JPH0124963B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat exchanger equipped with a combustion device that gasifies and burns a mixture of air and fuel by circulating combustion gas through a mixing tube provided in front of a spray nozzle. BACKGROUND ART Conventionally, combustion devices such as oil water heaters include a type called a gun-type burner. This involves igniting and burning a mixture of fresh air sent from a blower and atomized fuel pressurized by an electromagnetic pump or the like and sprayed from a spray nozzle using a high-pressure electric discharge or the like. However, with this conventional method, the amount of air in the mixed mist is large, resulting in yellow flame combustion, resulting in poor combustion efficiency, and the carbon particles generated by yellow flame combustion adhere to the heat transfer surface inside the casing, reducing heat exchange efficiency. In addition, there was a drawback that the combustion noise caused by the vibration of the flame was loud. Recently, there has been a demand for high combustion efficiency, low noise, and clean exhaust gas from the viewpoint of energy conservation and the environment, and so-called rotary gasification burners or heater gasification systems that gasify fuel oil and combust it with blue flame have recently been introduced. A burner has been developed. However, the former method had the disadvantage that the gasification of the fuel oil was insufficient at the time of ignition and extinguishment, resulting in odor. Moreover, the latter method requires a long time to preheat the heater, which is inconvenient in use, and has the disadvantage that it requires complicated control of the heater. Furthermore, both had the disadvantage that their fuel oil gasification structures were complicated and required special skills for maintenance and inspection. As a solution to the above-mentioned drawbacks, the applicant has
We have applied for a heat exchange device in Japanese Patent Application No. 57-83799. That is, as shown in FIG. 1, the heat exchange device 29 includes a cylindrical combustion chamber 33 formed inside a housing 32, and a spray nozzle installed inside a blow pipe 35 facing the combustion chamber 33. 34 is installed in the combustion chamber 33 and in front of the spray nozzle 34, a mixing pipe 30 having a flame stabilizing plate 31 inside is installed between the mixing pipe 30 and the blower pipe 35. It forms a gas inlet 36 and is installed so that the combustion flame extension center line G of the mixing tube 30 and the longitudinal center line H of the combustion chamber are perpendicular to each other. However, in the heat exchange device 29, the combustion flame extension center line G of the mixing tube and the longitudinal center line H of the combustion chamber 33 are perpendicular to each other, so that the combustion gas (not shown) ejected from the mixing tube 30 is mixed. After being sprayed onto the inner peripheral wall surface 32a facing the pipe 30, the inner peripheral wall surface 3
The gas is dispersed into gas that rises toward the exhaust side along the longitudinal direction of the inner peripheral wall surface 32a, and gas that flows along the circumferential direction of the inner peripheral wall surface 32a. The gas dispersed clockwise and counterclockwise along the circumferential direction of the inner circumferential wall surface 32a collides on the inner circumferential wall surface 32a on the side where the mixing tube 30 is installed, and then the gas is sucked into the mixing tube 30. The remaining gas rises toward the discharge side along the longitudinal direction of the inner circumferential wall surface 32a. In this way, when looking at the device as a whole, most of the combustion gas is caused by the kinetic force component in the longitudinal direction of the inner peripheral wall surface 32a being larger than the kinetic force component in the circumferential direction of the inner peripheral wall surface 32a. The contact movement distance between the inner peripheral wall surface 32a and the inner peripheral wall surface 32a becomes shorter,
The combustion gas is discharged to the outside without sufficient contact with the inner circumferential wall surface 32a, which is a heat transfer surface. As a result, the conventional heat exchange device 29 has a drawback of low heat exchange efficiency. In view of the above-mentioned drawbacks of the conventional technology, the present invention further improves the technology related to the above-mentioned unknown combustion device, which was previously filed by the present applicant. It is an object of the present invention to provide a heat exchange device with high heat exchange efficiency that can sufficiently make contact with an inner circumferential wall surface which is a hot surface. Hereinafter, the present invention will be explained based on embodiments shown in the drawings. FIGS. 2 and 3 show a heat exchange device 1 according to an embodiment of the present invention. The main improvement of the heat exchange device 1 is that the extension center line B of the combustion flame ejected through the mixing tube 20 is different from the longitudinal center line A extending through the center of the combustion chamber 3 toward the exhaust side. Position the mixing tube 20 so that it follows an arbitrary cross section C that intersects perpendicularly, and position the combustion flame extension center line B of the mixing tube 20 toward the outside of the combustion chamber 3 by an appropriate dimension D with respect to the vertical center line A. The point is that it is eccentric to the center. The housing 2 has a double pipe structure in which a water chamber 2c is formed between an outer circumferential wall 2b and an inner circumferential wall 2a, and has an appropriate cross-sectional shape surrounded by the inner circumferential wall 2a, such as a circular cross-section or a polygonal cross-section. A cylindrical combustion chamber 3 is formed. The outer periphery of the housing 2 is covered with a heat insulating material 5. Note that the housing 2 is not limited to a cylindrical shape, and may have a cross-sectional shape that changes along the longitudinal direction, such as a spherical or conical shape, although not shown. Further, the housing 2 is not limited to the double pipe structure, and although not shown, it may of course have a structure in which a long small diameter pipe is wound spirally to form a combustion chamber inside. It is possible, and any structure may be used as long as the inner circumferential wall surface forming the combustion chamber is a heat transfer surface for heat exchange. A predetermined gap W is provided within the combustion chamber 3 and at a front position of the blow pipe 10, which will be described later.
(for example, 15 mm), the mixing tube 20 passes through the center of the combustion chamber 3 and extends the combustion flame along a cross section C perpendicular to the vertical center line A extending toward the exhaust side (upward in the illustrated embodiment). Position the center line B, and move the combustion flame extension center line B toward the outside of the combustion chamber 3 by an appropriate dimension D (for example, 1/3 to 1/2 of the radius of the combustion chamber 3) with respect to the vertical center line A. It is installed eccentrically to. This gap W allows the mixing pipe 20 and the blower pipe 10 to
A circulating gas inlet (hereinafter referred to as a circulating inlet) 16 is located between the housing 2 and the combustion chamber 3.
It is formed near the inner peripheral wall 2a of. As shown in FIG. 4, the flame stabilizing section 15 having a multi-tube structure including the mixing tube 20 has a flame stabilizing plate 17 made of punched stainless steel metal or the like installed near the center thereof, and a flame stabilizing plate 17 made of punched metal made of stainless steel or the like is installed on the outer periphery of the flame stabilizing plate 17 in the downstream direction. A tapered cone-shaped flame-holding tube 18 that expands is installed. and,
A sub-flame-holding tube 19 made of stainless steel punched metal or the like is installed on the outer periphery of this flame-holding tube 18.
Furthermore, a mixing tube 20 is installed around the outer periphery of this. The flame stabilizing plate 17, the flame stabilizing tube 18, the sub flame stabilizing tube 19, and the mixing tube 20 are connected by support legs 21, 21..., and the mixing tube 20 is connected to the blower tube 10 by legs 22, 22... It is suspended in Note that the flame-holding tube 18 and the sub-flame-holding tube 19 are installed as necessary, and are not necessarily required. A spray nozzle 8 is installed behind the flame holding section 15 so as to be substantially coaxial with the combustion flame extension center line B, and sprays fuel oil pressurized by a hydraulic pump 7 (see FIG. 2). It is configured to eject in the form of fine particles. A blow pipe 10 is installed around the outer periphery of the spray nozzle 8 for blowing fresh air blown by a blower 9 (see FIG. 2) to the mixing pipe 20. A high-speed air jetting plate 11 is installed at the opening at the tip of the blast pipe 10 . This ejection plate 11
is the central nozzle 1 that spouts out atomized fuel and fresh air.
2, and a plurality of air jet holes 13 which are formed at appropriate circumferential pitches at a predetermined distance from the center. Each of the air ejection holes 13 is inclined at a predetermined angle in the circumferential direction, and creates a swirling flow in the ejected air to further refine the fuel particles and uniformly distribute the mixture of atomized fuel and fresh air. I have to. Reference numeral 14 denotes an electrode rod that generates a spark using high-voltage electricity near the tip of the spray nozzle 8 and ignites the fine particles of fuel oil that are ejected. In FIG. 1, 25 is a combustion tube, 24 is an exhaust chimney, 26 is a water supply port, and 27 is a hot water supply port. Next, the operation of the fuel exchange device 1 configured as described above will be explained based on the case where the fluid to be heat exchanged is water, the fuel oil is kerosene, and the amount of kerosene supplied and the amount of fresh air supplied are constant. do. The atomized kerosene particles ejected from the spray nozzle 8 are ignited by the spark of the electrode rod 16, and at first start yellow flame combustion near the tip of the ejection plate 11. In this condition there is an excess of air. After that, this combustion flame gradually moves in the spray direction, propagates to the sub-flame stabilizing cylinder 19, and further moves to the flame stabilizing plate 17,
The flow is rectified on the way to the flame stabilizing plate 17, stabilized at the flame stabilizing plate 17, and guided to the flame stabilizing tube 18 to maintain steady combustion. In this way, the auxiliary flame stabilizing cylinder 19 functions to smooth the propagation of the combustion flame when it moves to the flame stabilizing plate 17. In addition, the ejection plate 1
1. When the flame-holding tube 18 and the sub-flame-holding tube 19 are not installed, stable combustion is started and maintained on the flame-holding plate 17 by spark ignition near the flame-holding plate 17. As shown in FIG. 3, the combustion gas is blown around the intersection of the combustion flame extension center line B and the inner circumferential wall 2a of the casing 2, and a part of it is blown inside the casing 2 due to the kinetic energy of the combustion gas. It flows along the peripheral wall surface 2a' in the direction of arrow F and reaches the circulation inlet 16 while exchanging heat with the water in the water chamber 2c. And the combustion gas is
The negative pressure generated by the swirling airflow that passes through the gap W from the blast pipe 10 to the mixing pipe 20 at high speed forces the air into the mixing pipe 20 and instantly mixes it into a mixed mist of kerosene particles and fresh air. On the other hand, the combustion gas dispersed in the direction of the arrow E flows upward while circulating spirally along the circumferential direction of the inner peripheral wall surface 2a' of the housing 2 due to the kinetic energy of the combustion gas, and flows upward toward the inner peripheral wall surface 2a'. The combustion tube 25 and the exhaust chimney 2 while sufficiently exchanging heat with the water in the water chamber 2c during the long period of contact with the combustion tube 25 and the exhaust chimney 2.
4 and is discharged to the outside. That is, since the combustion flame extension center line B of the mixing tube 20 is oriented eccentrically toward the outside of the combustion chamber 3 by an appropriate dimension D with respect to the longitudinal center line A of the combustion chamber 3, most of the combustion gas is flows upward while circulating spirally along the circumferential direction of the inner peripheral wall surface 2a of the housing 2. Therefore, the chances of the combustion gas coming into contact with the inner circumferential wall surface 2a of the casing 2 are greatly increased, and the contact occurs for a long time, during which heat exchange is sufficiently performed. Therefore, it is possible to dramatically improve heat exchange efficiency. The circulating combustion gas sucked into the mixing tube 20 warms the mixed mist of very fine kerosene particles and fresh air due to the swirling airflow, and instantly gasifies the kerosene particles or into a state close to this. Make it. Therefore, the combustion state becomes gasification combustion or a state close to this, and blue flame combustion from the flame stabilizing plate 17 is obtained. In other words, kerosene particles, fresh air, and circulating combustion gas are mixed in the mixing tube 20 and then rectified, and what used to be combustion with excess air becomes an ideal combustion that is close to the stoichiometric air ratio and is rectified. Become. Therefore, combustion with low combustion noise and excellent heat exchange efficiency can be obtained. From then on, this blue flame combustion is maintained. In order to obtain the above-mentioned blue flame combustion, it is necessary to mix an appropriate amount of combustion gas into the mixed mist of fresh air and kerosene particles. ) is the problem. Therefore, in this example, we conducted experiments by changing the flow rate of the ejected air, which has the greatest effect on the negative pressure, and as a result, we were able to set a flow rate that was sufficient to suck in the amount of combustion gas required for the ideal air ratio. . The factors that affect the flow velocity of the ejected air are the diameters of the central ejection hole 12 and the air ejection hole 13 and the diameters of both the air ejection holes 12 and The area ratio is 13. In addition,
The number of air ejection holes 13 and the distance between the central ejection hole 12 and the air ejection hole 13 have little effect on the flow velocity of the ejected air and can be ignored. however,
If the distance between the two nozzles 12 and 13 exceeds an optimum value, good mixing of kerosene particles and air will not be achieved. In the case of this embodiment in which the diameter of the blast pipe 10 was 80 mm (combustion output was 35000 Kcal/Hr), the distance between the central nozzle 12 and the air nozzle 13 was appropriately 32 mm. Tables 1 and 2 are experimental results showing the relationship between the diameter of the ejection holes 12 and 13 and the air flow velocity and amount of air supplied when ejected from the ejection holes 12 and 13 into the natural atmosphere.

[Table] As is clear from Table 1, if the diameter of the air ejection holes 13 is made smaller, the flow velocity of the ejected air becomes faster and the negative pressure generated at the circulation inlet 16 becomes larger. However, the amount of supplied air tends to decrease as the diameter of the air jet hole 13 becomes smaller. For this reason,
A hole diameter of 8 mm is required to ensure a sufficient amount of supplied air and a high flow rate.

[Table] However, the opening ratio of the hole 12 above refers to the opening ratio of the central nozzle 1.
The opening area of 2 is the center nozzle 12 and the air nozzle 1.
It is the value obtained by multiplying the value divided by the sum of the opening areas of 3 by 100. Further, as is clear from Table 2, if the hole diameter of the central jet hole 12 is made smaller, the flow velocity becomes faster, but the amount of supplied air decreases. Furthermore, the ratio of the opening area of the central jetting hole 12 to the total opening area of the central jetting hole 12 and the air jetting hole 13 takes a value proportional to the amount of air. Therefore, if we consider the balance between the amount of supplied air and the flow rate of the ejected air, the center ejection hole 12
The optimum diameter is 18 to 20 mm. The diameter of the central nozzle 12 is 18 mm, and the air nozzle 13 is
The actual air flow velocity was measured to be 21 m/sec, assuming that the diameter of the air blowing hole 13 was 8 mm, the diameter of the air blowing pipe 10 was 80 mm, and the actual air flow velocity was 21 m/sec. For your reference,
The air flow velocity of conventional commercially available combustion equipment is usually
It was about 12.5m/sec. In short, the flame stabilizing section 15 warms the kerosene particles in the mixing tube 20 with circulating combustion gas to turn them into a gasified state or a state close to this, and also adds combustion gas to the mixed mist of air and kerosene particles. Since blue flame combustion is performed at an air-to-air ratio, a large amount of heat is generated for a given amount of fuel, resulting in excellent thermal efficiency. Furthermore, since it is a rectified blue flame combustion, it also has the advantage of low combustion noise. As explained above, the heat exchange device according to the present invention has the following excellent effects. so that the extended center line of the combustion flame ejected through the mixing tube is along any cross section perpendicular to the longitudinal center line extending through the center of the combustion chamber to the exhaust side;
Since the posture of the mixing tube is positioned so that the center line of the combustion flame extension of the mixing tube is eccentric to the outside of the combustion chamber by an appropriate amount with respect to the vertical center line, most of the combustion gas is , flows upward while circulating spirally along the circumferential direction of the inner peripheral wall of the casing, and after sufficiently exchanging heat while in contact with the inner peripheral wall for a long time, it is discharged to the outside. Efficiency can be improved. In addition, by circulating the combustion gas through the mixing tube to warm the fuel particles, it is brought to a state close to gasification, and by adding combustion gas to the mixture of fresh air and fuel particles, the air ratio is close to the stoichiometric air ratio. By burning with a blue flame, a large amount of heat is generated for a given amount of fuel, and the device has excellent thermal efficiency. Furthermore, the combustion flame is a steady blue flame,
The rectifying effect of the mixing tube has the advantage of low combustion noise.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a conventional heat exchange device, Fig. 2 is a longitudinal cross-sectional view showing an embodiment of the heat exchange device according to the present invention, Fig. 3 is a cross-sectional view of the same, and Fig. 4 is a mixing tube. FIG. 2... Housing, 3... Combustion chamber, 8... Spray nozzle, 10... Air pipe, 16... Circulation inlet, 20
... Mixing tube, A ... Vertical center line, B ... Combustion flame extension center line, C ... Cross section.

Claims (1)

[Claims] 1. A combustion air blowing pipe whose tip is open facing a cylindrical combustion chamber formed in a cylindrical housing, and a central blowing hole and a circumferential blowing pipe arranged to cover the tip opening of the blowing tube. a high-speed air ejection plate having air ejection holes at the top; a spray nozzle and an ignition electrode disposed inside the blast pipe; Tapered cone-shaped mixing tubes connected and arranged so that their cores match, and a porous or mesh-shaped flame stabilizing plate provided at the center of the mixing tube and facing directly in the spraying direction of the spray nozzle. and an annular inlet having a size that allows the combustion gas circulating along the wall of the cylindrical combustion chamber to flow into the rear end opening of the mixing tube is provided at the connecting portion between the blower tube and the mixing tube. In the heat exchange device having a combustion device, the mixing tube is installed in such a manner that the extension center line of the combustion flame ejected through the mixing tube is a vertical center line extending through the center of the combustion chamber toward the exhaust side. A heat exchange device characterized in that the heat exchange device is positioned along an arbitrary cross section orthogonal to the vertical center line, and is oriented eccentrically toward the outside of the combustion chamber by an appropriate dimension with respect to the longitudinal centerline.