Combustion device and hot water device equipped with the same

Abstract

To provide a combustion device capable of suitably preventing the risk of backfire in extinction under a condition that hydrogen or hydrogen-containing gas is being used as fuel gas.SOLUTION: A combustion device C comprises: a burner 2 into which hydrogen or hydrogen-containing gas is to be supplied as fuel gas, and which is provided with a main burner port 21a and flame holding ports 21b, 21b' disposed adjacent to each other; a fan 3; and fuel gas valves Va, Vb. The fuel gas valves Va, Vb can individually stop the supply of the fuel gas to each of the main burner port 21a and the flame holding ports 21b, 21b'. Upon extinguishing the combustion under a condition that the fan 3 is being driven and the fuel gas is burned by the burner 2, the supply of the fuel gas to the main burner port 21a is stopped first, while continuing driving the fan 3, and subsequently the supply of the fuel gas to the flame holding ports 21b, 21b' is stopped after a specified time Ta passes.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 combustion device. [Background technology]

[0002] A specific example of a combustion device is described in Patent Document 1. The combustion device described in this document is equipped with multiple flat burners and a fan that supplies combustion air to the burners. Each burner is a type that has a main flame hole and flame holding holes located on both sides as flame holes that burn a mixture of fuel gas and air (primary air). The main flame hole is a part that burns a lean mixture with an air ratio greater than 1, generating a lean flame as the main flame and causing lean combustion. For this reason, X On the other hand, the flame stabilizing holes are the parts that burn a rich mixture with an air-fuel ratio less than 1, and generate rich flames that act as stabilizing flames on both sides of the main flame. This makes it possible to stabilize the main flame, and ultimately the entire flame.

[0003] However, the above-mentioned combustion apparatus has the following problems to be solved.

[0004] In recent years, measures to realize a low-carbon society have been promoted from the perspective of protecting the natural environment. To achieve this, the use of hydrogen as a fuel gas is being considered in the field of combustion equipment technology. However, hydrogen has a significantly faster combustion speed than city gas (main component: methane CH4) and LP gas (main component: propane C3H8), which are commonly used as fuel gases (Figure 12 shows the combustion speeds of these gases). For this reason, there is a high risk of flashback when hydrogen is used as a fuel gas.

[0005] More specifically, in the burner described above, a flame is formed in the flame holes (main flame holes, flame holding holes), but strictly speaking, the position where the flame is formed is the position where the flow rate of the fuel gas ejected from the innermost part of the flame hole to the outside of the flame hole and the flame propagation rate (burning rate) propagating to the innermost part of the flame hole are balanced. Here, when hydrogen is used as the fuel gas and is burned in the burner, when the supply of hydrogen to the burner is stopped to terminate the combustion (to extinguish the flame), there is a high risk of a flame penetrating from the flame hole to the innermost part (flashback) due to the high burning rate of hydrogen. The flame is a rich flame, and the concentration of fuel gas is higher and the burning rate is faster on the flame holding hole side than on the main flame hole side, so the flashback is likely to occur at the position of the flame holding holes.

[0006] The flashback described above can cause accidents such as equipment damage, so it is desirable to prevent it appropriately. Furthermore, the flashback described above may occur not only when the fuel gas is hydrogen (100% hydrogen (H2)), but also when the fuel gas contains hydrogen (H2).

[0007] Incidentally, one example of a conventional flashback prevention means is the means described in Patent Document 2. In this means, instead of a mixture of hydrogen and air, only hydrogen or only fuel containing hydrogen is supplied to the flame stabilizing holes and this is subjected to diffusion combustion in an attempt to prevent flashback. However, even with such measures, it is difficult to completely prevent flashbacks during extinguishing. This is because, during extinguishing, fuel gas remaining inside the burner diffuses toward the flame stabilizing hole and mixes with air, which can cause flashbacks. Also, hydrogen has the property that its combustion speed increases when it is mixed with air during extinguishing (in Figure 12, when the excess air ratio of hydrogen (H2) changes from P1 to P2, as shown by the arrow Na in the figure, for example, the combustion speed increases, making it more likely to cause flashbacks). (It becomes more difficult.) [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-195516 [Patent Document 2] Japanese Patent Application Publication No. 2019-215127 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention was conceived under the circumstances described above, and its object is to provide a combustion device that can appropriately prevent the risk of backfire during fire extinguishing when hydrogen or a hydrogen-containing gas is used as the fuel gas, and a hot water device equipped with the same. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides the following technical solutions.

[0011] A combustion apparatus provided by a first aspect of the present invention is a combustion apparatus comprising: a burner into which hydrogen or a hydrogen-containing gas is supplied as fuel gas, and which has main flame holes and flame holding holes arranged adjacent to each other as flame holes for burning the fuel gas; a fan for supplying air to the burner; and a fuel gas valve capable of switching between supplying the fuel gas to the burner and stopping it, wherein the fuel gas valve is configured to be able to individually stop the supply of the fuel gas to each of the main flame hole and the flame holding holes, and when the fan is driven and the fuel gas is burning in the burner, the supply of the fuel gas to the main flame hole is first stopped while the fan continues to be driven, and then the supply of the fuel gas to the flame holding holes is stopped after a predetermined time has elapsed. The predetermined time is configured to be longer when the temperature of the burner is relatively high when the combustion is extinguished than when the temperature is relatively low. It is characterized by the presence of

[0012] This configuration provides the following effects. That is, when fuel gas is being burned using a burner and the combustion is to be extinguished, the supply of fuel gas to the main flame hole and the flame holding hole is not stopped simultaneously. Instead, the supply of fuel gas to the main flame hole is stopped first, the main flame is extinguished, and then, after a predetermined time has elapsed, the supply of fuel gas to the flame holding hole is stopped. Therefore, during the predetermined time period, the burner can be actively cooled by supplying air from the fan. As described in the Background Art section, flashback is likely to occur in the flame holding hole of the main flame hole and the flame holding hole during extinguishing. However, when the flame is extinguished in the flame holding hole, the burner is cooled and its temperature drops. On the other hand, flashback is less likely to occur the lower the burner temperature. Therefore, according to the present invention, even when hydrogen or a hydrogen-containing fuel gas, which is prone to flashback, is used as the fuel gas, flashback can be appropriately prevented during extinguishing, and accidents caused by flashback can be effectively prevented.

[0014] moreover With this configuration, if the burner temperature is high when extinguishing the flame, the time required for the burner to be cooled by the air supply from the fan is extended, allowing the burner temperature to be sufficiently reduced. This is therefore more preferable in terms of reliably preventing flashback. On the other hand, if the burner temperature is not so high, the time required for the burner to be cooled by the air supply from the fan is shortened, preventing the timing for stopping the supply of fuel gas to the flame stabilizing holes from being excessively delayed and preventing the time required for extinguishing the flame from being unnecessarily long.

[0015] A combustion apparatus provided according to a second aspect of the present invention comprises a burner into which hydrogen or a hydrogen-containing gas is supplied as a fuel gas, and which has main flame holes and flame holding holes arranged adjacent to each other as flame holes for burning the fuel gas, a fan for supplying air to the burner, and a fuel gas valve capable of switching between starting and stopping the supply of the fuel gas to the burner, wherein the fuel gas valve is configured to be able to individually stop the supply of the fuel gas to each of the main flame hole and the flame holding hole, and when the fan is driven and the fuel gas is burning in the burner, the fuel gas supply to the main flame hole is first stopped while the fan continues to be driven, and then the supply of the fuel gas to the flame holding hole is stopped after a predetermined time has elapsed, The predetermined time is set to be longer when the burner is driven and combusting for a relatively long time than when the burner is driven and combusting for a relatively short time, and / or is set to be longer when the output of the burner is driven and combusting for a relatively low time than when the output of the burner is relatively high. It is characterized by the following.

[0016] This configuration provides the following effects. That is, if the burner's driving combustion time is long, the burner is likely to reach a high temperature. Also, if the output of the burner's driving combustion is low, the flame is located close to the burner, and the burner is also likely to reach a high temperature in this case. On the other hand, when the burner is likely to reach a high temperature in this way, the predetermined time is set to be longer than when it is not. Therefore, the same effect as that described for the configuration in which the predetermined time is set to be longer when the burner temperature is high when extinguishing combustion than when it is low can be obtained, which is more preferable in terms of reliably preventing flashback and also makes it possible to prevent the time required to extinguish the flame from being unnecessarily long.

[0017] A combustion apparatus provided according to a third aspect of the present invention comprises a burner into which hydrogen or a hydrogen-containing gas is supplied as a fuel gas, and which has main flame holes and flame holding holes arranged adjacent to each other as flame holes for burning the fuel gas, a fan for supplying air to the burner, and a fuel gas valve capable of switching between starting and stopping the supply of the fuel gas to the burner, wherein the fuel gas valve is configured to be able to individually stop the supply of the fuel gas to each of the main flame hole and the flame holding holes, and when the fan is driven and the fuel gas is burning in the burner, the fuel gas supply to the main flame hole is first stopped while the fan continues to be driven, and then the supply of the fuel gas to the flame holding holes is stopped after a predetermined time has elapsed, The predetermined time is configured to be longer when the temperature of the location where the combustion device is installed is relatively high than when the temperature is relatively low. It is characterized by the following.

[0018] This configuration provides the following effects. In other words, if the temperature at the location where the combustion device is installed is high, it is difficult to lower the burner temperature by supplying air using a fan during extinguishing, and in order to sufficiently lower the burner temperature, it is necessary to take a longer air supply time. With the above configuration, it is possible to appropriately deal with such situations, and when the temperature is high, the air supply time to the burner is taken longer, making it possible to reliably prevent flashback, while when the temperature is low, it is possible to prevent the time required to extinguish the flame from becoming unnecessarily long.

[0019] A fourth aspect of the present invention provides a combustion apparatus comprising: a burner into which hydrogen or a hydrogen-containing gas is supplied as a fuel gas, and which has main flame holes and flame holding holes arranged adjacent to each other as flame holes for burning the fuel gas; a fan for supplying air to the burner; and a fuel gas valve capable of switching between starting and stopping the supply of the fuel gas to the burner, wherein the fuel gas valve is configured to be able to individually stop the supply of the fuel gas to each of the main flame hole and the flame holding holes, and when the fan is driven and the fuel gas is burning in the burner, the fuel gas supply to the main flame hole is first stopped while the fan continues to be driven, and then the supply of the fuel gas to the flame holding holes is stopped after a predetermined time has elapsed, The system further includes an exhaust blockage determining means for determining when an exhaust blockage has occurred, and the predetermined time is set to be longer when the exhaust blockage determining means determines that an exhaust blockage has occurred than when the exhaust blockage has not occurred. It is characterized by the following.

[0020] This configuration provides the following effects. That is, when exhaust blockage occurs, the pressure around the burner installation location rises, causing a decrease in so-called gas input. This reduces the flame height and makes it easier for the burner surface temperature to rise. In this case, with the above configuration, the predetermined time is extended, making it possible to appropriately cool the burner with air supplied from the fan and accurately prevent flashback. When exhaust blockage does not occur, the predetermined time is shortened, preventing the time required to extinguish the flame from becoming unnecessarily long.

[0021] A fifth aspect of the present invention provides a combustion apparatus comprising: a burner into which hydrogen or a hydrogen-containing gas is supplied as a fuel gas, and which has main flame holes and flame holding holes arranged adjacent to each other as flame holes for burning the fuel gas; a fan for supplying air to the burner; and a fuel gas valve capable of switching between starting and stopping the supply of the fuel gas to the burner, wherein the fuel gas valve is configured to be able to individually stop the supply of the fuel gas to each of the main flame hole and the flame holding holes, and when the fan is driven and the fuel gas is burning in the burner, the fuel gas supply to the main flame hole is first stopped while the fan continues to be driven, and then the supply of the fuel gas to the flame holding holes is stopped after a predetermined time has elapsed, The flame stabilizing holes are configured to be supplied with a mixture of the fuel gas and air, and the driving speed of the fan is kept constant from the time when the supply of fuel gas to the main flame hole is stopped until the supply of fuel gas to the flame stabilizing holes is stopped, and is configured to increase after the supply of fuel gas to the flame stabilizing holes is stopped. It is characterized by the following.

[0022] This configuration provides the following effects. That is, when a mixture is supplied to the flame stabilizing hole and combustion is occurring, if a large amount of air is supplied before the fire is extinguished, flashback is likely to occur. On the other hand, with the above-mentioned configuration, such a situation is appropriately avoided and flashback is prevented. In addition, the supply of fuel gas (combustion) to the flame stabilizing hole is Since the fan driving speed is increased after the supply of the fuel gas and air mixture is stopped, the remaining mixture in the burner can be quickly discharged to the outside of the burner through the flame stabilizing holes.

[0023] A combustion apparatus according to a sixth aspect of the present invention is a combustion apparatus comprising: a burner into which hydrogen or a hydrogen-containing gas is supplied as a fuel gas, and which has main flame holes and flame holding holes arranged adjacent to each other as flame holes for burning the fuel gas; a fan for supplying air to the burner; and a fuel gas valve capable of switching between starting and stopping the supply of the fuel gas to the burner, wherein the fuel gas valve is configured to be able to individually stop the supply of the fuel gas to each of the main flame hole and the flame holding holes, and when the fan is driven and the fuel gas is burning in the burner, the fuel gas supply to the main flame hole is first stopped while the fan continues to be driven, and then the supply of the fuel gas to the flame holding holes is stopped after a predetermined time has elapsed, The fuel gas is supplied to the flame stabilizing holes in a state where it is not mixed with air, and the driving speed of the fan is increased after the supply of fuel gas to the main flame hole is stopped and before the supply of fuel gas to the flame stabilizing holes is stopped. It is characterized by the following.

[0024] This configuration provides the following effects. In other words, in order to appropriately prevent flashback, it is desirable to cool the burner as early as possible, and the above-mentioned configuration can appropriately respond to such a situation. With the above-mentioned configuration, although the fan driving speed is increased until the supply of fuel gas to the flame holding holes is stopped, air is not supplied to the flame holding holes, so there is no problem even if the fan driving speed is increased while flame holding is being formed in the flame holding holes.

[0025] The present invention 7 The water heating device provided by this aspect of the present invention Any of 1 to 6 The present invention is characterized by comprising a combustion device provided by the above aspect.

[0026] According to this configuration, Any of 1 to 6 The same effects as those described for the combustion device provided by the above aspect can be obtained.

[0029] Other features and advantages of the present invention will become more apparent from the following description of the preferred embodiments of the invention, which proceeds with reference to the accompanying drawings. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a schematic cross-sectional view of a main part showing an example of a combustion device according to the present invention. [Figure 2] FIG. 2 is a schematic perspective view of a burner case that houses a plurality of burners of the combustion device shown in FIG. [Figure 3] FIG. 3 is a schematic cross-sectional view taken along line III-III of FIG. 2. [Figure 4] FIG. 2 is a perspective view of a burner used in the combustion device shown in FIG. [Figure 5] 5(a) is a partially cutaway side view of the burner shown in FIG. 4, and FIG. 5(b) is an enlarged cross-sectional view of a main part of FIG. [Figure 6] 2 is a flowchart showing an example of an operational processing procedure executed in the combustion apparatus shown in FIG. [Figure 7]7(a) to 7(c) are time charts showing a part of the operation processing procedure shown in the flowchart of FIG. [Figure 8] FIG. 4 is a schematic cross-sectional view of a main part showing another example of a combustion device according to the present invention. [Figure 9] 9(a) to 9(c) are time charts showing a part of the operational processing procedure executed in the combustion device shown in FIG. [Figure 10] 1 is a schematic explanatory diagram showing an example of a hot water device according to the present invention. [Figure 11] FIG. 10 is a schematic explanatory diagram showing another example of a hot water device according to the present invention. [Figure 12] FIG. 2 is a diagram showing the relationship between the excess air ratio and the combustion speed for a plurality of types of fuel gas used in the combustion device. DETAILED DESCRIPTION OF THE INVENTION

[0031] Preferred embodiments of the present invention will now be described in detail with reference to the drawings.

[0032] The combustion device C shown in FIG. 1 is used as a component of the water heating devices WH and WHa described later, and includes a burner case 1, a plurality of burners 2 housed inside the burner case 1, a fan 3, a fuel gas supply head 4 that supplies fuel gas to the plurality of burners 2, and a control unit 5.

[0033] The burner case 1 is, for example, a roughly rectangular parallelepiped case with an open top. As shown in Figures 2 and 3, a plurality of burners 2 are arranged and housed inside the burner case 1. As shown in Figure 1, a heat exchanger 6 is mounted on the upper side of the burner case 1, and this heat exchanger 6 recovers heat from the combustion gas generated by the plurality of burners 2 to heat water.

[0034] Each burner 2 is made of metal and has a flat overall shape, with fuel gas inlets 20a, 20b for the main flame and flame stabilization provided on the side of one longitudinal end (see also Figure 4). A plurality of flame holes for burning fuel gas are opened on the upper surface of each burner 2. As clearly shown in Figure 5, these flame holes include a flame stabilization hole 21b located in the center of each burner 2 in the short direction, a pair of main flame holes 21a adjacent to it on both outside sides, and a further pair of flame stabilization holes 21b' adjacent to those on both outside sides.

[0035] Each burner 2 is a so-called lean / rich burner, and hydrogen is supplied as fuel gas from the fuel gas supply head 4. The main flame hole 21a is the area where a lean mixture with an air ratio greater than 1 burns, generating a lean flame as the main flame. The flame holding holes 21b, 21b' are the areas where a rich mixture with an air ratio less than 1 burns, generating a rich flame as flame holding. The flame holding serves to stabilize the main flame. An ignition plug 90 and a flame detection sensor 91 are provided above the burner 2.

[0036] The fuel gas supply head 4 is equipped with a plurality of gas ejection nozzles 40a, 40b that eject hydrogen as fuel gas into the fuel gas inlets 20a, 20b for the main flame and flame holding of each burner 2. Meanwhile, the fan 3 is attached to the burner case 1 and is capable of supplying combustion air into this burner case 1. When fuel gas is ejected from the gas ejection nozzles 40a, 40b into the fuel gas inlets 20a, 20b, primary air is introduced into the fuel gas inlets 20a, 20b together with this fuel gas. The mixture of fuel gas and primary air reaches the main flame hole 21a and flame holding holes 21b, 21b' via internal gas flow paths 22a, 22b formed in the burner 2. However, the fuel gas inlet 20a for the main flame is not supplied to the flame holding holes 21b, 21b'. The opening area of ​​the fuel gas inlet 20b is larger than that of the fuel gas inlet 20a for the main flame hole 21a, and the fuel gas mixture that reaches the flame stabilizing holes 21b has a smaller excess air ratio than the fuel gas mixture that reaches the main flame hole 21a.

[0037] Each burner 2 is placed on a straightening plate 18 provided with a plurality of vent holes 19. Of the air supplied from the fan 3 into the burner case 1, a portion is used as the primary air described above, while another portion passes through the plurality of vent holes 19 and is supplied to the installation location of the burner 2, where it is used as secondary air for combustion. However, the air supplied from the fan 3 also serves to cool the burner 2, as will be described later.

[0038] The fuel gas supply head 4 is equipped with main flame and flame-holding fuel gas valves Va and Vb, which can switch between supplying and stopping fuel gas to the burner 2. More specifically, the fuel gas supply head 4 is equipped with main flame and flame-holding fuel gas flow paths 41a and 41b as fuel gas flow paths communicating with the gas ejection nozzles 40a and 40b. The fuel gas valves Va and Vb are, for example, solenoid valves, and are equipped with reciprocating valve bodies 43a and 43b facing openings 42a and 42b of the fuel gas flow paths 41a and 41b. These valve bodies 43a and 43b can independently open and close the openings 42a and 42b. With this configuration, the supply and stopping of fuel gas from each of the gas ejection nozzles 40a and 40b to the burner 2 can be independently switched. In other words, the supply and stopping of fuel gas to the main flame hole 21a and the flame-holding holes 21b and 21b' of the burner 2 can be independently switched. However, when fuel gas is supplied to the burner 2 to start driving combustion of the burner 2, the fuel gas valves Va and Vb are simultaneously switched from the closed state to the open state.

[0039] The control unit 5 is configured using a microcomputer, and is capable of executing operation control and data processing of each unit described below of the combustion device C. The combustion device C is equipped with a temperature sensor Sa for detecting the air temperature at the location where the combustion device C is installed, and a drive current sensor Sb for detecting the drive current of the motor M that drives the fan 3. Detection signals from these sensors are input to the control unit 5.

[0040] Next, an example of operational control of the combustion device C and its action will be described with reference to the flowchart shown in FIG.

[0041] First, when each burner 2 is driven and burning, the fan 3 is in operation, and the main flame and flame-holding fuel gas valves Va, Vb are both open, with hydrogen burning as fuel gas in the main flame hole 21a and flame-holding holes 21b, 21b' of each burner 2. In this state, when the control unit 5 executes a process to extinguish the combustion, it first switches the main flame fuel gas valve Va to a closed state and extinguishes the main flame in the main flame hole 21a (S1: YES, S2: YES, S3).

[0042] In addition, in accordance with the above operation, the control unit 5 starts counting the predetermined time Ta (S4). The predetermined time Ta corresponds to the delay time from when the main flame fuel gas valve Va is switched to the closed state until the flame holding fuel gas valve Vb is switched to the closed state. This predetermined time Ta may be fixed to a certain time, but in this embodiment, it is variable and is determined by the control unit 5 based on predetermined conditions (S5). However, details of this point will be described later.

[0043] When the predetermined time Ta has elapsed since the main flame fuel gas valve Va was switched to the closed state, the flame holding fuel gas valve Vb is switched to the closed state by the control of the control unit 5 at that time (S6: YES, S7). As a result, both the main flame and the flame holding of each burner 2 are extinguished, but during the predetermined time Ta, the main flame is extinguished. The burner 2 can be cooled using air supplied from the fan 3, thereby lowering the temperature of the burner 2. The cooling of the burner 2 is achieved by the action of primary air continuously flowing into the burner 2 from the main flame fuel gas inlet 20a and the action of secondary air coming into contact with the outer surface of the burner 2. In this embodiment, it is possible to lower the temperature of the burner 2 when the flame holding fuel gas valve Vb is switched to the closed state after the predetermined time Ta has elapsed. Normally, flashback is more likely to occur during flame extinguishing than during flame holding, but according to this embodiment, it is possible to prevent flashback from occurring during flame holding extinguishing.

[0044] Following the extinguishing of the flame, the control unit 5 increases the speed of the fan 3 (S8) (see also FIG. 7). This allows the mixture of fuel gas and air remaining in the burner 2 to be quickly discharged to the outside of the burner 2, and also allows the combustion gas present in the combustion device C to be discharged to the outside of the combustion device C. The fan 3 is then stopped after an appropriate predetermined time Tb has elapsed. Unlike the above configuration, if the speed of the fan 3 is increased and a large amount of air is supplied to the flame holding holes 21b before the flame holding holes 21b are extinguished, flashback becomes more likely (for the reasons explained above with reference to FIG. 12). However, according to the above configuration, the speed of the fan 3 is increased after the flame holding holes 21b are extinguished, so flashback does not become more likely to occur.

[0045] In step S5 of the above-described series of operation procedures, the predetermined time Ta is set to a time that satisfies all or some of the following conditions. Condition 1: When the temperature of burner 2 is high, the time is longer than when the temperature is low. Condition 2: When the burner 2 is driven and combusted for a long time, the time is set to be longer than when the burner 2 is driven and combusted for a short time. Condition 3: When the output of the drive combustion of the burner 2 is low, the time is set longer than when it is high. Condition 4: When the air temperature detected by the temperature sensor Sa is high, the time is set longer than when it is low. Condition 5: If the drive current value of the motor M of the fan 3 detected using the drive current sensor Sb exceeds a predetermined threshold and it is determined that an exhaust blockage has occurred, the time is set to be longer than when this is not the case.

[0046] The predetermined time Ta can be a value that changes continuously, or alternatively, can be a value that changes in stages. When the predetermined time Ta is a value that changes in stages, the control unit 5 may select, for example, two stages (long and short), three stages (long, medium, and short), or multiple stages of more than one.

[0047] [Regarding condition 1 above] In the above-mentioned condition 1, whether the temperature of the burner 2 is high may be determined directly or indirectly by measuring the temperature of the burner 2 or the temperature of a portion that reflects the temperature of the burner 2, for example, using a temperature sensor, or may be determined by the control unit 5 based on the status of the burner 2's driving and combustion (the above-mentioned conditions 2 and 3 indirectly determine whether the temperature of the burner 2 is high based on the status of the burner 2's driving and combustion, and can be considered specific embodiments of the above-mentioned condition 1). According to the above-mentioned condition 1, when the temperature of the burner 2 is high, the predetermined time Ta is set longer than when it is low, so that the temperature of the burner 2 can be sufficiently lowered within the predetermined time Ta by the air supply from the fan 3, which is more preferable in terms of reliably preventing flashback. On the other hand, when the temperature of the burner 2 is not so high, the predetermined time Ta is set shorter, so that an unnecessarily long time required for the flame to be extinguished is appropriately avoided.

[0048] [Regarding conditions 2 and 3 above] If the burner 2 is driven and combusted for a long time, the burner 2 is likely to reach a high temperature. Also, if the output (heating power) of the burner 2 is low, the flame is present near the burner 2, so the burner 2 is likely to reach a high temperature in this case as well. According to the above conditions 2 and 3, when the burner 2 is likely to reach a high temperature as described above, the predetermined time Ta is set to be longer than when it is not. As in the case described in point 1, this is more preferable in terms of ensuring sufficient cooling of the burner 2 and reliably preventing flashback, and it is also possible to appropriately avoid an unnecessarily long time being required to extinguish the flame.

[0049] [Regarding condition 4 above] If the temperature at the location where the combustion device C is installed is relatively high, it becomes difficult to quickly lower the temperature of the burner 2 by supplying air from the fan 3, and it is necessary to extend the time for supplying air to sufficiently lower the temperature of the burner 2. According to the condition 4, it is possible to appropriately deal with such a situation, and when the temperature is relatively high, it is possible to extend the time for supplying air to the burner 2, sufficiently lower the temperature of the burner 2, and reliably prevent flashback. On the other hand, when the temperature is relatively low, it is possible to prevent the time required to extinguish the flame from becoming unnecessarily long.

[0050] [Regarding condition 5 above] When exhaust blockage occurs, the pressure around the location where the burner 2 is installed increases, which reduces the so-called gas input and the flame height. As a result, the surface temperature of the burner 2 tends to increase. According to the condition 5, in such a case, the predetermined time Ta is lengthened, and in other cases, the predetermined time Ta is shortened, so that the same effect as in the case of the condition 1 is obtained.

[0051] When an exhaust blockage occurs, the load on the motor M of the fan 3 increases, and the drive current value thereof rises. The control unit 5 determines whether or not an exhaust blockage occurs based on this principle, and the combination of the control unit 5 and the drive current sensor Sb corresponds to an example of the exhaust blockage determination means referred to in the present invention. The presence or absence of an exhaust blockage can be determined based on parameters other than the drive current value of the motor M. For example, when an exhaust blockage occurs, the temperature at a specific location within the combustion device C may abnormally rise, and it is possible to determine whether or not an exhaust blockage occurs by detecting this temperature.

[0052] Fig. 8 shows another embodiment of the combustion device according to the present invention. In this figure, elements that are the same as or similar to those in the previous embodiment are given the same reference numerals as in the previous embodiment, and duplicated explanations will be omitted.

[0053] 8, there is no gap between the flame-stabilizing fuel gas inlet 20b and the corresponding fuel gas ejection nozzle 40b through which air can enter, and only hydrogen as fuel gas is introduced into the flame-stabilizing fuel gas inlet 20b, not air. Therefore, when the burner 2 is driven to burn, a stabilized flame is formed in the flame stabilizing hole 21b, where hydrogen without air is burned in a diffusive manner.

[0054] 9(a) and 9(b), in the combustion apparatus Ca of this embodiment, the fuel gas supply to the flame stabilizing holes 21b, 21b' is stopped when a predetermined time Ta has elapsed since the fuel gas supply to the main flame hole 21a was stopped. However, as shown in FIG. 9(c), the driving speed of the fan 3 is controlled to increase during the period from when the fuel gas supply to the main flame hole 21a is stopped until the fuel gas supply to the flame stabilizing holes 21b, 21b' is stopped.

[0055] To prevent flashback, it is desirable to cool the burner 2 as early as possible, and according to this embodiment, this desire can be met accurately because the speed of the fan 3 is increased before the supply of fuel gas to the flame holding holes 21b, 21b' is stopped. Furthermore, according to this embodiment, air is not supplied to the flame holding holes 21b, 21b', so there is no problem even if the speed of the fan 3 is increased while flame holding is being formed in the flame holding holes 21b, 21b'.

[0056] 10 and 11 show hot water apparatuses WH and WHa as hot water supply apparatuses configured using the combustion apparatus C (or combustion apparatus Ca) and heat exchanger 6 described above.

[0057] The hot water device WH shown in Figure 10 has the same basic overall configuration as a general gas water heater, with an internal water inlet pipe 70 and an internal hot water outlet pipe 71 connected to a heat exchanger 6, and hot water supplied from outside to a water inlet 70a is sent to the heat exchanger 6 via the internal water inlet pipe 70 and heated by combustion gas generated in the combustion device C. This heated hot water reaches a hot water outlet 71a via the internal hot water outlet pipe 71 and is supplied to a desired hot water supply destination from this hot water outlet 71a.

[0058] The hot water device WHa shown in Figure 11 is equipped with a liquid circulation path 8 that uses a pump P to circulate hot water (liquid) through a fixed path including a heat exchanger 6 (corresponding to the first heat exchanger in this invention), and a heat exchanger 9 (corresponding to the second heat exchanger in this invention). An internal water inlet pipe 70 and an internal hot water outlet pipe 71 are connected to the heat exchanger 9, which is capable of heating hot water supplied from the outside to a water inlet port 70a using the heat of the hot water in the liquid circulation path 8 and discharging the hot water from an outlet port 71a via the internal hot water outlet pipe 71 to the outside. A flow rate sensor Sc is provided in the internal water inlet pipe 71, which is capable of detecting when water inflow exceeds a predetermined flow rate.

[0059] The water heating apparatus WHa of this embodiment is not only capable of supplying hot water similar to the water heating apparatus WH shown in Fig. 10, but also has a function that, unlike the water heating apparatus WH, appropriately prevents the hot water in the heat exchanger 6 from boiling when the operation of the combustion apparatus C is stopped. That is, as described above, when the combustion apparatus C is extinguished, the main flame and the flame holding are extinguished sequentially with a time difference of a predetermined time Ta. Therefore, in the water heating apparatus WH shown in Fig. 10, even if the water inlet 70a is stopped and the burner 2 is stopped from burning, the burner 2 continues to burn for the predetermined time Ta, and therefore the hot water remaining stationary in the heat exchanger 6 is heated during that period, and there is a risk of it boiling.

[0060] In contrast, in the hot water system WHa, even if the water supply to the water inlet 70a is stopped, the pump P can be kept running thereafter, and the hot water can be circulated in the liquid circulation path 8 until the burner 2 has completely finished driving combustion. This makes it possible to prevent the hot water in the heat exchanger 6 from boiling.

[0061] The present invention is not limited to the above-described embodiment, and the specific configurations of the combustion device and the hot water device according to the present invention can be freely designed and modified in various ways within the intended scope of the present invention.

[0062] In the above-described embodiment, the burner 2 is configured to have a main flame hole 21a and flame holding holes 21b, 21b', but the specific number of main flame holes and flame holding holes is not limited, and it may be configured, for example, to have only a pair of flame holding holes on either side of one main flame hole. The fuel gas may be a hydrogen-containing gas instead of hydrogen. [Explanation of symbols]

[0063] C. Combustion device WH,WHa Water heating device Va, Vb fuel gas valve Sb Drive current sensor (exhaust blockage determination means) 2 Burner 21a Main flame hole 21b,21b' Flame holding hole 3 Fans 4 Fuel gas supply head 5. Control unit (exhaust blockage determination means) 6 Heat exchanger (first heat exchanger) 8 Liquid circulation path 9 Heat exchanger (second heat exchanger)

Claims

1. a burner into which hydrogen or a hydrogen-containing gas is supplied as a fuel gas, and which has a main flame hole and a flame holding hole arranged adjacent to each other as flame holes for burning the fuel gas; a fan that supplies air to the burner; a fuel gas valve capable of switching between supplying and stopping the fuel gas to the burner; A combustion device comprising: the fuel gas valve is configured to be able to individually stop the supply of the fuel gas to the main flame hole and the flame holding hole, When the fan is driven and the fuel gas is burning in the burner, in order to extinguish the combustion, the supply of the fuel gas to the main flame hole is first stopped while the fan is still driven, and then, after a predetermined time has elapsed, the supply of the fuel gas to the flame stabilizing hole is stopped, A combustion device characterized in that the predetermined time is configured to be longer when the temperature of the burner when the combustion is extinguished is relatively high than when it is relatively low.

2. A burner into which hydrogen or a hydrogen-containing gas is supplied as a fuel gas, and which has a main flame hole and a flame holding hole arranged adjacent to each other as flame holes for burning the fuel gas; a fan that supplies air to the burner; a fuel gas valve capable of switching between supplying and stopping the fuel gas to the burner; A combustion device comprising: the fuel gas valve is configured to be able to individually stop the supply of the fuel gas to the main flame hole and the flame holding hole, When the fan is driven and the fuel gas is burning in the burner, in order to extinguish the combustion, the supply of the fuel gas to the main flame hole is first stopped while the fan is still driven, and then, after a predetermined time has elapsed, the supply of the fuel gas to the flame stabilizing hole is stopped, A combustion device characterized in that the predetermined time is set to be longer when the burner driving combustion time is relatively long than when it is relatively short, and / or is set to be longer when the output of the burner driving combustion is relatively low than when it is relatively high.

3. A burner into which hydrogen or a hydrogen-containing gas is supplied as a fuel gas, and which has a main flame hole and a flame holding hole arranged adjacent to each other as flame holes for burning the fuel gas; a fan that supplies air to the burner; a fuel gas valve capable of switching between supplying and stopping the fuel gas to the burner; A combustion device comprising: the fuel gas valve is configured to be able to individually stop the supply of the fuel gas to the main flame hole and the flame holding hole, When the fan is driven and the fuel gas is burning in the burner, in order to extinguish the combustion, the supply of the fuel gas to the main flame hole is first stopped while the fan is still driven, and then, after a predetermined time has elapsed, the supply of the fuel gas to the flame stabilizing hole is stopped, A combustion device characterized in that the predetermined time is configured to be longer when the temperature of the location where the combustion device is installed is relatively high than when the temperature is relatively low.

4. A burner into which hydrogen or a hydrogen-containing gas is supplied as a fuel gas, and which has a main flame hole and a flame holding hole arranged adjacent to each other as flame holes for burning the fuel gas; a fan that supplies air to the burner; a fuel gas valve capable of switching between supplying and stopping the fuel gas to the burner; A combustion device comprising: the fuel gas valve is configured to be able to individually stop the supply of the fuel gas to the main flame hole and the flame holding hole, When the fan is driven and the fuel gas is burning in the burner, in order to extinguish the combustion, the supply of the fuel gas to the main flame hole is first stopped while the fan is still driven, and then, after a predetermined time has elapsed, the supply of the fuel gas to the flame stabilizing hole is stopped, The device further includes an exhaust blockage determining means for determining when an exhaust blockage has occurred, A combustion device characterized in that the predetermined time is configured to be longer when the exhaust blockage determination means determines that exhaust blockage has occurred than when it does not.

5. A burner into which hydrogen or a hydrogen-containing gas is supplied as a fuel gas, and which has a main flame hole and a flame holding hole arranged adjacent to each other as flame holes for burning the fuel gas; a fan that supplies air to the burner; a fuel gas valve capable of switching between supplying and stopping the fuel gas to the burner; A combustion device comprising: the fuel gas valve is configured to be able to individually stop the supply of the fuel gas to the main flame hole and the flame holding hole, When the fan is driven and the fuel gas is burning in the burner, in order to extinguish the combustion, the supply of the fuel gas to the main flame hole is first stopped while the fan is still driven, and then, after a predetermined time has elapsed, the supply of the fuel gas to the flame stabilizing hole is stopped, A mixture of the fuel gas and air is supplied to the flame holding hole, A combustion device characterized in that the driving speed of the fan is kept constant during the period from when the supply of fuel gas to the main flame hole is stopped to when the supply of fuel gas to the flame stabilizing hole is stopped, and is configured to increase after the supply of fuel gas to the flame stabilizing hole is stopped.

6. A burner into which hydrogen or a hydrogen-containing gas is supplied as a fuel gas, and which has a main flame hole and a flame holding hole arranged adjacent to each other as flame holes for burning the fuel gas; a fan that supplies air to the burner; a fuel gas valve capable of switching between supplying and stopping the fuel gas to the burner; A combustion device comprising: the fuel gas valve is configured to be able to individually stop the supply of the fuel gas to the main flame hole and the flame holding hole, When the fan is driven and the fuel gas is burning in the burner, in order to extinguish the combustion, the supply of the fuel gas to the main flame hole is first stopped while the fan is still driven, and then, after a predetermined time has elapsed, the supply of the fuel gas to the flame stabilizing hole is stopped, The fuel gas is supplied to the flame stabilizing hole in a state where it is not mixed with air, a combustion device characterized in that the driving speed of the fan is configured to increase after the supply of fuel gas to the main flame hole is stopped and before the supply of fuel gas to the flame holding hole is stopped.

7. A water heating system comprising the combustion device according to any one of claims 1 to 6.

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