EP1484552A1 - Combustion chamber for a vaporizing burner, particularly for an automotive heater - Google Patents

Abstract

The combustion chamber arrangement has a combustion chamber housing (16) enclosing the combustion chamber (22) with a heating/ignition device (56), incorporated in the wall (20) of the combustion chamber housing, provided by an electric heating element and an associated heat transfer element having an ignition projection (80) extending in the direction of the combustion chamber. An independent claim for an automobile auxiliary heating device is also included.

Description

The present invention relates to a combustion chamber arrangement for a Vaporizer burner, in particular for a vehicle heater.

DE 100 20 027 A1 describes a combustion chamber arrangement for a vehicle heater known, in which in the area of a bottom wall Pot-shaped combustion chamber housing a porous evaporator medium is provided in which of the combustion air together burning liquid fuel is fed and from which this liquid fuel then evaporates towards the combustion chamber. Around increase the evaporation rate and thus the start phase of the combustion chamber to shorten this porous evaporating medium is an electrical one Excitable heating element assigned to heat this faster can and thus increase the evaporation rate. At a distance from the porous evaporator medium is a glow plug Ignition device provided that with its sufficient to generate the high temperature effective section essentially radially into the Combustion chamber protrudes. Thus, in the start-up phase at a short distance the temperatures generated above the porous evaporator medium ignite the ignitable mixture and thus the combustion in the combustion chamber can start.

It is the object of the present invention to provide a combustor assembly for an evaporator burner, in particular for a vehicle heater, to provide, which with a simple and inexpensive construction Realization of a short start phase.

According to the invention, this object is achieved by a combustion chamber arrangement for an evaporator burner, in particular for a vehicle heater, comprising a combustion chamber housing providing a combustion chamber and one in the area of a wall of the combustion chamber housing provided heating / ignition device with an electrically excitable heating element and one in heat transfer contact with the heating element Heat transfer element, wherein the heat transfer element at least one ignition projection protruding towards the combustion chamber having.

In the present invention, the electrically excitable heating element takes over two functions. On the one hand, through its excitement, it serves the To increase the evaporation rate of the fuel, on the other hand it forms together with the at least one ignition projection a local area high temperature in the combustion chamber, so that by the electrically excitable heating element provided and via the heat transfer element transported in this at least one ignition projection Heat the temperatures required for ignition are provided can. There are not two separate and also separately controllable ones Heaters required.

In order to further improve the evaporation rate in the combustion chamber it is proposed that one of the combustion chamber facing Side of the heat transfer element is a porous evaporator medium is provided and that the at least one ignition projection in a recess engages in the evaporator medium. It is also advantageous if the recess is open to the combustion chamber, so that the at least one ignition tab in direct contact with that in the combustion chamber and especially in the vicinity of the porous evaporator medium formed ignitable mixture can occur. The Effect can be further improved in that the at least one Ignition projection extends beyond the evaporator medium into the combustion chamber extends.

About the construction or assembly of a combustion chamber arrangement according to the invention very easy to design and in particular also the components in the area of the heating / ignition device Protect against excessively high temperatures caused by combustion To be able to, it is proposed that the heat transfer element on a side of the wall of the wall facing away from the combustion chamber Combustion chamber housing arranged in heat transfer contact with this and that the at least one ignition projection is one in the wall formed opening penetrates.

The heating power required to generate the high ignition temperatures with the electrically excitable heating element can also result in that the heat transfer element is heated very strongly. A very strong one or excessive heating of the heat transfer element can correspondingly strong, undesired heating of the evaporator medium have as a consequence. According to a further aspect, it is therefore proposed that between the heat transfer element and the evaporator element an intermediate element with lower thermal conductivity than that Heat transfer element is arranged. Through this intermediate element will ensure that even if the heating element is very strong is excited and generates correspondingly high temperatures in the range of effective at least one ignition lead these high temperatures can be, while in other areas, i.e. those areas in what heat from the heat transfer element into the evaporator medium is to be transported, by providing the intermediate element generated reduced heat transfer or a higher Thermal resistance is provided. That way the evaporator medium is still heated, but not so much, that damage or undesirable reactions occur. Here can an opening may also be provided in the intermediate element, which who can then enforce at least one ignition projection.

The intermediate element can have a thermal conductivity in the range from 0.1 to 0.5 W / mK, preferably about 0.3 W / mK and can consist of one Ceramic material, commonly referred to as insulating ceramic can be built.

In a particularly preferred embodiment for manufacturing reasons can be provided that the wall is a bottom wall of the Evaporator case is.

It is further proposed that the heat transfer element have a thermal conductivity or specific thermal conductivity in the range from 30 to 200 W / mK, preferably 100 to 180 W / mK. In order to be able to further provide electrical insulation of the electrically excitable heating element, for example with respect to the combustion chamber housing, which is generally made of metal, it is further proposed that the heat transfer element have a specific electrical resistance of at least 10 ¹¹ Ωcm, preferably at least 10 ¹⁴ Ωcm.

As a particularly preferred material for the heat transfer element has ceramic material, for example aluminum nitride, silicon nitride or Silicon carbide.

To improve the heat transfer from the electrically excitable heating element in the heat transfer element it is further proposed that a sink arrangement is provided in the heat transfer element in which the heating element is at least partially received. Thus, the heating element is at least in the heat transfer element embedded in areas and the heat transfer surface accordingly increased.

In order to exclude heat loss as much as possible, further suggested that the heating element between the heat transfer element and a closure element is included. Therefor it is also preferably provided that the end element is a has lower thermal conductivity than the heat transfer element. The thermal conductivity of the termination element can be in the range of 0.02 to 0.06 W / mK, preferably about 0.04 W / mK. This too End element can be formed, for example, from ceramic material.

The present invention further relates to a vehicle heater in which a combustion chamber arrangement according to the invention is provided.

Fig. 1

eine Längsschnittansicht eines Fahrzeugheizgeräts mit einer erfindungsgemäßen Brennkammeranordnung;

Fig. 2

eine Draufsicht bzw. Schnittansicht einer Heiz/Zünd-Einrichtung, geschnitten längs einer Linie II-II in Fig. 3;

Fig. 3

eine Längsschnittansicht der Heiz/Zünd-Einrichtung;

Fig. 4

eine Explosionsansicht der Heiz/Zünd-Einrichtung.

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 vehicle heater with a combustion chamber arrangement according to the invention;

Fig. 2

a plan view or sectional view of a heating / ignition device, cut along a line II-II in Fig. 3;

Fig. 3

a longitudinal sectional view of the heating / ignition device;

Fig. 4

an exploded view of the heating / ignition device.

In Fig. 1, a vehicle heater is generally designated 10. Such a thing Heater 10 can be used, for example, as an auxiliary heater or as an auxiliary heater be used in a vehicle. The heater 10 includes one Combustion chamber arrangement 12, in which, as will be described in the following, thermal energy is provided by burning a fuel / air mixture is, as well as a heat exchanger assembly 14, in which this provided for combustion and transported in the combustion exhaust gases Heat on a medidum to be heated, for example air or also that circulating in a cooling system of an internal combustion engine Coolant can be transferred.

The combustor assembly 12 includes a combustor housing, generally designated 16. This combustion chamber housing 16 is essentially pot-shaped and, with a cylindrical peripheral wall 18, for example, and a bottom wall 20, for example, integrally configured with it, defines a combustion chamber 22 which is open in the direction of the heat exchanger arrangement 14. In the embodiment shown, there are a plurality of combustion air inlet openings 24 in the peripheral wall 18 formed so that the combustion air conveyed into an air supply space 26 and symbolically indicated by the arrow P ₁ can be introduced into the combustion chamber 22. It should be pointed out that the air supply space 26 can be delimited by the combustion chamber housing 16 and an air guide housing 28 surrounding it. The combustion air is conveyed into the air supply space 26 by an air conveying fan known per se, for example radially or possibly axially, with respect to a longitudinal axis A of the combustion chamber arrangement 12.

After flowing through a flame shield 30, the combustion exhaust gases emerging from the combustion chamber 22 enter a flame tube 32 which is axially open on its side facing away from the combustion chamber 22. The flame tube 32 is surrounded by the likewise substantially pot-shaped heat exchanger arrangement 12 or an inner heat exchanger housing 34 thereof. A combustion exhaust gas flow space 36 is formed between this inner heat exchanger housing 34 and the flame tube 32, along which the combustion exhaust gases flow back towards the combustion chamber arrangement 12 and are then discharged to the environment or to an exhaust gas purification system, such as through an outlet 38 formed, for example, in the air guide housing 28 Arrow P ₂ indicated.

Between the inner heat exchanger housing 34 and an outer Heat exchanger housing 40, a flow space 42 is formed by is flowed through the medium to be heated. This occurs in the area an inlet 44 in the heat exchanger assembly 14 and exits these in the area of an outlet 46.

It should be noted that both the heat exchanger arrangement 14 as well as the combustion chamber arrangement 12, as described above have been and are shown in Fig. 1, an example of a There are a variety of different options.

A porous evaporator medium 50 is provided on a side 48 of the bottom wall 20 of the combustion chamber housing 16 facing the combustion chamber 22. This porous evaporator medium, which can be formed, for example, from foam ceramic, nonwoven material, braid material or the like, preferably covers the entire surface of the side 48 of the bottom wall 20. A through opening for a fuel line 52 is formed in the bottom wall 20, which leads directly to the evaporator medium 50, so that fuel, as indicated by an arrow P ₃ , can be introduced into the porous evaporator medium 50. It should be pointed out here that such fuel lines 52 can of course also lead to the porous evaporator medium 50 in several areas of the bottom wall 20. Furthermore, it is of course also possible to provide on the inside of the peripheral wall 18 at least partially porous evaporator medium, into which liquid fuel can then be fed either via the porous evaporator medium 50 or via separate fuel lines.

On the side 54 of the bottom wall facing away from the combustion chamber 22 20, a heater / igniter generally designated 56 is provided. As can be seen in more detail in FIGS. 2 to 4, this comprises a plate-shaped heat transfer element 58, the its side 60 facing the side 54 of the bottom wall 20 via a Intermediate element 82 with the bottom wall 20 in heat transfer contact stands and on its side 62 facing away from the bottom wall 20 has an annular or spiral depression arrangement 64. In this is an electrically designed as a heating coil or heating coil or the like excitable heating element 66 essentially recorded so that it does not protrude from the heat transfer element 58 on the side 62. The electrically excitable heating element 66 is still on the side 62 by being in contact with the heating element 58 connected cover element 68 covers, so that it essentially, except for electrical supply areas, between this cover element 68 and the heat transfer element 58 is included. The heat transfer element 58 has a substantially ring-like configuration on, and in the cover member 68 is for the or each conduit 52 there is an opening 70 also in the form of a connection piece 72, so that on the one hand the heat transfer element 58 also in the area this opening 70 through the nozzle-like section 72 of the cover element 68 is covered and on the other hand a separation between this Heat transfer element 58 and line 52 are made can. On the outer peripheral region, the cover element 68 has a cylindrical one or nozzle-like projection 74 of the heat transfer element 58 covers to the outside. Also the plate-like intermediate element 82 has one associated with the or each line 52 Opening 84, which is also designed in a substantially nozzle-like manner Approach 86 is formed. Together with the neck-like section 72 of the cover element 68 thus closes this socket 86 Heat transfer element 58 radially inward with respect to a fuel line 52 thermally.

As can be seen in FIG. 1, this results in a configuration in which the heat transfer element 58 only in heat transfer contact with the intermediate element 85 and over this and the bottom wall 20th with the porous evaporator medium 50 while both to the fuel line 52 as well as one beyond the bottom wall 20 extended portion 75 of the peripheral wall 18 of the combustion chamber housing 16 a direct contact between the heat transfer element 58 and other components is not present. The cover element 68 is preferably made of a thermally insulating material, such as. B. Ceramic material or the like, built. This ensures that in the area of the heating element 60 by electrical excitation of the same generated heat essentially completely and without major heat losses introduced into the evaporator medium 50 or the combustion chamber 22 becomes.

In order to be able to provide the desired heat transfer conditions, it is advantageous to produce the heat transfer element 58 from a material which is a good thermal conductor. Here has special ceramic material, such as. As aluminum nitride, silicon nitride or silicon carbide, proven to be particularly advantageous, which has a specific thermal conductivity that is in the range of 30 to 180 W / mK and can therefore be significantly higher than the thermal conductivity of metal material, such as. B. steel. Further, this material also has a sufficiently high electrical resistivity in the range of, for example, 10 ^{12 to} 10 ¹⁴ ohm-cm, so that equally good electrical insulation between the heating element 60 and the generally made of metal, for example aluminum or steel material combustor casing 16 produced provided is ,

It can be seen above all in FIG. 1 that in the intermediate element 82, the Bottom wall 20 of the combustion chamber housing 16 and the porous evaporator medium 50 aligned openings 88, 76, 78 are formed are. A formed on the heat transfer element 58 and over its side 60 to be positioned facing the combustion chamber 22 protruding ignition protrusion 80 penetrates at the combustion chamber housing 16 worn heater / igniter 56 these openings 88, 76, 78. The dimensions or shape of these openings 88 are preferably 76, 78 matched to the shape of the ignition projection 80 such that the ignition projection 80 neither with the intermediate element 82 nor with the Bottom wall 20 still with the porous evaporator medium 50 in direct Heat transfer contact is. Through openings 88, 76, 78 through this, the ignition protrusion 80 engages slightly in the combustion chamber 72 on. When the heating element 66 is excited by the good thermal conductivity of the heat transfer element 58 ensured that in Area of the ignition projection 78 in the combustion chamber 22 for ignition by fuel evaporation and combustion air injection formed ignitable mixture required high temperature provided becomes. It is particularly advantageous here that this ignition projection 80 extends very close to the porous evaporator medium 50 so that especially in the vicinity of this ignition projection 80 a strong atmosphere enriched with vaporized fuel can. In particular, is in the substantially annular space between the ignition protrusion 80 and the porous evaporator medium 50 such an atmosphere leading to a good ignition characteristic provided so that it is not mandatory to have the ignition tab 80 so long that it, as shown in FIG. 1 can be seen until it extends into the combustion chamber 22. Alone by stretching in in the area of the opening 78 of the porous evaporator medium 50, which opening 78 is open to the combustion chamber 22, it may be possible be, by generating locally high temperatures and providing them a favorable atmosphere for igniting the heater 10 or the burner assembly 12 of the same already after a short preheating phase ignite.

In order to be able to generate these temperatures, it may be necessary that To excite heating element 66 comparatively strongly, so that in the heat transfer element 58 not only in the area of the ignition projection 80, but also in the others for heat transfer into the porous evaporator medium 50 serving areas very high temperatures arise. To avoid having the porous evaporator medium 50 with such is exposed to high temperatures, that is already mentioned above Intermediate element 82 is provided, which ensures that in Range of a respective ignition projection 80 these high temperatures in Heat transfer element 58 can be used directly while in the other for heating the porous evaporator medium 50 serving areas by additionally inserting a thermal conductivity resistor a reduced heat transfer will take place. For this, the Intermediate element 82, for example, from a so-called insulating ceramic be built up, the thermal conductivity or specific thermal conductivity in the range of 0.3 W / mK. Such insulation materials are commercially available which are resistant to high temperatures, e.g. B. under the registered PROMAFELD 9 brand available. By inserting this intermediate element So 82 becomes the one for igniting and heating the porous Evaporator medium 50, on the other hand, required temperature gradation reached. In particular, by selecting the material or the thickness of the intermediate element 82 can be predefined here in a defined manner large the thermal conductivity in the heat transfer to the porous Evaporator medium 50 and thus what proportion of the heat in it porous evaporator medium on the one hand and the projection 80 on the other is transmitted.

It should be noted that, of course, in the invention to be provided heating / ignition device 56 a plurality of ignition projections 80 can be provided to be distributed over the area of the bottom wall 20 to provide several areas in which the ignition then occurs so that from the beginning of the combustion a very even one Distribution of the combustion in the combustion chamber 22 can be obtained can. Furthermore, the heating element 66 can be operated such that it is initially more excited at the beginning of the start phase, i.e. warmed up more in order to achieve the required high levels in the area of the ignition projection 80 To be able to provide temperatures, and then when the combustion has been started, is operated with lower heating power, so that in Essentially, only the fuel evaporation is increasingly supported if necessary. Here, for example, a conventional one Heating wire, e.g. B. Kanthal can be used, the heat output of about 250 W can provide.

The above-mentioned intermediate element 82 or whose function of the additional heat transfer barrier through the Bottom wall 20 of the combustion chamber housing 16 itself taken over if the combustion chamber housing 16 or at least the bottom wall 20 of the same is constructed from a material that has a corresponding Heat transfer barrier created. A difficult heat transfer between the heat transfer element 58 and the bottom wall 20 of the combustion chamber housing 16 can also by surface structuring in the area of at least one surface of these two components can be obtained, so that with appropriately roughened, ribbed or in otherwise structured surface the total contact area of these two components is reduced and a correspondingly reduced Heat transfer from the heat transfer element 58 to the bottom wall 20 of the combustion chamber housing 16 will be the result. It is too basically conceivable that between the heat transfer element and intermediate element provided to the porous evaporator medium, if this is not formed by the bottom wall 20 itself, between the bottom wall 20 and the porous evaporator medium 50 to arrange.

It should also be pointed out that the device to be provided according to the invention Heating / ignition device 56 can also be provided if in Area of the bottom wall 20 of the combustion chamber housing 16, a combustion air inlet connection is formed so that the combustion air in the Can flow into the combustion chamber 22 essentially radially from the inside or can additionally flow into the combustion chamber 22 from the radially inside. Furthermore, it is of course also possible to use the inventive Arrange the arrangement so that it does not or not only on the floor chamber 20 of the combustion chamber housing 16 is positioned, but for example is also positioned in the region of the peripheral wall 18. Furthermore, it is basically also conceivable to switch on the heating / ignition device the side 48 of the bottom wall 20 facing the combustion chamber 22 to provide, that is between the bottom wall 20 and the porous evaporator medium 50 if this is for reasons of improved heat transfer in the porous evaporator medium 50 is advantageous.

Claims (19)

Combustion chamber arrangement for an evaporator burner, in particular for a vehicle heater, comprising a combustion chamber (22) Providing combustion chamber housing (16) and one in the area of Wall (20) of the combustion chamber housing (16) provided Heating / ignition device (56) with an electrically excitable heating element (66) and one with the heating element (66) in heat transfer contact standing heat transfer element (58), wherein the heat transfer element (58) at least one in the direction to the combustion chamber (22) projecting ignition projection (80). Combustion chamber arrangement according to Claim 1, characterized in that a porous evaporator medium (50) is provided on a side (60) of the heat transfer element (58) facing the combustion chamber (22) and in that the at least one ignition projection (80) into a recess (78) in the evaporator medium (50) engages. Combustion chamber arrangement according to Claim 2, characterized in that the recess (78) is open towards the combustion chamber (22). Combustion chamber arrangement according to claim 3, characterized in that the at least one ignition projection (80) extends beyond the evaporator medium (50) into the combustion chamber (22). Combustion chamber arrangement according to one of claims 1 to 4, characterized in that the heat transfer element (58) is arranged on a side (54) of the wall (20) of the combustion chamber housing (16) facing away from the combustion chamber (22) and that the at least one ignition projection ( 80) passes through an opening (76) formed in the wall (20). Combustion chamber arrangement according to Claim 2 or one of Claims 3 to 5, if dependent on Claim 2, characterized in that an intermediate element (82) with a lower thermal conductivity than the heat transfer element (58) is arranged between the heat transfer element (58) and the evaporator medium (50) , Combustion chamber arrangement according to claim 6, characterized in that the at least one ignition projection (80) passes through an opening (88) in the intermediate element (82). Combustion chamber arrangement according to claim 6 or 7, characterized in that the intermediate element (82) has a thermal conductivity in the range of 0.1 to 0.5 W / mK, preferably about 0.3 W / mK. Combustion chamber arrangement according to one of claims 6 to 8, characterized in that the intermediate element (82) is formed from ceramic material. Combustion chamber arrangement according to one of claims 1 to 9, characterized in that the wall (20) is a bottom wall (20) of the combustion chamber housing (16). Combustion chamber arrangement according to one of Claims 1 to 10, characterized in that the heat transfer element (58) has a thermal conductivity in the range from 30 to 200 W / mK, preferably 100 to 180 W / mK. Combustion chamber arrangement according to one of claims 1 to 8, characterized in that the heat transfer element (58) has a specific electrical resistance of at least 10 ¹¹ Ωcm, preferably at least 10 ¹⁴ Ωcm. Combustion chamber arrangement according to one of claims 1 to 12, characterized in that the heat transfer element (58) is formed from ceramic material, preferably aluminum nitride, silicon nitride or silicon carbide. Combustion chamber arrangement according to one of Claims 1 to 13, characterized in that a depression arrangement (64) is provided in the heat transfer element (58), in which the heating element (66) is at least partially accommodated. Combustion chamber arrangement according to one of Claims 1 to 11, characterized in that the heating element (66) is enclosed between the heat transfer element (58) and an end element (68). Combustion chamber arrangement according to claim 15, characterized in that the end element (68) has a lower thermal conductivity than the heat transfer element (58). Combustion chamber arrangement according to claim 15 or 16, characterized in that the end element (68) has a thermal conductivity in the range of 0.02 to 0.06 W / mK, preferably about 0.04 W / mK. Combustion chamber arrangement according to one of claims 15 to 17, characterized in that the closure element (68) is formed from ceramic material. Vehicle heating device comprising a combustion chamber arrangement (12) according to one of the preceding claims.

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