JP3249875B2 - 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 surroundings of the burner plate 15 on which the 4 is formed are surrounded by a cylindrical guard 17, and all the primary combustion is performed on the burner plate 15, and the state of the flame is detected by a thermocouple 19. Since the burner plate 15 is initially unaffected by the secondary air by the cylindrical guard 17,
The lift is quickly generated in a state where the flame is stable, and as a result, incomplete combustion can be detected with certainty even if there is a lack of oxygen in the room or a decrease in air volume due to a failure in the air supply / exhaust system. FIG. 12 shows the relationship between the electromotive force of the thermocouple 19 and the carbon monoxide concentration with respect to the air ratio (the ratio of the actual air amount to the theoretical air amount) λ when the combustion safety device 10 is incorporated in the water heater. Further, when the air ratio λ (the number of rotations of the fan in FIG. 12) decreases, the concentration of carbon monoxide rapidly increases and 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 before the concentration of carbon monoxide increases, and the gas flow path can be closed. (Note that, for the sake of convenience, the characteristics of two types of gases are described in FIG. 12.) The air ratio λ during the combustion of the water heater is proportional to the rotation speed of the fan that supplies the combustion air. The horizontal axis is replaced by the number of rotations of the fan, and by this, the combustion safety device 10 can also be used as a sensor for detecting a decrease in air volume.

[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. 12 shows an example. FIG. 12 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 time 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 13A gas and propane gas, about 1% is obtained.
There is only a shift of 000 rotations. Therefore, in 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 of propane gas Before the temperature rises, a region where the thermocouple electromotive force changes abruptly and the determination threshold 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 of the present invention solves the above-mentioned problems, and achieves 13
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]

According to a first aspect of the present invention, there is provided a combustion safety device which is provided 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, wherein a premix burner in which a porous ceramic having air permeability between a front surface and a back surface has a flame forming surface, and a premix burner surrounding the flame forming surface. The flame formed on the flame forming surface and the premix bar
By preventing contact with the combustion air around the
The gist comprises a cylindrical guard for lifting the flame when the supply amount of the burning air is insufficient, and a flame detecting element for outputting a detection signal according to a position where the flame is formed. In addition, a second combustion safety device of the present invention that solves the above-mentioned problem is that the porous ceramic has air permeability between the front and back surfaces, and a pore passing through the front and back surfaces is provided as a flame port. And

[0006]

In the first combustion safety device of the present invention having the above-described structure, a flame is formed by an air-fuel mixture squirting so as to penetrate the surface of the flame port due to the porous ceramic having air permeability between the front and back surfaces. Is done. Then, the flame is formed in a very stable state on the surface of the flame opening of the porous ceramics, with the combustion speed of the air-fuel mixture and the jetting speed slowed down by being prevented from jetting directly being balanced. 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. In the second combustion safety device, the air-fuel mixture having a high flow velocity flows through pores penetrating the front and back surfaces of the porous ceramic, and the air-fuel mixture having a low flow velocity is prevented from directly ejecting from the remaining surface. Squirt like soaking. Since the flow rate of the air-fuel mixture from the remaining surface is slow, even if there is no flame holding part near the pores that become the flame mouth, the surface becomes a flame holding part with the balance of the gas burning rate and a flame is formed, A very stable flame is formed near the flame opening of the porous ceramic. At this time, dust and dirt contained in the fuel gas and the combustion air pass through the pores serving as the flame ports, so that the porous ceramics are less clogged and can maintain stable performance for a long time. 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. In these combustion safety devices,
When the amount of combustion air decreases due to a defective air 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 in the fuel ejection direction and lifts, and the flame formation position greatly changes. In addition, the above-mentioned function of the cylindrical guard is not affected by the flow rate of the secondary air (the lower the air ratio, the lower the flow rate of the secondary air.
If there is no tubular guard, it will hold down the flame lift, but 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 in the flame formation position are reliable, even if the gas type is different, the change in the output characteristics of the flame detecting element is reduced, and the same specifications can be achieved. Further, when the room is in an oxygen-deficient state, even if the air ratio of the air-fuel mixture is constant, the amount of oxygen contributing to combustion is substantially reduced. Changes reliably as described above. As a result, these combustion safety devices can surely 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. A combustion safety device 1 is provided adjacent to a main burner in a combustion chamber of a forced exhaust gas (FE type) gas water heater described later. A premix burner 5 is constituted by a porous ceramics 4 mounted in the middle of the body 2 and having a plurality of pores (diameter of about 2 mm or less in this embodiment) as a flame outlet 3 and a premix burner 5 at the top of the cylindrical body 2 (porous body). A cylindrical guard 6 whose upper part is above ceramics 4 prevents secondary air contact
It has become. Specifically, the gas nozzle 20 faces the lower opening 7 of the cylindrical body 2, and the space up to the porous ceramics 4 is defined as a mixing chamber 8, and the lower opening is set so that the air ratio in the mixing chamber 8 is normally 0.9. The opening of the section 7 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.
As shown in the cross-sectional view and the top view, the ceramics 40 are made of coarse-grained ceramics 40 and have air permeability between the front surface 4a and the back surface 4b due to gaps formed between the ceramics 40. A large number of fine holes penetrating the front surface 4a and the back surface 4b are provided as the flame outlet 3. The porous ceramics 4 used in the present example has a pore diameter of 0.5 mm to 2 mm, and cordierite or β-spodumene as the ceramics 40. Rate) 65-95
%, And the size of the gap is 20 to 50 cells (the number of holes per square inch).

[0008] In the combustion safety device 1 having the above-described structure, the air-fuel mixture having a higher flow rate than the flame port 3 composed of the pores penetrating the front and back of the porous ceramics 4 is directly ejected from the remaining surface 4 a of the porous ceramics 4. The air-fuel mixture whose flow velocity has been slowed down by being prevented from spraying is jetted out so as to soak. (Figure 2
See) Because the flow rate of the mixture from the surface 4a is slow,
Even if there is no flame holding part near the pores serving as the flame outlet 3, the surface 4a becomes a flame holding part due to the balance of the gas burning rate, and a flame is formed. A stable flame is formed. In this case, as will be described in detail later, since the supply of the secondary air is interrupted by the cylindrical guard 6 surrounding the flame and the entire primary combustion is performed, even in the case of the incomplete combustion, the flame is discharged. Lift securely without being affected. In the cylindrical guard 6,
The thermocouple 9 is mounted from the lateral direction, and the heat receiving portion 9a is positioned in the flame. The thermocouple 9 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 the main burner according to an electromotive force of the thermocouple 9. That is, it operates so as to close the gas flow path when the electromotive force of the thermocouple 9 becomes lower than the predetermined level. 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 is reduced due to blockage of a fin of a heat exchanger (not shown) or a reduction in a fan capacity for feeding the combustion air into the combustion chamber, the air ratio in the mixing chamber 8 is reduced and the combustion speed is reduced. I do. For this reason, the flame formed in the flame outlet is lifted, and finally, the flame is formed in the opening at the tip end of the cylindrical guard 6 as shown in FIG. In other words, during the entire primary combustion, the flame reliably lifts without being affected by the secondary air with respect to the decrease in the air volume (the decrease in the air ratio). Secondary air is supplied 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 electromotive force of the thermocouple 9 sharply decreases as shown in FIG. 4, but the carbon monoxide concentration sharply increases. This characteristic diagram was obtained by an experiment. The horizontal axis represents the number of revolutions (rpm) of the fan that feeds combustion air into the combustion chamber, the solid line and the dashed line represent the electromotive force (mV) of the thermocouple, and the broken line represents the instrument. Indicates the concentration (ppm) of carbon monoxide in the exhaust gas. The gas type is propane gas and 13
Experiments were conducted for different gas types of A gas, and for comparison, a conventional example (dashed line) and this example (solid line) are shown side by side. (The conventional example has the same characteristic diagram as FIG. 12)
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 is 13 A
In the case of propane gas, the electromotive force characteristics of the present embodiment are shifted to a higher rotation speed side than in the conventional example, while the gas is not much different from the conventional example. 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 the present embodiment, since the air-fuel mixture is jetted not only from the flame outlet 3 but also from the surface 4a, the generation of vortices is small. It 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 drops to 18.5% or less, whereas the electromotive force of the thermocouple 9 decreases linearly 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.

Next, a modification of the mounting position of the thermocouple 9 will be described. In the above embodiment, the thermocouple 9 is connected to the cylindrical guard 6.
However, as shown in FIG. 7, the heat receiving portion 9a may be located in the flame by penetrating the center of the porous ceramics 4 as shown in FIG.

Various shapes of the premix burner 5 are also conceivable. For example, as shown in FIG. 8, the throat 11 formed in a U-shape may be relayed and arranged sideways to prevent clogging of falling objects due to drain or the like 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. 10 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. A proportional control valve for adjusting the capacity (burning amount) and a solenoid valve for opening and closing the gas flow path (not shown) are provided in the gas flow path to the nozzle base 34.
Is provided. 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 always becomes a constant value. 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. 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.

[0020]

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 porous ceramic as one example.

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 illustrating a modification of a mounting position of a thermocouple.

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

FIG. 9 is a schematic configuration diagram of a combustion safety device according to another embodiment.

FIG. 10 is an explanatory diagram showing a combustion chamber in a state where a combustion safety device is incorporated in a gas water heater.

FIG. 11 is a schematic configuration diagram of a conventional combustion safety device.

FIG. 12 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 4 Porous ceramic 6,17 Cylindrical guard 15 Burner plate 9,19 Thermocouple

Claims (2)

(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 of porous ceramic was flame port formation surface having breathable between front and rear surfaces, surrounding the flame orifice formation surface, the flame hole Formed on the forming surface
Keep the flame in contact with the combustion air around the premix burner.
If the supply of combustion air is insufficient,
A combustion safety device comprising: a tubular guard that lifts a flame; and a flame detection element that outputs a detection signal according to a position where the flame is formed. 2. The combustion safety device according to claim 1, wherein the porous ceramic has air permeability between the front and back surfaces, and a fine hole penetrating the front and back surfaces is provided as a flame port.