Combustion chamber assembly for an evaporator burner

Abstract

A combustion chamber assembly for a vaporizer burner, in particular for a fuel-operated vehicle heater, comprising a combustion chamber housing (14) with a circumferential wall (12) extending in the direction of a longitudinal axis (L) of the housing and radially outwardly defining a combustion chamber (18), and a combustion chamber floor (16) defining the combustion chamber (18) in the axial direction, wherein a porous vaporizer medium (30) is provided on a side (26) of the combustion chamber floor (16) facing the combustion chamber (18), characterized in that the porous vaporizer medium (30) is concavely curved on its side (32) facing the combustion chamber (18) with respect to the combustion chamber (18).

Description

[0001] The present invention relates to a combustion chamber assembly for a vaporizer burner, which can be used in particular in a fuel-operated vehicle heater.

[0002] Such a combustion chamber assembly for a vaporizer burner of a fuel-operated vehicle heater is known from DE 10 2013 220 654 A1. This combustion chamber assembly comprises a combustion chamber housing with a circumferential wall extending in the direction of a longitudinal axis of the housing and with a combustion chamber base axially delimiting the combustion chamber. A base wall of the combustion chamber base provides, on its side facing the combustion chamber, a vaporizer medium surface extending substantially orthogonally to the longitudinal axis of the housing. A substantially planar porous vaporizer medium, oriented with its side facing the combustion chamber substantially orthogonally to the longitudinal axis of the housing, is arranged on this surface. A fuel supply line opens into the base wall in a radially central area, through which liquid fuel is fed into the porous vaporizer medium.

[0003] From DE 10 2012 111 289 B3, a combustion chamber assembly for a vaporizer burner of a fuel-operated vehicle heater is known, in which, to achieve improved contact of a porous vaporizer medium, particularly one consisting of several layers, against a bottom wall of a combustion chamber, the bottom wall is convexly curved with respect to a combustion chamber axially bounded by the combustion chamber bottom in the direction of a longitudinal axis of the housing. The porous vaporizer medium, which in its basic state is fundamentally disk-shaped or planar, is held in its radially outer region against the radially outer region of the bottom wall, which is convexly curved with respect to the combustion chamber, so that the porous vaporizer medium also assumes a convexly curved configuration with respect to the combustion chamber and is thus pressed more strongly against the convexly curved vaporizer medium contact surface of the bottom wall, particularly in its radially central region.

[0004] The object of the present invention is to provide a combustion chamber assembly for a vaporizer burner, in particular for a fuel-operated vehicle heater, with which improved combustion behavior is achieved.

[0005] According to the invention, this problem is solved by a combustion chamber assembly for an evaporator burner, in particular for a fuel-operated vehicle heater, comprising a combustion chamber housing with a circumferential wall extending in the direction of a longitudinal axis of the housing and radially outwardly defining a combustion chamber, and a combustion chamber floor defining the combustion chamber in the axial direction, wherein porous evaporator medium is provided on a side of the combustion chamber floor facing the combustion chamber, characterized in that the porous evaporator medium is concavely curved on its side facing the combustion chamber with respect to the combustion chamber.

[0006] The concave structure of the porous evaporator medium on its combustion chamber-facing side combines various aspects that positively influence combustion behavior. Firstly, in the radially outer area, there are no, or less pronounced, corner areas or volume zones at the transition from the combustion chamber floor to the perimeter wall. These areas, which form dead spaces during combustion, can lead to excessively high fuel concentrations that impair combustion and promote deposit formation. Secondly, such a combustion chamber assembly is particularly suitable for installing a vehicle heater equipped with it in a vehicle where the concave side of the porous evaporator medium facing the combustion chamber is oriented vertically downwards.The concave curved structure results in radially outer areas of the porous evaporator medium being located further down in the vertical direction, or rather, the lowest areas of the porous evaporator medium being provided, so that a gravity-assisted, more uniform distribution of the liquid fuel fed into the porous evaporator medium is achieved even in the radially outer areas of the same.

[0007] In order to provide the effect of a uniform fuel distribution radially outwards particularly efficiently, it is proposed that the porous evaporator medium be concave with respect to the combustion chamber, and / or that the porous evaporator medium have an essentially constant thickness.

[0008] In a radially central area, a fuel supply line can open into the combustion chamber floor, and the porous vaporizing medium can have a bulge crest in this radially central area. The distribution of the liquid fuel inside the porous vaporizing medium can then proceed essentially uniformly from the bulge crest outwards.

[0009] To avoid the formation of gaps between the porous evaporator medium and the combustion chamber floor that impair uniform fuel distribution, it is proposed that the combustion chamber floor have an evaporator medium system surface that is concave with respect to the combustion chamber on its side facing the combustion chamber.

[0010] It is particularly advantageous if the curvature geometry of the evaporator medium system surface essentially corresponds to the curvature geometry of the porous evaporator medium on its side facing the combustion chamber.

[0011] To support the porous evaporator medium, the combustion chamber floor can include a floor wall that provides at least part of the evaporator medium system area.

[0012] With a design that is particularly easy to implement from a structural point of view, the floor wall can essentially provide the entire surface area for the evaporator medium system.

[0013] To achieve a rapid and uniform distribution of liquid fuel even in the radially outer areas of the porous evaporator medium, it is proposed that the bottom wall include a recess open to one side of the bottom wall facing the combustion chamber for receiving a porous distribution medium, wherein a first part of the evaporator medium system area is provided on the bottom wall and a second part of the evaporator medium system area is provided on the porous distribution medium.

[0014] Particularly when the liquid fuel is fed into the porous evaporator medium in a radially central area, it is especially advantageous for uniform fuel distribution if the first part of the evaporator medium surface area surrounds the second part of the evaporator medium surface area in a ring-like fashion and / or the porous distribution medium is arranged essentially centered with respect to the longitudinal axis of the housing. To distribute the liquid fuel radially outwards as quickly as possible via the porous distribution medium, it is proposed that the porous distribution medium have a higher porosity than the porous evaporator medium.

[0015] The porous distribution medium can be convex on its side facing away from the evaporator medium system surface, wherein a convexity geometry of the porous distribution medium on its side facing away from the evaporator medium system surface essentially corresponds to a convexity geometry of the porous distribution medium in the second part of the evaporator medium system surface and / or the porous distribution medium has an essentially constant thickness.

[0016] In a design that further enhances the efficient radial flow of liquid fuel, it is proposed that the porous distribution medium, on its side facing away from the evaporator medium system surface, extends essentially orthogonally to the longitudinal axis of the housing, and / or that the porous distribution medium has a thickness that increases from the radial inside to the radial outside. This means that the area of ​​the porous distribution medium through which liquid fuel flows radially increases from the radial inside to the radial outside not only due to the increasing distance from the housing axis, but also due to the increasing thickness of the porous evaporator medium.

[0017] To avoid heat loss, insulating material can be arranged on the side of the floor wall facing away from the evaporator medium system surface.

[0018] For a defined positioning of the porous evaporator medium, it is proposed that it be fixed at its outer circumference in relation to the combustion chamber floor.

[0019] For this purpose, the combustion chamber floor can include a retaining element surrounding the floor wall in a ring-like manner, wherein the retaining element includes at least one retaining projection holding the porous evaporator medium against the floor wall on its side facing the combustion chamber.

[0020] The invention further relates to a fuel-operated vehicle heater comprising a burner area with a combustion chamber assembly constructed according to the invention.

[0021] The present invention is described in detail below with reference to the accompanying figures. These show: Fig. 1 a longitudinal sectional view of a combustion chamber assembly for a vaporizer burner for a fuel-operated vehicle heater; Fig. 2 one of the Fig. 1 corresponding representation of an alternative design of a combustion chamber assembly; Fig. 3 one of the Fig. 1 Corresponding representation of an alternative design of a combustion chamber assembly; Fig. 4 one of the Fig. 1 corresponding representation of an alternative design type of a combustion chamber assembly.

[0022] The Fig. 1 The combustion chamber assembly 10, shown in longitudinal section, comprises a circumferential wall 12 of a combustion chamber housing 14, extending in the direction of a longitudinal axis L of the housing and, for example, being substantially cylindrical. In a Fig. 1 In the axial region not shown, a flame baffle may be provided on the inside of the circumferential wall 12. Adjacent to such a flame baffle, the circumferential wall 12 may transition into a flame tube or be connected to a flame tube designed as a separate component.

[0023] In a Fig. 1 In the axial end region of the circumferential wall 12 shown, a combustion chamber base, generally designated 16, is provided. The combustion chamber base 16 delimits a combustion chamber 18, which is bounded radially outwards by the circumferential wall 12 in the direction of the longitudinal axis L of the housing.

[0024] The combustion chamber floor 16 comprises a floor wall 20, in the radially central region 22 of which, with respect to the longitudinal axis L of the housing, a fuel supply line 24 opens for the supply of liquid fuel. On a side 26 facing the combustion chamber 18, the floor wall 20 of the combustion chamber floor 16 provides a concavely curved evaporator medium system surface 28 with respect to the combustion chamber 18.

[0025] A porous evaporator medium 30 is supported in the direction of the longitudinal axis L of the housing on the concavely curved evaporator medium system surface 28 of the bottom wall 20 with respect to the combustion chamber 18. The porous evaporator medium 30 can, for example, be made of wire material, in particular wire mesh, wire knitting, wire weaving, or the like, and can have such a porosity that liquid fuel, which enters the porous evaporator medium 30 from the fuel supply line 24 in the central area 20, is distributed in the internal volume of the porous evaporator medium 30 by capillary action and exits the porous evaporator medium 30 in vapor form on a side 32 of the porous evaporator medium 30 facing the combustion chamber 18.

[0026] The Fig. 1 The porous evaporator medium 30 shown, for example, has essentially the same thickness d in all circumferential and radial regions. This results in the porous evaporator medium itself, and in particular on its side 32 facing the combustion chamber 18, also being concavely curved, whereby, due to the essentially constant thickness d, the curvature geometry of the porous evaporator medium 30 on its side 32 facing the combustion chamber 18 essentially corresponds to a curvature geometry of the evaporator medium contact surface 28 on the side 26 of the combustion chamber floor 20 facing the combustion chamber 18.

[0027] To hold the porous evaporator medium 30 in a defined position against the evaporator medium system surface 28, a retaining element 34 is provided on the radially outer region of the combustion chamber base 16, surrounding the base wall 20 in a ring-like manner. This retaining element can, 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 be stably connected to the circumferential wall 12 or the base wall 20 by a material connection, for example by welding or brazing. In several areas spaced circumferentially apart, the retaining element 34 has retaining projections 36 bent radially inwards and towards the side 32 of the porous evaporator medium 30 facing the combustion chamber 18, which bear against the side 32 of the porous evaporator medium 30 facing the combustion chamber 18 in its radially outer area and thus hold it stably against the concavely curved evaporator medium contact surface 28.

[0028] To achieve a defined contact of the porous evaporator medium 30 with the evaporator medium contact surface 28 of the bottom wall 20 in this configuration, it can be provided, for example, that in a basic state in which the porous evaporator medium 30 is not held against the bottom wall 20 by the retaining projections 36, the porous evaporator medium 30 has a convex geometry with a greater curvature than the curvature of the evaporator medium contact surface 28. During assembly, the porous evaporator medium 30 initially comes into contact with the bottom wall 20 with its central area and is then pressed against the bottom wall 20 in its radially outer area by the retaining effect of the retaining element 34.This ensures in particular that in the radially inner area, i.e. in the central area 22 of the combustion chamber floor 16 where the liquid fuel is fed in, the porous evaporator medium 30 is held stably in contact with the evaporator medium system surface 28 without the risk of a gap forming between it and the floor wall 20.

[0029] The concave curvature of the porous evaporator medium 30 ensures that a crown 38 of the curvature, located in the central area 22 of the combustion chamber floor 16, forms the area of ​​the combustion chamber floor 16, or of the porous evaporator medium 30, furthest back from the combustion chamber 18 in the direction of the longitudinal axis L of the housing. Radially more outward areas of the porous evaporator medium 30 are then located further forward in the exhaust gas flow direction and, in particular, closer to the combustion air inlet openings 40 provided in the circumferential wall 12 for introducing combustion air. This results in no dead spaces being present, especially in the radially outer area at the transition from the combustion chamber floor 16 to the circumferential wall 12, where an excessively high fuel concentration could occur and the risk of deposit formation would be particularly pronounced.Furthermore, the concave curvature geometry of the porous evaporator medium 30 results in the following: when a vehicle heater comprising the combustion chamber assembly 10 is installed in this manner, with the side 32 of the porous evaporator medium 30 facing the combustion chamber 18 directed vertically downwards or obliquely downwards, the radially outer regions of the porous evaporator medium 30 lie further down in the vertical direction than the apex 38, in the region of which the liquid fuel is also fed into the porous evaporator medium 30. This results in a more uniform distribution of the liquid fuel introduced into the porous evaporator medium 30 in the region of the apex 38 radially outwards, aided by gravity.In conjunction with the increased surface area available for evaporation of the concavely curved porous evaporator medium 30 compared to a planar, uncurved structure of a porous evaporator medium, this leads to a particularly efficient, uniform delivery of vaporous fuel into the combustion chamber 18 across the entire porous evaporator medium 30.

[0030] A modified embodiment of the combustion chamber assembly 10 is in Fig. 2 As shown, in this embodiment, a recess 42 is formed in the bottom wall 20 of the combustion chamber floor 16. This recess is open on a side 47 of the bottom wall 20 facing the combustion chamber 18 and contains a porous distribution medium 44. In this embodiment, a first part 46 of the evaporator medium system surface 28 is formed on the bottom wall 20, and a second part 48 of the evaporator medium system surface 28 is formed on the porous distribution medium 44, surrounded by the first part 46. This evaporator medium system surface 28, formed by the two parts 46 and 48, also has a concave structure on its side 26 facing the combustion chamber 18.

[0031] The porous distribution medium 44 is positioned in the central area 22 of the combustion chamber floor 16, so that the liquid fuel supplied via the fuel supply line 24 first enters the porous distribution medium 44 and is distributed radially outwards within its volume. The liquid fuel then enters the porous evaporation medium 30, which is supported by the second part 48 of the evaporator medium system surface 28, already more evenly distributed radially and over a larger surface area, and is then further distributed radially outwards within its volume by capillary action and, as previously explained, also by gravity.

[0032] In order to achieve a rapid and efficient radial pre-distribution of the liquid fuel by the porous distribution medium 44, this preferably has a greater porosity than the porous evaporation medium 30. This means that a very rapid and somewhat coarser pre-distribution initially takes place in the porous distribution medium 44, while in the porous evaporation medium 30, which has a finer pore structure, a very uniform distribution of the liquid fuel and thus also a very uniform delivery of the fuel towards the combustion chamber 18 is provided.

[0033] At the Fig. 2 In the illustrated embodiment, the porous distribution medium 44 is convex in its entirety and thus has essentially the same thickness D in all circumferential and radial regions. This means that, with such a structure, the liquid fuel distributed radially outwards in the porous distribution medium 44 flows through a larger area of ​​the porous distribution medium 44 from radially inwards to radially outwards due to the increasing distance from the longitudinal axis L of the housing.

[0034] To make the radial distribution effect of the porous distribution medium even more efficient, as described in the Fig. 3 As shown in the illustrated embodiment, the thickness D of the porous distribution medium 44 increases from radially inward to radially outward, so that the increasing thickness D, i.e., the increasing axial extent of the porous distribution medium 44, also contributes to an increase in the area of ​​the porous distribution medium 44 available for fuel distribution and through which the fuel flows, towards the radial outward. This can be achieved, as shown in the Fig. 3 shows that the porous distribution medium 44, for example, is essentially orthogonally oriented on its side 50 facing away from the combustion chamber 18 or the evaporator medium system surface 28 to the longitudinal axis L of the housing and is therefore essentially planar.

[0035] The Fig. 4Figure 44 shows an embodiment in which a recess 54 is formed on a side 52 of the bottom wall 20 of the combustion chamber floor 16 facing away from the combustion chamber 18. This recess contains insulating material 56. The insulating material 56 can, for example, be a foamed material that has a lower thermal conductivity than air and, in particular, a lower thermal conductivity than the material of the bottom wall 20. The recess 44 can be closed by a cover 58, so that the insulating material 56 is held securely in the recess 54. This minimizes heat loss on the side 52 of the bottom wall 20 facing away from the combustion chamber 18 in a volume area where the relatively cold combustion air supplied by a combustion air blower generally flows.

[0036] The combustion chamber assembly shown in the figures, with its concavely curved porous vaporizer medium, particularly on the side facing the combustion chamber, not only achieves the previously mentioned aspects of efficient radial fuel distribution and the avoidance of dead spaces, but also increases the distance between the side of the porous vaporizer medium facing the combustion chamber and an ignition element, such as a glow plug, which generally extends radially inwards from the periphery wall at only a small axial distance to the combustion chamber floor. This prevents the risk of areas of local overheating occurring due to the curved structure of the porous vaporizer medium.This also reduces the risk of thermal destruction of the porous evaporator medium over its service life.

Claims

1. Combustion chamber assembly for an evaporator burner, in particular for a fuel-operated vehicle heater, comprising a combustion chamber housing (14) with a peripheral wall (12) extending in the direction of a housing longitudinal axis (L) and radially outwardly delimiting a combustion chamber (18), and a combustion chamber base (16) delimiting the combustion chamber (18) in the axial direction, wherein porous evaporator medium (30) is provided on a side (26) of the combustion chamber base (16) facing the combustion chamber (18), characterized in that the porous evaporator medium (30) is concavely curved on its side (32) facing the combustion chamber (18) with respect to the combustion chamber (18).

2. Combustion chamber assembly according to claim 1, characterized in that the porous evaporator medium (30) is concavely curved with respect to the combustion chamber (18), and / or that the porous evaporator medium (30) has a substantially constant thickness (d).

3. Combustion chamber assembly according to claim 1 or 2, characterized in thatin a radially central region (22) a fuel supply line (24) opens into the combustion chamber base (16), and in that the porous evaporator medium (30) has a curvature apex (38) in the radially central region (22).

4. Combustion chamber assembly according to one of claims 1-3, characterized in that the combustion chamber base (16) has, on its side (26) facing the combustion chamber (18), an evaporator medium contact surface (28) which is concavely curved with respect to the combustion chamber (18).

5. Combustion chamber assembly according to claim 4, characterized in that a curvature geometry of the evaporator medium contact surface (28) substantially corresponds to a curvature geometry of the porous evaporator medium (30) on its side (32) facing the combustion chamber (18).

6. Combustion chamber assembly according to claim 4 or 5, characterized in that the combustion chamber bottom (16) comprises a bottom wall (20) providing at least part of the evaporator medium contact surface (28).

7. Combustion chamber assembly according to claim 6, characterized in that the bottom wall (20) provides substantially the entire evaporator medium contact surface (28).

8. Combustion chamber assembly according to claim 6, characterized in that the bottom wall (20) comprises a recess (32) open towards a side (47) of the bottom wall facing the combustion chamber (18) for receiving a porous distribution medium (44), wherein a first part (46) of the evaporator medium contact surface (28) is provided on the bottom wall (20) and a second part (48) of the evaporator medium contact surface (28) is provided on the porous distribution medium (44).

9. Combustion chamber assembly according to claim 8, characterized in thatthe first part (46) of the evaporator medium contact surface (28) surrounds the second part (48) of the evaporator medium contact surface (28) in a ring-like manner, and / or that the porous distribution medium (44) is arranged substantially centrally with respect to the housing longitudinal axis (L), and / or that the porous distribution medium (44) has a greater porosity than the porous evaporator medium (30).

10. Combustion chamber assembly according to claim 8 or 9, characterized in that the porous distribution medium (44) is curved on its side (50) facing away from the evaporator medium contact surface (28), and that a curvature geometry of the porous distribution medium (44) on its side (50) facing away from the evaporator medium contact surface (28) substantially corresponds to a curvature geometry of the porous distribution medium (44) in the second part (48) of the evaporator medium contact surface (28), and / or that the porous distribution medium (44) has a substantially constant thickness (D).

11. Combustion chamber assembly according to claim 8 or 9, characterized in that the porous distribution medium (44) extends substantially orthogonally to the housing longitudinal axis (L) on its side (50) facing away from the evaporator medium contact surface (28), and / or that the porous distribution medium (44) has a thickness (D) increasing from radially inside to radially outside.

12. Combustion chamber assembly according to one of claims 6-11, characterized in that insulating material (56) is arranged on a side (52) of the bottom wall (20) facing away from the evaporator medium contact surface (28).

13. Combustion chamber assembly according to one of claims 1-12, characterized in that the porous evaporator medium (30) is fixed at its outer circumference with respect to the combustion chamber base (16).

14. Combustion chamber assembly according to claim 6 and claim 13, characterized in thatthe combustion chamber base (16) comprises a holding element (34) surrounding the base wall (20) in a ring-like manner, and in that the holding element (34) comprises at least one holding projection (36) holding the porous evaporator medium (30) against the base wall (20) on its side (32) facing the combustion chamber (18).

15. A fuel-operated vehicle heater comprising a burner region with a combustion chamber assembly (10) according to any one of the preceding claims.