High efficiency radiant burner

Abstract

A naturally aspirated, fully aerated radiant burner and optional heat exchanger arrangement where the radiant burner has a generally enclosed cavity defined, at least in part, by fuel gas impermeable surroundings and a lower surface of fuel gas permeable burner element, wherein cavity preferably has two opening exposed to an oxidizer source. Sealingly coupled to openings are mix tubes, each having respective first ends and second ends, wherein first ends occupy openings and second ends extend into and are exposed to cavity. Fuel gas injectors, which during use are in fluid communication with fuel gas, are positioned to introduce fuel gas into mix tubes and entrain only slightly more air than needed for stoichiometric combustion. Pre-combustion gasses migrate to upper surface where stable stoichiometric combustion occurs, resulting in low CO and NOx emissions, increased wind resistance and elevated combustion gas temperatures Connecting the heat exchanger directly to the burner further increases its wind resistance and prevents dilution of the combustion gases by wind or free convection.

Description

FIELD OF THE INVENTION[0001]The present invention relates to controlled, low emissions, combustion and more particularly to pressurized hydrocarbon gas burners and most particularly to a liquid pressurized gas (LPG) burner / heat exchanger system that Includes a high efficiency heat exchanger working in conjunction with a fully aerated radiant burner.DESCRIPTION OF THE PRIOR ART[0002]Conventional gas external combustion apparatus traditionally use partially aerated fuel-air mixtures and require introduction of relatively large quantities of secondary air for complete combustion to occur. This dilution of the post combustion gases reduces heat transfer efficiencies into a heat transfer surface, such as a fluid container in a cooking or water heating system, e.g., a pot, or a commercial or residential hot water tank. Additionally, the volume of introduced secondary air is dependent on the apparatus' natural convection and diffusion properties, which limit the driving pressure of the pre...

AI Technical Summary

Benefits of technology

[0007]The present invention is directed to a naturally aspirated, fully aerated burner, an optional heat exchanger arrangement optimized for fluid containers, and systems incorporating the combination thereof. Burner embodiments of the invention use premixed fuel-air in conjunction with relatively low burner surface temperatures and incandescing surface combustion to efficiently create heat with minimal CO and NOx combustion by-products. High heat transfer values to containers exposed to the burner are achieved through forced convection of hotter, undiluted, combustion gases to optimized heat exchangers associated with the containers, which increase overall efficiency of system embodiments (70% to 85% in the embodiment described in detail herein), without adding excessive heat exchanger surface area or materially impeding the convective gas flow. An additional benefit realized by system embodiments of the invention is markedly increased resistance to the deleterious effects of wind, particularly in exposed conditions.

[0008]Unlike free convention prior art burners that rely upon the introduction of secondary air to provide sufficient oxidizer for proper combustion, burner embodiments of the invention exploit forced convection principles. Thus, as heat output is increased, the driving pressure for forced convection is also increased, and heat transfer efficiency is generally constant over a wide range of heat level outputs. Because complete combustion is achieved at the burner element outer surface without the addition of secondary air, the optional heat exchanger can mate directly with the burner, eliminating the cooling effects of convecting air and making the burner essentially impervious to wind. An optional thermally activated fuel flow interrupt increases the safety of the burner by stopping fuel flow in the case of an overheat scenario. The result of this arrangement provides for a radiant burner that is has increased resistance to the deleterious effects of wind on the burner, that greatly increases the safety of operation of the radiant burner, and that significantly reduces the output of NOx and CO.

[0009]Burner embodiments of the invention comprise a generally enclosed cavity defined, at least in part, by a fuel gas impermeable surrounding and an inner surface of a fuel gas permeable burner element, wherein the cavity has at least one opening exposed to an oxidizer source, preferably oxygen present in the ambient environment. Sealingly coupled to the at least one opening is fuel-air mixing element or mixing means having a first end and a second end, wherein the first end is exposed to and / or is fluidly coupled with the at least one opening of the cavity and the second end extends into and is exposed to and / or is fluidly coupled with the cavity. In a preferred embodiment, the mixing element or mixing means is a mix tube, which maximizes both the air entertainment and resulting momentum transfer as well as thorough mixing of the air with the fuel gas. As those persons skilled in the art will appreciate, any structure capable of mixing a gaseous fuel with a gaseous oxidizer, preferably air from the ambient environment, can be used as, or in place of, a mix tube, and therefore such structures are considered equivalent thereto.

[0013]In order to increase the efficiency of burner embodiments of the invention, containment vessels, such as pots, can be specially adapted to exploit the quantity and quality of heat output of such burners, as previously intimated. A primary mode of efficiency enhancement comprises the use of integrated or removable heat exchanging structure at or near the bottom of containment vessels. Such structure preferably comprises a plurality of fins, either as fin elements integral with the vessel or as fin bodies attachable to the vessel, arranged to maximize radiant and convective heat transfer of combustion gasses from the burner. Alternatively, efficiency enhancement comprises the use of heat exchanging structure at or near the outer surface of the burner element, which may or may not be removable. Efficiency can be further increased by maximizing the thermal absorptivity of the vessel surface to optimize radiative heat transfer. Each relevant containment vessel will have a bottom surface and a lower side surface that is linked to the bottom surface by a shoulder.

[0014]The burners described and illustrated below provide a user with exceptional efficiency and significantly decreased undesirable combustion byproducts. For example, CO emissions are about 8 times less than a comparably sized conventional portable stove. Similarly, nitrogen oxides are significantly reduced (approximately 80-93%) when compared to commercially available competing portable stoves.

Problems solved by technology

The result of this arrangement provides for a radiant burner that is has increased resistance to the deleterious effects of wind on the burner, that greatly increases the safety of operation of the radiant burner, and that significantly reduces the output of NOx and CO.

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