JP7529487B2 - Combustion equipment - Google Patents

Description

The present invention relates to a combustion device that includes a burner disposed in a combustion chamber for burning a mixture of combustion air and fuel gas, a fan for supplying combustion air to the burner via an air supply passage, a gas supply passage for supplying fuel gas to the burner, a proportional valve provided in the gas supply passage, ignition means for performing an ignition operation to ignite the burner, ignition detection means for detecting ignition of the burner, a controller for controlling the fan, the proportional valve, and the ignition means, and an exhaust passage for exhausting combustion gas generated by combustion in the burner from the combustion chamber to the outside.

Conventionally, there is known a type of combustion device in which, when the burner is instructed to burn a mixed gas for the first time after the combustion device is installed, a trial operation mode is set in the controller to vent a large amount of air present in the gas supply passage to the outside of the combustion chamber by supplying fuel gas (see, for example, Patent Document 1).

In the test run mode, the controller opens the proportional valve to a specified opening, replaces the air in the gas supply passage with fuel gas, and causes the ignition means to repeatedly perform ignition operations until the air-fuel ratio of the mixed gas supplied to the burner reaches or exceeds the lower explosion limit, thereby igniting the burner. Note that the lower explosion limits for methane and propane are 5.0 vol.% and 2.1 vol.%, respectively.

Japanese Patent Application Publication No. 5-133522

In the combustion device described in Patent Document 1, the opening of the proportional valve in the test operation mode is set in the controller to be the same as that during ignition in the normal combustion mode, in which the mixed gas is stably burned in the burner. However, even when the air-fuel ratio of the mixed gas supplied to the burner is equal to or higher than the lower explosion limit, the burner may not ignite due to accidental factors such as a spark failure of the ignition electrode. In this case, a large amount of mixed gas remains in the combustion chamber, and if the ignition means is made to perform an ignition operation again in this state to ignite the burner, there is a risk of explosive ignition.

In view of the above, the present invention aims to provide a combustion device with improved safety that can suppress the occurrence of explosive adhesion in the burner while the test operation mode is being executed.

In order to solve the above problems, the present invention provides a combustion device including a burner arranged in a combustion chamber for burning a mixed gas of combustion air and fuel gas, a fan for supplying the combustion air to the burner through an air supply passage, a gas supply passage for supplying the fuel gas to the burner, a proportional valve provided in the gas supply passage, ignition means for performing an ignition operation for igniting the burner, ignition detection means for detecting ignition of the burner, a controller for controlling the fan, the proportional valve and the ignition means, and an exhaust passage for exhausting combustion gas generated by combustion in the burner from the combustion chamber to the outside, the device comprising: The controller is characterized by being capable of executing two modes: a normal combustion mode in which the proportional valve aperture and the fan speed are controlled so that the air-fuel ratio of the mixed gas becomes a value suitable for igniting the burner, and the ignition means is caused to perform an ignition operation to ignite the burner, and a trial operation mode in which at least one of the proportional valve aperture and the fan speed is controlled so that the air-fuel ratio of the mixed gas becomes a value below the lower explosion limit and therefore cannot be ignited, and a purge operation is performed to exhaust the mixed gas supplied to the burner from the combustion chamber to the outside through an exhaust path for a predetermined period of time.

According to the present invention, the air in the gas supply passage is replaced with fuel gas by the purging operation performed in the test operation mode, but since the air-fuel ratio of the mixed gas supplied to the burner is below the lower explosion limit, it is possible to suppress the occurrence of explosive adhesion in the burner while the test operation mode is being performed. Therefore, safety during the purging operation is improved.

In the present invention, the combustion device includes an intake and exhaust section state detection means for detecting the state of the intake and exhaust section from the intake and exhaust passage through the combustion chamber to the exhaust passage, and the controller, in the test operation mode, desirably causes the intake and exhaust section state detection means to detect the state of the intake and exhaust section prior to the purging operation, and if there is an abnormality in the state of the intake and exhaust section, does not execute the purging operation, and executes the purging operation if the state of the intake and exhaust section is normal. According to this, in the test operation mode, the controller determines whether there is an abnormality in the state of the intake and exhaust section due to a blockage or the like, or whether the state of the intake and exhaust section is normal, prior to the purging operation, so that it is possible to suppress a decrease in the amount of air in the mixed gas caused by an abnormality in the state of the intake and exhaust section, and an increase in the air-fuel ratio of the mixed gas caused by a short circuit in which the mixed gas that should have been exhausted flows back into the exhaust passage. Therefore, it is possible to suppress the supply of mixed gas above the lower explosion limit to the burner during the purging operation, and the safety of the purging operation is further improved.

In addition, in the present invention, it is preferable that the controller transitions to the trial operation mode when the ignition detection means does not detect ignition of the burner even if the ignition means repeats the ignition operation a predetermined number of times while the normal combustion mode is being executed. According to this, even in the normal combustion mode, if the amount of air in the mixed gas supplied to the burner is excessive and not suitable for ignition in the burner, the mode automatically transitions to the trial operation mode, which eliminates the need for a user or installer to switch to the trial operation mode, improving convenience.

1 is a schematic diagram showing a hot water heat source machine which is one embodiment of a combustion device of the present invention; 4 is a flowchart showing one embodiment of control performed by a controller of the hot water heat source machine shown in FIG. 1 .

With reference to FIG. 1, an outline of a hot water supply heat source device 1a which is an embodiment of the combustion device 1 of the present invention will be described. The hot water supply heat source device 1a has a combustion chamber 2a surrounded by a combustion case 2. A burner 3 is disposed in the lower part of the combustion chamber 2a, and the burner 3 has a first part ₃₁ in which five unit burners 3a are arranged side by side, and a second part ₃₂ in which ten unit burners 3a are arranged side by side. In addition, an ignition electrode 31 facing the first part ₃₁ of the burner 3 is provided in the combustion chamber 2a, and an igniter 32 which is a source of high voltage application to the ignition electrode 31 and serves as an ignition means is provided. The igniter 32 performs an ignition operation by energization, and ignites the first part 31 by sparking the ignition electrode _31. Furthermore, a flame rod 33 is provided in the combustion chamber 2a as an ignition detection means for detecting the ignition of the burner 3.

A heat exchanger 4 for hot water supply is disposed at the top of the combustion chamber 2a as an object to be heated. A fan 5 is connected to the bottom of the combustion case 2, which supplies combustion air to the burner 3 through an air supply passage 5a. The combustion air supplied by the fan 5 consists of primary air supplied directly to the unit burner 3a and secondary air supplied to the vicinity of the flame port of the unit burner 3a through the bottom of the combustion chamber 2a. Water from the water supply pipe 4a on the upstream side of the heat exchanger 4 is heated by the combustion gas from the burner 3, and hot water heated to a predetermined set temperature is discharged from the hot water outlet pipe 4b on the downstream side of the heat exchanger 4. The combustion gas that has passed through the heat exchanger 4 is exhausted to the outside of the combustion chamber 2a through an exhaust passage 6 connected to the top of the combustion case 2. An intake and exhaust section A is formed, which runs from the air supply passage 5a through the combustion chamber 2a to the exhaust passage 6. The state inside the intake and exhaust section A is detected by an intake and exhaust section state detection means _A1 . The supply/exhaust section state detection means _A1 detects whether the state within the supply/exhaust section A is normal with no impediment to combustion in the burner 3, or whether there is an abnormality such as a blockage occurring somewhere within the supply/exhaust section A that may impede combustion in the burner 3. Specifically, the supply/exhaust section state detection means _A1 detects the fan current of the fan 5, and detects whether the state within the supply/exhaust section A is normal or abnormal.

A main valve 71 consisting of an electromagnetic on-off valve and a proportional valve 72 downstream of the main valve 71 are provided in the gas supply passage 7 that supplies fuel gas to the burner 3. The portion of the gas supply passage 7 downstream of the proportional valve 72 is divided into a first branch passage 7a that is connected to the first portion ₃₁ of the burner 3 and a second branch passage 7b that is connected to the second portion ₃₂ of the burner 3. A first capacity switching valve 73a and a second capacity switching valve 73b consisting of an electromagnetic on-off valve are provided in the first branch passage 7a and the second branch passage 7b, respectively. The first capacity switching valve 73a and the second capacity switching valve 73b are opened and closed to supply fuel gas to the first portion ₃₁ or to both the first portion ₃₁ and the second portion ₃₂ of the burner 3. In this way, the combustion capacity of the burner 3 is switched between two stages. When the ignition operation of the igniter 32 is performed, a mixture gas of fuel gas and combustion air is supplied to the burner 3.

The hot water supply heat source unit 1a also includes a controller 8 that controls the fan 5, the main valve 71, the proportional valve 72, the first capacity switching valve 73a, the second capacity switching valve 73b, and the igniter 32. The controller 8 is composed of a microcomputer that includes a CPU, ROM, RAM, an A/D converter, an interface, etc. The frame rod 33 and the supply and exhaust unit state detection means _A1 are connected to the controller 8.

The controller 8 is also configured to be able to execute a normal combustion mode and a trial operation mode. In the normal combustion mode, the controller 8 controls the opening degree of the proportional valve 71 and the rotation speed of the fan 5 so that the air-fuel ratio of the mixed gas becomes a value suitable for igniting the burner 3, and also controls the igniter 32 to perform an ignition operation to ignite the burner 3. Here, the air-fuel ratio suitable for igniting the burner 3 is an estimated value that can be determined in consideration of a theoretical value based on the type of fuel gas, the combustion capacity of the burner 3, the air supply capacity of the fan 5, and the like. This estimated value is preset in the controller 8. When combustion is instructed, the controller 8 opens the main valve 71 and the first capacity switching valve 73a, and also opens the proportional valve 72, and controls the opening degree of the proportional valve 71 by the magnitude of the proportional valve current that is passed through the proportional valve 71 to determine the amount of fuel gas supplied to the first portion ₃₁ of the burner 3 so that the air-fuel ratio becomes the estimated value. The controller 8 also controls the amount of combustion air supplied to the first portion ₃₁ of the burner 3 by the rotation speed of the fan 5 .

On the other hand, in the trial operation mode, the controller 8 opens the main valve 71, the proportional valve 72 and the first capacity switching valve 73a, and then controls at least one of the opening degree of the proportional valve 71 and the rotation speed of the fan 5 so that the air-fuel ratio of the mixed gas becomes a value below the lower explosion limit at which ignition is not possible , while performing a purging operation to exhaust the mixed gas supplied to the first part 31 of the burner 3 from the combustion chamber 2a to the outside through the exhaust path 6 for a predetermined period of time.

The control executed by the controller 8 shown in FIG. 1 will be described with reference to FIG. 2. When combustion is instructed, the controller 8 determines whether or not it is in the test operation mode (STEP 1). Here, the user or installer can select the test operation mode or the normal combustion mode through a remote control or the like connected to the controller 8. Also, it is possible to set the controller 8 in advance so that the test operation mode is automatically selected when combustion is instructed for the first time after the hot water supply heat source unit 1a is installed.

If the test operation mode is not selected, the controller 8 executes control in the normal combustion mode described above (STEP 8). On the other hand, if the test operation mode is selected, the controller 8 drives the fan 5 to supply combustion air to the first portion ₃₁ of the burner 3 through the air supply passage 5a (STEP 2). The combustion air supplied to the first portion ₃₁ of the burner 3 passes through the combustion chamber 2a and is exhausted to the outside from the exhaust passage 6. Next, the controller 8 causes the intake and exhaust section state detection means A1 shown in FIG. ₁ to detect the state in the intake and exhaust section A, and determines whether the state in the intake and exhaust section A is abnormal or normal (STEP 3). The controller 8 determines whether the state in the intake and exhaust section A is normal or abnormal based on the change in the fan current value detected by the intake and exhaust section detection means _A1 and a preset threshold value. Specifically, if the change in the fan current value falls below the threshold value, the controller 8 determines that there is an abnormality, such as a blockage, in the condition within the air supply and exhaust section A, and if the change in the fan current value is at or below the threshold value, the controller 8 determines that the condition within the air supply and exhaust section A is normal.

When the condition in the intake and exhaust section A is normal, the controller 8 keeps the rotation speed of the fan 5 constant at a predetermined rotation speed, opens the main valve 71 and the first capacity switching valve 73a shown in FIG. 1, and also opens the proportional valve 71 to control the opening degree, so that the air-fuel ratio of the mixed gas of the fuel gas and the combustion air supplied to the first part ₃₁ of the burner 3 is adjusted to be less than the lower explosion limit, and executes the purge operation as described above (STEP 4). In addition, when the purge operation starts to be executed, a timer is started to measure the duration of the purge operation. On the other hand, when the condition in the intake and exhaust section A is abnormal, the controller 8 reports the abnormality, does not execute the purge operation, cancels the command for combustion, closes the main valve 71, the proportional valve 72, and the first capacity switching valve 73a, stops the fan 5, and ends the test operation mode (STEP 5).

If the condition in the intake and exhaust section A is normal, the controller 8 then causes the intake and exhaust section detection means _A1 to detect the condition in the intake and exhaust section A again while supplying mixed gas with an air-fuel ratio below the lower explosion limit to the first portion ₃₁ of the burner 3, and again determines whether the condition in the intake and exhaust section A is abnormal or normal (STEP 6). If the condition in the intake and exhaust section A is abnormal, the purge operation is stopped, and the process proceeds to STEP 5, where an abnormality is notified, and the test run mode is terminated. If the condition in the intake and exhaust section A is normal, the purge operation is continued.

Then, the controller 8 determines whether the duration of the purge operation measured by the timer is a predetermined time or not (STEP 7). Here, the predetermined time is set in the controller 8, and can be set at the discretion of the user or installer. A specific predetermined time is generally exemplified as one minute. If the predetermined time has elapsed, the timer is stopped and the system transitions to the normal combustion mode as described above (STEP 8). If the predetermined time is less than the predetermined time, the system returns to STEP 6.

Moreover, when the normal combustion mode is selected and combustion is instructed, the controller 8 executes control of the normal combustion mode. However, during execution of the normal combustion mode, if the flame rod 33 does not detect ignition of the first portion ₃₁ of the burner 3 even when the igniter 32 is energized and the ignition operation is repeated a predetermined number of times, the controller 8 transitions to the test operation mode as described above. The predetermined number of ignition operations for transitioning to the test operation mode is preset in the controller 8.

In such a hot water heat source unit 1a, the air in the gas supply passage 7 is replaced with fuel gas by the purge operation performed in the test operation mode, but since the air-fuel ratio of the mixed gas supplied to the first portion ₃₁ of the burner 3 is below the lower explosion limit, it is possible to suppress the occurrence of explosive adhesion in the first portion ₃₁ of the burner 3 during execution of the test operation mode. Therefore, safety during the purge operation is improved.

In addition, in the trial operation mode, prior to the purging operation, the controller 8 determines whether there is an abnormality in the condition of the intake and exhaust section A due to the occurrence of a blockage or the like, or whether the condition in the intake and exhaust section A is normal, so that it is possible to suppress a decrease in the amount of air in the mixed gas caused by an abnormality in the condition of the intake and exhaust section A, or an increase in the air-fuel ratio of the mixed gas caused by a short circuit in which the mixed gas that should have been exhausted flows back into the exhaust path 6. Therefore, it is possible to prevent the supply of mixed gas above the lower explosion limit to the first portion _3-1 of the burner 3 during the purging operation, further improving the safety of the purging operation.

Furthermore, even in the normal combustion mode, if the amount of air in the mixed gas supplied to the first portion _3-1 of the burner 3 becomes excessive and unsuitable for ignition in the first portion _3-1 of the burner 3, the mode automatically switches to the trial operation mode, eliminating the need for the user or installer to go through the trouble of switching to the trial operation mode, thereby improving convenience.

Although the present invention has been described above with respect to one embodiment, the present invention is not limited to the above embodiment. For example, various configurations are possible for the configuration of the burner 3 and the gas supply passage 7 associated therewith. In addition, in the purge operation performed in the trial operation mode, not only the opening degree of the proportional valve 72 is controlled, but also the opening degree of the proportional valve 72 may be kept constant at a predetermined opening _degree to control the rotation speed of the fan 5, or both the opening degree of the proportional valve 72 and the rotation speed of the fan 5 may be controlled, so long as the air-fuel ratio of the mixed gas supplied to the first portion 31 of the burner 3 is made to be a value below the lower explosion limit. Furthermore, the supply and exhaust section state detection means _A1 may employ an air flow sensor or the like that can be installed at an appropriate location in the supply and exhaust section A. In the case of the air flow sensor, a threshold value related to the air flow in the supply and exhaust section A is preset in the controller 8, and the controller 8 determines that the state of the supply and exhaust section A is abnormal, such as a blockage, when the air flow in the supply and exhaust section A detected by the air flow sensor is less than the threshold value, and determines that the state of the supply and exhaust section A is normal when the air flow is equal to or greater than the threshold value.

The test run mode can be executed not only when the first combustion command is issued after the hot water supply heat source device 1a is installed, but also after the gas supply path 7 is replaced with fuel gas. In addition, either STEP 3 or STEP 6 shown in FIG. 2 can be omitted. In addition, in the test run mode, the controller 8 can cause the igniter 32 to perform an ignition operation. In this case, even if the air-fuel ratio of the mixed gas becomes equal to or higher than the lower explosion limit due to some factor, the first portion 31 of the burner ₃ ignites just when the air-fuel ratio reaches the lower explosion limit, so that the occurrence of explosive combustion is suppressed. In addition to the hot water supply heat source device 1a, the combustion device 1 can also be a heating heat source device or the like.

1...combustion device, 2a...combustion chamber, 3...burner, 32...igniter (ignition means), 33...flame rod (ignition detection means), 5...fan, 5a...air supply passage, 6...exhaust passage, 7...gas supply passage, 72...proportional valve, 8...controller, A...air supply and exhaust section, _A1 ...air supply and exhaust section state detection means.

Claims (3)

A combustion device comprising: a burner disposed in a combustion chamber for burning a mixture of combustion air and fuel gas; a fan for supplying the combustion air to the burner via an air supply passage; a gas supply passage for supplying the fuel gas to the burner; a proportional valve provided in the gas supply passage; ignition means for performing an ignition operation for igniting the burner; ignition detection means for detecting ignition of the burner; a controller for controlling the fan, the proportional valve, and the ignition means; and an exhaust passage for exhausting combustion gas generated by combustion in the burner from the combustion chamber to the outside,
The controller is configured to be able to execute a normal combustion mode in which the controller controls the proportional valve aperture and the fan speed so that the air-fuel ratio of the mixed gas becomes a value suitable for igniting the burner, and controls the ignition means to perform an ignition operation to ignite the burner, and a trial operation mode in which the controller controls at least one of the proportional valve aperture and the fan speed so that the air-fuel ratio of the mixed gas becomes a value below the lower explosion limit and therefore cannot be ignited, and a purge operation is performed to exhaust the mixed gas supplied to the burner from the combustion chamber to the outside through the exhaust path for a predetermined period of time. 2. The combustion apparatus according to claim 1, further comprising an intake and exhaust section condition detection means for detecting a condition within the intake and exhaust section, the intake and exhaust section being disposed in the intake and exhaust section from the intake passage through the combustion chamber to the exhaust passage,
The combustion apparatus is characterized in that, in the trial operation mode, the controller causes the intake and exhaust section state detection means to detect the state within the intake and exhaust section prior to the purging operation, and if there is an abnormality in the state within the intake and exhaust section, the controller does not perform the purging operation, and if the state within the intake and exhaust section is normal, the controller performs the purging operation. The combustion device according to claim 1 or 2, characterized in that the controller, when executing the normal combustion mode, transitions to the trial operation mode if the ignition detection means does not detect ignition of the burner even after causing the ignition means to repeatedly perform the ignition operation a predetermined number of times.

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