JP3117582B2 - Combustion safety device - Google Patents

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, a forced exhaust combustor) forcibly taking in combustion air and burning.

[0002]

2. Description of the Related Art Incomplete combustion, which is a cause of carbon monoxide poisoning, is mainly caused by two factors: a defective supply / exhaust system of a combustor and a state of lack of oxygen in a room due to leakage of exhaust gas. Therefore, a safety device is conventionally provided in the combustor to detect incomplete combustion and stop 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. Sho 61-3.
No. 1768.

In the former, as shown in FIG. 8, an inner cylinder 51 to which a mixed gas is supplied is provided in an outer cylinder 50, and Bunsen combustion is performed in each opening, and a primary air port 52 and an auxiliary air port 53 are provided. When the oxygen concentration of the inflowing air decreases, the Bunsen flame on the side of the inner cylinder 51 lifts, so that the gas flow path is closed by a decrease in the electromotive force of the thermocouple 54 due to the lift phenomenon. Further, the latter reduces the oxygen concentration of the combustion air by introducing combustion exhaust that cannot be exhausted due to exhaust system failure such as fin blockage into the air port,
An abnormality is detected by lifting the Bunsen flame. still,
The Bunsen combustion used here is compared with the all primary combustion, and means combustion in which secondary air is taken in from the surroundings to form a flame.

[0004] However, even if these safety devices are incorporated in a combustion device that forcibly takes in combustion air by a fan, incomplete combustion due to lack of oxygen in the room can be detected, but due to blockage of the supply / exhaust path and deterioration of the capacity of the fan. There has been a problem that incomplete combustion due to a decrease in air flow cannot be detected. The reason will be described. The formation position of the flame
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, because it is diffusion combustion, not only in the vertical direction but also in the horizontal direction,
Because it spreads diagonally, it does not lift sensitively to a decrease in the air ratio. In addition, the flow rate of the secondary air is reduced, and thus the lift is suppressed. As a result, even if the state of the flame is detected by the thermocouple,
Incomplete combustion due to low airflow cannot be prevented.

Therefore, the applicant of the present application has previously proposed a combustion safety device that reliably detects incomplete combustion even if the air volume is low due to insufficient oxygen supply or exhaust due to lack of oxygen in the room (Japanese Patent Application No. 2002-110,086). Hei 4-358213). According to this technique, as shown in FIG. 9, the burner plate P is surrounded by a cylindrical guard G to prevent contact of the secondary air of the flame and perform all the primary combustion, and the flame formation position at this time is determined by a thermocouple TC. It is to detect. According to this safety device, the flame formation position changes (lifts) sensitively to fluctuations in the amount of combustion air and oxygen deficiency in the room without being affected by the secondary air, resulting in incomplete combustion. It was surely prevented and very good.

[0006]

However, in this combustion safety device, the flame starts to lift from the burner plate when the air volume starts to run short, and when the air volume reaches a predetermined air volume level, the flame is held at the open end of the cylindrical guard. However, the flame may flutter at a low level of insufficient air flow until the flame reaches the opening end of the cylindrical guard, and the output of the thermocouple tends to be unstable. That is, in a transition state from a normal state in which the flame is held by the burner plate to a state in which the flame is held by the opening end of the cylindrical guard, the output of the thermocouple becomes unstable due to fluttering of the flame. Therefore, in order to further improve the detection accuracy, it is necessary to narrow the range of the air volume level at which the transition state occurs as much as possible. Incidentally, such a problem was the same as in the case of lack of oxygen in a room. The combustion safety device of the present invention solves the above-mentioned problem, and narrows the air flow range (or oxygen concentration range) from when the flame starts to lift due to insufficient air flow (or lack of oxygen) until the flame is held by the cylindrical guard. Therefore, an object is to detect incomplete combustion with high accuracy.

[0007]

In order to solve the above-mentioned problems, a combustion safety device according to the present invention includes a main burner adjacent to a main burner for forcibly taking in combustion air and burning.
A safety device disposed in a combustion air supply passage of a burner, comprising: a premix burner having a burner plate having a plurality of flame openings; and a burner surrounding the burner plate.
Flame formed on the plate and around the premix burner
Blocking the contact with the combustion air prevents all
A cylindrical guard for primary combustion and formed inside the cylindrical guard
A thermocouple that outputs a detection signal corresponding to the position of the flame to be fired, and the tubular guard is inserted with the thermocouple.
Smaller area than the above burner plate downstream from the position
Opening due to insufficient supply of combustion air
The flame formed on the burner plate lifted
At that time, the flame is cut into Bunsen combustion at the throttle opening.
In other words, the point is to keep the flame in place.

[0008]

According to 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, so that all the primary combustion is performed. The thermocouple outputs a detection signal corresponding to.
The position where the flame is formed is determined by the balance between the combustion speed and the injection speed of the air-fuel mixture. In normal operation, a flame is formed on the burner plate. However, when the amount of combustion air decreases due to a defective air supply / exhaust system, the air ratio of the premix burner decreases and the combustion speed decreases. In this case, since all primary combustion is performed, the state of the flame changes only in the fuel ejection direction, and the flame lifts sensitively. Although the flame becomes unstable when the flame is lifted in the cylindrical guard down the tubular guard
Since the aperture is provided, the ejection speed at the aperture is increased. Therefore, the combustion speed and the ejection speed at the opening stop is easily balanced, flame ahead is held in the opening stop of the cylinder on the guard before the air volume deficiency progresses. As a result, bus
Opening of the cylindrical guard from all primary combustion on the
Smoothly switches to Bunsen combustion at the mouth and opens the throttle
The electromotive force of the thermocouple upstream of the mouth can be sharply reduced. In other words, when the throttle opening is not provided in the cylindrical guard, the jetting speed at the opening of the cylindrical guard is low, so that the airflow shortage does not proceed to some extent (unless the combustion speed decreases), so that the guard is held at the tip of the cylindrical guard. Can't burn, but squeeze on cylindrical guard
By providing the opening, it is possible to shift to the flame holding state early from the start of the lift.

Further, when the room 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 formation position changes, and the flame is held in the narrowed portion of the tubular guard early from the start of the lift. As a result, a sufficient change in the electromotive force of the thermocouple is obtained, and incomplete combustion can be reliably detected.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to further clarify the configuration and operation of the present invention described above, a preferred embodiment 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 one embodiment. The combustion safety device 1 is provided adjacent to the main burner in a combustion chamber of a forced exhaust gas (FE) gas water heater described later, and includes a mixing pipe 2 through which fuel gas and combustion air are mixed by suction. A cylindrical pressure regulating chamber 3 connected to the mixing pipe 2 to make the pressure distribution and concentration distribution of the air-fuel mixture uniform, and a burner plate 5 formed with a plurality of flame outlets 4 from which the air-fuel mixture is ejected (in this embodiment, a ceramic plate) To form a premix burner 6. Further, a cylindrical tubular guard 7 which surrounds the periphery of the burner plate 5 and prevents contact of the secondary air of the flame formed on the plate 5 is mounted. Although the distal end of the cylindrical guard 7 is open, the opening 8 is narrowed inward in an L-shaped cross section to form a diaphragm. In this embodiment, the diameter φA of the burner plate 5
(= Φ16), the diameter φB of the opening is set to φ12.

A gas nozzle 20 is provided in the opening 9 of the mixing tube 2.
The combustion air is also sucked in at the same time by the ejection of the fuel gas. The opening is set such that the air ratio in the mixing pipe 2 is 0.9 in a normal state. This mixture ratio (0.9) is a setting at which the combustion speed is maximized. That is, when the mixture ratio deviates from this value, the combustion speed is reduced.

The tubular guard 7 has a thermocouple 10 from the side.
The heat-sensitive portion 10a, which is the tip of, is inserted. This thermocouple 1
0 is provided at a predetermined distance from the surface of the burner plate 5 so as to strike the outer flame of the flame in a normal state.
Other than the heat-sensitive portion 10a, the thermocouple 10 is located outside the cylindrical guard 7, and the secondary air flowing upward around the cylindrical guard 7 directly hits the thermocouple 10 to cool it. no problem. The thermocouple 10 is connected to a combustion controller (not shown) of the water heater, and is configured to control opening and closing of an electromagnetic valve provided in a gas passage of a main burner according to an electromotive force of the thermocouple 10. I have. That is, the thermocouple 10
Operates so that the gas flow path is closed when the electromotive force becomes lower than a predetermined level. It should be noted that the configuration may be such that the magnet safety valve is attracted and held by the electromotive force of the thermocouple 10 to keep the gas flow path open.

The air-fuel mixture which has been mixed and adjusted in the pressure adjustment chamber 3 is blown out from each of the burners 4 of the burner plate 5 and is transferred from the main burner (shown in FIG. 7) of the water heater to the surface of the plate 5. Forms a flame. In this case, the supply of the secondary air is interrupted by the cylindrical guard 7 surrounding the flame, and all the primary combustion is performed.

When the air volume of the combustion air decreases due to blockage of the fins of a heat exchanger (not shown) or a reduction in the fan capacity for feeding the combustion air into the combustion chamber, the air ratio in the pressure regulating chamber 3 decreases, and the combustion speed decreases. descend. For this reason, the flame formed on the burner plate 5 starts to lift, and when the flame volume decreases to a predetermined air volume, the flame is finally held at the distal end opening 8 of the cylindrical guard 7 as shown in FIG. That is, during the entire primary combustion, the flame lifts sensitively to a decrease in the air volume (a decrease in the air ratio), and when the flame reaches the tip opening 8 of the cylindrical guard 7, the secondary air is supplied from therearound. Bunsen combustion is performed. Further, during Bunsen combustion, since the combustion is diffusion combustion and the force for lifting the flame upward due to a decrease in the airflow decreases, the lift hardly occurs in response to a change in the airflow.

By the way, during the period from when the flame starts to lift to when the flame is held in the tip opening 8, the flame flaps and the output of the thermocouple 10 becomes unstable. Therefore,
In order to narrow the air volume range until the flame is held in the front end opening 8 of the cylindrical guard 7, the opening diameter φB of the front end opening 8 is made smaller than the burner plate diameter φA to form an aperture shape. . The reason will be described below.

The combustion position of the flame is determined by the relationship between the combustion speed and the injection speed of the air-fuel mixture. Under normal conditions, the combustion speed and the ejection speed are balanced to form a flame on the burner plate 5. However, when the air volume decreases, the combustion speed decreases and the flame lifts. In order to cause the distal end opening 8 of the cylindrical guard 7 to hold the flame, the combustion speed must be reduced to a level below the level at which the mixture mixture is ejected at the opening 8. On the other hand, the ejection speed of the distal end opening 8 is lower than the ejection speed on the burner plate 5, but is higher than that of the one not narrowing the opening (shown in FIG. 9). Accordingly, the combustion speed and the ejection speed balance faster as compared with the case where the opening is not narrowed. As a result, the range of the air volume from when the flame starts to be lifted until when the flame is held at the distal end opening 8 is narrowed, and the period in which the flame flaps in the cylindrical guard 7 can be shortened.

Here, the output characteristics of the thermocouple 10 with respect to a change in air flow when the diameter of the opening 8 of the cylindrical guard 7 is changed will be described with reference to FIG. FIG. 4 shows the change in electromotive force of the thermocouple 10 when the opening 8 of the cylindrical guard 7 is φ12, φ14, and φ16 with respect to the diameter φ16 of the burner plate 5. As shown in the figure, when the opening 8 has a diameter of φ16, that is, when the opening 8 has the same diameter as the burner plate 5, the output of the thermocouple 10 is reduced when the fan rotation speed (corresponding to the air flow) is reduced. It will drop gently. In the test, when the flame starts to lift on the burner plate, the electromotive voltage of the thermocouple 10 is about 30 mv, and the electromotive voltage when the flame is held by the opening 8 of the cylindrical guard 7 is about 10 mv. is there. Therefore, when the fan speed is 4500
When the rotational speed is between 3 rpm and 3800 rpm, the flame cannot lift to the opening 8 and flutters.

On the other hand, when the diameter of the opening 8 is reduced, for example, in the case of φ12, the output of the thermocouple 10 sharply decreases with a decrease in the air volume. Therefore, when the fan speed is 44
The flame starts to lift at 00 rpm, and is held in the opening 8 of the cylindrical guard 7 at 4200 rpm. As a result, the period in which the flame flaps in the cylindrical guard 7 is shortened.

FIG. 3 shows the thermocouple 10 with respect to the air ratio λ of the main burner when the combustion safety device is incorporated in the water heater.
And the concentration of carbon monoxide. As described above, when the air ratio decreases, the electromotive force of the thermocouple 10 sharply decreases,
Before the concentration of carbon monoxide becomes high, the concentration becomes equal to or less than the set value, and the gas flow path can be closed.

Further, when the oxygen concentration in the room decreases, the combustion speed decreases because the amount of oxygen contributing to combustion decreases even if the air volume (air ratio) is the same. As a result, the flame lifts sensitively as described above. As a result, the electromotive force of the thermocouple decreases sufficiently before the carbon monoxide concentration increases, and the gas flow path can be reliably closed at a safe level.

Next, a combustion safety device according to a second embodiment will be described with reference to FIG. This combustion safety device 1
In this embodiment, the shape of the cylindrical guard 7 is changed from that shown in the previous embodiment. The cylindrical guard 7 is formed such that the wall surface is formed to have a tapered shape by increasing the wall thickness at the front end, and the diameter φB of the front end opening 8 is smaller than the diameter φA of the burner plate. Therefore, the ejection speed at the opening 8 is higher than that when the opening 8 is not narrowed, and the air ratio range from when the flame starts to lift on the burner plate 5 to when the flame is held by the opening 8 is narrow. Become. As a result, the thermocouple 10
The output characteristics with respect to the air ratio become very good.

In the combustion safety device shown in these embodiments, the opening 8 has a throttle shape, but a throttle portion may be provided in the middle of the cylindrical guard 7. For example, as shown in FIG.
In the middle of the tubular guard 7, a throttle portion 8 is provided downstream of the thermocouple 10.
Similar effects can be obtained by forming a.

Next, an example of a configuration in which the combustion safety device 1 is incorporated in a gas water heater will be described. FIG. 7 is a schematic configuration diagram of the inside of the combustion chamber 30 of the FE gas water heater as viewed from above. In the combustion chamber 30, a plurality of flat main burners 31 are arranged side by side, a damper 33 for adjusting a primary air amount is provided at the tip of the throat 32, and fuel gas is supplied from each gas nozzle 35 provided on a nozzle base 34. Is supplied. This nozzle base 3
The gas flow path to 4 is provided with a proportional control valve for adjusting the capacity (amount of combustion) and an electromagnetic valve (not shown) for opening and closing the gas flow path. Further, a sirocco fan (not shown) is provided below the combustion chamber 30 to supply combustion air to the combustion chamber 30 to perform Bunsen combustion with the main burner 31, and a heat exchanger (not shown) is generated by the combustion heat. It is configured to heat and tap. The combustion safety device 1 is provided in parallel with the main burner 31 and has a gas nozzle 36 provided on a common nozzle base 34.
Is supplied with fuel gas. Therefore, the structure is simple without providing a separate gas flow path. In addition, 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 is reduced to a predetermined value or less, the rotation speed of the fan may be adjusted before closing the gas flow path. In other words, when the air ratio is reduced due to a headwind from an exhaust duct (not shown) or a fin blockage, there is a case where the air conditioner can be used without stopping the combustor by increasing the rotation speed of the fan. Therefore, when the electromotive force of the thermocouple 10 decreases to a preset level, when the rotation speed of the fan is increased and the recovery of the electromotive force is not obtained even when the predetermined rotation speed is reached, that is, when the air ratio is increased. When it does not increase, the gas flow path is closed to stop the instrument. Further, the gas flow path may be closed when the electromotive force does not recover even after a predetermined period of time has elapsed since the rotation speed of the fan was increased.

Further, the fan speed may be controlled so that the electromotive force of the thermocouple 10 always becomes a constant value. That is, the rotation speed of the fan is controlled 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. Such control based on the electromotive force of the thermocouple 10 is possible because the combustion safety device 1 very sensitively detects an insufficient air volume or an oxygen deficiency state (see the characteristic diagram of FIG. 3). It is impossible to detect a lift with high precision even if one wants accurate control. At the start of combustion, the control operation is not performed until the electromotive force of the thermocouple 10 is stabilized.

The embodiments of the present invention have been described above.
The present invention is not limited to these embodiments at all, 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 present invention can be applied not only to a water heater but also to a combustor such as a fan heater. Also,
It can also be used as a sensor for detecting a decrease in air flow, even in an external-type appliance in which oxygen deficiency is not a concern.

[0027]

As described above, according to the combustion safety device of the present invention , the burner plate is surrounded by the cylindrical guard.
Burner play if the supply of combustion air is normal
All primary combustion on the air
And switch to Bunsen combustion at the throttle opening for flame holding
Therefore, the flame position is sensitive to the air supply shortage and
Whether the air supply is insufficient
Can be clearly distinguished. In addition, mixing at the aperture
The spouting speed of the air increases, and the combustion speed and the spouting speed
Flame lifts from the burner plate
The transition from starting to flame holding on the cylindrical guard is smooth.
And detects the shortage of air supply from the thermocouple electromotive force.
It can be performed with high accuracy.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram illustrating a state of a flame when a flow rate is reduced.

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

FIG. 4 is a graph showing the electromotive force characteristics of a thermocouple when the diameter of an opening is changed.

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

FIG. 8 is a schematic configuration diagram of a conventional combustion safety device.

FIG. 9 is a schematic configuration diagram of the previously proposed combustion safety device.

[Explanation of symbols]

1: Combustion safety device, 5: Burner plate, 6: Premix burner, 7: Cylindrical guard, 8: Opening (throttle),
10: Thermocouple, 10a: Thermosensitive part.

Claims (1)

(57) [Claims] 1. A combustion burner of a main burner adjacent to a main burner which forcibly takes in combustion air and burns the combustion air.
A safety device which is disposed in the air supply passage, a premix burner having a burner plate having a plurality of burner ports, surrounds the burner plate, the form of the above burner plate
The flame formed and the combustion air around the premix burner
All primary combustion on the burner plate
A cylindrical guard, and a thermocouple that is inserted into the wall surface of the cylindrical guard and outputs a detection signal in accordance with the position at which the flame is formed. The cylindrical guard is further downstream than the insertion position of the thermocouple.
The aperture opening is smaller than the above burner plate.
Burner press due to insufficient combustion air supply.
When the flame that forms on the plate lifts,
Combustion safety device, wherein the this <br/> that flame holding is switched to Bunsen combustion in the iris opening.