JPH0674444A - Combustion control method of gas instrument - Google Patents

Abstract

PURPOSE:To reduce the contents of nitrogen oxide compared with that by the prior art in a combustion control method of gas instruments where the contents of nitrogen oxide in combustion exhaust gas are reduced. CONSTITUTION:There are provided a fan 12 for supplying as primary air all amount of air required for combustion to a burner 2, and a flame monitoring sensor such as a flame rod disposed in the vicinity of a flame hole. A flame formed at a particular flame hole 21 corresponding to the flame monitoring sensor is lifted before flames formed at other flame holes 21, 21 are lifted, so that an excess amount of air is increased until the flame monitoring sensor issues an accidental fire signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control method for gas appliances, and more particularly to a combustion control method for reducing the amount of nitrogen oxides contained in combustion exhaust gas.

[0002]

2. Description of the Related Art An all-primary air type gas combustor in which all of the air amount required for complete combustion is mixed as primary air for combustion is constructed as shown in FIG. The gas circuit (10) including the gas amount adjusting valve (15) is connected to the fan case of the air supply fan (12), and the discharge port (13) of the fan (12) has a large number of flame holes ( The burner plate (20) having the holes (21) and (21) is exposed from below. Further, a thermocouple (2) for flame monitoring is provided above the specific flame hole (21) of the burner plate (20).
4) is provided, the output of the thermocouple (24) is applied to the control device (5), by the control device (5),
The opening of the gas amount adjusting valve (15) and the rotation speed of the fan (12) are controlled.

In this case, the amount of nitrogen oxides generated by the combustion of the burner (2) can be suppressed as small as possible, and therefore, the combustion control operation is not hindered. The opening of the gas amount adjusting valve (15) and the rotation speed of the fan (12) are controlled so that a large excess air ratio can be secured. That is, by increasing the excess air ratio, excess air that is not involved in gas combustion is mixed into the flame to cool the flame, and the cooling reduces the amount of nitrogen oxides generated. The excess air ratio and the amount of generated nitrogen oxides have a relationship as shown in FIG. 5, and the amount of generated nitrogen oxides decreases as the excess air ratio λ increases.

Now, when the thermal power control knob (51) is operated in the above-mentioned conventional one, the opening degree of the gas amount control valve (15) and the rotation speed of the fan (12) are controlled according to a predetermined arithmetic expression. Thus, the excess air ratio is adjusted by mixing gas and air so that a combustion state in which the amount of generated nitrogen oxides is suppressed can be secured. Next, while monitoring the output of the thermocouple (24),
The fan (12) and the gas amount adjusting valve (15) are feedback-controlled to perform a fine adjustment to minimize the amount of nitrogen oxides generated while keeping the air excess ratio as large as possible.

That is, when the flame formed in the flame holes (21) (21) is in a red fire state and the output of the thermocouple (24) is large, it is judged that the air is insufficient, and the gas amount adjusting valve (15) is turned on. Squeeze or fan (1
Increase the rotation speed in 2) and change the mixing ratio of gas and air to increase the excess air ratio. On the contrary to the above, when the output of the thermocouple (24) is reduced, it is judged that the air is excessive and the control opposite to the above is performed.

However, the above-mentioned conventional device has a problem that the amount of nitrogen oxides generated cannot be suppressed sufficiently low. The above problems will be described in more detail. When the excess air ratio of the gas ejected from the flame holes (21) (21) increases, the surplus air that does not participate in combustion cools the flame as described above. Then, the combustion speed of the gas becomes slow and the flame tends to lift.

As shown in FIG. 6, the excess air ratio is about 1.2.
On the excess air side above, the thermocouple (24)
Since the output change of is small, the excess air ratio increases extremely significantly when the output of the thermocouple (24) decreases slightly. Therefore, when the air formed in the flame holes (21) (21) is in an air excess state that lifts, it is judged by the output of the thermocouple (24) and the fan (12) and the gas amount adjustment valve are judged. Even if feedback control is applied to (15), there is a high possibility that the misfire has already occurred. Further, since the output of the thermocouple (24) changes slowly, the delay of the control operation of the fan (12) and the like becomes more remarkable, which hinders the realization of proper combustion control.

Therefore, in the above-mentioned conventional one, the set excess air ratio cannot be increased so much to prevent misfire.
In reality, combustion control is performed by setting the excess air ratio to about "1.1" in order to select a range in which the output of the thermocouple (24) changes greatly with respect to the excess air ratio. Therefore, in the case of the above-mentioned conventional one in which the excess air ratio is set to about "1.1",
As can be seen from the above, it cannot be said that the amount of nitrogen oxides generated is sufficiently reduced. In this way, in the above-mentioned conventional one,
The amount of nitrogen oxides generated cannot be sufficiently suppressed because the excess air ratio cannot be increased so much.

When a flame rod is used in place of the thermocouple (24) for monitoring the flame, the flame rod only has a function of detecting the presence or absence of flame. It is not possible to prevent the misfire prior to the misfire simply by simply monitoring the flame formed in (1) as in the conventional one. The present invention has been made in view of the above-mentioned points, and describes a "burner (2) having a plurality of flame holes (21) (21)".
A fan (12) for supplying the burner (2) with all the amount of air required for combustion as primary air, and a gas amount regulating valve (15) inserted in the gas circuit (10) to the burner (2). Further, a flame monitoring sensor such as a frame rod disposed near the flame hole is provided, and the opening of the gas amount adjusting valve (15) and the rotation speed of the fan (12) are controlled by the signal of the flame monitoring sensor. By controlling the excess air ratio by controlling, thereby controlling the amount of nitrogen oxides contained in the combustion exhaust gas, the gas ejected from the flame holes (21) (21) It is an object of the present invention to make it possible to further reduce the amount of nitrogen oxides in the combustion exhaust gas by setting a large excess air ratio. [Invention of Claim 1]

[0010]

[Technical Means] To solve the above-mentioned problems, the technical means of the invention of claim 1 is "a flame hole (21) corresponding to a flame monitoring sensor".
Set the excess air ratio of the gas ejected from the gas slightly higher than the excess air ratio of the gas ejected from the other flame holes (21) (21), and increase the excess air ratio until the flame monitoring sensor gives a misfire signal. I did that. ”

[0011]

The above technical means operates as follows. If the excess air ratio of the gas supplied to the burner (2) is increased by reducing the opening of the gas amount adjustment valve (15) or increasing the rotation speed of the fan (12), the nitrogen oxides in the combustion exhaust gas will be increased. The amount of will gradually decrease.

Further, when the excess air ratio increases, each flame hole (2
1) The flame formed in (21) is likely to lift, but the gas ejected from the specific flame hole (21) corresponding to the flame monitoring sensor is more likely than the gas ejected from other flame holes (21) (21). Since the excess air ratio is set to be slightly higher, the flame formed in the specific flame hole (21) lifts slightly ahead of the flame formed in the other flame hole (21) (21). It will cause a misfire. Then, when the flame of the specific flame hole (21) lifts or misfires and the flame monitoring sensor that monitors the flame stops detecting the presence of the flame, the flame monitoring sensor outputs a misfire signal. . That is, each flame hole (21)
Immediately before the flame formed in (21) lifts or misfires, the flame monitoring sensor outputs a misfire signal.

When the misfire signal is output from the flame monitoring sensor, the fan (12) and the gas amount adjusting valve (15) are controlled to stop the increase of the excess air ratio. As described above, according to the above technical means, by using the misfire signal of the flame monitoring sensor for monitoring the specific flame that slightly misfires before other flames, when the misfire signal is generated, Since the operation of increasing the excess air ratio is stopped, the misfiring can be prevented immediately before the flame formed in these flame holes (21) (21) is misfired, and the gas is ejected from the flame holes (21) (21). Even if the excess air ratio of the gas to be used is increased, there is no risk of the burner (2) misfiring. That is, according to the above technical means, the excess air ratio of the gas ejected from the burner (2) can be set sufficiently large.

[0014]

The invention of claim 1 has the following unique effect. Since the excess air ratio of the gas ejected from the burner (2) can be set large, the amount of nitrogen oxides generated can be reduced accordingly. The misfire signal detected by the flame monitoring sensor is a signal indicating the presence or absence of flame, and is not a signal indicating the amount of heat.Therefore, when the flame is present and when it disappears, the signal output from the flame monitoring sensor is Since the distinction can be made clearly, control of the fan (12) and the like can be performed quickly and easily.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a gas combustion apparatus for carrying out the invention of claim 1 will be described in detail with reference to the drawings. As shown in FIG. 1, a gas ejection pipe (25) is horizontally arranged inside the burner (2) connected to the downstream side of the outlet (13) of the fan (12). Gas is supplied from the gas circuit (10) to the pipe (25). Further, on the side wall upper surface of the gas ejection pipe (25), gas ejection holes (26) (26) are formed at equal intervals, and the gas ejected from these gas ejection holes (26) (26) is It is designed to eject from the flame holes (21) (21) formed in the burner plate (20) above it.

Frame rod (23) as a flame monitoring sensor
Below the specific flame hole (21) corresponding to the air intake pipe (32)
Of the air supply pipe (32), and the upstream end (34) of the air supply pipe (32) is guided into the discharge port (13) of the fan (12). Then, by the supply air from the air supply pipe (32), the excess air ratio of the gas ejected from the specific flame hole (21) corresponding to the frame rod (23), other flame holes (21) (21) It is designed to be larger than the excess air ratio of the gas ejected from the chamber by about 0.3. That is, when the air excess ratio of the gas ejected from each flame hole (21) (21) is 1.3, the air excess ratio of the gas ejected from the specific flame hole (21) corresponding to the frame rod (23) is It is about 1.6.

The frame rod (23) and the gas circuit
The gas amount regulating valve (15) inserted in (10), the fan (12) and the like are electrically connected to the control device (5) as in the conventional one. In this case, the gas supplied from the gas ejection pipe (25) is uniformly ejected from the gas ejection holes (26) (26) provided at equal intervals, and the fan (12) responds to the ejected gas. Supply air is mixed as primary air. And the gas mixed with the air required for combustion is the flame hole (21).
It is ejected uniformly from (21) and burned.

On the other hand, the excess air ratio of the gas ejected from the specific flame hole (21) corresponding to the frame rod (23) depends on the air supply action from the air supply pipe (32). ) Is set to be higher than the excess air ratio of the gas ejected from the above), the flame formed in the specific flame hole (21) above is more air than the flame formed in the other flame hole (21) (21). It burns in the state. And
In order to suppress the amount of nitrogen oxides generated by the combustion of the burner (2), the excess air ratio of the gas ejected from each flame hole (21) (21) is increased. Ascend to 1.3, as shown, the specific flame holes (2
The excess air ratio of the gas ejected from 1) reaches 1.6, and the flame formed in the specific flame hole (21) lifts and misfires.

When the flame in the flame hole (21) corresponding to the frame rod (23) is lifted or misfired and the frame rod (23) is not covered with the flame, the flame rod (23) for detecting the misfire is detected. ) Output current drops to "0" which is applied to the controller (5). Then, as shown in FIG. 2, the control device (5) reduces the rotation speed of the fan (12), whereby the flame formed in each flame hole (21) (21) is misfired. The air excess ratio of the gas ejected from the flame holes (21) (21) is slightly decreased. That is, the flame hole (21) corresponding to the frame rod (23)
The excess air ratio of the gas ejected from the flame reaches 1.6
(21) When the flame of (21) disappears, control is performed to slightly reduce the excess air ratio of the other flame holes (21) and (21) whose excess air ratio is 1.3 at this time. Also, as a result of lowering the rotation speed of the fan (12), the flame hole (21) corresponding to the frame rod (23)
When the flame is reformed, the output current of the frame rod (23) for detecting this is judged to increase the rotation speed of the fan (12) to increase the excess air ratio.

As described above, by increasing or decreasing the rotation speed of the fan (12) while monitoring the output of the frame rod (23), the excess air ratio of the gas ejected from each flame hole (21) (21) can be reduced. Control to about 1.3. In the above embodiment,
Although the excess air ratio is controlled by controlling the rotation speed of the fan (12), the excess air ratio may be controlled by controlling the opening of the gas amount adjusting valve (15).

The embodiment shown in FIG. 3 has a gas ejection pipe (25).
Multiple large-diameter holes (27) (27) at equal intervals on the upper surface of the side wall of the
And one small hole (28), and each large hole (2
7) Partition wall (29) (2) that partitions the (27) and small diameter hole (28) from each other
9) are arranged at equal intervals. In this case, since the amount of gas ejected from the small diameter hole (28) is smaller than the amount of gas ejected from the other large diameter holes (27) (27), the flame holes located above the small diameter hole (28). The excess air ratio of the gas ejected from (21) becomes higher than that of other flame holes (21) (21). Then, by determining the output of the flame rod (23) facing the flame holes (21), (21) having a high excess air ratio, the combustion operation is controlled as in the first embodiment.

In the above embodiment, one large-diameter hole (27) or one small-diameter hole (28) is provided in each of the single compartment spaces partitioned by the compartment walls (29) and (29). Multiple small holes in the compartment space
(28) (28) may be made to correspond, and a single or a plurality of large diameter holes (27) may be made to correspond to other compartment spaces. In this case, the total area of the small-diameter holes (28) (28) is the area of one large-diameter hole corresponding to the single compartment space or the sum of a plurality of large-diameter holes corresponding to a single compartment space. Make it smaller than the area.

Further, the partition wall (29) for partitioning the large diameter holes (27) (27) is not necessarily provided. Further, when the distance between the burner plate (20) and the gas ejection pipe (25) is small, the flame holes (21) corresponding to the small diameter holes (28) and the flame holes corresponding to the large diameter holes (27) (27). (21) When it is possible to provide a difference in the amount of gas flowing into each of (21), it is not necessary to provide the partition wall (29).
In each of the above embodiments, the flame rod (23) was adopted as a flame monitoring sensor, but if it is a system that can instantly determine the presence or absence of flame, an optical sensor such as a phototransistor will prevent flame misfire. You may make it detect. [Invention of Claim 2] The invention of Claim 2 solves the same problem as the invention of Claim 1 above.

[0024]

[Technical Means] The technical means of the invention according to claim 2 for solving the above-mentioned problems is "a flame hole (21) corresponding to a flame monitoring sensor".
The gas ejection speed from the flame was set slightly higher than the ejection speed of the gas ejected from the other flame holes (21) (21), and the excess air ratio was increased until the flame monitoring sensor gave a misfire signal. That is.

[0025]

[Operation / Effect] According to the above technical means, the gas ejection speed from the flame hole (21) corresponding to the flame monitoring sensor is different from that of another flame hole (21).
Since it is set slightly higher than the gas ejection speed from (21), in the excess air state, the flame formed in the former flame hole (21) is formed in the latter flame hole (21) (21). A slight advance of the flame will cause a lift and misfire.

Therefore, according to the above technical means, like the invention of claim 1, the misfire can be prevented immediately before the flame formed in each flame hole (21) (21) is misfired. , Even if the excess air ratio is increased, there is no risk that the burner (2) will misfire. That is, it is possible to reduce the amount of nitrogen oxides generated by setting a large excess air ratio.

[0027]

Next, an embodiment of the invention of claim 2 will be described with reference to FIG. In the combustion device shown in FIG.
Of the flame holes (21) (21) drilled in the burner plate (20), the diameter of the lower part of the specific flame hole (21) corresponding to the frame rod (23) is enlarged to reduce the diameter of the flame hole (21). By shortening the distance between the portions, the passage resistance of the gas passing through the flame hole (21) portion is reduced. Therefore, the gas ejection speed from the specific flame hole (21) becomes higher than the ejection speed of the other flame holes (21) (21), and the gas is formed in the flame hole (21) portion corresponding to the frame rod (23). The generated flame is easier to lift than the flames formed in the other flame holes (21) (21). That is, the flame formed in the specific flame hole (21) with the high gas ejection speed is designed to be misfired prior to the flame formed in the other flame hole (21) (21). . In this embodiment, when the excess air ratio of the gas ejected from the flame holes (21) (21) reaches 1.3, the flame of the flame holes (21) corresponding to the frame rod (23) The gas ejection speed of the specific flame hole (21) is set to be slightly higher so as to lift and misfire.

In this case, the other flame holes (21) (21) are lifted and misfired, and the flame holes (2
When the flame rod (23) detects that the flame formed in 1) has lifted or misfired, the detection signal is transmitted to the control device (5).
Will be applied to. Thereafter, similarly to the embodiment of the invention of claim 1, the flame hole (21) (2) is increased by increasing the rotation speed of the fan (12) or adjusting the opening degree of the gas amount adjusting valve (15).
Control is performed to maintain the excess air ratio of the gas ejected from 1) to about 1.3.

In the above embodiment, the diameter of the lower part of the specific flame hole (21) was enlarged to shorten the distance of the flame hole (21). However, the diameter of the upper part of the flame hole (21) was enlarged. Good. Further, like the embodiment of the invention of claim 1 described above, in this embodiment as well, if it is a system that can instantly determine the presence or absence of a flame, an optical sensor such as a phototransistor is used instead of the frame rod (23). Needless to say, can be used.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a first embodiment of the invention corresponding to claim 1.

FIG. 2 is an explanatory diagram of a control operation when adjusting an excess air ratio.

FIG. 3 is an explanatory diagram of a second embodiment of the invention corresponding to claim 1.

FIG. 4 is an explanatory diagram of an embodiment of the invention corresponding to claim 2;

FIG. 5 is a graph showing the relationship between the excess air ratio and the amount of generated nitrogen oxides.

FIG. 6 is a graph showing the relationship between the excess air ratio and the output of the frame rod (23).

FIG. 7 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 (2) ・ ・ ・ Burner (10) ・ ・ ・ Gas circuit (12) ・ ・ ・ Fan (15) ・ ・ ・ Gas amount control valve (21) ・ ・ ・ Flame hole

[Procedure amendment]

[Submission date] September 29, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 7

[Correction method] Change

[Correction content]

[Figure 7]

Claims (2)

[Claims] 1. A burner having a plurality of flame holes (21) (21)
(2), a fan (12) for supplying the burner (2) with all the amount of air required for combustion as primary air, and a gas amount adjusting valve (10) inserted in the gas circuit (10) to the burner (2). 15) and then
A flame monitoring sensor such as a frame rod disposed near the flame hole is provided, and the opening of the gas amount regulating valve (15) and the rotation speed of the fan (12) are controlled by the signal of the flame monitoring sensor. In the combustion control method for gas appliances, which controls the excess air ratio, thereby suppressing the amount of nitrogen oxides contained in the combustion exhaust gas, the flame hole (21) corresponding to the flame monitoring sensor.
Set the excess air ratio of the gas ejected from the gas slightly higher than the excess air ratio of the gas ejected from the other flame holes (21) (21), and increase the excess air ratio until the flame monitoring sensor gives a misfire signal. Combustion control method for gas appliances. 2. A burner having a plurality of flame holes (21) (21)
(2), a fan (12) for supplying the burner (2) with all the amount of air required for combustion as primary air, and a gas amount adjusting valve (10) inserted in the gas circuit (10) to the burner (2). 15) and then
A flame monitoring sensor such as a frame rod disposed near the flame hole is provided, and the opening of the gas amount regulating valve (15) and the rotation speed of the fan (12) are controlled by the signal of the flame monitoring sensor. In the combustion control method for gas appliances, which controls the excess air ratio, thereby suppressing the amount of nitrogen oxides contained in the combustion exhaust gas, the flame hole (21) corresponding to the flame monitoring sensor.
The gas ejection rate from the gas is set to be slightly higher than the ejection rate of the gas ejected from other flame holes (21) (21), and the excess air ratio is increased until the flame monitoring sensor outputs a misfire signal. Combustion control method for appliances.