70a) is formed upstream or downstream, preferably convex, conical or cylindrical. Catalytic burner according to one of claims 1 to 20,
characterized in that the grid-like support of at least one catalyst unit (48, 50, 52, 70, 48a, 52a, 70a, 48b, 52b, 70b) for obtaining the installation form of the catalyst unit (48, 50, 52, 70, 48a, 52a, 70a, 48b, 52b, 70b) is deformed. Catalytic burner according to one of claims 1 to 21,
characterized in that an electrically energizable heating device (32; 32b) is associated with the porous evaporator arrangement (28a; 28b).

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