JPH0756369B2 - Low NOx burner - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous combustion burner for gas turbines, jet engines, heaters and the like, and more particularly to a burner in which generation of nitrogen oxide (NOx) is remarkably reduced.

[0002]

2. Description of the Related Art Conventionally, in a continuous combustor such as a gas turbine, a jet engine, a heater, etc., as shown in FIG. And the air are mixed and burned, and at the downstream of the flame 6, the dilution air 4 is supplied from the air holes 3 provided on the combustor wall, and the combustion gas 5 having a required temperature is obtained. In this case, a relatively high temperature portion is inevitably formed in the flame 6, and NOx is rapidly generated there, so that it is difficult to significantly reduce NOx emission.

A method in which fuel and air are premixed and burned at a fuel concentration much lower than the stoichiometric ratio (lean combustion), or at a considerably high fuel concentration in an oxygen-deficient state, the temperature is lowered. The method of introducing air and further burning it (rich / lean combustion) has the potential to significantly reduce the generation of NOx.

[0004]

However, in the case of lean burn, the leaner the production of NOx, the more dilute the NOx production becomes, but under too lean conditions, the production of carbon monoxide and unburned hydrocarbons increases, and the flame becomes unstable. The problem arises that Therefore,
In order to burn under lean conditions where unburned components such as carbon monoxide and unburned hydrocarbons do not occur, and to suppress the generation of NOx, introduce air immediately downstream of the flame and mix it rapidly. Therefore, it is necessary to stop or slow down the NOx generation reaction. Further, in the rich / lean combustion, in order to completely burn the partially burned gas while suppressing the generation of NOx, this gas and the introduced air must be rapidly mixed within a short time.

However, in a combustor having a structure in which dilution air is introduced through holes formed in the wall surface of the combustor like the conventional combustor shown in FIG. 5, it is extremely difficult to spatially uniform and rapid mixing. Is. Lean combustion not only impairs flame stability, but also increases the generation of unburned components such as carbon monoxide and unburned hydrocarbons.

[0006]

In the burner of the present invention, a large number of flow paths for the premixed fuel and air and a large number of flow paths for the air in the combustion chamber are mutually different. A large number are arranged so as to surround each other, and the structure is such that air flows out from the latter downstream of the former end.

[0007]

[Operation] The premixture of fuel and air flowing into the combustion chamber is
Although flame is formed and held at the end of the flow path, the premixed gas is divided into many flow paths and flows in, so the flame at each flow path end is short, but the entire flow path The flames at the edges are united to form a thin planar combustion zone in the combustion chamber. Air flowing out of the air flow path flows into the downstream of this flame, and the NOx production reaction is stopped without interfering with the combustion zone,
Reduces NOx emissions.

[0008]

In the embodiment shown in FIG. 1, a pipe 8 through which a premixed fuel and air flows and a pipe 9 through which air flows are alternately arranged at the end of a combustion chamber 7, and the air pipe 9 is a mixture pipe. 8 extends downstream, the front end surface is closed, and a hole is provided in the tube wall. As shown in FIG. 2, the flame is held at the outlet end face of the gas mixture tube 8, and the air flowing out from the air tube 9 through the hole 10 in the tube wall in the radial direction downstream thereof is mixed with the combustion gas due to the flame and the temperature thereof is changed. Lowering to stop or slow down the NOx production reaction.

If the tubes 8 and 9 are thin, the air tube 9
The same effect can be obtained even if the hole is not provided in the wall and the end face opening of the pipe is directly discharged to the downstream side.

In the embodiment shown in FIG. 3, air-fuel mixture 11
Flows out into the combustion chamber 7 through a hole 13 provided in the plate 12 at the end of the combustion chamber 7, and the flame is held there. An air pipe 9 is arranged in the center of the hole 13, and air is supplied and mixed into the combustion gas downstream of the flame through a hole in the wall of the air pipe 9.

In the above embodiment, if the air pipe and the air-fuel mixture are not fixedly provided and the axial distance between the two can be made variable according to the combustion condition, the combustion condition over a wider range can be obtained. Both unburned components and NOx can be suppressed and a greater effect can be obtained.

As another embodiment, as shown in FIG. 4, the combustion chamber wall is a double pipe, and the air-fuel mixture 11 is supplied to one of the pipes and the air is supplied to the other pipe, and at the same time, from the combustion chamber wall surface to the combustion chamber. Holes 14, 1 through which air-fuel mixture and air flow out in the radial direction
If 5 is provided so as to surround each other, the combustor can be downsized and cooling of the wall surface of the combustion chamber is unnecessary.

[00013]

As described above, in the burner of the present invention, the flame that is subdivided and held by the premixed air forms a thin combustion zone having a planar shape as a whole, and immediately after that, the air is effective. The temperature of the combustion gas immediately after combustion is lowered, the NOx generation reaction can be immediately stopped or decelerated, and NOx generation can be suppressed.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a configuration of a first embodiment of a burner of the present invention.

FIG. 2 is a partial cross-sectional view showing the relationship between the mixed air tube and the air tube of the above embodiment.

FIG. 3 is a conceptual diagram showing the configuration of another embodiment of the present invention.

FIG. 4 is a sectional view of yet another embodiment of the present invention.

FIG. 5 is a conceptual diagram showing the configuration of a conventional burner.

[Explanation of symbols]

 1 Fuel 2 Air 3 Air Hole 4 Dilution Air 5 Combustion Gas 6 Flame 7 Combustion Chamber 8 Mixture Tube 9 Air Tube 10 Hole 11 Mixture 12 Plate 13 Hole 14, 15 Outflow Hole

Claims (5)

[Claims] 1. A plurality of flow passages in which a premixed mixture of fuel and air flows and a plurality of flow passages in which air flows are arranged in a combustion chamber so as to mutually surround other flow passages. A low NOx burner characterized in that a flat flame is formed at the end of the flow path of the air flow, and the air from the air flow path is introduced downstream of the flame. 2. The inflow of air from the air flow path to the downstream side of the flame is the air flowing out in the radial direction from the air flow path extending downstream from the flow path end portion of the air-fuel mixture. Low NOx according to claim 1, characterized in that
Burner 3. An end portion of the flow path of the air-fuel mixture is formed by a plate which is arranged at an end portion of the combustion chamber and has a large number of holes in the center of which the air flow path is arranged. 1 low NOx burner 4. The low NOx burner according to claim 1, wherein the axial distance between the flow passage end of the air-fuel mixture and the air flow passage end is variable. 5. The combustion chamber wall is a double pipe for supplying a mixture and air to the combustion chamber, respectively, and the mixture and air flow out radially from the double pipe into the combustion chamber. The holes are provided so as to surround each other.
Low NOx burner