EVAPORATOR ASSEMBLY UNIT, ESPECIALLY FOR A VEHICLE HEATER OR A REFORMER ARRANGEMENT OF A FUEL CELL SYSTEM

Abstract

An evaporator assembly unit, especially for a vehicle heater or a reformer arrangement of a fuel cell system, includes a wall arrangement (12) enclosing an evaporation chamber (20) with a circumferential wall (14) and with a bottom wall (16). An air introduction shoulder (18) extending in the direction of a wall longitudinal axis (L) is provided with a plurality of first air introduction openings (22). Evaporator medium (26), that is porous at least in some areas, is provided on the side of the wall arrangement (12) facing the evaporation chamber (20). An auxiliary air opening arrangement (34) with at least one second air introduction opening (36) is provided in the wall arrangement (12).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a longitudinal sectional view of an evaporator assembly unit designed according to the present invention;

FIG. 2 is a view corresponding to FIG. 1 of an evaporator assembly unit of an alternative design;

FIG. 3 is another view corresponding to FIG. 1 of an evaporator assembly unit of an alternative design; and

FIG. 4 is a cross-sectional view of the evaporator assembly unit shown in FIG. 3, cut along a line IV-IV in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings in particular, An evaporator assembly unit is generally designated by 10 in FIG. 1. This evaporator assembly unit 10, which can be inserted, for example, into an evaporative burner of a vehicle heater, in which the heat generated by combustion is transferred to a heat carrier medium, comprises a wall arrangement generally designated by 12 with a circumferential wall 14 and with a bottom wall 16. The circumferential wall 14 and the bottom wall 16 of the wall arrangement 12 form a pot-like assembly unit elongated in the direction of a longitudinal axis L of the wall. The circumferential wall 14 and the bottom wall 16 are designed in the example being shown as integral components of the wall arrangement 12, which can be manufactured, for example, by a casting process from metallic material. The circumferential wall 14 and the bottom wall 16 could, of course, also be made available as separate components and assembled subsequently.

An air introduction shoulder 18 begins from the bottom wall 16 in the central area of the bottom wall 16 in the direction of the wall longitudinal axis L. This shoulder 18, just as the circumferential wall 14, may be of a cylindrical, for example, regular cylindrical shape, and it extends into an evaporation chamber 20, which is enclosed by the circumferential wall 14 and the bottom wall 16 and which can also be called a combustion chamber if the evaporator assembly unit 10 is used in an evaporative burner.

A plurality of slot-like first air introduction openings 22, which likewise extend, for example, in the direction of the wall longitudinal axis L and via which the air delivered by an air delivery blower 24 of an air delivery arrangement generally designated by 25 can flow into the evaporation chamber 20, as is indicated by flow arrows, are present in the air introduction shoulder. It shall be pointed out here that the air delivery blower 24 is presented only symbolically and could be designed, for example, as a by-pass channel blower. Furthermore, it is possible that an air introduction arrangement with a plurality of blades extending helically is provided in the area of the bottom wall 16 on the side thereof facing away from the evaporation chamber 20, so that a twist can be additionally imposed on the air flowing into the air introduction shoulder.

A porous evaporator medium 26 is provided on a side of the circumferential wall 14 facing the evaporation chamber 20. This porous evaporator medium 26, built up, for example, from wire mesh, knitted wire, foam ceramic or the like, extends along the circumferential wall 14 starting from the bottom wall 16 approximately in the axial area, in which the air introduction shoulder 18 extends as well. The porous evaporator medium 26 is preferably designed such that it covers the entire circumferential wall 14 in the circumferential direction in the axial area shown.

Liquid fuel or hydrocarbon is introduced into this porous evaporator medium 26 via a fuel guide arrangement, not shown, and distributed in the inner volume area of the evaporator medium and then released on the side of the porous evaporator medium 26, which side is freely exposed towards the evaporation chamber 20. It shall be pointed out here that one or more shoulders, which extend outwardly, for example, tangentially from the circumferential wall 14 and which may likewise be lined with porous evaporator medium and used to receive an igniting member or for introducing the fuel, could be provided, for example, at the circumferential wall 14.

A flame screen 28 with a central opening 30 is arranged on the inner side of the circumferential wall 14 in an area located farther away from the bottom wall 16. When combustion is taking place, this flame screen 28 essentially limits the evaporation chamber or combustion chamber 20, and the combustion waste gases and the flame will move into a next section of the circumferential wall, which is generally also called flame tube 32. It is obvious that the flame tube 32, as is shown, may be made integral with the area of the circumferential wall 14 forming the evaporation chamber 20, but it may, of course, also be designed as a separate component.

Furthermore, an auxiliary air opening arrangement 34 with a plurality of second air introduction openings 36, which are provided in the circumferential wall 14 here, are provided in the evaporator assembly unit 10 next to the air introduction shoulder 18. These second air introduction openings 36 may be provided in the circumferential direction around the wall longitudinal axis L following each other approximately in the same axial area of the circumferential wall 14, namely, in the area that is no longer covered by the porous evaporator medium 26. It is recognized in FIG. 1 that the second air introduction openings 36 may have a different shape. Thus, as is shown in the upper part of FIG. 1, they may be elongated in the circumferential direction, or they may be circular, as is shown in the lower part of FIG. 1. A combination of elongated and circular second air introduction openings 36 is, of course, possible, as is a combination of second air introduction openings located in different axial areas of the circumferential wall 14.

To make it possible to guide the air being delivered by the air delivery blower 24 in the direction of the wall arrangement 12 not only to the bottom wall 16 and thus into the air introduction shoulder 18, but also to the auxiliary air opening arrangement 34, the air feed arrangement 25 comprises, furthermore, an outer wall or an outer housing 38, which, surrounding the circumferential wall 14, provides with the latter a, for example, annular flow space 40. This annular flow space 40 leads to the second air introduction openings 36 of the auxiliary air opening arrangement 34, so that the air being delivered by the air delivery blower 24 can also enter through the second air introduction openings 36 into the evaporation chamber 20, as is indicated by flow arrows.

Various advantages are gained with the design of an evaporator assembly unit shown in FIG. 1 during the evaporation or combustion operation. Thus, by additionally introducing air, a markedly better mixing of the fuel vapor being released via the porous evaporator medium 26 with the air being introduced is achieved. As a consequence, the combustion taking place or started in the evaporation chamber 20 will take place with a better quality and hence with the formation of a reduced amount of pollutants. Furthermore, the risk of fuel deposits or deposits of combustion residues is reduced. By providing the auxiliary air opening arrangement 34, a sharper physical separation of the sections of the circumferential wall 14 located on the two axial sides of the second air introduction openings 36 is achieved. Since the area of the circumferential wall 14, which is located to the right of the second air introduction openings 38 in the view shown in FIG. 1 and hence farther downstream in the direction of flow of the combustion waste gases, which said area is also used as a flame tube 32, is heated intensely during the combustion taking place, a sharper thermal uncoupling of the area of the circumferential wall 14 or wall arrangement 12, which also surrounds above all the porous evaporator medium 26, is achieved due to the interruptions in the circumferential wall 14. This is advantageous especially when low-boiling fuels are used. The extent of the thermal uncoupling can, of course, be strongly affected here by the size of the interruptions formed in the wall arrangement 12 in the circumferential direction. Furthermore, the flow of the air to be introduced into the evaporation chamber 20 via the second air introduction openings 36 past the circumferential wall 14 through the annular flow space 40 leads to an additional cooling of the area of the circumferential wall 14 in which the porous evaporator medium 26 is provided and the fuel is also introduced. The risk of boiling of fuel is thus counteracted, and the air to be introduced into the evaporation chamber 20 can also be heated during its flow through the flow space 40.

FIG. 2 shows a variant of the embodiment shown in FIG. 1, in which an auxiliary air opening arrangement 34 is likewise provided in the area of the circumferential wall 14. It is recognized that the wall arrangement 12 comprises two wall components 42, 44 here, of which the wall component 42 provides the bottom wall 16 and an adjoining section of the circumferential wall 14. This is especially also the area of the circumferential wall 14 in which the porous evaporator medium 26 is arranged. The wall component 44 axially joins the wall component 42 and thus likewise represents an area of the circumferential wall 14 or the area of the circumferential wall 14 that is also the area acting as the flame tube 32. Furthermore, the flame screen 28 may be provided in this wall component 44.

The two wall components 42, 44 are provided with radially outwardly directed flange sections 46, 48. The two wall components 42, 44 are rigidly connected to one another by connection elements 50, which are schematically indicated in FIG. 2, for example, screws or clinched bolts or the like, via the intermediary of spacers 52, in the area of these flange sections 42, 44 in a plurality of circumferential positions. An annular gap, which is interrupted by the spacers 52, is thus formed between the two wall components 42, 44, and the gap sections formed between consecutive spacers 52 in the circumferential direction provide the second air introduction openings 36 of the auxiliary air opening arrangement 34. Thus, the possibility of introducing air into the area of the evaporation chamber 20 through a plurality of elongated second air introduction openings 36 in the circumferential wall 14, which said openings 36 follow each other in the circumferential direction, is thus created again. The same advantages as those described above arise concerning the mixing with the evaporated fuel and also the thermal uncoupling. In particular, the thermal uncoupling can, however, be achieved even better by the fact that materials with poor thermal conduction are used for the spacers 52, which form heat bridges between the two wall components 42, 44. The flow conditions and the thermal uncoupling can, of course, again be affected strongly by the design of the spacers 52 and a possibly annular spacer provided with through openings for providing the second air introduction openings 36.

Another embodiment of an evaporator assembly unit with an auxiliary air opening arrangement is shown in FIGS. 3 and 4. A design that is, in principle, similar to that shown in FIG. 1 is recognized here. However, the auxiliary air opening arrangement 34 is provided here with its second air introduction openings 36 in the area of the bottom wall 16. The second air introduction openings 36 are located in the annular area of the bottom wall 16 surrounding the air introduction shoulder 18 and thus they likewise form, as can be recognized from FIG. 4, a sequence of openings following each other in the circumferential direction around the wall longitudinal axis L. As is indicated in FIG. 4, a plurality of shapes or dimensions of the second air introduction openings are possible here as well. Thus, these second air introduction openings may be elongated in the circumferential direction, as is shown in the left-hand part of FIG. 4, or they may be, for example, circular, as is shown in the right-hand part of FIG. 4.

A markedly better mixing of the evaporating fuel with the air being introduced is also achieved with this embodiment of the auxiliary air opening arrangement 34. It is highly advantageous that starting from the bottom wall 16, an air flow stream is provided essentially in parallel to the surface of the porous evaporator medium 26, which transports the fuel evaporated from there into the area of the evaporation chamber 20, which latter area follows it in the axial direction. The transport of the heat absorbed during the combustion taking place in the area of the air introduction shoulder 18 is also made difficult in the direction of the area of the circumferential wall 14 in which the porous evaporator medium 26 is provided, so that the risk of excessively intense or too early boiling of fuel can be eliminated here as well.

By providing the auxiliary air opening arrangement 34, improved evaporation and mixing properties are ensured in an evaporator assembly unit 10 of such a design, and lower pollutant emissions and reduced amount of deposits of combustion residues are ensured during the combustion. Furthermore, the heat balance can be strongly affected by the selection of the number, the selection of the shape and the selection of the positioning of the second air introduction openings 36, especially in the area in which the fuel is to be fed in and evaporated. This makes it possible to design such an evaporator assembly unit specifically for a fuel that is to be used such that combustion characteristics that are optimal for that particular fuel can be obtained. This is especially advantageous when biological fuels, e.g., PME (vegetable oil methyl ester) or rapeseed oil or the like, are to be used, whose combustion characteristics differ markedly from those of conventional fuels, e.g., gasoline.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

Claims

1. An evaporator assembly unit for a vehicle heater or a reformer arrangement of a fuel cell system, the evaporator assembly unit comprising: a wall arrangement enclosing an evaporation chamber with a circumferential wall with a wall longitudinal axis and with a bottom wall;an air introduction shoulder provided at said bottom wall and extending in the direction of said wall longitudinal axis and with a plurality of air introduction openings;an evaporator medium, which is porous at least in some sections, provided on a side of said wall arrangement facing said evaporation chamber; andan auxiliary air opening arrangement with an auxiliary air introduction opening in said wall arrangement.

2. An evaporator assembly unit in accordance with claim 1, wherein said auxiliary air introduction opening is in said circumferential wall.

3. An evaporator assembly unit in accordance with claim 2, wherein at least part of said evaporator medium is provided at said circumferential wall and said auxiliary air introduction opening is provided in an area of said circumferential wall not covered by said evaporator medium.

4. An evaporator assembly unit in accordance with claim 3, wherein said evaporator medium is provided essentially in an area of said circumferential wall located in an area in which said air introduction shoulder extends axially.

5. An evaporator assembly unit in accordance with claim 2, wherein said circumferential wall comprises two wall components which follow each other in the direction of said wall longitudinal axis, said two wall components being rigidly connected to one another, said auxiliary air introduction opening being formed by an intermediate space between said two wall components.

6. An evaporator assembly unit in accordance with claim 5, wherein said two wall components are rigidly connected to one another in a plurality of circumferential areas via intermediary spacers, wherein said auxiliary air introduction opening is formed at least in one area between two said spacers following each other in a circumferential direction.

7. An evaporator assembly unit in accordance with claim 1, wherein said auxiliary air introduction opening is provided in said bottom wall in an area surrounding an air introduction insert.

8. An evaporator assembly unit in accordance with claim 1, wherein said auxiliary air opening arrangement includes said auxiliary air introduction opening and at least one further auxiliary air introduction opening to provide a plurality of auxiliary air introduction openings following each other in the circumferential direction.

9. An evaporator assembly unit in accordance with claim 8, wherein at least one said second air introduction openings is elongated.

10. An evaporator assembly unit in accordance with claim 1, further comprising an air feed arrangement for feeding air to be introduced into said evaporation chamber in a direction of said bottom wall of said wall arrangement.

11. An evaporator assembly unit in accordance with claim 10, wherein said air feed arrangement comprises means for feeding air in a direction of said circumferential wall of said wall arrangement.

12. An evaporator assembly unit comprising: a wall arrangement including a circumferential wall extending in an axial direction and with a bottom wall, said wall arrangement defining an evaporation chamber;an air introduction shoulder extending interiorly of said circumferential wall and in the axial direction from said bottom wall, said air introduction shoulder having a plurality of air introduction openings;an at least partially porous evaporator medium provided on a side of said wall arrangement facing said air introduction shoulder; andan auxiliary air opening arrangement with an auxiliary air introduction opening in said wall arrangement.

13. An evaporator assembly unit in accordance with claim 12, further comprising: an air feed arrangement for feeding air to be introduced into said evaporation chamber in the axial direction into an interior of said air introduction shoulder and through said plurality of air introduction openings into said evaporation chamber, wherein said auxiliary air opening arrangement includes said auxiliary air introduction opening and at least one further auxiliary air introduction opening to provide a plurality of auxiliary air introduction openings in said circumferential wall and said air feed arrangement comprises means for feeding air to said auxiliary air introduction openings for air to flow radially into said evaporation chamber.

14. An evaporator assembly unit in accordance with claim 13, wherein at least part of said evaporator medium is provided at said circumferential wall and said auxiliary air introduction openings are provided in an area of said circumferential wall not covered by said evaporator medium.

15. An evaporator assembly unit in accordance with claim 14, wherein said evaporator medium is provided essentially in an area of said circumferential wall located in an area in which said air introduction shoulder extends axially.

16. An evaporator assembly unit in accordance with claim 15, wherein said circumferential wall comprises two wall components which follow each other in the axial direction, said two wall components being rigidly connected to one another, said auxiliary air introduction openings being formed by an intermediate space between said two wall components.

17. An evaporator assembly unit in accordance with claim 16, wherein said two wall components are rigidly connected to one another in a plurality of circumferential areas via intermediary spacers, wherein said auxiliary air introduction openings are formed between two circumferentially adjacent said spacers.

18. An evaporator assembly unit in accordance with claim 13, wherein at least one said second air introduction openings is elongated in the circumferential direction.

19. An evaporator assembly unit in accordance with claim 12, further comprising: an air feed arrangement for feeding air to be introduced into said evaporation chamber in the axial direction into an interior of said air introduction shoulder and through said plurality of air introduction openings into said evaporation chamber, wherein said auxiliary air opening arrangement includes said auxiliary air introduction opening and at least one further auxiliary air introduction openings to provide a plurality of auxiliary air introduction openings in said bottom wall in an area surrounding said air introduction insert and said air feed arrangement comprises means for feeding air to said auxiliary air introduction openings for air to flow axially into said evaporation chamber.