JPH06193867A - Safety device for combustion - Google Patents

Abstract

PURPOSE:To permit the detection of imperfect combustion surely even when the imperfect combustion is caused due to either the faulty supply or discharge of air for a burner or the lack of oxygen in a room. CONSTITUTION:A porous plate 4 is provided in a tubular body 2 and total primary combustion is effected on the plate surrounded by a tubular guard 6 while the condition of the flame of the combustion is detected by a thermocouple 9. In this case, the flame is lifted sensitively even under the condition of faulty supply or discharge of air or the lack of oxygen and the electromotive force of the thermocouple 9 is changed whereby imperfect combustion can be detected surely.

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. 10, an inner cylinder 51 to which a mixed gas is supplied is provided in an outer cylinder 50, and Bunsen combustion is performed at each opening, and a primary air port 52 and an auxiliary air port 53 are used. When the oxygen concentration of the incoming air drops,
Since the Bunsen flame on the inner cylinder 51 side is lifted, the electromotive force of the thermocouple 54 is lowered due to this lift phenomenon, thereby closing the gas flow path. In the latter case, combustion exhaust that cannot be exhausted due to exhaust system failure such as fin blockage is introduced into the air port to lower the oxygen concentration in the combustion air and lift the Bunsen flame to detect abnormalities. is doing.

[0004]

However, even if these safety devices are incorporated in a combustion device forcibly taking in combustion air by a fan, incomplete combustion due to oxygen deficiency in the room can be detected, but the supply / exhaust path is blocked. There was a problem that the incomplete combustion due to the decrease in air volume due to the deterioration of the fan capacity and fan could not be detected. The reason will be described.
The flame formation position is determined by the balance between the combustion speed and the gas ejection speed. On the other hand, the combustion speed 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, it spreads not only vertically but also laterally and diagonally, so 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 state of the flame, incomplete combustion due to a decrease in the air volume cannot be prevented. An object of the combustion safety device of the present invention is to solve the above-mentioned problems and to reliably detect incomplete combustion regardless of oxygen deficiency in the room or a decrease in air flow due to poor supply and exhaust.

[0005]

SUMMARY OF THE INVENTION A combustion safety device of the present invention is a safety device incorporated in a combustor for forcibly taking in combustion air and burning it, in which a porous plate is used as a flame port forming surface. A summary is provided with a mixing burner, a cylindrical guard that surrounds the flame mouth forming surface and prevents contact of secondary air of a flame, and a flame detection element that outputs a detection signal according to the formation position of the flame. To do.

[0006]

In the combustion safety device of the present invention having the above-mentioned structure, the flame formed on the porous plate is prevented from coming into contact with the secondary air by the cylindrical guard, and all the primary combustion is carried out to form the flame. The flame detection element outputs a detection signal corresponding to the position. 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 changes. In this case, since all primary combustion is performed, the flame state changes only in the fuel injection direction, and the flame formation position changes greatly. Further, it is not affected by the flow velocity of the secondary air. As a result, the flame formation position changes sensitively to changes in the amount of combustion air, which changes the output of the flame detection element and detects an abnormality. In addition, when the room is in an oxygen-deficient state, the combustion rate decreases and flame formation occurs because the amount of oxygen that contributes to combustion is substantially reduced even when the air ratio of the premix burner is constant. The position changes. As a result, incomplete combustion can be reliably prevented based on the output of the flame detection element.

[0007]

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. A premix burner 5 with a porous plate 4 (a ceramic plate is used in the present embodiment) which is mounted in the middle of the body 2 and forms a plurality of flame ports 3
In addition to the above, the upper part (above the ceramic plate) of the tubular body 2 serves as a tubular guard 6 that prevents contact of secondary air. Specifically, the gas nozzle 20 is made to face the lower opening 7 of the cylindrical body 2 to form the mixing chamber 8 up to the porous plate 4, and the lower opening is set so that the air ratio in the mixing chamber 8 is 0.9 at the normal time. The opening of the section 7 is set. 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.

The air-fuel mixture mixed in the mixing chamber 8 is ejected from each flame port 3 of the porous plate 4 and is transferred from the main burner (shown in FIG. 9) of the water heater to form a flame on the plate surface. To do. In this case, the supply of secondary air is blocked by the tubular guard 6 surrounding the flame, and all primary combustion is performed. A thermocouple 9 is attached to the tubular guard 6 from the lateral direction, and its heat receiving portion 9a is positioned inside the flame. The thermocouple 9 is connected to a combustion controller (not shown) of the water heater, and is configured to open and close an electromagnetic valve provided in the gas flow path of the main burner according to the electromotive force of the thermocouple 9. That is, when the electromotive force of the thermocouple 9 becomes equal to or lower than a predetermined level, the gas flow passage is closed. The electromagnetism of the thermocouple 9 may adsorb and hold the magnet safety valve to keep the gas flow path open.

When the air volume of the combustion air decreases due to the fin clogging of a heat exchanger (not shown) or the reduction of the fan capacity for sending the combustion air into the combustion chamber, the air ratio in the mixing chamber 8 decreases and the combustion speed decreases. To do. Therefore, the flame formed on the porous plate 4 is lifted, and finally the flame is formed at the tip end opening of the tubular guard 6 as shown in FIG. That is, during the entire primary combustion, the flame sensitively lifts with respect to the reduction of the air volume (the reduction of the air ratio), and when it reaches the tip opening of the tubular guard 6, the secondary air is supplied from around it and the Bunsen combustion is performed. Is done. Further, during Bunsen combustion, since the combustion is diffusion combustion and the force for lifting the flame upward due to the decrease in air volume is reduced, the air hardly lifts with respect to the change in air volume.

When the air volume decreases in this way, the electromotive force of the thermocouple 9 sharply decreases as shown in FIG. This characteristic diagram was obtained by experiment, the horizontal axis is the air ratio λ of the main burner of the water heater, the solid line is the electromotive force (mV) of the thermocouple,
The broken line represents the carbon monoxide concentration (ppm) in the equipment exhaust. As can be seen from the characteristic diagram, the electromotive force of the thermocouple 9 rapidly decreases as the air ratio decreases. Therefore, the electromotive force of the thermocouple 9 becomes less than or equal to the set value before the carbon monoxide concentration becomes high, and the gas flow path can be closed.

Next, the operation of preventing incomplete combustion due to a decrease in the oxygen concentration in the room will be described. 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, as shown in FIG. 4, the flame during the entire primary combustion starts to lift, and after reaching the opening at the tip of the tubular guard 6, misfire occurs. FIG. 5 shows the characteristics of the electromotive force of the thermocouple 9 and the carbon monoxide concentration in the equipment exhaust in this case. This characteristic diagram was obtained by an experiment, and the horizontal axis represents the oxygen concentration (%). As can be seen from the characteristic diagram, the carbon monoxide concentration sharply rises when the indoor oxygen concentration falls to 18.5% or less, while the electromotive force of the thermocouple 9 decreases linearly with the oxygen concentration reduction. To do. Therefore, since the electromotive force of the thermocouple 9 has sufficiently decreased by the time the carbon monoxide concentration rises, it is possible to reliably close the gas passage at a safe level.

Next, a modification of the mounting position of the thermocouple 9 will be described. In the previous embodiment, the thermocouple 9 is replaced by the tubular guard 6.
6A, the porous plate 4 is penetrated into the heat receiving portion 9a so that the heat receiving portion 9a is located in the flame as shown in FIG. 6A, or the heat receiving portion 9a is shown in FIG. 6B. May be embedded in the porous plate 4 to detect the plate temperature of red heat. Further, as shown in FIG. 6C, the structure may be provided on the tip end opening of the tubular guard 6 to generate an electromotive force at the time of lifting.

Various shapes of the premix burner 5 can be considered. For example, as shown in FIG. 7, a U-shaped throat 11 may be relayed and arranged laterally to prevent clogging of falling objects due to drainage from the heat exchanger. Further, as shown in FIG. 8, the throat 12 formed in a V shape may be relayed and arranged to be inclined, and the falling object prevention plate 13 may be provided at the tip of the tubular guard 6. The fallen object prevention plate 13 also acts as a fire transfer plate that assists the transfer of fire from the main burner.

Next, an example of a construction in which the combustion safety device 1 is incorporated in a gas water heater will be shown. FIG. 9 is a schematic configuration view 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 9
Although the gas flow passage is closed when the electromotive force is reduced to a predetermined value or less, the rotation speed of the fan may be adjusted before closing the gas flow passage. 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 9 is reduced to a preset level and the electromotive force is not recovered even when the rotational speed of the fan is increased and the rotational speed reaches a predetermined rotational speed, 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 9 is always a constant value. That is, the rotational speed of the fan is controlled by using the electromotive force of the thermocouple 9 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 9 is possible because the combustion safety device 1 very sensitively detects the air volume shortage and the oxygen deficiency state (see the characteristic diagram of the figure), and the control of the Bunsen combustion like the conventional one is possible. With lift detection, it is impossible to obtain accurate control. At the start of combustion, the control operation is not performed until the electromotive force of the thermocouple 9 stabilizes.

The embodiment of the present invention has been described above.
The present invention is not limited to these examples, and for example, an element such as a flame rod for detecting a flame current may be used instead of the thermocouple 1, and various elements may be used without departing from the gist of the present invention. Of course, it can be carried out in other modes. Further, the present invention can be applied not only to a water heater but also to a combustor such as a fan heater. Furthermore, even in an external type device in which oxygen deficiency is not a concern, it can be used as a sensor for detecting a decrease in air volume.

[0019]

As described above in detail, according to the combustion safety device of the present invention, incomplete combustion can be reliably detected even if the air supply / exhaust of the combustor is poor or the oxygen deficiency in the room is insufficient. It has an excellent effect that it can be done.

[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 state of a flame when the air volume decreases.

FIG. 3 is a graph showing electromotive force and CO concentration characteristics of a thermocouple with respect to changes in air ratio.

FIG. 4 is an explanatory diagram showing a state of a flame at the time of lack of oxygen.

FIG. 5: Electromotive force of a thermocouple, CO with respect to changes in oxygen concentration
It is a graph showing a density characteristic.

FIG. 6 is a schematic configuration diagram showing a modified example of a mounting position of a thermocouple.

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

FIG. 8 is a schematic configuration diagram of a combustion safety device according to another embodiment.

FIG. 9 is an explanatory diagram showing a combustion chamber in a state in which a combustion safety device is incorporated in a gas water heater.

FIG. 10 is a schematic configuration diagram of a conventional combustion safety device.

[Explanation of symbols]

1 ... Combustion safety device, 4 ... Porous plate, 5 ... Premix burner, 6 ... Cylindrical guard, 9 ... Thermocouple.

Claims (1)

[Claims] 1. A safety device incorporated in a combustor for forcibly taking in combustion air for combustion, comprising a premixing burner having a porous plate as a flame port forming surface, and surrounding the flame port forming surface. A combustion safety device comprising a tubular guard that prevents contact of secondary air of a flame, and a flame detection element that outputs a detection signal according to the formation position of the flame.