Patent Publication Number: US-11378273-B2

Title: Reduced resonance burner

Description:
BACKGROUND 
     The present disclosure relates generally to a premix burner (combustion air and gas are mixed prior to entering the burner) for burning a combustible gas mixture. 
     Premix burners allowing for burning of a combustible gas mixture are known in the art. These premix burners, however, may include a burner surface or a burner support structure that allows an excessive noise level to be created when in operation. This effect can be further accentuated when the premix burner is contained within a small combustion chamber volume wherein all the energy causing the noise levels cannot dissipate within the volume. In such applications, the noise levels can be transmitted beyond the combustion chamber in varying oscillating wave forms that are audible and usually objectionable 
     What is needed, therefore, is an improved burner construction which would eliminate or greatly reduce the noise level inherent in operating a premix burner. 
     BRIEF SUMMARY 
     Briefly, the present disclosure relates, in one embodiment, to a burner apparatus for burning a gas and air mixture. The burner apparatus may include a burner wall having a plurality of ridges and a plurality of grooves. Each groove may be defined between adjacent ridges. Each groove may also include a pair of slopes. Each slope may have an area of permeability having openings defined therein from which flames can project. Each ridge may define an area of reduced permeability relative to the areas of permeability of the slopes. 
     An alternative embodiment includes each area of reduced permeability of the ridges being less than half as permeable as the area of permeability of each slope. 
     Still another embodiment includes the area of reduced permeability of each ridge including no openings defined therein. 
     Yet another embodiment includes the openings defined in the slopes including a row of openings defined in each slope. The row of openings may be defined along a line extending in a direction generally parallel to a respective groove. 
     Another embodiment includes each pair of slopes including opposing rows of openings. Each opening on a given slope may be aligned with a corresponding opening on a respective opposing slope along a line extending in a direction generally perpendicular to the respective groove. 
     In a further embodiment, the openings defined in the slopes are configured to project the flames in a direction extending above an opposing slope and respective ridge. 
     A further still embodiment includes adjacent openings being less than about 10 cm from center to center. 
     Yet another embodiment includes the openings defined in each slope configured to project the flames such that a noise cancelling effect is achieved with destructive pressure wave interference created by the flames. 
     Still another embodiment includes the openings each including an opening diameter of less than about 1 cm. 
     An even further embodiment includes the burner wall having an outer surface. A flexible foraminous material may be disposed on the outer surface of the burner wall. 
     Another embodiment includes the foraminous material affixed to the burner wall such that the foraminous material closely follows the shape of the burner wall. 
     One embodiment includes the foraminous material spot welded to the burner wall. 
     A further embodiment includes the burner wall being generally cylindrical. 
     A further still embodiment includes the generally cylindrical burner wall having an end cap. The end cap may include ridges and grooves defined between adjacent ridges. 
     An even further embodiment includes the ridges and the grooves defined in the end cap forming concentric circles. 
     Yet another embodiment includes the generally cylindrical burner wall including a non-active end cap. 
     Still another embodiment includes the generally cylindrical burner including a base end and the non-active end cap including a curved end cap. The curved end cap may have a convex face facing toward the base end of the generally cylindrical burner. 
     The present disclosure also relates, in one embodiment, to a burner apparatus for burning a gas and air mixture. The burner apparatus may include a cylindrical burner wall. The cylindrical burner wall may have a plurality of ridges and a plurality of grooves. Each groove may be defined between adjacent ridges. A first group of openings may be defined in the cylindrical burner wall. Each opening of the first group of openings may be configured to allow a respective first flame to project therefrom, thereby producing first flame pressure waves. A second group of openings may also be defined in the cylindrical burner wall. Each opening of the second group of openings may be configured to allow a respective second flame to project therefrom, thereby producing second flame pressure waves. The first group of openings and the second group of openings may be oriented such that the first flame pressure waves and the second flame pressure waves destructively interfere with each other to reduce noise. 
     A further embodiment includes the cylindrical burner wall further having a cylinder length. The ridges and the grooves may alternate along the cylinder length. 
     Another embodiment includes the cylindrical burner wall further including a cylinder axis. Each of both the ridges and the grooves may extend in a direction that is perpendicular to the cylinder length and concentrically around the cylinder axis. 
     Still another embodiment includes the cylindrical burner wall having an end cap. 
     Yet another embodiment includes the end cap having a plurality of end cap ridges and a plurality of end cap grooves. Each end cap groove may be defined between adjacent end cap ridges. The end cap ridges and the end cap grooves may form concentric circles. 
     A further embodiment includes the end cap including a substantially non-active end cap having a concave outer face. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of one embodiment of the burner apparatus. 
         FIG. 2  is a side cross-sectional elevation view of the burner apparatus of  FIG. 1 . 
         FIG. 3  is a side cross-sectional elevation view of another embodiment of the burner apparatus having a different end cap. 
         FIG. 4  is a perspective view of another embodiment of the burner apparatus. 
         FIG. 5  is a side cross-sectional elevation view of the burner apparatus of  FIG. 4 . 
         FIG. 6  is a detailed side cross-sectional elevation view of a burner wall of the burner apparatuses of both  FIGS. 1, 3, and 4 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments of the present disclosure, one or more drawings of which are set forth herein. Each drawing is provided by way of explanation of the present disclosure and is not a limitation. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the teachings of the present disclosure without departing from the scope of the disclosure. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. 
     Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents. Other objects, features, and aspects of the present disclosure are disclosed in, or are obvious from, the following detailed description. It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only and is not intended as limiting the broader aspects of the present disclosure. 
     Sound is created by any cyclical pressure variation in an elastic medium, such as a gas, liquid, or solid. The audible frequency for most humans is in the range of 10 Hz to 16 KHz. 
     In a burner, sudden, rhythmic expansion and contraction of hot gases in an oscillating flame front can generate sound. The “flame front” is defined as the leading edge of the flame, which is the place where combustion stops and becomes hot exhaust product. In such an oscillating system, the flame front acts similarly to a speaker diaphragm. So, just as with a speaking diaphragm, the sound intensity increases as the area of the burner media or “diaphragm” increases. In a burner allowing for excessive resonant flame fronts, the sound waves can re-enforce each other should they get in synchronous motion, and create an unacceptably loud noise level. 
     In dealing with noises of any type, including the burner noise of the type just described, the designer can provide means to:
         a. absorb or attenuate the energy of the wave form leaving the burner surface by using a muffling device,   b. disperse the energy wave forms at the surface of the burner into non-synchronous wave forms of varying energy pulsations by using tooling techniques and additional internal parts within the burner.   c. Eliminate the source of the noise by cancellation. This solution is particularly desirable as it eliminates the problem at the source.       

     There are a number of variables that can contribute to oscillatory flame noise. These variables include, but are not limited to, the type of fuel used, the burner firing rate, the burner size and shape, the firing intensity per unit area, the pressure drop across the burner, the flame shape and size, the fuel to air ratio, the fuel to air mixedness, and the aerodynamics of the combustion chamber. 
     The present disclosure illustrates and describes a manner of cancellation by eliminating or greatly reducing oscillatory burner noise. 
     As shown in the Figures, a burner apparatus  100 ,  200  may receive a mixture  102  of combustion air and gas which then exits the burner wall  104  to allow flames  106  to project therefrom. The burner apparatus  100 ,  200  may be of any appropriate shape. As shown in  FIGS. 1-3 , the burner apparatus  100  may be a generally cylindrical burner apparatus. In  FIGS. 4 and 5 , a generally planar burner apparatus  200  is shown. The materials of construction of the burner apparatus  100 ,  200  may be of any appropriate material that is either a rigid or a flexible heat resistant material. One suitable material for use as the burner wall  104  may be stainless steel that has been bent or formed into an appropriate shape, such as those shown in the Figures. Another suitable material may be a porous ceramic material formed in the requisite shape. 
     Referring now to  FIGS. 1 and 4 , a burner apparatus  100 ,  200  is shown. The burner apparatus  100 ,  200  may include a burner wall  104 . In some embodiments, the burner wall may comprise a plurality of ridges  110  and a plurality of grooves  112 . Each groove  112  may be defined between adjacent ridges  110 . The grooves  112  may each include slopes  114  such that a pair of the slopes is included with each groove. Each slope  114  may include an area of permeability  116  having openings  118  defined therein. As can best be seen in  FIG. 6 , flames  106  may project from each of the openings  118 . 
     As shown in  FIGS. 1 and 4 , the openings  118  defined in the slopes  114  may include a row of openings defined in each slope along a line L 1  extending in a direction generally parallel to a respective groove  112 . In some embodiments, each pair of slopes  114  includes opposing rows of openings  118  such that each opening on a given slope is aligned with a corresponding opening on a respective opposing slope along a line L 2  extending in a direction generally perpendicular to the respective groove  112 . As shown in  FIG. 6 , some embodiments include the openings  118  defined in each slope  114  configured to project the flames  106  in a direction extending above an opposing slope and respective ridge  110 . In many embodiments, the openings  118  defined in the slopes  114  are configured to project the flames  106  such that a noise cancelling effect is achieved with destructive pressure wave interference created by the flames. Returning to  FIGS. 1 and 4 , the openings  118  may have a center to center distance D 1  of less than about 10 cm in some embodiments. This distance D 1  may be measured along the line L 1  in many embodiments. Other embodiments may include a center to center distance D 1  of between about 0.5 cm and 1.5 cm. One embodiment may include a center to center distance D 1  of 1 cm. The openings  118  in some embodiments may also include an opening diameter D 2  of less than about 1 cm. Other embodiments may include an opening diameter D 2  of between about 1 mm and 5 mm. One embodiment may include an opening diameter D 2  of about 3 mm. 
     As can best be seen in  FIGS. 2, 3, and 5 , the grooves  112  may each include a groove floor  120 . The groove floor  120  may include a substantially flat portion  122  defined between adjacent slopes  114 . One embodiment may include the substantially flat portion  122  having a flat portion width W 1  of up to about 0.5 inches. Another embodiment may include the substantially flat portion  122  having a flat portion width W 1  of from about 0.15 inches to 0.35 inches. Still another embodiment may include the substantially flat portion  122  having a flat portion width W 1  of about 0.25 inches. Other embodiments may include the groove floor  120  including a substantially curved floor. 
     Each of the plurality of ridges  110  may define an area of reduced permeability  124  relative to each area of permeability  116  of the slopes  114 . Each area of reduced permeability  124  may be less than half as permeable as the area of permeability on a respective slope  114 . In some embodiments, the area of reduced permeability  124  includes no openings  118  defined therein. In some embodiments, the areas of reduced permeability  124  may each functionally establish a barrier between respective adjacent grooves  112 . In one embodiment, the barrier may be a complete barrier. Other embodiments may include only a partial barrier such that the area of reduced permeability  124  includes substantially fewer openings  118  defined therein compared to the area of permeability  116 . The ridges  110  may be of any appropriate dimensions. One embodiment includes the ridges  110  having a maximum ridge height H 1  extending outward from a plane coincident with the groove floor  120  of an adjacent groove  112 . In some embodiments, the maximum ridge height H 1  is up to about 1 inch. In other embodiments, the maximum ridge height H 1  is between about 0.15 inches and about 0.35 inches. In one embodiment, the maximum ridge height H 1  is about 0.25 inches. Each ridge  110  may include a curved ridge portion  126 . In some embodiments, the curved ridge portion  126  may include a radius of curvature R 1  of less than about 1 inch. In other embodiments, the radius of curvature R 1  is between about 7 mm and about 10 mm. 
     As shown in  FIGS. 2-4 , the burner wall  104  includes an outer surface  128  that may optionally include a flexible foraminous material  130  disposed thereon. In many embodiments, the foraminous material  130  is affixed to the burner wall  104  such that the foraminous material closely follows the shape of the burner wall. The foraminous material  130  may also closely follow the shape of the outer surface  128 . In some embodiments, the foraminous material  130  is spot welded to the outer surface  128  of the burner wall  104 . There are several materials commercially available that comprise a woven or sintered fabric of metal fibers having a thickness of approximately ⅛″. Other suitable flexible heat resistant materials include ceramic weaves and other alloy meshes. A fabric constructed of rock fiber could also be utilized. The foraminous material  130  as shown in  FIGS. 2-4  only covers a small portion of the burner wall  104 . This configuration is for illustration purposes, and the foraminous material  130  would preferably cover the majority of the outer surface  128 . Some embodiments may include the foraminous material  130  covering all or substantially all of the outer surface  128 . 
     With regard to  FIGS. 1-3  showing embodiments of the burner apparatus  100  that are generally cylindrical, the burner wall  104  may be connected to an end cap  132 . Stated another way, the burner wall  104  may include an end cap  132 . As illustrated in  FIGS. 1 and 2 , some embodiments of the generally cylindrical burner apparatus  100  may include an end cap  132   a  having ridges  110 , or end cap ridges, and grooves  112 , or end cap grooves. The end cap  132   a  may further include a plurality of openings  118  in the areas of permeability  116  as described above. As mentioned above, the grooves  112  may be defined between adjacent ridges  110 . The ridges  110  and grooves  112  defined in the end cap  132   a  may form concentric circles. The grooves  112  of the end cap  132   a  may be substantially the same as, or may be different from, the grooves of the burner wall  104 . 
     As illustrated in  FIG. 3 , however, other embodiments of the generally cylindrical burner apparatus  100  may include an end cap  132   b  that is substantially non-active, or substantially devoid of openings  118 . Some openings  118  may be defined in the substantially non-active end cap  132   b . At least one embodiment of a non-active end cap  132   b  may have no openings  118  defined therein. In many embodiments, the generally cylindrical burner apparatus  100  may include a base end  133 . The non-active end cap  132   b  may be a curved end cap having a convex face  135  and a concave face  137  opposite the convex face. In some embodiments, the convex face  135  may be facing toward the base end  133  of the generally cylindrical burner apparatus  100 . Stated another way, the convex face  135  may face toward the base end  133  of the generally cylindrical burner apparatus  100 . Stated yet another way, the substantially non-active end cap  132   b  may include a concave outer face  137 . In embodiments including the non-active end cap  132   b  having the convex face  135  and the concave face  137 , the end cap may be connected to the burner wall  104  in any appropriate manner. The non-active end cap  132   b , in some embodiments, may further include a substantially flat portion  139  to facilitate attachment to the burner wall  104 . Embodiments of the generally cylindrical burner apparatus  100  including a substantially non-active end cap  132   b  having the convex face  135  facing the base end  133  may allow for the gas and air mixture  102  to form at least some flow paths F 1  that may be redirected by the end cap toward the burner wall  104 . The redirection of these flow paths F 1  may reduce the temperatures in and/or around the substantially non-active end cap  132   b , thereby reducing stress and fatigue in the materials forming at least one of the end cap and the burner wall  104 . 
     The generally cylindrical burner apparatus  100  may also further include a cylinder length L 3  and a cylinder diameter D 3 . Some embodiments may include the cylinder length L 3  being greater than the cylinder diameter D 3 . Other embodiments may include the cylinder diameter D 3  being greater than the cylinder length L 3 . Still other embodiments may include the cylinder length L 3  being equal to the cylinder diameter D 3 . The generally cylindrical burner apparatus  100  may further include a cylinder axis A 1 , and the ridges  110  and grooves  112  of the burner wall  104  may extend in a direction perpendicular to the cylinder length L 3  and concentrically around the cylinder axis A 1 . 
     In embodiments including the non-active end cap  132   b  having convex and concave faces  135 ,  137 , the end cap may extend a cap length L 4  toward the base end  133  between about 0.1 times the cylinder diameter D 3  and about 0.5 times the cylinder diameter. In some embodiments, the cap length L 4  may be about 0.25 times the cylinder diameter D 3 . 
     Another embodiment of a cylindrical burner apparatus  100  may include a burner wall  104  having a cylindrical shape. The burner wall  104  may include a plurality of ridges  110  and grooves  112 . Each groove  112  may be defined between adjacent ridges  110 . A first group  134  of the openings  118  may be defined in the burner wall  104 . As best shown in  FIG. 6 , each opening  118  of the first group  134  may be configured to allow a respective first flame  136  to project therefrom. First flame pressure waves  138  may thereby be produced. A second group  140  of the openings  118  may also be defined in the burner wall  104 . Each opening  118  of the second group  140  may be configured to allow a respective second flame  142  to project therefrom. Second flame pressure waves  144  may thereby be produced. The first group  134  of the openings  118  and the second group  140  of the openings may be oriented such that the first flame pressure waves  138  and the second flame pressure waves  144  destructively interfere with each other to reduce noise. 
     As shown in  FIGS. 1 and 4 , the first group  134  may form a first row of the openings  118 , and the second group  140  may form a second row of the openings. As can best be seen in  FIG. 6 , the groups  134 ,  140  of openings  118  may be oriented such that the general direction of the first flame pressure waves  138  and the general direction of the second flame pressure waves  144  intersect in a manner creating the destructive noise interference. 
     Returning to  FIGS. 1-3 , the burner wall  104  of the cylindrical burner apparatus  100  may include the ridges  110  and grooves  112  alternating along the cylinder length L 3  of the burner apparatus. This alternating pattern may include ridges  110  and grooves  112  that are angled relative to the cylinder axis A 1  and therefore twist around the cylinder axis such that the burner apparatus  100  resembles something similar to a barber shop pole in some embodiments. Other embodiments may include each of the ridges  110  and each of the grooves  112  extending in a direction perpendicular to the cylinder length L 3  and concentrically around the cylinder axis A 1  of the burner apparatus  100 . Still other embodiments of the burner apparatus  100  may include the ridges  110  and the grooves  112  extending in a direction parallel to the cylinder axis A 1 . The end cap  132  may optionally be provided along with the burner wall  104 . In some embodiments including an end cap  132   a , ridges  110  and grooves  112  may also be provided on the end cap, also respectively called end cap ridges and end cap grooves. In many embodiments, the end cap ridges  110  and end cap grooves  112  may form concentric circles. These concentric circles may be concentric around the cylinder axis A 1 , for instance. In other embodiments including a substantially non-active end cap  132   b , the end cap may include a concave outer face  137 . 
     With reference to  FIGS. 4 and 5 , the burner apparatus  200  may also be generally planar. In such an embodiment, the burner apparatus  200  may include a burner wall  104  having horizontally, vertically, or diagonally extending parallel ridges  110  and grooves  112 . Any appropriate orientation is also contemplated. These orientations and configurations include, but are not limited to, ridges  110  and grooves  112  that are circular, square, lines oriented in a series of rows, and the like. As with the generally cylindrical burner apparatus  100 , the generally planar burner apparatus  200  may include any appropriate number of ridges  110  and grooves  112 . 
     This written description uses examples to disclose the invention and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims. 
     Although embodiments of the disclosure have been described using specific terms, such description is for illustrative purposes only. The words used are words of description rather than limitation. It is to be understood that changes and variations may be made by those of ordinary skill in the art without departing from the spirit or the scope of the present disclosure, which is set forth in the following claims. In addition, it should be understood that aspects of the various embodiments may be interchanged in whole or in part. While specific uses for the subject matter of the disclosure have been exemplified, other uses are contemplated. Therefore, the spirit and scope of the appended claims should not be limited to the description of the versions contained herein.