JPH0421085B2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The present invention is suitable for industrial/commercial use or home use.
It concerns the NO _X burner.

Conventional technology Conventionally, as shown in FIG _. 7, a burner utilizing complete premix combustion has been used as a low NO The fuel 5 supplied to the combustion chamber 3 was ignited on the surface of the wire mesh to form a flame 6.

Such burners burn fuel with excess air and radiate the heat received from the flame through a wire mesh, thereby lowering the flame temperature and reducing _NOx emissions.

Problems to be Solved by the Invention However, when the amount of combustion is large or when the excess air ratio approaches 1, the temperature of the wire mesh rises rapidly and flashback often occurs, or due to the high temperature, the wire mesh It oxidized and caused durability problems. On the other hand, if you increase the amount of premixed air to increase the excess air ratio, or if you increase the amount of fuel and increase the fuel flow velocity, the flame will become unstable and may emit unburned gas or blow out. This often occurred. As a result, the variable range of combustion amount and air amount is small, which causes practical inconvenience.

Heat is also radiated from the wire mesh to the upstream side, that is, to the combustion chamber, heating the fuel. As a result, the reduction in flame temperature was small and the reduction in _NOx was small.

Means for Solving the Problem A combustion chamber is formed by a combustion chamber wall and a combustion chamber outlet, and a large number of flame ports are provided on the combustion chamber wall, and the flame ports are opposed to each other and are provided on the combustion chamber wall. It is located at the outlet of the fuel supply path, and the outer wall of the combustion chamber serves as a cooling surface.
The fuel supply path is provided outside the combustion chamber, and this is also used as a cooling surface. It is preferable to burn the fuel in a region where the excess air ratio (M) is large (M≧1). A fin is provided around each flame opening.

Effects In such a burner, there is an excess of air, and the flame burns in the opposite direction even when it is away from the flame opening, so combustion is possible in an area with a large amount of air, and it is difficult to blow away even when there is a large amount of combustion. Furthermore, when the amount of combustion is small, the fuel supply path is cooled, there is no backfire, and the variable range of the amount of combustion is wide. The flame is dispersed and heat is radiated from the combustion chamber and fuel supply path, _reducing NO
Efforts are being made to reduce emissions. In particular, when the combustion amount is small or the excess air ratio is small, the flame approaches the flame nozzle and heats the flame nozzle, which reduces _NOx through heat radiation from the flame nozzle, fuel supply path, and combustion chamber wall. is promoting. Fins are placed around the flame opening, which transmits heat from the flame to the fins, _{reducing NO}
We aim to reduce the At this time, the smaller the excess air ratio, the smaller the distance between the flame and the fins, and the greater the heat radiation from the flame. As a result, the smaller the excess air ratio, the greater the NO _x reduction effect.

The outside of the combustion chamber, which is the heat dissipation surface, is a cooling passage that suppresses the rise in flame temperature and reduces _NOx emissions.

Embodiment FIG. 1 is a configuration diagram of an embodiment of the present invention, and 7
is the burner body, 8 is the combustion chamber, 9 is the combustion chamber wall, 10
is the combustion chamber outlet, 11 is the flame port, 12 is the fuel supply path,
13 is a branch pipe, 14 is a cooling passage, and 15 is a vaporization cylinder.

FIG. 2 is a cross section taken along the line AA in FIG. 1, and FIG. 3 is a cross section taken along the line BB. 16 is a blower, 17 is a fuel nozzle, 18 is fuel, 19 is an air-fuel mixture, and 20 is a flame, which forms opposing flames 21. 22 is exhaust gas,
23 is cooling air. 24 is a heater. Hot exhaust gas is often used as a heat source.

Fuel 18 (for example, kerosene) is injected into the carburetor 15 from the fuel nozzle 17. The vaporization cylinder is made of die-cast aluminum, has a heater 24 embedded therein, and is heated to 200-300°C. The fuel supplied to the vaporization tube 15 is vaporized. On the other hand, combustion air is introduced into the vaporization cylinder 15 from the blast air 16 and mixed with vaporized fuel to form an air-fuel mixture 19. The air-fuel mixture 19 passes through the branch pipe 13, passes through a number of fuel supply passages 12 provided in the branch pipe 13, and is introduced into the combustion chamber 8 from the flame port 11 at the tip. The fuel supply passage 12 is constituted by a tube having an elongated passage outside the combustion chamber wall 9.

When this mixture is ignited, flame 20, opposing flame 2
form 1. When using expected fuel instead of liquid fuel, it is possible to burn it in the same way as liquid fuel by omitting the vaporizer cylinder 15.

The flame ports 11 are arranged in pairs facing each other with the combustion chamber 8 interposed therebetween, and a large number of these pairs are arranged. The flames formed at each flame port 11 become opposing flames. The fuel supply passages are also arranged in pairs corresponding to the flame ports 11. A fuel supply passage 13 is arranged outside the combustion chamber wall 9. Fuel supply passages 12 are arranged in groups between the combustion chamber wall 9 and the branch pipes, and cooling passages 14
is formed. Cooling air passes through the cooling passage 14. The branch pipe 13 is divided into several parts, and cooling air can pass between each branch pipe 13, and the heat radiated from the combustion chamber wall 9 can be radiated to the outside. Cooling air is often heated and used as a heat source. A number of opposing flames are formed within the combustion chamber 8, and the heat generated by these flames heats the combustion chamber wall 9 and the fuel supply passage 12. Then, heat is radiated from the combustion chamber wall 9 and the fuel supply path 12,
The flame temperature is lowered, and _NOx contained in the exhaust gas 22 is reduced. The combustion chamber wall 9 and the fuel supply passage 12 are made of a heat-resistant material such as stainless steel, which facilitates heat dissipation by radiation at high temperatures. The outside of the combustion chamber wall 9 heated by the flame serves as a cooling passage, through which cooling air passes.
The combustion chamber wall 9 is cooled to directly cool the flame, and the combustion chamber wall 9 is also prevented from preheating the air-fuel mixture. At this time, the fuel supply passage 12 is similarly cooled by the cooling air. The heat supplied from the flame to the flame outlet is transmitted upstream to the fuel supply path 12 by conduction, preheating the air-fuel mixture, but since the outside of the fuel supply path 12 is cooled with cooling air, preheating is kept to a minimum. be able to.

The present invention is characterized by the formation of opposing flames, which will now be described in detail. Figure 4 shows the configuration of opposing flames. 25 is the unburned gas, 26 is the end of the opposing flame, the flow velocity V is at the air-fuel mixture outlet, and S is the combustion speed. A is a diagram showing the flame attached to the flame nozzle, and B is a diagram showing an opposing flame where the flame is separated from the flame nozzle.

At this time, if the opposing flame ports are not on the same axis, and therefore opposing flames cannot be formed, or if one of the opposing flame ports is removed, the flame will blow off and stable combustion will not be possible. Opposing flames can achieve stable combustion in a region with a high V/S. When opposing flames are formed as shown in Figure B, unburnt gas is released from the end 26 of the opposing flames. At this time, the distance H between the end portion 26 and the flame port 11 increases as V/S increases, and the amount of unburned gas also increases. As shown in FIGS. 1 and 2, since there are many flame ports 11 and the combustion chamber 8 is cut off from the cooling air, unburned gas is oxidized by the adjacent flames. Furthermore, since the combustion chamber wall 9 exists on the upstream side of the opposing flame, the air-fuel mixture flowing into the opposing flame exits from the flame port 11 and is cooled by the combustion chamber wall 9, resulting in a large _NOx reduction effect.

In FIG. 5, fins 28 are provided around the burner port 11, and since the distance from the burner port 11 can be kept constant, the fins can be kept at a uniform temperature.

Further, if fins 28 are provided around the flame port 11, heat from the flame is transmitted to the fins 28, promoting a decrease in flame temperature. FIG. 6 shows the _NOx reduction effect when the fins 28 are provided. Vertical axis is fin 28
The value of _NOx when the excess air ratio M=1 is shown as 1. The horizontal axis shows the excess air ratio M. When the fins 28 are provided, the effect of reducing _NOx can be seen.
At this time, if the excess air ratio is large, the flame gradually moves away from the flame port 11, as shown in FIG. 4B, and the _NOx reduction effect tends to become smaller. The burner of the present invention employs opposed flames, expanding _{the NO} Efforts are being made to reduce this. At this time, even if fins are provided, the fins are located downstream of the flame, and the heat dissipation effect of the fins cannot be expected. Furthermore, in conventional burners, if the excess air ratio is increased, the flame becomes unstable and blows out. Combustion is possible only in areas where the excess air ratio is small, and NO _x reduction effects cannot be expected at high air excess ratios where the NO _x level is low.

Furthermore, as shown in Figure 3, the high-temperature exhaust gas generated by the flame formed at the flame port far from the combustion chamber outlet is supplied to the flame formed at the outlet closer to the combustion chamber outlet 27, preheating the air-fuel mixture. do. At this time, this preheating effect appears prominently in the flame 29 of FIG. 4B. As a result, the stability of the flame near the combustion chamber is ensured. The exhaust gas inflows only near the end 26 of the opposing flame, and does not heat the entire flame, so the amount of _NOx emissions does not increase.

When V/S becomes smaller than the state shown in FIG. 4A, the flame tries to enter the flame port 11. At this time, the combustion chamber wall 9 and the fuel supply passage 12 are cooled with cooling air. Therefore, the flame enters the upstream side of the fuel supply path 12, that is, there is no backfire, and the flame stably burns near the flame port 11.

The fuel supply passage 12 has an elongated tubular shape, and if L is the length and D is the diameter, the air-fuel mixture will flow as Poiseuille if L/D is large. When the flow becomes Poiseuille flow, the end face of the opposing flame approaches the flame port 11, so
Emission of unburned gas 25 is suppressed and complete combustion is facilitated. At this time, the effect is great when L/D≧4.

Effect of the invention The present invention forms a large number of opposing flames in the combustion chamber,
Furthermore, the outside of the combustion chamber is cooled, the fuel supply path is provided outside the combustion chamber, and fins are installed around the flame port, which has a large _NOx reduction effect, especially at low excess air ratios. is large, and combustion can be performed in a wide range of combustion amount and excess air ratio.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a burner according to an embodiment of the present invention;
Figures 2 and 3 are cross-sectional views of the burner, Figures 4 and 5 are conceptual diagrams of the main parts of the burner, Figure 6 is a characteristic diagram of the burner, and Figure 7 is a configuration diagram of a conventional burner. It is. 7... Burner body, 8... Combustion chamber, 11... Flame port, 12... Fuel supply path, 14... Cooling passage, 2
8...Fin.

Claims (1)

[Claims] 1 A combustion chamber is formed by a combustion chamber wall and a combustion chamber outlet, the combustion chamber wall is provided with a plurality of flame ports facing each other, and the flame ports are provided with a plurality of fuel supply channels provided on the outer wall of the combustion chamber wall. The burner communicates with the combustion chamber, uses the outer wall of the combustion chamber as a cooling surface, and has heat dissipation fins between adjacent flame ports.