Fully premixed under-burner and gas volume water heater

Abstract

The application provides a full premixed down-fired burner and a gas volumetric water heater, which comprises a stepless speed-regulating fan and an injection cavity; a gas servo proportional valve is arranged at the connection position of the stepless speed-regulating fan and the injection cavity; the outlet of the injection cavity is connected with a combustion cavity; a guide plate is arranged at the connection position of the injection cavity and the combustion cavity; a plurality of guide holes are arranged on the guide plate; a burner port is arranged on the side of the combustion cavity away from the injection cavity; a plurality of port holes are arranged on the burner port; and the diameter of the port holes is smaller than that of the guide holes. In the application, the stepless speed-regulating fan and the gas servo proportional valve are used to automatically control the technology, the corresponding air and gas are premixed at a certain ratio by the fan, and then are sent into the injection cavity for secondary mixing, and then are guided into the combustion cavity for tertiary mixing through the guide holes, so that the complete premixing of the gas is ensured, the premixed gas is fully and uniformly burned on the surface of the burner port, the combustion efficiency is high, the emission of NO X (nitrogen oxide) is reduced.

Description

Technical Field

[0001] This application relates to the field of water heater technology, specifically to a fully premixed downcombustion burner and a gas-fired storage water heater. Background Technology

[0002] A gas water heater is a device that uses gas as its energy source, heating water through the heat generated by gas combustion to achieve the required temperature for domestic use, heating, and industrial processes. A storage-type gas water heater refers to a water heater that has an internal container for hot water and is considered an integral part of the overall water heater system.

[0003] Gas-fired storage water heaters emit a certain amount of exhaust gas during operation. This includes NO. X Nitrogen oxides (NOx) have a certain impact on the air environment, and traditional gas-fired storage water heaters generally use atmospheric burners, which produce NOx in their flue gas. X The content of (nitrogen oxides) is relatively high.

[0004] Conventional reduction of NO X The method for reducing (nitrogen oxides) content is to mix fuel gases in various proportions before combustion, thereby adjusting the fuel gas mixing ratio to reduce NO after combustion. X (Nitrogen oxides) content, but due to insufficient fuel mixing, NO after combustion is often high. X The nitrogen oxide content still cannot be reduced to the desired level. Summary of the Invention

[0005] This application addresses the issue of insufficient fuel mixing, which often results in incomplete NO production after combustion. X To address the issue that the nitrogen oxide content still cannot be reduced to the desired level, a fully premixed downcombustion burner is provided, including: a stepless speed-regulating fan and an ejector chamber;

[0006] The air outlet of the continuously variable speed fan is connected to the inlet of the ejector cavity, and the air inlet of the continuously variable speed fan is connected to the atmosphere.

[0007] A gas servo proportional valve is provided at the connection between the continuously variable speed fan and the ejector cavity. The gas servo proportional valve is also connected to an external gas pipeline. The gas servo proportional valve is used to adjust the proportion of various types of gas input from the external gas pipeline.

[0008] The outlet of the ejector cavity is connected to the combustion chamber. A guide plate is provided at the connection between the ejector cavity and the combustion chamber. The guide plate is provided with a plurality of guide holes, which are evenly distributed on the guide plate. The ejector cavity communicates with the combustion chamber through the guide holes.

[0009] An igniter is provided inside the combustion chamber, and the igniter is used to ignite the gas.

[0010] The combustion chamber has a burner nozzle on the side away from the ejector chamber. The burner nozzle has a plurality of nozzle holes, which are evenly distributed on the burner nozzle. The diameter of the nozzle holes is smaller than that of the guide hole.

[0011] In one feasible implementation, the length of the ejector cavity is greater than or equal to 2-3 times the length of the combustion cavity, and the combustion cavity is located at the end of the ejector cavity.

[0012] In one feasible implementation, the area of ​​the guide hole is 200 mm². 2 -700mm 2 The area of ​​the vent hole is 3mm². 2 -10 mm 2 .

[0013] In one feasible implementation, a guide metal mesh is provided on the side of the guide plate facing the combustion chamber, and the guide plate is spot-welded to the guide metal mesh, wherein the mesh size is 20-40 mesh.

[0014] In one feasible implementation, a combustion metal mesh is provided on the side of the burner nozzle near the ejector cavity, and the burner nozzle is spot-welded to the combustion metal mesh, wherein the mesh size of the combustion metal mesh is 20-40 mesh.

[0015] In one feasible implementation, the cross-sectional shape of the burner nozzle is wavy, and the combustion metal mesh conforms to the shape of the burner nozzle.

[0016] In one feasible implementation, the reference for adjusting the gas ratio by the gas servo proportional valve is: the oxygen content in the flue gas after complete combustion of the gas is 5%-7%.

[0017] In one feasible implementation, the air inlet of the continuously variable speed fan is provided with an air filter.

[0018] Another aspect of this application provides a gas-fired storage water heater, including any of the above-described fully premixed downcombustion burners, and also includes a water tank;

[0019] The ejector cavity passes through the outer wall of the water tank, wherein the combustion chamber and the portion of the ejector cavity connected to the combustion chamber are located at the bottom of the inner cavity of the water tank;

[0020] The continuously variable speed fan, the gas servo proportional valve, and the portion of the ejector chamber connected to the gas servo proportional valve are located outside the water tank.

[0021] In one feasible implementation, an electronic controller is also included. The electronic controller is located outside the water tank and is communicatively connected to the continuously variable speed fan for controlling the start-up, shutdown, and wind speed of the continuously variable speed fan.

[0022] As can be seen from the above, this application provides a fully premixed downcombustion burner, comprising: a continuously variable speed fan and an ejector chamber; a gas servo proportional valve is provided at the connection between the continuously variable speed fan and the ejector chamber, the gas servo proportional valve is also connected to an external gas pipeline, a combustion chamber is connected to the outlet of the ejector chamber, a guide plate is provided at the connection between the ejector chamber and the combustion chamber, the guide plate is provided with a plurality of guide holes, an igniter is provided in the combustion chamber, the igniter is used to ignite the gas; a burner nozzle is provided on the side of the combustion chamber away from the ejector chamber, the burner nozzle is provided with a plurality of nozzle holes, the diameter of the nozzle holes being smaller than the diameter of the guide holes. This application employs a continuously variable speed fan and a gas servo proportional valve automatic control technology. First, the fan premixes the required air and gas in a specific ratio, then sends it into the ejector chamber for secondary mixing. Finally, it guides the mixture through the guide hole into the combustion chamber for tertiary mixing. This ensures complete premixing of the gas, allowing it to burn evenly and thoroughly on the burner nozzle surface, resulting in high combustion efficiency and reduced NO₂ levels. X (Nitrogen oxide) emissions have decreased. Attached Figure Description

[0023] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the implementation of the invention and, together with the description, serve to explain the principles of the embodiments of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0024] Figure 1 A schematic diagram of the structure of a fully premixed downcombustion burner shown in an exemplary embodiment of this application;

[0025] Figure 2 for Figure 1 Cross-sectional view;

[0026] Figure 3 for Figure 2 A magnified view of a portion of the image;

[0027] Figure 4 This is a schematic diagram of the structure of a gas-fired storage water heater, which is an exemplary embodiment of this application.

[0028] 100 - Infinitely variable speed fan; 200 - Gas servo proportional valve; 300 - Injector chamber; 400 - Combustion chamber; 500 - Water tank;

[0029] 310 - Guide plate; 320 - Guide hole; 330 - Guide metal mesh; 410 - Burner nozzle; 420 - Nozzle hole; 430 - Combustion metal mesh. Detailed Implementation

[0030] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the embodiments of the invention will be more comprehensive and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a full understanding of how embodiments of the invention are carried out.

[0031] Gas-fired storage water heaters emit a certain amount of exhaust gas during operation. This includes NO. X Nitrogen oxides (NOx) have a certain impact on the air environment, and traditional gas-fired storage water heaters generally use atmospheric burners, which produce NOx in their flue gas. X The content of nitrogen oxides (NOx) is high. Conventional methods to reduce NO... X The method for reducing (nitrogen oxides) content is to mix fuel gases in various proportions before combustion, thereby adjusting the fuel gas mixing ratio to reduce NO after combustion. X (Nitrogen oxides) content, but due to insufficient fuel mixing, NO after combustion is often high. X The nitrogen oxide content still cannot be reduced to the desired level.

[0032] This application addresses the issue of insufficient fuel mixing, which often results in incomplete NO production after combustion. X To address the issue that the nitrogen oxide (NOx) content cannot be reduced to the desired level, one approach is to provide a fully premixed downcombustion burner, referring to... Figure 1 As shown, Figure 1 This is a schematic diagram of the structure of a fully premixed downcombustion burner shown in an exemplary embodiment of this application; it includes a continuously variable speed fan 100 and an ejector cavity 300; the air outlet of the continuously variable speed fan 100 is connected to the inlet of the ejector cavity 300, and the air inlet of the continuously variable speed fan 100 is connected to the atmosphere.

[0033] After the stepless speed regulating fan 100 is connected to the atmosphere, it blows air into the burner, which can clean the burner after the previous combustion, ensuring that there are no impurities or soot in the burner, and preventing the combustion of gas after entering the burner from being affected by impurities, resulting in incomplete combustion.

[0034] A gas servo proportional valve 200 is provided at the connection between the stepless speed regulating fan 100 and the ejector cavity 300. The gas servo proportional valve 200 is also connected to an external gas pipeline. The gas servo proportional valve 200 is used to adjust the proportion of various types of gas input from the external gas pipeline.

[0035] For example, the gas servo proportional valve 200 can be equipped with multiple valve inlets, allowing connection to various types of gas. The flow rate of the incoming gas can be adjusted by controlling the degree of valve opening and closing, thereby controlling the proportion of different types of gas to ensure the mixed gas meets requirements. This constitutes the first mixing of the gas. After entering the gas servo proportional valve 200, the gas is propelled by the continuously variable speed fan 100 into the ejector chamber 300, where it flows and undergoes a second mixing.

[0036] The outlet of the ejector cavity 300 is connected to the combustion cavity 400. A guide plate 310 is provided at the connection between the ejector cavity 300 and the combustion cavity 400. The guide plate 310 is provided with a number of guide holes 320. The guide holes 320 are evenly distributed on the guide plate 310. The ejector cavity 300 is connected to the combustion cavity 400 through the guide holes 320.

[0037] The ejector chamber 300 and the combustion chamber 400 are connected by a guide hole 320, and the combustion gas also needs to enter the combustion chamber 400 through the guide hole 320. Therefore, the combustion gas undergoes a third mixing when it passes through the guide hole 320.

[0038] The combustion chamber 400 is equipped with a burner, and the igniter is used to ignite the gas. The side of the combustion chamber 400 away from the ejector chamber 300 is provided with a burner nozzle 410. The burner nozzle 410 is provided with a number of nozzle holes 420. The nozzle holes 420 are evenly distributed on the burner nozzle 410. The diameter of the nozzle holes 420 is smaller than the diameter of the guide hole 320.

[0039] The gas, after being mixed three times, burns at the burner orifice 420. Since the orifice diameter of 420 is smaller than that of the guide orifice 320, combustion is more complete and uniform. This application ensures complete premixing of the gas through three mixing stages and allows for thorough and uniform combustion on the burner orifice 410 surface, improving combustion efficiency while reducing NO₂ levels. X (Nitrogen oxides) emissions.

[0040] In some embodiments of this application, reference continues to be made to Figure 1 As shown, the length of the ejector cavity 300 is greater than or equal to twice the length of the combustion cavity 400, and the combustion cavity 400 is located at the end of the ejector cavity 300.

[0041] In this embodiment, to ensure uniform gas mixing, sufficient space and distance need to be reserved in the ejector cavity 300 to allow for thorough mixing as the gas passes through. Therefore, before the gas enters and fills the combustion chamber 400, it should travel at least the length of the combustion chamber 400, ensuring that all gas entering the combustion chamber 400 undergoes the same degree of mixing. Since the combustion chamber 400 is located at the end of the ejector cavity 300, and the combustion chamber 400 and the ejector cavity 300 overlap in length, the length of the ejector cavity 300 is at least twice the length of the combustion chamber 400. This distance constraint ensures that the gas has sufficient distance within the ejector cavity 300 for thorough mixing.

[0042] In some embodiments of this application, reference continues to be made to Figure 1 As shown, the area of ​​the guide hole 320 is 200 mm². 2 -700mm 2 The area of ​​the 420 vent hole is 3mm². 2 -10mm 2 .

[0043] Since the combustion gas needs to enter the combustion chamber 400 for combustion, if the area of ​​the guide hole 320 is too small, such as less than 200mm... 2 This will affect the rate at which the gas enters the combustion chamber 400, resulting in low combustion efficiency and failure to reach the rated power; if the area of ​​the guide hole 320 is too large, such as exceeding 700mm... 2 If the resistance encountered by the gas as it passes through the guide hole 320 is too small, the guide hole 320 cannot further mix the gas. When the area of ​​the guide hole 320 is 200 mm²... 2 -700mm 2 In the case of a guide hole 320, the hole area is 500 mm². 2 This allows for further mixing of the gas without affecting combustion efficiency, resulting in better combustion performance.

[0044] The burner orifice 420 has a relatively small area, allowing for close distribution on the burner nozzle 410. The flame will burn within the orifice 420, and the area and arrangement of the orifice 420 ensure uniform flame distribution. If the orifice 420 area is too small, such as less than 3mm... 2 This can easily lead to blockages, affecting gas combustion; if the area of ​​the burner hole 420 is too large, the gas release rate will be too high, resulting in incomplete combustion of gas. In this embodiment, the gas is released from a smaller hole, such as a burner hole 420 with an area of ​​7 mm². 2 This reduces the flow rate of the gas, resulting in more complete combustion.

[0045] In some embodiments of this application, reference is made to Figure 2 andFigure 3 As shown, Figure 2 for Figure 1 Cross-sectional view, Figure 3 for Figure 2 A partial enlarged view; wherein, a guide metal mesh 330 is provided on the side of the guide plate 310 facing the combustion chamber 400, and the mesh number of the metal mesh 330 is 20-40 mesh.

[0046] The guide plate 310 is equipped with a guide metal mesh 330, which is spot-welded to the guide plate 310 and the guide metal mesh 330. This allows for the adjustment of the gas passing through the guide hole 320 before the burner hole 420, ensuring uniform gas distribution. Simultaneously, when combustion impurities or soot are present, the guide metal mesh 330 prevents them from falling into the ejector cavity 300. Furthermore, the relatively large aperture of 20-40 mesh will not significantly affect the gas flow.

[0047] In some embodiments of this application, reference continues to be made to Figure 2 and Figure 3 As shown, a combustion metal mesh 430 is provided on the side of the burner nozzle 420 near the ejector chamber 300. The burner nozzle 420 and the combustion metal mesh 430 are spot-welded together. The mesh size of the combustion metal mesh 430 is 20-40 mesh. The combustion metal mesh 430 also has the effect of uniformly distributing the gas, ensuring that the flame of the burner nozzle 410 is uniformly distributed during gas combustion, achieving complete and sufficient combustion.

[0048] In some embodiments of this application, reference continues to be made to Figure 2 and Figure 3 As shown, the cross-sectional shape of the burner nozzle 410 is wavy, and the combustion metal mesh 430 fits the shape of the burner nozzle 410.

[0049] The cross-sectional shape of the burner nozzle 410 is wavy, which allows the slag generated and falling from the upper chamber after prolonged heating to accumulate in the groove without clogging the burner nozzle 410, and also facilitates the cleaning of the burner nozzle 410.

[0050] In some embodiments of this application, the gas servo proportional valve 200 adjusts the gas ratio based on the following criteria: the oxygen content in the flue gas after complete combustion of the gas is 5%-7%. This is to comply with NO... X The emission standards for nitrogen oxides (NOx) also require control of the fuel gas ratio, primarily focusing on controlling the oxygen content in the flue gas after combustion. In the case of complete combustion achieved by the burner described in this application, the oxygen content in the flue gas after combustion can be controlled between 5% and 7% via the fuel gas servo proportional valve 200, thus ensuring that NOx emissions are within acceptable limits. X The nitrogen oxide emissions are low and meet national standards.

[0051] In some embodiments of this application, the continuously variable speed fan 100 is provided with an air filter at its air inlet. The continuously variable speed fan 100 draws in air and provides power for the gas to enter the burner. Therefore, the air and gas will also mix together. The air filter can block impurities, dust and other foreign objects in the air, preventing foreign objects from mixing with the gas and affecting the combustion of the gas.

[0052] In this embodiment of the fully premixed downcombustion burner, during use, firstly, based on the rated power of the gas-fired water heater and the type of gas used, the speed of the continuously variable fan 100 and the gas servo proportional valve 200 are adjusted to set the air-gas mixing ratio, ensuring that the oxygen content in the exhaust gas produced after complete combustion of the gas is around 5-7%. At this time, the premixed gas with the set mixing ratio is then forcibly sent into the ejector chamber 300 of a certain length by the continuously variable fan 100 for secondary mixing. When the premixed gas enters the combustion chamber 400 through the guide hole, a unique metal mesh flow-blocking and pressure-equalizing structure is adopted at the guide plate 310 to ensure that the premixed gas airflow introduced into the combustion chamber through each guide hole is equal. After the premixed gas enters the combustion chamber 400 and undergoes a final mixing, it is sent to the burner nozzle 410 on the combustion chamber wall for ignition and combustion. At the burner nozzle 410, a unique metal mesh flow-blocking and pressure-equalizing structure is also employed to ensure uniform flame distribution during gas combustion, achieving complete and efficient combustion. The burner nozzle 410 has a wavy shape, which allows slag generated and falling from the upper chamber due to prolonged heating to accumulate in the grooves, preventing blockage of the burner nozzle 410.

[0053] As can be seen from the above embodiments, this application provides a fully premixed downcombustion burner, including: a continuously variable speed fan and an ejector chamber; a gas servo proportional valve is provided at the connection between the continuously variable speed fan and the ejector chamber, and the gas servo proportional valve is also connected to an external gas pipeline; a combustion chamber is connected to the outlet of the ejector chamber; a guide plate is provided at the connection between the ejector chamber and the combustion chamber; the guide plate has several guide holes; an igniter is provided in the combustion chamber for igniting the gas; a burner nozzle is provided on the side of the combustion chamber away from the ejector chamber, and several nozzle holes are provided on the burner nozzle, the diameter of which is smaller than the diameter of the guide holes. This application employs a continuously variable speed fan and a gas servo proportional valve automatic control technology. First, the required air and gas are premixed in a certain proportion by the fan and then sent to the ejector chamber for secondary mixing. Then, the mixture is introduced into the combustion chamber through the guide holes for tertiary mixing. The unique metal mesh flow-blocking and pressure-equalizing structure effectively ensures complete premixing of the gas, allowing the premixed gas to burn fully and evenly on the burner nozzle surface, resulting in high combustion efficiency and reduced NO₂. X (Nitrogen oxide) emissions have decreased.

[0054] Another aspect of this application provides a gas-fired storage water heater, see reference 1. Figure 4As shown, Figure 4 This is a schematic diagram of the structure of a gas-fired storage water heater according to an exemplary embodiment of this application. The gas-fired storage water heater includes a fully premixed downcombustion burner of any of the above embodiments, and also includes a water tank 500; an ejector cavity 300 passes through the outer wall of the water tank 500, wherein the combustion chamber 400 and the portion of the ejector cavity 300 connected to the combustion chamber 400 are disposed at the bottom of the inner cavity of the water tank 500; a continuously variable speed fan 100, a gas servo proportional valve 200, and the portion of the ejector cavity 300 connected to the gas servo proportional valve 200 are disposed outside the water tank 500.

[0055] The combustion chamber 400, located at the bottom of the water tank 500, heats the entire tank. To prevent condensate from affecting the premixed tubular metal fiber burner during heating in gas-fired storage water heaters, the combustion chamber 400 is typically installed at the top of the inner tank. This inevitably results in the main combustion chamber area being located in the upper part of the inner tank, leading to insufficient heating of the lower water level to the required temperature. In this application, the fully premixed bottom-burning burner is placed at the bottom of the tank, ensuring complete heating of the water without energy waste.

[0056] In some embodiments of this application, an electronic controller is also included. The electronic controller is located outside the water tank 500 and is communicatively connected to the continuously variable speed fan 100 for controlling the start / stop and wind speed of the continuously variable speed fan. Installing the electronic controller outside the water tank facilitates manual operation and use of the continuously variable speed fan by the user.

[0057] As can be seen from the above embodiments, this application also provides a gas-fired storage water heater, including a fully premixed downcombustion burner and a water tank; an ejector chamber passes through the outer wall of the water tank, wherein the combustion chamber and the portion connecting the ejector chamber to the combustion chamber are located at the bottom of the inner cavity of the water tank; a continuously variable speed fan, a gas servo proportional valve, and the portion connecting the ejector chamber to the gas servo proportional valve are located outside the water tank. The combustion chamber being located at the bottom of the water tank allows for heating of the entire water tank without wasting energy. It also includes an electronic controller for controlling the start / stop and fan speed of the continuously variable speed fan. The electronic controller is located outside the water tank for easy manual operation and use of the continuously variable speed fan by the user.

[0058] It should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a structure, article, or apparatus that includes a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a structure, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the structure, article, or apparatus that includes the element.

[0059] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the following claims.

Claims

1. A fully premixed downcombustion burner, characterized in that, include: A continuously variable speed fan (100) and an ejector cavity (300); The air outlet of the continuously variable speed fan (100) is connected to the inlet of the ejector cavity (300), and the air inlet of the continuously variable speed fan (100) is connected to the atmosphere. A gas servo proportional valve (200) is provided at the connection between the continuously variable speed fan (100) and the ejector cavity (300). The gas servo proportional valve (200) is also connected to an external gas pipeline. The gas servo proportional valve (200) is used to adjust the proportion of various types of gas input from the external gas pipeline. The reference for the gas servo proportional valve (200) to adjust the gas proportion is: the oxygen content in the flue gas after complete combustion of the gas is 5%-7%. The outlet of the ejector cavity (300) is connected to a combustion cavity (400). The length of the ejector cavity (300) is greater than or equal to 2-3 times the length of the combustion cavity (400), and the combustion cavity (400) is located at the end of the ejector cavity (300). A guide plate (310) is provided at the connection between the ejector cavity (300) and the combustion cavity (400). The guide plate (310) is provided with a plurality of guide holes (320), which are evenly distributed on the guide plate (310). The ejector cavity (300) communicates with the combustion cavity (400) through the guide holes (320). The guide plate (310) is provided with a guide metal mesh (330) on the side facing the combustion chamber (400). The guide plate (310) and the guide metal mesh (330) are spot welded together. The mesh number of the guide metal mesh (330) is 20-40 mesh. An igniter is provided inside the combustion chamber (400), which is used to ignite the gas; The combustion chamber (400) is provided with a burner nozzle (410) on the side away from the ejector chamber (300). The burner nozzle (410) is provided with a plurality of nozzle holes (420). The nozzle holes (420) are evenly distributed on the burner nozzle (410). The diameter of the nozzle holes (420) is smaller than the diameter of the guide hole (320). The burner nozzle (410) is provided with a combustion metal mesh (430) on the side near the ejector cavity (300). The burner nozzle (410) and the combustion metal mesh (430) are spot welded together. The mesh number of the combustion metal mesh (430) is 20-40 mesh. The cross-sectional shape of the burner nozzle (410) is wavy, and the combustion metal mesh (430) fits the shape of the burner nozzle (410).

2. The fully premixed underburner according to claim 1, characterized in that, The area of ​​the guide hole (320) is 200mm²-700mm², and the area of ​​the vent hole (420) is 3mm²-10mm².

3. The fully premixed underburner according to claim 1, characterized in that, The continuously variable speed fan (100) is equipped with an air filter at its air inlet.

4. A gas-fired storage water heater, characterized in that, The fully premixed downcombustion burner according to any one of claims 1-3 further includes a water tank (500). The ejector cavity (300) passes through the outer wall of the water tank (500), wherein the combustion cavity (400) and the portion of the ejector cavity (300) connected to the combustion cavity (400) are located at the bottom of the inner cavity of the water tank (500); The continuously variable speed fan (100), the gas servo proportional valve (200), and the ejector chamber (300) connected to the gas servo proportional valve (200) are located outside the water tank (500).

5. The gas-fired storage water heater according to claim 4, characterized in that, It also includes an electronic controller, which is located outside the water tank (500) and is communicatively connected to the continuously variable speed fan (100) for controlling the start-up, shutdown and wind speed of the continuously variable speed fan (100).

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