JPH0694221A - Low nitrogen oxide burner - Google Patents

Abstract

PURPOSE:To provide a low nitrogen oxide burner in which a flame can be held near a flame port even if a back fire is generated in a flame of a fuel excess side burner at the time of low load combustion in which a heat generation amount is reduced, and the back fire can be prevented. CONSTITUTION:A low nitrogen oxide burner 100 has a flame lightention tip burner 2 for forming slit-like side flame ports 21, 21 at a side of a main flame port 11 of a flat main burner 1 in such a manner that the burner 2 has a common suction port 22 for sucking mixture gas independently from the main burner to supply air excess mixture gas to the burner 1 and to supply fuel excess mixture gas to the burner 2, and comprises a throttle 3 for preventing a back fire at an upstream at a small gap from the side flame port in the tip burner 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low nitrogen oxide burner used as a heat source for a gas water heater, etc.

[0002]

2. Description of the Related Art A sleeve-fire burner forming a slit-shaped sleeve crater is provided on the side of the main crater of a flat main burner, and the main burner has excess air and the sleeve-fire burner has an excess of fuel. A low-nitrogen oxide burner has been proposed which supplies a mixture (hereinafter referred to as a mixture).

In Japanese Patent Laid-Open No. 3-263505, the excess air ratio of the main burner is set to be larger than 1.4, and the excess air ratio of the sleeve fire burner is set to be smaller than 0.8. There is disclosed a low nitrogen oxide (low NOx) burner capable of reducing the nitrogen oxide (NOx) discharged by about 120 ppm to 40 to 60 ppm when combusted in.

However, when this type of low-nitrogen oxide burner is used as a heating source such as a water heater that needs to greatly change the amount of heat generated according to tapping conditions, the sleeve crater becomes stable at the time of high-load combustion due to excessive fuel. In a sleeve fire burner in which the flow velocity of the air-fuel mixture is set to be small in order to form a flame, the flow velocity of the air-fuel mixture becomes smaller than the flame propagation velocity at low load combustion, and there is a flashback where the flame is sucked into the burner from the sleeve crater It is easy to occur.

[0005]

If a flashback occurs and combustion continues in a state where a flame is sucked into the sleeve fire burner or in the vicinity of the gas ejected from the nozzle, the burner is overheated and the burner is burned into the burner. Problems such as soot adhesion, misfire, and noise will occur. An object of the present invention is that, at the time of low-load combustion with a reduced calorific value, even if the flame of the burner on the excess fuel side begins to backfire, the flame can be held near the sleeve crater and drawn into the sleeve fire burner. Or to provide a low-nitrogen oxide burner that can prevent the mixture from reaching the nozzle provided at the intake port.

[0006]

The low nitrogen oxide burner of the present invention is provided with a sleeve fire burner forming a slit-shaped sleeve crater on the side of the main crater of the flat main burner. Independently of the main burner, it has a suction port for sucking a mixture of fuel gas and primary air, supplies an excess air mixture to the main burner, and an excess fuel mixture to a sleeve fire burner. In the low-nitrogen oxide burner for supplying the above, a throttle part for preventing flashback is formed in the sleeve fire burner on the upstream side with a small gap from the sleeve crater.

[0007]

According to the present invention, since the throttle portion is provided on the upstream side with a small gap from the sleeve crater of the sleeve fire burner,
Even if the flow velocity of the air-fuel mixture from the sleeve crater decreases at the time of low-load combustion and a flashback begins to occur, the flame stops at the throttle portion. Therefore, troubles such as overheating of the burner, adhesion of soot in the burner, misfire, and noise generation can be prevented, and the safety is high.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a combustion part of a water heater in which low-nitrogen oxide burners 100 according to the present invention are fixed by a frame (not shown) and arranged in rows at a predetermined interval. Low nitrogen oxide burner 1
00 comprises a main burner 1 having a flat main crater 11, and a sleeve burner 2 forming slit-shaped sleeve craters 21 on both sides of the main crater 11.

The main burner 1 is made of sheet metal and, as shown in FIGS. 1 and 2, is provided with the elongated main crater 11 consisting of a group of slit flames arranged in parallel at the upper end, and the mixture is provided on the side. Is provided with a suction port 12.

The sleeve fire burner 2 is made of sheet metal and, as shown in FIG. 1, forms the flat slit-shaped sleeve fire mouths 21 and 21 across the main fire mouth 11 as shown in FIG. As shown in (b), one common suction port 22 is provided on the side. A slit-shaped throttle portion 3 is formed near the sleeve craters 21, 21. In this embodiment, as shown in FIG. 4, the narrowed portion 3 is welded to either the outer wall surface 1A of the main burner 1 or the inner wall surface 2A of the sleeve fire burner 2 by a metal plate 32 provided with slit rows 31. Has been formed.

FIG. 3 shows a water heater, which corresponds to the intake port 12 of the main burner 1 of the low-nitrogen oxide burner 100 and the common intake port 22 of the sleeve fire burner 2, and the fuel gas supply pipes 4 and 5 are provided.
Are juxtaposed. Proportional valves 41 and 51 for controlling the flow rate of the fuel gas are provided in each of the supply pipes 4 and 5, and nozzles 42 and 52 are arranged in a row. The fuel gas ejected from the nozzle 42 entrains the primary air and becomes an air-excessive air-fuel mixture having a large flow velocity, and is introduced from the suction port 12 to the main burner 1.
It flows in and burns lean in the main crater 11 as shown in FIG.

The fuel gas injected from the nozzle 52 entrains the primary air into an excess fuel mixture having a small flow velocity and flows into the sleeve fire burner 2 from the common inlet 22 and is dispersed on both sides of the main burner 1 to disperse the sleeve. Excessive fuel combustion occurs at the craters 21, 21. In addition, the flow velocity of the air-fuel mixture temporarily increases in the throttle portion 3 on the upstream side where there is a small gap from the sleeve craters 21 and 21, but in the sleeve craters 21 and 21 on the downstream side only by the small gap. The flow velocity of the air-fuel mixture is decreasing, and the flame formed above the sleeve craters 21, 21 becomes a gentle and stable flame.

Since the sleeve fire burner 2 is provided with the common suction port 22 as in this embodiment, it is not affected by variations in manufacturing and assembly and variations in opening adjustment of the suction port by a damper (not shown). Sleeve crater 21, 21
There is an advantage that the air-fuel ratio of the air-fuel mixture supplied to is constant.

As a combustion condition of the main burner 1, for example, an excess air ratio of 1.4 is set, and an excess air ratio of the sleeve fire burner 2 is set to 0.8. It As a result, the main burner 1 performs lean combustion with excess combustion air, the sleeve fire burner 2 performs excess fuel combustion with insufficient combustion air, and the unburned gas reacts completely with the excess air of the lean combustion flame to complete combustion. . As a result, 120pp generated when the whole is burned at a substantially constant air-fuel ratio
The NOx emission amount of m can be reduced to 40-60 ppm.

The combustion amount is increased or decreased from a maximum of 30,000 kcal to a minimum of 3,000 kcal in accordance with the setting of the hot water supply temperature of the water heater. Due to the reduction of the combustion load, the flow velocity of the air-fuel mixture in the main burner 1 and the sleeve burner 2 decreases as shown in FIG. At this time, the sleeve crater 21 of the sleeve fire burner 2,
In some cases, the flow velocity of the air-fuel mixture ejected from 21 becomes equal to or lower than the flame propagation velocity, and flashback begins to occur.

In this case, according to the present invention, FIG.
As shown in (b), the flame F has a slit-shaped sleeve crater 21.
From the inside to the inside of the sleeve fire burner 2, but the flow velocity of the air-fuel mixture is kept high in the throttle portions 3 and 3, and the flame propagates to the back of the sleeve fire burner 2 because the wall of the throttle portion 3 has a quenching action. Things are thwarted. When the combustion load increases and the flow velocity of the air-fuel mixture increases, the throttles 3 and 3 are located near the sleeve craters 21 and 21, so the flame F can return to the sleeve crater 21. The II cross section of (a) of FIG. 4 is (b) of FIG.

The throttle portion 3 is 0.5 mm below the flashback limit.
The following slit widths are desirable. The narrowed portion 3 may be a row of holes having a diameter of 1.0 mm or less, instead of the row of slits. Further, as shown in FIG. 5, the bulging portions 1B, 2 are provided so as to face the wall surface of the main burner 1 and the wall surface of the sleeve fire burner 2.
By providing B, a slit having a width of 0.5 mm or less can be formed.

[Brief description of drawings]

FIG. 1 is a perspective view of a combustion part of a gas water heater using the low nitrogen oxide burner of the present invention.

FIG. 2 is a side view of a main burner and a sleeve fire burner.

FIG. 3 is a schematic view of a gas water heater equipped with a low nitrogen oxide burner.

FIG. 4 is a plan view and a cross-sectional view of a main part of a low nitrogen oxide burner.

FIG. 5 is a cross-sectional view of essential parts of a low nitrogen oxide burner according to another embodiment.

[Explanation of symbols]

 1 Main Burner 2 Sleeve Fire Burner 3 Throttle 4 Fuel Gas Supply Pipe for Main Burner 5 Fuel Gas Supply Pipe for Sleeve Fire Burner 11 Main Vent 21 Sleeve Crater 22 Common Intake 100 Low Nitrogen Oxide Burner

Front page continuation (72) Inventor Hideaki Ishikawa 2-26 Fukuzumicho, Nakagawa-ku, Nagoya City Rinnai Co., Ltd.

Claims (2)

[Claims] 1. A sleeve fire burner forming a slit-shaped sleeve crater is provided on the side of the main crater of the flat main burner, the sleeve fire burner being independent of the main burner, the fuel gas and the primary air. In a low-nitrogen oxide burner that supplies an excess air-fuel mixture to the main burner and an excess fuel mixture to the sleeve fire burner, the inside of the sleeve fire burner A low nitrogen oxide burner characterized in that a narrowed portion for flashback prevention is formed on the upstream side with a small gap from the sleeve crater. 2. The sleeve burner for forming a slit-shaped sleeve crater sandwiching the main crater on both sides of the main crater of the main burner according to claim 1, and common to supply air-fuel mixture to both sleeve craters. A low-nitrogen oxide burner characterized by having an inlet.