JP2769586B2 - Combustion equipment - Google Patents

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 premixing type combustion device.

[0002]

2. Description of the Related Art There is known a combustion apparatus in which a flame port for supplying a lean air-fuel mixture having a large air suction ratio and a flame port for supplying a rich air-fuel mixture having a small air suction ratio are provided (for example, Japanese Patent Laid-Open Publication No. HEI 9 (1994)). 1-2-219406). FIG. 10 is a schematic diagram showing the configuration of the air-fuel mixture generation unit of such an apparatus. A
Is a mixing section for generating a rich mixture, B is a mixing section for generating a lean mixture, C is a gas supply source, D is a blower, E ₁ and E ₂ are gas control valves, F ₁ and F ₂ are air control valves. And each mixing section A,
In B, the fuel flow rate and the air flow rate are adjusted by the respective valves so as to obtain a mixture having a desired concentration.

[0003] In an actual combustion apparatus, when the thermal power is reduced, it is advantageous to reduce the total amount of air supply in accordance with the thermal power.
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 time of the minimum heating power is generally selected to be larger than that at the time of the maximum heating power. Therefore, for example, the air amount is adjusted so that the exhaust amount is the same at the time of the maximum thermal power and at the time of the minimum thermal power, and the ratio of the input amount Ismax at the maximum thermal power and the input amount Ismin at the minimum thermal power is 5/1. Then, the air suction ratio at the time of the minimum heating power is five times that at the time of the maximum heating power.

[0004] However, such a fuel concentration is too lean, so that even if flame holding is performed by burning a rich mixture, the combustion cannot be maintained. Also on the rich mixture side, the change in the air suction ratio accompanying the thermal power adjustment is a problem as well, and as a result,
Ratio of maximum input amount Ismax and minimum input amount Ismin
(TDR) could not be increased so much, and it was difficult to obtain a combustion device having a wide range of thermal power adjustment. Further, as shown in the figure, it is necessary to individually adjust the fuel and the air using four control valves, which complicates the structure and complicates the control.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such a point, and an object of the present invention is to provide a combustion apparatus having a wide range of thermal power adjustment and easy to use with a relatively simple configuration.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a lean air-fuel mixture generating section adjusted to generate a lean air-fuel mixture having a large air suction ratio, and a low air suction ratio. A rich mixture generation unit adjusted to generate a rich mixture, and an air supply unit configured to adjust the total air supply amount according to the total fuel supply amount,
In a region where the total fuel supply amount is equal to or less than a preset reference value, the fuel supply to the lean mixture generation unit is stopped, and the rich mixture sent from the rich mixture generation unit and the air sent from the lean mixture generation unit are stopped. In the region where the total fuel supply exceeds the reference value, the lean mixture and the rich mixture sent from the lean mixture generation unit and the rich mixture generation unit respectively perform the combustion at a predetermined total fuel supply amount. Combustion is performed.

The control pattern in a region where the total fuel supply amount exceeds the reference value is such that the fuel supply amount to the lean mixture generation unit is fixed, and the rich mixture generation unit is controlled according to the change in the total fuel supply amount. Or the fuel supply amount to the lean mixture generation unit and the rich mixture generation unit according to the total fuel supply amount, and the air supply to the rich mixture generation unit It is possible to limit the supply amount. In addition, the air suction ratio of the rich mixture is selected to be a value that enables stable combustion over the entire adjustment range of the total fuel supply amount.
The air suction ratio of the lean air-fuel mixture is selected so that the lean air-fuel mixture can be burned by the flame holding action of the combustion flame of the rich air-fuel mixture.

Further, when the total fuel supply amount exceeds the reference value and increases, the fuel supply amount to the rich mixture generation unit is reduced after a short time from the start of fuel supply to the lean mixture generation unit. In the case where the total fuel supply amount is reduced to be equal to or less than the reference value, the fuel supply amount to the rich mixture generation unit is increased after a short time of stopping the fuel supply to the lean mixture generation unit. Make up.

[0009]

In the region where the total fuel supply amount is equal to or less than the reference value, normal premix combustion in which the secondary air is supplied is performed, so that the stable combustion region is wide, and it is easy to reduce the minimum input amount Ismin. Further, in the region exceeding the reference value, the fuel supply amount to the rich mixture generation unit decreases with the start of the fuel supply to the lean mixture generation unit, and a predetermined total fuel supply amount is maintained as a whole, Since the air-fuel mixture burns without hindrance by flame holding due to the combustion of the rich air-fuel mixture, the maximum input amount Ismax can be increased.

Further, at the time of combustion switching in which the supply of the lean mixture is started when the total fuel supply amount exceeds the reference value and increases, the decrease in the fuel supply amount to the rich mixture generation section is maintained by delaying for a short time. The flame action is ensured, and the combustion of the lean mixture is started smoothly. Further, at the time of combustion switching in which the total fuel supply amount decreases to become equal to or less than the reference value and the supply of the lean mixture is stopped to increase the supply amount of the rich mixture, the fuel supply amount to the rich mixture generation unit is increased. By delaying for a minute time, occurrence of poor combustion is prevented.

[0011]

Next, an embodiment shown in the drawings will be described. FIG. 1 is a schematic diagram showing the configuration of an embodiment according to the first aspect of the present invention. In FIG. 1, reference numeral 1 denotes a mixer for generating a rich mixture, 2 denotes a mixer for generating a lean mixture, and 3 denotes a fuel supply source. Reference numeral 4 denotes a blower, 5R denotes a fuel control valve, 5S denotes a fuel opening / closing valve, 6 denotes a control unit, 7 denotes a thermal power control member, and 8 denotes a burner unit.

For example, gas fuel is supplied to the mixer 1 via a fuel control valve 5R and to the mixer 2 via a fuel opening / closing valve 5S, respectively, and is mixed with air supplied from the blower 4 to form a mixture of a desired concentration. The air suction ratio of the rich mixture obtained by the mixer 1 is, for example, 40 to 100%, and the air suction ratio of the lean mixture obtained by the mixer 2 is, for example, 100% or more. Have been. The air-fuel mixture of each of the mixers 1 and 2 is sent to the burner section 8 and burned.
And the flame holes 8b of the lean mixture are arranged alternately. Further, the fuel supply amount is adjusted by controlling the fuel control valve 5R by the control unit 6 according to the operation of the thermal power adjusting member 7, and the air supply amount is controlled by the control unit 6 according to the fuel supply amount.
It is configured to be controlled by.

Next, the operation will be described with reference to FIG. The abscissa indicates the input amount Is, Is1 indicates the fuel supply amount in the rich mixture, Is2 indicates the fuel supply amount in the lean mixture, and Itotal indicates the total fuel supply amount. Total fuel supply (=
(Total input amount) changes as shown in (d) of the figure according to the adjustment of the input amount accompanying the operation of the thermal power adjusting member 7. Iso
Is a reference value set in advance to an appropriate value. In a region equal to or less than the reference value Iso, the fuel on-off valve 5S is closed and fuel is supplied to the mixer 2 as shown in FIGS. Instead, the fuel adjusted by the fuel adjustment valve 5R is supplied only to the mixer 1.

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

That is, in the region equal to or lower than the reference value Iso, the rich air-fuel mixture is supplied from the mixer 1 and only the air is supplied from the mixer 2 to the burner section 8, and the secondary air is supplied to the normal premix combustion. Combustion is performed in the state. The reference value I
In the region beyond so, the rich mixture from the mixer 1 and the lean mixture from the mixer 2 are supplied to the burner unit 8, and the lean mixture burns while being subjected to the flame holding action by the combustion of the rich mixture. Become. As described above, in the region equal to or less than the reference value Iso, since the stable combustion region is normal premixed combustion, it is easy to reduce the minimum input amount Ismin.
In the region exceeding the reference value Iso, the combustion system is a combination of a lean mixture and a rich mixture, so that the maximum input amount Ismax can be increased while maintaining a stable combustion state, and the range of adjustment of the thermal power is wide. This makes it possible to obtain a combustion device that is easy to burn and that maintains a proper combustion state and emits a small amount of NOx and the like.

[0016] Next to the second aspect of the present invention with reference to FIG. 3 through FIG. 6
A corresponding embodiment and its modification will be described. In the above-described embodiment, the mixers 1 and 2 are independently supplied to supply the fuel and the air separately, and the air is distributed at a fixed ratio and the respective mixers 1 and 2 are switched at the time of combustion switching with the reference value IS0 as a boundary. The air supply to 2 does not change. For this reason, in a region exceeding the reference value IS0, the amount of combustion supplied to the mixer 1 decreases, and the air suction ratio of the rich mixture becomes relatively high.
The combustion state changes greatly and the combustion tends to be unstable.

FIG. 3 and FIG. 4 show an improvement of this. The mixer 1 for producing a rich mixture has a structure in which a venturi tube 1a is provided in a mixer 2 and a nozzle 1b is combined therewith. Accordingly, when the amount of air sucked into the venturi pipe 1a changes in accordance with the change in the amount of fuel injected from the nozzle 1b, and the fuel opening / closing valve 5S is opened to reduce the amount of fuel injected from the nozzle 1b, (FIG. 4) As shown in a), the air amount A1 in the rich mixture is also reduced, the increase in the air suction ratio is moderated, the change in the combustion state is suppressed, and the combustion is prevented from becoming unstable. ( Corresponding to the invention of claim 3 ). At this time, the air amount A2 in the lean mixture slightly increases.

Further, in this embodiment, the fuel control valve 5R is disposed upstream of the branch point of the fuel supply path, so that not only the rich mixture but also the fuel supply amount in the lean mixture is adjusted according to the adjustment of the input amount. The air suction ratio of each mixture is suppressed from fluctuating due to the input amount, and the change in the fuel amount in the rich mixture is also moderated, which also prevents combustion instability from this point. (Corresponding to the invention of claim 2 ). Note that the fuel control valve 5R can be disposed on the nozzle 1b side downstream of the branch point as shown in FIG. 5, in which case the fuel amount in the lean mixture becomes constant as shown in FIG. In the region exceeding IS0, the air amount A1 in the rich mixture is prevented from decreasing and the air suction ratio is prevented from increasing (corresponding to the invention of claim 3 ). Thus, the reference value IS
There are several types of control patterns in the region beyond 0,
Appropriate combinations are possible.

By the way, at the time of combustion switching with the reference value Iso as a boundary, if the increase and decrease of the fuel amount in the rich mixture and the start or stop of the fuel supply for generating the lean mixture are performed simultaneously and instantaneously, If the input amount is suddenly increased from the value below the standard value to the amount exceeding the reference value, the amount of fuel in the rich mixture sharply decreases before the lean mixture starts to burn, so the flame holding effect of the rich mixture is not sufficient. It becomes sufficient, and the lean air-fuel mixture cannot start combustion smoothly, and is likely to cause an unstable combustion state. On the other hand, when the input amount is suddenly decreased to the reference value or less, the rich mixture rapidly increases before the lean mixture is burned and exhausted. FIG. 7 shows a change state of the fuel supply amounts Is1, Is2 in the rich mixture and the lean mixture in such a case.

In order to solve this problem, it is effective to delay the change of the fuel supply amount IS1 in the rich mixture for a short time as shown in FIGS. 8 and 9 (corresponding to the inventions of claims 4 and 5 ).
FIG. 8 shows a case where the total fuel supply amount suddenly increases and exceeds the reference value IS0. As shown in FIG. 8A, the combustion is switched at time to, and the supply of the fuel supply amount IS2 in the lean mixture starts immediately. On the other hand, the fuel supply amount IS1 in the rich mixture decreases with a delay of the minute time T. In general, even when the supply of a predetermined amount of fuel to the mixer is started, it takes some time for the air-fuel mixture to reach the burner section. Therefore, the above-mentioned delay time T may be appropriately set in consideration of the arrival delay or the like. I just need. Thereby, the flame holding action by the combustion flame of the rich mixture is sufficiently performed, and the combustion of the lean mixture is started smoothly.

Immediately after time t0 , the total fuel supply amount It
Although the total temporarily exceeds a predetermined value, the effect on the heat output is so small that it is almost negligible because of a short time.
However, if the fuel supply amount Is1 is reduced stepwise, for example, as shown in FIG. 8B, the total fuel supply amount It1
The peak value of the total is suppressed, the fluctuation of the heat output is reduced, and the flame holding effect can be secured, so that the combustion can be switched smoothly. Further, the fuel supply amount Is1 may be changed gradually as shown by a broken line without being changed instantaneously.

FIG. 9 shows that the total fuel supply amount is rapidly reduced and the reference value Iso is increased.
The combustion switching is performed at time t ₀ ′, and the fuel supply amount Is2 immediately becomes zero.
s1 increases with a delay of the minute time T '. This prevents the occurrence of poor combustion due to the supply of the rich mixture before the lean mixture is burned and exhausted. The delay time T 'may be appropriately set in consideration of the time required for combustion and exhaust of the lean mixture. Each of the above embodiments can be implemented alone or in combination as appropriate according to the application, the user's desire, and the like.

[0023]

As is apparent from the above embodiment, the present invention relates to a combustion apparatus for combusting a lean air-fuel mixture and a rich air-fuel mixture in a region where the total fuel supply amount is below a reference value. Normal premixed combustion with air is performed, and in a region exceeding the reference value, a rich mixture and a lean mixture are burned, 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 thermal power adjustment range, is stable in combustion, and is easy to use. There is an effect that the required number of control valves for adjusting the pressure is small, the structure is simple and the control is easy.

Further, in the region exceeding the reference value, the fuel supply amount in the lean mixture and the fuel supply amount in the rich mixture are respectively changed according to the total fuel supply amount, or the air supply amount in the rich mixture is changed. By limiting, a more stable combustion state can be achieved. Also, if the total fuel supply increases above the reference value or decreases below the reference value,
With a small time delay in decreasing or increasing the amount of fuel supplied to the rich mixture, it is possible to prevent unstable states that are likely to occur when switching the combustion state, and to stabilize combustion. Become.

[Brief description of the drawings]

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

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

FIG. 3 is a schematic diagram of a main part showing a configuration of an embodiment of the second invention .

FIG. 4 is an operation explanatory diagram of the embodiment .

FIG. 5 is a schematic diagram of a main part showing a configuration of another modification of the embodiment.

FIG. 6 is an operation explanatory diagram of the modification.

FIG. 7 is a diagram showing a change state of a fuel supply amount in a rich mixture and a lean mixture in the embodiment.

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

FIG. 9 is an operation explanatory view of another embodiment.

FIG. 10 is a schematic view of a main part 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 unit 7 thermal power control member 8 burner unit Iso reference value Is1 fuel supply amount in rich mixture Is2 fuel supply amount in lean mixture Itotal Total fuel supply A1 Air supply in rich mixture A2 Air supply in lean mixture Atotal Total air supply

Claims (5)

(57) [Claims] 1. A lean air-fuel mixture generation unit adjusted to generate a lean air-fuel mixture with a large air suction ratio, and a rich air-fuel mixture generation unit adjusted to generate a rich air-fuel mixture with a small air suction ratio. An air supply unit configured to adjust the total air supply amount according to the total fuel supply amount, and in an area where the total fuel supply amount is equal to or less than a preset reference value,
A region in which the fuel supply to the lean mixture generation unit is stopped and combustion is performed by the rich mixture sent from the rich mixture generation unit and the air sent from the lean mixture generation unit, and the total fuel supply amount exceeds the reference value. Is a combustion device that performs combustion at a predetermined total fuel supply amount with a lean mixture and a rich mixture sent from a lean mixture generation unit and a rich mixture generation unit, respectively.
Therefore, in the region where the total fuel supply exceeds the reference value,
Keeping the fuel supply to Naribe constant, and changing the total fuel supply
Fuel supply to the rich mixture generator
Combustion apparatus characterized by configured. 2. A lean air-fuel mixture having a large air suction ratio is generated.
And the air suction ratio
A rich mixture conditioned to produce a small rich mixture
Adjust the total air supply according to the component and the total fuel supply
An air supply configured so that the total fuel
In the area where the supply amount is below the preset reference value,
Stop fuel supply to the lean mixture generation section to generate a rich mixture
From the rich / lean mixture generation section
Combustion is performed by the discharged air, and the total fuel supply
In the region exceeding the reference value, the lean mixture generation section and the rich mixture
Lean and rich mixtures sent from the generator
Combustion device that performs combustion with a predetermined total fuel supply amount
Therefore, in a region where the total fuel supply amount exceeds the reference value, the fuel supply amount to the lean mixture generation unit and the rich mixture generation unit is calculated as the total fuel supply amount .
Characteristically configured to change according to each
And combustion equipment. 3. In a region where the total fuel supply exceeds a reference value.
The combustion device according to claim 1 or 2 , wherein the combustion device is configured to limit an amount of air supplied to the rich mixture generation unit. 4. The total fuel supply increases and exceeds a reference value.
In the case, the minute time of the start of fuel supply to the lean mixture generation unit
Combustion device according to any one after the amount of fuel supplied to the dense mixture generator configured to cause reduced little of the claims 1 to 3. 5. The total fuel supply amount decreases to a value below a reference value.
When Tsu, combustion apparatus according to any one of claims 1 to 4 which is configured to increase the amount of fuel supplied to the dense mixture generator after short time of stopping fuel supply to the lean generator .