Flame arrestor assembly for a gas water heater appliance

Abstract

A gas water heater appliance includes a tank for storage of water for heating, a combustion chamber wall positioned below the tank and defining a combustion chamber and a pilot air inlet, a gas burner positioned within the combustion chamber to heat the water in the tank, and an arrestor assembly mounted to the combustion chamber wall above the pilot air inlet and below the gas burner. The arrestor assembly includes a flame arrestor and a restrictor plate positioned adjacent the flame arrestor, the restrictor plate defining a bottom of the combustion chamber and comprising one or more apertures that provide fluid communication between the pilot air inlet and the combustion chamber.

Description

FIELD OF THE DISCLOSURE

[0001] The present subject matter relates generally to water heater appliances, and more particularly to combustion assemblies for gas water heaters.BACKGROUND OF THE DISCLOSURE

[0002] Water heater appliances utilize a variety of energy sources to create hot water in commercial and residential settings, the energy sources including electric, solar, and various fuels. For example, natural gas and propane are preferred by some customers due to, for example, the relatively quick heating rate. These fuels are supplied as a gas that is burned in a combustion chamber to provide heat energy to raise the water temperature.

[0003] A conventional unpowered gas water heater may include a standing pilot light that will ignite the main gas burner when a call for heat is required. This combustion system may be a partially pre-mixed gas system. In this regard, the primary combustion air comes directly from the outside environment through a venturi located at the combustion chamber door and the secondary air for the pilot comes through the wrapper.

[0004] Notably, gas water heater appliances are commonly subject to strict emissions standards or other government regulations. For example, nitrogen oxides (NOx) emissions are often regulated by governments and municipalities, e.g., such that they must be lower than 10 nanograms per joule. In order to meet these emissions standards, the flow of secondary air needs to be restricted to create a more fuel rich mixture which decreases flame temperature and reduces NOx emissions. However, introducing such a restriction may cause an audible sound (i.e., combustion noise) that osculates at 1300 Hertz or may result in pilot flame instability.

[0005] Accordingly, a gas water heater with features for reduced NOx emissions is desirable. More specifically, a gas water heater with improved pilot light stability, reduced noise, and improved operation would be particularly beneficial.BRIEF DESCRIPTION OF THE DISCLOSURE

[0006] Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

[0007] In one exemplary embodiment, a gas water heater appliance is provided including a tank for storage of water for heating, a combustion chamber wall positioned below the tank and defining a combustion chamber and a pilot air inlet, a gas burner positioned within the combustion chamber to heat the water in the tank, and an arrestor assembly mounted to the combustion chamber wall above the pilot air inlet and below the gas burner. The arrestor assembly includes a flame arrestor and a restrictor plate positioned adjacent the flame arrestor, the restrictor plate defining a bottom of the combustion chamber and comprising one or more apertures that provide fluid communication between the pilot air inlet and the combustion chamber.

[0008] In another exemplary embodiment, an arrestor assembly for a gas water heater is provided. The gas water heater includes a combustion chamber and the arrestor assembly includes a flame arrestor and a restrictor plate positioned adjacent the flame arrestor, the restrictor plate defining a bottom of the combustion chamber and comprising one or more apertures that provide fluid communication between a pilot air inlet and the combustion chamber.

[0009] These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures.

[0011] FIG. 1 provides a partially cut away, side view of a water heater according to an example embodiment of the present subject matter.

[0012] FIG. 2 provides a schematic of a gas flow control system as may be used with the example water heater of FIG. 1.

[0013] FIG. 3 provides a perspective view of a combustion assembly of the example water heater of FIG. 1 according to an example embodiment of the present subject matter.

[0014] FIG. 4 provides a cross-sectional view of the example combustion assembly of FIG. 3 according to an example embodiment of the present subject matter.

[0015] FIG. 5 provides a top, perspective view of an arrestor assembly of the example combustion assembly of FIG. 3 according to an example embodiment of the present subject matter.

[0016] FIG. 6 provides a bottom, perspective view of the example arrestor assembly of FIG. 5 according to an example embodiment of the present subject matter.

[0017] FIG. 7 provides an exploded view of the example arrestor assembly of FIG. 5 according to an example embodiment of the present subject matter.

[0018] FIG. 8 provides a close-up, perspective view of the example arrestor assembly of FIG. 5 according to an example embodiment of the present subject matter.

[0019] FIG. 9 provides a cross-sectional view of the example arrestor assembly of FIG. 5 according to an example embodiment of the present subject matter.

[0020] FIG. 10 provides a perspective view of a restrictor plate of the example arrestor assembly of FIG. 5 according to an example embodiment of the present subject matter.

[0021] Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention.DETAILED DESCRIPTION

[0022] Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the invention. 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 invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

[0023] As used herein, the terms “first,”“second,” and “third” may be used interchangeably to distinguish one element or component from another and are not intended to signify location or importance of the individual elements or components. The terms “includes” and “including” are intended to be inclusive in a manner similar to the term “comprising.” Similarly, the term “or” is generally intended to be inclusive (i.e., “A or B” is intended to mean “A or B or both”). In addition, here and throughout the specification and claims, range limitations may be combined or interchanged. Such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. The singular forms “a,”“an,” and “the” include plural references unless the context clearly dictates otherwise.

[0024] Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “generally,”“about,”“approximately,” and “substantially,” are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value, or the precision of the methods or machines for constructing or manufacturing the components or systems. For example, the approximating language may refer to being within a 10 percent margin (i.e., including values within ten percent greater or less than the stated value). In this regard, for example, when used in the context of an angle or direction, such terms include within ten degrees greater or less than the stated angle or direction (e.g., “generally vertical” includes forming an angle of up to ten degrees in any direction, such as, clockwise or counterclockwise, with the vertical direction V).

[0025] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” In addition, references to “an embodiment” or “one embodiment” does not necessarily refer to the same embodiment, although it may. Any implementation described herein as “exemplary” or “an embodiment” is not necessarily to be construed as preferred or advantageous over other implementations. Moreover, each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the invention.

[0026] Except as explicitly indicated otherwise, recitation of a singular processing element (e.g., “a controller,”“a processor,”“a microprocessor,” etc.) is understood to include more than one processing element. In other words, “a processing element” is generally understood as “one or more processing element.” Furthermore, barring a specific statement to the contrary, any steps or functions recited as being performed by “the processing element” or “said processing element” are generally understood to be capable of being performed by “any one of the one or more processing elements.” Thus, a first step or function performed by “the processing element” may be performed by “any one of the one or more processing elements,” and a second step or function performed by “the processing element” may be performed by “any one of the one or more processing elements and not necessarily by the same one of the one or more processing elements by which the first step or function is performed.” Moreover, it is understood that recitation of “the processing element” or “said processing element” performing a plurality of steps or functions does not require that at least one discrete processing element be capable of performing each one of the plurality of steps or functions.

[0027] Referring now to the figures, FIG. 1 illustrates a partial sectional, side view of an exemplary water heater 100 of the present invention. FIG. 2 provides a schematic of a gas flow control system as may be used with the example water heater of FIG. 1. According to the illustrated embodiment, water heater 100 includes a tank 102 that extends along a vertical direction V between a top wall 104 and a bottom wall 106. Tank 102 defines a generally cylindrical reservoir where water (e.g., identified generally by reference numeral 108) is supplied for heating and storage. Specifically, cool water 108 may be supplied into tank 102 by an inlet line 110 where it is heated before being discharged through an outlet line 112. According to an example embodiment, inlet line 110 and outlet line 112 are fluidly coupled to top wall 104 of tank 102 by one or more fluid connections, though other fluid supply / return configurations are possible and within the scope of the present subject matter.

[0028] Specifically, during operation of water heater 100, water 108 from an external water supply 114 travels through inlet line 110 and fills tank 102. Specifically, water heater 100 may include a cold water dip tube 116 that extends along vertical direction V towards bottom wall 106 of tank 102. As described in more detail below, water 108 within tank 102 may be heated by combusting a fuel (e.g., natural gas or propane), and the heated water 108 may be stored in tank 102 until demanded by a consumer, e.g., by opening a water consuming device such as an external fixture 118. In this regard, external fixtures 118 may include valves, faucets, appliances, or other water consuming devices fluidly coupled to water heater 100 through a water supply system of a residential or a commercial structure. Thus, when heated water 108 is requested by an external fixture 118, heated water travels upward through outlet line 112 where it is supplied to the external fixture 118 through one or more conduits or pipes of the water supply system.

[0029] To heat water 108 within tank 102, water heater 100 includes a combustion assembly 130 that burns a fuel or fuel mixture, e.g., including propane, natural gas, etc. Specifically, combustion assembly 130 includes a combustion chamber 132 positioned below bottom wall 106 of tank 102 in which a gas burner 134 is centrally located. Gas burner 134 is supplied with a gaseous fuel (e.g., propane or natural gas) from a gas supply line 136 including one or more flow regulating valves (e.g., such as a gas valve 138 as shown in FIG. 2). The gas is directed into a venturi 140, and in the process, ambient air is drawn in through a combustion air inlet 142 where it is entrained with the fuel to create a fuel / air mixture that is injected into gas burner 134 through the venturi 140. The resulting mixture of air and gas is ignited and burned by gas burner 134 to heat bottom wall 106 of tank 102 and the water 108 contained within tank 102.

[0030] Hot combustion gas may be exhausted from combustion chamber 132 through a vent or flue 144 centrally located within tank 102. Heat exchange with flue 144 also helps heat water 108 in tank 102. A baffle 146 may further promote this heat exchange between combustion gases and water 108. Gas exits water heater 100 though a vent hood 148, which may be connected with additional vent piping (not shown) to eject the combustion gases to an external environment.

[0031] According to example embodiments, water heater 100 may further include an anode rod 150 that provides protection against corrosion attacks on tank 102 and other metal components of water heater 100. In addition, a pressure relief valve 152 provides for a release of water from tank 102 in the event the pressure rises above a predetermined amount. Other safety features may be included while remaining within the scope of the present subject matter.

[0032] A thermostat 154 may be positioned within tank 102 to measure the temperature of water 108 in tank 102 and provide a signal to gas control valve module 156. As used herein, “a signal” is not limited to a single measurement of temperature and, instead, may include multiple measurements over time or continuous measurements over time. The signal may be provided through, for example, changes in current, voltage, resistance, or others. Depending upon whether the desired temperature has been reached as determined (e.g., from the signal from thermostat 154), gas control valve module 156 regulates the flow of gas to gas burner 134 through gas supply line 136.

[0033] Referring now to FIG. 2, combustion chamber 132 is formed by a chamber wall 160 that at least partially encloses combustion chamber 132 and may also provide support for tank 102 along a top edge 162. As shown, chamber wall 160 encircles combustion chamber 132 and is spaced apart from gas burner 134. In addition, water heater 100 may include an outer skirt or a cabinet 164 that surrounds both combustion chamber wall 160 and tank 102, though it should be appreciated that these features may alternatively be formed as part of cabinet 164. As illustrated for example in FIG. 1, cabinet 164 may define an air intake 166 for supplying ambient air that facilitates operation of water heater 100.

[0034] As shown, water heater 100 includes a pilot burner 170 that provides a pilot light 172 to ignite a mixture of air and fuel at gas burner 134 when a gas valve (e.g., as part of gas control valve module 156 or provided as a separate component) is open. An igniter 174 is positioned adjacent to pilot burner 170 and generates a spark used to ignite gaseous fuel and provide pilot light 172. Gaseous fuel for pilot burner 170 is supplied by a pilot burner fuel line 176. Gas valve control module 156 may control the flow of gaseous fuel through pilot burner fuel line 176 and the flow of gas to gas burner 134 through gas supply line 136. Alternatively, a dedicated pilot valve may be used to regulate the flow of gas to pilot burner 170.

[0035] In certain embodiments, gas valve control module 156 includes at least one controller 180. By way of example, controller 180 may include memory and one or more processing devices such as microprocessors, CPUs or the like, such as general or special purpose microprocessors operable to execute programming instructions or micro-control code associated with operation of water heater 100 as further described herein. The memory can represent random access memory such as DRAM, or read only memory such as ROM or FLASH. The processor executes programming instructions stored in the memory. The memory can be a separate component from the processor or can be included onboard within the processor. Alternatively, controller 180 may be constructed without using a microprocessor (e.g., using a combination of discrete analog or digital logic circuitry—such as switches, amplifiers, integrators, comparators, flip-flops, AND gates, and the like) to perform control functionality instead of relying upon software.

[0036] In some embodiments, a chamber sensor 182, which is generally configured to detect temperature, is positioned at, on, or adjacent to the combustion chamber 132. For instance, chamber sensor 182 may be attached to chamber wall 160 (e.g., supported thereon). As shown, chamber sensor 182 may be disposed, at least in part, within combustion chamber 132. Generally, chamber sensor 182 may be any suitable temperature sensor (e.g., thermocouple, thermistor, IR sensor, etc.) configured to detect a temperature within combustion chamber 132. For instance, an output voltage from chamber sensor 182 may be proportional to the temperature within the combustion chamber 132 or at chamber sensor 182. The voltage signal transmitted to controller 180 (e.g., and may be interpreted thereby) through conductors may thus represent representing the measured chamber temperature.

[0037] Further separate from or in addition to chamber sensor 182, water heater 100 may include an ambient sensor 184. Ambient sensor 184 may be spaced apart from chamber sensor 182. In some embodiments, ambient sensor 184 is attached to tank 102, such as indirectly or through the gas valve control module 156 (e.g., such that the ambient sensor 184 is generally fixed relative to the tank 102). For instance, ambient sensor 184 may be disposed within gas valve control module 156 on or in operable (e.g., electrical or wireless) communication with controller 180. Generally, ambient sensor 184 is configured to detect temperature outside of combustion chamber 132 (e.g., directly or indirectly). In some such embodiment, ambient sensor 184 includes or is provided as a suitable temperature sensor (e.g., thermocouple, thermistor, IR sensor, etc.) configured to detect temperate outside of combustion chamber 132. The voltage signal from ambient sensor 184 may be transmitted to controller 180 (e.g., and may be interpreted thereby). In additional or alternative embodiments, ambient sensor 184 communicates (e.g., wirelessly) with a separate probe or database (e.g., weather station) to receive an ambient temperature value detected apart from the tank 102 or water heater 100 generally.

[0038] In exemplary embodiments, water heater 100 includes gas valve 138 positioned along gas supply line 136. According to example embodiments, gas valve 138 may be incorporated as part of gas control valve module 156 or may be a separate component. Controller 180 is in communication with gas valve 138 to control the flow of gas therethrough by determining when gas valve 138 is energized. For this exemplary embodiment, gas valve 138 may operate so that when energized, gas valve 138 is fully open to allow a flow of gaseous fuel to gas burner 134. When not fully energized, gas valve 138 is fully closed (i.e. a “fail-closed” type valve) so as to prevent the flow of gaseous fuel to gas burner 134.

[0039] During use, opening or closing of gas valve 138 may generally be directed or controlled by controller 180. For instance, gas valve 138 may be directed to the open position to create a flame at gas burner 134. Controller 180 may receive one or more signals (e.g., from thermostat 154) to determine whether the temperature of water in tank 102 has reached a desired setpoint temperature. In response to the same, the controller 180 may direct the gas valve 138 to the closed position. In some embodiments, an open interval (i.e., time period in which gas valve 138 is continuously opened or a flame is generated) may be demarcated or observed as a single cycle.

[0040] Referring now also to FIGS. 3 through 10, aspects of combustion assembly 130 will be described in more detail according to example embodiments of the present subject matter. More specifically, aspects of the present subject matter are generally directed to an arrestor assembly 200 for use with combustion assembly 130 to address various problems described herein. Specifically, arrestor assembly 200 may be mounted to the combustion chamber wall 160 and generally defines a bottom boundary of combustion chamber 132. According to the illustrated embodiment, combustion chamber wall 160 may generally define a pilot air inlet 202, e.g., which may include a plurality of perforations or apertures defined around a circumference of a bottom of combustion chamber wall 160. In general, arrestor assembly 200 may be positioned above pilot air inlet 202 and below gas burner 134 within combustion assembly 130.

[0041] According to the illustrated embodiment, arrestor assembly 200 may generally include a flame arrestor 210 and a restrictor plate 212 positioned adjacent flame arrestor 212 and defining a bottom of combustion chamber 132. Specifically, according to the example embodiment, flame arrestor 210 is positioned below restrictor plate 212 and is generally configured to allow free passage of air and / or gases while preventing a flame from traveling therethrough. For example, flame arrestor 212 may be a mesh screen, a perforated plate, or any other structure that defines a plurality of small passages through which gases may flow while the passage of flames is prevented. For example, as shown schematically in FIGS. 8 and 9, a flow of pilot air 214 may pass through flame arrestor 210, as described in more detail below.

[0042] Specifically, restrictor plate 212 may define one or more apertures 216 that provide fluid communication between pilot air inlet 202 and combustion chamber 132. According to the illustrated embodiment, apertures 216 are defined on a raised embossment 218 of restrictor plate 212. In this regard, raised embossment 218 may be defined in the center of restrictor plate 212 for directing the flow of pilot air 214 toward pilot burner 170. In this regard, for example, raised embossment 218 may be positioned directly below pilot light 172 for supporting combustion of pilot burner 170.

[0043] Notably, as explained briefly above, supplying pilot air 214 only through apertures 216 may generate audible sounds and / or may generate pilot flame instability, resulting in the potential failure of water heater 100 and consumer dissatisfaction. Specifically, combustion noise may oscillate at approximately 1300 Hz when pilot air 214 is supplied only through apertures 216. Accordingly, aspects of the present subject matter are directed to features of arrestor assembly 200 designed to carefully regulate the flow of pilot air 202 and the pressure drop across arrestor assembly 200, thereby providing improved flame stability and reduced operation noise.

[0044] Specifically, as best shown in FIG. 9, restrictor plate 212 may be formed such that a gap 230 is defined or formed between restrictor plate 212 and combustion chamber wall 160. In this manner, pilot air 202 may flow both through apertures 216 and through gap 230 into combustion chamber 132 to facilitate operation of pilot burner 170. According to example embodiments, a nominal length of gap 230 (e.g., an average about the circumference of restrictor plate 212) may be between about 0.01 and 0.2 inches, between about 0.02 and 0.1 inches, between about 0.03 and 0.07 inches, or about 0.05 inches. In addition, according to an example embodiment, the total cross-sectional area of the one or more apertures 216 and gap 230 may be between about 1 and 15 square inches, between about 2 and 10 square inches, between about 3 and 8 square inches, or about 5 square inches.

[0045] It should be appreciated that gap 230 may be formed in any suitable manner. For example, according to the illustrated embodiment as best shown in FIG. 10, restrictor plate 212 may define an arcuate profile within a vertical plane. In this regard, for example, restrictor plate 212 may be formed as a hyperbolic paraboloid that is not flat within a horizontal plane. Forming restrictor plate 212 in this manner may create gaps 230 between restrictor plate 212 and combustion chamber wall 160, as described above. Although a curved or bent restrictor plate 212 is illustrated, it should be appreciated that according to alternative embodiments, gap 230 may be formed by punching recesses around a perimeter of restrictor plate 212 or machining restrictor plate 212 in any other suitable manner to define the desirable size of gap 230.

[0046] Referring again to FIG. 9, arrestor assembly 200 may be secured within combustion chamber wall 160 by roll forming or any other suitable process. For example, combustion chamber wall 160 may be roll formed around flame arrestor 210 secure flame arrestor 210 to combustion chamber wall 160. Restrictor plate 212 may be supported on top of flame arrestor 210. In addition, according to the illustrated embodiment, a burner support bracket 232 may be mounted on top of restrictor plate 212 for supporting gas burner 134. For example, burner support bracket 234 may define a plurality of weld locations 234 where burner support bracket 232 may be welded or joined (e.g., by tack welding) to both restrictor plate 212 and flame arrestor 210. Gas burner 134 may then be seated on top of burner support bracket 232. Notably, this construction improves pilot flame stability and reduces combustion noise for improved consumer satisfaction and appliance performance.

[0047] As explained herein, aspects of the present subject matter are generally directed to an ultra-low nitrogen oxide (NOx) emission storage gas water heater including a combustion chamber that includes multiple air entrances for good combustion that reduces NOx emissions. One air inlet is defined through a bottom member with strategically placed perforations, through which air enters around the gas burner through a perforated, centrally located arrestor plate. The optimized air opening reduces NOx formation, and a total open area may include apertures in the punched section plus the area created by the gap around the perimeter. The arrestor plate may undergo a stamping procedure which transforms a flat metal plate into one with contours. These contours in the metal reduce the pressure drop across the perforated arrestor plate, which in turn enhances the stability of the pilot flame during the ignition phase of a gas burner. The small air gap around the perimeter of the combustion chamber skirt provides a stable supply of secondary combustion air that stabilizes combustion oscillations and eliminates combustion noise.

[0048] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. 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 include 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 languages of the claims.

Examples

Embodiment Construction

[0022]Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the invention. 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 invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

[0023]As used herein, the terms “first,”“second,” and “third” may be used interchangeably to distinguish one element or component from another and are not intended to signify location or importance of the individual elements or components. The terms “includes” and “i...

FIELD OF THE DISCLOSURE

[0001] The present subject matter relates generally to water heater appliances, and more particularly to combustion assemblies for gas water heaters.BACKGROUND OF THE DISCLOSURE

[0002] Water heater appliances utilize a variety of energy sources to create hot water in commercial and residential settings, the energy sources including electric, solar, and various fuels. For example, natural gas and propane are preferred by some customers due to, for example, the relatively quick heating rate. These fuels are supplied as a gas that is burned in a combustion chamber to provide heat energy to raise the water temperature.

[0003] A conventional unpowered gas water heater may include a standing pilot light that will ignite the main gas burner when a call for heat is required. This combustion system may be a partially pre-mixed gas system. In this regard, the primary combustion air comes directly from the outside environment through a venturi located at the combustion chamber door and the secondary air for the pilot comes through the wrapper.

[0004] Notably, gas water heater appliances are commonly subject to strict emissions standards or other government regulations. For example, nitrogen oxides (NOx) emissions are often regulated by governments and municipalities, e.g., such that they must be lower than 10 nanograms per joule. In order to meet these emissions standards, the flow of secondary air needs to be restricted to create a more fuel rich mixture which decreases flame temperature and reduces NOx emissions. However, introducing such a restriction may cause an audible sound (i.e., combustion noise) that osculates at 1300 Hertz or may result in pilot flame instability.

[0005] Accordingly, a gas water heater with features for reduced NOx emissions is desirable. More specifically, a gas water heater with improved pilot light stability, reduced noise, and improved operation would be particularly beneficial.BRIEF DESCRIPTION OF THE DISCLOSURE

[0006] Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

[0007] In one exemplary embodiment, a gas water heater appliance is provided including a tank for storage of water for heating, a combustion chamber wall positioned below the tank and defining a combustion chamber and a pilot air inlet, a gas burner positioned within the combustion chamber to heat the water in the tank, and an arrestor assembly mounted to the combustion chamber wall above the pilot air inlet and below the gas burner. The arrestor assembly includes a flame arrestor and a restrictor plate positioned adjacent the flame arrestor, the restrictor plate defining a bottom of the combustion chamber and comprising one or more apertures that provide fluid communication between the pilot air inlet and the combustion chamber.

[0008] In another exemplary embodiment, an arrestor assembly for a gas water heater is provided. The gas water heater includes a combustion chamber and the arrestor assembly includes a flame arrestor and a restrictor plate positioned adjacent the flame arrestor, the restrictor plate defining a bottom of the combustion chamber and comprising one or more apertures that provide fluid communication between a pilot air inlet and the combustion chamber.

[0009] These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures.

[0011] FIG. 1 provides a partially cut away, side view of a water heater according to an example embodiment of the present subject matter.

[0012] FIG. 2 provides a schematic of a gas flow control system as may be used with the example water heater of FIG. 1.

[0013] FIG. 3 provides a perspective view of a combustion assembly of the example water heater of FIG. 1 according to an example embodiment of the present subject matter.

[0014] FIG. 4 provides a cross-sectional view of the example combustion assembly of FIG. 3 according to an example embodiment of the present subject matter.

[0015] FIG. 5 provides a top, perspective view of an arrestor assembly of the example combustion assembly of FIG. 3 according to an example embodiment of the present subject matter.

[0016] FIG. 6 provides a bottom, perspective view of the example arrestor assembly of FIG. 5 according to an example embodiment of the present subject matter.

[0017] FIG. 7 provides an exploded view of the example arrestor assembly of FIG. 5 according to an example embodiment of the present subject matter.

[0018] FIG. 8 provides a close-up, perspective view of the example arrestor assembly of FIG. 5 according to an example embodiment of the present subject matter.

[0019] FIG. 9 provides a cross-sectional view of the example arrestor assembly of FIG. 5 according to an example embodiment of the present subject matter.

[0020] FIG. 10 provides a perspective view of a restrictor plate of the example arrestor assembly of FIG. 5 according to an example embodiment of the present subject matter.

[0021] Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention.DETAILED DESCRIPTION

[0022] Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the invention. 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 invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

[0023] As used herein, the terms “first,”“second,” and “third” may be used interchangeably to distinguish one element or component from another and are not intended to signify location or importance of the individual elements or components. The terms “includes” and “including” are intended to be inclusive in a manner similar to the term “comprising.” Similarly, the term “or” is generally intended to be inclusive (i.e., “A or B” is intended to mean “A or B or both”). In addition, here and throughout the specification and claims, range limitations may be combined or interchanged. Such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. The singular forms “a,”“an,” and “the” include plural references unless the context clearly dictates otherwise.

[0024] Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “generally,”“about,”“approximately,” and “substantially,” are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value, or the precision of the methods or machines for constructing or manufacturing the components or systems. For example, the approximating language may refer to being within a 10 percent margin (i.e., including values within ten percent greater or less than the stated value). In this regard, for example, when used in the context of an angle or direction, such terms include within ten degrees greater or less than the stated angle or direction (e.g., “generally vertical” includes forming an angle of up to ten degrees in any direction, such as, clockwise or counterclockwise, with the vertical direction V).

[0025] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” In addition, references to “an embodiment” or “one embodiment” does not necessarily refer to the same embodiment, although it may. Any implementation described herein as “exemplary” or “an embodiment” is not necessarily to be construed as preferred or advantageous over other implementations. Moreover, each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the invention.

[0026] Except as explicitly indicated otherwise, recitation of a singular processing element (e.g., “a controller,”“a processor,”“a microprocessor,” etc.) is understood to include more than one processing element. In other words, “a processing element” is generally understood as “one or more processing element.” Furthermore, barring a specific statement to the contrary, any steps or functions recited as being performed by “the processing element” or “said processing element” are generally understood to be capable of being performed by “any one of the one or more processing elements.” Thus, a first step or function performed by “the processing element” may be performed by “any one of the one or more processing elements,” and a second step or function performed by “the processing element” may be performed by “any one of the one or more processing elements and not necessarily by the same one of the one or more processing elements by which the first step or function is performed.” Moreover, it is understood that recitation of “the processing element” or “said processing element” performing a plurality of steps or functions does not require that at least one discrete processing element be capable of performing each one of the plurality of steps or functions.

[0027] Referring now to the figures, FIG. 1 illustrates a partial sectional, side view of an exemplary water heater 100 of the present invention. FIG. 2 provides a schematic of a gas flow control system as may be used with the example water heater of FIG. 1. According to the illustrated embodiment, water heater 100 includes a tank 102 that extends along a vertical direction V between a top wall 104 and a bottom wall 106. Tank 102 defines a generally cylindrical reservoir where water (e.g., identified generally by reference numeral 108) is supplied for heating and storage. Specifically, cool water 108 may be supplied into tank 102 by an inlet line 110 where it is heated before being discharged through an outlet line 112. According to an example embodiment, inlet line 110 and outlet line 112 are fluidly coupled to top wall 104 of tank 102 by one or more fluid connections, though other fluid supply / return configurations are possible and within the scope of the present subject matter.

[0028] Specifically, during operation of water heater 100, water 108 from an external water supply 114 travels through inlet line 110 and fills tank 102. Specifically, water heater 100 may include a cold water dip tube 116 that extends along vertical direction V towards bottom wall 106 of tank 102. As described in more detail below, water 108 within tank 102 may be heated by combusting a fuel (e.g., natural gas or propane), and the heated water 108 may be stored in tank 102 until demanded by a consumer, e.g., by opening a water consuming device such as an external fixture 118. In this regard, external fixtures 118 may include valves, faucets, appliances, or other water consuming devices fluidly coupled to water heater 100 through a water supply system of a residential or a commercial structure. Thus, when heated water 108 is requested by an external fixture 118, heated water travels upward through outlet line 112 where it is supplied to the external fixture 118 through one or more conduits or pipes of the water supply system.

[0029] To heat water 108 within tank 102, water heater 100 includes a combustion assembly 130 that burns a fuel or fuel mixture, e.g., including propane, natural gas, etc. Specifically, combustion assembly 130 includes a combustion chamber 132 positioned below bottom wall 106 of tank 102 in which a gas burner 134 is centrally located. Gas burner 134 is supplied with a gaseous fuel (e.g., propane or natural gas) from a gas supply line 136 including one or more flow regulating valves (e.g., such as a gas valve 138 as shown in FIG. 2). The gas is directed into a venturi 140, and in the process, ambient air is drawn in through a combustion air inlet 142 where it is entrained with the fuel to create a fuel / air mixture that is injected into gas burner 134 through the venturi 140. The resulting mixture of air and gas is ignited and burned by gas burner 134 to heat bottom wall 106 of tank 102 and the water 108 contained within tank 102.

[0030] Hot combustion gas may be exhausted from combustion chamber 132 through a vent or flue 144 centrally located within tank 102. Heat exchange with flue 144 also helps heat water 108 in tank 102. A baffle 146 may further promote this heat exchange between combustion gases and water 108. Gas exits water heater 100 though a vent hood 148, which may be connected with additional vent piping (not shown) to eject the combustion gases to an external environment.

[0031] According to example embodiments, water heater 100 may further include an anode rod 150 that provides protection against corrosion attacks on tank 102 and other metal components of water heater 100. In addition, a pressure relief valve 152 provides for a release of water from tank 102 in the event the pressure rises above a predetermined amount. Other safety features may be included while remaining within the scope of the present subject matter.

[0032] A thermostat 154 may be positioned within tank 102 to measure the temperature of water 108 in tank 102 and provide a signal to gas control valve module 156. As used herein, “a signal” is not limited to a single measurement of temperature and, instead, may include multiple measurements over time or continuous measurements over time. The signal may be provided through, for example, changes in current, voltage, resistance, or others. Depending upon whether the desired temperature has been reached as determined (e.g., from the signal from thermostat 154), gas control valve module 156 regulates the flow of gas to gas burner 134 through gas supply line 136.

[0033] Referring now to FIG. 2, combustion chamber 132 is formed by a chamber wall 160 that at least partially encloses combustion chamber 132 and may also provide support for tank 102 along a top edge 162. As shown, chamber wall 160 encircles combustion chamber 132 and is spaced apart from gas burner 134. In addition, water heater 100 may include an outer skirt or a cabinet 164 that surrounds both combustion chamber wall 160 and tank 102, though it should be appreciated that these features may alternatively be formed as part of cabinet 164. As illustrated for example in FIG. 1, cabinet 164 may define an air intake 166 for supplying ambient air that facilitates operation of water heater 100.

[0034] As shown, water heater 100 includes a pilot burner 170 that provides a pilot light 172 to ignite a mixture of air and fuel at gas burner 134 when a gas valve (e.g., as part of gas control valve module 156 or provided as a separate component) is open. An igniter 174 is positioned adjacent to pilot burner 170 and generates a spark used to ignite gaseous fuel and provide pilot light 172. Gaseous fuel for pilot burner 170 is supplied by a pilot burner fuel line 176. Gas valve control module 156 may control the flow of gaseous fuel through pilot burner fuel line 176 and the flow of gas to gas burner 134 through gas supply line 136. Alternatively, a dedicated pilot valve may be used to regulate the flow of gas to pilot burner 170.

[0035] In certain embodiments, gas valve control module 156 includes at least one controller 180. By way of example, controller 180 may include memory and one or more processing devices such as microprocessors, CPUs or the like, such as general or special purpose microprocessors operable to execute programming instructions or micro-control code associated with operation of water heater 100 as further described herein. The memory can represent random access memory such as DRAM, or read only memory such as ROM or FLASH. The processor executes programming instructions stored in the memory. The memory can be a separate component from the processor or can be included onboard within the processor. Alternatively, controller 180 may be constructed without using a microprocessor (e.g., using a combination of discrete analog or digital logic circuitry—such as switches, amplifiers, integrators, comparators, flip-flops, AND gates, and the like) to perform control functionality instead of relying upon software.

[0036] In some embodiments, a chamber sensor 182, which is generally configured to detect temperature, is positioned at, on, or adjacent to the combustion chamber 132. For instance, chamber sensor 182 may be attached to chamber wall 160 (e.g., supported thereon). As shown, chamber sensor 182 may be disposed, at least in part, within combustion chamber 132. Generally, chamber sensor 182 may be any suitable temperature sensor (e.g., thermocouple, thermistor, IR sensor, etc.) configured to detect a temperature within combustion chamber 132. For instance, an output voltage from chamber sensor 182 may be proportional to the temperature within the combustion chamber 132 or at chamber sensor 182. The voltage signal transmitted to controller 180 (e.g., and may be interpreted thereby) through conductors may thus represent representing the measured chamber temperature.

[0037] Further separate from or in addition to chamber sensor 182, water heater 100 may include an ambient sensor 184. Ambient sensor 184 may be spaced apart from chamber sensor 182. In some embodiments, ambient sensor 184 is attached to tank 102, such as indirectly or through the gas valve control module 156 (e.g., such that the ambient sensor 184 is generally fixed relative to the tank 102). For instance, ambient sensor 184 may be disposed within gas valve control module 156 on or in operable (e.g., electrical or wireless) communication with controller 180. Generally, ambient sensor 184 is configured to detect temperature outside of combustion chamber 132 (e.g., directly or indirectly). In some such embodiment, ambient sensor 184 includes or is provided as a suitable temperature sensor (e.g., thermocouple, thermistor, IR sensor, etc.) configured to detect temperate outside of combustion chamber 132. The voltage signal from ambient sensor 184 may be transmitted to controller 180 (e.g., and may be interpreted thereby). In additional or alternative embodiments, ambient sensor 184 communicates (e.g., wirelessly) with a separate probe or database (e.g., weather station) to receive an ambient temperature value detected apart from the tank 102 or water heater 100 generally.

[0038] In exemplary embodiments, water heater 100 includes gas valve 138 positioned along gas supply line 136. According to example embodiments, gas valve 138 may be incorporated as part of gas control valve module 156 or may be a separate component. Controller 180 is in communication with gas valve 138 to control the flow of gas therethrough by determining when gas valve 138 is energized. For this exemplary embodiment, gas valve 138 may operate so that when energized, gas valve 138 is fully open to allow a flow of gaseous fuel to gas burner 134. When not fully energized, gas valve 138 is fully closed (i.e. a “fail-closed” type valve) so as to prevent the flow of gaseous fuel to gas burner 134.

[0039] During use, opening or closing of gas valve 138 may generally be directed or controlled by controller 180. For instance, gas valve 138 may be directed to the open position to create a flame at gas burner 134. Controller 180 may receive one or more signals (e.g., from thermostat 154) to determine whether the temperature of water in tank 102 has reached a desired setpoint temperature. In response to the same, the controller 180 may direct the gas valve 138 to the closed position. In some embodiments, an open interval (i.e., time period in which gas valve 138 is continuously opened or a flame is generated) may be demarcated or observed as a single cycle.

[0040] Referring now also to FIGS. 3 through 10, aspects of combustion assembly 130 will be described in more detail according to example embodiments of the present subject matter. More specifically, aspects of the present subject matter are generally directed to an arrestor assembly 200 for use with combustion assembly 130 to address various problems described herein. Specifically, arrestor assembly 200 may be mounted to the combustion chamber wall 160 and generally defines a bottom boundary of combustion chamber 132. According to the illustrated embodiment, combustion chamber wall 160 may generally define a pilot air inlet 202, e.g., which may include a plurality of perforations or apertures defined around a circumference of a bottom of combustion chamber wall 160. In general, arrestor assembly 200 may be positioned above pilot air inlet 202 and below gas burner 134 within combustion assembly 130.

[0041] According to the illustrated embodiment, arrestor assembly 200 may generally include a flame arrestor 210 and a restrictor plate 212 positioned adjacent flame arrestor 212 and defining a bottom of combustion chamber 132. Specifically, according to the example embodiment, flame arrestor 210 is positioned below restrictor plate 212 and is generally configured to allow free passage of air and / or gases while preventing a flame from traveling therethrough. For example, flame arrestor 212 may be a mesh screen, a perforated plate, or any other structure that defines a plurality of small passages through which gases may flow while the passage of flames is prevented. For example, as shown schematically in FIGS. 8 and 9, a flow of pilot air 214 may pass through flame arrestor 210, as described in more detail below.

[0042] Specifically, restrictor plate 212 may define one or more apertures 216 that provide fluid communication between pilot air inlet 202 and combustion chamber 132. According to the illustrated embodiment, apertures 216 are defined on a raised embossment 218 of restrictor plate 212. In this regard, raised embossment 218 may be defined in the center of restrictor plate 212 for directing the flow of pilot air 214 toward pilot burner 170. In this regard, for example, raised embossment 218 may be positioned directly below pilot light 172 for supporting combustion of pilot burner 170.

[0043] Notably, as explained briefly above, supplying pilot air 214 only through apertures 216 may generate audible sounds and / or may generate pilot flame instability, resulting in the potential failure of water heater 100 and consumer dissatisfaction. Specifically, combustion noise may oscillate at approximately 1300 Hz when pilot air 214 is supplied only through apertures 216. Accordingly, aspects of the present subject matter are directed to features of arrestor assembly 200 designed to carefully regulate the flow of pilot air 202 and the pressure drop across arrestor assembly 200, thereby providing improved flame stability and reduced operation noise.

[0044] Specifically, as best shown in FIG. 9, restrictor plate 212 may be formed such that a gap 230 is defined or formed between restrictor plate 212 and combustion chamber wall 160. In this manner, pilot air 202 may flow both through apertures 216 and through gap 230 into combustion chamber 132 to facilitate operation of pilot burner 170. According to example embodiments, a nominal length of gap 230 (e.g., an average about the circumference of restrictor plate 212) may be between about 0.01 and 0.2 inches, between about 0.02 and 0.1 inches, between about 0.03 and 0.07 inches, or about 0.05 inches. In addition, according to an example embodiment, the total cross-sectional area of the one or more apertures 216 and gap 230 may be between about 1 and 15 square inches, between about 2 and 10 square inches, between about 3 and 8 square inches, or about 5 square inches.

[0045] It should be appreciated that gap 230 may be formed in any suitable manner. For example, according to the illustrated embodiment as best shown in FIG. 10, restrictor plate 212 may define an arcuate profile within a vertical plane. In this regard, for example, restrictor plate 212 may be formed as a hyperbolic paraboloid that is not flat within a horizontal plane. Forming restrictor plate 212 in this manner may create gaps 230 between restrictor plate 212 and combustion chamber wall 160, as described above. Although a curved or bent restrictor plate 212 is illustrated, it should be appreciated that according to alternative embodiments, gap 230 may be formed by punching recesses around a perimeter of restrictor plate 212 or machining restrictor plate 212 in any other suitable manner to define the desirable size of gap 230.

[0046] Referring again to FIG. 9, arrestor assembly 200 may be secured within combustion chamber wall 160 by roll forming or any other suitable process. For example, combustion chamber wall 160 may be roll formed around flame arrestor 210 secure flame arrestor 210 to combustion chamber wall 160. Restrictor plate 212 may be supported on top of flame arrestor 210. In addition, according to the illustrated embodiment, a burner support bracket 232 may be mounted on top of restrictor plate 212 for supporting gas burner 134. For example, burner support bracket 234 may define a plurality of weld locations 234 where burner support bracket 232 may be welded or joined (e.g., by tack welding) to both restrictor plate 212 and flame arrestor 210. Gas burner 134 may then be seated on top of burner support bracket 232. Notably, this construction improves pilot flame stability and reduces combustion noise for improved consumer satisfaction and appliance performance.

[0047] As explained herein, aspects of the present subject matter are generally directed to an ultra-low nitrogen oxide (NOx) emission storage gas water heater including a combustion chamber that includes multiple air entrances for good combustion that reduces NOx emissions. One air inlet is defined through a bottom member with strategically placed perforations, through which air enters around the gas burner through a perforated, centrally located arrestor plate. The optimized air opening reduces NOx formation, and a total open area may include apertures in the punched section plus the area created by the gap around the perimeter. The arrestor plate may undergo a stamping procedure which transforms a flat metal plate into one with contours. These contours in the metal reduce the pressure drop across the perforated arrestor plate, which in turn enhances the stability of the pilot flame during the ignition phase of a gas burner. The small air gap around the perimeter of the combustion chamber skirt provides a stable supply of secondary combustion air that stabilizes combustion oscillations and eliminates combustion noise.

[0048] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. 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 include 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 languages of the claims.

Examples

Embodiment Construction

[0022]Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the invention. 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 invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

[0023]As used herein, the terms “first,”“second,” and “third” may be used interchangeably to distinguish one element or component from another and are not intended to signify location or importance of the individual elements or components. The terms “includes” and “i...

Claims

1. A gas water heater appliance, comprising:a tank for storage of water for heating;a combustion chamber wall positioned below the tank and defining a combustion chamber and a pilot air inlet;a gas burner positioned within the combustion chamber to heat the water in the tank; andan arrestor assembly mounted to the combustion chamber wall above the pilot air inlet and below the gas burner, the arrestor assembly comprising:a flame arrestor; anda restrictor plate positioned adjacent the flame arrestor, the restrictor plate defining a bottom of the combustion chamber and comprising one or more apertures that provide fluid communication between the pilot air inlet and the combustion chamber.

2. The gas water heater appliance of claim 1, wherein the restrictor plate defines an arcuate profile within a vertical plane.

3. The gas water heater appliance of claim 1, wherein the restrictor plate is formed as a hyperbolic paraboloid.

4. The gas water heater appliance of claim 1, wherein the one or more apertures are defined proximate a center of the restrictor plate.

5. The gas water heater appliance of claim 1, wherein the one or more apertures are defined on a raised embossment of the restrictor plate.

6. The gas water heater appliance of claim 5, wherein the gas water heater appliance further comprises:a pilot light, wherein the raised embossment is defined directly below the pilot light.

7. The gas water heater appliance of claim 1, wherein a gap is formed between the restrictor plate and the combustion chamber wall.

8. The gas water heater appliance of claim 7, wherein a total cross-sectional area of the one or more apertures and the gap is between about 3 and 8 square inches.

9. The gas water heater appliance of claim 7, wherein a nominal gap length of the gap is between about 0.03 and 0.07 inches.

10. The gas water heater appliance of claim 1, further comprising:a burner support bracket mounted on a top of the restrictor plate for supporting the gas burner.

11. The gas water heater appliance of claim 10, wherein the burner support bracket is welded to the arrestor assembly.

12. The gas water heater appliance of claim 1, wherein the flame arrestor is rolled formed along with the combustion chamber wall to secure the arrestor assembly within the combustion chamber wall.

13. The gas water heater appliance of claim 1, wherein the flame arrestor is a mesh screen or a perforated plate.

14. An arrestor assembly for a gas water heater, the gas water heater comprising a combustion chamber, the arrestor assembly comprising:a flame arrestor; anda restrictor plate positioned adjacent the flame arrestor, the restrictor plate defining a bottom of the combustion chamber and comprising one or more apertures that provide fluid communication between a pilot air inlet and the combustion chamber.

15. The arrestor assembly of claim 14, wherein the restrictor plate defines an arcuate profile within a vertical plane.

16. The arrestor assembly of claim 14, wherein the restrictor plate is formed as a hyperbolic paraboloid.

17. The arrestor assembly of claim 14, wherein the one or more apertures are defined proximate a center of the restrictor plate.

18. The arrestor assembly of claim 14, wherein the one or more apertures are defined on a raised embossment of the restrictor plate.

19. The arrestor assembly of claim 14, wherein a gap is formed between the restrictor plate and a combustion chamber wall.

20. The arrestor assembly of claim 19, wherein a total cross-sectional area of the one or more apertures and the gap is between about 3 and 8 square inches.

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