JP3150241B2 - Evaporative 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 vaporizer and, more particularly, to a burner in which liquid fuel is vaporized through a porous body and burned.

[0002]

2. Description of the Related Art Conventionally, as a burner using liquid fuel, there is a spray burner which sprays liquid fuel from a nozzle and burns it in a droplet state, or a vaporization burner which vaporizes liquid fuel and burns it. As one of the vaporizing burners, the one shown in FIG. 9 is known (Japanese Utility Model Application Laid-Open No. 59-170719).

In FIG. 1, reference numeral 100 denotes an outer cylinder, 102 denotes an inner cylinder, and 104 denotes a preheating device (ignition burner). The preheating device 104 includes an ignition electrode 106 and an auxiliary nozzle 108. Reference numeral 110 denotes a vaporizing cylinder, and a main nozzle 112 is disposed so as to face the vaporizing cylinder.

In this liquid fuel combustion apparatus, first, the liquid fuel is guided to the auxiliary nozzle 108 by the electromagnetic pump 113 through the pilot valve 111 which is opened, and is sprayed and ignited by the ignition electrode 106. The preheating device 104 firstly operates the vaporizing cylinder 110.
Is heated (preheated) to a predetermined temperature.

When the vaporizing cylinder 110 is heated for a certain period of time, the main valve 114 is first opened (at this time, the pilot valve 111 is closed), and the liquid fuel is sprayed from the main nozzle 112.

[0006] The liquid fuel sprayed from the main nozzle 112 hits the vaporizing cylinder 110 and is vaporized in the vaporizing chamber 115.
Then, it flows through the air supply passage 118 together with the air sent from the air blower cylinder 116, and is jetted out of a large number of jet ports 120 provided in the inner cylinder 102 into the cylinder, where it is burned. Here, the ignition of the air-fuel mixture is performed by the residual fire of the preheating device 104. Reference numeral 122 denotes a control device.

[0007]

However, in the case of this type of vaporizing burner, the vaporizing chamber 115 is specially required, and there is a problem that the equipment becomes large. Further, in general, the vaporization type burner including the burner of this type has a problem that the stability of the flame is not sufficient, the variable width of the combustion amount is not sufficiently wide, and the exhaust gas such as CO and NOx is not sufficiently low. Improvement was desired.

[0008]

The invention of the present application has been made to solve such a problem. The first solution of the present invention is to supply a liquid fuel from a fuel supply means to a porous body having continuous pores having an average diameter of 60 to 300 μm, and to hold the liquid fuel in the pores of the porous body. At the same time, air for combustion was applied to the porous body from the air supply means to pass the air through the pores of the porous body, and at that time, the liquid fuel held in the pores of the porous body was vaporized. It is characterized by ejecting and burning it (claim 1).

Another solution of the present invention is to dispose a mesh between the discharge port of the liquid fuel in the fuel supply means and the porous body in one or more stages and in a direction parallel to the liquid receiving surface of the porous body. And the liquid fuel discharged from the discharge port is dispersed by the mesh body in a direction parallel to the liquid receiving surface of the porous body, and then supplied to the porous body. Claim 3).

Still another solution of the present application is to provide a plurality of discharge ports in the fuel supply means, dispose the discharge ports in a direction parallel to a liquid receiving surface of the porous body, and dispose the porous body from the dispersed positions. The liquid fuel is supplied to the fuel cell (claim 4).

Still another solution of the present invention is to provide a spray nozzle at a discharge port of the liquid fuel in the fuel supply means, and spray and disperse the liquid fuel in the nozzle in a direction parallel to a liquid receiving surface of the porous body. And supplying to the porous body (claim 5).

[0012]

As described above, the first solution is to hold a liquid fuel in a porous body having a specific pore diameter, that is, a pore, and to burn a burner in the pore. Using a porous body through which the combustion air from the air supply means can pass, liquid fuel is supplied to the porous body from the fuel supply means and held there, and then the liquid fuel is supplied by the air from the air supply means. It is designed to be vaporized, ejected, and burned.

According to this solution, the fuel and air can be premixed inside the porous body. As a result, the combustion reaction is performed uniformly, and the stability of the flame is enhanced.

[0014] Also, by increasing the stability of the flame,
The advantage that the combustion amount variable width is widened is obtained. That is, the advantage that the turndown ratio, which is the ratio between the minimum combustion amount and the maximum combustion amount, can be increased can be obtained. By the way, in the case of the conventional evaporative burner, the turndown ratio was at most about 5,
It has been confirmed that this burner can be used up to a turndown ratio of about 7.7.

In the present burner, the porous body functions as a vaporizer and a flame holding body as it is, and therefore does not require a special vaporizing chamber unlike the conventional vaporizing type burner, and thus makes the equipment compact. There are advantages that can be done.

Further, the uniformity of the flame allows CO,
It is possible to suppress the amount of exhaust gas such as NOx to a low level, and in addition, it is possible to form a wide surface of a vaporized fuel ejection surface in a porous body, and it is possible to widen a flame holding surface. Accordingly, there is obtained an advantage that the combustion temperature can be lowered and the amount of NOx emission can be reduced. The effect is particularly remarkable when the porous body is formed in a plate shape (claim 2).

In the present solution, the average diameter of the pores of the porous body is set to 60 to 300 μm. The reason is that if the pore diameter of the pores is smaller than 60 μm, even if the combustion air is applied to the porous body, such air cannot pass through the pores of the porous body. When the pore diameter exceeds 300 μm, the pore diameter is too large, and the liquid fuel held in the pores is not sufficiently vaporized and is ejected in a droplet state. In this solution, the more preferable range of the pore diameter is 90 to 260 μm.

A second solution of the present invention is to dispose a mesh or a plurality of meshes between a porous body and a fuel outlet of a fuel supply means, and to divide the liquid fuel from the outlet into the mesh. According to this solution, the liquid fuel can be uniformly supplied to the porous body, and the liquid fuel can be uniformly supplied to the porous body. The advantage is obtained that the liquid fuel can be uniformly held in each pore of the porous body.

A third solution of the present invention is to provide a fuel supply device having a plurality of discharge ports and disposing them in a direction parallel to a liquid receiving surface of a porous body. The advantage is that it can be supplied uniformly to the body.

Further, a fourth solution of the present invention is to provide a fuel supply means in which a spray nozzle is provided at a discharge port to spray liquid fuel in a dispersed state in a direction parallel to a liquid receiving surface of the porous body and supply the fuel to the porous body. Thus, the liquid fuel can be uniformly supplied to the porous body by the present solution.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings. In FIG. 1, reference numeral 10 denotes a vaporizing burner, and reference numeral 12 denotes a blower as an air supply means. Reference numeral 14 denotes an outer cylinder, and 16 denotes an inner cylinder, between which an annular air supply passage (secondary air passage) 18 is formed. A swirler 20 is disposed at the tip of the air supply passage 18. The swirler 20 blows air in a swirling state.

On the other hand, a supply pipe 22 for liquid fuel protrudes into the inner cylinder 16. A discharge port 24 is formed at the end of the supply pipe 22, and the discharge port 24 is open at an upper portion inside the inner cylinder 16. The other end of the supply pipe 22 is connected to the fuel tank.
A pump 28 is provided.

On the other hand, at the distal end of the inner cylinder 16, a pore having an average diameter of 6
A plate-shaped ceramic porous body 30 having continuous pores of 0 to 300 μm is provided. This porous body 30
While retaining the liquid fuel in the pores, the supplied combustion air is passed through the pores, and at that time, the liquid fuel is vaporized and ejected and burned, so to say, a vaporizer and a flame holding body Is also used.

In the inner cylinder 16, two metal nets 34 are arranged at a predetermined interval between the porous body 30 and the discharge port 24. These reticulated bodies 34 are porous bodies 3
It is arranged in a direction parallel to the liquid receiving surface 32 at 0.
Incidentally, reference numeral 36 denotes an ignition device.

Next, the operation of the burner 10 of this embodiment will be described. In the burner 10 of the present embodiment, the liquid fuel is supplied to the inside of the inner cylinder 16 from the discharge port 24 at the distal end through the supply pipe 22. The supplied liquid fuel passes through the mesh body 34, is dispersed in the direction parallel to the liquid receiving surface 32 of the porous body 30, and is supplied to the porous body 30 in that state.

The liquid fuel supplied to the porous body 30 is once held in the many pores. That is, the liquid fuel is kept in a state of seeping into the inside of the porous body 30.

At the same time, combustion air is sent from the blower 12, and a part of the sent air is guided into the inner cylinder 16 through the opening 38 of the inner cylinder 16 (this is referred to as primary air). The other part is guided to an air supply passage 18 between the outer cylinder 14 and the inner cylinder 16.

The air guided to the inside of the inner cylinder 16 flows downward in the inside of the inner cylinder 16 and the air guided to the air supply passage 18 flows downward in the figure.

The air guided to the air supply passage 18 is swirler 2
0, it is jetted in a swirling state from the tip of the passage 18.
On the other hand, the air guided into the inner cylinder 16 is directly blown to the porous body 30.

The air blown to the porous body 30 is jetted to the outside through the pores of the porous body 30. At this time, the liquid fuel held in the porous body 30 is ejected in a vaporized state, ignited by the ignition device 36, and burned. That is, a flame 40 is formed in front of the porous body 30.

In the burner 10 of this embodiment, the liquid fuel is premixed with the air inside the porous body 30 and is ejected from the porous body 30 in a vaporized state, so that the combustion reaction is performed uniformly and the flame is stabilized. The properties are good.

Also, because of the good flame stability,
There is an advantage that the combustion amount variable width can be widened. Further, since no vaporization chamber is required, the equipment can be made compact.

Further, since the flame becomes uniform, CO,
The emission amount of NOx can be reduced, and in addition, since the flame holding surface is formed over a wide range, there is an advantage that the flame temperature is reduced and NOx is reduced.

FIG. 2 shows another embodiment of the present invention. In this embodiment, a plurality of discharge ports 24 are provided and these are dispersed and arranged in a direction parallel to the liquid receiving surface 32 of the porous body 30. According to the example, an advantage that the liquid fuel can be uniformly supplied to the entire porous body 30 is obtained.

FIG. 3 shows still another embodiment of the present invention. In this embodiment, a spray nozzle 42 is provided at a discharge port.
The liquid fuel is sprayed in a dispersed state in a direction parallel to the liquid receiving surface 32 of the porous body 30 and supplied to the porous body 30. Also in this example, the advantage that the liquid fuel can be uniformly supplied to the porous body 30 is obtained.

[Experimental Example] Next, an experimental example for confirming the effect of the burner of the present invention will be described in detail. FIG. 4 shows an outline of this experimental apparatus. Reference numeral 44 denotes a stainless steel cylinder having a length of 120 mm and an inner diameter of 55 mm.
A mullite ceramic porous body 46 having a thickness of 5 mm, an average pore diameter of 180 μm, and a porosity of 0.36 is installed horizontally.

Two 400-mesh wire nets 48 are interposed between the porous body 46 and the outlet 50 for kerosene as a liquid fuel. A combustion chamber is formed by a stainless steel cylinder 52 in front of the porous body 46.

The stainless steel cylinder 52 has a length of 280 m.
m, an inner diameter of 55 mm, and a tap 54 for temperature measurement and gas sampling is formed on the way.

In the experiment of this example, kerosene was dropped from the discharge port 50, and primary air was spouted inside the cylinder 44 and secondary air was spouted into the upper part of the cylinder 52 constituting the combustion chamber. The vaporized fuel ejected from the porous body 46 was ignited in front of it and burned, and each measurement was performed when the combustion reaction reached steady state combustion.

FIG. 5 shows the flammability limit of the equivalence ratio of 1 or less in a relatively low combustion region in terms of the relationship between the equivalence ratio and the combustion amount (output) Q. The fuel lean limit is about the equivalence ratio of about 0.1. And the stable range of the flame was confirmed to be sufficient.

FIG. 6 shows the effect of the amount of combustion on the gas concentration distribution in the combustion chamber at the equivalence ratio (φ) of 0.9. The horizontal axis represents the distance from the surface of the porous body 46 (the downward distance in the figure). Represents From this measurement result, the CO2 near the combustion chamber outlet was
As far as the concentration is concerned, at least Q = 0.91-7.0 kW
It is considered that almost complete combustion occurred in the range of 7.
Stable combustion at a high turndown ratio of about 7 was confirmed.

From this concentration distribution, in the present burner, kerosene vaporizes and evaporates in the porous body 46 or on the surface, fuel-rich combustion near the surface, and then combustion proceeds to the end downstream. It is thought that there is.

Regarding the generation of NOx, the result was 45 ppm or less near the outlet of the combustion chamber in any case.
In this burner, low NOx combustion is performed and NO
The generation of x tended to increase as the amount of combustion increased. This is presumably because, as shown in the temperature distribution of the combustion gas in FIG. 7, the combustion temperature increased with an increase in the amount of combustion, thereby increasing the generation of NOx.

FIG. 8 shows the primary air amount V given to the gas concentration distribution.
_It shows the effect of the ratio of ₁ to the total air amount V. In this experimental result, V ₁ / V =
An optimum value of 0.1 was found.

Although the embodiment of the present invention has been described in detail above, this is merely an example, and the present invention can use, for example, a porous body made of another material. It is also possible to variously change the configuration of the burner.

[Brief description of the drawings]

FIG. 1 is a diagram of an evaporative burner according to an embodiment of the present invention.

FIG. 2 is a view of a vaporizing burner according to another embodiment of the present invention.

FIG. 3 is a view of a vaporizing burner according to still another embodiment of the present invention.

FIG. 4 is a diagram of an apparatus used in an experiment for confirming the effect of the burner of the present invention.

FIG. 5 is a diagram showing a relationship between an equivalent ratio and a combustion amount obtained in the same experiment.

FIG. 6 is a diagram showing a gas concentration distribution at an equivalent ratio of 0.9 obtained in the same experiment.

FIG. 7 is a diagram showing a temperature distribution at an equivalent ratio of 0.9 obtained in the same experiment.

FIG. 8 is a diagram showing the influence of the ratio of primary air to secondary air on the gas concentration obtained in the same experiment.

FIG. 9 is a view showing an example of a conventional vaporizing burner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Evaporation type burner 12 Blower 22 Supply pipe 24 Discharge port 28 Pump 30 Porous body 32 Liquid receiving surface 34 Reticulated body 40 Flame 42 Spray nozzle

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F23D 3/40

Claims (5)

(57) [Claims] 1. A liquid fuel is supplied from fuel supply means to a porous body having continuous pores having an average diameter of 60 to 300 μm to hold the liquid fuel in the pores of the porous body. Combustion air is applied from the air supply means to pass the air through the pores of the porous body. At this time, the liquid fuel retained in the pores of the porous body is vaporized, and then ejected and burned. An evaporative burner characterized by the following. 2. The evaporative burner according to claim 1, wherein the porous body has a plate shape. 3. A net-like body is arranged in one or more stages between the liquid fuel discharge port in the fuel supply means and the porous body and in a direction parallel to the liquid receiving surface of the porous body. The liquid fuel discharged from the reticulated body is dispersed in the mesh body in a direction parallel to a liquid receiving surface of the porous body, and then supplied to the porous body. Evaporative burner. 4. A plurality of discharge ports in the fuel supply means, and the discharge ports are dispersed and arranged in a direction parallel to a liquid receiving surface of the porous body, and liquid fuel is supplied to the porous body from the dispersed positions. The evaporative burner according to claim 1, 2 or 3, characterized in that: 5. A spray nozzle is provided at an outlet of the liquid fuel in the fuel supply means, and the nozzle sprays and disperses the liquid fuel in a direction parallel to a liquid receiving surface of the porous body. The evaporative burner according to claim 1, 2, or 3, wherein the gas is supplied.