JP3473140B2 - Low NOx burner - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low NOx burner mainly used for a water heater or a hot-water bath. 2. Description of the Related Art Conventionally, a lean burn method has been known as a low NOx combustion method. FIGS. 4 and 5 show a conventional example of a low NOx burner using this combustion method. This burner is composed of a flare port portion 2 composed of a group of flame outlets for injecting a light premixed gas of a theoretical air amount or more into a flat flame port plate 1 and a flame port group for ejecting a rich premixed gas of a theoretical air amount or less. Is provided with a thick flame outlet portion 3 comprising: Since the light flame 4 formed at the light flame port 2 is a lean flame, the flame temperature is low and the emission amount of NOx is small. However, since the fresh flame 4 itself has a primary air ratio of about 1.3 to 2.0, the stability of the flame is poor, and it is used even at an air ratio higher than the flammable limit. Therefore, in order to stabilize the light flame 4, the rich flame 5 is formed so as to surround the light flame 4. Although the primary air ratio of the rich flame 5 is a very stable flame of about 0.4 to 0.8, it burns in the same manner as the Bunsen flame, so that a large amount of NOx is emitted. Normally, the rich flame 5 is adjusted so as to secure the stability of the flame as a whole while reducing the low NO.
We are trying to convert to x. [0003] In the conventional burner, the fuel gas amount of the rich premixed gas is reduced to about 20 to 40 in order to secure the stability of the lean flame 4 and suppress the entire NOx emission. %. When the rich premix is 30%, the NOx generated from the light flame 4 is 40 ppm (O ₂ 0% conversion), and the rich flame 5
Since NOx generated from the gas is about 120 ppm, the NOx exhausted from the whole becomes 64 ppm from the following equation (1), and it is not possible to significantly reduce NOx. (1) 0.7 × 40 + 0.3 × 120 = 64 (ppm) (1) Further, considering the case where this burner is used in a hot water heater of No. 16, etc., 16 to 2 In order to secure the capability range of No.5, it was impossible to deal with one set of burners, and two or more sets of burners were required to deal with the change of the number of burners. For this reason, low NOx burners have been expensive. The present invention solves the above-mentioned problem of the conventional low NOx burner, and the low Nx burner which sufficiently suppresses NOx emission and has excellent flame stability.
An Ox burner is provided. According to the present invention, a plurality of rows of strip-shaped light flame ports comprising a group of flame ports which eject a light premixed air of a theoretical air amount or more are formed between the light flame ports. A flameless port is provided around the light flame port and the flameless port. A flame port portion is formed, and two sets of the flame port portions are arranged on a flame port plate with a non-flame port band for gas sealing interposed therebetween. The present invention relates to a low NOx burner in which a rich flame port is not provided in a portion extending from a non-flame port between light flame ports in a peripheral portion adjacent to the above. Next, an embodiment of the present invention will be described with reference to FIGS. First, a plurality of rows of strip-shaped light flame ports 2 composed of a group of flame ports that blow out a light premixed air of a theoretical air amount or more are arranged with a non-flame port 6 in which fuel or air is not blown out. Along with
A set of flame outlets 10 composed of flame outlets 3 composed of a group of flame outlets for ejecting a rich premixed air having a theoretical air volume or less is disposed around the light flame outlet 2 and the non-flame vent 6. Is composed. In FIG. 1, two sets of flame ports 10a and 10a are sandwiched between a single flat flame port plate 1 and a non-flame port band 8 for gas sealing.
b is arranged. And, in one flame outlet part 10a,
A rich flame opening 3a is provided at a portion of the peripheral portion 9 adjacent to the non-flame opening band 8 for gas sealing, which is extended from the light flame opening 2a. A portion extending from 6a was not provided with a rich flame outlet. The other rich flame port 3 is formed continuously around the flame port 10a as shown. Here, the flame port plate 1 is made of ceramic, and the light flame port portion 2 and the rich flame port portion 3 have a diameter of 1.0 to 1.0.
Many 2.0 mm holes are provided. First, since the non-flame port 6 is disposed between the rows of the light flame ports 2, the high-temperature combustion gas is regenerated on the non-flame port 6 as shown in FIG. A circulating flow 7 is formed, so that the lean flame 4 can be stabilized. Furthermore, since the rich flame port 3 is provided so as to surround the light flame port 2 and the non-flame port 6,
The rich flame 5 can stabilize both sides of the light flame 4 and the outermost light flame 4. Although it is better to provide the rich flame 5 continuously, it is possible to stabilize the light flame 4 even if the boundary between both flame ports is provided intermittently like the rich flame port 3a. With this basic configuration, the flame can be stabilized without enclosing the entire periphery of the lean flame 4 with the rich flame 5, so that the fuel gas amount of the rich premixed gas can be reduced to about 10%. . That is, when the NOx generated from the light flame 4 or the rich flame 5 is the same as that of the prior art, the NOx discharged from the whole is calculated by the following equation (2).
It becomes 8 ppm, and it is possible to reduce 64 ppm in the prior art to 3/4. 0.9 × 40 + 0.1 × 120 = 48 (ppm) (2) In the present invention, two sets of flame ports 10 a and 10 b are provided in one flame port plate 1. Since it is provided, it is possible to switch the capacity (switching between combustion of both 10a and 10b and combustion of only 10b) with one burner, so that an inexpensive structure can be achieved. Here, if a continuous rich flame portion 3 is provided also in the flame portion 10b that burns when the capacity is switched and the flame portion 10a that does not burn, as shown in FIG. The rich flame 5 is formed on both sides of the non-flame mouth zone 8 of FIG. By the way, the air for secondary combustion is supplied to the rich flame 5 formed in this portion mainly from the surplus air of the light flame 4 existing on both sides thereof. Further, since there is a recirculated gas lacking air on the non-flame port zone 8 for gas sealing between the rich flames 5, the combustion in this part is deteriorated, and the flame elongates. In other words, this portion is likely to be in an air shortage state, and the emission of unburned components (hydrocarbon and carbon monoxide) increases. For this reason, according to the present invention, of the rich flame ports 3 present on both sides of the non-flame port zone 8 for gas sealing, which is the seal portion of both flame ports, the rich flame port on the side that does not burn due to the switching of performance. The portion 3a is connected to the portion corresponding to the light flame port 2a (the light flame port 2
a), and is not provided at a portion corresponding to the non-flame opening 6a (a portion extending from the non-flame opening 6a). And the rich flame 5 is subdivided, the diffusion of the secondary combustion air is improved, and the elongation of the flame can be suppressed. By the way, in this portion, since the rich flame 5a is not continuously formed, the flame holding ability is reduced by this portion alone. However, the light flame 4 which holds the flame by the rich flame 5a is formed. This is when a flame is always formed in the two sets of flame ports 10a and 10b. In the non-flame port zone 8, which is a seal between the two flame ports, a high-temperature recirculating flow is present. Since the surface temperature of the flame port plate 1 is also high, the flame holding ability does not decrease due to the partial arrangement of the rich flame port portion 3a. According to the present invention, it is possible to provide an inexpensive low-NOx burner that sufficiently suppresses NOx emissions, has good flame stability, and does not emit unburned substances. It becomes possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a main 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 sectional view taken along line BB of FIG. 1; FIG. 4 is a plan view of a main part of a conventional low NOx burner. FIG. 5 is a sectional view taken along line CC of FIG. 4; [Description of Signs] 1 ... Flame plate, 2 ... Light flame port, 3 ... Rich flame port, 4 ... Light flame, 5 ... Rich flame, 6 ... No flame port, 7 ... Recirculating flow, 8 ... Flameless orifice for gas seal, 9 ... Peripheral part adjacent to flameless orifice, 10a, 10b ... Flame mouth

Claims (1)

(57) [Claims 1] A plurality of rows of strip-shaped light flame outlets composed of a group of flame outlets for ejecting a light premixed air of a theoretical air amount or more are provided between the light flame openings. A flame outlet is provided and arranged, and a rich flame outlet consisting of a group of flame outlets that blows a rich premixed air of a theoretical air amount or less is arranged around a light flame opening and a non-flame opening. An opening is formed, and two sets of the above-mentioned opening are arranged on a flame opening plate with a non-flaming opening for gas sealing interposed therebetween, and one opening is adjacent to a non-flaming opening for gas sealing. A low NOx burner in which a rich flame port is not provided in a portion extending from a non-flame port between light flame ports in a peripheral portion.