JP6219620B2 - Plate burner control unit - Google Patents

Description

  The present invention has a ceramic burner plate, and controls a plate type burner in which an air-fuel mixture of fuel gas and primary air supplied from a fan is ejected from a plurality of flame holes formed in the burner plate to perform all primary combustion. Relates to the device.

  At the time of ignition, the airflow resistance of the burner plate is lower than that in steady combustion where the temperature of the burner plate is low and the plate temperature is high. Therefore, even if the fan rotation speed is the same, the supply amount of primary air is greater during ignition than during steady combustion. Then, the excess air ratio of the air-fuel mixture (primary air amount / theoretical air amount required for fuel gas combustion) calculated from the fuel gas supply amount and the fan speed is calculated as the excess air ratio and calculated at ignition. If the fuel gas supply rate and the fan speed are controlled so that the excess air ratio is equal to the appropriate value of the excess air ratio during steady combustion, the actual excess air ratio of the air-fuel mixture ejected from the burner plate will become excessive, resulting in a flame. Causes a lift.

  Therefore, conventionally, temperature detection means for detecting the temperature of the burner plate is provided, and the calculated excess air ratio is higher than the appropriate value of the excess air ratio during steady combustion until the temperature detected by the temperature detection means reaches a predetermined reference temperature at the time of ignition. Also, there is known one that performs flame holding control to increase the fuel gas supply amount or decrease the fan rotation speed so as to be corrected to decrease to a small value (see, for example, Patent Document 1).

  Here, conventionally, the reduction correction amount, which is the difference between the appropriate value of the excess air ratio during steady combustion and the calculated excess air ratio during flame holding control, is ignited until the temperature detected by the temperature detection means reaches the reference temperature. Although it is decreased from the initial initial value as the detected temperature increases, this causes the following problems. That is, the ceramic burner plate has low thermal conductivity, and a temperature difference is generated between the portion of the burner plate where the temperature detecting means is disposed and the plate portion away from the burner plate, and the detected temperature of the temperature detecting means rises to the reference temperature. Until then, the temperature of the plate part far from the arrangement part of the temperature detection means may be lower than the detection temperature. If the reduction correction amount is decreased in accordance with the rise in the detected temperature, the actual excess air ratio of the air-fuel mixture ejected from the plate portion having a temperature lower than the detected temperature becomes excessive, resulting in poor combustion. May end up.

JP-A-2-267417

  This invention makes it the subject to provide the control apparatus of the plate-type burner which made it possible to prevent the combustion defect at the time of ignition reliably in view of the above point.

In order to solve the above-mentioned problems, the present invention has a ceramic burner plate, and a mixture of fuel gas and primary air supplied from a fan is ejected from a plurality of flame holes formed in the burner plate. A control device for a plate type burner for primary combustion, comprising temperature detecting means for detecting the temperature of the burner plate, and calculating the air excess ratio of the air-fuel mixture calculated from the supply amount of fuel gas and the rotational speed of the fan As an excess rate, fuel gas is supplied so that the calculated excess air rate is reduced and corrected to a value smaller than the appropriate value of the excess air rate during steady combustion until the temperature detected by the temperature detection means reaches a predetermined reference temperature during ignition. In the case of performing flame holding control that increases the amount or decreases the fan speed, a reduction correction amount that is the difference between the appropriate value of the excess air ratio during steady combustion and the calculated excess air ratio during flame holding control, Decreases to a predetermined holding value big than 0 rather smaller than the initial value after the detection temperature and the adhering without a predetermined time of the temperature detection means from an initial value of the initial fire, then, the temperature detected by the temperature detection means reaches a predetermined The holding value is maintained until the reference temperature is reached.

  Here, when the burner is ignited, the temperature of the burner plate rises with time, but the rise in the detected temperature is delayed due to the influence of the heat capacity of the temperature detecting means. According to the present invention, the correction amount for reducing the excess air ratio due to the flame holding control is decreased over time from the initial value at the beginning of ignition, regardless of the increase in the detected temperature. Accordingly, the decrease correction amount is reduced, and it is possible to prevent a combustion failure at the initial stage of ignition.

  Further, according to the present invention, when the decrease correction amount decreases to the hold value, the decrease correction amount is maintained at the hold value thereafter until the temperature detected by the temperature detecting means rises to the reference temperature. Here, if the reference temperature is set to be equal to the temperature at which the temperature rise of the burner plate has subsided, when the temperature detected by the temperature detecting means rises to the reference temperature, the temperature detecting means is separated from the arrangement portion. The burner plate as a whole, including the plate part, becomes close to the reference temperature. And even if the temperature of the plate part far from the part where the temperature detecting means is arranged is low, the holding value is set so that the actual excess air ratio of the air-fuel mixture ejected from this plate part does not become so large that it causes a combustion failure. Thus, it is possible to effectively prevent the occurrence of defective combustion before the detected temperature rises to the reference temperature.

  Further, in the present invention, when misfiring and reigniting while maintaining the decrease correction amount at the holding value, it is desirable to update the holding value used in the flame holding control to a value larger by a predetermined amount than the previous time. . Here, the reason why misfire occurs while the reduction correction amount is maintained at the holding value is that the holding value is too small and the actual excess air ratio of the air-fuel mixture ejected from the burner plate becomes excessive, causing a flame lift. It is. By updating the hold value to a large value as described above, it is possible to avoid misfire as much as possible while maintaining the decrease correction amount at the hold value after reignition.

The perspective view of a combustion apparatus provided with the plate-type burner controlled with the control apparatus of embodiment of this invention. 1 is a cut side view of the combustion apparatus of FIG. Sectional drawing cut | disconnected by the III-III line | wire of FIG. The expanded cutting top view cut | disconnected by the IV-IV line of FIG. The graph which shows the relationship between the air excess rate of air-fuel | gaseous mixture, and CO concentration (COaf) in combustion exhaust. The flowchart which shows the content of the flame holding control by the control apparatus of this embodiment. The graph which shows the change of the reduction | decrease correction amount by flame holding control.

  With reference to FIGS. 1-3, 1 has shown the plate type burner provided in combustion apparatuses, such as a hot water supply heat source machine. The burner 1 has a ceramic burner plate 3 mounted on the upper surface of a burner body 2 formed in a box shape opening upward.

  A distribution chamber 21 facing the lower surface of the burner plate 3 and a mixing chamber 22 below the bottom wall 211 of the distribution chamber 21 are provided in the burner body 2. An air supply chamber 23 surrounded by a case 231 attached to the lower surface of the burner body 2 is provided below the mixing chamber 22. A fan 24 is connected to one end of the air supply chamber 23 in the horizontal direction.

  In the rear part of the bottom wall 211 of the distribution chamber 21, an opening 212 that communicates the distribution chamber 21 and the mixing chamber 22 is formed. In addition, the distribution chamber 21 is divided into two upper and lower spaces by a partition plate 213. Then, the air-fuel mixture flowing into the lower space of the distribution chamber 21 from the mixing chamber 22 through the opening 212 is formed in the burner plate 3 through the numerous distribution holes 213 a formed in the partition plate 213 and the upper space of the distribution chamber 21. I try to be guided. The air-fuel mixture guided to the burner plate 3 is ejected from a large number of flame holes 3a formed in the burner plate 3 and undergoes all primary combustion.

  The front surface of the mixing chamber 22 is closed by a front wall 221 integrated with the burner body 2. A plurality of nozzle holes 222 are formed in the front wall 221 at intervals in the horizontal direction. A gas manifold 25 is attached to the front surface of the front wall 221 via a partition plate 251 that defines a nozzle passage 223 communicating with the nozzle holes 222 and the front wall 221. An opening (not shown) for communicating the gas passage 252 and the nozzle passage 223 in the gas manifold 25 is formed in the partition plate 251, and an electromagnetic valve 253 for opening and closing the opening is attached to the gas manifold 25. Yes. When the solenoid valve 253 is opened, the fuel gas is supplied to the nozzle passage 223 so that the fuel gas is injected from each nozzle hole 222.

  The bottom surface of the mixing chamber 22 is closed by a bottom plate 224 that is separate from the burner body 2. A wall plate 225 is formed at the front end of the bottom plate 224 so as to face the front wall 221 with a ventilation space and to which fuel gas ejected from each nozzle hole 222 collides. In addition, an air inlet 226 communicating with the air supply chamber 23 is opened at a portion facing the ventilation space on the bottom surface of the mixing chamber 22. The air blown from the fan 24 to the air supply chamber 23 is supplied as primary air to the ventilation space via the air inlet 226, and the fuel gas and the primary air that collide with the wall plate 225 and diffuse are mixed into the mixing chamber 22. Is mixed to produce an air-fuel mixture.

  In this embodiment, the distribution chamber 21 and the mixing chamber 22 are divided into a relatively large # 1 distribution chamber 21 and the mixing chamber 22 by a partition wall 26 integral with the burner body 2, and relatively small # 2 and # 3. The distribution chamber 21 and the mixing chamber 22 are divided into three parts, and the structure is obtained by substantially combining three burners. In addition, three electromagnetic valves 253 are provided in the gas manifold 25 so that fuel gas can be individually supplied to the mixing chambers 22 divided into # 1 to # 3. Also, the burner plate 3 is divided into a # 1 burner plate 3 covering a relatively large # 1 distribution chamber 21 and a # 2 burner plate 3 covering relatively small # 2 and # 3 distribution chambers 21 and 21. Divided into two.

  The combustion apparatus also includes a combustion housing 4 that surrounds the combustion space above the burner plate 3. The combustion housing 4 includes an upper housing 42 that houses a heat exchanger 41 for hot water supply, which is an object to be heated, and a lower housing 43 that is connected to the lower end of the upper housing 42. The front plate portion of the lower casing 43 is provided with a viewing window 44 fitted with glass, and a thermocouple 5, an ignition electrode 6, and a frame rod 7 are attached.

  The thermocouple 5 functions as temperature detecting means for detecting the temperature of the burner plate 3, and is disposed so as to be in contact with the # 2 burner plate 3, as shown in FIGS. It should be noted that no flame hole 3a is formed in the portion of the # 2 burner plate 3 where the thermocouple 5 contacts. The ignition electrode 6 is disposed on one side of the thermocouple 5, and the frame rod 7 is disposed on the other side of the thermocouple 5.

  By the way, in order to cause the air-fuel mixture ejected from the flame holes 3a of the burner plate 3 to undergo primary combustion, the excess air ratio of the air-fuel mixture is made larger than 1. However, as shown in FIG. 5, when the excess air ratio is about 1.6 or more, a flame lift occurs and COaf (CO concentration in the theoretical dry combustion gas) increases rapidly. Further, when the excess air ratio becomes about 1.1 or less, the actual excess air ratio of a part of the air-fuel mixture ejected from the burner plate 3 due to the mixture unevenness of the air-fuel mixture becomes less than 1, and incomplete combustion occurs. COaf increases rapidly. Further, the excess air ratio of the air-fuel mixture calculated from the supply amount of the fuel gas and the rotation speed of the fan 24 is used as the calculated air excess ratio. The excess rate may be smaller or larger than the calculated excess air rate.

  Therefore, the appropriate value λm, which is the control target for the calculated excess air ratio, is about 1.3 so that the actual excess air ratio does not become 1.1 or less due to variations in gas components, or 1.6 or more. Is set. A controller (not shown) controls a proportional valve (not shown) provided in the gas supply path on the upstream side of the gas manifold 25 to vary the supply amount of the fuel gas in accordance with the required combustion amount, and the fan. The rotational speed of 24 is varied in a predetermined proportional relationship with the fuel gas supply amount so that the calculated excess air ratio becomes an appropriate value λm.

  By the way, at the time of ignition, the ventilation resistance of the burner plate 3 is lower than that at the time of steady combustion where the temperature of the burner plate 3 is low and the plate temperature is high. Therefore, even if the fan rotation speed is the same, the supply amount of primary air is greater during ignition than during steady combustion. When the fuel gas supply amount and the fan rotational speed are controlled so that the calculated excess air ratio becomes equal to the appropriate value λm of the excess air ratio during steady combustion at the time of ignition, the actual air of the air-fuel mixture ejected from the burner plate 3 is controlled. The excess rate becomes excessive and causes a flame lift.

  Therefore, in the present embodiment, the calculated excess air ratio decreases to a value smaller than the appropriate value λm of the excess air ratio during steady combustion until the detected temperature of the burner plate 3 by the thermocouple 5 at the time of ignition reaches a predetermined reference temperature. The controller performs flame holding control to increase the fuel gas supply amount or decrease the fan rotation speed so as to be corrected.

  The details of the flame holding control are as shown in FIG. 6. First, in STEP 1, a decrease correction amount Δλ, which is the difference between the appropriate value λm of the excess air ratio during steady combustion and the calculated excess air ratio during flame holding control. A predetermined holding value Δλh determined for is read. Then, after the burner 1 is ignited in STEP 2, the reduction correction amount Δλ is subtracted in STEP 3 until it is determined in STEP 4 that the decrease correction amount Δλ has decreased to the hold value Δλh. As a result of this subtraction process, the decrease correction amount Δλ decreases from the initial value Δλs at the beginning of ignition to a hold value Δλh after a predetermined time ta (for example, 30 seconds), as shown in FIG. The initial value Δλs is set so that the actual excess air ratio is close to the appropriate value λm when the temperature of the burner plate 3 is low.

  When the decrease correction amount Δλ decreases to the hold value Δλh, it is next determined in STEP 5 whether or not the detected temperature T of the burner plate 3 by the thermocouple 5 has increased to a predetermined reference temperature Ta. While T <Ta, it is determined in STEP 6 whether or not a predetermined time has elapsed since the decrease correction amount Δλ decreased to the holding value Δλh. Until the predetermined time elapses, the process proceeds to STEP 7 where the frame rod 7 To determine whether or not the flame has been detected, that is, whether or not it has misfired. And if it is not misfired, it returns to STEP5. Therefore, in principle, the decrease correction amount Δλ is maintained at the hold value Δλh until the detected temperature T reaches the reference temperature Ta.

  When the detected temperature T reaches the reference temperature Ta, or even if the detected temperature T has not reached the reference temperature Ta, the decrease correction amount Δλ decreases to the hold value Δλh for a predetermined time (the temperature unevenness of the burner plate 3 is When the time is sufficiently eliminated (for example, 10 minutes), subtraction processing of the decrease correction amount Δλ in STEP 8 is performed until it is determined in STEP 9 that the decrease correction amount Δλ has decreased to 0. In this subtraction process, the decrease correction amount Δλ is decreased with a constant gradient over time. Then, when the decrease correction amount Δλ becomes 0, the process proceeds to STEP 10 and combustion is continued while maintaining the calculated excess air ratio at the appropriate value λm.

  If it is determined in STEP 7 that a misfire has occurred, that is, if a misfire has occurred while maintaining the decrease correction amount Δλ at the hold value Δλh, the hold value Δλh is updated to a value larger than the previous value in STEP 11. Next, proceeding to STEP 12, it is determined whether or not the updated holding value Δλh has reached a predetermined upper limit value Δλhmax. Read as holding value to use. On the other hand, when Δλh ≧ Δλhmax is established, the process proceeds to STEP 13 to display an abnormality.

  Here, when the burner 1 is ignited, the temperature of the burner plate 3 rises with time, but the rise in the detected temperature is delayed due to the influence of the heat capacity of the thermocouple 5 serving as the temperature detecting means. According to the flame holding control of the present embodiment described above, the decrease correction amount Δλ of the excess air ratio due to the flame holding control is decreased over time from the initial value Δλs at the beginning of ignition, regardless of the delay in the rise of the detected temperature. As the temperature of the burner plate 3 rises with time, the decrease correction amount Δλ is reduced, and it is possible to prevent poor combustion at the initial stage of ignition.

  Further, according to the flame holding control of the present embodiment, when the decrease correction amount Δλ decreases to the hold value Δλh, the decrease correction is basically performed until the detected temperature T increases to the reference temperature Ta or until a predetermined time elapses. The quantity Δλ is maintained at the hold value Δλh. Here, if the reference temperature Ta is set to be equal to the temperature when the temperature rise of the burner plate 3 stops, when the detected temperature T rises to the reference temperature Ta, the reference temperature Ta is separated from the arrangement portion of the thermocouple 5. The entire burner plate 3 including the plate portion becomes a temperature close to the reference temperature Ta. Even if the temperature of the plate part away from the part where the thermocouple 5 is arranged is low to some extent, the actual excess air ratio of the air-fuel mixture ejected from the plate part is excessively high, ie, 1.6 or more. By setting the holding value Δλh so as not to occur, it is possible to effectively prevent a combustion failure from occurring until the detected temperature T rises to the reference temperature Ta.

  Note that the hold value Δλh is maintained until the detected temperature T rises to the reference temperature Ta until the predetermined time elapses. Therefore, even if the detected temperature does not increase due to a failure of the thermocouple 5 or the like, It is advantageous that combustion can be performed at an appropriate excess air ratio without continuing to produce an excessive decrease correction amount in a state where the plate temperature of the plate rises to the reference temperature Ta.

  In addition, according to the flame holding control of the present embodiment, when misfiring and reigniting while maintaining the decrease correction amount Δλ at the holding value Δλh, the holding value Δλh used in the flame holding control is lower than the previous value. It is updated to a value larger by a predetermined amount. Here, the reason why misfire occurs while maintaining the decrease correction amount Δλ at the holding value Δλh is that the holding value Δλh is too small, the actual excess air ratio of the air-fuel mixture becomes excessive, and flame lift occurs. . By updating the hold value Δλh to a large value as in the present embodiment, it is possible to avoid misfire as much as possible after the reignition while maintaining the decrease correction amount Δλ at the hold value Δλh. When the updated holding value Δλh reaches the upper limit value Δλhmax due to repeated misfires, an abnormality is displayed without reigniting for safety measures.

  As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to this. For example, in the above-described embodiment, the flame holding control described above is performed even when the burner plate 3 is not lit and the ignition is performed in a state where the temperature of the burner plate 3 is high after the fire is extinguished. In this case, the decrease correction amount Δλ may be maintained at the hold value Δλh from the beginning of ignition until the detected temperature T reaches the reference temperature Ta. Moreover, in the said embodiment, although the thermocouple 5 is used as a temperature detection means to detect the temperature of the burner plate 3, other sensors, such as a thermistor, may be used.

  DESCRIPTION OF SYMBOLS 1 ... Plate type burner, 3 ... Burner plate, 5 ... Thermocouple (temperature detection means).

Claims (2)

A control device for a plate-type burner having a ceramic burner plate and jetting an air-fuel mixture of fuel gas and primary air supplied from a fan through a plurality of flame holes formed in the burner plate to perform primary combustion entirely. ,
A temperature detection means for detecting the temperature of the burner plate is provided, and the detected temperature of the temperature detection means at the time of ignition is determined by setting the excess air ratio of the air-fuel mixture calculated from the fuel gas supply amount and the fan speed as the calculated excess air ratio. Flame holding that increases the fuel gas supply amount or decreases the fan speed so that the calculated excess air ratio is corrected to decrease to a value smaller than the appropriate value of the excess air ratio during steady combustion until a predetermined reference temperature is reached. In what controls,
The reduction correction amount, which is the difference between the appropriate value of the excess air ratio during steady combustion and the calculated excess air ratio during flame holding control, is set to the initial value after a predetermined time from the initial ignition value regardless of the temperature detected by the temperature detection means. It decreases to a predetermined holding value big than rather smaller 0 than, then the control plate burner, wherein the temperature detected by the temperature detecting means is maintained at a holding value to reach a predetermined reference temperature apparatus. The holding value used in the flame holding control is updated to a value larger by a predetermined amount than the previous time when misfiring and reigniting while maintaining the decrease correction amount at the holding value. The control apparatus of the plate type burner of 1.

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