JP3368609B2 - Combustion control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control device for controlling a burner block whose NOx is reduced mainly by rich and lean combustion by detecting the state of the mixing ratio, the state of the flame mouth temperature and the existence of the flame itself. It is a thing.

[0002]

2. Description of the Related Art Conventionally, there is a combustion control device of this type as shown in FIG. That is, burner burner plate 1
A fan 4 provided on the upstream side so as to form a low m-value flame 2 and a high m-value flame 3 respectively, and a low m-value and a high m-value.
Each gas supply 5, 6 was provided to supply gas to each burner of value. Then, based on the outputs of the respective temperature sensors 7 and 8, the low m-value flame 2 and the high m-value flame 3
Therefore, even if the same output value is shown on both sides of the maximum value or the minimum value, the fan 4 is controlled by distinguishing which side the output value is.

[0003]

However, in the above conventional structure, the low m-value flame 2 or rich flame and the high m-value flame 3 or lean flame are reducing flame and oxidizing flame, respectively, and the temperature sensors 7 and 8 are set. The environment is completely different. Particularly, the low m-value flame 2 has a very low sensitivity to the mixing ratio and a very high sensitivity to the combustion amount. Therefore, there is a change in the sensitivity of the sensor with time and a difference in the service life, which causes a problem in reliability. Further, it is a prerequisite that the combustion states of the low m-value flame 2 and the high m-value flame 3 are uniform, and that the outputs between the temperature sensors 7 and 8 are always balanced in a constant relationship. Therefore, if a change occurs in one of the flames due to clogging of the flame mouth or blockage of intake air, and the balance of the sensor output is lost, the originally set amount of air is not supplied and an abnormal combustion state occurs. Further, it does not mention how to deal with changes in the amount of combustion, and how to deal with changes in the presence or absence of wind and blockage of the air supply and exhaust system.

The present invention solves the above-mentioned problems and provides a low N
Even if the burner block for rich-lean combustion, which is Ox, is subject to external disturbances that affect the combustion state, it is automatically returned to the specified combustion set point, and optimum combustion control is always performed to ensure reliability. The primary purpose is to stop the combustion if it is too high to recover.

The second purpose is to promptly escape from the abnormal state and return to the original combustion set point when a large disturbance is received.

[0006]

In order to achieve the first object of the present invention, the present invention is directed to a flame port for forming a flame, a burner block in which a plurality of the flame ports are arranged, and the vicinity of the flame port. A mixing ratio sensor having sensitivity to the mixing ratio, a temperature sensor for detecting the temperature of the flame opening provided near the upstream side of the flame opening where the mixing ratio sensor is provided , and the presence or absence of flame Ignition sensor, fan that supplies combustion air to the burner block, state setting means that presets the output of the mixing ratio sensor at the optimum excess air ratio according to the combustion amount, and receives and corrects the output signal of the mixing ratio sensor Correction means for outputting a value, control means for controlling the fan air volume so that the deviation between the set value of the state setting means and the correction value of the correction means becomes small, and a flame mouth temperature determination means for determining the output signal of the temperature sensor. Having said temperature And controls the supply of fuel by the detection signal of the capacitor.

In order to achieve the second object, the present invention has sensitivity to a flame port that forms a flame, a burner block in which a plurality of flame ports are arranged, and a mixing ratio provided near the flame port. A mixture ratio sensor and this mixture ratio sensor
A temperature sensor that detects the temperature of the flame opening provided near the upstream side of the flame opening, an ignition sensor that detects the presence or absence of a flame, a fan that supplies combustion air to the burner block, and an optimum value depending on the combustion amount. The state setting means for setting the output of the mixing ratio sensor at various excess air ratios, the correction means for receiving the output signal of the mixing ratio sensor and outputting the correction value, and the deviation between the setting value of the state setting means and the correction value of the correction means If the detection signal of the temperature sensor exceeds a predetermined value, it has a control means for controlling the fan air volume so as to be small and a flame opening temperature determination means for determining the output signal of the temperature sensor. The emergency signal is output to the control means.

[0008]

According to the present invention, with the above-described structure, since the mixing ratio sensor is provided in the vicinity of the flame mouth that forms the flame having the characteristics such as the flame temperature, the ion current and the oxygen concentration, which have high sensitivity, It will be detected well. Based on the output of the mixing ratio sensor at the optimum excess air ratio predetermined by the state setting means according to the combustion amount, the control means controls the fan air volume to supply the combustion air to the burner block. If a predetermined amount of air cannot be supplied due to the presence or absence of wind, the supply / exhaust system being blocked, etc., the mixing ratio sensor will detect that the mixing ratio differs from the value determined according to the combustion amount. Become. The correction means captures this change and calculates and outputs a necessary correction value. Then, the control means compares the set value of the state setting means with the correction value, and increases or decreases the fan air volume so that the difference between the two becomes smaller according to the positive or negative level of the deviation, thereby returning to a predetermined combustion state. become. Here, if the air above the design condition is temporarily blown and the air shortage cannot be corrected due to exceeding the power supply capacity of the device, etc., the temperature of the light flame port rises and the temperature sensor detects this state. . Therefore, necessary fuel supply control is performed so that no abnormality occurs according to the output of the temperature sensor. Further, when the correction amount of air is too large, the flame is extinguished, but in this case, the ignition sensor detects it and similarly performs necessary control.

Further, when the temperature sensor exceeds a predetermined value, an emergency signal is output from the flame outlet temperature determination means to the control means, and the fan is controlled so as to preferentially increase to the maximum air flow rate, so that promptly. Escape from the red-hot area of the pale flame mouth.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a burner and control, and a light burner 11 that forms a light flame 10 on a light flame port 9.
And a rich burner 14 that forms a rich flame 13 on the rich flame mouth 12
Are alternately arranged to form the burner block 15. A fan 16 that supplies combustion air is installed upstream of the burner block 15. Each light burner 1
Nozzles 19 for ejecting and supplying the fuel supplied through the solenoid valve 17 and the proportional valve 18 are mounted on the 1 and the rich burner 14, respectively. A mixing ratio sensor 20 is mounted on the downstream side of the specific light flame port 9, and a temperature sensor 21 is mounted on the upstream side thereof. Similarly, an ignition sensor 22 that detects the presence or absence of the rich flame 13 is mounted on the downstream side of the specific rich flame outlet 12.

The combustion amount calculated from the usage condition is changed from the combustion amount setting means 23 to the proportional valve control means 24 and the state setting means 2
5 is output. The proportional valve control means 24 controls the voltage or current value applied to the proportional valve 18 according to the combustion amount setting signal, and adjusts the flow rate of the fuel that has passed through the solenoid valve 17. The state setting means 25 outputs to the control means 26 a target set value of the mixing ratio sensor 20 at an optimum air excess ratio that is predetermined according to the combustion amount setting signal. Control means 26
Compares the correction value transmitted from the correction unit 27 with the setting value transmitted from the state setting unit 25, and outputs a control signal corresponding to the deviation between the two to the fan control unit 28 to control the fan 16. Then, the combustion air is supplied to the burner block 15. The flame port temperature signal of the light flame port 9 is input from the temperature sensor 21 to the flame port temperature determination means 29. Ignition sensor 2
An ignition signal from 2 is input to the flame detecting means 30. The respective judgment signals from the flame outlet temperature judging means 29 and the flame detecting means 30 are inputted to the valve control means 31, and the valve control means 31 outputs an opening / closing signal to the solenoid valve 17.

The combustion and control operation in the above configuration will be described. The fuel whose flow rate is adjusted by the proportional valve 18 is jetted from each nozzle 19 in a predetermined amount to form a rich and lean flame, and is mixed with the combustion air supplied from the fan 16. Here, in the light burner 11, a lean air-fuel mixture having an equivalence ratio or less is formed, and a lean flame 10 is ejected from the lean flame port 9 to form a lean flame 10.
Similarly, in the rich burner 14, a rich air-fuel mixture having an equal ratio or more is formed, and the rich flame 13 is ejected from the rich flame port 12 to form a rich flame 13. Therefore, in the burner block 15 as a whole, the lean flame 10 and the rich flame 13 are alternately formed, so that rich and lean combustion is realized and low NOx combustion is achieved.

Here, the limit state in combustion control will be described in advance with reference to FIG. When the set combustion amount changes, the optimum mixture ratio of the lean flame 10 and the rich flame 13 considering the combustion limit also changes. Therefore, the excess air ratio m of the entire burner block 15 is controlled to the value indicated by the curve J as the combustion amount changes. When the amount of combustion becomes small, the lean flame 10 comes close to the lean flame port 9, and when the amount of air is small, the flame temperature rises.
Is subjected to abnormal heating, and the red flame area of the light flame mouth as shown in FIG. 2 is generated. On the other hand, if the amount of air is too large, the lean flame 1
0 becomes even leaner, and if the rich flame 13 is extinguished due to blowout or the rich flame 13 similarly increases in air amount, the extinguishing zone shown in FIG. 2 exists.

The control operation for ensuring a stable combustion state in the presence of such a limit on combustion will be described. The combustion amount setting means 23 determines the combustion amount, and the proportional valve control means 24 and the fan control means 28 set an optimum combustion set point corresponding to the combustion amount to the point A. At that time, the operation when the supply / exhaust amount changes due to wind or the like will be described with reference to FIG. When the exhaust resistance increases due to the breeze at time t1, the combustion set point starts to move from the point A to the point B, and the output 32 of the mixing ratio sensor 20 has a set value 33 that is predetermined according to the combustion amount. Detects that it has begun to deviate. The correction means 27 captures this change and predicts a steady fan rotation speed in which the response delay of the mixture ratio sensor 20 is corrected, and outputs it as a correction value. And the control means 26
In comparison with the set value 33 of the state setting means 25, since a positive deviation is generated, the deviation is made zero by increasing the fan rotation speed 34. As a result, the combustion set point returns from point B to point A again. Also, when the slight wind stops at time t2, the above-mentioned operation is similarly performed, and a negative deviation occurs this time, so that the fan rotation speed 34 is reduced. Therefore, immediately after the breeze has stopped, it moves from point A to point C temporarily, but is returned to point A again.

When the exhaust resistance greatly increases due to the strong wind at the time t3, the combustion set point moves from the point A toward the point D in the red heat region of the light flame port 10. In this case, since the output of the mixture ratio sensor 20 is largely deviated, the correction value output from the correction unit 27 is also large. The output 35 of the temperature sensor 21 is affected by the heat capacity of the lean flame port 9 and, after a certain time delay, transiently exceeds the predetermined value 36 until it escapes from the red heat region of the lean flame port 9. However, since the fan rotation speed 34 is significantly increased, it becomes less than or equal to the predetermined value 36 at time t5.
At this time, since the time from t4 to t5 does not exceed the predetermined time T, which is determined in advance, the flame port temperature determination means 29 does not output the closing signal of the solenoid valve 17 to the valve control means 31. Then, when the deviation becomes zero, the combustion set point is returned to point A again.

A description will now be given of a case where a gust is further generated and the exhaust resistance is greatly increased to move from point A to point E all at once. Since the output 32 of the mixing ratio sensor 20 again deviates from the set value 33, the rotation speed correction means 27 makes a point A.
The predicted fan rotation speed that is further required for returning to the output is output as a correction value, but this time, the rotation speed exceeding the limit of the fan motor capacity is required. The fan motor control means 28 keeps the fan rotation speed set to the rotation speed limit value 37 to protect the fan motor. Therefore, the output 35 of the temperature sensor 21 rises again and reaches the predetermined value 3 at the time t7.
Over 6. Since the fan rotation speed has reached the limit value, the temperature sensor 21 does not operate even at time t8 when the set time T has elapsed.
Output 35 does not fall below a predetermined value 36. At this time, the flame outlet temperature determination means 29 sends the solenoid valve 1 to the valve control means 31.
The closing signal 7 is output to stop the fuel supply. Therefore, the combustion set point remains in the red heat range, and the light flame port 9 is not deformed or burned. At this time, the wind suddenly stops within the set time T, and the exhaust resistance drops sharply, causing the fan 1
When the amount of air blown from 6 becomes abnormally large and the rich flame 13 is also blown away, the ignition sensor 22 detects extinction. At this time, the flame detection means 30 outputs a closing signal of the electromagnetic valve 17 to the valve control means 31, and the supply of fuel is stopped.

Next, the case where the emergency signal is output to the control means 26 will be described with reference to FIG. In this case, in FIG. 1, a path is newly provided for outputting an emergency signal indicated by a broken line from the flame port temperature determination means 29 to the control means 26. As described with reference to FIG. 3, the same control operation as described above is performed until time t4. At time t4, when the output 35 of the temperature sensor 21 exceeds the predetermined value 36, the flame outlet temperature determination means 29 outputs an emergency signal 38 to the control means 26. The control means 27 gives priority to this emergency signal, and the fan control means 28 increases the fan rotation speed 34 to the rotation speed limit value 37.
Therefore, the fan 16 supplies the maximum allowable air volume to the burner block 15, so that the red heat zone can be escaped at a time t5 ′ earlier than the time t5. When the output 35 of the temperature sensor 21 becomes equal to or less than the predetermined value 36, the emergency signal 38 is stopped, and as described above, the fan 1 according to the level of the deviation from the set value 33 of the mixing ratio sensor 20.
Control 6

In the above embodiment, the burner block for rich and lean combustion is explained, but it may be applied to the burner block for all primary combustion. Further, although the case where the mixing ratio sensor 20 and the temperature sensor 21 are installed one by one in a specific burner has been described, they may be installed in a plurality of burners. Further, although the control means has shown the case of controlling the fan rotation speed, it may be a means for controlling a current value or a voltage value for controlling the fan, or may be a means for separately providing a damper or the like to control the passage. What is essential is that the amount of combustion air can be controlled.

[0019]

As described above, according to the combustion apparatus of the present invention, the following effects can be obtained.

(1) When the combustion set point deviates from a predetermined position due to disturbance or the like, a change in the output of the mixing ratio sensor is detected, a correction value is output from the correction means, and the deviation from the set value is reduced. By controlling the fan air volume by the control means as described above, the setting point is returned to the original setting point. Therefore, even if a temporary disturbance factor is generated or a change with time, a stable N value is maintained.
Ox combustion can be maintained.

(2) Even when the combustion set point cannot be returned to the predetermined position because the correction value cannot be corrected only by the correction value of the correction means, if the air is insufficient, the temperature sensor indicates the red heat state of the light flame mouth. In the case of excess air, the ignition sensor detects the blowout of the flame and stops the fuel supply, so that abnormal combustion does not continue and safety can be guaranteed.

(3) When the flame mouth starts to glow red and the output of the temperature sensor exceeds a predetermined value, the flame mouth temperature determination means outputs an emergency signal to the control means to quickly escape from the red heat zone. Therefore, the reliability of the flame mouth is improved.

(4) In the unlikely event that the red hot state of the flame mouth continues for a set time or longer, the fuel supply is stopped, so that the flame mouth is not deformed or damaged. Therefore, it is possible to use sheet metal as the material of the flame mouth, which is inexpensive and improves mass productivity.

[Brief description of drawings]

FIG. 1 is a block diagram of a burner and control of a combustion control device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a combustion limit region and a combustion set point by a combustion amount and an excess air ratio.

FIG. 3 is a time chart showing the control response due to disturbance.

FIG. 4 is a time chart diagram showing control response by an emergency signal.

FIG. 5 is an overall cross-sectional view of a conventional combustion control device

[Explanation of symbols]

9 light flame mouth 10 light flame 12 rich flame mouth 13 rich flame 15 burner blocks 16 fans 20 Mixing ratio sensor 21 Temperature sensor 22 Ignition sensor 25 State setting means 26 Control means 27 Correction means 29 Flame mouth temperature determination means

─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Keijiro Kunimoto 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Junichi Ueda 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. Company (72) Inventor Yoichi Kimura 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-6-117628 (JP, A) (58) Fields investigated (Int.Cl . ^7, DB name) F23N 1/02 101 F23C 11/00 329 F23N 5/14 320

Claims (2)

(57) [Claims] 1. A flame port for forming a flame, a burner block in which a plurality of the flame ports are arranged, a mixing ratio sensor provided in the vicinity of the flame port and having a sensitivity for a mixing ratio, and the mixing ratio.
A temperature sensor provided near the upstream side of the flame port provided with a sensor for detecting the temperature of the flame port, an ignition sensor for detecting the presence or absence of the flame, and a combustion air supply to the burner block. A fan, state setting means for setting the output of the mixing ratio sensor in advance at an optimum excess air ratio according to the combustion amount, correction means for receiving an output signal of the mixing ratio sensor and outputting a correction value, and the state setting Control means for controlling the fan air volume so that the deviation between the set value of the means and the correction value of the correction means becomes small, and flame opening temperature determination means for determining the output signal of the temperature sensor. A combustion control device that controls the supply of fuel by signals. 2. A flame opening for forming a flame, a burner block in which a plurality of the flame openings are arranged, and the mixing ratio sensor are provided.
A mixing ratio sensor provided in the vicinity of the upstream side of the flame opening and having a sensitivity to the mixing ratio, a temperature sensor provided near the flame opening for detecting the temperature of the flame opening, and detecting the presence or absence of the flame. Ignition sensor, a fan for supplying combustion air to the burner block, state setting means for setting the output of the mixing ratio sensor at an optimum excess air ratio in advance according to the amount of combustion, and the mixing ratio sensor Of the output signal of the temperature sensor, and a correction means for outputting a correction value, a control means for controlling the fan air volume so as to reduce the deviation between the setting value of the state setting means and the correction value of the correction means, and the output signal of the temperature sensor. A combustion control device which has a flame outlet temperature determination means for determining, and outputs an emergency signal from the flame outlet temperature determination means to the control means when the detection signal of the temperature sensor exceeds a predetermined value.