DE10233340B4 - Pore burner and cooking device containing at least one pore burner - Google Patents

Abstract

Pore burner, in particular for cooking appliances, with a housing which has at least one inlet for a gas / air mixture as fuel and / or at least one inlet for air and / or at least one inlet for gas and at least one outlet for air and / or gas and / or exhaust gases, the housing having sintered metal powder and / or, in particular pressed, metal wire mesh in the form of at least one dimensionally stable, porous shaped body (7, 7 '), on the surface of which there are reaction zones of flame development to form a surface burner, characterized by at least two, At least in sections, form-fitting, mutually adjoining molded bodies which are connected to one another in particular in regions, preferably with the formation of at least one groove or phase, and form a stable connection.

Description

The present invention relates to a pore burner, especially for cooking devices, with a housing that at least one inlet for a gas / air mixture as fuel and / or at least one inlet for air and / or at least an inlet for gas and at least one outlet for air and / or Has gas and / or exhaust gases, wherein the housing sintered metal powder and or, especially pressed, Has metal wire mesh in the form of at least one dimensionally stable, porous shaped body, on its surface Reaction zones of flame development to form a surface burner as well as a cooking device, containing at least one pore burner.

Pore burners are well known to the person skilled in the art. This is generally a burner with a predetermined combustion chamber volume with spatially connected cavities, over which a defined flame zone is formed. Embodiments of known pore burners can be found, for example, in US 5,522,723 , WO 95/01532, DE 199 39 951 A1 and DE 199 04 921 C2 described. With the help of pore burners, for example, the size of industrial and domestic steam or hot water boilers can be reduced, since the thermal energy is emitted both by radiation and by means of heat conduction, which reduces the convective portion of the heat transfer. In the DE 199 04 921 C2 For example, a housing container is described which, in addition to a radiation heat exchanger and a convection heat exchanger, also comprises a pore burner which is suitable for heating liquids. In the DE 198 04 267 A1 there is a large water space boiler equipped with a pore burner for generating steam and / or hot water.

Especially with compressed construction and high ambient temperatures, according to DE 199 39 951 A1 a flashback that frequently occurs under these conditions or poor flame stability, for example due to pressure fluctuations and negative pressure, is avoided by increasing the pore size of the pore burner in the direction of flow. In this case, a critical Peclet number must be maintained in a zone of the porous material for the pore size, above which the flame develops and below which it is suppressed. With a pore burner, as in DE 199 39 951 A1 described, the reaction of the fuel / oxidant mixture takes place within the porous matrix. This porous matrix is preferably produced by filling from temperature-resistant ceramic balls or saddle bodies. Packing according to DE 199 39 951 A1 accordingly have at least two zones made of bulk material with different pore sizes. WO 95/01532 also deals with the problem of producing a stable flame at low temperature and low pollutant emissions. This publication shows that the porosity of the pore burner along the combustion chamber is changed in such a way that the pore size increases in the direction of flow of the gas / air mixture from the inlet to the outlet. The porous material used in the pore burner is in turn obtained via bulk material, for example in the form of loosely layered grains, which are solidified in a sintering process.

In the previously described pore burners known from the prior art find the Reactions underlying flame formation between the fuel gas and the oxidizing agent predominantly regularly or completely within the porous Matrix instead. Accordingly, the stream be called Reaction products without flame formation from the combustion cavities. This procedure entails that the flames pass through the burner material chilled be what a further flame propagation as well as a flashback helps prevent. However, are the burner masses as well as the burner loads dimensioned very small, it can still cause a flashback come. This is e.g. regularly then the case when in compact heaters due to high ambient temperatures high temperatures are also present in the combustion chamber itself. A flashback let yourself then often just about adequate flame cooling to reach. For this you need however it is a big one Mass with high heat capacity and good thermal conductivity. The pore burner devices described continue to have in common that a optimized gas homogenization and gas distribution over the burner surface as well Adequate flame stability and dimensional stability of the surface regularly only through the Use of several components of different geometries and / or Materials succeed.

Suitable flat-flame burners on the basis of porous burners are only known in the form of sintered discs, such as a flat-flame burner according to the so-called "Kaskan-type" (by WE Kaskan, "The dependence of flame temperature on mass burning velocity", 6 ^th Symp. (Int .) on Combustion, The Williams & Wilkins Company, Baltimore, 1956, pages 134 to 143).

The DE-US 2 211 297 relates to a burner for gaseous fuels containing a porous wall element, the wall element being made of porous metal obtained by sintering spherical metal particles. Known burners containing asbestos disks and metal nets should be able to be replaced with such burners. The EP 0 635 677 A1 is a pore burner based on a pressed metal wire knit remove. With such an arrangement, a uniform, stable flame pattern should be possible and flame flashback should be avoided. From the US 5,470,222 is a heating unit with a burner made of porous ceramic material, with which very low pollutant emissions can be realized. The EP 0 382 674 A2 again describes an infrared burner made of corrosion-resistant wire mesh, which is provided with a thick porous layer of ceramic fibers. When using such a burner, an improved energy efficiency should result. In the burner system according to the EP 0 840 061 A1 several separate pore burner elements formed from pressed metal wire mesh are connected to one another via non-porous cross bars. The EP 0 390 255 A1 describes a burner membrane made of porous sintered tissue made of inorganic fiber materials, which is provided on the outside with a pattern of furrows. In this way, damage or breakages in the porous structure should be avoided or prevented during the heating process. The JP 62062110 A a cylindrical burner can be seen, which is formed from several ceramic surface burners. The individual burner elements lying against each other are held together via a head and end plate, which are connected with a threaded rod. The JP 2001165412 A describes a surface burner that can be operated at low temperature, which in turn results in low NO _x emissions. This is achieved by a special arrangement of air and fuel supply to a mixing chamber, which in turn is connected to a conical burner made of knitted metal wire.

A high level of flame stability, the prevention of flashback as well as the warranty a uniform and constant flame front with a flat flame burner can only be regularly with a porous High homogeneity material obtained, otherwise otherwise an uneven flow profile results. A porous However, a matrix with a sufficiently high degree of homogeneity can usually only be used realize up to a specified component size. For larger dimensions Burner systems are therefore regularly cut back with regard to a uniform flow profile and the associated properties.

Conventional fully premixed burners, in particular also surface burners or flat flame burners, have so far generally been made from sheet metal built up with hole and / or Slit patterns are provided, such as by burners in cylindrical combustion chambers known. For an almost homogeneous distribution of the A gas mixture is required further more sheets with a coarser perforation, which are below of the aforementioned sheets. Only under these design guidelines regularly succeeds only the flow velocities so that everyone Place the respective gas / air mixture in a suitable amount can. Known surface burners can others also from a fixed on a support structure flexible wire mesh, made of perforated ceramics or wire mesh consist. However, gas homogenization and gas distribution are required also for the flame stability and dimensional stability the surface also always the combination of several components from different ones Geometries and materials.

In general, conventional cooking has so far been used for cooking appliances Heating systems with electrical or gas powered heating elements. This would improve the efficiency of such heating systems contribute to the natural Conserve energy resources and reduce pollutant emissions.

It would therefore be desirable to use cooking appliances to be able the, independent of their size. about a very energy-efficient and low-pollutant and therefore also eco-efficient Heating system.

The present invention lies therefore the task of making pore burners accessible, in particular for cooking appliances make or the generic pore burner to develop in such a way that they no longer have the disadvantages of generic pore burners and especially about a high level of flame stability and homogeneity, especially in execution as a surface burner or flat flame burner. Accordingly lies the present invention further has the object of generic cooking appliances in this way evolve that they with a high level of energy efficiency and the lowest possible operating costs, eco-efficient and can be heated constantly.

According to the invention, this object is achieved by Pore burner according to claims 1 and 4th

Accordingly, the entire molded body surface can already be used as those caused by the porous Structure, the outlet, the pore burner according to the invention represent, if necessary also without a defined, large-area outlet, for. B. at one end of the case. The pore burner according to the invention regularly has at least one Inlet for a gas / air mixture as fuel. About that in addition or alternatively, the pore burner or the housing of the Pore burner over at least one further inlet for air and / or have another inlet for gas. For example fed separately Air as secondary air or for cooling of components of the pore burner.

The pore burner according to the invention can For example, for the generation of heat and / or steam in cooking appliances, in particular gas-heated cooking appliances, and also also in heating appliances such as boilers or gas heating appliances, for example in domestic technology, in particular when using cylindrical combustion chambers.

It can be provided according to the invention that the moldings essentially a hollow body, in particular a hollow cylinder. Suitable hollow bodies can also be used in any have geometric shapes, e.g. in cross section an ellipse, a triangle, a square, a Represent a rectangle or any polygon. Suitable hollow bodies can also Completely do without a defined, large outlet opening and e.g. be designed as an ellipse, sphere or cylinder with only at least a defined opening for the Inlet of the Gas / air mixture. About the Use of hollow bodies it is easy to achieve the largest possible surface for a uniform flame front to accomplish.

It has been found to be very advantageous that pore burners accessible are where the molded body at least one mounting and / or fastening element, in particular a flange and / or a thread. Brackets and fasteners can with the pore burners according to the invention thus already in the dimensionally stable molded body, e.g. made of pressed metal wire, be integrated, thereby reducing the manufacturing costs of the pore burner according to the invention let and a production for the large series is much easier to implement. Of course, the dimensionally stable molded body for attachment also simply welded on be, for example on the tube for supplying the fuel mixture. This can be particularly easy to accomplish when both the pipe and the dimensionally stable molded body matches Have cross sections and e.g. the shaped body is cylindrical and the tube is circular Cross section.

According to another aspect of Invention are pore burners containing at least two, at least sectionally to each other moldings, which in particular in areas, preferably with the formation of a groove, are interconnected. By form-fittingly combining shaped bodies, large-size pore burners can also be used, for example realize without sacrificing an even gas passage or an even flow profile have to be accepted. Two or more joined together moldings can about a Phase or a groove enter into a stable connection. The moldings are preferably only in very few, adjacent areas connected to each other and thus secured against loosening. A constant Material density remains in the area of the joints largely preserved, which ensures a uniform flow profile is. So far with very large ones moldings a high homogeneity of the porous material and thus also of the type described above one if possible uniform flow profile can not always be maintained, with the previous one described embodiment also pore burner of larger design accessible, the above their entire burner surface over one extremely even flow profile feature. In a preferred embodiment are the dimensionally stable molded bodies, especially hollow bodies, formed in such a way at their respective end regions or head surfaces, that these correspond in shape to one another, so that e.g. the front area of a shaped body yourself if possible a perfect fit in the rear area of another molded body, in particular of such an identical design. This allows pore burners to be used get that in length can be extended as required are without, however losses in terms of homogeneity have to be accepted.

It can be provided according to the invention that the Material densities of at least two abutting moldings in the essentially match.

Furthermore, has in this context as a preferred embodiment pointed out that the Material density in the area of the junction of two to each other joined moldings essentially corresponds to the material density of at least one of these moldings.

Another embodiment of the invention is characterized in that the Surface of the molding at least one irregularity, in particular has at least one indentation and / or elevation, which by the base area of the shaped body differs. Through indentations and / or elevations, i.e. Irregularities in the surface of the shaped body is regularly prevented that itself forms an essentially two-dimensional reaction zone. Prefers are accordingly such Surfaces, who don't have a completely uniform surface and therefore not e.g. about himself uniform Repeat structures. It is usually enough for this from, molded body, especially hollow bodies, with different material thicknesses to be used, especially if they are based on sintered metal powder. In this way it is already prevented that self-excited vibrations on the burner surface can arise. The surface of dimensionally stable, especially pressed, metal wire knits as such is generally sufficiently irregular to the described resonance phenomena to prevent, of course however also about different strengths feature.

Accordingly, one embodiment provides that the wall thickness of a shaped body varies and in particular has at least two different strengths. Accordingly, the wall thickness of a hollow body must not be constant within the same in this embodiment.

Preferred pore burner in the sense of the present invention are flat flame burners.

Particularly preferred pore burners are characterized in that the molded body has, at least in some areas, in particular in the area of a metal wire knit, a compression density in the range from about 2.5 to about 5 g / cm ³ , in particular from about 2.8 to about 4.5 g / cm ³ . Lower compression densities generally require lower blower capacities because of the lower pressure losses, whereas higher compression densities enable more uniform reaction zones to be achieved. The pressed metal wire knitted fabrics according to the invention, like the sintered metal powder moldings, are already dimensionally stable as such and, for example, do not require, for example, the targeted mixture management or the shaping of any stabilizing elements, for example in the form of perforated metal sheets, in order to provide functional flat-flame burners.

Such pore burners are also from Advantage where the wire diameter of the metal wire mesh in the range from about 0.1 to about 0.4 mm, in particular from about 0.16 up to about 0.28 mm. In addition to the compression density, the porosity of the pore burner according to the invention can be on the basis of pressed Knitted wire also over the wire gauge, i.e. the wire diameter, and / or the number of pressed wires in the knitted fabric influence. For example, the wire mesh consists of only one relatively thick wire, the pore burner usually has relatively size Pores with essentially matching Pore size. On the other hand, e.g. three wires with smaller diameters, receives one generally has different pores at the same compression density Size, however mostly on average under the previously described embodiment lies.

Pore burners according to the invention containing knitted metal wire feature accordingly further advantageous Way over 1 to 5, especially 1, 2 or 3, metal wires.

It can be provided according to the invention that this Metal wire mesh wound axially or radially before pressing is present.

Furthermore, pore burners according to the present invention are preferred, with which surface loads in the range from 20 to 300 W / cm ² , in particular from 30 to 260 W / cm ² , are accessible. Accordingly, the flame does not rise in the pore burners according to the invention even at 200 W / cm ² and more. The maximum area load is often not limited by the wire mesh, but by the delivery rate of the air and / or gas supply. The surface load lower limit is regularly formed by the flame being extinguished as a result of high heat conduction by contact with the metallic surface. With a three-strand knitted metal fabric based on a heat-resistant steel, for example 1.4828, with a compression density of about 3.8 g / m ³ , surface loads in the range of about 30 to 160 W / cm ³ can be easily achieved, for example. The pore burner according to the invention thus enables a very wide range of possible operating states between extinguishing the flame on the one hand and lifting the flame on the other hand and therefore also a power modulation range of 1: 5 and more. For example, a glowing wire mesh is obtained with a surface load of approximately 70 W / cm ² with an air ratio of approximately λ = 1.2. If the air ratio drops, the annealing will start at higher outputs, with higher air numbers the surface will only shine at very low outputs. With an increasingly intensive glow, the proportion of the amount of heat transported via radiation from the reaction zone becomes ever greater.

In a further embodiment according to the invention it is envisaged that Metal powder and / or the metal wire mesh at least one metal and / or comprises a metal alloy, the or which forms an oxide layer, especially a metal alloy, containing chrome and / or aluminum. As suitable metals and metal alloys for the metal powder to be sintered and in particular for the wire mesh are preferred heat-resistant materials, for example heat-resistant steels. this includes fall z. B. high-alloy steels like low-carbon austenitic chrome, nickel and manganese steels. exemplary be on the heat-resistant Steel 1.4828 (X15 CrNiSi 20-12) referenced. Still well suited are those metals or metal alloys that have a Can form oxide layer, whereby the molded body can be equipped with a protective layer. Particularly suitable Metal alloys have aluminum and / or chromium components or are composed of these metals. A suitable material z. B. the alloy with the material number 1.4767 (CrAl 20 5) and the alloys with the material number 1.47675 represents.

Another embodiment of the invention has the subject pore burner systems that a pore burner according to the invention and at least one feed pipe for Air and / or gas which can be connected to an inlet of the pore burner, include.

It can be provided according to the invention that at least an inlet of a dimensionally stable molded body over a Bracket and / or a fastening element, in particular a flange and / or a thread, connected to at least one supply pipe for air and / or gas is.

Furthermore, it can be provided according to the invention that at least one inlet of a form stable molded body is at least partially welded onto at least one supply pipe for air and / or gas.

According to a further aspect of the present invention, the object is further achieved by a cooking device, in particular a gas-heated cooking device, which contains at least one pore burner, in particular a pore burner according to the invention or a pore burner system according to the invention. Basically, pore burners are suitable for use in cooking devices according to the invention, such as those in the US 5,522,723 , WO 95/01532, DE 199 39 951 A1 and DE 199 04 921 C2 are described. However, preference is given to using the pore burners according to the invention. Suitable cooking devices are those with closed as well as open systems. Gas-heated cooking appliances, in particular those with a pore burner that functions as a surface burner, are preferably used. Small cooking appliances, for example kitchen cooking appliances, can also be equipped with pore burners, in particular pore burners according to the invention, as can large-scale cooking appliances that are used, for example, in commercial kitchens.

With the pore burners according to the invention a very high level of flame stability achieved. At the same time, flashback is essentially completely prevented. Accordingly Pore burner available posed with a porous material high homogeneity and even flow profile, the as a surface burner consistently have a uniform and constant flame front and are particularly suitable as flat flame burners. With the pore burners according to the invention a quasi-two-dimensional flat flame is maintained over the entire burner surface receive. The cooking devices according to the invention have a very high efficiency and can be extremely eco-efficient, e.g. conserving resources and low in pollutants. The heat input is very even and can also precisely regulated and controlled in a direct and simple manner become. surprisingly The properties described above can also be done in this way realize with cooking devices according to the invention, that are small. The cooking devices according to the invention can thus both in canteen kitchens, e.g. for the Canteen operation, as well as used in restaurants become. cooking appliances with surface burners housed in it are therefore easily accessible.

Other features and advantages of Invention result from the following description, in which preferred embodiments the invention by way of example with reference to schematic drawings in detail explained become. It shows:

1 the schematic structure of a cooking device according to the invention, containing a pore burner; and

2 a hollow cylindrical pore burner in cross section.

This in 1 shown cooking appliance 1 includes an interior 2 with a pore burner according to the invention 4 for the generation of hot air. Alternatively or additionally, you can use the pore burner 4 or another pore burner (not shown) on the other hand, steam is also generated. Each pore burner is included to monitor the burner function 4 a sensor, not shown, in the form of an ionization current sensor, and in each case an ignition device, not shown. The pore burner 4 with fuel gas or a fuel gas mixture via a supply line 6 with the interposition of a first gas valve (not shown). This gas valve takes over the functions of pressure control, quantity setting and, if necessary, gas filtering. The pore burner 4 is designed as a hollow cylinder and has a thread at one end, which is integrated in one piece in the molded body forming the porous body (not shown). The dimensionally stable molded body, which is present as a pressed wire knit in the present embodiment, can be threaded over this thread 7 immediately with a base 8th be screwed, which already ensures a secure connection to the supply line 6 is guaranteed without the need for additional components, which also enables different pore burners 4 or molded body 7 exchange them in a simple and uncomplicated way.

2 is a schematic representation of a pore burner 4 ' can be seen in cross section. The wall 10 of the hollow cylindrical shaped body 7 ' of the pore burner 4 ' has irregularities 12 and 14 in the surface 16 of the molded body, which indicates a different thickness of the molded body wall 10 declining. The phenomenon of combustion-induced, self-excited vibrations does not regularly occur in pore burners designed in accordance with the invention. By making the irregularities 12 and 14 of the shaped body 7 ' are formed as grooves that can interlock, can with these moldings 7 ' that can be placed against each other in a form-fitting manner, larger pore burners can also be created. The groove engages 12 a first molded body 7 ' in the groove 14 a second molded body 7 ' whose free groove 12 again with the groove 14 a third molded body 7 ' can be combined with positive locking.

The in the description above, in the drawings and in the claims disclosed features of Invention can both individually and in any combination for the realization of the invention in its various embodiments.

1

Cooking appliance

2

inner space of the cooking appliance

4, 4 '

porous burner

6

supply line

7, 7 '

dimensionally stable moldings

8th

Base with thread

10

wall of the hollow cylindrical molding

12 14

irregularities or grooves of the molded body

16

Surface of the molding

Claims (21)

Pore burner, in particular for cooking appliances, with a housing which has at least one inlet for a gas / air mixture as fuel and / or at least one inlet for air and / or at least one inlet for gas and at least one outlet for air and / or gas and / or exhaust gases, the housing being sintered metal powder and / or, in particular pressed, metal wire mesh in the form of at least one dimensionally stable, porous molded body ( 7 . 7 ' ), on the surface of which there are reaction zones of the flame development to form a surface burner, characterized by at least two, at least in sections positively abutting, joined together molded bodies which are connected to one another in certain areas, preferably with the formation of at least one groove or phase, and a stable connection received. Pore burner according to claim 1, characterized in that the Material densities of at least two shaped bodies lying against one another essentially match. Pore burner according to claim 1 or 2, characterized in that the Material density in the area of the junction of two to each other joined moldings essentially corresponds to the material density of at least one of these moldings. Pore burner, in particular for cooking appliances, with a housing which has at least one inlet for a gas / air mixture as fuel and / or at least one inlet for air and / or at least one inlet for gas and at least one outlet for air and / or gas and / or exhaust gases, the housing being sintered metal powder and / or, in particular pressed, metal wire mesh in the form of at least one dimensionally stable, porous molded body ( 7 . 7 ' ), on the surface of which there are reaction zones for flame development to form a surface burner, characterized in that the shaped body ( 7 . 7 ' ) at least one integrally formed mounting and / or fastening element, in particular a flange and / or a thread ( 8th ). Pore burner according to one of the preceding claims, characterized in that the shaped body ( 7 . 7 ' ) essentially represents a hollow body, in particular a hollow cylinder. Pore burner according to one of the preceding claims, characterized in that the surface ( 16 ) of the molded body ( 7 ' ) at least one irregularity ( 12 . 14 ), in particular at least one indentation and / or elevation, which extends from the base of the shaped body ( 7 ' ) deviates. Pore burner according to one of the preceding claims, characterized in that the wall thickness of a shaped body ( 7 ' ) varies, in particular has at least two different strengths. Pore burner according to one of the preceding claims, characterized characterized that said pore burner represents a flat flame burner. Pore burner according to one of the preceding claims, characterized in that the shaped body ( 7 . 7 ' ), at least in some areas, in particular in the area of a metal wire knitted fabric, has a compression density in the range from about 2.5 to about 5 g / cm ³ , in particular from about 2.8 to about 4.5 g / cm ³ . Pore burner according to one of the preceding claims, characterized characterized that the wire diameter of the metal wire mesh in the range from about 0.1 to about 4 mm, in particular from about 0.16 to about 0.28 mm lies. Pore burner according to one of the preceding claims, characterized in that the knitted metal wire 1 to 5 , In particular 1, 2 or 3, includes metal wires. Pore burner according to one of the preceding claims, characterized characterized that the metal wire mesh axially or radially wound before pressing. Pore burner according to one of the preceding claims, characterized in that surface loads in the range from 20 to 300 W / cm ² , in particular from 30 to 260 W / cm ² , are accessible with said pore burner. Pore burner according to one of the preceding claims, characterized in that the metal powder and / or the metal wire mesh comprises at least one metal and / or a metal alloy or include, which forms an oxide layer, in particular a metal alloy containing chromium and / or aluminum. Pore burner system, comprising a pore burner according to one of claims 1 to 14 and at least one supply pipe for air and / or gas that with an inlet of the Pore burner is connectable. Pore burner system according to claim 15, characterized in that that at least an inlet of a dimensionally stable molded body over a Bracket and / or a fastener, especially one Flange and / or a thread, with at least one supply pipe for air and / or Gas is connected. Pore burner system according to claim 15, characterized in that that at least an inlet of a dimensionally stable molded body on at least one feed pipe for Air and / or gas is at least partially welded on. Use of pore burners according to one of claims 1 to 14 or pore burner systems according to one of claims 15 to 17 for generating heat and / or steam in cooking appliances ( 1 ), especially gas-heated cooking appliances, or in heating appliances. cooking appliance, in particular gas-heated cooking appliances, comprising at least one pore burner according to one of claims 1 to 14 or a pore burner system according to one of claims 15 to 17. Heater, comprising at least one pore burner according to one of claims 1 to 14 or a pore burner system according to one of claims 15 to 17th