JP3249873B2 - 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. Regarding the technology of such a safety device, the present applicant has previously filed an application in Japanese Patent Application No. 4-358213 for a technology for detecting incomplete combustion with high accuracy regardless of whether the air supply / exhaust system is defective or the room is deficient in oxygen. I have.

[0003] As shown in FIG.
The burner plate 15 on which the burner 4 is formed is surrounded by a cylindrical guard 17, and all the primary combustion is performed on the burner plate 15. The state of the flame is detected by a thermocouple 19 according to the flame forming position. is there. At the time of incomplete combustion such as a defective supply / exhaust system or lack of oxygen in the room, the flame generated from the flame port 14 of the burner plate 15 is initially in the cylindrical guard 17 and is not affected by secondary air from the outside. When the air ratio (the ratio of the actual air amount to the theoretical air amount) of the air-fuel mixture composed of the fuel gas and the combustion air is reduced and the combustion speed is reduced, a lift is quickly generated in the jetting direction. Once the lift occurs, the flame is held in the opening of the tip of the cylindrical guard, and secondary air is supplied from the surroundings to perform Bunsen combustion. The thermocouple 19 detects the temperature of the internal flame having a low temperature from the external flame having a high temperature of the flame. As a result, it is possible to surely detect a lack of air in the room or a decrease in the air volume due to a defective supply / exhaust system. It has the characteristic that incomplete combustion can be detected. Air ratio (ratio of actual air amount to stoichiometric air amount) when this combustion safety device 10 is incorporated in a water heater
As shown in FIG. 11, the relationship between the electromotive force of the thermocouple 19 and the carbon monoxide concentration is as shown in FIG. 11, when the air ratio λ (the fan speed in FIG. 11) decreases, the carbon monoxide concentration sharply increases, and the flame quickly lifts. As a result, the thermocouple 19 detects a lift flame, so that the electromotive force of the thermocouple 19 rapidly decreases. Therefore, the combustion safety device 10 is excellent in that the electromotive force of the thermocouple 19 becomes equal to or less than the set value and the gas flow path can be closed before the concentration of carbon monoxide increases (the later description). For the sake of convenience, FIG. 11 shows characteristics of two types of gases.) Since the air ratio λ during the combustion of the water heater is proportional to the rotation speed of the fan for supplying the combustion air, the horizontal axis in FIG. 11 is replaced by the rotation speed of the fan. It can also be used as a sensor for detecting a drop.

[0004]

However, even if these safety devices are incorporated in a combustion device that forcibly takes in combustion air by a fan, incomplete combustion can be determined in the case of the same specifications due to differences in gas types. The problem that it was difficult occurred. The contents and the reason will be described.
Gas groups used for combustion equipment and the like are generally roughly classified into two types, that is, propane gas and city gas, which are supplied and used for industrial and household purposes. In addition, city gas has various gas types, and is called by 13A or 6C, etc., and combustion equipment corresponding to those gas types is sold, and the specifications of the combustion equipment are different between different gas types. It cannot be used as it is. Supplying and adjusting components with different specifications for all of the dozens of these gas types requires a great deal of labor and cost, and therefore, it is always necessary for combustion equipment vendors to use common components and common specifications. Is a problem. For the reasons described above, for example, when the conventional combustion safety device 10 is used with the same specifications in propane gas and 13A gas,
There is a large difference in the thermocouple detection electromotive force characteristics with respect to the air ratio λ. FIG. 11 shows an example. FIG. 11 is a graph obtained by the experiment, in which the horizontal axis represents the number of rotations of the fan for supplying the combustion air, and the vertical axis represents the thermocouple electromotive force. As described above, the air ratio λ during combustion is proportional to the number of revolutions of the fan, so the same applies even if the horizontal axis is replaced with the air ratio λ. According to this, the thermocouple electromotive force characteristic obtained from 13A gas is:
1 compared to thermocouple electromotive force characteristics obtained from propane gas
At the point of 0 mV, the characteristic is shifted to the high rotation side by about 1300 rotations. However, similarly, when comparing the characteristics of the carbon monoxide concentration between the 13A gas and the propane gas, there is only a shift of about 1000 rotations. Therefore, when determining the propane gas specification of the combustion equipment incorporating the combustion safety device 10, even if it is attempted to determine the set value of the combustion control while keeping the 13A gas specification (specifically, the carbon monoxide concentration becomes high). Previously, a region where the thermocouple electromotive force changes abruptly and the threshold value for the determination of incomplete combustion greatly changes, that is, a thermocouple electromotive force of about 10 mV is used) is used. The same set value cannot be determined for gas. That is, in the vicinity of 10 mV where the change in thermocouple electromotive force of the 13A gas becomes large, the concentration of carbon monoxide in the propane gas exceeds the dangerous concentration, and the function as a safety device cannot be provided. The combustion safety device according to the present invention solves the above-mentioned problems, and realizes a fuel safety device that uses a fuel gas of propane gas.
It is an object of the present invention to reliably detect incomplete combustion of A gas without changing the specification of the gas type.

[0005]

A combustion safety device according to the present invention which solves the above-mentioned problems is provided adjacent to a main burner which forcibly takes in combustion air and burns.
A safety device disposed in a baking air supply passage, comprising: a premix burner having a burner plate having a plurality of flame openings; and a burner plate surrounding the burner plate.
And the combustion air around the premixed burner
Above the burner plate by preventing air contact
To perform all primary combustion, and when the supply of combustion air is insufficient
A cylindrical guard that lifts the flame on the burner plate, and a flame detection element that is inserted into the wall surface of the cylindrical guard and outputs a detection signal according to the formation position of the flame, and a flame port of the burner plate has The gist is that it is provided perpendicular to the axial direction of the cylindrical guard.

[0006]

In the combustion safety device according to the present invention having the above-described structure, a flame is formed by the air-fuel mixture jetted from a flame port provided in the burner plate. Then, the flame generated from each flame port is directed toward the center of the cylindrical guard since each flame port is provided perpendicular to the axial direction of the cylindrical guard. Therefore, the tips of the flames try to spread against each other at the center of the tubular guard. As a result, the flame spreads in a well-balanced manner as a whole, and a very stable flame is formed in the cylindrical guard regardless of the type of gas. Further, the flame is prevented from contacting with the secondary air by the cylindrical guard, so that all the primary combustion is performed, and the flame detection element outputs a detection signal corresponding to a position where the flame is formed. Note that the combustion exhaust is discharged from the opening of the cylindrical guard. When the amount of combustion air decreases due to a defective supply / exhaust system, the air ratio of the air-fuel mixture decreases and the combustion speed changes. In this case, since all the primary combustion is performed, the flame that has been stable until now changes and lifts, and the flame formation position greatly changes. The air-fuel mixture is once jetted perpendicular to the cylindrical guard axis from the flame outlet, but it is directed to the cylindrical guard opening immediately after diffusion, so it is formed by the balance between the flow of the air-fuel mixture and the combustion speed The flame lifts along the cylindrical guard axis to the cylindrical guard opening. In addition, the function of the above-described cylindrical guard is not affected by the flow rate of the secondary air (if the air ratio is reduced, the flow rate of the secondary air is also reduced. Therefore, if there is no cylindrical guard, the flame lift can be suppressed. Will work.) As a result, the flame formation position is reliably changed with respect to the fluctuation of the combustion air amount, and the lift is performed. As a result, the output of the flame detection element is changed, and the abnormality is detected. Since the stability of combustion and the change of the flame formation position are reliable,
Even if the gas type is different, the change in the output characteristic of the flame detecting element is reduced, and the same specification can be made for the gas type. Also,
When the room is in an oxygen-deficient state, the amount of oxygen contributing to combustion is substantially reduced even if the air ratio of the air-fuel mixture is constant. It will definitely change as you did. In this case, similarly, even if the gas type is different, the change in the output characteristic of the flame detecting element is reduced, and the same specification can be made for the gas type. As a result, this combustion safety device can reliably prevent incomplete combustion with the same specification for the gas type even if the gas type is different based on the output of the flame detection element.

[0007]

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 a main burner in a combustion chamber of a forced exhaust gas (FE) gas water heater described later, and is an elbow-shaped mixing pipe through which fuel gas and combustion air are mixed by suction. A premix burner 5 is composed of a burner plate 4 having a plurality of flame outlets 3 from which a gas-fuel mixture mixed by a mixing tube is jetted. Also,
A cylindrical cylindrical guard 6 surrounding the burner plate 4 and preventing contact of secondary air of the flame formed by the flame port 3
Is attached. Specifically, the gas nozzle 20 faces the opening 7 of the mixing pipe 2, the space between the gas nozzle 20 and the burner plate 4 is defined as a mixing chamber 8, and the air ratio in the mixing chamber 8 is set to 0.9 in a normal state. The opening is set. 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. As shown in FIG. 2, the burner plate 4 forms a groove 25 on the outer periphery of a cylindrical main body.
At the bottom, a large number of flame ports 3 (upper row) and vent holes 18 (lower row) are provided radially toward the center. The burner plate 4 has recesses 23 and 28 formed vertically above and below the boundary surface 26, and the above-described flame outlet 3 is formed in the recess 2
3, the vent 9 opens into a recess 28. The burner plate 4 is inserted into the cylindrical guard 6 using the outer periphery of the main body as a guide, so that the flame port 3 is perpendicular to the axial direction of the cylindrical guard 6 as shown in FIG.

The air-fuel mixture mixed in the mixing chamber 8 flows from the recess 28 of the burner plate 4 through the vent 18 to each of the flame ports 3.
From the main water burner 31 (shown in FIG. 9)
Then, a flame is formed in the tubular guard 6. The flame generated from each flame port 3 is provided because each flame port 3 is provided in the axial direction of the cylindrical guard 6.
The tips of the flames try to spread by pressing against each other at the center of the cylindrical guard 6. As a result, the flame spreads in a well-balanced manner as a whole, and a very stable flame is formed in the tubular guard 6. Further, the flame is prevented from being in contact with the secondary air by the cylindrical guard 6 surrounding the flame, so that all the primary combustion is performed. Therefore, even when the combustion is incomplete, the flame is not affected by the flow velocity of the secondary air. Make sure to lift. A thermocouple 9 is attached to the cylindrical guard 6 from the lateral direction, and a heat receiving portion 9a is positioned in the flame. This thermocouple 9
It is connected to a combustion controller (not shown) of the water heater, and is configured to control the opening and closing of 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 falls below a predetermined level, the thermocouple 9 operates to close the gas flow path. Note that a configuration may be employed in which the magnet safety valve is attracted and held by the electromotive force of the thermocouple 9 to maintain the gas passage open.

When the air volume of the combustion air decreases due to blockage of the fins of a heat exchanger (not shown) or a decrease in the fan capacity for feeding the combustion air into the combustion chamber, the air ratio of the air-fuel mixture in the mixing chamber 8 decreases, and the combustion proceeds. Speed decreases. Once the air-fuel mixture is ejected from the flame outlet 3 toward the axis of the cylindrical guard 6, the air-fuel mixture is directed toward the opening of the cylindrical guard 6 immediately after the diffusion. The formed flame lifts along the axis of the cylindrical guard 6 to the opening of the cylindrical guard 6. In addition, the function of the cylindrical guard 6 is not affected by the flow rate of the secondary air. In other words, if the air ratio decreases, the flow velocity of the secondary air also decreases, and if the cylindrical guard 6 is not provided, the flame lift is suppressed, but instead acts as a crook. As a result, the flame formation position is reliably changed with respect to the fluctuation of the combustion air amount, and the lift is performed, and finally, the flame is formed at the opening of the end of the cylindrical guard 6 as shown in FIG. That is, during the entire primary combustion, when the flame lifts reliably without being affected by the flow rate of the secondary air in response to a decrease in the air volume (a decrease in the air ratio), when the flame reaches the opening of the end of the cylindrical guard 6, the flame is lifted. Secondary air is supplied from the surroundings to perform Bunsen combustion. 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.

When the air volume decreases in this manner, the shape of the flame changes, and the electromotive force of the thermocouple 9 sharply decreases as shown in FIG. 4, while the carbon monoxide concentration sharply increases. This characteristic diagram was obtained by an experiment, and the horizontal axis represents the number of revolutions (rpm) of the fan that sends combustion air into the combustion chamber.
, The solid line and the dashed line indicate the electromotive force (mV) of the thermocouple, and the dashed line indicates the concentration of carbon monoxide (ppm) in the exhaust gas of the instrument. Experiments were conducted for different gas types, propane gas and 13A gas. For comparison, a conventional example (dashed line) and this embodiment (solid line) are shown side by side (the conventional example has the same characteristic diagram as FIG. 11). Is). This device has a configuration in which the air volume and the air ratio λ are proportional to the rotation speed of the fan, as in the conventional example. As can be seen from the characteristic diagram, the electromotive force characteristic of the thermocouple does not change much in the 13A gas from the conventional example, whereas the electromotive force characteristic of the present example in the propane gas is smaller than that of the conventional example. It has moved to the high rotation speed side. Therefore, for example, if the combustion safety device 1 is set so as to operate at a thermocouple electromotive force of 10 mV (close the gas flow path using a region where the thermocouple electromotive force changes rapidly), conventionally, as described above, Although the concentration of carbon monoxide has already reached a dangerous amount in propane gas and this setting cannot be used, it is a safe amount in this embodiment.
That is, not only the 13A gas but also the propane gas, the combustion safety device 1 can close the gas passage because the electromotive force of the thermocouple 9 becomes equal to or less than the set value before the carbon monoxide concentration becomes high. .

The reason for exhibiting such characteristics is considered as follows. Propane gas has a higher combustion rate than 13A gas, and the combustion rate further increases if a vortex is formed when the air-fuel mixture blows out from the flame opening. Therefore, in the conventional configuration in which a vortex is formed in the flame outlet,
Although the characteristic difference between the propane gas and the 13A gas is large, in the case of this embodiment, the flames generated from the respective flame ports 3 face each other and press against each other in the cylindrical guard 6 so as to diffuse in a well-balanced manner, thereby forming a vortex. The generation is small, and the difference between the properties of the two gases is inconspicuous.

Next, an operation for 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 decreases 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. 5, the flame during the entire primary combustion starts to lift, and after reaching the opening at the tip end of the cylindrical guard 6, misfire occurs. FIG. 6 shows the characteristics of the electromotive force of the thermocouple 9 and the concentration of carbon monoxide in the exhaust gas of the instrument in this case. This characteristic diagram is obtained by an experiment, and the horizontal axis represents the oxygen concentration. As can be seen from the characteristic diagram, the concentration of carbon monoxide sharply rises while the oxygen concentration in the room decreases to 18.5% or less, while the electromotive force of the thermocouple 9 decreases gradually with the decrease in oxygen concentration. I do. Therefore, in this case, the difference in the set value depending on the gas type does not cause much problem. That is, for any gas type, the electromotive force of the thermocouple 9 is sufficiently reduced before the carbon monoxide concentration increases, so that the gas flow path can be reliably closed at a safe level.

Various shapes of the premix burner 5 can be considered. For example, as shown in FIG. 7, the throat 11 formed in a U-shape may be relayed and arranged sideways to prevent clogging of falling objects due to drainage from the heat exchanger. Further, as shown in FIG.
The throat 12 formed in the shape of a letter may be relayed and arranged to be inclined, and a fall-off prevention plate 13 may be provided at the tip of the cylindrical guard 6. Also, the falling object prevention plate 13
Also acts as a fire transfer plate to assist the transfer of heat from the main burner.

Next, an example of a configuration in which the combustion safety device 1 is incorporated in a gas water heater will be described. FIG. 9 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 includes a main burner 31
And the gas nozzles 3 provided on the common nozzle base 34
Fuel gas is supplied from 6. 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 9
Although the gas flow path is closed when the electromotive force decreases below a predetermined value, the rotation speed of the fan may be adjusted before the gas flow path is closed. 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 9 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.

The fan speed may be controlled so that the electromotive force of the thermocouple 9 is always constant. That is, the rotation speed of the fan is controlled 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. Such control based on the electromotive force of the thermocouple 9 is possible because the combustion safety device 1 reliably detects an insufficient air volume or an oxygen-deficient state regardless of the gas type (see the characteristic diagram). At the start of combustion, the control operation is not performed until the electromotive force of the thermocouple 9 is stabilized.

The embodiments of the present invention have been described above.
The present invention is not limited to these examples in any way,
For example, an element such as a flame rod for detecting a flame current may be used in place of the thermocouple 9, 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 burner plate 4 in FIG.
Even if one flame outlet 3 is added to the center of the boundary surface 26, the flame is stabilized and the same effect can be obtained. Further, the present invention can be applied not only to a water heater but also to a combustor such as a fan heater. Further, the present invention can be used as a sensor for detecting a decrease in the air volume even in an external-type appliance in which oxygen deficiency is not a concern.

[0019]

As described above in detail, according to the combustion safety device of the present invention, the same specifications are maintained even if the gas type is different.
This provides an excellent effect that incomplete combustion caused by insufficient supply / exhaust of the combustor or lack of oxygen in the room can be reliably detected.

[Brief description of the drawings]

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

FIG. 2 is an enlarged view of a burner plate.

FIG. 3 is an explanatory diagram illustrating a state of a flame when a flow rate is reduced.

FIG. 4 is a graph showing an electromotive force and a CO concentration characteristic of a thermocouple with respect to a change in air flow.

FIG. 5 is an explanatory diagram showing a state of a flame when oxygen is lacking.

FIG. 6: Thermocouple electromotive force, CO, with respect to oxygen concentration fluctuations
5 is a graph showing density characteristics.

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 where a combustion safety device is incorporated in a gas water heater.

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

FIG. 11 is a graph showing the electromotive force and CO concentration characteristics of a thermocouple with respect to a change in air volume of a conventional combustion safety device.

[Explanation of symbols]

 1,10 Combustion safety device 5 Premix burner 6,17 Cylindrical guard 9,19 Thermocouple 4,14 Burner plate

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 disposed in an air supply passage, comprising: a premix burner having a burner plate having a plurality of flame openings; and a burner plate surrounding the burner plate.
The flame formed and the combustion air around the premix burner
Block all contacts on the burner plate.
Primary combustion is performed, and when the supply of combustion air is
A cylindrical guard that lifts the flame on the burner plate, and a flame detection element that is inserted through the wall surface of the cylindrical guard and outputs a detection signal according to the flame formation position, A combustion safety device provided perpendicular to the axial direction of a cylindrical guard.