JP2001201011A - LOW NOx COMBUSTION DEVICE - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low NOx formation and assure a variable range of combustion amount by increasing a combustion rate of lean flame or by further making lean concentration of the lean flame. SOLUTION: There are provided a lean flame port 12 communicated with a lean gas chamber 11 for supplying lean mixture gas; a first flame port 14 communicated with a first mixture gas chamber 13 adjacent to the lean gas chamber 11 and adjacent to the lean flame port; and a second flame port 17 communicated with a second mixture gas chamber 16 adjacent to the first mixture gas chamber 13 and arranged adjacent to the first flame port 14. A concentration of the first mixture gas chamber 13 is made thicker than that of the second mixture gas chamber 16, and flow rates of the lean mixture gas, the first mixture gas and the second mixture gas can be increased or decreased under the same rate. With such an arrangement as above, even if 'the high temperature and high reaction region' where an active combustion reaction is attained increases or decreases the amount of combustion, it may always be formed. Thus, a concentration of the lean mixture gas is decreased to enable an ultra-low NOx formation to be attained and at the same time, it is possible to keep a high variable range of combustion amount maintaining a superior combustion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-NOx combustion apparatus mainly used in domestic or commercial combustion apparatuses, in particular, in which exhaust gas NOx is significantly reduced to achieve cleanliness.

[0002]

2. Description of the Related Art A conventional low NOx combustion apparatus of this type is generally the first one described in Japanese Patent Application Laid-Open No. 1-219406. The low NOx combustion device includes a light burner that supplies a lean air-fuel mixture into a combustion chamber,
The burners are arranged so as to alternately supply rich burners for supplying a rich air-fuel mixture to both sides of the light burners.

[0003] The lean mixture supplied from the lean burner has a low flame temperature in the combustion chamber and thus has low NOx, but itself forms an unstable lean flame. The rich mixture supplied from the rich burner has a high flame temperature in the combustion chamber and therefore high NOx, but forms a stable rich flame by supplying thermal energy to the adjacent lean flame to promote the combustion reaction. As a whole, a so-called lean-burn combustion is realized. Then, the combustion ratio of the light burner is set to be larger than that of the rich burner, and the NOx is reduced as a whole.

[0004] As a second example, Japanese Patent Publication No. 57-12923 discloses an all-primary type combustion apparatus in which the concentration of an air-fuel mixture is changed stepwise to reduce NOx. In this apparatus, as shown in FIG. 9, the lean mixture chamber 3 is communicated from the central flame opening 1 to the peripheral flame opening 2 through the communication port 4, and the fuel is gradually supplied to the lean mixture chamber 3 so as to supply the fuel. It is configured to gradually increase the concentration of the air-fuel mixture. Then, the ultra-lean flame formed at the central flame opening 1 is stabilized to some extent by a peripheral flame having a relatively high concentration, and is stabilized by a lean flame having a gradually increasing concentration.
x combustion is realized.

[0005] As a third example, a rich flame outlet 9 is used in the light and shade combustion.
Japanese Unexamined Patent Publication No. 6-307610 discloses a low-NOx concentration-type combustion apparatus in which the supply of fuel gas supplied to the gas outlet 10 is kept constant and the amount of fuel gas supplied to the light-portion flame opening 10 is reduced. ing. As shown in FIG. 10, this device has a structure in which a fuel gas passage 5 is branched, and one of the fuel gas passages 5 is communicated with a dense nozzle 6 and the other is communicated with a light nozzle 8 via a proportional valve 7. When the combustion amount is varied, the fuel supplied to the lean portion is increased or decreased according to the opening of the proportional valve. For this reason, the combustion of the rich portion is constant, the ratio of the rich flame is increased, and the generation of unburned gas COHC can be prevented in order to maintain a good flame holding effect of the light flame.

[0006]

However, in the low NOx combustion apparatus of the first conventional example, the lean flame is stabilized by the thermal energy of the rich flame.
If the burn rate of the rich burner is reduced, the lean flame becomes unstable, and there is a problem that there is a limit in increasing the burn rate of the lean mixture and further reducing NOx.

The low N in the second example shown in FIG.
In the Ox combustion device, a lean flame that performs all primary combustion is formed in both the central flame opening 1 and the peripheral flame opening 2, and is effective for stabilizing a lean flame such as a rich flame in the lean combustion. Since there is no means, a very delicate balance of fuel and air supply is required, and therefore, the configuration of the communication port 4 also requires high-precision processing. In addition, high-speed, high-precision air and fuel flow control was required.

Further, there is a problem that a variable adjustment range of the combustion amount is small because an unstable lean flame is formed by all the primary combustion, and it is difficult to cope with a high-speed change of the combustion amount because the fuel supply balance is easily lost. I was

Further, in the low NOx combustion apparatus of the third example shown in FIG. 10, in order to stabilize the combustion state when the combustion amount is small, the supply of the fuel gas supplied to the rich flame port in the lean combustion is made constant. The amount of fuel gas to be supplied to the end flame opening is changed, and the combustion in the rich portion is constant, the ratio of the rich flame increases, and the unburned gas COHC to maintain the flame holding effect of the light flame satisfactorily.
However, since the basic form of combustion is rich-lean combustion and the lean flame is stabilized by the thermal energy of the rich flame, the lean flame becomes unstable when the burn rate of the rich burner is reduced, There is a similar problem that there is a limit in increasing the combustion ratio of a lean mixture to further reduce NOx, and there is a limit in further increasing the combustion ratio of a lean flame to further reduce NOx. Was.

As described above, in the conventional combustion apparatus, the concentration of the air-fuel mixture changes stepwise, monotonously, and becomes thinner toward the central flame opening. Therefore, there is a limit to increasing the burning rate of the lean flame and further reducing the concentration of the lean flame in order to further reduce NOx.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a lean flame port which communicates with a lean chamber and supplies a lean mixture to a combustion chamber, and a first lean chamber adjacent to the lean chamber. A first flame port provided in communication with the lean flame port, and a second gas port provided in proximity to the first flame port in communication with a second mixture chamber adjacent to the first mixture chamber; Having a flame opening, making the concentration of the first mixture chamber higher than the concentration of the second mixture chamber, and increasing and decreasing the flow rates of the lean mixture, the first mixture, and the second mixture at the same rate. It is the structure which did.

As a result of a detailed investigation of the flame base structure that determines the stability of the lean flame, which is the point of the technical problem, the rich flame that is formed on the second flame port by the above configuration and that is supplied from the first flame port is rich. The mixture is subjected to thermal decomposition, a large amount of chemically active intermediate products are generated, and the mixture is supplied to the base of the lean flame outlet by material diffusion and the combustion reaction is actively performed in the minute space of the base. A "reaction zone" was formed, indicating that the lean flame was stabilized.
As inferred from Hooke's law, which is the basis of material diffusion, the higher the concentration difference between the first mixture chamber and the lean chamber, and the lower the jet flow velocity from the first flame outlet, the higher the temperature and reaction zone. Was found to be easily formed. Further, the rich mixture supplied from the second flame port forms a stable rich flame by itself and promotes the reaction of the lean flame, so that the combustion reaction is completed.

Further, by increasing or decreasing the flow rates of the lean air-fuel mixture, the first air-fuel mixture, and the second air-fuel mixture at the same rate, even when the amount of combustion is increased or decreased, the lean air-fuel mixture ejected from the lean flame and the first air-fuel mixture can be obtained. Since the flow pattern of the spouted mixed gas flows in a similar manner, the concentration difference between the lean mixed gas and the highly mixed gas is maintained,
The substance diffusion from the rich mixed gas toward the lean mixed gas is stably maintained. For this reason, an intermediate product is supplied to the base of the lean flame outlet, and a "high temperature / high reaction zone" in which the combustion reaction is active in the minute space of the base is always formed even if the amount of combustion increases or decreases.

Further, the first mixture, which is a high-concentration mixed gas, is always kept at a constant flow rate, and the flow rates of the lean mixture and the second mixture are increased and decreased at the same rate. Since the flame amount is constant even when the combustion amount is small, the amount of heat is maintained and a stable flame is maintained. Then, the oxygen-deficient flame created by ejecting the high-concentration mixed gas can have the same shape regardless of the amount of combustion. Therefore, a large amount of substance diffusion from the high-concentration gas to the lean gas mixture is maintained even when the combustion amount is small. For this reason, an intermediate product is supplied to the base of the lean flame outlet, and a "high temperature / high reaction zone" in which the combustion reaction is active in the minute space of the base can be stably formed even if the amount of combustion increases or decreases.

Therefore, the combustion ratio of the lean mixture is increased,
Further, since the concentration of the lean air-fuel mixture can be reduced, NOx can be further reduced. In this state, the variable width of the combustion amount can be increased, and stable combustion can be realized by following high-speed fluctuations of air. Such a combustion system that supplies air-fuel mixtures having different concentrations to achieve ultra-low NOx combustion is hereinafter referred to as "multi-concentration combustion" in order to distinguish it from the conventional lean-burn combustion.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Low NOx according to claim 1 of the present invention
The combustion device is provided with a lean flame port communicating with the lean chamber and supplying and supplying a lean air-fuel mixture into the combustion chamber, and a second fuel chamber communicated with a first air-fuel mixture chamber adjacent to the lean chamber and provided in close proximity to the lean flame port. One flame port, having a second flame port provided in close proximity to the first flame port communicating with a second mixture chamber adjacent to the first gas mixture chamber,
By having a configuration in which the concentration of the first mixture chamber is higher than the concentration of the second mixture chamber, and the flow rates of the lean mixture, the first mixture, and the second mixture are increased and decreased at the same rate. Even when the amount of combustion is increased or decreased, the flow pattern of the light mixed gas ejected from the lean flame and the rich mixed gas ejected from the first flame is similar, and the concentration difference between the lean mixed gas and the rich mixed gas is maintained. Therefore, the substance diffusion from the rich mixed gas toward the lean mixed gas is stably continued. For this reason, an intermediate product is supplied to the base of the lean flame outlet, and a "high temperature / high reaction zone" in which the combustion reaction is active in the minute space of the base is always formed even if the amount of combustion increases or decreases. Therefore, the combustion ratio of the lean air-fuel mixture is increased, and the concentration of the lean air-fuel mixture is reduced to achieve an extremely low N.
Oxification can be achieved, and a large variable width of the combustion amount for maintaining good combustion can be secured.

The low NOx combustion apparatus according to claim 2 of the present invention has a structure in which the first mixture is always kept at a constant flow rate and the flow rates of the lean mixture and the second mixture are increased and decreased at the same rate, so that the high-concentration mixed gas is obtained. The flame at the first flame outlet that blows out the gas has a constant amount of combustion even when the amount of combustion is small, so that the amount of heat is maintained and a stable flame is maintained. Then, the oxygen-deficient flame created by ejecting the high-concentration mixed gas can have the same shape regardless of the amount of combustion. Therefore, a large amount of substance diffusion from the high-concentration gas to the lean gas mixture is maintained even when the combustion amount is small. For this reason, an intermediate product is supplied to the base of the lean flame outlet, and a `` high temperature / high reaction zone '' in which the combustion reaction is active in the minute space of the base can be stably formed even if the amount of combustion increases or decreases,
Ultra-low NOx combustion can be realized.

The low NOx combustion apparatus according to the third aspect of the present invention has a configuration in which the flow rate of the lean air-fuel mixture is increased or decreased while always maintaining the first air-fuel mixture and the second air-fuel mixture at constant flow rates. As a result, not only the first flame outlet for ejecting the rich mixed gas but also the second flame outlet for ejecting the rich mixed gas are constant, so that these flames vary in combustion amount and burn even when the combustion amount is small. Since the amount is constant, the calorific value of the flame is maintained at each flame outlet, and a stable flame can be maintained. For this reason, the flame retention of the second flame port of the rich combustion is further improved, and a stable flame is formed.

Therefore, the combustion ratio of the lean mixture is increased,
In addition, since the concentration of the lean air-fuel mixture can be reduced, NOx can be more reliably reduced and the variable range of the combustion amount can be expanded.

In the low NOx combustion apparatus according to a fourth aspect of the present invention, a secondary air passage is provided adjacent to the second flame port, and the flow rates of the secondary air and the lean air-fuel mixture flowing through the secondary air passage are made equal. Has a configuration increased or decreased.

In order to perform low NOx combustion, most of the fuel gas in the combustion amount is burned in a lean flame port, and a minimum small amount of fuel gas necessary for improving flame holding properties and securing a combustion range is obtained. Fuel gas is ejected from the first and second flame ports. For this reason, it is also set when the amount of combustion is changed to the minimum equivalent ratio required for combustion by increasing and decreasing the flow rate of the secondary air and the lean mixture at the same rate, and extra air is supplied to the combustion unit. Therefore, high efficiency and low noise of the equipment can be achieved while securing good combustion.

The low NOx combustion apparatus according to claim 5 of the present invention has a configuration in which the first air-fuel mixture and the second air-fuel mixture are branched and supplied.

In the multi-concentration combustion, the basic structure is such that the first burner port of the highly mixed gas, the second burner port of the rich mixed gas, and the secondary air outside the rich burned gas on both sides of the lean burn. Therefore, the first air-fuel mixture and the second air-fuel mixture are branched and supplied, so that the combustion amount can be varied without time delay, the configuration of the equipment can be simplified, reliability is improved, and cost is reduced. be able to.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is an overall sectional view showing a low NOx combustion apparatus according to Embodiment 1 of the present invention, and FIG. 2 is a partially enlarged view showing a flame formation state of the low NOx combustion apparatus.

In FIG. 1 and FIG. 2, a lean chamber 11 containing a lean air-fuel mixture is connected to a lean flame port 12 in the lean burner 10, and a first air-fuel mixture chamber 1 is provided on both sides of the lean burner 10.
A first burner 15 which includes the first burner 3 and is connected to the first flame port 14 is provided in close contact therewith. Outside the first burner 15, a second burner 18 containing a second air-fuel mixture chamber 16 and connected to a second burner port 17 is similarly provided in close contact with each other.
0 and first burners 15 on both sides thereof and second burners 18 provided on both sides thereof are integrated into a burner block 19.
Is composed. A plurality of the burner blocks 19 are housed in the burner case 20 and are connected to the combustion chamber 21.

A fuel pipe 22 for supplying fuel and a fan 23 for supplying combustion air are provided upstream of the burner case 20.
Is provided. The fuel pipe 22 is provided with a lean mixer 25, a first mixer 26, and a second mixer 2 downstream via a proportional valve 24.
7 and each of the mixers is provided with a branch.
While providing and connecting the lean fuel adjusting means 28, the first fuel adjusting means 29, and the second fuel adjusting means 30 in the fuel system,
On the downstream side of the fan 23, the lean mixer 25 and the first mixer 2
6, a second mixer 27 is provided in a branched manner, and the connection of each mixer is provided with a lean air adjusting means 3 in an air system.
1. The first air adjusting means 32 and the second air adjusting means 33 are connected to the respective mixers via the air mixing means.

The lean mixer 25 and the lean chamber 11 are in a lean passage 34, the first mixer 26 and the first mixture chamber 13 are in a first passage 35, and the second mixer 27 and the second mixture chamber 16 are in a lean passage. They are connected by the second passages 36, respectively. In each passage, branch passages 37 and 3 for supplying each air-fuel mixture to the other burner block 19 are provided.
7 ', 37 ". The first passage 35
And the second passage 36 are branched and connected to the two first mixture chambers 13 and the second mixture chamber 16, respectively.

The air supply system is provided with an air passage 39 connected to the burner case 20 via an air adjusting means 38 in addition to the connection with each mixer. The lean fuel adjusting means 28, the first fuel adjusting means 29, the second fuel adjusting means 30, the lean air adjusting means 31, the first air adjusting means 32, the second air adjusting means 33, and the air adjusting means 38 correspond to the flow resistance of a nozzle or the like. A configuration may be made by setting means to adjust the flow distribution of each passage, or a means for switching according to the flow rate due to a change in combustion amount by adding an electromagnetic valve or the like may be provided. The fan 23 and the proportional valve 24 are electrically connected to the control unit 40 and control so as to supply a required air amount and a fuel amount according to the variable amount of the combustion amount.

Next, the operation and action will be described. The fuel supplied from the fuel pipe 22 is supplied to the fuel control means 28, the first fuel control means 29 and the second fuel control means 30 through the proportional valve 24 at a predetermined distribution ratio. And then supplied to the lean mixer 25, the first mixer 26, and the second mixer 27, respectively.
After a part of the combustion air supplied from the fan 23 is adjusted to a predetermined flow rate by the air adjusting means 38, the combustion air is supplied to the burner case 20 through the air passage 39 and passes through the gaps between the burner blocks 19. And flows out into the combustion chamber 21. Most of the combustion air is branched into three and the lean air adjusting means 31,
After being adjusted to a predetermined distribution ratio by the first air adjusting means 32 and the second air adjusting means 33, they are supplied to the lean mixer 225, the first mixer 26, and the second mixer 27, respectively.

Most of the fuel is lean fuel adjusting means 2.
At 8, a large amount of combustion air is supplied to the lean mixer 25 by the lean air adjusting means 31 to become a uniform lean mixture, and the lean burners provided in each burner block 19 through the lean passage 34 and the branch passage 37. It is supplied to ten lean chambers 11.
As shown in FIG. 2, the lean air-fuel mixture supplied to the lean chamber 11 is ejected from the lean flame port 12 into the combustion chamber 21 to form a lean flame E having a low flame temperature and an extremely low NOx concentration.

Next, a small amount of fuel is supplied to the first fuel adjusting means 29.
Then, a very small amount of combustion air is adjusted in flow rate by the first air adjusting means 32 and supplied to the first mixer 26 to become a uniform rich mixture, which passes through the first passage 35 and the branch passage 37 'to each burner. The mixture is supplied to the first mixture chamber 13 provided in the block 19. The rich mixture supplied to the first mixture chamber 13 flows out of the first flame port 14 into the combustion chamber 21 at a low speed and undergoes thermal decomposition to generate a large amount of active chemical species. At the base of the flame, a "high-temperature / high-reaction zone" in which the combustion reaction is extremely active is formed, and a rich flame F is formed, which stabilizes a large amount of lean flame at both bases.

Next, an extremely small amount of fuel is supplied to the second fuel adjusting means 30 and a small amount of combustion air is supplied to the second air adjusting means 33.
The mixture is supplied to the second mixer 27 and is supplied to the second mixer 27 to be supplied to the second mixture chamber 16 provided in each burner block 19 through the second passage 36 and the branch passage 37 ". The rich mixture supplied to the second mixture chamber 16 flows out of the second flame port 17 at a low speed into the combustion chamber 21 to form a stable rich flame G and the rich mixture of the first burner 15. To generate rich flame F, and at the same time complete combustion with the combustion air supplied from between the burner blocks 19.

As described above, the multi-concentration combustion having the three types of mixture concentration ignites the rich flame F with the stable rich flame G, which is provided even in the conventional lean-burn combustion.
A large amount of active reactive species, so-called radicals
Is diffused and supplied to the base of the gas to form a "high temperature / high reaction zone" α, which greatly promotes the stabilization of the lean flame.

Here, the first fuel adjusting means 29 and the second fuel adjusting means 30 are set so that the fuel flow rate of the first flame port 16 flows more than that of the second flame port 17, and the fuel concentration of the first flame port 16 is adjusted. When the concentration is excessive, the generation amount of the active chemical species increases, and the formation region of the “high-temperature / high-reaction region” α is expanded, so that the stability of the lean flame E can be further increased.

Thus, as shown in FIG.
The critical jet flow velocity from the diluted 12 flame outlet where the air blows was able to be greatly improved by promoting the stabilization of the base. Then, the flow rates of the respective air-fuel mixtures are controlled, and the flow rates of the lean air-fuel mixture, the first air-fuel mixture, and the second air-fuel mixture are increased and decreased at the same rate. As a result, even when the combustion amount is increased or decreased, the flow pattern of the lean mixed gas ejected from the lean flame port 12 and the rich mixed gas ejected from the first flame port 14 flow in a similar manner, and the lean mixed gas and the highly concentrated mixed gas flow. Is maintained, the substance diffusion from the rich mixed gas toward the lean mixed gas is stably continued.

For this reason, an intermediate product is supplied to the base of the lean flame outlet 12, and a "high temperature / high reaction zone" in which a combustion reaction is active is formed in a minute space of the base even if the amount of combustion increases or decreases.
For this reason, the combustion ratio of the lean air-fuel mixture can be increased, and the concentration of the lean air-fuel mixture can be reduced to achieve ultra-low NOx.

(Embodiment 2) FIG. 4 is an overall sectional view showing a low NOx combustion apparatus according to Embodiment 2 of the present invention. The fuel pipe 22 is branched and one side is directly connected to the first mixer 26, and the other side is provided with a lean mixer 25 and a second mixer 27 branched on the downstream side via a proportional valve 24, respectively. The connection of each mixer is provided by providing a lean fuel adjusting means 28, a first fuel adjusting means 29, and a second fuel adjusting means 30 in the fuel system. A small amount of fuel is adjusted by the first fuel adjusting means 29, and a very small amount of combustion air is adjusted by the first air adjusting means 32 and supplied to the first mixer 26 to form a uniform rich mixture to form the first passage 35. And each of the burner blocks 1 through the branch path 37 '
9 is supplied to the first mixture chamber 13, and the rich mixture supplied to the first mixture chamber 13 flows out of the first flame port 14 into the combustion chamber 21 at low speed and undergoes thermal decomposition. A large amount of active chemical species are generated, and the diffusion supply forms a "high-temperature, high-reaction zone" α at the base of the lean flame where the combustion reaction is extremely active, and stabilizes a large amount of the lean flame at both bases. A rich flame F is formed.

The first fuel adjusting means 29 has a structure in which the flow rate of the lean air-fuel mixture and the flow rate of the second air-fuel mixture are increased and decreased at the same rate by the first fuel adjusting means 29 so that the first air-fuel mixture is ejected. Even when the amount of combustion is small, the amount of heat of the flame at the flame outlet 14 is constant, so that the amount of heat is maintained and a stable flame is maintained. An over-concentrated, oxygen-deficient flame created by jetting a high-concentration mixed gas can have the same shape regardless of the amount of combustion.

Therefore, a large amount of the substance diffusion from the high-concentration gas to the lean mixed gas is maintained even when the combustion amount is small. For this reason, an intermediate product is supplied to the base of the lean flame outlet, and a `` high temperature / high reaction zone '' in which the combustion reaction is active in the minute space of the base can be stably formed even when the combustion amount increases or decreases. As shown in FIG. 5, the combustion ratio of the lean flame can be increased from the conventional point S to the point R, and further lowering of NOx can be realized.

(Embodiment 3) FIG. 6 is an overall sectional view showing a low NOx combustion apparatus according to Embodiment 3 of the present invention. The fuel pipe 22 is branched, and the first mixer 26 and the second mixture 27 are respectively branched and directly connected to one side, and the lean mixer 25 is provided on the downstream side via a proportional valve 24 on the other side. To connect the container,
A lean fuel adjusting means 28, a first fuel adjusting means 29, and a second fuel adjusting means 30 are provided and connected in the fuel system. The first air-fuel mixture and the second air-fuel mixture have a structure in which the flow rate of the lean air-fuel mixture is constantly increased and decreased by the proportional valve 24 by the first fuel adjustment means 29 and the second fuel adjustment means 30 as constant flow rates.

As a result, not only the first flame port 14 for ejecting the highly mixed gas but also the second flame port 17 for ejecting the rich mixed gas
Since these flames are also constant, even when the amount of combustion is small, the amount of combustion is constant even when the amount of combustion is small. Therefore, the calorific value of the flame is maintained at each of the flame openings, and a stable flame can be maintained.

Therefore, the flame holding property of the second flame port 17 is further improved, and a stable flame is formed. Accordingly, it is possible to further increase the combustion ratio of the lean air-fuel mixture and to reduce the concentration of the lean air-fuel mixture. Thus, as shown in FIG. 3, even when the concentration of the lean gas mixture in the lean chamber 11 is reduced from the J concentration to the K concentration, the same stability of the lean flame can be obtained. Therefore, as shown in FIG. 7, the NOx generation concentration moves from the point N corresponding to the concentration J to the point P corresponding to the concentration K to further reduce NO.
x can be realized.

The air adjusted by the air adjusting means 38 and supplied from the air passage 39 flows between the burner blocks 19, and a secondary air passage 41 adjacent to the second flame port 17 is provided. It has a configuration in which the amount of secondary air flowing through the air passage 41 and the fuel flow rate of the lean mixture are increased and decreased at the same rate.
In order to achieve low NOx combustion, most of the fuel gas in the combustion amount is burned in the lean flame port 12, and the minimum small amount of fuel gas required to improve the flame holding property and secure the combustion range From the first and second flame ports 14 and 17.

Therefore, the amount of secondary air and the flow rate of the lean air-fuel mixture are increased or decreased at the same rate to set the minimum equivalent ratio required for combustion, and even when the amount of combustion is changed, excess air is burned. This makes it possible to achieve high efficiency and low noise of the equipment while ensuring good combustion without supplying it to the section. Therefore, in the region where the amount of combustion is small, as shown in FIG.
When the air amount increased due to strong winds and the excess air ratio increased, the lean flame became unstable and unburned products such as HC were generated rapidly.

However, in the present invention, a "high-temperature / high-reaction zone" is formed by stable thermal decomposition of the rich mixture by the rich flame which burns completely, so that generation of HC can be suppressed. Although the rich mixture containing a small amount of air was supplied to the first mixture chamber 13,
The same effect can be realized even if the first air adjusting means 32 is closed and only the fuel is used.

The first mixer 26 and the first mixture chamber 13
Branches off the first passage 35, and the second mixer 27 and the second mixture chamber 16 branch off the second passage 36, respectively.
A plurality of first mixture chambers 13 and second mixture chambers 1 on both sides of
6, the first air-fuel mixture and the second air-fuel mixture are branched and supplied. In multi-concentration combustion, the lean flame outlet 1
The basic configuration is such that the first flame port 14 of the highly mixed gas, the second flame port 17 of the rich mixed gas, and the secondary air are provided outside the first flame port 14 on both sides.

Therefore, the first air-fuel mixture and the second air-fuel mixture are branched and supplied, so that the combustion amount can be varied without time delay, the configuration of the equipment can be simplified, the reliability is improved, and the cost is reduced. Can be achieved.

[0049]

As is apparent from the above description, the low NOx combustion apparatus according to the first aspect of the present invention is characterized in that the lean flame outlet communicates with the lean chamber and supplies the lean air-fuel mixture into and out of the combustion chamber. A first flame port communicating with a first air-fuel mixture chamber adjacent to the chamber, and a first flame port provided adjacent to the lean flame port, and a first flame communicating with a second air-fuel mixture chamber adjacent to the first gas mixture chamber; Having a second flame port provided in close proximity to a mouth, while making the concentration of the first mixture chamber higher than the concentration of the second mixture chamber, the lean mixture, the first mixture, It has a configuration in which the flow rate of the second mixture is increased or decreased at the same rate. A "high-temperature, high-reaction zone" is formed at the base of the lean flame to stabilize the lean flame. Since the flow pattern of the mixed gas is similar, the concentration difference between the lean mixed gas and the highly concentrated mixed gas is maintained, and the substance diffusion from the rich mixed gas toward the lean mixed gas is stably continued. For this reason, an intermediate product is supplied to the base of the lean flame outlet, and a "high temperature / high reaction zone" in which the combustion reaction is active in the minute space of the base is always formed even if the amount of combustion increases or decreases. In addition, it is possible to increase the combustion ratio of the lean air-fuel mixture and reduce the concentration of the lean air-fuel mixture to achieve ultra-low NOx, and to secure a large variable width of the amount of combustion for maintaining good combustion.

The low NOx according to the second aspect of the present invention.
The combustion system has a structure in which the flow rate of the lean mixture and the flow rate of the second mixture are increased and decreased at the same rate with the first air-fuel mixture always being a constant flow rate. Is small, the amount of combustion is constant, so the amount of heat is maintained and a stable flame is maintained. Therefore, the mass diffusion from the high-concentration gas to the lean gas mixture is large even when the combustion amount is small, and the "high temperature / high reaction zone" where the combustion reaction is active is stable even if the combustion amount increases or decreases. Since it can be formed, ultra-low NOx combustion can be realized.

Further, the low NOx combustion apparatus according to claim 3 of the present invention has a configuration in which the flow rate of the lean air-fuel mixture is increased or decreased while the first air-fuel mixture and the second air-fuel mixture are always constant flow rates. As a result, not only the first flame outlet for ejecting the rich mixed gas but also the second flame outlet for ejecting the rich mixed gas are constant, so that these flames vary in combustion amount and burn even when the combustion amount is small. The amount is constant and further enhances the flame holding ability of the second flame port of the rich combustion to form a stable flame. Therefore, the combustion ratio of the lean air-fuel mixture can be increased, and the concentration of the lean air-fuel mixture can be reduced, so that the NOx can be more reliably reduced and the variable range of the combustion amount can be expanded.

In the low NOx combustion apparatus according to a fourth aspect of the present invention, a secondary air passage is provided adjacent to the second flame port, and a flow rate of the secondary air and the lean air-fuel mixture flowing through the secondary air passage is provided. Is increased or decreased at the same rate, the excess air is set even when the combustion amount is changed to the minimum equivalent ratio required for combustion by increasing or decreasing the flow rate of the secondary air and the lean mixture at the same rate. Is supplied to the combustion section, and high efficiency and low noise of the device can be achieved while ensuring good combustion.

In the low NOx combustion apparatus according to the fifth aspect of the present invention, the first air-fuel mixture and the second air-fuel mixture are branched and supplied. The first mixture and the second mixture of the concentrated gas mixture, and the second mixture of the second mixture are divided and supplied. The amount of combustion can be varied without delay, the configuration of the equipment can be simplified, and reliability can be improved and cost can be reduced.

[Brief description of the drawings]

FIG. 1 is an overall sectional view of a low NOx combustion device according to a first embodiment of the present invention.

FIG. 2 is a partially enlarged sectional view of a main part of the apparatus.

FIG. 3 is a characteristic diagram illustrating a relationship between a lean concentration and blow-off in the apparatus.

FIG. 4 is an overall sectional view of a low NOx combustion device according to a second embodiment of the present invention.

FIG. 5 is a characteristic diagram illustrating a relationship between a lean burn ratio and NOx in the same device.

FIG. 6 is an overall sectional view of a low NOx combustion device according to a third embodiment of the present invention.

FIG. 7 is a characteristic diagram illustrating a relationship between a mixture concentration and NOx in the apparatus.

FIG. 8 is a characteristic diagram illustrating a relationship between an excess air ratio and an exhaust concentration in the same device.

FIG. 9 is a partial cross-sectional view of a conventional low NOx combustion device.

FIG. 10 is a partial sectional view of another conventional low NOx combustion device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Lean chamber 12 Lean flame 13 First mixture chamber 14 First flame 16 Second mixture chamber 17 Second flame 28 Lean fuel adjustment means 29 First fuel adjustment means 30 Second fuel adjustment means 31 Lean air adjustment Means 32 First air adjustment means 33 Second air adjustment means

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor, Yuuki Kubota 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F term (reference) 3K065 TA01 TB02 TB04 TB09 TB10 TC02 TC05 TD01 TE01 TH04 TH20

Claims (5)

[Claims] 1. A lean flame port which communicates with a lean chamber and supplies and supplies a lean mixture into and from a combustion chamber, and is provided adjacent to the lean flame port which communicates with a first mixture chamber adjacent to the lean chamber. A first flame port, having a second flame port provided in proximity to the first flame port in communication with a second gas mixture chamber adjacent to the first gas mixture chamber;
A low N that makes the concentration of the first air-fuel mixture chamber higher than that of the second air-fuel mixture chamber and allows the flow rates of the lean air-fuel mixture, the first air-fuel mixture, and the second air-fuel mixture to be increased and decreased at the same rate;
Ox combustion device. 2. A low NOx combustion apparatus wherein the first mixture is always at a constant flow rate so that the flow rates of the lean mixture and the second mixture can be increased and decreased at the same rate. 3. A low NOx gas in which the flow rate of the lean air-fuel mixture can be increased or decreased by maintaining the first air-fuel mixture and the second air-fuel mixture at constant flow rates.
Combustion equipment. 4. A low NOx combustion apparatus comprising a secondary air passage provided adjacent to a second flame port, and wherein the flow rates of the secondary air and the lean mixture flowing through the secondary air passage can be increased and decreased at the same rate. 5. The low-N gas according to claim 1, wherein the first mixture and the second mixture are branched and supplied.
Ox combustion device.