JPH06331134A - Combustion safety device - Google Patents

Abstract

PURPOSE:To perform a fast sensing of not only a lack of oxygen in a room but also a reduction in an amount of air in particular and to surely prevent incomplete combustion. CONSTITUTION:Burner plates 4 are installed within a cylinder 2. A full primary combustion is carried out on the plates enclosed by a cylinder guard 6. A state of flame is sensed by a thermocouple 9. In this case, pressure of mixture gas is adjusted by a pressure adjusting chamber 8 and at the same time a degree of mixing is made superior to suppress flatter of the flame to be restricted and then a sensing characteristic is improved.

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. 7, 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 exhaust system failure such as fin blockage is introduced into the air port to lower the oxygen concentration of the combustion air,
An abnormality is detected by lifting the Bunsen 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. 8, the burner plate P is surrounded by a tubular guard G to prevent contact of secondary air in the flame to perform all 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 regardless of the fluctuation of the combustion air amount and the oxygen deficiency in the room without being affected by the secondary air, and the incomplete combustion is reliably prevented. It was possible and very good.

[0006]

However, in this combustion safety device, the concentration and pressure distribution of the air-fuel mixture ejected from each flame port H of the burner plate P are likely to be non-uniform. Therefore, when the air volume of the fan decreases, a high air ratio portion and a low air ratio portion are formed on the burner plate P,
Before the flame is completely lifted from the cylinder guard G, the guard G
I'm fluttering inside. As a result, the output of the thermocouple becomes unstable. In other words, as a safety device, when the air volume (air ratio) decreases, we want to quickly lift the flame to obtain a large change in the electromotive force of the thermocouple, but due to the non-uniform air ratio, the flame flaps and does not lift sensitively. Therefore, the change in electromotive force of the thermocouple becomes gradual and the abnormality cannot be caught quickly. An object of the combustion safety device of the present invention is to solve the above-mentioned problems and to prevent not only oxygen deficiency in a room but also to detect a decrease in air volume quickly to reliably prevent incomplete combustion.

[0007]

In order to solve the above problems, a combustion safety device of the present invention is a safety device incorporated in a combustor which compulsorily takes in combustion air and burns it. A premixed burner having a burner plate formed with, a cylindrical guard surrounding the burner plate to prevent contact of secondary air of the flame, and a detection signal corresponding to the position of the flame formed in the cylindrical guard. With a thermocouple to output, the air-fuel mixture flow path of the premix burner,
A first mixing flow path through which the fuel gas and the combustion air are sucked,
The gist of the present invention is to provide a second mixing flow passage having a diameter larger than that of the first mixing flow passage and changing the direction of the mixed air flow from the first mixing flow passage to send the mixture to the flame port of the burner plate.

[0008]

In the combustion safety device of the present invention having the above structure, the fuel gas and the combustion air are sucked and mixed in the first mixing passage of the premixing burner, and then the first mixing passage having a diameter larger than that of the first mixing passage. 2 The mixture is sent to the mixing channel and the direction of the mixture is changed, and the mixture is ejected from the flame port of the burner plate. The air-fuel mixture is mixed in the first mixing flow passage, but when it is sent to the second mixing flow passage, the flow passage has a large diameter, so that the pressure is suddenly reduced and entrained to promote mixing. Moreover, since the direction of the mixed air flow is changed,
The air-fuel mixture collides with the wall surface of the second mixing flow path, and the mixing degree is further improved. Further, since the second mixing flow path has a large diameter, the volume after mixing can be made large and the pressure distribution becomes uniform. In this way, the pressure distribution becomes uniform, and the well-mixed air-fuel mixture is ejected from the flame opening of the burner plate and ignited. When the air-fuel mixture ignites, a flame is formed on the burner plate, and this flame is blocked by the cylindrical guard from contacting with the secondary air to perform all primary combustion, and a detection signal corresponding to the flame formation position is sent to the thermocouple. Will output.

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 with respect to changes in the combustion air amount. 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, a sufficient change in electromotive force of the thermocouple can be obtained, and incomplete combustion can be reliably detected.

[0010]

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 the main burner in a combustion chamber of a forced exhaust (FE) type gas water heater, which will be described later. The combustion safety device 1 is arranged vertically and has a closed lower end (a cylindrical body 2). Of the cylindrical body 2), a burner plate 4 (a ceramic plate is used in the present embodiment) which is installed in the middle of the cylindrical body 2 to form a plurality of flame ports 3, and a cylindrical body 2 A premixing burner 5 is constituted by a narrow mixing portion 10 (first mixing flow passage of the present invention) which is connected to the side wall and in which the fuel gas and the combustion air are sucked from the lateral direction, and at the same time, the upper portion of the cylindrical body 2 (burner). The upper part (above the plate 4) serves as a cylindrical guard 6 which prevents the contact of the secondary air. Further, the inside of the cylindrical body 4 below the burner plate 4 is a pressure adjusting chamber (second mixing flow passage of the present invention) 8. Also,
The gas nozzle 20 is made to face the opening 7 of the mixing section 10 to eject the fuel gas, and the combustion air is sucked accordingly. The opening of the opening 7 is set so that the air ratio in the mixing unit 10 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.

In the mixing section 10, the sucked fuel gas and the combustion air pass through a narrow flow path and are mixed well and are sent to the pressure adjusting chamber 8. The pressure adjusting chamber 8 has a larger diameter than the mixing unit 10, and the flow directions of the air-fuel mixture are orthogonal to each other. Therefore, the air-fuel mixture sent from the mixing section 10 is suddenly depressurized when it enters the pressure regulating chamber 8 and is entrained, and the air-fuel mixture collides with the wall surface of the pressure regulating chamber 8 to promote mixing. Further, since the pressure adjusting chamber 8 has a large diameter and a large volume, the pressure distribution of the air-fuel mixture becomes uniform.

When the concentration and pressure are made uniform in this way and the air-fuel mixture is ejected from each flame port 3 of the burner plate 4, the flame is transferred from the main burner (shown in FIG. 6) 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 heat sensitive portion 9a, which is the tip of the thermocouple 9, is inserted into the tubular guard 6 from the lateral direction. Further, the thermocouple 9 is located outside the tubular guard 6 except for the heat sensitive portion 9a,
Secondary air that flows upwardly around the tubular guard 6 is directly hit to cool the thermocouple 9. That is, the thermal deterioration of the thermocouple is reduced. The thermocouple 9 is connected to a combustion controller (not shown) of the water heater, and is configured to open and close the solenoid valve provided in the gas flow path of the main burner according to the electromotive force of the thermocouple 9. There is.
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. Also, thermocouple 9
The magnet safety valve may be adsorbed and held by the electromotive force to maintain the gas flow path in the open state.

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 pressure adjusting chamber 8 decreases and the combustion speed increases. descend. For this reason, the flame formed on the burner plate 4 is lifted, and finally the flame is formed at the tip 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, an example of a structure in which the combustion safety device 1 is incorporated in a gas water heater will be shown. FIG. 6 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 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, the rotational speed of the fan is increased and the electromotive force is not recovered even when 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 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.

[0021]

As described above in detail, according to the combustion safety device of the present invention, not only oxygen deficiency in the room, but especially a decrease in the air flow rate can be quickly detected to reliably prevent incomplete combustion.

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

FIG. 7 is a schematic configuration diagram of a conventional combustion safety device.

FIG. 8 is a schematic configuration diagram of the previously proposed combustion safety device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Combustion safety device, 4 ... Burner plate, 5 ... Premix burner, 6 ... Cylindrical guard, 9 ... Thermocouple, 8 ... Pressure regulation chamber (2nd mixing flow path), 10 ... Mixing part (1st mixing flow) Road).

Claims (1)

[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. With a tubular guard that prevents the contact of the secondary air, and a thermocouple that outputs a detection signal according to the position of the flame formed in the tubular guard, the air-fuel mixture flow path of the premix burner, A first mixing flow passage through which the fuel gas and the combustion air are sucked, and a mixture air flow having a diameter larger than that of the first mixing flow passage and changing the direction of the mixed air flow from the first mixing flow passage to burn the air-fuel mixture in the flame of the burner plate. A combustion safety device, comprising: a second mixing flow path that is sent to the mouth.