Patent Application
20180195717
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.
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 flamessuch 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.
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:
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
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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 H1 extending outward from a plane coincident with the groove floor 120 of an adjacent groove 112. In some embodiments, the maximum ridge height H1 is up to about 1 inch. In other embodiments, the maximum ridge height H1 is between about 0.15 inches and about 0.35 inches. In one embodiment, the maximum ridge height H1 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 R1 of less than about 1 inch. In other embodiments, the radius of curvature R1 is between about 7 mm and about 10 mm.
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The generally cylindrical burner apparatus 100 may also further include a cylinder length L3 and a cylinder diameter D3. Some embodiments ¢may include the cylinder length L3 being greater than the cylinder diameter D3. Other embodiments may include the cylinder diameter D3 being greater than the cylinder length L3. Still other embodiments may include the cylinder length L3 being equal to the cylinder diameter D3. The generally cylindrical burner apparatus 100 may further include a cylinder axis A1, and the ridges 110 and grooves 112 of the burner wall 104 may extend in a direction perpendicular to the cylinder length L3 and concentrically around the cylinder axis A1.
In embodiments including the non-active end cap 132b having convex and concave faces 135, 137, the end cap may extend a cap length L4 toward the base end 133 between about 0.1 times the cylinder diameter D3 and about 0.5 times the cylinder diameter. In some embodiments, the cap length L4 may be about 0.25 times the cylinder diameter D3.
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
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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.
