DE102004028305B3 - Porous vaporizer medium used in vaporizing burners in vehicle heating devices comprises a body having a pore structure and preferred pore orientation consisting of long chain particles made from magnetizable or magnetized material - Google Patents

Abstract

Porous vaporizer medium comprises a body having a pore structure and preferred pore orientation consisting of long chain particles made from magnetizable or magnetized material. An independent claim is also included for a process for the production of a porous vaporizer medium. Preferred Features: The body is connected to a further body which has a pore structure without a preferred orientation.

Description

The The present invention relates to a porous evaporator medium, as it is used for example in evaporator burners in vehicle heaters according to the generic term of claim 1, and a method for its production.

at Such evaporator is in a combustion chamber housing the porous Evaporator medium, for example, at a bottom area or on a Peripheral wall area provided as a plate-like or cylindrical body. Through the pore structure in the body of the porous one Evaporator medium is the fed into this liquid fuel or hydrocarbon under capillary action in the volume of this body distributed. At the a combustion chamber or a fuel vapor receiving facing side of the porous Evaporator medium can at the appropriate temperature of the first still liquid Evaporate fuel or hydrocarbon and, for example, then with Air an ignitable or combustible mixture form. The advancement of the liquid fuel in the pore structure causing capillary force is generally superimposed on gravity. This gravity overlay As a result, when, for example, vertical orientation of the body of porous Evaporator medium the liquid Fuel will preferentially move to the lower area while in upper areas a certain fuel depletion occurs. This is therefore particularly disadvantageous, especially in the upper Area in a combustion chamber higher Temperatures will prevail and there the preferred evaporation of the fuel occurs.

A porous evaporator medium according to the preamble of claim 1 is known from US 4,745,568 known. This document discloses a ring-like wick element, can be sucked through which fuel and released for combustion. The wicking element is multi-layered, with layers of long fibers oriented substantially in one direction.

The DE 102 44 812 A1 shows a provided as a lining for a combustion chamber of a heater porous medium having a substantially disc-like structure. In an area of this element constructed, for example, of fabric material or mesh material, the flow resistance is increased in order to influence the flow characteristic.

The DE 102 22 969 A1 discloses an evaporator structure made from powder particles in a vacuum plasma spray process. As powder materials metals or metal alloys can be used.

The US 5,278,007 relates to a ceramic structure with then embedded, elongated particles. In this way, a pore structure with a certain orientation is created.

The DE 100 52 075 A1 discloses a method for producing porous layers by means of a spin-coating method. Such layers can be used in microelectronics, in sensors or in catalytic reactions. In carrying out the process, the porous particles used for this purpose should have an approximately spherical shape. It is also possible to provide needle-shaped or disk-shaped particles, that is to say preformed particles, which, when they are magnetic, are aligned by application of a magnetic field.

It the object of the present invention is a generic porous evaporator medium so educate, or such a method for its production to provide, in a simple manner a preferential orientation of this constituent particle is obtained.

According to one First aspect of the present invention, this object is achieved by a porous one Evaporating medium, in particular for a Ver steamer burner of a vehicle heater, comprising one with pore structure trained body, wherein at least in a volume region of the body, the pore structure a Having preferred pore orientation, wherein the body of a plurality of elongated Particles is constructed, wherein at least in the volume range the elongated particles have a preferred orientation and the elongated particles of magnetizable or magnetized Material are constructed.

While there is a virtually random distribution or orientation of the pore structure in the case of the porous evaporator media known from the prior art, according to the invention a defined pore structure is provided at least in one area of the body. This has the consequence that the flow behavior of the liquid in the body of the evaporator medium can be influenced in a defined manner. If the pores are oriented in a particular preferred orientation, the flow resistance in the direction of this preferred orientation will be less than transversely thereto. This can be used to facilitate the flow of liquid in certain directions, while in the other direction this streaming can be made more difficult. Furthermore, it becomes possible by magnetic interaction to specify a defined position of these particles and then to maintain them in the finished porous evaporator medium.

According to one Another advantageous aspect may be provided that the body with another body is connected and that the further body has a pore structure in the Has substantially no preferential pore orientation. The porous evaporator medium can therefore multilayered with the respective layers or layers forming bodies or be designed multi-layered. The one with pore preferential orientation can be configured, so in terms of material selection be built that this preference, for example can be obtained by magnetic interaction. The other Lage, in which such pore preferred orientation is not required or is provided, for example, from a thermal point of view Load optimized material to be constructed.

For example can be further provided that the preferred orientation in essence is a circular orientation.

• a) Bereitstellen einer Vielzahl langgestreckter Partikel,
• b) Ausrichten der Partikel wenigstens in einem Volumenbereich mit einer Vorzugsorientierung,
• c) Herstellen einer Verbindung zwischen benachbarten Partikeln,

wobei der Schritt a) das Bereitstellen langgestreckter Partikel aus magnetisierbarem oder magnetisiertem Material umfasst und der Schritt b) das Bereitstellen eines wenigstens einen Teil der Partikel ausrichtenden Magnetfeldes umfasst.According to a further aspect, the object mentioned at the outset is achieved by a method for producing a porous evaporator medium given above, comprising the steps:

• a) providing a plurality of elongate particles,
• b) aligning the particles at least in a volume region with a preferred orientation,
• c) establishing a connection between adjacent particles,

wherein step a) comprises providing elongated particles of magnetizable or magnetized material and step b) comprises providing a magnetic field aligning at least a portion of the particles.

The Production of a porous Evaporator medium with multi-layered structure, so one more connected bodies comprehensive construction, can be obtained by the step a) the provision of a plurality of layers of different particulate material and in that step b) the alignment of particles in only a part of the layers of particulate material.

Here Thus, several layers are applied in a manufacturing process or with each other also "baked in." Alternatively is it is possible that after execution of steps a) - c) at least steps a) and b) for a further layer of Particle material performed become.

at the method according to the invention can be further provided that the step c) the exercise of Pressure at elevated Temperature includes.

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

1 a longitudinal sectional view of a combustion chamber housing;

2 the principle of the construction according to the invention of a porous evaporator medium;

3 one of the 2 corresponding view;

4 another illustration for illustrating the principle of the present invention;

5 the procedure in the preparation of an evaporator medium according to the invention.

In 1 is an evaporator housing generally with 10 designated. This evaporator housing 10 may be referred to as a combustion chamber housing, for example, in a reformer for producing a mixture of hydrocarbon vapor with mixed material, so for example air, water vapor and the like, when used in an evaporator burner, for example. The housing 10 includes a bottom wall 12 and a peripheral wall 14 and thus forms a substantially pot-like structure. In the peripheral wall 14 can have multiple openings 16 be provided to allow air in the housing 10 formed chamber 18 involved. In the ground area 12 opens a pipe 12 a, for example, the liquid fuel can promote. Adjacent to the ground area 12 is a multi-layered porous evaporator medium 22 intended. This porous evaporator medium 22 comprises a first body formed with pore structure 24 , the bottom wall 12 is arranged opposite. Here, for example, between the bottom wall 12 and this first pore-structured body 24 an electrically energizable heater may be provided.

In accordance with the principles of the present invention, the body is 24 designed so that the formed therein and essentially to Kapillarför effect contributing pore structure at least in certain volume areas of the body 24 has a specific pore preference orientation. By specifying such a preferential pore orientation and the flow resistance for the capillary flow is defined adjustable. The flow resistance will be greater than in the direction of this preferential orientation, transversely to the preferred pore orientation, ie its preferred longitudinal extension. In this way it becomes possible, the flow of the over the line 20 The liquid fuel fed in under the influence of gravity preferably counteracts downwards. If, for example, as explained below, the preferred pore orientation is circular and concentrically surrounds the area of fuel introduction, the following effect is obtained: 1 right, that in the chamber 18 combustion, the temperature in the upper region will be the highest, in the center, ie in the area of the fuel inlet, due to the existing there cooler fuel will be minimal and will rise to the bottom again. As a result, the fuel will vaporize the most in the upper region, resulting in a relatively high transpiration effect. This transpiration or fuel depletion in this upper region of the porous evaporator medium 22 or the body 24 As a result, more fuel or liquid is replenished from other fuel enriched areas. Due to the mentioned circular pore orientation can now but also along this circular orientation in the lower part of the body 24 By gravity, preferably accumulated fuel to be promoted easier up and evaporate there. It is thus obtained a homogenization of Abdampfungscharakteristik. Other preferred pore orientations are conceivable. For example, in the area of the body that is under the introduction of fuel 24 the preferred orientation pores extend substantially horizontally, so are transverse to the direction of gravity, while in the upper region, the pore preferred orientation can be vertical, ie substantially in the direction of gravity. Thus, the flow is opposed to a greater flow resistance than the flow upward, which allows compensating for the effect of gravity.

The provision of such a body 24 can be realized, for example, that this body with at least in certain volume ranges existing pore preferred orientation 24 is built up of small elongated, so fibrous designed particles. If these particles of magnetized or magnetizable material, ie metal material, such as stainless steel, constructed, it can be obtained by applying or exerting a magnetic field during the production process, a certain preferred orientation of these elongated particles. This is in 2 with regard to the above-mentioned circular pore preferred orientation explained. Here is in the center of the body to be formed an electrical conductor 26 provided a current 1 leads. The current flow creates a magnetic field represented by the conductor 26 concentric surrounding magnetic field lines M. Now becomes in this magnetic field, the particulate material 28 from which the body 24 is to be formed, it will be obtained in a sufficiently strong magnetic field, a preferred orientation of these elongated particles in the direction of the magnetic field when these particles are magnetized. In areas where the magnetic field is no longer strong enough to achieve the alignment of the small particles, as in 3 makes clear that the statistical, that is completely random, distribution of these particles is retained with regard to their orientation. So become during the manufacturing process of the body 24 First, the elongated and magnetized or consisting of magnetizable material, such as ferromagnetic material particles aligned by providing a magnetic field, then while maintaining this orientation, the particles can be connected together, for example in a sintering process. The body thus produced 24 then has the desired orientation.

It goes without saying that other orientations can be provided, as in 4 is illustrated. Here are two permanent magnets 30 . 32 provided that form between them a very homogeneous magnetic field with substantially rectilinear field lines M. Here, therefore, a substantially linear orientation of the elongated particles is obtained. By superimposing different magnetic fields, it becomes possible to have a body 24 build up, which has different preferred orientations of the pore structure or the elongated particles in different volume areas and accordingly also defines a defined conduction behavior.

The production of such a body 24 for the porous evaporator medium 22 is in 5 illustrated again with reference to the circular pore-preferred orientation. You can see a shape here 34 in which one of the shapes of the porous evaporator medium to be formed 22 corresponding depression 36 is formed. In the central area of this depression 36 is an opening 38 for passing an electrical conductor 26 intended. The particulate material 28 for the body 24 gets into this depression 36 entered with the desired layer thickness. Then a current is passed through the conductor 26 directed, so that in 2 and also in 3 discernible preferred orientation of the particles in the particulate material 28 will occur. Once this alignment has been achieved, the leader can 26 are pulled out, since the switching off of the electric current is generally no longer cause a change in position. Below, for example, the opening 38 be closed from the outside and by a stamp 40 a pressure on the particulate material 28 be exercised. At the same time, the shape 34 be heated, so that by pressure and exercise temperature then in a sintering process, a solid body having the desired structure and in particular the desired pore preferred orientation is obtained. It goes without saying that in the form 34 several such depressions 36 can be provided and thus simultaneously several bodies 24 can be produced.

In particular, if that is for the construction of the body 24 used particulate material 28 due to the required magnetic properties in the chamber 18 If the temperatures to be expected have a critical thermal stability, that is, if possible should not be exposed to correspondingly high temperatures, it is advantageous to use the porous evaporator medium 22 multi-layered, so for example with another body 42 build. Also, this is preferably made of a porous material, so it is provided with pore structure, but without pore preference orientation. This body 42 so it will have the property in the body 24 already pre-distributed liquid medium substantially only in the direction of the chamber 18 to lead. It should therefore be the body 22 be designed only with such a thickness that it for the body 24 provides the required thermal insulation, but otherwise the least possible influence, especially the influence of gravity, can affect the liquid medium to be conveyed. For this body 42 can be used in terms of thermal load less critical material, such as stainless steel or ceramic material CrNiSi. Also this body 42 can be produced from a particle-like material under a sintering process under pressure and under the influence of temperature. In particular, it is possible this body 42 simultaneously with the body 24 to build. For example, after arranging the particulate material 28 for the body 24 and producing the preferred orientation of the particles the material for the body 42 be sprinkled, or it may be after sprinkling the particulate matter for the body 42 Only the magnetic field can be generated to align the particles of the particulate material 28 to get. This should then be the material for the body 42 can not be influenced magnetically. The two bodies 24 . 42 or the layers provided by this body can then be provided in a manufacturing process as an integral body. At the same time can also be at the chamber 18 facing side of the body 42 a serving as a support wire mesh 44 be involved. In the manufacturing process for the in 1 recognizable multi-layered or consisting of several bodies construction can of course also proceed so that, for example, the body first 24 produced under pressure and temperature, then on this body 24 the particulate matter for the body 42 is applied and at the same time with this then the material for the wire mesh 44 is involved.

Claims (7)

Porous evaporator medium, in particular for an evaporator burner of a vehicle heater, comprising a body formed with a pore structure ( 24 ), wherein at least in a volume region of the body ( 24 ) the pore structure has a preferential pore orientation, the body ( 24 ) is constructed of a plurality of elongated particles, wherein at least in the volume region, the elongated particles have a preferred orientation, characterized in that the elongated particles of magnetizable or magnetized material. Porous evaporating medium according to claim 1, characterized in that the body ( 24 ) with another body ( 42 ) and that the further body ( 42 ) has a pore structure substantially without preferential pore orientation. porous Evaporating medium according to one of claims 1 or 2, characterized that the preferred orientation is essentially a circular orientation is. Process for the preparation of a porous evaporator medium according to one of the preceding claims, comprising the steps: a) Providing a plurality of elongate particles, b) Align the particle at least in a volume region with a preferred orientation, c) Establishing a connection between adjacent particles, in which the step a) providing elongate particles of magnetizable or magnetized material and that step b) the Providing an at least a portion of the particles aligning Magnetic field includes. A method according to claim 4, characterized in that step a) comprises providing a plurality of layers of different particulate materials, and that step b) comprises aligning particles in only a part of the layers made of particulate material. Method according to claim 5, characterized in that that after execution of steps a) - c) at least the steps a) and c) for another layer of particulate material is performed. Method according to one of claims 4 to 6, characterized that step c) exercise from increased pressure Temperature includes.