JPH04369311A - Burner - Google Patents

Abstract

PURPOSE:To widen the range of adjustment of thermal power, stabilize the combustion, and give easiness of use to the device by carrying out ordinary premixture combustion of a concentrated mixture gas and air in the area where the total volume of supplied fuel is below a standard value and burning a concentrated mixture gas and diluted mixture gas individually in the area where the total volume of supplied fuel is beyond the standard value. CONSTITUTION:In the area where the total volume of supplied fuel is below a standard value the combustion is carried out in the ordinary premixture combustion in which the concentrated mixture gas from a mixer 1 and air only from a mixer 2 are supplied to a burner section 8. In the area beyond the standard value the concentrated gas from the mixer 1 and the diluted mixture gas from the mixer 2 are supplied to the burner 2 and the combustion is made with the diluted mixture gas receiving the flame holding action given by the combustion of the concentrated mixture gas. With this arrangement, in the area below the standard value, since the ordinary combustion with wide stable combustion is made, it is easy to make small the minimum input value. And, since, in the area beyond the standard value, the combustion system is by a combination of diluted mixture gas and concentrated mixture gas, it is possible to keep the state of stable combustion and make large the volume of minimum input.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a premix combustion system.

0002

BACKGROUND OF THE INVENTION Combustion devices that combine a flame hole portion to which a lean air-fuel mixture with a high air suction ratio is supplied and a flame hole portion to which a rich air-fuel mixture is supplied with a small air suction ratio are known (for example, 1-219406). FIG. 10 is a schematic diagram showing the configuration of the air-fuel mixture generating section of such an apparatus. A
is a mixing part that produces a rich mixture; B is a mixing part that produces a lean mixture; C is a gas supply source; D is a blower; E1 and E2 are gas control valves; F1 and F2 are air control valves; The fuel flow rate and the air flow rate are adjusted by each valve so that a mixture having a desired concentration is obtained in the mixing sections A and B.

By the way, in actual combustion equipment, when the thermal power is reduced, it is better to reduce the total amount of air supplied accordingly for better combustion, but the disturbance resistance and
In particular, it tends to have poor wind resistance. For this reason, the total air supply amount cannot be reduced in proportion to the total fuel supply amount, and the air suction ratio at the minimum thermal power is generally selected to be a larger value than at the maximum thermal power. For this reason, for example, the amount of air is adjusted so that the displacement is the same at maximum thermal power and at minimum thermal power, and the ratio of the input amount Ismax at maximum thermal power and the input amount Ismin at minimum thermal power is 5/1. In this case, the air suction ratio at minimum firepower will be five times that at maximum firepower.

[0004] However, such a fuel concentration is too lean and combustion cannot be maintained even if flame stabilization is achieved by combustion of a rich air-fuel mixture. Also, on the rich mixture side, changes in the air suction ratio due to thermal power adjustment are also a problem, and as a result,
Maximum input amount Ismax and minimum input amount Ism
It has been difficult to obtain a combustion device with a wide thermal power adjustment range because the in ratio (TDR) cannot be made very large. Further, as shown in the figure, it is necessary to individually adjust the fuel and air using four control valves, which makes the structure complicated and the control difficult.

[0005]

SUMMARY OF THE INVENTION The present invention has focused on these points, and has been made with the object of providing a combustion device with a relatively simple configuration that has a wide range of thermal power adjustment and is easy to use.

[0006]

[Means for Solving the Problems] In order to achieve the above-mentioned problems, the present invention provides a lean mixture generating section that is adjusted to generate a lean mixture with a large air suction ratio, and a lean mixture generating section with a small air suction ratio. It includes a rich mixture generating section that is adjusted to generate a rich mixture, and an air supply section that is configured to adjust the total air supply amount according to the total fuel supply amount,
In an area where the total fuel supply amount is below a preset reference value, the fuel supply to the lean mixture generation section is stopped and the rich mixture is sent out from the rich mixture generation section and the air is sent out from the lean mixture generation section. In addition, in the region where the total fuel supply amount exceeds the above reference value, the lean mixture and rich mixture sent from the lean mixture generation section and rich mixture generation section are used to achieve the specified total fuel supply amount. I'm trying to do combustion.

[0007] The control pattern in the region where the total fuel supply amount exceeds the reference value is to keep the fuel supply amount to the lean mixture generating section constant, and to control the amount of fuel supplied to the rich mixture generating section according to changes in the total fuel supply amount. A type that changes the amount of fuel supplied to the lean mixture generating section and a rich mixture generating section depending on the total fuel supply amount. It is possible to limit the supply amount, etc. The air suction ratio of the rich mixture is selected to be a value that allows stable combustion throughout the adjustment range of the total fuel supply amount.
The air suction ratio of the lean mixture is selected so that it can be combusted under the flame-holding effect of the combustion flame of the rich mixture.

[0008] Furthermore, when the total fuel supply amount increases and exceeds a reference value, the fuel supply amount to the rich mixture generation section is reduced a short time after the start of fuel supply to the lean mixture generation section. If the total fuel supply amount decreases to below the reference value, the amount of fuel supplied to the rich mixture generation section will be increased after a short period of time after the fuel supply to the lean mixture generation section is stopped. It consists of

[0009]

[Operation] In a region where the total fuel supply amount is less than the reference value, normal premix combustion is performed in which secondary air is supplied, so the stable combustion region is wide and it is easy to reduce the minimum input amount Ismin. In addition, in the region exceeding the reference value, the fuel supply amount to the rich mixture generation section decreases as fuel supply to the lean mixture generation section starts, and the predetermined total fuel supply amount is maintained as a whole, and the lean mixture generation section starts to supply fuel. Since the air-fuel mixture burns without any problem due to the flame holding caused by the combustion of a rich air-fuel mixture, the maximum input amount Ism
ax can be increased.

[0010] Furthermore, at the time of combustion switching when the total fuel supply amount increases and exceeds the reference value and the supply of a lean mixture is started, the reduction in the fuel supply amount to the rich mixture generation section is delayed for a short period of time. Flame action is ensured and combustion of the lean mixture starts smoothly. Furthermore, when the total fuel supply amount decreases to below the standard value, the supply of lean mixture stops and the supply amount of rich mixture increases.At the time of combustion switching, the amount of fuel supplied to the rich mixture generation section is increased. The occurrence of poor combustion can be prevented by delaying for a minute time.

[0011]

[Embodiment] Next, the illustrated embodiment will be explained. FIG. 1 is a schematic diagram showing the configuration of a first embodiment corresponding to the invention of claims 1 and 2. In the figure, 1 is a mixer for producing a rich mixture, 2 is a mixer for producing a lean mixture, and 3 is a mixer for producing a lean mixture. is a fuel supply source, 4 is a blower, 5R is a fuel control valve, 5S is a fuel on-off valve,
6 is a control section, 7 is a fire power adjustment member, and 8 is a burner section.

For example, gas fuel is supplied to the mixer 1 through a fuel control valve 5R, and to the mixer 2 through a fuel on-off valve 5S, and is mixed with air sent from the blower 4 to form an air-fuel mixture with a desired concentration. The air suction ratio of the rich mixture obtained by mixer 1 is, for example, 40 to 100%, and the air suction ratio of the lean mixture obtained by mixer 2 is, for example, 100% or more. has been done. The mixtures of the mixers 1 and 2 are sent to the burner section 8 to be burned.
It has a structure in which the flame hole portions 8b for a lean mixture are arranged alternately. Further, the fuel supply amount is adjusted by controlling the fuel control valve 5R by the control unit 6 in accordance with the operation of the thermal power adjustment member 7, and the air supply amount is adjusted by the control unit 6 in accordance with the fuel supply amount.
It is configured to be controlled by

Next, the operation will be explained with reference to FIG. The horizontal axis shows the input amount Is, where Is1 is the amount of fuel supplied in a rich mixture, Is2 is the amount of fuel supplied in a lean mixture, Ito
tal indicates the total fuel supply amount. The total fuel supply amount (=total input amount) changes as shown in FIG. Iso is a reference value that is set to an appropriate value in advance, and in the area below this reference value Iso, as shown in (b) in the figure.
As shown in (C), the fuel on-off valve 5S is closed so that no fuel is supplied to the mixer 2, and only the mixer 1 is supplied with fuel regulated by the fuel control valve 5R.

Further, in the region where the total fuel supply amount exceeds the reference value Iso, the fuel on-off valve 5S is opened and a constant amount of fuel is supplied to the mixer 2 as shown in FIG. Fuel is supplied by subtracting the amount of fuel supplied to the mixer 2 from the fuel supply amount, and the total fuel supply amount is controlled to be maintained at a predetermined value as a whole. As shown in (a) of the figure, the total air supply amount increases or decreases according to the adjustment of the input amount,
More air is supplied to mixer 2 than to mixer 1, distributed in a constant ratio. In the figure, A1 is the air supply amount in a rich mixture, A2 is the air supply amount in a lean mixture, Atotal
respectively indicate the total air supply amount.

That is, in the area below the reference value Iso,
Mixer 1 supplies a rich air-fuel mixture to burner section 8, mixer 2 supplies only air to burner section 8, and combustion is performed in a normal premixed combustion state in which secondary air is supplied. In addition, in the region exceeding the reference value Iso, the rich mixture from mixer 1 and the lean mixture from mixer 2 are supplied to the burner section 8, and the lean mixture is combusted while being flame-holding by the combustion of the rich mixture. It becomes a state where In this way, in the region below the reference value Iso, it is normal premixed combustion with a wide stable combustion range, so it is easy to reduce the minimum input amount Ismin, and in the region exceeding the reference value Iso, it is possible to reduce the lean mixture. Since the combustion method uses a combination of a rich mixture and a rich mixture, the maximum input amount Ismax is
This makes it possible to obtain a combustion device that has a wide adjustment range of thermal power, is easy to use, maintains a proper combustion state, and emits less NOx, etc.

Next, a modification of the above embodiment will be explained with reference to FIGS. 3 to 6. In the embodiment described above, the mixers 1 and 2 are made independent and fuel and air are supplied separately, and the air is distributed at a fixed ratio to each mixer 1 and 2 at the time of combustion switching with the reference value Iso as the boundary. The amount of air supplied to 2 does not change. Therefore, in the region exceeding the standard value Iso, the amount of fuel supplied to mixer 1 decreases, and the air suction ratio of the relatively rich mixture becomes quite high, causing a large change in the combustion state and making combustion unstable. .

FIGS. 3 and 4 show an improvement on this, in which the mixer 1 for producing a rich mixture has a structure in which a Venturi tube 1a is provided in the mixer 2 and a nozzle 1b is combined with this. Therefore, when the amount of air sucked into the venturi pipe 1a changes according to the change in the amount of fuel injected from the nozzle 1b, and the fuel on-off valve 5S opens and the amount of fuel injected from the nozzle 1b decreases, the amount of air injected from the nozzle 1b decreases. As shown in a), the amount of air A1 in the rich mixture also decreases, the increase in the air suction ratio is alleviated, and changes in the combustion state are suppressed, thereby preventing combustion from becoming unstable ( (corresponding to the invention of claim 4). At this time, the air amount A2 in the lean mixture increases slightly.

Furthermore, in this embodiment, the fuel control valve 5R is arranged upstream of the branch point of the fuel supply path, so that the amount of fuel supplied not only for rich mixtures but also for lean mixtures is adjusted according to the input amount. This suppresses fluctuations in the air suction ratio of each mixture depending on the input amount, and the change in the amount of fuel in the rich mixture becomes gradual, which also prevents combustion from becoming unstable. (corresponding to the invention of claim 3). In addition, as shown in FIG. 5, the fuel control valve 5R can be placed on the nozzle 1b side downstream from the branch point. In this case, as shown in FIG. 6, the amount of fuel in the lean mixture is constant and the reference value In the region exceeding Iso, the air amount A1 in the rich mixture is reduced and the air suction ratio is prevented from increasing (corresponding to the invention of claim 4). In this way, the reference value Is
There are several types of control patterns in the area beyond o.
Appropriate combinations are possible.

By the way, when switching combustion around the standard value Iso, if the increase/decrease in the amount of fuel in the rich mixture and the start or stop of fuel supply to generate a lean mixture are performed simultaneously and instantaneously, the standard value Iso can be changed. If the input amount is suddenly increased from below the standard value to above the standard value, the amount of fuel in the rich mixture will suddenly decrease before the lean mixture starts to burn, causing the flame holding effect of the rich mixture to fail. If this happens, the lean air-fuel mixture will not be able to start combustion smoothly, resulting in an unstable combustion state. On the other hand, if the input amount is suddenly reduced to below the reference value, the rich mixture increases rapidly before the lean mixture is combusted and exhausted, which tends to cause temporary combustion failure. FIG. 7 shows changes in the fuel supply amounts Is1 and Is2 in the rich mixture and lean mixture in such a case.

In order to solve this problem, it is effective to delay the change in the fuel supply amount Is1 in the rich mixture by a minute time as shown in FIGS. 8 and 9 (corresponding to the inventions of claims 5 and 6). Figure 8 shows the case where the total fuel supply amount rapidly exceeds the reference value Iso, and as shown in (a), combustion switching is performed at time t0, and the fuel supply amount Is2 in the lean mixture starts to be supplied immediately. On the other hand, the fuel supply amount Is1 in the rich mixture decreases with a delay of a minute time T. Generally, even after a predetermined amount of fuel is supplied to the mixer, it takes some time for the air-fuel mixture to reach the burner, so the above delay time T must be set appropriately taking this delay in arrival into account. Bye. As a result, the flame-holding effect of the combustion flame of the rich air-fuel mixture is sufficiently performed, and the combustion of the lean air-fuel mixture starts smoothly.

[0021] Immediately after time T, the total fuel supply amount Ito
Although tal temporarily exceeds a predetermined value, since it is for a short time, the effect on heat output is so small as to be almost negligible. However, if, for example, the fuel supply amount Is1 is decreased in stages as shown in FIG. 8(b), the total fuel supply amount Ito
The peak value of tal is suppressed, and fluctuations in heat output are reduced, and flame-holding effect can also be ensured, allowing smooth combustion switching. Alternatively, the fuel supply amount Is1 may not be changed instantaneously, but may be changed gradually as shown by the broken line.

FIG. 9 shows that the total fuel supply amount suddenly decreases to the reference value Is.
In this case, the combustion switching is performed at time t0' and the fuel supply amount Is2 immediately becomes zero, but the fuel supply amount Is1 increases with a delay of a minute time T'. This prevents the occurrence of poor combustion due to supply of rich air-fuel mixture before lean air-fuel mixture is combusted and exhausted. The delay time T' may be appropriately set in consideration of the time required for combustion and exhaust of the lean mixture. It should be noted that each of the above embodiments can be implemented alone or in combination as appropriate depending on the purpose, the user's wishes, etc.

[0023]

Effects of the Invention As is clear from the above-described embodiments, the present invention provides a combustion device that burns a combination of a lean mixture and a rich mixture, in which the total fuel supply amount is less than the reference value. Normal premix combustion using air is performed, and in areas where the standard value is exceeded, a rich mixture and a lean mixture are combusted, respectively. Therefore, it is easy to reduce the minimum input amount and increase the maximum input amount, and it is possible to obtain a combustion device that has a wide range of thermal power adjustment, has stable combustion, and is easy to use. This has the advantage that fewer control valves are required to adjust the flow rate, resulting in a simpler structure and easier control.

Furthermore, in the region exceeding the reference value, the amount of fuel supplied to the lean mixture and the amount of fuel supplied to the rich mixture are changed according to the total amount of fuel supplied, or the amount of air supplied to the rich mixture is changed. By restricting the amount, a more stable combustion state can be achieved. Additionally, if the total fuel supply amount increases beyond the standard value or decreases below the standard value,
A system that allows a small time delay to decrease or increase the amount of fuel supplied to a rich mixture prevents the unstable state that tends to occur when switching combustion states and makes combustion more stable. Become.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of the operation of the same embodiment.

FIG. 3 is a schematic diagram of main parts showing the configuration of a modified example of the same embodiment.

FIG. 4 is an explanatory diagram of the operation of the modified example.

FIG. 5 is a schematic diagram of main parts showing the configuration of another modified example of the same embodiment.

FIG. 6 is an explanatory diagram of the operation of the modified example.

FIG. 7 is a diagram showing changes in the amount of fuel supplied in a rich mixture and a lean mixture in the same embodiment.

FIG. 8 is an explanatory diagram of the operation of another embodiment.

FIG. 9 is an explanatory diagram of the operation of another embodiment.

FIG. 10 is a schematic diagram of main parts of a conventional example.

[Explanation of symbols]

1, 2 Mixer 3 Fuel supply source 4　Blower 5R Fuel control valve 5S Fuel on/off valve 6 Control section 7 Firepower adjustment member 8 Burner part Iso standard value Is1 Fuel supply amount in rich mixture Is2 Fuel supply amount in lean mixture Itotal Total fuel supply amount A1 Air supply amount in rich mixture A2 Air supply amount in lean mixture Atotal Total air supply amount

Claims (6)

[Claims] 1. A lean mixture generation section that is adjusted to generate a lean mixture with a high air suction ratio, and a rich mixture generation section that is adjusted to generate a rich mixture with a low air suction ratio. , an air supply section configured to adjust the total air supply amount according to the total fuel supply amount, and in a region where the total fuel supply amount is less than a preset reference value, a lean mixture is generated. The fuel supply to the fuel mixture generator is stopped, and the rich mixture sent from the rich mixture generation section and the air sent from the lean mixture generation section are used for combustion. A combustion device characterized in that combustion is performed at a predetermined total fuel supply amount using a lean mixture and a rich mixture sent from a gas generation section and a rich mixture generation section, respectively. [Claim 2] In a region where the total fuel supply amount exceeds the reference value, the fuel supply amount to the lean mixture generation section is kept constant, and the fuel supply amount to the rich mixture generation section is adjusted according to changes in the total fuel supply amount. The combustion device according to claim 1, wherein the combustion device is configured to vary. [Claim 3] In a region where the total fuel supply amount exceeds a reference value, the fuel supply amount to the lean mixture generation section and the rich mixture generation section is changed in accordance with the total fuel supply amount. The combustion device according to item 1. 4. The combustion apparatus according to claim 2, wherein the combustion apparatus is configured to limit the amount of air supplied to the rich mixture generating section in a region where the total amount of fuel supplied exceeds a reference value. [Claim 5] When the total fuel supply amount increases and exceeds a reference value, the fuel supply amount to the rich mixture generation section is reduced a short time after the start of fuel supply to the lean mixture generation section. A combustion device according to any one of claims 1 to 4 configured. [Claim 6] When the total fuel supply amount decreases to below a reference value, the fuel supply amount to the rich mixture generation section is increased after a short time after the fuel supply to the lean mixture generation section is stopped. The combustion device according to any one of claims 1 to 5, configured to:.