JPH0211803B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a combustion method for a liquid fuel vaporizing burner. The combustion of kerosene is broadly classified into blue flame and white flame, depending on its mode of combustion.A premixed flame containing sufficient oxygen produces a blue flame, while a diffusion flame produces a white flame (luminous flame). It is estimated that the combustion process is similar to the flowchart shown in FIG. As can be seen from the flowchart in Figure 4, the difference between the two combustions is caused by the way oxygen diffuses, and the following factors affect this oxygen diffusion. Amount of combustion air (i.e., amount of oxygen) Mass of fuel Flow turbulence In order to perform blue flame combustion, the amount of combustion air must be large enough or the mass of the fuel must be small (i.e., in the case of atomized fuel, atomization is good). (the size of the oil droplets is small) or
Alternatively, it is necessary that the flow is highly turbulent and the fuel and oxygen are sufficiently mixed. However, in the case of combustion using a gun-type burner that is often used for general kerosene combustion, it is difficult to achieve blue flame combustion even if the above conditions are met. This is because in general gun-type burners, a flame holder is installed immediately after the atomized fuel nozzle, and a stable flame is formed in this part, which becomes the ignition source for the subsequent fuel, as shown in Figure 4. Each stage of combustion proceeds simultaneously, and the sprayed oil droplets are ignited around the oil droplets before being thermally decomposed into a complete gas with a light mass, and are surrounded by a concentric diffusion flame sphere and burned. do. For this reason, oxygen diffusion is insufficient, resulting in white flame combustion instead of blue flame. In white flame combustion (diffusion combustion), the diffusion of oxygen is through the flame of the diffusion flame ball to the above layer on the surface of the internal oil droplets, and the mixing of fuel and air is due to the fact that the fuel is in the form of oil droplets. Due to its large mass, it must be promoted by large turbulence in the flow or by excessive air volume. For this reason, white flame combustion burners require measures to generate large turbulence in the flow (eg, generation of maximum impact flow), and also require the supply of an excessive amount of air. In white flame combustion, an oxidation reaction of colloidal carbon occurs, but if oxygen diffusion is insufficient at this time, this colloidal carbon is discharged as soot. Such insufficient diffusion of oxygen may occur due to poor local mixing even if the amount of oxygen is sufficient. Insufficient oxygen diffusion also results in the emission of oxidative intermediates (often carbon monoxide). The increase in the content of the above two combustion emissions becomes noticeable when the excess air ratio is lowered, and for this reason, it has been difficult to reduce the excess air ratio below a certain level in diffusion combustion. In white flame combustion, it is necessary to generate large turbulence in the flow in order to promote mixing, but since this is turbulence in the flow that includes the diffused flame ball during combustion, it is loud and causes problems during white flame combustion. was the main cause of combustion noise. Another disadvantage is that the more turbulent the flow is to achieve complete combustion, the louder the noise becomes. Additionally, to prevent such turbulence from occurring, it is common practice to narrow down the flow path at the rear of the flame holder, but in this case the flame is formed in a narrow space with some openings. So the sound gets louder. On the other hand, in blue flame combustion, oxygen diffuses easily because it diffuses with vaporized gaseous fuel.
There is less need for large flow turbulence or excessive air volume. Therefore, in blue flame combustion, it is possible to reduce the excess air ratio to almost the stoichiometric ratio. In blue flame, the proportion of colloidal carbon produced is small, and the diffusion and mixing of gaseous fuel and oxygen is good, so even if the excess air ratio is lowered, soot and carbon monoxide emissions are small, and combustion is close to complete. It is possible to carry out combustion. In this way, by lowering the excess air ratio, combustion is possible close to the theoretical combustion air amount, and because the mixing is good, the combustion area is narrowed, so the flame temperature becomes close to the adiabatic flame temperature, which increases the temperature. Become. In blue flame combustion, combustion occurs after mixing is completed, so
It is quiet and the flame formation at the open end makes it quiet. As described above, blue flame combustion is clearly superior to white flame combustion as a combustion method for liquid fuel vaporization burners. Therefore, the object of the present invention is how to achieve complete blue flame combustion in a liquid fuel vaporizing burner, particularly in a burner with an output range of 23,000 to 57,000 Kcal. In order to achieve complete blue flame combustion, in addition to oxygen diffusion (that is, mixing), it is necessary to separate the nozzle region, combustion air region, fuel vaporization region, mixing region, combustion region, and high-temperature combustion gas circulation region. The present invention completely separates the nozzle area a, the combustion air area b, the fuel vaporization area c, the mixing area d, the combustion area e, and the high-temperature combustion gas circulation area f as shown in FIG. The oil droplets sprayed from the nozzle are first vaporized into a gaseous state by the heat of the high-temperature combustion gas sucked through the circulation area without being ignited in the oil droplet state in the fuel vaporization area, and then transferred to the mixing area. The gaseous fuel is mixed with air and then stably ignited in the combustion zone. In order to separate the nozzle zone, the combustion air zone, the fuel vaporization zone, the mixing zone and the combustion zone, and the hot combustion gas circulation zone, there must be no mixing or flame formation in the fuel vaporization zone, and There should be no flame formation in the mixing zone. The technical means taken by the present invention to achieve this object is to surround a fuel spray nozzle that is held in a nozzle holder and facing into the combustion chamber, and to form an air outlet coaxially with the nozzle to form a nozzle area. A combustion gas suction port is provided in front of the air outlet and between the air outlet and the air outlet is formed into a cylindrical shape consisting of a straight cylindrical portion and an expanded portion that continues to the front end of the cylindrical portion and expands forward. A burner cone made of porous ceramic with a porosity of 20 to 50% is installed coaxially with the nozzle, surrounding the fuel spray area of the nozzle, and the outlet of this burner cone is made of the same porous ceramic as the burner cone and has an open bottom. A rectifier plate is formed into a hollow conical or hemispherical shape with small holes perforated on its circumferential surface, and is disposed coaxially with the convex surface facing inside the burner cone. Alternatively, a flame stabilizing ring formed in an annular shape with a U-shaped cross section is provided coaxially with the current plate, and the dimensional relationship of these parts is such that the nozzle has a pattern with a spray angle of 60 degrees in a burner of 23,000 to 57,000 Kcal/H. Hollow
Cone, nozzle holder outer diameter is φ21 Air blowing speed from air outlet is 19 m/s to 1 m/s Air outlet cross-sectional area is 0.00077 m ² to 0.00146 m ² Air outlet inner diameter is φ37 to φ48 Burner cone cylindrical part inner diameter The ratio of the inner diameter of the air outlet is 1.3 or more. The ratio of the inner diameter of the air outlet to the length is 1/2 or more. The length of the air outlet is 20 mm or more. ) < 1 The difference between the cross-sectional area of the burner cone cylindrical part and the air outlet cross-sectional area is 0.00077m2 or ^more The inner diameter of the burner cone cylindrical part is φ48 or more Gap area / {air outlet + (burner cone cylindrical cross-sectional area - air outlet cross-section Figure)>1 Gap area is 0.00154m ² to 0.00667m ² The expansion angle of the burner cone expansion part is 30°,
The amount of oil injected from the nozzle is 2.5 to 7.0/H, the amount of air blown out from the air outlet is 0.5 to ^{1.3 Nm2} /m, and the amount of sprayed oil that hits the burner cone and current plate is 40% by weight or more. Air flows in the combustion air region in the center, and in the fuel vaporization region near the cone wall, oxygen-deficient combustion gas sucked in by the high-speed air flow and combustion gas gasified by the heat of the cone flow. This prevents two flows that do not fall within the flammability limits from mixing. According to the present invention, this phenomenon depends on the suction of oxygen-deficient combustion gas, and structurally, it depends on the relationship between the air outlet and the diameter of the cone cylindrical part, and the cone shape, and in the mixing zone, By setting the baffle plate and the aperture area of the cone outlet, the flame propagation speed and the air-fuel mixture flow speed in the mixing region are balanced to prevent the flame from flowing backward into the mixing region, that is, from backfiring. Furthermore, as mentioned above, in order to achieve blue flame combustion in the combustion method of the present invention, suction of combustion gas into the burner cone is essential, and the shape and dimensions of each part are determined to optimize the suction amount. has been done. In other words, if the diameter of the air outlet is too small, the air blowing speed will be too high, colliding with the baffle plate and applying back pressure, making it difficult to suck in the circulating gas and making combustion noise louder. On the other hand, if it is too large, the air flow rate will slow down and the suction of circulating gas will become worse. Therefore, the diameter is φ37 to φ48,
The air blowing speed is preferably 19 m/s to 10 m/s. Also, if the length of the outlet is too short, the air that blows out will not flow in the axial direction, making it impossible for the igniter's spark to flow into the fuel spray area, resulting in ignition failure, or combustion gas and air inside the burner cone. When mixed, a yellow flame appears inside the burner cone and the combustion sound becomes louder. Therefore, the relationship between the diameter and length of the air outlet is preferably such that the length is about 1/2 or more of the diameter, and the length is preferably 20 mm or more. In addition, the diameter of the outlet and the diameter of the cylindrical part of the burner cone are closely related, and if the diameters of the two become close, for example, the diameter of the cylindrical part of the cone becomes smaller, the combustion gasified by the sucked combustion gas will be reduced. Gas and air mix in the front half of the cone, creating a flame inside the cone. Therefore, the diameter of the cylindrical portion of the burner cone needs to be at least 1.3 times the diameter of the air outlet.
Also, from the suction relationship, air outlet cross-sectional area / (burner cone cylindrical section cross-sectional area - air outlet cross-sectional area) <1
It is desirable that the difference between the cross-sectional area of the burner cone cylindrical portion and the air outlet cross-sectional area be 0.00077 m ² or more, and the inner diameter of the burner cone cylindrical portion is preferably φ48 or more. That is, as a result, air flows in the center and vaporized fuel flows on the outside, and the two mix for the first time at the baffle plate and cone outlet constriction, and then a stable flame is formed in the combustion zone consisting of the baffle plate and the flame-holding ring. be done. Determination of the shapes and dimensions of each of the above parts will be further explained. The presence or absence of suction of combustion gas can be confirmed by measuring the gas temperature at the suction port position when the combustion gas is combusted in the combustion chamber, with the suction port closed and when the suction port is opened. As a result of measuring the temperature of an actual burner in which the method of the present invention was carried out, it was approximately 800°C when there was a suction port, while it was approximately 400°C when the suction port was closed. From this, it can be assumed, albeit indirectly, that in the present invention, there is actually a circulating flow due to the provision of the suction port between the burner cone and the air outlet. If the amount of combustion gas to be sucked is estimated based on Von Karman's theory of thrust increase, the temperature of the circulating gas to be sucked in at the suction port position is approximately 800℃.
℃, and when the suction port is closed, the above temperature is approximately 400℃
Therefore, calculations are made assuming that the composition of the circulated gas to be sucked is the same as the composition of the combustion gas and the temperature is 800°C. When the drag term is ignored According to Von Karman's thrust increase theory, the equation includes a drag term: Ff, but calculations are performed assuming that this can be ignored. As a result, the flow rate ratio n between the amount of circulating gas sucked and the combustion air is n≈1, that is, almost the same amount of combustion gas as the amount of combustion air is suctioned and circulated. The amount of heat held by this circulating gas is as shown below. Approximately 15000Kcal/H (MAX value) When taking into account the resistance term In the actual machine (fluid resistance due to ceramic surface roughness, fluid resistance due to the shape of the rectifier plate and burner cone) (i.e. fluid resistance due to flow path changes), etc. Therefore, the resistance term: Ff can no longer be ignored. When this term becomes large, suction disappears and blue flame combustion becomes impossible. Therefore, in the present invention, the shape of the burner cone and the shape of the current plate are made as described above so as to minimize this resistance term. The suction amount has an optimum value based on the amount of heat required to vaporize the sprayed fuel and the amount of gas to prevent flame holding in the cone, and the present invention maintains this optimum value.
The shapes and dimensions of each part, including the resistance term, are determined to be the above shapes and dimensions. On the other hand, according to the present invention, the amount of oil sprayed onto the burner cone and the current plate is set at the normal position.
When sprayed from the nozzle, the amount that does not hit the ceramic surface and flows out of the cone is from the annular portion between the cone outlet and the current plate. The amount of oil sprayed onto the burner cone and baffle plate is calculated to be 81% by weight for a nozzle spray angle of 60°. However, in reality, due to air flow around the nozzle and air resistance, the spray angle may not be the prescribed spray angle, and may differ from the calculated value depending on the spray pattern of the nozzle. For this reason, the oil that hits the ceramic surface is caught in a container,
Determine this amount by weighing: 60% by weight
becomes. In the case of the present invention, during combustion, there are no oil droplets inside the cone that burn and disappear in the flame, and almost all of the oil droplets in the above-mentioned proportion reach the ceramic surface. According to the present invention, approximately 60% by weight of the liquid fuel sprayed from the nozzle reaches the burner cone and the inner surface of the baffle plate, which are heated by the high-temperature combustion gas sucked from the suction port. After being sucked into and held by the ceramic support surface, the fuel is instantaneously vaporized by the heat of the burner cone and rectifying plate to become a primary vaporized fuel body. Also, among the fine oil droplets that do not reach the burner cone and the inner surface of the baffle plate, those that reach the fuel vaporization region are vaporized by the heat of the high-temperature circulating gas and become secondary vaporized fuel bodies. The high-temperature circulating gas sucked through the vaporized fuel body and the high-temperature combustion gas circulation region flows along the inner surface of the burner cone, and the oxygen concentration near the surface becomes below the lower combustion limit. That is, an oxygen-deficient layer is formed near the inner surface of the burner cone, thereby preventing the formation of flame in the fuel vaporization region. On the other hand, the central part of the burner cone is the combustion air region where the air blown out from the air outlet flows, and here there is a primary vaporized fuel body that has vaporized when it hits the baffle plate and some oil droplets that have been caught up in the air flow. However, the amount of these fuels is extremely small and the concentration is above the lower flammability limit. That is, an oxygen-rich zone is formed in the combustion air region to prevent flame formation. This combustion air and the oxygen-deficient vaporized fuel are mixed at the burner cone outlet by promotion of flow turbulence by the restriction formed by the baffle plate and the burner cone outlet, and oxygen is sufficiently diffused. At this time, due to the balance between the flame propagation speed and the air-fuel mixture based on the shapes and dimensions of each part described above, flame formation in the mixing part is prevented, and the flame is ignited at the end of the baffle plate and the small hole part of the baffle plate. That is, the annular gap 1 formed between the current plate 8 and the outlet of the burner cone 6
8, from the viewpoint of balance, it is desirable that the gap area/{passage area of the air outlet + (cross-sectional area of the burner cone cylindrical part - cross-sectional area of the air outlet)}>1, which means that the gap area should be >0.00154 ^m2 . This means that it is desirable. Further, in order to prevent backfire, it is desirable that the gap area be <0.00667 m ² , and as a result, the gap area including the area of the small holes in the rectifier plate is preferably 0.00154 m ² to 0.00667 m ² . The concave portion formed behind the baffle plate serves as a retention point for the airflow, and a portion of the high-temperature circulating gas is retained in this portion, which becomes a source of ignition for the air-fuel mixture discharged from the burner cone outlet. Therefore, a blue flame will come out from the end of the rectifier plate and the small holes. The concave portion of the baffle plate serves as an ignition source, and also has the role of completely separating each area of the burner space without disturbing the combustion air flow. Therefore, an appropriate number of small holes are drilled parallel to the axis of the current plate near the peripheral edge and in a portion surrounding the top near the top, leaving an appropriate width at the top and middle of the current plate. Further, the unburned gas that is not ignited at the end of the current plate flows along the inner and outer peripheral surfaces of the flame stabilizing ring and is ignited in the recessed portion behind the flame stabilizing ring. The concave movement behind the flame-holding ring, like the recess behind the baffle plate, becomes a stagnation point for the airflow, and high-temperature combustion gas stagnates in this area, which becomes a source of ignition for unignited gas that has not ignited at the edge of the baffle plate. Become. Therefore, a stable blue flame will also be formed at the end of the flame-holding ring. A portion of the high-temperature combustion gas is sucked into the burner cone from the suction port as a circulating gas to heat the burner cone and vaporize the oil mist as described above. As described above, the burner cone is heated by the circulating gas, in which the blue flame combustion gas formed on the current plate and flame holding ring passes through the high temperature combustion gas circulation area, is sucked from the suction port, and circulates within the cone. This transfers heat to the burner cone, but at this time, since the combustion gas flows near the cone wall, it is heated from both the inside and outside of the cone, which only shortens the rise time at initial ignition. However, it is possible to sufficiently supply the amount of heat necessary for vaporizing the liquid fuel. For example, under the maximum usage conditions of this burner,
The amount of heat required to vaporize liquid fuel is approximately
The amount of heat is 1000Kcal/H, but this amount of heat is replenished from the amount of heat held by this combustion gas by sucking in the amount of combustion gas that is approximately 1.0 times the amount of the combustion air jet. Only about 7%. Therefore, the efficiency of the present invention is greatly improved by employing the heating method by convective heat transfer to the burner cone. Therefore, the present invention can realize complete blue flame combustion,
Since the gasified fuel and combustion air are mixed, the mixture is good, and even if the excess air ratio is low, no soot or carbon monoxide is generated. FIG. 5 shows how soot and carbon monoxide are generated when a household water heater is equipped with a burner that implements the method of the present invention. The general CO emission standard is CO/CO ₂ ≦0.02, so the combustion range of this burner is O ₂ = 1 (vol%) or more, preferably O ₂ = 1.5 in terms of smoke degree. (vol%) That's all. In the method of the present invention, in order to prevent flame holding in the cone, the oxygen concentration near the wall is kept below the lower combustion limit. No soot or tar formation was observed. In addition, the present invention was based on the recognition that the noise caused by the maximum air shock flow in the plane of the flame holder is the main cause of combustion noise, and the structure of the flame holder was moved from immediately after the nozzle to the cone outlet, so that combustion is prevented. The flame is formed by the open end, and the operation is quiet. By the way, when we measured the noise of a water heater equipped with a burner that implemented the method of the present invention, it was 40 to 43 dB(A).
It was 65 to 70 dB(c). On the other hand, in the method of the present invention, the burner cone and the current plate are formed by casting a slurry made by mixing and stirring a powder containing 30 to 75% by weight of silicon and 10 to 50% by weight of clay, the balance being silicon nitride. The fact that it is made of porous ceramic with a porosity of 20 to 50% obtained by nitriding and firing at 1350 to 1650°C also greatly contributes to achieving a perfect blue flame and preventing the generation of soot. In blue flame combustion, as mentioned above, oxygen must diffuse with the vaporized gaseous fuel, but in the method of the present invention, approximately 60% by weight of the oil mist sprayed from the fuel spray nozzle is in the burner cone. The fuel collides with the inner circumferential surface of the expanded part and the current plate, but since these are made of water-absorbing porous ceramic with the above-mentioned structure, the fuel is once sucked into the ceramic and held, and then heated by the burner. It quickly evaporates into gas due to the heat of the cone. That is, the vaporization of fuel by the burner cone and baffle plate is largely dependent on the water absorbency of the ceramics that constitute them, and the water absorbency is influenced by the porosity of the ceramic. Incidentally, burner cones were prototyped using various ceramic materials and their properties during combustion were investigated, and the results are shown in the table below.

[Table] From the above table, it can be seen that a blue flame cannot be obtained with a substrate with a low porosity, and that silicon nitride substrate is the best material for burner cones and rectifier plates when thermal shock resistance is taken into account. Hereinafter, an example of implementation of the present invention will be described based on the drawings. FIG. 2 is a longitudinal cross-sectional view of a main part of a water heater equipped with a burner embodying the present invention. In this illustrated example, burner A installed in water heater B has an output of 35,000 Kcal/H and has a cylindrical combustion chamber 2.
The heat exchanger flange pipe 10 is provided on the peripheral wall of the heat exchanger and faces into the combustion chamber 2. The burner A includes a fuel spray nozzle 3, an air outlet 4 provided around the fuel spray nozzle 3 surrounding the nozzle 3, a burner cone 6 provided surrounding the combustion spray area of the fuel spray nozzle 3, and a burner cone 6. A current plate 8 is provided at the outlet of the flow regulating plate 8, and a flame stabilizing ring 9 is provided in front of the current plate 8. The air outlet 4 is formed in a straight cylindrical shape that opens from the heat exchanger flange pipe 10 in a direction perpendicular to the axial direction of the combustion chamber 2, and the rear part is connected to the combustion chamber 2.
It is connected to the air passage 12 of the blower 11 on the outside. Further, a nozzle holder 1 is provided coaxially within the air outlet 4, and the tip of the fuel spray nozzle 3 held by the nozzle holder 1 is directed from the front end opening of the air outlet 4 to the center of a burner cone 6, which will be described later. It's coming. The air outlet has an inner diameter of 40 mm and a total length of 55 m/m, and the burner cone has a cylindrical inner diameter of 63 mm and an outlet inner diameter of 63 mm.
104〓, the total length is 100m/m, the expansion angle of the expansion part is 30゜,
The distance from the air outlet to the rear end is 20m/m, the opening outer diameter of the baffle plate is 90〓, the total length is 45m/m, and the distance from the air outlet to the rear end is 82m/m from the front end of the burner cone to the front end. The distance from the front end of the burner cone is 7 m/m, the outer diameter of the 36 flame holding rings is 130 mm, the inner diameter is 104 mm, the total length is 15 m/m, and the distance from the front end of the burner cone is 12 m/m. It is formed. The diameter of the nozzle holder 1 is 21 mm. Regarding the air blown out from the air outlet 4 by the blower 11, the air volume is 0.5 to 1.3 Nm ³ /m,
It must be 19m/sec≧Blowing speed≧10m/sec, and in this example, the air volume is 0.8Nm ³ /m,
The blowing speed is set to 16 m/sec. The fuel spray nozzle 3 is a nozzle with a spray angle of 60° having a conventionally well-known structure, and its rear portion communicates with an oil supply source 14 via an oil feed pipe 13 that passes through the nozzle holder 1 in the axial direction. The oil pipe 13 is equipped with an electromagnetic pump 15 in the middle, and the amount of oil sprayed from the nozzle 3 by the operation of the electromagnetic pump 15 is set to 4.3/H. Incidentally, the above oil amount needs to be 2.6 to 7.0/H. The burner cone 6 has the shape shown in the figure, that is, a straight or slightly tapered cylindrical portion 6a is formed at the rear, and a conical expansion that continues from the front end of the cylindrical portion 6a and extends forward in a widening shape. A portion 6b is formed, which is held in front of the air outlet 4 by a suitable holding member 17, and provided coaxially with the fuel spray nozzle 3 with a gap 5 between the air outlet 4 and the air outlet 4. . The burner cone 6 has a cylindrical part inner diameter>48〓, cylindrical part inner diameter/air outlet inner diameter>1.3, air outlet passage area/(cylindrical part cross-sectional area - air outlet cross-sectional area)<1,
The cross-sectional area of the cylindrical part - the cross-sectional area of the air outlet must be > ^0.00077m2 , and in this example, the inner diameter of the cylindrical part is 63〓,
The cross-sectional area of the cylindrical portion - the cross-sectional area of the air outlet = 0.00173 ^m2 . The burner cone 6 has a total length of 100 m/m, an expanded portion 6b that expands forward at an expansion angle of 30 degrees, and its front end has an inner diameter of 104 mm, and its rear end and air outlet 4. The gap 5 with the front end has a width of 20 m/m. A gap 5 between the opening at the rear end of the burner cone 6 and the air outlet 4 is used to generate high-temperature combustion gas in the combustion chamber 2 by utilizing the negative pressure generated around the air outlet 4 at high speed. This constitutes a suction port 5 that sucks the gas into the burner cone 6. The current plate 8 is formed into a conical or hemispherical shape with an open bottom, and the convex surface faces the burner cone 6 side.
It is provided coaxially with the burner cone 6 with most of it inserted into the burner cone 6, and an annular gap 18 is formed between its outer periphery and the outlet of the burner cone 6. The current plate 8 has a total length of 45 m/m and an opening diameter of 90 mm, and its top is placed at the outlet of the burner cone 6 so that it is located 82 m/m from the front end of the air outlet 4. It is inserted and deployed, and its front end protrudes forward by 7 m/m from the front end of the burner cone 6. In addition, the rectifier plate 8 has a position other than its center.
36 small holes 7 of 6〓 are drilled. The annular gap 18 formed at the outlet of the burner cone 6 by the baffle plate 8 and the burner cone 6 is the actual outlet of the burner cone 6: gap area/{passage area of air outlet + (burner cone cylinder) Sectional cross-sectional area - Air outlet cross-sectional area)}>
1. Gap area > 0.00154 m ² and 0.00154 m ² < Gap area < 0.00667 m ² to prevent backfire at the outlet of burner cone 6. In this example, 36 small holes 7 were Including
It is formed at ^0.00410m2 . The number and diameter of the small holes 7 can be slightly increased or decreased as long as the annular gap 18, ie, the substantial exit of the burner cone 18, satisfies the above conditions. Above, the burner cone 6 and rectifying plate 8 are made of silicon 42
%, silicon nitride 18%, and clay 40% as raw materials, and is manufactured by the method described below. That is, ethanol is added to powder raw materials of silicon and silicon nitride, and the mixture is ground in a cylinder mill for 4 hours. At this time, using ethanol instead of water is
This is because silicon and silicon nitride react with water and generate gas during pulverization. After pulverization, the ethanol is removed by distillation, and the powder is heated to 175°C in air to make it stable against water, as it will react with water. Next, the above-mentioned crushed silicon and a flocculant (sodium polyacrylate) were added to the slurry of clay and water.
A casting slurry is prepared by mixing and stirring, and a burner cone 6 and a current plate 8 are cast and formed, respectively. Then, holes for the small holes 7 are formed in the rectifier plate 8, and after drying, the molded body is fired in nitrogen at 1450° C. for 15 hours to obtain a product. The physical properties of the burner cone 6 and current plate 8 according to the present invention manufactured by such a method are shown in the table below. Open pore porosity (%) 30 Bending strength (25℃) 13.0Kg/mm ² (700℃) 13.0 Composition (X-ray peak ratio) αSi ₃ N ₄ 1.0 βSi ₃ N ₄ 1.0 O′ phase 2.3 X phase 0.2 The above porosity can be changed by changing the amount of flocculant added to the casting slurry and the firing temperature, but the range that can be used for the burner cone 6 and the current plate 8 is a porosity of 50 to 20%. In this example, it is 30%. In addition, rubber press molding, injection molding, and casting molding are available as methods for molding the cone and current plate. Rubber press molding is advantageous in that it can speed up the molding process, but it requires cutting of the end surfaces of the molded product. The disadvantage is that the molding equipment required is expensive. Injection molding is similarly advantageous in that the molding speed can be fast, but since the base material contains 40 to 50% by volume of binder, the base material is expensive and it takes a long time to heat and remove the binder. However, there are disadvantages in that it requires equipment for environmental regulations such as exhaust gas purification, and that molding equipment is expensive. On the other hand, casting molding cannot achieve as high a molding speed as the first two methods, but it is advantageous in obtaining homogeneous and thin-walled molded products, and there is no need for cutting or debinding of molded products, making it possible to form This method has the advantages of simple subsequent steps and low equipment costs, making it the most suitable method for forming cones and rectifier plates. The flame-holding ring 9 is made of metal with excellent heat resistance and is formed into an annular body having a substantially V-shaped or U-shaped cross section, and is placed in front of the current plate 6 with the convex surface facing the current plate 6 and the burner cone 5 side. established in The flame-holding ring 9 has an outer diameter of 130 mm, an inner diameter of 104 mm, the same diameter as the outlet of the burner cone 6, and a length of 15 m/m, with the rear end extending from the front end of the burner cone 6. Rectifying plates 8 at intervals of 12m/m
located in front of. In the figure, reference numeral 19 denotes igniters, and a pair of igniters are provided at positions close to the fuel spray nozzle 3 so as not to obstruct the flow of air from the air outlet 4. Therefore, in such burner A, the blower 11
When the electromagnetic pump 15 is operated and the igniter 19 is ignited, the spark from the igniter 19 ignites the mixture of fuel sprayed from the fuel spray nozzle 3 and air blown from the air outlet 4, and the burner cone is ignited. 6 Yellow flame is formed in the center. Furthermore, the air is blown out from the air outlet 4, thereby producing a suction effect and sucking the surrounding air. As a result, from the outlet of the burner cone 6, the gap between the inlet of the burner cone 6 and the air outlet 4,
That is, a circulating flow is generated that passes through the combustion gas suction port 5 and reaches the inside of the cone 6. After ignition, hot combustion gas is sucked into the burner cone 6 by the above-mentioned circulation action, and the atomized fuel is instantaneously vaporized by the heat. The vaporized fuel is cone 6
Along the inner surface, an oxygen-deficient layer C is formed together with the circulating gas, and the gas flows to the constriction part 20 formed between the outlet part of the cone 6 and the current plate 8, and in this part 20, the cone 6
Mixing with the combustion air flowing into the center is promoted. Then, the yellow flame inside the burner cone 6 moves to the downstream part of the baffle plate 8 at the same time as it sucks in the combustion gas,
At this point, the mixture ignites and becomes a blue flame. On the other hand, the oil droplets sprayed from the spray nozzle 3 and not vaporized by the suctioned combustion gas collide with the inner circumferential surface of the burner cone 6, especially the inner circumferential surface of the expanded portion.
Since the cone 6 is made of water-absorbing porous ceramic, it is once sucked and held within the ceramic. Since the cone 6 is heated to a high temperature due to convection heat transfer by the high-temperature combustion gas, the inhaled fuel quickly evaporates and vaporizes and flows to the outlet of the cone 6, and then passes through the baffle plate 8 and the cone outlet 20. It is mixed with air and ignited in the downstream part of the current plate 8, that is, in the recessed part behind the current plate 8. The concave portion behind the baffle plate 8 serves as a retention point for the airflow, and high-temperature combustion gas is retained in this portion, causing the cone 6
It is released from the outlet, vaporizes, and becomes a source of ignition for the fuel gas mixed with air. Therefore, blue flame will come out from the small holes 7 made in the current plate 8. In addition, the rectifying plate 8 is made of porous ceramic that has the same water absorption properties as the burner cone 6, so that it functions as a fuel vaporizing surface in the same way as the burner cone 6, in addition to rectifying the airflow and serving as an ignition source. becomes possible. Further, the unburnt gas that has not been ignited at the end of the current plate 8 flows along the inner and outer peripheral surfaces of the flame stabilizing ring 9 and is ignited in the recessed portion behind the flame stabilizing ring 9. The recess behind the flame-holding ring 9 serves as a retention point for airflow, similar to the recess behind the baffle plate 8, and high-temperature combustion gas accumulates in this part, causing ignition of unburned gas that was not ignited in the baffle plate 8. Become the source. Therefore, a stable blue flame stands at the end of the flame-holding ring 8. Thus, achieving the intended purpose. In addition, in this application, the output range is from 23000 to
Although this relates to an evaporative burner with an output of 57,000 Kcal/H, the intended purpose can be achieved if the shape of the present application is similarly enlarged for outputs higher than this.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a diagram showing separation of burner spaces in the method of the present invention, and FIG.
The figure is a sectional view of the main parts of a water heater equipped with a burner that implements the method of the present invention, Figure 3 is a front view of the burner with a portion cut away, and Figure 4 shows the process of burning kerosene. The flowchart, FIG. 5, is a graph showing the generation of soot and carbon monoxide when the method of the present invention is implemented in comparison with when the conventional method is implemented. A... Burner, 1... Nozzle holder, 2...
...Combustion chamber, 3...Fuel spray nozzle, 4...Air outlet, 5...Suction port for high temperature combustion gas, 6...Burner cone, 6a...Cylindrical part, 6b...Enlarged part, 7... ...small hole, 8... rectifier plate, 9... flame holding ring, a... nozzle area, b... combustion air region, c...
...Fuel vaporization region, d...Mixing region, e...Combustion region, f
...High temperature combustion gas circulation area.

Claims (1)

[Claims] 1 A fuel spray nozzle, an air outlet provided around the fuel spray nozzle surrounding the nozzle and coaxial with the nozzle, and a rear part made of water-absorbing porous ceramic having a substantially cylindrical shape, and a front end of the cylindrical part. forming a tapered tubular widening part that continuously widens forward at an angle slightly narrower than the spray angle of the nozzle, surrounding the fuel spray area of the fuel spray nozzle and coaxially with the nozzle and the air outlet; a porous burner cone that forms a combustion gas suction port between the rear end opening and the air outlet; A suitable number of small holes are formed at appropriate positions other than the porous tip, a convex surface is provided inside the burner cone at the outlet opening at the front end of the porous burner cone, and the porous burner cone is arranged coaxially with the burner cone.
By using a porous baffle plate having an appropriate gap between it and the burner cone outlet rim, a combustion air region is provided in the center in front of the nozzle region, and a fuel vaporization region layer is provided in the periphery thereof. A mixing zone and a combustion zone are sequentially formed, and a high-temperature combustion gas circulation zone is formed on the outer periphery of the porous burner cone to completely separate each zone, and the majority of oil droplets sprayed from the nozzle in the nozzle zone are is applied to a porous burner cone and a porous rectifier plate, and is evaporated and vaporized by the heat of the high-temperature combustion gas and the heat of the porous burner cone and porous rectifier plate to form a primary vaporized fuel body. The remaining part of the oil droplets that did not reach the temperature are mixed with the high-temperature gas coming from the high-temperature combustion gas circulation region to form a secondary vaporized fuel body, and the primary and secondary vaporized fuel bodies together constitute the fuel vaporization region. At the same time, the remaining oil droplets are mixed with a part of the combustion air in the fuel-air region to form a mixed fuel body, and then the primary and secondary vaporized fuel bodies, the mixed fuel body, and the remainder of the combustion air are added to the mixing region. A combustion method in a liquid fuel vaporization burner characterized by feeding the gas, mixing them to form a combustion gas body, and burning the combustion gas body in a combustion zone to obtain a blue flame.