JP2002039528A - Combustion equipment - Google Patents

Abstract

(57) [Problem] To detect an excess air ratio with a flame rod and burn at a desired excess air ratio to suppress generation of NOx, CO, and HC. SOLUTION: A light-side frame rod 30, a dark-side frame rod 31, a light-side resistor 32 and a dark-side resistor 33 provided between the light-side frame rod 30, the dark-side frame rod 31, and a power supply 34, respectively, Frame rod 3
And a first potential difference detecting means 35 for detecting a potential difference between the first frame rod 31 and the dark side frame rod 31. Then, a small difference in flame resistance can be detected without being affected by noise of the same phase due to a change in the excess air ratio, and the excess air ratio can be accurately detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low NOx combustion apparatus, and more particularly to a lean combustion system.

[0002]

2. Description of the Related Art Conventionally, a combustion apparatus using a lean-burn combustion system is generally the one described in JP-A-6-117628. This combustion device is shown in FIG. Reference numeral 1 denotes a burner unit that heats a heat exchanger 2 for heating water. The burner unit 1 has a light burner 3a for burning a lean premix with a large excess air ratio and a rich burner 3b for burning a rich premix with a small excess air ratio. 4 is a fan for supplying combustion air. Light flame side frame rod 5a
And the rich flame side frame rod 5b are inserted into the light flame and the rich flame, respectively. Light flame side frame rod 5a
The controller 6 controls the on-off valve 7 for interrupting the supply of the fuel gas, the regulating valve 8 for adjusting the fuel gas supply amount, and the fan 4 based on the output of the rich flame side frame rod 5b.

[0003] In the above configuration, the rich flame stabilizes a light flame having a low flame temperature and a small NOx emission.
Here, under the normal condition of the excess air ratio, the lean flame side frame rod 5a detects the inner flame of the lean flame, and the rich flame side frame rod 5b detects the outer flame of the rich flame.

[0004] When the excess air ratio decreases, the length of the lean flame becomes shorter, and the lean flame side frame rod 5a deviates from the inner flame and comes to the outer flame. When the lean flame side frame rod 5a detects the external flame, the excess air ratio is detected to be too small.

On the other hand, with respect to the rich flame, when the low air excess ratio state is reached, the length of the rich flame becomes longer, and the rich flame side frame rod 5b comes out of the outer flame and comes to be located in the inner flame. When the rich flame side frame rod detects the internal flame, the excess air ratio is detected to be too small.

Japanese Unexamined Patent Publication No. Hei 5-322159 has the same configuration as that of Japanese Unexamined Patent Publication No. Hei 6-117628, and detects that when the excess air ratio becomes low, the flame rod side flame rod output is reduced, and the air is detected. Detects excessive ratio undersizing.

[0007]

SUMMARY OF THE INVENTION
In the combustion device described in JP-B-117628, the flame rod output is continuous due to a change in the excess air ratio regardless of whether the lean flame side frame rod 5a and the rich flame side frame rod 5b are arranged in any of the rich flame and the lean flame. Change. The length of the flame changes according to the input.
Further, the flame rod output temporally fluctuates due to minute temporal fluctuations of the fuel and air supply amounts. Therefore, it is difficult to detect whether the frame rod is located in the inner flame or the outer flame of the flame, and it is difficult to accurately detect the excess air ratio.

It is well known that in the case of a so-called Bunsen flame in which there is no light flame on both sides of the rich flame, the flame rod output is maximized when the excess air ratio of the premixed air is in the range of 0.8 to 1. . When the excess air ratio of the premixed air becomes excessively large or small, the output of the frame rod greatly decreases, and the excessively large or small excess air ratio can be detected based on the output of the frame rod. However, in the case of a rich flame, it is difficult to detect an excess air ratio that is too small even if a flame rod is arranged on the rich flame. This is because if the excess air ratio becomes too small, the excess air ratio of the lean premix decreases and approaches 1, and the flame temperature rises. It is because it is difficult to decrease.
For this reason, Japanese Unexamined Patent Publication No. Hei 5-322159 has a problem that it is difficult to detect an excessively small air ratio with the rich flame side frame rod 5b.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a light frame rod inserted into a lean flame, a dark frame rod inserted into a rich flame, and the light frame rod. And a power supply, a light-side resistor provided between the dark-side frame rod and the power supply, and a first potential difference detection for detecting a potential difference between the light-side frame rod and the dark-side frame rod. Means.

According to the above invention, the change of the excess air ratio causes the light flame resistance between the light-side frame rod and the light flame port and the dark flame resistance between the dark-side frame rod and the light flame port to change. A difference occurs, and the difference between the light flame resistance and the rich flame resistance is detected by the information of the potential difference, so it is possible to detect the minute flame resistance difference without being affected by the noise of the same phase, and accurately detect the excess air ratio. it can.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A combustion apparatus according to a first aspect of the present invention has a light flame port in which a lean premixture is burned to form a lean flame, and a rich flame is formed by burning a rich premixture. Rich flame outlet, and a light side frame rod inserted into the light flame,
A dark-side frame rod inserted into the deep flame, a power supply for applying a voltage to the light-side frame rod and the dark-side frame rod, a light-side resistor provided between the light-side frame rod and the power supply, A dark-side resistor provided between the dark-side frame rod and the power supply, a first potential difference detecting unit that detects a potential difference between the light-side frame rod and the dark-side frame rod, and a fuel supply unit that supplies fuel. Air supply means for supplying air, and control means for controlling the fuel supply means or the air supply means based on the detection value of the first potential difference detection means.

The change in the excess air ratio causes a difference between the light flame resistance between the light side frame rod and the light flame port and the light flame resistance between the deep side frame rod and the light flame port,
Since the difference between the light flame resistance and the rich flame resistance is detected by the information of the potential difference, a minute difference in the flame resistance can be detected without being affected by the noise of the same phase, and the excess air ratio can be accurately detected.

In the combustion apparatus according to the second aspect of the present invention, the resistance values of the light-side resistance and the deep-side resistance are the same.

And detecting a light flame resistance between the light side frame rod and the light flame port, a light flame resistance between the dark side frame rod and the light flame port, a light side resistance, a dark side resistance, and a first potential difference detection. Since the means forms a so-called Wheatstone bridge circuit, the potential difference can be detected accurately.

In the combustion apparatus according to a third aspect of the present invention, when the value detected by the first potential difference detecting means based on the rich side frame rod becomes smaller than the first threshold value for determining that the excess air ratio is too small. Then, the control means reduces the fuel supply amount or increases the air supply amount.

Then, when the excess air ratio decreases, the excess air ratio of the lean premixture approaches 1 and the lean flame resistance decreases and the lean side flame rod potential decreases. The detection value of the potential difference detecting means decreases. Therefore, a decrease in the excess air ratio can be detected, and when the detected value becomes smaller than the first threshold value, the fuel supply means or the air supply means is controlled so that the excess air ratio increases, thereby suppressing the NOx emission. it can.

According to a fourth aspect of the present invention, the detected value of the first potential difference detecting means based on the rich side frame rod is smaller than a second threshold value for determining that the excess air ratio is abnormally small. Then, the control means stops the combustion.

Since an excessively small excess air ratio such as a supply / exhaust blockage can be detected, abnormal combustion such as incomplete combustion can be suppressed.

A combustion apparatus according to a fifth aspect of the present invention is provided with a second potential detecting means for detecting a potential difference before and after the light-side resistance or the high-side resistance, and the control means controls the second potential difference detecting means. The fuel supply means or the air supply means is controlled based on the detected value.

In addition to the first potential difference detecting means, the excess air ratio can be more accurately controlled by the second potential detecting means for detecting a potential difference before and after the light-side resistance or the deep-side resistance.

In the combustion apparatus according to claim 6 of the present invention, when the detected value of the second potential difference detecting means is smaller than a third threshold value for determining that the excess air ratio is excessive, the controlling means reduces the fuel supply amount. Increase or decrease the air supply.

When the excess air ratio increases, the lean and rich flame resistances increase, so that the value detected by the second potential difference detecting means decreases. Therefore, an increase in the excess air ratio can be detected, and when the detected value is smaller than the third threshold value, the fuel supply means or the air supply means is controlled so that the excess air ratio decreases, thereby suppressing the generation of CO, HC, and the like. be able to.

In the combustion apparatus according to claim 7 of the present invention, the third threshold value decreases as the fuel supply amount decreases.

When the fuel supply amount decreases, the lean and rich flame resistances increase, and the detection value of the second potential difference detecting means decreases at the same excess air ratio. Therefore, by decreasing the third threshold value as the fuel supply amount decreases,
The excess air ratio can be accurately controlled under a wide range of fuel supply.

The combustion apparatus according to claim 8 of the present invention has an upper limit and a lower limit for the correction amount of the fuel supply amount or the air supply amount.

Further, it is possible to prevent the fuel supply amount or the air supply amount from being excessively controlled due to the abnormality of the control system such as the frame rod, resulting in abnormal combustion.

According to a ninth aspect of the present invention, when the detected value of the second potential difference detecting means is smaller than a fourth threshold value for determining that the excess air ratio is abnormally large, the control means stops the combustion. Let it.

When the excess air ratio becomes excessively large, the combustion is stopped, so that the generation of large amounts of CO, HC and the like can be suppressed.

[0029] A combustion apparatus according to claim 10 of the present invention comprises:
The display unit is provided, and the control unit displays the abnormality by the display unit.

Then, it is possible to warn the user of abnormal combustion due to the abnormality of the excess air ratio and to prompt maintenance.

[0031]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a view showing a combustion apparatus according to Embodiment 1 of the present invention, FIG. 2 (a) is a view showing a detection value of a first potential difference detecting means in this embodiment, and FIG. FIG. 4B is a diagram showing a detection value of the second potential difference detecting means in the present embodiment.

In FIG. 1, a light burner 23 having a light flame port 22 in which a light flame 21 having a large excess air rate is formed and a light burner 26 having a rich flame port 25 in which a rich flame 24 having a small excess air rate is formed. Constitutes a burner unit 27. The burner unit is electrically grounded,
The light flame port 22 and the rich flame port 25 having the same potential as the burner unit 27 are also grounded. 28 is a fuel supply means for supplying fuel such as city gas, and 29 is an air supply means for supplying air for combustion. A light-side frame rod 30 is disposed downstream of the light flame port 22 and a dark-side frame rod 31 is disposed downstream of the dark flame port 25, and a voltage is applied by a power source 34 via a light-side resistor 32 and a dark-side resistor 33, respectively. I have. One side of the power supply 34 is grounded.

Reference numeral 35 denotes first potential difference detecting means for detecting a potential difference between the light frame rod 30 and the dark frame rod 31 with reference to the dark frame rod 31. 36
Is a second potential difference detecting means for detecting a potential difference before and after the light-side resistor 32, and 37 is a third potential difference detecting means for detecting a potential difference before and after the dark-side resistor 33. The control means 38 inputs the detection values of the first potential difference detection means 35, the second potential difference detection means 36 and the third potential difference detection means 37, and controls the display means 39, the fuel supply means 28 and the air supply means 29. .

Next, the operation and operation will be described. The fuel supply means 28 and the air supply means 29 supply fuel and air to the light burner 23 and the rich burner 26, respectively. Here, the fuel supply amount of the light burner 23 and the air supply amount of the light burner 23 are larger than those of the dark burner 26. A light premixed gas having a large excess air ratio is generated in the light burner 23, and is blown out from the light flame port 22 to form a light flame 21. On the other hand, the rich burner 26 generates a rich premixture with a small excess air ratio,
5 and a rich flame is formed. The control means 38 receives the detection values of the first potential difference detection means 35, the second potential difference detection means 36, and the third potential difference detection means 37, detects the excess air ratio, and displays the display means 39, the fuel supply means 28, The air supply means 29 is controlled.

Here, due to the change in the excess air ratio, the light flame resistance between the light side frame rod 30 and the light flame port 22 and the light flame resistance,
A difference is generated between the rich flame resistance between the rich flame rod 31 and the rich flame port 25, and the difference between the light flame resistance and the rich flame resistance is detected by the information of the potential difference.
A minute difference in flame resistance can be detected without being affected by in-phase noise caused by a minute change in the voltage of the power supply 34 with time, and the control means 38 can accurately detect the excess air ratio.

The light resistance and the dark resistance have the same resistance value. Therefore, since the light flame resistance, the rich flame resistance, the light side resistance 32, the dark side resistance 33 and the first potential difference detecting means 35 form a so-called Wheatstone bridge circuit,
The potential difference can be accurately detected.

Further, in addition to the first potential difference detecting means 35,
The excess air ratio can be more accurately controlled by the second to third potential detecting means 36 to 37 for detecting the potential difference before and after the light-side resistor 32 to the dark-side resistor 33.

The details of the detection of the excess air ratio will be described with reference to FIGS. 2 (a) and 2 (b). When the excess air ratio decreases, the excess air ratio of the lean premixture approaches 1 and the temperature of the lean flame 21 increases, so that the lean flame resistance decreases and NOx increases. As the light flame resistance decreases, the potential of the light side frame rod 30 decreases and the dark side frame rod 31
, The detection value of the first potential difference detecting means 35 based on the dark side frame rod 31 becomes smaller. Accordingly, an excessively small state of the excess air ratio can be detected, and the control means 38 decreases the fuel supply amount or the air so that the excess air rate increases when the detection value of the first potential difference detection means 35 becomes smaller than the first threshold value. By increasing and correcting the supply amount, combustion can be performed at a desired excess air ratio, and the emission amount of NOx can be suppressed.

Further, when the excess air ratio becomes abnormally small due to a so-called air supply / exhaust blockage or the like, a large amount of CO is generated due to a lack of oxygen. At this time, the detection value of the first potential difference detecting means 35 further decreases. When the detection value of the first potential difference detecting means is smaller than the second threshold value, the control means 38 determines that the excess air ratio is abnormally small and stops the combustion, so that a large amount of CO is generated due to incomplete combustion. Can be suppressed. At this time, the control means 38 displays an error message on the display means 39 to notify the user.

On the other hand, when the excess air ratio increases, especially the lean premixed gas approaches the flammable limit, the flame temperature of the lean flame decreases, and C
O and HC generation amount increases. At this time, since the light and rich flame resistances increase, the detection values of the second potential difference detecting means 36 and the third potential difference detecting means 37 decrease. Accordingly, the excessive state of the excess air ratio can be detected, and the control means 38 increases or decreases the fuel supply amount so that the excess air rate decreases when the detection value of the second potential difference detecting means 36 becomes smaller than the third threshold value. By reducing the amount of air supply, combustion can be performed at a desired excess air ratio, and generation of CO, HC, and the like can be suppressed. The second potential difference detecting means 36
Has been described, but the third potential difference detecting means 37
Can also be used.

Here, when the fuel supply amount decreases, the lean and rich flame resistances increase, so that the detection values of the second potential difference detecting means 36 and the third potential difference detecting means 37 decrease at the same excess air ratio. By reducing the third threshold value as the fuel supply amount decreases, the excess air ratio can be accurately controlled under a wide range of fuel supply amount.

Also, by providing an upper limit and a lower limit to the correction amount of the fuel supply amount or the air supply amount, the fuel supply amount or the air supply amount is excessively controlled due to some abnormality of the control system such as the frame rod and abnormal combustion. Can be suppressed beforehand.

When the excess air ratio further increases, the value detected by the second potential difference detecting means 36 decreases, and large amounts of CO and HC are generated. Here, when the detection value of the second potential difference detecting means 36 falls below the fourth threshold value, it is determined that the excess air ratio is abnormally large, and the combustion is stopped. As a result, a large amount of CO, HC and the like can be suppressed. At this time, the control means 38 displays an error message on the display means 39 to notify the user. In the embodiment, a liquid fuel such as kerosene may be used.

[0045]

As described above, according to the first aspect of the present invention, the light flame resistance between the light side frame rod and the light flame port and the light flame resistance between the dark side frame rod and the light flame port are caused by the change of the excess air ratio. The difference between the rich flame resistance and the rich flame resistance is detected, and the difference between the light flame resistance and the rich flame resistance is detected by the information of the potential difference, so the minute flame resistance difference is detected without being affected by the noise in the same phase. It is possible to accurately detect the excess air ratio.

Further, the invention according to claim 2 provides a light flame resistance between the light side frame rod and the light flame port, a rich flame resistance between the dark side frame rod and the light flame port, a light side resistance, and a light flame resistance. Since the side resistance and the first potential difference detecting means form a so-called Wheatstone bridge circuit, the potential difference can be detected accurately.

Further, according to the third aspect of the present invention, when the excess air ratio decreases, the excess air ratio of the light premixed gas approaches 1 and the light flame resistance decreases, and the light side flame rod potential decreases. The detection value of the first potential difference detecting means based on the rod becomes smaller. Therefore, a decrease in the excess air ratio can be detected, and when the detected value becomes smaller than the first threshold value, the fuel supply means or the air supply means is controlled so that the excess air ratio increases, thereby suppressing the NOx emission. it can.

Further, the invention according to claim 4 can detect abnormally small excess air ratio such as air supply / exhaust blockage, so that abnormal combustion such as incomplete combustion can be suppressed.

According to a fifth aspect of the present invention, in addition to the first potential difference detecting means, the second potential detecting means for detecting a potential difference before and after the light-side resistance or the high-side resistance further improves the air excess with higher accuracy. Can control the rate.

Further, in the invention according to claim 6, since the lean and rich flame resistance increases as the excess air ratio increases, the detection value of the second potential difference detecting means decreases. Therefore, an increase in the excess air ratio can be detected, and when the detected value is smaller than the third threshold value, the fuel supply means or the air supply means is controlled so that the excess air ratio decreases, thereby suppressing the generation of CO, HC, and the like. be able to.

In the invention according to claim 7, since the lean and rich flame resistance increases when the fuel supply amount decreases, the detection value of the second potential difference detecting means decreases at the same excess air ratio. Therefore, by decreasing the third threshold value as the fuel supply amount decreases, the excess air ratio can be accurately controlled under a wide range of fuel supply amount.

Further, the invention according to claim 8 can prevent abnormal combustion due to excessive control of the fuel supply amount or the air supply amount due to the abnormality of the control system such as the frame rod.

The ninth aspect of the present invention is to stop the combustion when the excess air ratio becomes excessively large.
Etc. can be suppressed beforehand.

Further, the invention according to claim 10 can warn the user of abnormal combustion due to abnormal air excess ratio, and can prompt maintenance.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a combustion device according to a first embodiment of the present invention.

FIG. 2A is a diagram showing a detected voltage characteristic of a first potential difference detecting means of the combustion device. FIG. 2B is a diagram showing a detected voltage characteristic of a second potential difference detecting device of the combustion device.

FIG. 3 is a configuration diagram showing a conventional combustion device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Light flame 22 Light flame 24 Rich flame 25 Rich flame 28 Fuel supply means 29 Air supply means 30 Light side frame rod 31 Dark side frame rod 32 Light side resistance 33 Dark side resistance 34 Power supply 35 First potential difference detection means 36 Second potential difference detecting means 38 Control means 39 Display means

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F23N 5/12 F23N 5/12 JKG (72) Inventor Norio Shiya 1006 Odakadama, Kadoma, Osaka Matsushita Inside Electric Industrial Co., Ltd. (72) Inventor Kazuhisa Morikami 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. ) Inventor Takanobu Fujimoto 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd.

Claims (10)

[Claims] 1. A light flame port in which a lean premix burns to form a light flame, a rich flame port in which a rich premix burns to form a rich flame, and inserted into the light flame. A light-side frame rod, a dark-side frame rod inserted into the rich flame, a power supply for applying a voltage to the light-side frame rod and the dark-side frame rod, and a power supply between the light-side frame rod and the power supply. A light-side resistor provided between the light-side frame rod and the power supply; a dark-side resistor provided between the dark-side frame rod and the power supply; a first potential difference detecting means for detecting a potential difference between the light-side frame rod and the dark-side frame rod; A fuel supply means for supplying air, an air supply means for supplying air, and a control means for controlling the fuel supply means or the air supply means based on a value detected by the first potential difference detection means. . 2. The combustion apparatus according to claim 1, wherein the light resistance and the dark resistance have the same resistance value. 3. The control means decreases the fuel supply amount when a detection value of the first potential difference detection means based on the rich side frame rod becomes smaller than a first threshold value for determining that the excess air ratio is too small. 3. The combustion device according to claim 1, wherein the air supply amount is increased and corrected. 4. The control means stops the combustion when a detection value of the first potential difference detection means based on the rich side frame rod becomes smaller than a second threshold value for determining that the excess air ratio is abnormally small. The combustion device according to claim 1. 5. A system according to claim 1, further comprising a second potential detecting means for detecting a potential difference before and after the light-side resistance or the high-side resistance, wherein the control means controls the fuel supply means or the fuel supply means based on a detection value of the second potential difference detecting means. 3. The combustion device according to claim 1, wherein the air supply means is controlled. 6. The control means increases the fuel supply amount or reduces the air supply amount when the detection value of the second potential difference detection means becomes smaller than a third threshold value for determining that the excess air ratio is excessive. The combustion device according to claim 5. 7. The combustion apparatus according to claim 6, wherein the control means decreases the third threshold value as the fuel supply amount decreases. 8. The combustion apparatus according to claim 3, wherein an upper limit and a lower limit are set for the correction amount of the fuel supply amount or the air supply amount. 9. The control device according to claim 5, wherein the control means stops the combustion when the detection value of the second potential difference detection means becomes smaller than a fourth threshold value for determining that the excess air ratio is abnormally large. Combustion equipment. 10. The combustion apparatus according to claim 4, further comprising display means, wherein the control means displays the abnormality by the display means.