CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority of German patent application no. 10 2023 106 734.6, filed Mar. 17, 2023, the entire content of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a combustion chamber subassembly for a vaporizing burner which may be used particularly in a fuel-operated vehicle heating device.

BACKGROUND

Such a combustion chamber subassembly for a vaporizing burner of a fuel-operated vehicle heating device is known from US2015/0102115. This combustion chamber subassembly comprises a combustion chamber housing having a circumferential wall which extends in the direction of a longitudinal housing axis and having a combustion chamber base which axially delimits a combustion chamber. A base wall of the combustion chamber base provides at the side thereof facing the combustion chamber a vaporizing medium abutment face which extends substantially orthogonally to the longitudinal housing axis and at which a substantially planar porous vaporizing medium which is orientated with the side thereof facing the combustion chamber substantially orthogonally to the longitudinal housing axis is arranged. In a radially central region, there opens into the base wall a fuel supply line, via which fluid fuel is fed into the porous vaporizing medium.

DE 10 2012 111 289 B3 discloses a combustion chamber subassembly for a vaporizing burner of a fuel-operated vehicle heating device, wherein, in order to achieve improved abutment of a porous vaporizing medium, which is particularly formed from several layers, against a base wall of a combustion chamber base, the base wall is curved in a convex manner with respect to a combustion chamber which is axially delimited by the combustion chamber base in the direction of a longitudinal housing axis. The in principle disk-like or planar, porous vaporizing medium in its basic state is retained in the radially outer region thereof against the radially outer region of the base wall which is convex-curved with respect to the combustion chamber so that the porous vaporizing medium also takes up a configuration which is convex-curved with respect to the combustion chamber and consequently particularly also in the radially central region thereof is increasingly pressed against the convex-curved vaporizing medium abutment face of the base wall.

SUMMARY

An object of the present disclosure is to provide a combustion chamber subassembly for a vaporizing burner, in particular for a fuel-operated vehicle heating device, with which an improved combustion behavior is achieved.

This object is achieved according to the disclosure by a combustion chamber subassembly for a vaporizing burner, in particular for a fuel-operated vehicle heating device, including a combustion chamber housing having a circumferential wall which extends in the direction of a longitudinal housing axis and which surrounds a combustion chamber in a radially outward direction, and having a combustion chamber base which delimits the combustion chamber in an axial direction, wherein porous vaporizing medium is provided at a side, facing the combustion chamber, of the combustion chamber base, characterized in that the porous vaporizing medium is concave-curved with respect to the combustion chamber at the side thereof facing the combustion chamber.

The concave-curved structure of the porous vaporizing medium at the side thereof facing the combustion chamber combines different aspects which positively influence the combustion behavior. On the one hand, no corner regions or volume regions or corner regions or volume regions which are less powerfully pronounced are produced in the radially outer region in the transition from the combustion chamber base to the circumferential wall, which regions form during the combustion operation dead spaces in which an excessively high fuel concentration which impairs the combustion and which supports the production of deposits occurs. On the other hand, such a combustion chamber subassembly is particularly suitable for such installation of a vehicle heating device, which is provided therewith, in a vehicle in which the concave-curved side, which faces the combustion chamber, of the porous vaporizing medium is orientated vertically downward. The concave-curved structure results in regions, which are located radially further outward, of the porous vaporizing medium being located in a lower position in a vertical direction or providing the lowest regions of the porous vaporizing medium so that a distribution, which is supported by gravitational force and is more uniform, of the fluid fuel which is supplied to the porous vaporizing medium is also achieved in the radially outer regions thereof.

In order to be able to provide the effect of a uniform fuel distribution in a radially outward direction in a particularly efficient manner, it is proposed that the porous vaporizing medium be concave-curved with respect to the combustion chamber and/or that the porous vaporizing medium have a substantially constant thickness.

In a radially central region, a fuel supply line can open in the combustion chamber base and the porous vaporizing medium may have in this instance a curvature apex in the radially central region. The distribution of the fluid fuel inside the porous vaporizing medium can then, starting from the curvature apex thereof, be carried out substantially uniformly in a radially outward direction.

In order to avoid the production of intermediate spaces, which impair a uniform fuel distribution, between the porous vaporizing medium and the combustion chamber base, it is proposed that the combustion chamber base have, at the side thereof facing the combustion chamber, a vaporizing medium abutment face which is concave-curved with respect to the combustion chamber.

In this case, it is particularly advantageous if a curvature geometry of the vaporizing medium abutment face substantially corresponds to a curvature geometry of the porous vaporizing medium at the side thereof facing the combustion chamber.

In order to support the porous vaporizing medium, the combustion chamber base may comprise a base wall which provides at least a portion of the vaporizing medium abutment face.

In an embodiment which is structurally particularly easy to implement, the base wall may provide substantially the entire vaporizing medium abutment face.

In order to achieve a rapid and uniform distribution of fluid fuel, including in the radially outer regions of the porous vaporizing medium, it is proposed that the base wall comprise a recess which is open toward a side, which faces the combustion chamber, of the base wall, for receiving a porous distribution medium, wherein a first portion of the vaporizing medium abutment face is provided on the base wall and a second portion of the vaporizing medium abutment face is provided on the porous distribution medium.

Particularly when the fluid fuel is fed into the porous vaporizing medium in a radially central region, it is particularly advantageous for uniform fuel distribution if the first portion of the vaporizing medium abutment face annularly surrounds the second portion of the vaporizing medium abutment face and/or if the porous distribution medium is arranged in a substantially centered manner with respect to the longitudinal housing axis. In order to distribute the fluid fuel via the porous distribution medium as quickly as possible in a radially outward direction, it is proposed that the porous distribution medium have a greater porosity than the porous vaporizing medium.

The porous distribution medium may be curved at the side thereof facing away from the vaporizing medium abutment face, wherein a curvature geometry of the porous distribution medium at the side thereof facing away from the vaporizing medium abutment face substantially corresponds to a curvature geometry of the porous distribution medium in the second portion of the vaporizing medium abutment face and/or the porous distribution medium has a substantially constant thickness.

In an embodiment which even more powerfully supports the efficient conveying of fluid fuel in a radially outward direction, it is proposed that the porous distribution medium extend substantially orthogonally relative to the longitudinal housing axis at the side thereof, facing away from the vaporizing medium abutment face and/or the porous distribution medium have a thickness which increases in a radially outward direction. This means that the face, through which fluid fuel radially flows, of the porous distribution medium increases in a radially outward direction not only as a result of the increasing spacing from the housing axis but also as a result of the increasing thickness of the porous vaporizing medium.

In order to avoid heat losses, insulation material may be arranged at a side, facing away from the vaporizing medium abutment face, of the base wall.

For defined positioning of the porous vaporizing medium, it is proposed that it be fixed at the outer circumference thereof with respect to the combustion chamber base.

To this end, the combustion chamber base may comprise a retention element which annularly surrounds the base wall, wherein the retention element comprises at least one retention projection which retains the porous vaporizing medium against the base wall at the side thereof facing the combustion chamber.

The disclosure further relates to a fuel-operated vehicle heating device including a burner area having a combustion chamber subassembly which is configured according to the disclosure.

BRIEF DESCRIPTION OF DRAWINGS

The invention will now be described with reference to the drawings wherein:

FIG. 1 shows a longitudinally sectioned view of a combustion chamber subassembly for a combustion burner for a fuel-operated vehicle heating device;

FIG. 2 shows an illustration, corresponding to FIG. 1, of an alternative embodiment of a combustion chamber subassembly;

FIG. 3 shows an illustration, corresponding to FIG. 1, of an alternative embodiment of a combustion chamber subassembly; and,

FIG. 4 shows an illustration, corresponding to FIG. 1, of an alternative embodiment of a combustion chamber subassembly.

DETAILED DESCRIPTION

The combustion chamber subassembly 10 illustrated in FIG. 1 as a longitudinal section comprises a, for example, substantially cylindrically formed circumferential wall 12, which extends in the direction of a longitudinal housing axis L, of a combustion chamber housing 14. In an axial region which is not illustrated in FIG. 1, a flame shield may be provided at the inner side of the circumferential wall 12. In a state adjoining such a flame shield, the circumferential wall 12 may merge into a flame tube or be connected to a flame tube which is in the form of a separate component.

In an axial end region, which is illustrated in FIG. 1, of the circumferential wall 12, a combustion chamber base which is generally designated 16 is provided. The combustion chamber base 16 delimits a combustion chamber 18, which is surrounded by the circumferential wall 12 in a radially outward direction, in the direction of the longitudinal housing axis L.

The combustion chamber base 16 comprises a base wall 20, in the radially central region 22 of which with respect to the longitudinal housing axis L, a fuel supply line 24 opens in order to supply fluid fuel. At a side 26, which faces the combustion chamber 18, the base wall 20 of the combustion chamber base 16 provides a vaporizing medium abutment face 28 which is curved in a concave manner with respect to the combustion chamber 18.

At the vaporizing medium abutment face 28, which is curved in a concave manner with respect to the combustion chamber 18, of the base wall 20, a porous vaporizing medium 30 is supported in the direction of the longitudinal housing axis L. The porous vaporizing medium 30 may be formed, for example, with wire material, in particular wire mesh, knitted wires, braided wires, or the like, and may have such a porosity that fluid fuel which is introduced in the central region 20 out of the fuel supply line 24 into the porous vaporizing medium 30 is also distributed, as a result of capillary conveying action, in the inner volume of the porous vaporizing medium 30 and is discharged from the porous vaporizing medium 30 in vapor form at a side (32), which faces the combustion chamber 18, of the porous vaporizing medium 30.

The porous vaporizing medium 30 which is illustrated in FIG. 1 has, for example, in all circumferential regions and all radial regions substantially the same thickness d. This results in the porous vaporizing medium per se and particularly at the side 32 thereof facing the combustion chamber 18 also being curved in a concave manner, wherein, as a result of the substantially constant thickness d, a curvature geometry of the porous vaporizing medium 30 at the side thereof facing the combustion chamber 18 substantially corresponds to a curvature geometry of the vaporizing medium abutment face 28 at the side 26, which faces the combustion chamber 18, of the combustion chamber base 20.

In order to retain the porous vaporizing medium 30 in a defined manner in abutment against the vaporizing medium abutment face 28, a retention element 34 which annularly surrounds the base wall 20 is provided at the radially outer region of the combustion chamber base 16. This retention element 34 may, for example, be positioned between an outer circumferential region of the base wall 20 and the axial end region of the circumferential wall 12 and may be stably connected to the circumferential wall 12 or the base wall 20 by material engagement, for example, welding or soldering. In several regions, which are located with circumferential spacing from each other, the retention element 34 has retention projections 36 which are bent radially inwardly and toward the side 32, facing the combustion chamber 18, of the porous vaporization medium 30 and which abut against the side 32, facing the combustion chamber 18, of the porous vaporization medium 30 in the radial outer region thereof, and consequently retain it stably against the concave-curved vaporization medium abutment face 28.

In order in this configuration to achieve a defined abutment of the porous vaporization medium 30 against the vaporization medium abutment face 28 of the base wall 20, for example, there may be provision for, in a basic state, in which the porous vaporization medium 30 is not retained by the retention projections 36 against the base wall 20, the porous vaporization medium 30 to have a curvature geometry with a more powerful curvature than the curvature of the vaporization medium abutment face 28. During assembly, the porous vaporization medium 30 then initially moves into abutment with the central region thereof against the base wall 20 and is then also pressed in the radially outer region thereof against the base wall 20 by the retention action of the retention element 34. It is thereby particularly ensured that in the radially inner region, that is, in the central region 22 of the combustion chamber base 16, at locations where the fluid fuel is supplied, the porous vaporization medium 30 is retained stably in abutment against the vaporization medium abutment face 28 without any risk that an intermediate space between it and the base wall 20 may be produced.

As a result of the concave curvature of the porous vaporization medium 30, it is possible for a curvature apex 38, which is located in the central region 22 of the combustion chamber base 16, of the porous vaporization medium 30 to form the region, which is set back in the direction of the longitudinal housing axis L furthest away with respect to the combustion chamber 18, of the combustion chamber base 16 or the porous vaporization medium 30. Radially further outwardly located regions of the porous vaporization medium 30 are then located in the exhaust gas flow direction further forward and are particularly located nearer combustion air inlet openings 40 which are provided to introduce combustion air in the circumferential wall 12. This results in no dead spaces, in which an excessively high fuel concentration may occur and the risk of the occurrence of deposits is particularly pronounced, being present particularly in the radially outer region in the transition from the combustion chamber base 16 to the circumferential wall 12. Furthermore, the concave curvature geometry of the porous vaporization medium 30 results, when a vehicle heating device which has the combustion chamber subassembly 10 is fitted in such a manner, in the side 32, facing the combustion chamber 18, of the porous vaporization medium 30 being directed downwardly in a vertical direction or obliquely downwardly, in the vertical direction the radially outer regions of the porous vaporization medium 30 being located in a lower position than the curvature apex 38, in the region of which the fluid fuel is also supplied to the porous vaporization medium 30. Consequently, a more uniform distribution, which is supported by gravitational force, of the fluid fuel, which is introduced in the region of the curvature apex 38 into the porous vaporization medium 30, occurs in a radially outward direction. In conjunction with the increased surface-area, which is available for vaporization in comparison with a planar, non-curved structure of a porous vaporization medium, of the concave-curved porous vaporization medium 30, this leads to a particularly efficient discharge, which is uniform over the entire porous vaporization medium 30, of vaporized fuel into the combustion chamber 18.

A modified embodiment of the combustion chamber subassembly 10 is illustrated in FIG. 2. In this embodiment, there is formed in the base wall 20 of the combustion chamber base 16 a recess 42 which is open at a side 47, facing the combustion chamber 18, of the base wall 20 in the direction toward the combustion chamber 18 and in which a porous distribution medium 44 is received. In this embodiment, a first portion 46 of the vaporization medium abutment face 28 is formed on the base wall 20 and a second portion 48 of the vaporization medium abutment face 28 is formed on the porous distribution medium 44 in a state surrounded by the first portion 46 of the vaporization medium abutment face 28. In this vaporization medium abutment face 28 which is provided with the two portions 46, 48, this face has at the side 26 thereof facing the combustion chamber 18 the structure which is curved in a concave manner with respect to the combustion chamber 18.

The porous distribution medium 44 is positioned in the central region 22 of the combustion chamber base 16 so that the fluid fuel, which is supplied via the fuel supply line 24, is initially introduced into the porous distribution medium 44 and is also distributed radially outwardly in the volume thereof. The fluid fuel is then introduced in a radial direction in a state more uniformly distributed or distributed over a greater surface-area into the porous vaporization medium 30 which is supported on the second portion 48 of the vaporization medium abutment face 28 and is then distributed in the volume thereof further in a radially outward direction by capillary conveying effect and, as set out above, also in a manner supported by gravitational force.

In order to achieve a rapid and efficient radial pre-distribution of the fluid fuel as a result of the porous distribution medium 44, it preferably has a greater porosity than the porous vaporization medium 30. This means that in the porous distribution medium 44 initially a very rapid and slightly more coarse pre-distribution takes place while, in the porous vaporization medium 30 which is formed with a finer pore structure, a very uniform distribution of the fluid fuel and consequently also a very uniform discharge of the fuel in the direction toward the combustion chamber 18 are then provided.

In the embodiment illustrated in FIG. 2, the porous distribution medium 44 as a whole is formed in a curved manner and consequently has substantially in all circumferential regions and all radial regions the same thickness D. This means that, in such a structure, the fluid fuel which is distributed in a radially outward direction in the porous distribution medium 44 flows through a greater surface-area of the porous distribution medium 44 in a radially outward direction as a result of the increasing spacing from the longitudinal housing axis L.

In order to configure the distribution effect of the porous distribution medium even more efficiently in a radially outward direction, as shown in the embodiment illustrated in FIG. 3, the thickness D of the porous distribution medium 44 may increase in a radially outward direction so that the increasing thickness D, that is, the increasing axial extent of the porous distribution medium 44, also contributes to an increase of the surface-area, through which fuel flows and which is available for fuel distribution, of the porous distribution medium 44 in a radially outward direction. To this end, as FIG. 3 shows, for example, the porous distribution medium 44 may be orientated substantially orthogonally at the side 50 thereof, which faces away from the combustion chamber 18 or also the vaporization medium abutment face 28, relative to the longitudinal housing axis L and can consequently be formed in a substantially planar manner.

FIG. 4 shows an embodiment, in which there is formed at a side 52, facing away from the combustion chamber 18, of the base wall 20 of the combustion chamber base 16 a recess 54 in which insulation material 56 is received. The insulation material 56 may, for example, be foamed material which has a lower thermal conductivity than air and particularly also a lower thermal conductivity than the construction material of the base wall 20. The recess 44 can be closed by a cover 58 so that the insulation material 56 is retained stably in the recess 54. Consequently, a heat loss at the side 52, which faces away from the combustion chamber 18, of the base wall 20 to a volume region, in which generally the comparatively cold combustion air which is supplied by a combustion air fan, is minimized.

With the construction (illustrated in the figures) of a combustion chamber subassembly with the concave-curved structure of the porous vaporization medium, particularly at the side thereof facing the combustion chamber, not only are the aspects already discussed above with respect to an efficient distribution of fuel in a radially outward direction and avoiding dead spaces achieved, but it is also possible for a spacing of the side, facing the combustion chamber, of the porous vaporization medium from an ignition member, for example glow plug, which generally extends radially inwardly only with a small axial spacing from the combustion chamber base from the circumferential wall, to increase in a radially inward direction. Consequently, the risk that, with the curved structure of the porous vaporization medium, regions in which the porous vaporization medium may become locally overheated are produced is avoided. This also prevents any risk of a thermal destruction of the porous vaporization medium over the operating service-life.

It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.