Combustion device and hot water device equipped therewith

Abstract

To provide a combustion device capable of eliminating an erroneous backfire detection, improving accuracy of backfire detection, and suitably suppressing its components from being thermally damaged by a backfire flame.SOLUTION: A combustion device C comprising a combustion unit 4 for combusting fuel gas, a mixed gas supply path 3 for supplying the combustion unit 4 with mixed gas of fuel gas and air, and a flame sensor 5 positioned in the mixed gas supply path 3 or disposed on a position facing the same, and capable of optically detecting a backfire flame when a backfire occurs from the combustion unit 4 in the direction of the mixed gas supply path 3, is characterized by further comprising a shield 6 that prevents a backfire flame and flame light of normal combustion respectively, from proceeding to the flame sensor 5 from the combustion unit 4.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a combustion device and a hot water device such as a water heater equipped with the same.

Background Art

[0002] As a specific example of the combustion device, there is one described in Patent Document 1. In the combustion device described in the document, a mixed gas of fuel gas and air is supplied to a porous combustion plate having a plurality of ventilation holes, and the fuel gas in the mixed gas that has permeated outside the combustion plate is combusted outside the combustion plate. A light quantity detection means is provided on the upper wall portion of the mixed gas supply path for fuel gas and air provided in front of the combustion plate, and when backfire occurs, it can be detected by using the light quantity detection means. Backfire is a cause of accidents such as equipment damage. According to the above configuration, when backfire occurs, it can be detected and appropriate countermeasures can be taken.

[0003] However, in the above prior art, there are problems to be solved as described below.

[0004] That is, the light quantity detection means is provided so that light from the combustion plate is incident thereon. Not only when backfire occurs, but also when normal combustion of the fuel gas is being performed, the light of the flame is detected by the light quantity detection means. Therefore, even though normal combustion is being carried out, there may be a case where backfire is erroneously detected based on the detection of the light of the flame of this normal combustion. Conversely, even though backfire has occurred, the light detected at that time may be considered to be the light from the flame during normal combustion, and the backfire may be overlooked. It is desired that such false detection be appropriately eliminated. Flashfire occurs when the supply rate of the fuel mixture slows down compared to the combustion rate of the fuel gas. In recent years, however, policies to realize a low-carbon society have been promoted from the perspective of protecting the natural environment, and as a measure to achieve this, the use of hydrogen as the fuel gas is being considered. However, hydrogen burns much faster than city gas or LPG, which are commonly used as fuel gases. Therefore, when hydrogen is used as the fuel gas, the possibility of flashfire increases. Considering this situation, it can be said that there is a great need to improve the accuracy of flashfire detection.

[0005] Furthermore, in the aforementioned conventional technology, when a flashback occurs, there is a risk that the flame will travel towards the light intensity detection means. This could cause thermal damage to the light intensity detection means, making it difficult to detect flashbacks using this means afterward. In such cases, it becomes necessary to replace the components of the light intensity detection means, which places a burden on the user in terms of labor and cost. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 3100328 [Patent Document 2] Japanese Utility Model Publication No. 56-4759 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The present invention was conceived under the circumstances described above, and provides a combustion device and a hot water device equipped therewith that can eliminate false detection of flashbacks, improve the accuracy of flashback detection, and appropriately suppress problems in which components suffer thermal damage due to flashback flames. The goal is to provide it. [Means for solving the problem]

[0008] To solve the above problems, the present invention employs the following technical measures.

[0009] A combustion apparatus provided in a first aspect of the present invention comprises: a combustion section for burning a fuel gas; a mixed gas supply passage for supplying a mixed gas of the fuel gas and air to the combustion section; and a flame sensor located in or facing the mixed gas supply passage and capable of optically detecting a flashback flame when a flashback occurs from the combustion section to the mixed gas supply passage, wherein the combustion apparatus further comprises a shielding section that prevents the flashback flame from reaching the flame sensor from the combustion section and prevents the light of the flame during normal combustion from traveling from the combustion section to the flame sensor.

[0010] This configuration yields the following effects: In other words, the light from the flame during normal combustion of fuel gas in the combustion chamber is prevented from traveling from the combustion chamber towards the flame sensor by the shielding unit, thus preventing the flame light from being detected by the flame sensor. Therefore, the risk of the flame light during normal combustion being mistakenly identified as the light from a flashback can be appropriately eliminated. When a flashback occurs, the flame is appropriately detected by the flame sensor when it is not obstructed by the shielding unit and enters the detection range of the flame sensor. Therefore, when a flashback occurs, it is possible to appropriately detect it. As a result, the accuracy of flashback detection can be improved. Furthermore, according to the present invention, when a flashback occurs, the shielding prevents the flashback flame from traveling from the combustion chamber towards the flame sensor. Therefore, malfunctions such as thermal damage to the flame sensor causing failure due to flashback can be appropriately prevented or suppressed. Since the need to replace a faulty flame sensor is eliminated or reduced, the user's workload and financial burden of parts replacement are also reduced.

[0011] In the present invention, preferably, the shielding portion includes a partition wall portion provided to separate the combustion portion and the flame sensor.

[0012] With this configuration, the direct propagation of the flame from the combustion section towards the flame sensor, as well as the light from the flame during normal combustion, can be appropriately prevented by using a simple partition wall, thereby enabling the intended effect of the present invention to be properly achieved.

[0013] In the present invention, preferably, the shielding portion includes a cover member that surrounds the flame sensor and partially has an opening that faces the upstream side in the mixed gas flow direction of the mixed gas supply passage, and is configured such that when the flashback flame travels through the mixed gas supply passage in the region opposite the opening, the light of this flame is detected by the flame sensor.

[0014] With this configuration, the flame sensor is surrounded by a cover member, making it less susceptible to exposure to flashback flames and more reliably preventing the flame sensor from failing due to flashback. On the other hand, when a flashback flame travels through the mixed gas supply path to the area opposite the opening of the cover member, the light from the flame is reliably detected by the flame sensor at that point, thereby significantly improving the accuracy of flashback detection.

[0017] In the present invention, preferably, the flame sensor is located in an area outside the combustion section that does not overlap the combustion section in the vertical direction.

[0018] This configuration simplifies the wiring and installation of the flame sensor. Furthermore, it reduces its exposure to flashback flames, making it more reliable to prevent the flame sensor from failing due to flashback.

[0019] A hot water device provided by a second aspect of the present invention is characterized by comprising a combustion device provided by a first aspect of the present invention.

[0020] According to such a configuration, the same effects as those described for the combustion device provided by the first aspect of the present invention can be obtained.

[0021] Other features and advantages of the present invention will become more apparent from the following description of the embodiments of the invention with reference to the accompanying drawings.

Brief Description of the Drawings

[0022] [Figure 1] (a) is a schematic cross-sectional view of the main part schematically showing an example of the combustion device according to the present invention and a hot water device equipped with the same, and (b) is a cross-sectional view taken along the line Ib-Ib of (a). [Figure 2] (a) is a schematic cross-sectional view of the main part schematically showing another example of the combustion device according to the present invention and a hot water device equipped with the same, and (b) is a cross-sectional view taken along the line IIb-IIb of (a). [Figure 3] (a) is a schematic cross-sectional view of the main part schematically showing another example of the combustion device according to the present invention and a hot water device equipped with the same.

Embodiments for Carrying Out the Invention

[0023] Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.

[0024] The combustion device C shown in FIG. 1 is used as a component of a hot water device WH to be described later, and includes a first and a second case 1, 2, a mixed gas supply passage 3 formed in the first case 1, a combustion section 4 configured using a combustion plate 40, a flame sensor 5 for detecting flashback, and a shielding section 6 for flame and light. The hot water device WH further includes a heat exchanger 7 disposed in the second case 2 in addition to the combustion device C. Heat is recovered from the combustion gas generated by the combustion section 4 by the heat exchanger 7, so that the hot and cold water fed into the heat exchanger 7 is heated to generate hot water, and this hot water is discharged to a desired hot water supply destination.

[0025] The mixed gas supply passage 3 is a supply passage that mixes the fuel gas and air supplied into the first case 1 from the fuel gas supply port 3a and air supply port 3b provided in the first case 1, and guides this mixed gas to the combustion section 4. The fuel gas is, for example, hydrogen or a hydrogen-containing gas. However, it is not limited to this, and other types of gas such as city gas or LP gas can also be used. Air is supplied to the mixed gas supply passage 3 by taking in external air using a fan 9. The mixed gas supply passage 3 is defined by a plurality of wall sections 33a, 33b and is serpentine in a front or side cross-sectional view, which is preferable for promoting stirring and mixing of the fuel gas and air.

[0026] The combustion section 4 is the part where the fuel gas in the mixed gas burns, and includes a combustion plate 40 located at the end of the mixed gas supply passage 3. The combustion plate 40 is a heat-resistant plate having a plurality of vent holes 40a (flame holes), and an ignition plug (not shown) is provided near its lower surface. The fuel gas in the mixed gas that passes downward through the plurality of vent holes 40a burns in the lower surface region of the combustion plate 40, and the combustion gas proceeds toward the heat exchanger 7 described above. The combustion plate 40 is attached to both or one of the first and second cases 1 and 2 using, for example, a frame-shaped support wall 68. This support wall 68 blocks the region of the end of the mixed gas supply passage 3 where the combustion plate 40 is not provided. In addition to being made of a plate material with flame holes, the combustion plate 40 may also be made of metal knit or metal fiber with flame holes.

[0027] The flame sensor 5 is used to optically detect the flashback flame that occurs when flashback occurs from the combustion section 4 to the mixed gas supply passage 3. It is, for example, an ultraviolet sensor (omnidirectional type (however, a directional type may also be used)), and its detection signal is input to a controller (not shown) that controls the combustion device C and the hot water device WH. The flame sensor 5 is inserted into the first case 1 from the outside, penetrating the side wall portion 10 of the first case 1, and is positioned above the support wall portion 68. The flame sensor 5 is positioned within or facing the mixed gas supply passage 3 so as not to overlap with the combustion section 4.

[0028] The shielding portion 6 is a part that prevents the flame from flashing back from the combustion portion 4 to the flame sensor 5, as well as the light from the flame during normal combustion, from traveling. It includes a partition wall portion 60 that rises upward from the support wall portion 68 to separate the combustion portion 4 and the flame sensor 5. A part of the support wall portion 68 also separates the combustion portion 4 and the flame sensor 5, preventing the flame from flashing back from the combustion portion 4 towards the flame sensor 5, as well as the light from the flame during normal combustion, from traveling. Therefore, in this embodiment, the combined structure of a part of the support wall portion 68 and the partition wall portion 60 constitutes the shielding portion 6. This shielding portion 6 has heat resistance and light-shielding properties. As shown in Figure 1(b), the width La of the partition wall portion 60 should be a width that is sufficiently larger than the width Lb or diameter of the flame sensor 5.

[0029] The mixed gas supply passage 3 has first and second regions S1 and S2, which are regions close to the combustion section 4 (combustion plate 40). The first region S1 corresponds to the terminal region adjacent to the upper side of the entire combustion section 4 so that the mixed gas is supplied to the entire area of ​​the combustion section 4. In contrast, the second region S2 is narrower in width (width in the left-right direction in Figure 1(a)) than the first region S1, and is connected to one end of the first region S1 in the width direction, and is positioned offset from the center of the combustion section 4 in the width direction, and extends in the vertical height direction. The mixed gas flows from the second region S2 to the first region S1.

[0030] The partition wall 60 constituting the shielding section 6 is positioned at the boundary between the first and second regions S1 and S2 so as not to completely close the boundary between them. The flame sensor 5 is positioned offset from the combustion section 4 in the same direction as the displacement of the second region S2. A gap 11 is formed between the partition wall 60 and the side wall 10 of the first case 1, allowing the flame sensor 5 to face the second region S2. As indicated by the symbol Na, when a flashback flame progresses into the second region S2, ultraviolet rays emitted from the flame pass through the gap 11 and reach the flame sensor 5. It is configured to be detected.

[0031] Preferably, the area where the light is expected to hit is a region with low ultraviolet reflectivity, such as a painted area with ultraviolet absorption properties, so that the light from the flame during normal combustion in the combustion section 4 is reflected by the inner surface of the first case 1 or the wall portion 33b and does not reach the flame sensor 5. Furthermore, the anti-reflective structure is not limited to the aforementioned coating; for example, it may also be a structure that prevents reflection by applying a surface treatment such as plating to suppress reflection, or by roughening the surface with a matte finish.

[0032] Next, the operation of the combustion device C and the hot water device WH described above will be explained.

[0033] In the combustion section 4, when the fuel gas in the mixed gas is burning normally, the light (ultraviolet rays) from the flame generated at that time is prevented from traveling from the combustion section 4 towards the flame sensor 5 by the shielding section 6. Therefore, the light from the flame is not detected by the flame sensor 5, and the risk of the light from the flame during normal combustion being mistakenly detected as the light from a flashback is effectively eliminated.

[0034] On the other hand, if the supply rate of the fuel mixture is slower than the combustion rate of the fuel gas, flashback will occur. However, the shielding unit 6 prevents this flashback flame from directly traveling from the combustion unit 4 towards the flame sensor 5 and reaching it. Therefore, the risk of the flame sensor 5 malfunctioning due to thermal damage from contact with the flashback flame is eliminated, and flashback detection using the flame sensor 5 can be continued appropriately.

[0035] If a flashback occurs, the flame travels upstream in the mixed gas supply passage 3 in the direction of mixed gas flow. It travels from the first region S1 to the second region S2 of the mixed gas supply passage 3 and reaches the position indicated by the symbol Na in Figure 1(a). The light (ultraviolet light) emitted from the flashback flame is then appropriately received and detected by the flame sensor 5. Based on this, the controller determines that a flashback has occurred and takes appropriate countermeasures. As described above, flashback detection is performed when the flashback flame advances into the second region S2. The second region S2 is narrow, and the flame sensor 5 is positioned to directly face this second region S2. Therefore, the flashback flame can be reliably received and detected by the flame sensor 5, thereby improving the accuracy of flashback detection.

[0036] Figures 2 and 3 illustrate other embodiments of the present invention. In these figures, elements identical or similar to those in the previous embodiments are denoted by the same reference numerals, and redundant explanations are omitted.

[0037] In the combustion device Ca and hot water device WHa shown in Figure 2, the shielding portion 6A is configured to include a cover member 63 having a plurality of side wall portions 61a to 61c surrounding the flame sensor 5 and an upper wall portion 62 with an upward-facing opening 62a. The opening 62a faces the second region S2 of the mixed gas supply passage 3. The side wall portion 61a corresponds to the partition wall portion 60 in the embodiment shown in Figure 1.

[0038] According to this embodiment, since the flame sensor 5 is surrounded by the cover member 63 of the shielding part 6A, exposure to flashback flames is more reliably prevented, and the prevention of flame sensor 5 failure can be further thoroughly addressed. Furthermore, the detection of the flame light during normal combustion in the combustion part 4 by the flame sensor 5 can be more thoroughly prevented. On the other hand, when the flashback flame proceeds into the second region S2 of the mixed gas supply path 3, this flame fires The flame sensor 5 ensures reliable detection, and, as in the above embodiment, it is possible to improve the accuracy of flashback detection.

[0039] In the combustion device Cb and hot water device WHb shown in Figure 3, the shielding section 6B is configured as a holder section 64 that holds the flame sensor 5B, and since this holder section 64 is inserted into the first case 1 from the outside, the holder section 64 is also located inside the first case 1. The holder section 64 is equipped with side wall sections 64a and bottom wall sections 64b, etc., which prevent the light of flames that have flashed back from the combustion section 4 towards the flame sensor 5B, as well as the light of flames during normal combustion. The flame sensor 5B is a directional type in which an ultraviolet detection section 50 is provided on a part of the upper surface, and it detects only ultraviolet rays that are traveling downwards from above.

[0040] In this embodiment, the holder portion 64 of the shielding portion 6B can be used to prevent the flame sensor 5B from being exposed to the flashback flame, and the flame light (ultraviolet rays) from normal combustion in the combustion section 4 from being detected by the flame sensor 5B, while still allowing for the proper detection of the flashback flame that has progressed to the second region S2. Because the flame sensor 5B has directionality for detecting ultraviolet rays, even if the flame light from normal combustion in the combustion section 4 reaches the flame sensor 5B by being reflected by various parts within the first case 1, it is possible to prevent this light from being detected. In the embodiment shown in Figure 3, it is possible to use a flame sensor that does not have directional detection. Furthermore, the holder portion 64 can be in the form of a case that encloses the flame sensor 5B.

[0041] The present invention is not limited to the embodiments described above. The specific configurations of each part of the combustion device and hot water device according to the present invention can be modified in various ways within the scope intended by the present invention.

[0042] The shielding portion in this invention is essentially just a configuration that can prevent the flame from flashing back from the combustion section to the flame sensor, as well as the light from the flame during normal combustion. The specific shape, size, material, position, number, etc., can be changed in various ways. The flame sensor is not limited to ultraviolet sensors. It may also be a type that detects visible light or infrared light emitted from a flashback flame individually or in combination, in addition to ultraviolet light. In short, any sensor that can optically detect a flashback flame is acceptable. The type of fuel gas is not limited. The combustion device according to the present invention is not limited to hot water systems, but can also be used for other purposes such as heating or incineration. Furthermore, it is not limited to downward combustion types, but can also be upward combustion types, or horizontal combustion types as described in Patent Document 1. [Explanation of symbols]

[0043] C, Ca, Cb Combustion Equipment WH, WHaWHb Hot water system S1, S2 First and second regions (of the mixed gas supply path) 3. Mixed gas supply path 4. Combustion section 5.5B Flame Sensor 6,6A,6B Shield part 60 Partition wall section 63 Cover component

Claims

1. A combustion section for burning fuel gas, This combustion section includes a mixed gas supply passage for supplying a mixed gas of the fuel gas and air, A flame sensor is provided in an arrangement that is located in or facing the mixed gas supply passage, and is capable of optically detecting the flashback flame when flashback occurs from the combustion section to the mixed gas supply passage. A combustion device equipped with, A combustion device further comprising a shielding portion that prevents the flashback flame from reaching the flame sensor from the combustion portion, and prevents the light of the flame during normal combustion from traveling from the combustion portion to the flame sensor.

2. A combustion apparatus according to claim 1, The combustion apparatus includes a partition wall that separates the combustion section from the flame sensor.

3. A combustion apparatus according to claim 1 or 2, The shielding portion includes a cover member that surrounds the flame sensor and partially has an opening that faces upstream in the direction of the mixed gas flow of the mixed gas supply passage. A combustion device configured such that when the flashback flame travels through the mixed gas supply passage to a region facing the opening, the light from this flame is detected by the flame sensor.

4. A combustion apparatus according to claim 1 or 2, A combustion device in which the flame sensor is located in an area outside the combustion section that does not overlap the combustion section in the vertical direction.

5. A hot water device characterized by comprising a combustion device according to any one of claims 1 to 4.

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