Outer fire cover of combustor of high-efficiency gas stove

Abstract

The invention relates to a high-efficiency gas stove burner outer fire cover which comprises an outer fire cover bottom plate and a plurality of bosses located on the outer fire cover bottom plate, the bosses are higher than the outer fire cover bottom plate, fire holes are machined in the bosses, and the fire holes incline inwards. Preferably, the boss is higher than the bottom plate of the outer fire cover by more than 3mm, the inward inclined angle of the fire hole is 0-20 degrees, the fire hole is in a cone shape with a small upper part and a large lower part, and the outer fire cover is made of an aluminum alloy material and can be polished to be in the natural color of metal aluminum. According to the high-efficiency gas stove burner fire cover, the thermal inertia of a burner can be reduced, the thermal efficiency, particularly the practical thermal efficiency, of a gas stove can be improved, the manufacturing cost is greatly reduced, and the high-efficiency gas stove burner fire cover can be conveniently detached and cleaned.

Description

Technical Field

[0001] The invention relates to a high-efficiency gas stove burner fire cover, which is suitable for household gas stoves. Background Art

[0002] Gas stoves have been around for over 200 years, but their basic structure has remained largely unchanged. They all use atmospheric burners. Gas is injected into the burner through a guide tube, mixed with primary air, and then passed to the ignition distributor on the burner. It is then ejected from the flame hole in the ignition distributor's fire cap, where it mixes with secondary air before burning. Cooking is done with the flame fully exposed to the air. Modern gas stoves have only seen minor improvements in appearance, materials, ignition, and safety, but the basic structure remains unchanged, resulting in lower thermal efficiency.

[0003] The inventors have found through long-term research and development that the main reasons for low thermal efficiency are four aspects:

[0004] 1. Most existing gas stove burners feature two flame rings: an inner and outer ring. These are known as two-ring burners. The outer ring's flame holes project flames diagonally upward, with a diameter of approximately 110-120 mm. This design wastes the heated area of the pot bottom between the inner and outer flames, concentrating the outer flames in a narrow circle. While this burner exhibits high thermal efficiency during flame detection, it exhibits extremely low thermal efficiency when used in a Chinese round-bottomed wok, resulting in poor cooking results.

[0005] The root cause of this phenomenon lies in thermal efficiency testing standards that are out of touch with China's realities. Current national testing standards, based on international standards, use large frying pans with a diameter of over 30 centimeters for testing. Because the flame is ejected close to the pan's bottom, the flame velocity is high, resulting in a higher heat transfer coefficient. Even if some heated area is wasted in the center, it represents a relatively small percentage of the pan's base. Furthermore, while this wasted area is in the center, it effectively reduces the heat intensity to the lowest area of the pan's base. Therefore, it has little impact on overall thermal efficiency, resulting in a higher measured thermal efficiency value.

[0006] Most household pots are small, around 20 centimeters in diameter. This is especially true in China, where electrical appliances are often used for boiling water and cooking, while gas stoves are primarily used for stir-frying. Households typically cook smaller portions; a typical large bowl of food, about 500 grams, occupies only about 20 centimeters of the pot's diameter. The broth, even smaller, is concentrated in the center of the pot. In particular, the most widely used two-ring stoves, due to their upwardly curved base, allow the outer ring's upward-directed flame to reach a diameter of around 150 centimeters on the pot's bottom. This effectively only reaches the edges of the dish, igniting the broth entirely. This significantly reduces thermal efficiency. During cooking, the edges of the dish often burn while the broth in the center remains unboiled. This necessitates repeated opening and stirring, which not only leads to significant heat loss, but also prolongs cooking time, wastes gas, and is extremely difficult to cook.

[0007] There are also spiral stoves on the market, where the outer flame is ejected tangentially along the circumference. Increasing the tangential flame velocity is useless; only increasing the normal flame velocity and thinning the flame layer can improve the heat transfer coefficient and thus thermal efficiency. Therefore, while the heat is concentrated in the center, the flame is weak, the normal flame velocity is low, and the thermal efficiency is also low. Nine-burner stoves, which have been released in recent years, also have dispersed flames. While these two stoves are not very efficient in practical cooking, they offer more evenly distributed heat than two-ring stoves, making cooking easier.

[0008] There are also infrared stoves that are modified to mix the air only once to improve thermal efficiency, but in fact it is unreasonable. In addition, there are major defects such as fine fire holes, inability to clean after clogging, and short lifespan, so they have been basically eliminated.

[0009] 2. Every time a gas stove starts cooking, it wastes some heat to heat the burner, stovetop, and other components. This is called thermal inertia. The heavier the burner, the greater the thermal inertia, and the more heat is wasted. Current burners are made of brass (previously, they were cast iron, which is prone to rust). For example, a 300-gram burner, heated to a constant temperature of approximately 300°C, consumes roughly the same amount of heat as boiling 80 grams of water. For a household gas stove that only takes a few minutes to cook a single bowl of food, using about 500 grams of water, this represents a significant amount of waste. Therefore, the lower the thermal inertia, the better.

[0010] Current national standards don't measure thermal inertia or the thermal efficiency of round-bottomed woks. However, manufacturers should strive to produce gas stoves with low thermal inertia and high thermal efficiency using round-bottomed woks to truly contribute to energy conservation and emissions reduction. Our own rough test method uses the same round-bottomed iron pan, starting from cold, to boil 500g or 1000g of water at room temperature. We compare the time and gas consumption of each stove, providing a rough comparison of the actual thermal efficiency of various gas stoves.

[0011] 3. The flame burns when exposed to the air, and loses a lot of heat due to contact and mixing with too much air outside.

[0012] 4. About 30% of the heat in a flame is radiated by infrared rays, most of which is radiated downward and outward and is wasted.

[0013] In 1997, the inventors discovered the aforementioned flaws (1) and (2) while using a two-ring stove. Convinced that round-bottomed woks must utilize centrally concentrated straight burners, they developed a gas stove with a thin-walled stainless steel cover weighing only approximately 80 grams. Stainless steel has poor thermal conductivity, resulting in minimal heat loss to the burner, low thermal inertia, and upward-focused firepower. While the straight burners' distance from the pot bottom and their increased exposure to cold air resulted in slightly lower thermal efficiency than a two-ring stove, the stove's practical performance was significantly better than that of a conventional stove. At the time, a satisfactory thermal efficiency was sufficient, making it a popular choice among users.

[0014] Gas stove energy efficiency ratings began to be standardized in 2015, with the national standard for built-in Class 1 energy-efficiency stoves setting a thermal efficiency of 63%. This is because the 1996 edition of the national standard for household gas stoves included an unreasonable stipulation regarding thermal efficiency testing: "…the initial water temperature should be room temperature plus 5°C, and the final water temperature should be the initial water temperature plus 50°C..." This "room temperature plus 5°C" preheats the stove for several minutes, masking the shortcomings of the high thermal inertia stove cover. The 2007 edition added an even more unreasonable stipulation: "…when the temperature rises 30K above the initial temperature, turn off the gas and continue stirring. The highest temperature reached is the final temperature..." This practice allows the stove with high thermal inertia to continue transferring heat to the pot even after it is turned off, further inflating the measured thermal efficiency. The 2020 version restored the 1996 method, but added a 15-minute preheating step, making it virtually indistinguishable between cooktops with different thermal inertias. (Actually, it would have been more reasonable to use an additional electric heater or ice pack to bring the water to room temperature and then test immediately after ignition. However, because the water volume tested was so large, the difference in thermal inertia values was minimal.) Knowing that their product's energy efficiency rating was low and unable to compete, they proactively discontinued production of the product.

[0015] In 2021, the inventors further realized the third and fourth reasons for the low thermal efficiency of the above-mentioned gas stoves, and developed a "gas stove insulation furnace", with a patent application number of 2021 2 1082865.9. The flame is placed in the insulation furnace to burn, firstly, to control the secondary combustion air, prevent too much cold air from contacting the flame, and allow part of the hot exhaust gas attached to the periphery of the flame to circulate in the furnace. Secondly, infrared radiation is made on the inner wall of the furnace to increase the furnace temperature, thereby reducing heat loss, and improving the use of thin-walled stainless steel fire covers with low thermal inertia for both the inner and outer fire covers. Due to manufacturing difficulties, the official trial product was not launched until the end of 2023, and the detected thermal efficiency was increased to 74%. However, due to the installation of aluminum silicate insulation cotton in the insulation furnace, the large size and clumsy appearance, coupled with some other defects, the market recognition is not high.

[0016] Therefore, in May 2024, the inventor changed the design to a gas stove with gas control only and no heat preservation. The patent is named "Gas stove with gas control pot rack" and the patent application number is 202421212615.6. Although the thermal efficiency is reduced to 69%, it is still much higher than the original 63% first-level energy efficiency. It also has good practical performance and user-acceptable appearance. However, there are some drawbacks: the stainless steel burner is difficult to remove and clean, and the interior of the gas control pot rack is also difficult to clean, and it will yellow and discolor over time.

[0017] As a result, some existing household gas stoves have gradually adopted the gas control principle and improved their design to improve thermal efficiency. Some two-ring gas stoves feature a gas control disc on the pot foot, raising the nominal thermal efficiency to 68%. However, to achieve this, the diameter of the gas control disc is increased, leaving a large gap between the edge and the wok. This allows cold air to flow in, but has little effect when the wok is actually in use, resulting in very poor cooking performance.

[0018] The flames of spiral stoves and nine-burner stoves do not flow radially outward from the center, the flame airflow is turbulent, and the air control plate cannot be used to improve the detection thermal efficiency.

[0019] Until the beginning of 2025, two new types of stoves appeared on the market. They concentrated the firepower in the center, and the effect of using a frying pan was better than that of ordinary stoves. They were equipped with a gas control basin, and the thermal efficiency was tested to be over 70%. The effect of using a frying pan was also better than that of ordinary stoves. However, it was only because the flame was concentrated in the center rather than the effect of the gas control basin that it was still worse than the straight-flame stainless steel burner of the insulated furnace stove and the gas-controlled pot rack stove.

[0020] We believe the burners of these two stoves have two flaws: 1. To minimize height, the jet angles of the outer ring fire holes and the flow angle of the surrounding secondary air differ significantly from the flame flow angle, resulting in a low flame velocity at the bottom of the pot and reduced thermal efficiency. 2. The original stove's flame distributor was located at the burner outlet, resulting in a simple structure. Now, independent flame distributors are becoming popular, some even connected to the flame cover with screws and weighing up to 1,000 grams. This structure is detrimental, increasing thermal inertia, increasing the heat dissipation area, reducing thermal efficiency, and increasing manufacturing costs. Summary of the Invention

[0021] Based on the above background technology, it is believed that existing gas stoves can be further improved in many aspects. The purpose of the present invention is to further improve the gas stove burner, especially the outer flame cover. The gas stove burner using the improved outer flame cover has the advantages of small thermal inertia, high thermal efficiency when using a cooking pot, low manufacturing cost, and easy disassembly and cleaning.

[0022] According to the above purpose, the present invention provides a high-efficiency gas stove burner fire cover.

[0023] The utility model comprises: an outer fire cover bottom plate and a plurality of bosses located on the outer fire cover bottom plate, wherein the bosses are higher than the outer fire cover bottom plate, and fire holes are processed on the bosses, and the fire holes are inclined inwards.

[0024] In the outer fire cover as described above, the height of the boss above the bottom plate of the outer fire cover is greater than 3 mm.

[0025] In the outer fire cover as described above, the inwardly inclined angle of the fire hole is 0 to 20 degrees.

[0026] In the outer fire cover as described above, the fire hole is in a cone shape that is smaller at the top and larger at the bottom.

[0027] In the outer fire cover as described above, the outer fire cover is made of aluminum alloy material.

[0028] In the outer fire cover as described above, the outer fire cover is polished to the natural color of metallic aluminum.

[0029] As described above, the high-efficiency gas stove burner fire cover of the present invention can reduce the thermal inertia of the burner and improve the thermal efficiency of the gas stove, especially the practical thermal efficiency, while significantly reducing the manufacturing cost and can be easily disassembled and cleaned. See the principle explanation in the following embodiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0031] Figure 1 This is a side cross-sectional view of an embodiment of a high-efficiency gas stove burner outer fire cover of the present invention.

[0032] Figure 2 yes Figure 1 Top view of . DETAILED DESCRIPTION

[0033] See Figure 1 , Figure 1 The structural diagram (cross-sectional view) of the gas stove including the outer fire cover of the present invention is shown in FIG. Figure 1 In the above description, 1 is the gas stove part, 1-1 is the gas stove cooktop, 1-2 is the outer outlet of the gas stove burner's ignition distributor, 1-3 is the inner outlet of the gas stove burner's ignition distributor, 1-4 is the inner fire cover installed on the inner outlet 1-3, 1-5 is the inner secondary air inlet, and 2 is the outer fire cover installed on the outer outlet 1-2 of the ignition distributor.

[0034] The outer fire cover 2 includes an outer fire cover bottom plate 2-1 and bosses 2-2 located on the outer fire cover bottom plate 2-1. The number of bosses 2-2 can be set as needed. They are generally evenly arranged on the outer fire cover bottom plate 2-1 and higher than the outer fire cover bottom plate 2-1. The higher value should preferably be greater than 3mm.

[0035] Each boss is machined with flame holes 2-3 to ensure secondary air is drawn in from the side grooves of boss 2-2 on both sides. Preferably, each flame hole 2-3 is tilted inward at a slight angle a of 0-20 degrees to help concentrate the flame power at the center of the pot bottom. Alternatively, each flame hole can be tapered, with a smaller top and larger bottom, to reduce resistance and increase flame speed.

[0036] These improvements to the external flame cover contribute to improved thermal efficiency. As the flaws of the two-ring flames in the existing gas stoves mentioned in the first section of the background art indicate, the entire flame should be concentrated in the center of the round-bottomed wok, first boiling the broth at the bottom and generating a large amount of steam to quickly cook the entire dish. Furthermore, a higher radial flame velocity results in a thinner flame layer. This means that the flame spreads over a larger area at the bottom of the wok per unit heat, resulting in a greater heat transfer rate, a higher heat transfer coefficient, and a higher thermal efficiency.

[0037] 1. High boss is beneficial to increase flame speed and improve thermal efficiency:

[0038] If a nozzle is opened on a flat surface to eject a mixed gas for combustion, the viscosity of the flame gas will inevitably drive the surrounding air (including secondary air) upward. The air on the horizontal surface is drawn horizontally into the nozzle hole, then suddenly changes direction to follow the flame upward. This creates significant resistance and turbulence, making the flame feel as if it is being pulled upward, resulting in significant speed loss. However, if a high pipe is erected on a flat surface, the gas is ejected from the nozzle and combustion occurs. The force exerted by the flame on the air surrounding the pipe below is less, resulting in less speed loss. The effect of a high boss is similar: the secondary air is pulled upward from below by the flame, reducing resistance as it mixes, resulting in a high flame speed and high thermal efficiency.

[0039] 2. The fire hole should be tilted upward and slightly toward the center, which can concentrate all the firepower in the center of the round-bottomed frying pan, and the flame speed and thermal efficiency are high:

[0040] The flame speed of a gas stove is determined by two factors: the buoyancy generated by the high-temperature flame and the initial velocity of the gas after mixing with the primary air. People often overlook the latter, spraying the flame at a large angle to the vertical and then allowing it to float upwards and contact the bottom of the pot, resulting in low thermal efficiency, as is the case with spiral stoves. This flame cover tilts the flame holes slightly upward and inward to concentrate the flame, aligning it with the direction of the flame's buoyancy. The combination of these two factors results in a higher flame speed and improved thermal efficiency. This effectively leverages the kinetic energy of the high-pressure gas jet to increase flame speed and thermal efficiency.

[0041] 3. The tapered fire hole with a small top and a large bottom is also beneficial to increase the flame speed and improve thermal efficiency:

[0042] After adding the boss, the flame hole becomes longer and more resistant, which reduces the injection velocity of the mixed gas or reduces the amount of primary air it draws, both of which also reduce the flame speed. By making the flame hole tapered, with a smaller top and a larger bottom, the resistance of the mixed gas inlet is reduced, and the ejection velocity at the flame hole outlet is higher, thereby improving thermal efficiency.

[0043] The fire cover is preferably made of pure aluminum alloy die-casting, which can be polished to the original color of aluminum. Aluminum alloy fire cover has many advantages:

[0044] In the past, when artificial gas was used, the flame spread quickly, making it prone to backfire in the burner. Therefore, the burner had to be made of cast iron, and the flame cap had to be made of iron or brass. Now that artificial gas has been phased out, and natural gas and liquefied petroleum gas do not backfire, burners and flame distributors are now made of aluminum alloy, but the flame cap is still made of brass.

[0045] It's a common misconception that aluminum alloy, with a melting point of only 660°C, can't be used as a flame cover. In fact, the flame cover is located below the flame. Atmospheric burners only mix about 70% primary air in the burner head, resulting in a low combustion rate. After exiting the flame hole, the air is ejected at a higher rate, preventing combustion. Combustion occurs only after mixing with secondary air, which reduces the injection rate and increases the combustion rate. The flame is approximately 1-2 mm away from the burner hole, radiating upward rather than downward to the edge of the burner hole, preventing the flame cover from heating up. The flame cover's temperature rises because some infrared heat is directed downward by the flame. Infrared heat in a gas flame is inherently low, accounting for only about 30% of the total heat. Some of this heat is radiated upward to heat the pot bottom, some is wasted by radiating to the surrounding area, and only a small amount is transferred downward to the flame cover surface, heating the flame cover. As the flame cover heats up, it also begins to dissipate heat. Some of this heat is recovered by heating the secondary air and the gas in the burner holes, some is radiated upward by infrared radiation to heat the pot bottom, some is wasted by radiating downward to the surrounding area, and some is wasted by heat transfer to the burner head below. The higher the fire cover's temperature, the more heat it dissipates. When the amount of heat absorbed and dissipated equals, equilibrium is reached and the fire cover stabilizes at a fixed temperature, typically around 300°C, well below the 660°C melting point of aluminum alloy. It's generally accepted that the long-term operating temperature of aluminum alloy should be below 200°C, as this reduces its mechanical strength, softening it like annealing steel. However, the fire cover isn't a stress-bearing component, and long-term extreme testing has proven that aluminum alloys are perfectly suitable for fire covers.

[0046] Aluminum alloy burner caps offer five advantages: ① They are lightweight, weighing only one-third of brass, significantly reducing the thermal inertia of gas stoves. ② They are inexpensive, costing only half that of brass. Therefore, a burner cap of the same volume costs only one-sixth of a brass one. Furthermore, their low melting point and low die-casting costs significantly reduce production costs. ③ The high-purity aluminum alloy, after polishing, exhibits excellent optical properties across the entire spectrum, particularly in the infrared, with a reflectivity exceeding 85% and an emissivity below 15%. The polished top surface of the burner cap reflects infrared radiation, absorbing less heat and lowering the burner cap temperature. This also reduces the temperature of the burner's diffuser below, saving energy. The polished bottom surface of the burner cap reduces radiant heat transfer to the diffuser below, further reducing its temperature and saving energy (although the burner cap itself will slightly increase its temperature). ④ The aluminum alloy's surface is protected by a natural transparent oxide film. As long as the temperature remains below its melting point, its color and optical properties remain unchanged after cooling. ⑤. Infrared light has a long wavelength and requires a low level of surface roughness. The outer flame cover surface generally does not get dirty. Even if it does get dirty, users can simply use a used toothbrush with detergent or toothpaste to remove it, or sandpaper or file to polish it back to its original metallic color to restore its performance. Even if it gets dirty and the user doesn't clean it for a long time, it won't cause any damage. The only problem is that the thermal efficiency will be slightly lower and the flame cover temperature will be slightly higher.

[0047] However, it should be noted that the polished surface cannot be anodized. When the aluminum oxide film is thick, it is transparent to visible light but opaque to infrared rays, just like being painted with black paint.

Claims

1. A high-efficiency gas stove burner outer fire cover, characterized in that: include: An outer fire cover bottom plate and a plurality of bosses located on the outer fire cover bottom plate, wherein the bosses are higher than the outer fire cover bottom plate, and fire holes are processed on the bosses, and the fire holes are inclined inwards.

2. The outer fire cover according to claim 1, characterized in that: The height of the boss above the bottom plate of the outer fire cover is greater than 3 mm.

3. The outer fire cover according to claim 1, characterized in that: The inward inclination angle of the fire hole is 0 to 20 degrees.

4. The outer fire cover according to claim 1, characterized in that The fire hole is in a cone shape that is smaller at the top and larger at the bottom.

5. The outer fire cover according to any one of claims 1 to 4, characterized in that: The outer fire cover is made of aluminum alloy material.

6. The outer fire cover according to claim 5, characterized in that: The outer fire cover is polished to the natural color of metallic aluminum.

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