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Metal foam radiant burner

Metal foam radiant burner description/claims

The present application claims priority to pending U.S. Provisional Patent Application No. 60/906,348 filed Mar. 12, 2007 which is incorporated herein by reference.

The present invention is related to radiant burners made of metal foam. More specifically, the present invention is related to metal foam radiant burners comprising grooves wherein the burner is capable of low gas input rates thereby allowing the burners to be used at lower temperatures

Radiant burners utilizing reticulated foam structures have been used in various applications. In general, there are two predominant classes of reticulated foam radiant burners. One type is ceramic foam and the other type, and the focus of this invention, is a metal foam.

Ceramic foams have been utilized in the burner art for some period of time. Ceramic foams are typically made by impregnating polyurethane foam with a ceramic precursor. The impregnated foam is then heated to vaporize the foam and then to sinter the ceramic. A reticulated ceramic is formed wherein the ceramic is in regions previously represented by voids in the foam and those area which were occupied by foam represent voids in the ceramic. Ceramic foam radiant burners are exemplified in U.S. Pat. No. 5,409,375 to Butcher which is incorporated herein by reference.

Ceramic foams are marginally suitable as the combustion surface in a radiant heater yet they are also known to be somewhat deficient. Ceramic foams do not heat evenly and zones which are significantly colder than average are routinely observed. Grooves in the surface mitigate the uneven heating to a certain extent, however, this exasperates problems associated with physical robustness. Yet another deficiency is the brittle nature of the ceramic. Ceramic foams are susceptible to flash back induced damage which has greatly minimized their wide spread acceptance as a suitable combustion surface. Yet another problem, particularly with reference to their use in gas grills, is that drippings from the food clog the pores of the ceramic thereby exasperating the uneven heating.

Metal foams alleviate some of the deficiencies of ceramic foams. They are more physically robust and less susceptible to damage from blow back. Part of the robustness is considered to be due to the high thermal shock resistance of metal foams as compared to ceramic foams. Metal foams can also be formed at lower relative densities than ceramic foam materials which is advantageous for gas flow through the porous structure and for weight reduction.

A particular advantage with metal foam is that they exhibit a more consistent thermal profile. The metal foam exhibits a resistance to flame penetration into the porosity of the material which greatly decreases flame flash-back. This also mitigates the appearance of the cool zones which are a prevalent problem in ceramic foams.

Food drippings are also less of a problem with metal foams since the drippings are typically wicked away from the surface and are therefore less likely to plug the pores.

For many of the reasons discussed above, metal foams have been considered a viable alternative to ceramic foam based radiant heaters. While metal foams do offer some advantages they are deficient in other ways. One limit to their wide spread use is the problem referred to as turn down characteristics. Metal foams perform poorly under low gas flow conditions and are therefore not suitable for low heat applications including cooking lighter meats, such as chicken or fish. Therefore, even though metal foam may be adequate for cooking a large steak they are limited in their ability to impact the market if they can not be used for other meats or items which require less heat. Dual burners have been used, however, this greatly increases the price since the grill must be manufactured with a high burner and a low burner in the same physical space. This is an unacceptable solution.

The use of reticulate foam as a combustion surface has never reached the anticipated potential. Ceramic foams are brittle and do not burn evenly whereas metal foams are inadequate for use in lower temperature applications with a low gas flow. Therefore, the art has long been suffering for a reticulated foam combustion surface which is physically robust, burns evenly, is less susceptible to clogging and which burns efficiently. The present invention provides such a material.

It is an object of the present invention to provide a reticulated foam radiant burner particularly suitable for use in low gas flow, or low heat, applications.

It is another object of the present invention to provide a radiant burner which is physically robust and which resist flame blow back.

A particular feature of the present invention is that it can be used as a natural draft burner thereby eliminating the necessity for forced air.

These and other advantages, as will be realized, are provided in a radiant burner. The radiant burner has a reticulated metal foam with a first face and a second face and a density sufficient for combustion fuel to pass there through. The first face is adapted to be the initial contact for the combustion fuel passing through the reticulated metal foam. The second face is adapted to radiate after the combustion fuel has been ignited. The second face has a plurality of grooves.

Yet another embodiment is provided in a heating system. The heating system has an apparatus for providing combustible gas. A mixer is provided which is capable of mixing the combustible gas with air to form a combustible fuel mixture. A reticulated metal foam burner is provided with a first face and a second face wherein the first face is capable of receiving the combustible fuel mixture and the combustible fuel mixture passes through the reticulated metal foam burner for combustion on a second surface. The second surface has a plurality of grooves. A plenum chamber is provided which is adapted to distribute the combustible fuel mixture over the first surface.

• Provisional Patent
• Utility Patent

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