JPH074641A - Combustion safety device - Google Patents

Abstract

PURPOSE:To accurately detect incomplete combustion by stabilizing an output of a thermocouple until a cylindrical guard opening is flame stabilized from when a flame starts to be lifted due to lack of air flow rate (or oxygen deficiency). CONSTITUTION:A burner plate 5 is surrounded around it by a cylindrical guard 7, entirely primarily burned on the plate 5, and a state of this flame is detected by a thermocouple 10. A distributing plate 3 for enhancing a pressure distribution along an outer periphery of the plate 5 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a safety device for preventing incomplete combustion of a combustor (for example, forced exhaust type combustor) which compulsorily takes in combustion air and burns it.

[0002]

2. Description of the Related Art Incomplete combustion, which is a cause of carbon monoxide poisoning, is caused mainly by two factors: defective supply / exhaust system of the combustor and indoor oxygen deficiency due to exhaust leakage. Therefore, conventionally, the combustor is provided with a safety device that detects incomplete combustion and stops the combustion. The technology of such a safety device is disclosed in, for example, Japanese Patent Publication No. 59-39647 and Japanese Patent Publication No. 61-3.
1768 and the like.

In the former case, as shown in FIG. 9, an inner cylinder 51 to which a mixed gas is supplied is provided in an outer cylinder 50, Bunsen combustion is performed at each opening, and a primary air port 52 and an auxiliary air port 53 are used. Since the Bunsen flame on the inner cylinder 51 side lifts when the oxygen concentration of the inflowing air decreases, the electromotive force of the thermocouple 54 due to this lift phenomenon lowers the gas flow path. In the latter case, the combustion exhaust gas that cannot be exhausted due to a defective exhaust system such as fin blockage is introduced into the air port to reduce the oxygen concentration of the combustion air,
An abnormality is detected by lifting the Bunsen flame. still,
The Bunsen combustion used here is in contrast to the entire primary combustion, and means combustion in which secondary air is taken in from the surroundings to form a flame.

However, even if these safety devices are incorporated into a combustion device for forcibly taking in the combustion air by a fan, incomplete combustion due to oxygen deficiency in the room can be detected, but due to blockage of the air supply / exhaust path and deterioration of fan performance. There was a problem that incomplete combustion due to the decrease in air volume could not be detected. The reason will be described. The flame formation position is
It is determined by the balance between the combustion speed and the gas ejection speed. on the other hand,
The burning rate is determined by the air ratio (the ratio of the actual air amount to the theoretical air amount). Therefore, when the amount of air supplied from the fan decreases, the air ratio of the air-fuel mixture supplied to the safety device also decreases, and the combustion speed decreases. Therefore,
The flame should lift, but in the case of Bunsen combustion, since it is diffusion combustion, not only in the vertical direction but also in the horizontal direction,
Since it spreads in an oblique direction, it does not lift sensitively to a decrease in the air ratio. Moreover, the flow velocity of the secondary air is also reduced, which rather acts to suppress the lift. As a result, even if the thermocouple detects the flame condition,
Incomplete combustion due to the reduction in air volume cannot be prevented.

Therefore, the applicant of the present application has previously proposed a combustion safety device capable of reliably detecting incomplete combustion even when the oxygen deficiency in the room is low or the air flow rate is reduced due to poor supply / exhaust (Japanese Patent Application No. 2003-242242). Flat 4-358213). In this technique, as shown in FIG. 10, the burner plate P is surrounded by a tubular guard G to prevent contact of secondary air in the flame to perform primary combustion, and the flame formation position at this time is determined by a thermocouple TC. It is something to detect. According to this safety device, the flame formation position is sensitively changed (lifted) to the incomplete combustion regardless of the fluctuation of the combustion air amount and the oxygen deficiency in the room without being affected by the secondary air. It was a very good thing that could be reliably prevented.

[0006]

However, in this combustion safety device, when the combustion device starts incomplete combustion due to insufficient air flow or lack of oxygen, the flame starts to lift from the burner plate P and reaches a predetermined combustion level. The flame is held at the open end of the cylindrical guard G, but at a weak incomplete combustion level until the flame reaches the open end of the cylindrical guard G, the thermocouple TC
Output is likely to be unstable.

The state of the flame and the output of the thermocouple TC with the progress of incomplete combustion will be described with reference to FIG. During the complete combustion, as shown in FIG.
The flame is held by the burner plate P and the output of the thermocouple TC is stable. And when the air volume shortage and oxygen deficiency begin,
As shown in (a) in the figure, first, the flame in the central portion of the burner plate P begins to lift, but in this state, the thermocouple TC
The output is stable because is heated by the external flame. However, when the incomplete combustion progresses a little further, as shown in FIG. 5C, a part of the flame on the outer peripheral portion of the burner plate P is connected to the central flame and lifted. At this time, the flame held in the burner plate P and the lifted flame are mixed, and the flame moves to heat the thermocouple TC with an external flame or an internal flame. Therefore, the output of the thermocouple TC becomes unstable. Further progressing, as shown in (d) of the same figure, although most of the flame is lifted, a part of the flame is held on the burner plate P, and the output of the thermocouple TC becomes unstable. Not only that, but it also varies greatly depending on the flame holding position. For example, in the case where the flame is held by the burner plate P on the thermocouple TC side as shown by the broken line in (d) of the figure, and when the flame is held by the side opposite to the thermocouple TC as shown by the solid line. The output is quite different.

After that, a predetermined air volume shortage (or oxygen deficiency)
When the level is reached, the flame is completely lifted from the burner plate P and held at the tip of the tubular guard G, and the output of the thermocouple TC stabilizes at a low value, as shown in FIG.
When the flame is held at the tip of the tubular guard G, the secondary air is taken in from the surroundings to switch to Bunsen combustion and the flame becomes stable.

Therefore, although incomplete combustion can be finally detected, the output of the thermocouple TC tends to become unstable during the detection, and there remains a problem in forming a combustion sequence using this output. An object of the combustion safety device of the present invention is to solve the above problems and to stabilize the output of a thermocouple to detect incomplete combustion with high accuracy.

[0010]

In order to solve the above problems, the first combustion safety device of the present invention is a safety device incorporated in a combustor for forcibly taking in combustion air and burning it. A premix burner having a burner plate having a flame port, a cylindrical guard surrounding the burner plate to prevent contact of secondary air of the flame, and a cylindrical guard inserted through the wall surface of the cylindrical guard depending on the flame formation position. And a thermocouple for outputting the detection signal, and a pressure adjusting means for increasing the pressure distribution of the air-fuel mixture toward the thermocouple.

A second combustion safety device according to the present invention is the first combustion safety device according to the first combustion safety device, wherein the thermocouple is disposed above the outer peripheral portion of the burner plate whose heat sensitive portion is surrounded by the tubular guard. It is provided that the pressure adjusting means increases the pressure distribution along the outer peripheral portion of the burner plate.

[0012]

In the combustion safety device of the present invention having the above-described structure, the flame formed on the burner plate is prevented from coming into contact with the secondary air by the cylindrical guard to carry out all primary combustion, and the flame formation position. The thermocouple outputs a detection signal corresponding to.
The formation position of this flame is determined by the balance between the combustion speed and the jet speed of the air-fuel mixture. In a normal state, a flame is formed on the burner plate, but when the amount of combustion air decreases due to a defective supply / exhaust system, the air ratio of the premix burner decreases and the combustion speed decreases. In this case, since the combustion is all primary combustion, the state of the flame changes only in the fuel injection direction, and the flame lifts sensitively. The flame is lifted more sensitively when the pressure distribution of the air-fuel mixture is higher, and conversely, the flame holding property is higher when the pressure distribution is lower. Therefore, the flame of the air-fuel mixture having a high pressure toward the thermocouple lifts earlier than the flame in the region where the pressure distribution is low, and the thermocouple is maintained in the inner flame. In other words, even when only a part of the flame is lifted and the weak air volume is insufficient, by adjusting the pressure distribution, the region where the flame is lifted and the region where the flame is not lifted are divided, and the flame in the lifted region (internal flame) Heats the thermocouple. Therefore, after that, the outer flame is less likely to come into contact with the thermocouple, and the output of the thermocouple becomes stable. When the air volume becomes insufficient, the flame held in the burner plate (flame at the position where the pressure distribution is low) is also lifted and held at the tip opening of the tubular guard. As a result, it is possible to accurately detect a state where the air volume is insufficient.

Further, when the chamber is in an oxygen-deficient state, the combustion rate decreases because the amount of oxygen contributing to combustion is substantially reduced even if the air ratio of the premix burner is constant. Similarly, the flame changes, and a stable thermocouple output change can be obtained. As a result, incomplete combustion can be detected with high accuracy.

In the second combustion safety device of the present invention,
Since the pressure distribution is increased along the outer peripheral portion of the burner plate, in addition to the above operation, the period from when the flame starts to lift to when the flame is held in the tip opening of the tubular guard is shortened. That is, the period in which the flame is likely to be unstable on the burner plate is shortened, and incomplete combustion can be detected with higher accuracy.

The pressure distribution is adjusted by changing the flow of the air-fuel mixture by providing a distribution plate or swirl vanes in the air-fuel mixture flow passage on the upstream side of the burner plate, or by making the burner plate distribution distribution of the burner plate coarse and dense. You may comprise by.

[0016]

EXAMPLES In order to further clarify the structure and operation of the present invention described above, preferred examples of the combustion safety device of the present invention will be described below. FIG. 1 shows a schematic configuration of a combustion safety device as an example. The combustion safety device 1 is provided adjacent to a main burner in a combustion chamber of a forced exhaust (FE) type gas water heater, which will be described later, and is an elbow-shaped mixing pipe in which fuel gas and combustion air are sucked and mixed. A premixing burner 6 is formed by 2 and a burner plate 5 (a ceramic plate is used in this embodiment) formed with a plurality of flame ports 4 from which the air-fuel mixture mixed in the mixing tube is ejected. Further, a cylindrical tubular guard 7 that surrounds the burner plate 5 and prevents contact of secondary air of flame formed on the plate 5 is mounted. In addition, a disk-shaped distribution plate 3 is disposed in the mixing pipe 2 at a position slightly upstream of the burner plate 5 in the central portion of the mixing pipe 2, and further upstream thereof, a throttle member 8 for collecting the air-fuel mixture in the central side. Is provided.

A gas nozzle 20 is provided at the opening 9 of the mixing tube 2.
Combustion air is also taken in at the same time when the fuel gas is ejected. The opening is set so that the air ratio in the mixing pipe 2 is 0.9 when the air ratio is normal. This mixing ratio (0.9) is set so that the combustion speed becomes maximum. That is, when the mixing ratio deviates from this value, the burning speed becomes slow. Further, as shown in FIG. 2A, the pressure distribution of the air-fuel mixture on the burner plate 5 is higher on the outer peripheral portion, that is, on the inner wall surface side of the tubular guard 7, by providing the distribution plate 3. It should be noted that FIG. 9A shows the pressure distribution when the distribution plate 3 is not provided.

The tubular guard 7 is provided with a thermocouple 10 from the lateral direction.
The heat sensitive portion 10a, which is the tip of the, is inserted. This thermocouple 1
0 is provided at a predetermined distance from the surface of the burner plate 5 so as to be heated by the outer flame of the flame in a normal state, but is located outside the cylindrical guard 7 except for the heat sensitive portion 10a of the thermocouple 10.
Secondary air that flows upwardly around the tubular guard 7 hits it directly to cool the thermocouple 10, so that the durability is improved and a large electromotive force is obtained. In addition, this thermocouple 1
0 is connected to a combustion controller (not shown) of the water heater, and is configured to control the opening / closing of the solenoid valve provided in the gas flow path of the main burner according to the electromotive force of the thermocouple 10. That is, when the electromotive force of the thermocouple 10 falls below a predetermined level, the gas flow passage is closed. The electromagnetism of the thermocouple 10 may adsorb and hold the magnet safety valve to keep the gas flow path open.

The air-fuel mixture mixed and regulated in the mixing pipe 2 is ejected from each flame port 4 of the burner plate 5 and is transferred from the main burner (shown in FIG. 8) of the water heater to the surface of the plate 5. Form a flame. In this case, the supply of the secondary air is blocked by the tubular guard 7 surrounding the flame, and the entire primary combustion is performed.

When the air volume of the combustion air decreases due to the fin closure of a heat exchanger (not shown) or the reduction of the fan capacity for sending the combustion air into the combustion chamber, the state shown in FIG. As shown in, the flame on the outer peripheral portion of the burner plate 5 begins to lift a little. This is because the pressure distribution in the outer peripheral portion is high. In this state, since the thermocouple 10 is still heated by the external flame, the output has a stable and high value.

When the amount of air flow further decreases, the flame on the outer peripheral portion of the burner plate 5 lifts significantly as shown in FIG. 3C, and the thermocouple 10 (heat sensitive portion 10a) is settled in the flame. In this case, the central portion of the burner plate 5 is flame-held by adjusting the pressure distribution. That is, it is divided into a lift region in the outer peripheral portion and a flame holding region in the central portion. Therefore, the thermocouple 10 is maintained in the lift region and the surrounding flame is stable, so that the output of the thermocouple 10 is also stable.

When the air volume further decreases, the flame at the center of the burner plate 5 also begins to lift, as shown in FIG. Even in this case, a flame holding flame is seen in the burner plate 5, but the flame holding position is limited to the vicinity of the center of the burner plate 5 and is wide in the range as in the previous application (shown in FIG. 11D). I won't. Therefore, regardless of the position of the flame, the thermocouple 10 is always contained in the inner flame and the output is stable. That is, the flame may have a shape shown by a broken line or a shape shown by a solid line in the figure, but in any case, since the flame holding position is near the center, the thermocouple 10 is contained in the inner flame.

In this way, when the air volume becomes insufficient at a predetermined level, the flame is burned by the burner plate 5 as shown in FIG.
To completely hold the flame in the opening of the tubular guard 7. When this happens, secondary air is supplied from the surroundings, and the Bunsen combustion is switched to. At the time of Bunsen combustion, since it is diffusion combustion and the force for lifting the flame upward due to the decrease in the air volume is reduced, it hardly lifts with respect to the change in the air volume.

FIG. 4 shows the thermocouple 10 for the air ratio λ of the main burner when the combustion safety device is incorporated in the water heater.
Represents the electromotive force and the carbon monoxide concentration. As mentioned above, when the air ratio decreases, the electromotive force of the thermocouple 10 decreases sharply,
Before the carbon monoxide concentration becomes high, it becomes less than the set value and the gas passage can be closed. Moreover, since the output of the thermocouple 10 is more stable than that of the previous application during the flame lift from the point A to the point B, the incomplete combustion determination level (threshold value) is arbitrarily set. be able to. Further, since the pressure distribution on the outer peripheral portion of the burner plate 5 is made high, the flame is easily held at the tip of the tubular guard 7, and the intermediate lift period (point A to point B) is shortened. For this reason, the output characteristic of the thermocouple 10 with respect to the air ratio becomes steep, and it is possible to accurately grasp the state where the air volume is insufficient.

On the other hand, when the oxygen concentration in the room decreases, the combustion speed becomes slow because the amount of oxygen contributing to combustion decreases even if the air volume (air ratio) is the same. As a result, the flame is lifted sensitively as described above. As a result, the electromotive force of the thermocouple 10 is sufficiently reduced before the carbon monoxide concentration rises, and the gas flow path can be closed reliably at a safe level. In the case of oxygen deficiency, the flame is retained by the tubular guard 7, and then the flame is misfired earlier.

Next, another embodiment of the combustion safety device will be described. In the combustion safety device shown in FIG. 5, a swirl vane 3a is fixed in the mixing pipe 2 instead of the distribution plate 3 and the throttle member 8 shown in the previous embodiment. Therefore, the air-fuel mixture that has passed through the swirl vanes 3a swirls as shown by the dashed arrow, and the pressure distribution on the outer peripheral portion of the burner plate 5 becomes high.

Further, in the combustion safety device shown in FIG. 6, without adjusting the pressure distribution in the mixing tube 2, the arrangement of the flame ports 4 formed in the burner plate 5 is roughly arranged in the central part and densely in the outer peripheral part. By doing so, the pressure distribution on the inner wall surface side of the tubular guard 7 on which the thermocouple 10 is provided is increased.

In the combustion safety device shown in FIG. 7, a thermocouple 1 is used instead of the distribution plate 3 and the throttle member 8 shown in the previous embodiment.
A diaphragm member 3b having an opening is provided directly below the 0 tip. Therefore, the pressure distribution of the air-fuel mixture toward the thermocouple 10 becomes high.

Next, an example of a construction in which the combustion safety device 1 is incorporated in a gas water heater will be shown. FIG. 8 is a schematic configuration diagram of the inside of the combustion chamber 30 of the FE type gas water heater viewed from above. A plurality of flat main burners 31 are arranged in parallel in the combustion chamber 30, a damper 33 for adjusting the primary air amount is provided at the tip of the throat 32, and fuel gas is supplied from each gas nozzle 35 provided in the nozzle base 34. Is supplied. This nozzle stand 3
A proportional control valve for adjusting the capacity (combustion amount) and a solenoid valve (not shown) for opening and closing the gas passage are provided in the gas passage to 4. A sirocco fan (not shown) is provided below the combustion chamber 30. Combustion air is supplied to the combustion chamber 30 to perform Bunsen combustion in the main burner 31, and a heat exchanger (not shown) is generated by the combustion heat. It is configured to be heated and discharged.

The combustion safety device 1 includes the main burner 31.
Gas nozzles 3 installed in parallel on the common nozzle base 34
Fuel gas is supplied from 6. Therefore, the structure is simple without providing a separate gas flow path. Further, although the setting of the air ratio of the main burner 31 is different between the case where the capacity is large and the case where the capacity is small, the air ratio is also changed in the combustion safety device 1 accordingly, and the actual combustion state of the main burner 31 is changed. Incomplete combustion detection can be performed.

In the embodiment described above, the thermocouple 1
Although the gas flow path is closed when the electromotive force of 0 decreases below a predetermined value, the rotation speed of the fan may be adjusted before closing the gas flow path. In other words, when the air ratio decreases due to back wind from an exhaust duct (not shown), fin blocking, or the like, there are cases where the combustor can be used without stopping by increasing the rotation speed of the fan. Therefore, when the electromotive force of the thermocouple 10 is reduced to a preset level, the rotation speed of the fan is increased and the electromotive force cannot be recovered even when the predetermined rotation speed is reached, that is, the air ratio is When it does not increase, the gas flow path is closed and the device is stopped. Further, the gas flow path may be closed when the electromotive force does not recover even after a lapse of a predetermined period after increasing the rotation speed of the fan.

Further, the fan speed may be controlled so that the electromotive force of the thermocouple 10 is always a constant value. That is, the rotational speed of the fan is controlled by using the electromotive force of the thermocouple 10 as a feedback control factor. In this case, when the rotation speed of the fan does not fall within the predetermined range, the gas passage is closed to prevent incomplete combustion. The control based on the electromotive force of the thermocouple 10 is possible because the combustion safety device 1 detects the air volume shortage and the oxygen deficiency with high accuracy, and the conventional Bunsen combustion lift detection has high accuracy. It is impossible to ask for. At the start of combustion, thermocouple 1
The control operation is not performed until the electromotive force of 0 is stabilized.

The embodiment of the present invention has been described above.
The present invention is not limited to these examples, and it goes without saying that the present invention can be implemented in various modes without departing from the gist of the present invention. For example, the invention can be applied not only to a water heater but also to a combustor such as a fan heater. Also,
It can be used as a sensor for detecting a decrease in air volume even in an external type device in which oxygen deficiency is not a concern.

[0034]

As described in detail above, according to the combustion safety device of the present invention, since the pressure distribution of the air-fuel mixture toward the thermocouple is increased, the output of the thermocouple becomes very stable,
It has an excellent effect that the incomplete combustion can be detected with high accuracy.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a combustion safety device as one embodiment.

FIG. 2 is an explanatory diagram showing a pressure distribution of a combustion safety device.

FIG. 3 is an explanatory diagram showing the state of flame and the output of a thermocouple when the air volume decreases.

FIG. 4 is a graph showing electromotive force and CO concentration characteristics of a thermocouple with respect to changes in air ratio.

FIG. 5 is a schematic configuration diagram of a combustion safety device as another embodiment.

FIG. 6 is a schematic configuration diagram of a combustion safety device as another embodiment.

FIG. 7 is a schematic configuration diagram of a combustion safety device as another embodiment.

FIG. 8 is an explanatory view showing a combustion chamber in which a combustion safety device is incorporated in a gas water heater.

FIG. 9 is a schematic configuration diagram of a conventional combustion safety device.

FIG. 10 is a schematic configuration diagram of the previously proposed combustion safety device.

FIG. 11 is an explanatory diagram showing the state of flame and the output of a thermocouple when the air flow rate of the previously proposed combustion safety device is decreased.

[Explanation of symbols]

1 ... Combustion safety device, 3 ... Distribution plate, 3a ... Swirl blade,
3b ... diaphragm member, 4 ... flame port, 5 ... burner plate,
6 ... Premix burner, 7 ... Cylindrical guard, 10 ... Thermocouple, 10a ... Heat sensitive part.

Claims (2)

[Claims] 1. A safety device incorporated in a combustor for forcibly taking in combustion air for combustion, comprising a premix burner having a burner plate having a plurality of flame openings, and a flame surrounding the burner plate. And a thermocouple that outputs a detection signal according to the flame formation position, which is inserted into the wall surface of the tubular guard, and the pressure of the air-fuel mixture that goes toward the thermocouple. A combustion safety device comprising a pressure adjusting means for increasing the distribution. 2. The thermocouple is disposed above the outer peripheral portion of the burner plate whose heat sensitive portion is surrounded by the tubular guard, and the pressure adjusting means distributes pressure along the outer peripheral portion of the burner plate. The height is set high.
Combustion safety device as described.