JP2009503433A - High efficiency radiant burner with optional heat exchanger - Google Patents

Abstract

The radiant burner (10) has an enclosure (2, 14) that is at least partially impermeable to fuel gas and a generally sealed cavity (24) defined by the underside of the combustion gas permeable burner member 60. Arrangement of a radiant burner (10) and optionally a heat exchanger 90, the cavity (12) preferably having two openings (16a, 16b) exposed to an oxidant source. There are mixing tubes (50a, 50b) sealed and connected to openings (16a, 16b) each having a first end (52a, 52b) and a second end (54a, 54b), and the first end (52a, 52b) seals the opening (16a, 16b) and the second end extends to be exposed in the cavity (12). The fuel gas injectors (48a, 48b) are arranged to introduce combustion gases into the mixing tubes (50a, 50b) when the fuel gas (100) and fluid are allowed to move during use. The pre-combustion gas moves to the top surface (64) and is made available for ignition. A block of hot fuel flow is placed between the combustion gas (100) and the gas injectors (48a, 48b) to isolate the combustion gas in the event of overheating malfunction. Because of the function of the burner (60) as a radiant body, a high heat exchange efficiency over the prior art is for specific applications arranged for the burner (60) or a container (70) located in the vicinity thereof. By producing the heat exchanger arrangement (90), this fact can be exploited effectively. Effective use of the relatively low velocity of the hot combustion gases at the exposed surfaces (80, 82, 84) is constructed, thereby increasing the heat exchange flux in the vessel (70).

Description

  The present invention relates to controlled combustion, and more particularly to a pressurized hydrocarbon gas burner, and more particularly to a pressurized liquid gas having a high efficiency heat exchange device that functions in conjunction with a radiant burner that is fully aired. (LPG) relates to a stove / cookware system.

  Conventional gas burning appliances use a burner with partially introduced air and require the introduction of a relatively large amount of second air in order to generate complete combustion. In a cooking system that uses a liquid container such as a pot, for example, the diffusion of the combustion gas lowers the temperature of the flame and reduces the efficiency of heat exchange with the electric heating surface. In general, the amount of secondary air supplied depends on natural convection, the diffusion of combustion gases, which brings the pressure of the gas and excess air to a pressure that can only be obtained by the buoyancy effect of the hot gas. To limit the supply. Therefore, the heat exchange value by forced convection is larger than the value by natural convection. At present, many companies (Cascade Design Inc. and JetBoil, Inc) are from traditional stove and pot combinations (35% -55%) (45% -65%) ) Has proposed a gas combustion device with a heat exchange device that increases the efficiency of such a device because it is limited by the free convection heat exchange coefficient and the diffusion of the combustion gas with the second air. There is a limit to increasing efficiency.

  Manufacturers of combustion appliances based on heat exchange equipment must also strive to continuously improve combustion and heat exchange efficiency while also addressing environmental concerns associated with combustion by-products . As such a combustion by-product, nitrogen oxides (NOx) are of particular concern in connection with domestic gas water heaters. The initial combustion of the gas in a natural convection heater generates a high temperature that results in nitrogen oxides. The combustion gas undergoes some additional combustion and is diluted by the free convection air in the area where gas release and velocity are reduced.

  The present invention utilizes the arrangement of a radiant burner and optionally employed heat exchanger to obtain a high heat transfer value to the containment vessel through forced convection and higher temperature non-diffusive combustion gases, and provides extra surface area. Increase overall system efficiency (70% -85%) without adding heat exchangers. The burner also significantly lowers the temperature at which complete combustion occurs, thereby significantly reducing the generation of nitrogen oxides. A feature of the present invention is that the driving pressure for forced convection with optional heat exchange equipment is increased so that the output is increased, thereby stabilizing the heat exchange efficiency in a generally wide output range. . As a result of this arrangement, a radiant burner is provided that has high fuel efficiency, high resistance to the adverse effects of the wind of the burner, increases the operational safety of the radiant burner, and significantly reduces the generation of nitrous oxide. . When used in combination with an optional heat exchanger, the combustion efficiency is higher and the generation of nitrous oxide is further reduced

  In general, a radiant burner is composed at least in part of a closed cavity defined by a perimeter that is not permeable to combustion gas and a lower surface of the burner member that is permeable to combustion gas, the cavity being a supply of at least one oxidant. Opening exposed to the source. There is a mixing tube sealingly connected to at least one opening and defined by a longitudinal axis and having first and second ends. The first end closes at least one opening and the second end extends and is exposed to the pressure cavity. Those skilled in the art will appreciate that any structure capable of mixing a gaseous oxidant and a gaseous fuel can be used as a mixing tube. Such structures are therefore considered as equivalent. A combustion gas injector, which is communicatively connected to a fuel gas source and fluid during use of the burner, is arranged to supply fuel gas to the mixing tube. Preferably, it is placed at or near the first end. Thereby, when oxide is supplied at or near this location, it promotes oxide momentum transfer towards the flow of fuel gas.

  Due to the porosity of the burner member, a pressure gradient exists between the cavity and the upper surface of the burner member. As a result, the precombustion gas diffuses from the lower surface to the upper surface of the burner member. Thereafter, the preheated gas is ignited on the upper surface, and combustion is started by an ignition device or the like connected to the burner.

  In one series of embodiments, multiple openings are present in the pressure cavity. A corresponding number of cylindrical mixing tubes are connected in fluid communication with the openings and are exposed to the ambient environment at the first end and to the cavity at the second end. Thus, the surrounding environment supplies an oxidant, such as oxygen. Preferably, when a corresponding number of fuel gas injectors are provided in the mixing tube, the mixing gas first in the mixing tube to mix the two gases so that the combustion gas takes in a certain amount of air and generates a preheated gas. Mounted on one end. The preheated gas is preferably further mixed and turbulence is generated in the preburning gas stream by a plurality of fixed mixing posts. Also preferably, the mixing post serves to radiate heat that may accumulate in the burner housing through exposure to a cold pre-combustion gas.

  The feature of the burner is that a thermal fuse (trip filter) arranged between the fuel gas and the gas injector is adopted. This fuse is made of a material that reacts as preset to heat so that the shape of the material deforms when exposed to heat above a certain temperature for a set time, and the fuel is Operates to prevent flow to the gas injector. In one series of embodiments, the filter is a eutectic metal such as an alloy of cadmium, tin, lead, etc., and is formed in a washer that maintains the check valve operatively at the opening. Thus, in the event of a malfunction due to light back or heat, the elevated temperature causes the washer to liquefy, thereby closing the check valve and causing the combustion gas from melting. To isolate.

  In order to increase the efficiency of a system using a radiant burner, a storage container such as a pot is employed specifically to extract the amount and characteristics of the heat output by the radiant burner sufficiently. The main form for application involves the use of a heat exchange structure at or near the bottom of the containment vessel. Preferably, it is comprised by several fins, such as a fin member integral with a container, or a fin main body which can be attached to a container, and it adjusts so that the radiation | emission of combustion gas and conduction of convective heat may become the maximum from a burner. Each associated container will have a bottom surface and a lower surface that is continuous with the bottom surface by a shoulder. The purpose of the heat exchange structure is to increase the duration of exposure of the container to the burner output, thereby further increasing the efficiency of the system using a radiant burner.

  The burner described and illustrated greatly reduces the efficiency and unwanted combustion by-products. As an example, the production of CO is about one-eighth of a conventional stove of comparable size. Similarly, nitrogen oxides are greatly reduced (approximately 80-93%) when compared to commercially available competing stoves.

  The following description is presented to enable any person skilled in the art to make and use the invention. Various modifications of the preferred embodiment will be readily apparent to those skilled in the art. Also, the general principles described herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention as defined by the appended claims. Accordingly, the present invention is not intended to limit the disclosure of the embodiments and is to be accorded the widest scope consistent with the principles and features disclosed herein.

  Unless otherwise stated here, the burner 10 and the heat exchanger 90 are made of metal. Depending on where the part is applied, the metal may be aluminum, steel, copper, brass, or similar conventional metal. The choice of metal naturally takes into account resistance to corrosion and heat resistance to high temperatures, but first it is chosen in consideration of heat conduction, and weight considerations are also an effective criterion for the selection of metals. sell. In a preferred embodiment, the burner member 60 is comprised of a porous metal foam material sold under the trademark METPORE by Porvair Advanced Materials, Inc. of Hendersonville, North Carolina. The However, those skilled in the art will appreciate that other gas porous, refractory materials can be used, such as ceramics and metal-ceramic composites.

  Referring now to FIGS. 2 and 3, an embodiment of the burner of the present invention is shown in front and plan cross-sectional views, respectively. The burner 10 is composed of a metal base 12 and is provided with a fuel supply structure 30 (detailed below) that partially defines a cavity 24. The cavity 24 is further defined by the metal enclosure 14 and the burner member 60. As described in more detail below, the cavity 24 is entirely sealed from the external environment with two major exceptions. First, the mixing tubes 50a and 50b are hermetically attached to the surrounding portion 14 and exposed to the environment at the proximal ends 52a and 52b (see FIG. 3). Secondly, the burner member 60 has a porosity that leads to gas (see FIG. 2). As a result of this arrangement, the gas provided at the proximal ends 52a and 52b of the mixing tubes 50a and 50b travels the mixing tube length until it is discharged into the cavity 24 at the distal ends 54a and 54b. Since the burner member 60 has a high porosity, a gas pressure gradient is created in the environment in the cavity 24 and the outer surface 64 so that the gas present in the cavity 24 diffuses from the burner member 60 toward the outer surface 64. Exists between.

  Fuel gas such as pressurized liquid gas (LPG) is supplied to the burner member 60 in the following manner. An LPG bottle (not shown) is rotated and connected to the inlet 30 as best shown in FIGS. 2 and 2A. In order to allow such a connection, the inlet 30 includes a threaded portion 32 and preferably conforms to the B-188 standard to ensure broad compatibility with gas bottle suppliers. Once securely connected, the probe 36 opens the valve of the LPG bottle and the pressurized gas moves through the probe 36 and into the chamber 26. The chamber 26 is entirely defined by an inlet accommodating portion 27 and a sheet 28. Inside the chamber 26 are a ball 29 and a compression spring 25. The compression spring 25 is given an outward urging force to the ball 29, and the translational movement is prevented by the seat 28 that reacts to the outlet container 31 via the thermal fuse body 38. The LPG fills both the chamber 26 and the region 26 ′, and is connected to the discharge pipe 40 through the port 39 so that fluid can be transmitted. The discharge pipe 40 then discharges the LPG to the adjustment device 42.

  A feature of the disclosed arrangement is that it is guided in the direction of a temperature LPG breaker that has the function of automatically shutting off the flow of gas from the container to the burner. As described briefly above and best illustrated in FIG. 2A, the sheet 28, which functions to prevent the ball 29 from extending, is in contact with the sealing surface 41. Similarly, the seat 28 in compression mode through a bias applied in the direction of the ball by the spring 25 reacts to the discharge vessel 31 via the thermal fuse 38. When the fuse 38 is no longer present, the sheet 28 is urged to translate from the compression spring 25, thereby allowing the ball 29 to approach the sealing surface 41, and the gas passage is further connected to the discharge tube. 40 is sealed. Therefore, the fuse 38 is designed at a general temperature or higher to prevent a potentially explosive condition that may intentionally occur during the phenomenon of "light back" or reverse combustion propagation. It is configured to release a general bond. The ultimate determination of the appropriate temperature is a matter of design. The disclosed embodiments contemplate temperature conditions between about 145 ° C. and 200 ° C. as candidate temperatures for temperature trips.

  Those having skill in the field will understand that there is a wide choice of candidate materials. Satisfactory results are obtained especially when ultra high molecular weight (UHMW) plastics or eutectic alloys are selected. The advantage of using eutectic alloys is the precise phase transition properties and the very rapid transition provided by them. This second feature is the importance of the burner for years of operation. This is because the thermal fuse is in a state of axial compression, and mechanical creep occurs particularly at a high temperature. This potentially reduces processing performance during normal times. An alloy that produces favorable results is comprised of 18.2% cadmium, 30.6% lead, and 51.2% tin. This alloy has a melting point of about 145 ° C. ± 1.5 ° C.

  Through the thermal fuse 38, the compressed gas is guided to the regulator and valve assembly 42 for pressure and volume adjustment. The control handle 44 provides functionality to the assembly 42 as understood by those having skill in the art. The conditioned gas is then guided to both gas jets 48a and 48b via distribution manifold 46, which in turn guides the fuel gas to mixing tubes 50a and 50b. If oxide uptake occurs in the oxygen-carrying air, it occurs in the injector and mix tube length by drawing air into the mix tube at openings 16a and 16b, which represent the only major opening in the pressure cavity 24. To move. Those skilled in the art will appreciate that other forms of oxide introduction may be implemented through similar or different structures. However, this embodiment represents an efficient and cost effective approach to the supply of combustible gas. The described method and associated structure is dependent on momentum transfer (the effect is achieved at openings 16a and 16b, creating a local low pressure, thereby taking in outside air to aid combustion). Mixing oxides and combustion gases is effectively obtained at low cost. Furthermore, since there are no moving parts, reliability and product life are increased.

  In order to optimize the introduction of air as oxidant and to minimize the influence of the environment (mainly wind in portable burner operation), the enclosure 14 is coaxially surrounded by a porous housing 18. As a result, a generally annular space is created between the enclosure 14 and the housing 18, and air is drawn into the openings 16a and 16b. In this way, any wind that affects the porous housing is diffused before entering the openings 16a and 16b.

  A mixture of fuel gas and oxide (pre-combustion gas) exists from the ends 54a and 54b of the mixing tubes 50a and 50b, enters the cavity 24, mixes statically and strikes the heat conducting post 56. As implied by its name, the static mixing and heat conducting post 56 has two functions. The post 56 is thermally connected to the base 12, heat is generated by the burner 10, and is conducted to the base 12 by radiation. Conduction and / or convection is partially removed by exposure between the post 56 and the next cold precombustion gas. Beneficially, this conduction of heat from the base 12 increases the heat capacity of the pre-combustion gas and promotes more effective combustion. The post 56 also functions to increase the mixing of the pre-combustion gas before combustion, and the uniform distribution of the pre-combustion gas by reducing the gas velocity so that the diffusion of the pre-combustion gas through the burner member 60 occurs more uniformly. To assist.

  As described above, during operation of the burner 10, the upper surface 64 of the burner member 60 where the pressure gradient is exposed to the outside environment and the lower surface 62 of the burner member 60 exposed to slightly pressurized pre-combustion gas. Exists between. After movement of the pre-combustion gas from the cavity 24 to the top surface 64, a piezoelectric igniter 66 known in the art is activated to initiate combustion of the pre-combustion gas. Upon ignition, the combustion travels just below the upper surface 64 of the burner member 60 and further propagation is prevented by the low heat transfer capacity and the small pores of the burner member 60. In this respect, the burner 10 is a radiant burner without a flame that convects so freely.

  The screen 20 is provided as a safety feature to prevent unintentional body contact and is provided to suit cooking utensils using heat exchangers as described in detail below. Both the screen 20 and the porous housing 18 are fixed to the burner 10 by means of a screen fixing ring 22. When maintenance of the burner is required, the user only needs to remove the fixing ring 22 in order to expose the upper surface 64 of the burner member 60 and remove the burner member 60 and the base 12.

  When a radiant burner represents a significant advance in thermal technology with regard to efficiency, safety and reliability, but is used in conjunction with a heat exchanger intended to be employed to extract maximum heat from the burner 10 Further progress is gained. As best shown in FIGS. 1 and 4-7, the heat exchanger 90 is integrated into a fuel container, more preferably a container or pot 70. The purpose of the heat exchanger is to effectively draw the heat generated by the burner 10 by utilizing it in combustion mode. In this regard, the mass flow rate and the temperature characteristics of the heat generated by the burner 10 are taken into account by the design of the heat exchanger 90.

  As shown in some of the drawings, the structure of the heat exchanger 90 can take many forms. The selection of the ultimate form from other forms is selected in consideration of the design based on the amount of the container 70, the characteristics of the heated gas, the hydrodynamic characteristics of the combustion gas, and similar factors. Thus, the illustrated embodiments are intended to illustrate several variations, but in no way represent a complete example of a heat exchanger that can be utilized. However, all of the illustrated embodiments attempt to optimize the surface area exposed to the radiant heat and the burner 10 combustion gases without significantly reducing the beneficial effects obtained through convective heating. Thus, the illustrated embodiment uses a plurality of channels with relatively unobstructed exit passages that maximize the distance that combustion gases must travel from the burner member 60 to the surrounding environment.

  Turning to FIG. 5A, a welded heat exchanger arrangement is shown. Here, a plurality of fin members 80 are formed independently of the pot 70, and subsequently by spot welding, brazing or similar heat treatment techniques to create a plurality of channels 86 through which the combustion gas travels, etc. Attached to the pot 70. The fin member 80 is preferably made of aluminum by stamping or similar mass production techniques. The fin member 80 is preferably located on the bottom surface 78 of the pot 70 and is formed in a spiral or involute pattern so that the time during which the combustion gas contacts the member is maximized. FIG. 5B shows a similar pattern of fin bodies 82 formed on the bottom surface 78 of the pot 70. However, the fin body 82 is integrated with the bottom surface 78. In this embodiment, the fin body 82 may form a suitable pattern for the bottom surface 78 by machining or during casting on the bottom surface. The thermal conductivity or overall durability from the fin body 82 to the pot 70 is higher than the thermal conductivity from the fin member 80 to the pot 70 because of the more robust combination of the former having the pot, but the manufacturing cost is high. Become.

  In addition to machining or casting methods to make a suitable fin body, the optimal means of producing a one-piece fin body is by impact extrusion. These steps are superior in thermal conductivity (than those made by casting), desirable surface finishes for cooking plates (better than casting or machining), better than those of casting or machining, and wasteful Are advantageous in terms of low weight and superior cost over machining or welding. Although there are size limitations by using these processes, there are no material limitations to form the elements normally used in backpacking cookware.

  Note that the bottom surface 78 need not be planar. Depending on the design requirements, the bottom surface 78 may be conical or frusto-conical with a vertex in the middle of the container. Such a shape not only advantageously modifies the combustion gas residence area during operation of the burner, but also other cooking utensils when used in combination with a burner such as the burner 10 having the screen 20. Would limit what would be properly integrated with the burner. Alternatively, a plurality of surface features, such as convex or concave features, can be provided in or on the bottom surface 78 to alter the combustion gases that can be discharged to the outside environment.

  The embodiment of FIG. 6 illustrates an ambient heat exchange arrangement that may be used as an integral part of the heat exchanger of FIGS. 5A and 5B, or used with other arrangements. By combining with a plurality of peripheral members 84 as shown in FIG. 7, for example, surrounding the pot 70 having such members, the wasteful heat present from the channel 86 acts on the peripheral members 84. Then, the direction is changed along the reduced diameter portion 74 of the pot 70. In this manner, an area added to the heat exchanger is formed in both peripheral members 84 and is not only directly coupled to the pot 70 but also thermally coupled to the heat exchanger 90. To prevent unintentional movement of fluid in the pot 70 from the heat exchanger 90, a drip ring 76 is provided on the reduced diameter portion 74.

FIG. 1 is a front view of an assembled burner and heat exchanger equipped with a pot system. FIG. 2 is a sectional view of the burner. FIG. 2A is a detailed cross-sectional view of a thermal fuse / trip used in the embodiment shown in FIG. FIG. 3 is a cross-sectional plan view of the burner of FIG. FIG. 4 is a cross-sectional front view of a first heat exchanger equipped with a pot. FIG. 5A is a perspective view of a first heat exchanger mounted on the pot, with fin members attached to the bottom of the pot and the vibe cover and ring removed for clarity. FIG. 5B is a perspective view of a first heat exchanger equipped with a pot, with the fin body integrated into the bottom of the pot during manufacture of the pot, with the cover and ring removed for clarity. The figure is a front cross-sectional view of a second heat exchanger installed in the pot, where the surrounding heat exchange ring is used to increase the surface available for heat conduction. FIG. 7 is a perspective view of a part of a surrounding heat exchange ring used in the carrying of FIG. 6.

Claims (4)

A fuel gas burner,
At least in part, having a cavity defined by an enclosure that does not allow combustion gas to permeate therethrough, and a burner member that allows the combustion gas to pass therethrough, having an inner surface exposed to the cavity and an outer surface exposed to the external environment. The surrounding portion that does not transmit combustion gas has at least one opening,
A mixing tube having a longitudinal axis and having first and second ends, wherein the first end seals at least one opening and the second end extends into the cavity;
A combustion gas injector at or near the first end for injecting combustion gas into the mixing tube, thereby introducing the combustion gas from the injector into the mixing tube and mixing the available oxidant with the mixing tube A combustion burner characterized in that a large amount of pressurized combustible gas is generated in the cavity and diffused from the inner surface of the burner member to the outer surface of the burner member.   The burner according to claim 1, wherein the burner member is made of a substantially combustible porous material.   The burner according to claim 2, wherein the combustible porous material is made of a foam metal.   2. The burner according to claim 1, further comprising a thermal fuse for closing the combustion gas passage between the combustion gas supply source and the combustion gas injector.

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