JPH07174314A - Low nox burner and combustion apparatus using the burner - Google Patents

Abstract

PURPOSE:To provide a low NOx burner and a combustion apparatus using the burner in which no lift occurs in a stable flame and generating amounts of CO and HC are small by suppressing a generating amount of NOx. CONSTITUTION:A low NOx burner has a thin burner port group 2 having thin burner ports 1 each for injecting thin premixed gas of a theoretical air volume or more and a thick burner port group 4 having thick burner ports 3 each for injecting thick premixed gas of a theoretical air volume or less in such a manner that the groups 2 and 4 are disposed on a planar burner port plate 6, and comprises a non-burner port zone 5 provided between a plurality of the groups 2, wherein the group 4 is disposed in the vicinity of an outer periphery 7 of the plate 6. A combustion apparatus using this burner is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low NOx burner and a low NOx burner mainly used for a water heater and a bath kettle with hot water supply.
The present invention relates to a combustion device using a burner.

[0002]

2. Description of the Related Art Conventionally, a fully premixed lean combustion method has been known in order to reduce NOx. As shown in FIGS. 9 and 10, the conventional low NO using this premixed lean combustion method is used.
The x-burner ejected and burned a light premixed air with a theoretical air amount or more from the flame nozzle portion 1 provided on the flat flame nozzle plate 6. In the case of this method, the primary air ratio of the light premixed gas is increased and the flame temperature is lowered to reduce the NOx generation amount. On the other hand, the density combustion method is known as a method for improving the stability of the flame. 11 and 12
As shown in Fig. 4, the low NOx burner using this method is theoretically composed of a flat flame nozzle plate 6 and a light flame nozzle group 2 consisting of a light flame nozzle portion 1 from which a light premixed gas of a theoretical air amount or more is ejected. A rich flame port group 4 composed of a rich flame port portion 3 from which a rich premixed air below the air amount is ejected is provided. FIG. 13 shows the distribution of the combustion amount on the CC cross section of FIG. In this case, the rich flame port group 4 is provided not only on the outer peripheral portion 7 of the burner but also between the plurality of lean flame port groups 2 and 2 to stabilize the lean flame 8 formed on the lean flame port group 2. Had improved sex.

[0003]

However, in the lean premixed lean combustion method, when the primary air ratio of the lean premixed gas is increased, the flame 13 becomes extremely unstable, and lift and CO and HC are generated. Was causing an increase. In the rich-lean combustion method, the rich flame 9 formed on the rich flame port group 4 has a high N concentration.
Since Ox is generated, as shown in FIG. 14, when the ratio of the combustion amount of the rich premixed gas becomes large, the generation amount of NOx discharged from the entire flame cannot be sufficiently suppressed. In the low NOx burner using the conventional rich-lean combustion method shown in FIG. 11 to FIG. 13, since the rich flame port group 4 is also provided between the plurality of lean flame port groups 2 and 2, the combustion of the rich premixture is performed. There is a problem in that the amount ratio becomes large and the amount of NOx generated cannot be reduced sufficiently. Thus, in the conventional low NOx burner, NO
It was still insufficient to obtain a burner with a sufficient suppression of x generation and good flame stability. The present invention solves the problems of the conventional low NOx burner described above.
(EN) A low NOx burner that sufficiently suppresses the amount of x generated, has sufficient flame stability, does not generate lift, and produces little CO or HC, and a combustion device using the low NOx burner. That is the purpose.

[0004]

DISCLOSURE OF THE INVENTION According to the present invention, a group of lean flames consisting of a lean flame mouth portion for jetting a lean premixed air mixture of a theoretical air amount or more and a rich flame for jetting a rich premixed air mixture of less than the theoretical air amount. In a low NOx burner in which a rich flame mouth group composed of mouth portions is arranged on a flat flame mouth plate, a flameless mouth band is provided between a plurality of the light flame mouth groups, and the rich flame mouth group is connected to the flame mouth. The present invention relates to a low NOx burner provided only near the outer peripheral portion of a plate and a combustion apparatus using the low NOx burner. In the present invention, the flameless mouth band is usually arranged between the lean flame mouth group and the lean flame mouth group, but in addition to this, it may be provided between the lean flame mouth group and the rich flame mouth group. The number of flameless mouth girdles may be one or more. Further, the rich flame mouth portion in the rich flame mouth group may be formed in a single row or a plurality of rows. It is preferable that the ratio of the combustion amount of the rich premixed gas ejected from the rich flame port group to the total combustion amount be 3 to 30% because the flame is stable and the generation amount of NOx can be sufficiently suppressed. Further, if necessary, secondary air may be flown outside the rich flame port group.

Further, the width dL of the light flame mouth group is 2 to 6 mm, the width dN of the flameless mouth band is 2 to 6 mm, and dN / dL is 1/3 to 3 /.
It is preferably 2. If the width dL of the lean flame group is small, the flame length of the lean flame becomes too long and the flame becomes unstable, and a large amount of CO and HC are generated. If the dL is too large, the recirculation flow is insufficiently formed. , Lift, etc. On the other hand, if the width dN of the flameless mouth band is small, it becomes difficult to hold the flame by the recirculation flow. If dN is too large, the formation of recirculation flow becomes insufficient due to coalescence of light flames, etc., and lift etc. occurs. Furthermore,
If dN / dL is small, the flame becomes unstable and lift occurs, and if dN / dL is too large, it is not possible to obtain a sufficient recirculation flow to hold the lean flame, and the flame is still unsatisfactory. Be stable. Particularly preferably, dL is 3 to 4.5 mm, dN
Is 3 to 4.5 mm and dN / dL is 1/3 to 3/2, and flame stability becomes very good. The width dL of each pale flame group does not have to be the same for each pale flame group. Further, the width dN of each flameless mouth band does not have to be the same for each flameless mouth band.

[0006]

[Function] By providing a flameless mouth band between the groups of pale flames,
A recirculation flow of hot combustion gases is formed on the flameless mouth zone,
It is possible to stabilize the light flame formed on the light flame group. Also, it is difficult to stabilize the lean flame formed near the outer periphery of the flame mouth plate even by this recirculation flow, but since there is a rich flame mouth group near the outer periphery of the flame mouth plate, this rich flame The lean flame is stabilized by the rich flame formed on the mouth group. Further, unlike the conventional rich-lean combustion method, it is not necessary to provide a rich-flame port group between a plurality of lean-flame port groups, so that the ratio of the combustion amount of the rich premixed gas can be reduced, and NOx is generated. The amount can be suppressed sufficiently.

[0007]

Embodiments of the present invention will now be described with reference to the drawings.
In the figure, the same components as those in the conventional technique are designated by the same reference numerals. Embodiment 1 FIG. 1 is a plan view of a main portion of a low NOx burner according to an embodiment of the present invention. This low NOx burner has a flat flame nozzle plate 6,
10 rows of the lean flame mouth group 2 consisting of the lean flame mouth portion 1 that ejects a light premixed air amount of more than the theoretical air amount are arranged with nine flameless mouth bands 5 separated, and a rich premixed amount of less than the theoretical air amount A rich flame port group 4 composed of a rich flame port portion 3 for ejecting air is provided only near the outer periphery 7 of the flame port plate 6. The width dN of the flameless mouth band 5 was set to be substantially equal to the width dL of the light flame mouth group 2. Further, the ratio of the combustion amount of the rich premixed gas ejected from the rich flame nozzle group 4 to the total combustion amount is 1
It was set to 0%. 2 is a cross-sectional view taken along the line AA of FIG. 1, in which the recirculation flow 15 of the high-temperature combustion gas is appropriately formed on the flameless zone 5 to allow the lean flame above the lean flame group 2. 8 is stabilized. Further, secondary air is made to flow outside the rich flame port group 4 that forms the rich flame 9. 3 shows the low N of FIG.
It shows the distribution of the combustion amount of the premixed gas in the Ox burner.

Examples 2 to 3 In Example 2, the width dL of the pale flame outlet group in Example 1 is 4 mm,
The width dN of the flameless mouth band is 4 mm and dN / dL is 1. In Example 3, as shown in FIGS. 15 (a) and 15 (b), three rows of equally-spaced fresh flame mouths arranged in parallel with the flameless mouth band 5 in the fresh flame mouth group 2 are adjacent to each other. The rows are shifted by 60 ° with respect to the pale flame mouth (in the case of Examples 1 and 2, 12
It is further improved in lift performance. The width dL of the light flame mouth group 2 is 4.5 mm, the width dN of the flameless mouth band is 3 mm and dN / dL is 2/3. . The ratio of the amount of combustion by the rich premixed gas to the total amount of combustion was 10% in both Examples 2 and 3. Embodiments 4 to 6 FIGS. 4 to 6 show still another embodiment. 4 is different from FIG. 1 in that a flameless mouth band 5 is provided between the light flame mouth group 2 and the rich flame mouth group 4 (Example 4). FIG. 5 shows an example of arranging the flameless mouth bands 5 in a grid pattern (Example 5), and FIG. 6 shows an example of arranging the flameless mouth bands 5 in an oblique grid pattern (Example 6). The width dN of the flameless mouth band is 0.5 times the width dL of the thin flame mouth group in FIGS.
Was 0.3 times, and the ratio of the combustion amount of the rich premixed gas to the total combustion amount was 10% in all cases.

Example 7 As shown in FIG. 7, a plurality of the low NOx burners 12 shown in FIG. 11 is a blower. FIG. 8 compares the relationship between the primary air ratio of the light premixed gas and the NOx generation amount for the low NOx burner of the present invention of FIG. 1 and the conventional low NOx burner of FIGS. 9 and 11. The broken line indicates the region where the lean flame is unstable. As is apparent from FIG. 8, the low NOx burner of the present invention of FIG. 1 has a wider range of the stable primary air ratio of the lean flame than the burner of the fully premixed lean combustion method of FIG. The amount of NOx generated is smaller than that of the burner using the density combustion method.

[0010]

According to the present invention, the amount of NOx generated is sufficiently suppressed, the stability of flame is good, lift is not generated, and the amount of CO and HC generated can be reduced. This allows a wide turndown ratio. Further, since it is not necessary to dispose the rich flame port group between the plurality of lean flame port groups as in the conventional rich and lean combustion method, the structure of the NOx burner can be simplified.

[Brief description of drawings]

FIG. 1 is a plan view of an essential part of a low NOx burner according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a graph showing a distribution of a combustion amount of the low NOx burner shown in FIG.

FIG. 4 is a plan view of an essential part of a low NOx burner according to another embodiment of the present invention.

FIG. 5 is a plan view of an essential part of a low NOx burner according to another embodiment of the present invention.

FIG. 6 is a plan view of an essential part of a low NOx burner according to another embodiment of the present invention.

FIG. 7 is a diagram showing a combustion apparatus using the low NOx burner of FIG.

FIG. 8 is a graph showing the relationship between the primary air ratio of the lean premixed gas and the NOx generation amount.

FIG. 9 is a plan view of a main part of a conventional low NOx burner.

10 is a sectional view taken along line BB of FIG.

FIG. 11 is a plan view of relevant parts of a conventional low NOx burner.

12 is a cross-sectional view taken along line CC of FIG.

FIG. 13 is a graph showing the distribution of the combustion amount of the burner shown in FIG.

FIG. 14 is a graph showing the relationship between the ratio of the combustion amount of the rich premixed air and the NOx generation amount.

FIG. 15 is a plan view of a main part of a low NOx burner according to another embodiment of the present invention, in which (b) is a partially enlarged view of (a).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light flame mouth part, 2 ... Light flame mouth group, 3 ... Thick flame mouth portion, 4 ... Thick flame mouth group, 5 ... Flameless mouth band, 6 ... Flame mouth plate, 7 ... Outer periphery part, 8 ... Light flame , 9 ... Rich flame, 10 ... Combustor, 11 ... Blower, 12
… Low NOx burner, 13… Flame, 15… Recirculation flow

Claims (3)

[Claims] 1. A lean flame port group consisting of a lean flame port portion for ejecting a lean premixed air amount greater than the theoretical air amount, and a rich flame port group consisting of a rich flame port portion for ejecting a rich premixed air amount less than the theoretical air amount. In a low NOx burner in which a flat flame mouth plate is arranged, a flameless mouth band is provided between the plurality of light flame mouth groups, and the rich flame mouth group is provided only near the outer peripheral portion of the flame mouth plate. Low NOx burner. 2. The low NOx according to claim 1, wherein the width dL of the lean flame group is 2 to 6 mm, the width dN of the flameless mouth zone is 2 to 6 mm, and dN / dL is 1/3 to 3/2. Burner. 3. A combustion device using the low NOx burner according to claim 1.