EP1788305B1 - Combustion chamber assembly for an evaporation burner - Google Patents

Description

The present invention relates to a combustion chamber assembly for an evaporator burner, as used for example in a vehicle heater, according to the preamble of claim 1.

Such from the EP 1 363 070 A1 known combustion chamber assembly has a substantially pot-like and a combustion chamber delimiting combustion chamber housing. On a wall of this combustion chamber housing, generally a peripheral wall of the same, at least one Zündorganaufnahmeansatz is provided, which is lined on its inside with a porous evaporator medium. To be able to feed fuel into this porous evaporator medium, a Brennstoffzuführleitung opens into the Zündorganaufnahmeansatz where it is lined with the porous evaporator medium. Further, for supplying the required in particular for ignition air, such a fuel receiving approach to an air inlet opening. This lies in the end region of such a Zündorganaufnahmeansatz, which is located the connection to the wall of the combustion chamber housing.

The air required for ignition is conveyed into such an air inlet opening by a blower, which also promotes the required for the normal combustion and fed into the combustion chamber air. This means that the amount of air fed into the Zündorganaufnahmeansatz can not be adjusted independently of the in the combustion chamber itself or directly fed combustion air quantity. Therefore, in order to specify a defined quantity of ignition air, the passage cross-section of the air inlet opening provided in the Zündorganaufnahmeansatz is dimensioned so that the correct amount of ignition air is available also in relation to the fuel quantity fed in the ignition phase.

The DE 43 28 790 A1 shows a combustion chamber assembly with a pot-like combustion chamber housing. A region of the peripheral wall and a ring-like region of the bottom wall are covered by a porous evaporator medium. In the bottom wall and in the peripheral wall of the combustion chamber housing air inlet openings are provided. Air flowing through it passes through the porous evaporator medium or through openings provided in the porous evaporator medium into a combustion chamber. In an ignition member receiving lug adjacent to a peripheral wall of the combustion chamber housing, an ignition member is provided. By an opening provided in the circumferential wall of the combustion chamber housing and a corresponding opening provided in the porous evaporator medium, the internal volume of the ignition element receiving attachment to the combustion chamber is open.

The problem with such combustion chamber assemblies is that liquid fuel can reach the area in which the air passage opening is provided. Solid residues possibly formed during combustion or ignition can deposit in the region of the air inlet opening and close it more and more over the service life. The amount of heat available via an ignition element, generally a glow plug, is generally insufficient, for example, to burn off such solid residues in a cleaning phase. This is primarily due to the fact that the Zündorganaufnahmeansatz, as well as the remaining portion of the combustion chamber, is generally provided as a cast component, ie as a metal component, which provides a comparatively large thermal mass and quickly dissipates the heat input.

It is the object of the present invention to provide a combustion chamber assembly for an evaporator burner, with which it can be ensured in a simple and reliable manner that the required amount of air required for igniting air is fed At the same time, the risk of the formation of residues in the field of Zündlufteinspeisung should be reduced.

According to the invention, this object is achieved by a combustion chamber assembly for an evaporator burner, in particular for a vehicle heater, according to claim 1.

It is essential in the combustion chamber assembly according to the invention that at least one air inlet opening is not in a range in which no porous evaporator medium is present, but that the air inlet opening is basically covered by the porous evaporator medium and even in this porous evaporator medium further into the interior of the Zündorganaufnahmeansatzes Passage opening is provided. That is, even if liquid or vaporized fuel enters this area of the air feed, it will not directly contact the material of the ignition organ receiving itself, but will generally only come into contact with the porous evaporator medium. If deposits are formed in this area, it will be easily possible to burn off the same by very strong heating by means of the ignition device in the Zündorganaufnahmeansatz. On the one hand, the porous evaporator medium is closer to the ignition device. On the other hand, the thermal mass of the porous evaporator medium is significantly lower and its thermal conductivity also reduced, especially if it does not rest over its entire outer circumference on Zündorganaufnahmeansatz. The heat supplied by the ignition device can thus be used efficiently to burn off any deposits that may be formed. Furthermore, there is the advantage that at least one air inlet opening can be dimensioned arbitrarily or too large in the Zündorganaufnahmeansatz in itself, so that it is suitable for different design types of such a combustion chamber assembly. The actual inlet cross-section is defined defined by the air passage opening provided in the porous evaporator medium in association with such an air inlet opening, which has a smaller passage cross-section, as the air inlet opening assigned to it. This means that a throttle point is created by the passage opening in comparison to the passage cross section of the air inlet opening. It should nevertheless be pointed out that even if, for example, the air passage opening provided in the porous evaporator medium provides approximately the same dimension or the same passage cross-section as the air inlet opening, it is also ensured that deposits possibly generated on the inside are in the region of be located much easier to heat porous evaporator medium.

To be able to obtain a homogenization of the Zündluftzufuhr over the Zündorganaufnahmeansatz, it is proposed that in the Zündorganaufnahmeansatz more air inlet openings are provided and that at least one air passage opening is provided in association with at least one of the air inlet openings in the porous evaporator medium. Alternatively or additionally, it can be provided here that at least one air inlet opening is designed to extend in a ring-like manner over the circumference of the ignition element receiving projection, wherein preferably such an annular opening can extend at least over an angular range of 180 °.

With regard to the ignition air feed, it has proved to be particularly advantageous if the at least one Zündorganaufnahmeansatz in a first end portion in communication with the combustion chamber and when the at least one air inlet opening is formed near a second end portion of the Zündorganaufnahmeansatzes. It is advantageous if the Brennstoffzuführleitung in the Zündorganaufnahmeansatz between the first end and he opens at least one air inlet opening.

In the case of the construction according to the invention, provision can furthermore be made for the porous evaporator medium to abut against an inner surface of the Zündorganaufnahmeansatzes at least in the area surrounding the at least one air inlet opening.

In order to obtain an improved thermal decoupling of the porous evaporator medium from the building material of the Zündorganaufnahmeansatzes itself, it is proposed that the porous evaporator medium is at least in the area surrounding the at least one air inlet opening at a distance from an inner surface of the Zündorganaufnahmeansatzes.

In particular, if between the porous evaporator medium and the approach a gap is formed, an advantageous development of the invention may be characterized by a arranged after the porous evaporator medium in the Zündorganaufnahmeansatz and on an inner surface of the Zündorganaufnahmeansatzes fitting end element. In this way, an undefined inflow of the combustion air is avoided, bypassing the porous evaporator medium.

Furthermore, the combustion chamber assembly according to the invention can be constructed such that the at least one air inlet opening in the Zündorganaufnahmeansatz with respect to a longitudinal direction thereof is arranged radially.

Fig. 1

eine Querschnittsansicht einer erfindungsgemäßen Brennkammerbaugruppe;

Fig. 2

eine der Fig. 1 entsprechende Ansicht einer alternativen Ausgesaltungsform;

Fig. 3

eine der Fig. 1 entsprechende Darstellung einer nicht erfindungsgemäßen Brennkammerbaugruppe;

Fig. 4

eine Detailansicht eines Zündorganaufnahmeansatzes bei einer weiteren Ausgestaltungsform der erfindungsgemäßen Brennkammerbaugruppe.

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

Fig. 1

a cross-sectional view of a combustion chamber assembly according to the invention;

Fig. 2

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

Fig. 3

one of the Fig. 1 corresponding representation of a non-inventive combustion chamber assembly;

Fig. 4

a detailed view of a Zündorganaufnahmeansatzes in another embodiment of the combustion chamber assembly according to the invention.

In Fig. 1 10 is a combustor assembly for a vehicle heater. This illustrated in cross-section combustion chamber assembly 10 includes a combustion chamber housing 12 which is formed with an example substantially circular cylindrical peripheral wall 14 and a bottom wall 16. The bottom wall 16 may be integrally formed with the peripheral wall 14 and formed therewith to provide an integral combustor housing 12 in a manufacturing operation, generally using a casting process for manufacturing. The substantially pot-shaped combustion chamber housing 12 defines a combustion chamber 18 with its peripheral wall 14 and its bottom wall 16.

In an area preferably lying close to the bottom wall 16, an ignition element receiving lug 20 is provided on the combustion chamber housing 12, namely here the circumferential wall 14. This lateral approach is approximately tangential to the peripheral wall 14 and is preferably integrally formed with this, so also forms an integral part of the metal-made combustor 12. Also, this approach 20, based on its longitudinal direction, for example, be designed substantially circular cylindrical. Not shown is a possibly provided on the bottom wall 16 combustion air inlet nozzle, which may be formed approximately parallel to the peripheral wall 14 extending in a central region of the bottom wall 16 and projects into the combustion chamber 18 to feed combustion air into the combustion chamber 18 via a plurality of slot-like openings formed therein ,

On the inside of the peripheral wall 14, a porous evaporator medium 22 is provided. This preferably dresses the peripheral wall 14 in its entire peripheral region and approximately in the entire extension region of the combustion chamber 18 from. This porous evaporator medium 22 can receive liquid fuel, distribute it by Kapillarförderwirkung in its internal volume range and then evaporate at the surface exposed to the combustion chamber 18 toward.

Also on the inside of the Zündorganaufnahmeansatzes 20, a porous evaporator medium 24 is provided, which is where the projection 20 in its first end portion 26 connects to the peripheral wall 14, in contact with the porous evaporator medium 22. In the approach 20 further opens a fuel supply 28, in a region in which the projection 20 is lined with the porous evaporator medium 24. Liquid fuel is thus fed via the line 28 into the batch 20 and there into the porous evaporator medium 24. Also, the evaporator medium 24 provides a Kapillarfördereffekt so that it on the one hand distributed from the line 28 liquid fuel in its interior volume range and thus distributed over the circumference of the neck 20, on the other hand, but also due to the connection to the porous evaporator medium 22 in the combustion chamber 18 fuel in this porous evaporator medium 22 introduces further distribution therein and for evaporation in the combustion chamber 18th

At its second end region 30, the projection 20 is closed by a closure element 32. An ignition member 34, such as a glow plug, is carried on this closure member 32 or a separate carrier and extends approximately centrally into the boss 20. Via a connecting line 36, the ignition device 34 can be energized, so that by heating the same in the region of the projection 20 so high temperatures can be generated that a mixture contained therein of evaporated fuel and air can be ignited and thus the combustion in the combustion chamber housing 12 are started can.

As previously stated, the time required for normal combustion Air fed directly into the combustion chamber 1B. However, the air required for the ignition, in particular in the inner region of the projection 20, is fed directly into this Zündorganaufnahmeansatz 20. For this purpose, this has at the second end portion 30 in the in Fig. 1 illustrated embodiment, an air inlet opening 38. One recognizes in the Fig. 1 clearly that the air inlet opening 38 is positioned there on the projection 20, where it is still lined on its inside with the porous evaporator medium 24. That is, the evaporator medium 24 extends from the first end portion 26 and thus the connection to the porous evaporator medium 22 substantially over the entire length of the projection 20 to the second end portion 30 and so far that the air inlet opening 38 is basically still detected or is covered. Where the air inlet opening 38 is formed in the projection 20, an air passage opening 40 is also provided in the porous evaporator medium 24. The air required to ignite the fuel vaporized via the porous evaporator medium 24 into the interior volume region of the projection 20 can thus pass through the air inlet opening 38 and the air passage opening 40 into the projection 20, where it mixes with the fuel vapor in the region surrounding the ignition element 34 and then be ignited upon excitation of the ignition device 34. The resulting flame or combustion will then extend or spread over an opening 42 in the porous evaporator medium 22 into the region of the combustion chamber 18 and also lead there to the start of the combustion.

Since at the in Fig. 1 illustrated inventive construction of a combustion chamber assembly 10 provided in the approach 20 air inlet opening 38 is covered to the interior of the neck 20 out, so is not exposed, and thus the air required for ignition must first pass through an opening provided in the porous evaporator medium 24 through opening 40 result For the operation of a equipped with such a combustion chamber assembly 10 evaporator burner various advantages. Thus, initially the combustion chamber housing 12 with the peripheral wall 14, the bottom wall 16, possibly on the bottom wall 16 an air inlet nozzle and with the Zündorganaufnahmeansatz 20 are provided with the therein provided air inlet opening with a standardized size. That is, for different power levels or different types of construction, it is not necessary to differentiate at the air inlet opening 38. This can be formed with such a passage cross section that sufficient combustion air can occur for all intended types. The limitation on the amount of ignition air actually to be made for a particular intended type is realized by the size selection for the passage opening 40 in the porous evaporator medium 24. Thus, in this structure, a high flexibility in the specification or adjustment of the amount of ignition air, taking into account the fact that the ignition air is conveyed together with the combustion air by the same blower.

A modified embodiment is in Fig. 2 shown. The basic structure of the combustion chamber assembly 10 and the combustion chamber housing 12 corresponds to the above-described. A difference exists insofar as the air inlet opening 38 is formed here not more than, for example, circular radial opening in the wall of the Zündorganaufnahmeansatzes 20, but as a extending over a larger peripheral area annular gap-like opening. In order to ensure that the second end portion 30 of the lug 20 is also connected to the combustion chamber housing 12, a connection region 44 extending between the peripheral wall 14 and the lug 20 can be provided, which extends approximately over the entire length of the lug 20 extends and may also form an integral part of the housing 12. In the area of this section 44, the opening 38 may be interrupted in the circumferential direction. However, the opening 38 extends over a peripheral region of at least 180 °, preferably almost 360 °, with the result that even in the positioning of the air passage opening 44 in the circumferential direction or a plurality of such air passage openings 44 greater freedom exists.

One of the principles of embodiments of the Fig. 1 and 2 merging embodiment could provide over the circumference, possibly also distributed in the longitudinal direction of the projection 20 to provide a plurality of discrete air inlet openings 38. Depending on the amount of ignition air required, one or more air passage openings 40 can then be provided in the porous evaporator medium 24 in association with one, several or all such openings 38.

In Fig. 3 a non-inventive combustion chamber assembly 10 is shown. This basically corresponds to the structure of Fig. 2 , However, has the difference that where in the projection 20 of the air inlet opening 38 is formed in the porous evaporator medium 24, no air passage opening is present. That is, the porous evaporator medium 24, which thus completely covers or closes the air passage opening 38, allows the air passage due to its porosity. Here, therefore, the total passage cross-section is essentially defined by the opening size of the air inlet opening 38. In this air passage cross-section, the air can then pass through the pores of the porous evaporator medium 24 into the interior region of the Zündorganaufnahmeansatzes 20 under the conveying effect of the air supply blower provided for this purpose and thus constructed. Since the throttling effect of the porous evaporator medium 24 is known, it is easy, taking account of its porosity, to design the size of the opening 38 so that the desired amount of ignition air can flow into the projection 20 at the intended delivery capacity of the air blower.

It goes without saying that this embodiment can also be combined with the in Fig. 1 illustrated embodiment. That is, even a plurality of discrete air inlet openings 38 can each be completely covered with the porous evaporator medium 24. It is also possible to combine these two variants, so that, for example, a part of the air inlet openings 38 is completely covered with the porous evaporator medium 24, while in association with another Part of an opening 40 is present, as in the Fig. 1 and 2 is recognizable.

In the embodiments described above, the porous evaporator medium 24 abuts against an inner surface 46 of the Zündorganaufnahmeansatzes 20 at least in the area surrounding the air inlet opening 38. This has the consequence that there is no space between the porous evaporator medium 24 and the Zündorganaufnahmeansatz 20, in particular in the region of the air inlet opening 38. That is, the air conveyed through the air inlet opening 38 forcibly there either by a passage opening 40 and / or through the Pores of the porous evaporator medium 24 must pass.

In Fig. 4 an embodiment is shown in which between the inner surface 46 of the Zündorganaufnahmeansatzes 20 and the porous evaporator medium 24, a ring-like gap 48 is formed, at least in that area which is close to the second end portion of the projection 20 or where the air inlet opening 38 is provided , Thus, the air passing through this air inlet opening 38 can also reach the intermediate space 48. To ensure that in this embodiment, too, this air has to pass through the air passage opening 40 and / or the pores of the porous evaporator medium 24, a closing element 52 is provided adjacent to the end region 50 of the porous evaporator medium 24 located in the second end region 30 of the projection 20. This may for example be formed integrally with the closure element 32 and may, for example or alternatively, be effective as a carrier of the ignition device 34. The end element 52 abuts on the one hand with its outer circumference on the inner surface 46 of the projection 20, and on the other hand with an end face, ie an oriented in the longitudinal direction of the projection 20 surface at the end portion 50 of the porous evaporator medium 24 at. Thus, the gap 48 is closed toward the end portion 30, so that no leading to undefined flow conditions Bypassströmungsweg is created. It It is ensured that even with the positioning of the air inlet opening 38 shown in the figures, regardless of their dimensions, in the radial orientation with respect to the longitudinal extent of the projection 20, the air must also flow through defined by the then still radially inner porous evaporator medium 24.

The provision of such a gap 48 has the advantage that the thermal contact of the porous evaporator medium 24 is reduced with the projection 20 and thus the heat loss towards the approach 20 is reduced both in the ignition phase, as well as the annealing of deposits. Furthermore, there is the advantage that the air introduced through the air inlet opening 38, especially at the in Fig. 3 illustrated embodiment variant of the porous evaporator medium 24 can be distributed over the entire space 48 and thus can pass through a much larger area of the porous evaporator medium 24 through this. Thus, even with a fine-pored configuration of the porous evaporator medium 24 due to the larger passage area of the throttle effect can be compensated.

Claims (10)

1. Combustion chamber assembly for an evaporation burner, in particular a vehicle heating device, comprising a substantially pot-like combustion chamber housing (12) defining a combustion chamber (18), at least one ignition member receiving piece (20) at a wall (14) of the combustion chamber housing (12) where an ignition member (34) extends and where at least one air entry opening (38) is provided, a porous evaporator medium (24) being provided at an inner side of the ignition member receiving piece (20) surrounding the ignition member (34) and a fuel supply line (25) for inserting liquid fuel into the porous evaporator medium (24) leading into the ignition member receiving piece (20),
   characterized by the at least one air entry opening (38) being provided in the ignition member receiving piece (20) in an area covered by the porous evaporator medium (24) and being at least partly covered by the porous evaporator medium (24), by at least one air passage opening (40) being provided in the porous evaporator medium (24) in the area of at least one air entry opening (38) and by said air passage opening (40) having a smaller passage cross-section than the associated air entry opening (38).
2. Combustion chamber assembly according to claim 1,
   characterized by several air entry openings (38) being provided in the ignition member receiving piece (20) and at least one air passage opening (40) being provided in the porous evaporator medium (24) in association to at least one of the air entry openings (38).
3. Combustion chamber assembly according to one of claims 1 to 2, characterized by at least one air entry opening (38) being formed extending annularly across the circumference of the ignition member receiving piece (20).
4. Combustion chamber assembly according to claim 3,
   characterized in that the air entry opening (38) which extends annularly across the circumference extends across an angular area of at least 180°.
5. Combustion chamber assembly according to one of claims 1 to 4,
   characterized by the at least one ignition member receiving piece (20) being in a first end section (26) associated to the combustion chamber (18) and by the at least one air entry opening (38) being formed near a second end section (30) of the ignition member receiving piece (20).
6. Combustion chamber assembly according to claim 5,
   characterized by the fuel supply line (28) leading into the ignition member receiving piece (20) between the first end section (26) and the at least one air entry opening (38).
7. Combustion chamber assembly according to one of claims 1 to 6,
   characterized by the porous evaporator medium (24) abutting, at least in the area surrounding the at least one air entry opening (38), on an inner surface (46) of the ignition member receiving piece (20).
8. Combustion chamber assembly according to one of claims 1 to 7,
   characterized by the porous evaporator medium (24) being, at least in the area surrounding the at least one air entry opening (38), spaced from an inner surface (46) of the ignition member receiving piece (20).
9. Combustion chamber assembly according to one of claims 1 to 8,
   characterized by an end member (52) which is arranged adjacent to the porous evaporator medium (24) in the ignition member receiving piece (20) and abuts on an inner surface (46) of the ignition member receiving piece (20).
10. Combustion chamber assembly according to one of claims 1 to 9,
    characterized by the at least one air entry opening (38) being arranged radially in the ignition member receiving piece (20) in relation to a longitudinal extension direction.

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