JPS587125B2 - Burner plate for closed combustion method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a burner plate used in a closed combustion type burner.

A burner plate made of a ceramic or other refractory plate with a large number of flame holes is well known as an open combustion type burner, or a Schwank type burner, but it can be used as a closed combustion type burner plate. When used, there are the following problems.

In other words, in the burner plate of a Schwank type burner, combustion is balanced in the part that is a few millimeters from the plate surface into the flame hole, and this combustion causes the entire plate to become red hot, releasing a large amount of radiant heat, and the released radiant heat is utilized. It is something.

On the other hand, a closed combustion type burner is one that forcibly supplies combustion and air to combust it in a combustion chamber, that is, it performs high-load combustion, and uses the heat of the combustion flame itself. It is.

Therefore, if a burner plate similar to that used in a bank type burner is used in such a closed combustion type burner, the plate becomes red hot even though it is not necessary to generate red heat, causing heat loss, and high-load combustion. is difficult,
In order to solve this problem, a considerably large area is required, and the entire burner becomes extremely large.

By the way, if we take as an example the radiant burner plate that is commonly used in the past, it is 67mm x 46mm x 11mm.
Approximately 1000 flames L with a diameter of 1 mm (thickness T) are provided (approximately 950 for city gas, approximately 1300 for LP gas), and an appropriate number of these are used in combination. However, this standard input Kca per plate is
The limit for l was approximately 360 Kcal/Hr.

Therefore, if this were to be applied to a high-calorie burner, for example, at 6000 Kcal/Hr, an area equivalent to about 16 of the above-mentioned plates would be required, which would pose a problem in making the device more compact.

Also, even if you ignore this and achieve high-load combustion,
Since the total area of the flame holes drilled in the plate is quite large, flashbacks can easily occur if the pressure in the combustion chamber increases, eg in the case of a head wind.

In addition, if there is a change on the input side, that is, if the amount of combustion increases or the amount of air decreases, the surface temperature of the plate will rise and the effect will spread to the back side, so the temperature difference with the back side will decrease and eventually a flash will occur. Wake up Buck.

In particular, unlike burners for gas combustion, burners for vaporization type combustors use liquid fuel of almost the same quality, so they have the advantage of having almost the same flame combustion speed. Fluctuations in the input) and mixed gas pressure (fluctuations in the amount of air blown by the combustion blower) are large, and the combustion air ratio fluctuates, resulting in lifting (flying sparks) and yellow chips (red flames, soot). combustion).

That is, there is a permissible limit range for the above-mentioned fluctuation, and the wider the range, the more stable the burner can be realized, but this has been difficult to achieve with the flame arrangement in the conventional burner plate.

As described above, if a conventional burner plate is applied as it is to a closed combustion type burner, there are disadvantages such as difficulty in high-load combustion, heat loss during combustion, and easy occurrence of flashback.

The object of the present invention is to provide a burner plate that can solve this problem.

The present invention will be explained below with reference to the drawings.

FIG. 1 shows an example of the use of a burner plate according to the present invention, where reference numeral 1 denotes a burner plate, and the plate 1 is provided with a large number of flame holes, which will be described later.

Reference numeral 2 denotes a distributor, into which liquid fuel is sequentially supplied via an oil feed pipe 3, and is sprayed around it by the rotating centrifugal force of the distributor 2, and the amount of the sprayed fuel is transferred to a carburetor. It vaporizes with the heat of step 4 and becomes vaporized gas.

At the same time, combustion air is forcibly blown into the carburetor 4 by the rotation of the fan 5.

The vaporized gas mixes with the pregnant air and ejects from each flame L of the burner plate 1, and is ignited by the ignition device 6 and combusts.

This combustion continues in the closed combustion chamber 7, and the exhaust gas is sequentially discharged through the duct.

Note that 8 is a motor that drives the distributor 3 and fan 5, and 9 is a heater that heats the vaporizer 4.

The burner plate is made of a refractory with low thermal conductivity, such as ceramic, and is formed into a disk shape as shown in FIG. As shown in the figure, a large flame hole 10a with a dog-shaped diameter, and a small flame hole 10 with a small diameter.
A large number of b... are equally bored.

In addition, in the example, a burner plate with a diameter of 100 mm has 3.37 dog flame holes and 1030 small flame holes as a burner suitable for generating a calorific value of 6000 Kcal/Hr for a vaporization type combustor using liquid fuel. It has been drilled.

Furthermore, although there are two types of flaming in this example, there may be two or more types.

Therefore, the L diameter of the large flame hole 10a and the small flame hole 10b, their arrangement relationship, etc. are set as shown in Table 1 below.

In addition, the porosity here is the burner plate with many holes only for the large flame ratio,
When compared with a burner plate in which only a large number of small flames were drilled, the results shown in Table 2 were obtained.

As can be seen from this [Table 2], large flames and small flame holes each have their own advantages and disadvantages, but in the burner plate of the present invention, which has large flames and small flame holes at the same time, the following characteristics are achieved: There are advantages such as:

In other words, by creating a large flame, the primary air supply of the combustion gas is sufficient to enable high-load combustion, and it also has the meaning of compensating for an increase in fuel input and a decrease in the amount of air supply, and also forms a clear Bunsen flame. This creates a blue flame, suppressing radiation and preventing the plate temperature from rising.

Therefore, there is no need to worry about clutter or backfire caused by the reduced temperature difference between the front and back surfaces.

On the other hand, by drilling small flame holes, it is possible to prevent excessive fuel combustion and improve ignition performance, which is very important in combustion equipment.
Even if the fuel input is reduced or the air supply is increased, that is, even if there is a slight excess of air, this small flame will be maintained (even if it has already begun to lift). This has the effect of retaining the flame to some extent on the plate surface.

This is effective for flame stability in vaporizing combustors,
For example, when a safety device such as a flame sensor that detects flame current is used together, the role of the small flame L is particularly important.

(In the case of a lift, the flame current is small, but the small flame hole stabilizes the flame current.

) Next, the basis for the setting values in [Table 1] will be described.

(a) The maximum diameter D of canine inflammation L is 3.5 mm.

In other words, if the temperature is higher than this, backfire is likely to occur and noise is likely to occur due to (d) and (e) in [Table 2].

(b) When D/d, that is, the flame hole diameter ratio, is doubled or more, the difference becomes significant and the drawbacks of large flame and small flame L become noticeable.

That is, the large flame tends to lift, and the small flame holes cause excess fuel, making the flame short and prone to red heat.

(c) The manufacturing limit for the plate thickness is approximately 20 mm.

That is, when manufacturing ceramics by firing, if the wall thickness is other than the above, the temperature will not rise to the inside, and a homogeneous plate will not be produced.

(d) If the gap g is 0.5 mg or more, it is difficult to manufacture.

In other words, the pins for creating the flame are close together, and there is a risk of damage when removing the mold.

Moreover, if it is 3 mm or more, the area of the entire plate is required to be large for the same amount of combustion, which is disadvantageous, and furthermore, since the air supply is small, the area around the flame becomes red hot.

(e) The porosity is a factor that maintains the pressure difference between the front and rear of the plate at an appropriate level.
Below, the area of the entire plate becomes larger, and 0.8
Above that, the pressure difference will be small and the fuel will be vulnerable to back pressure such as during ignition.

(f) The L area ratio is something that is difficult to determine in terms of design, whether to distribute large flame holes and small flame holes, respectively, but it should ultimately be determined by experiment.

However, when vaporized gas is viewed as a fluid flow with a certain viscosity coefficient μ, the flow rate Q passing through a flame with a diameter h is as follows: P1-P2: Pressure difference before and after the plate t: Thickness of the plate There is a further relationship.

Therefore, the flow rate ratio of large flames to small flames is not simply an area ratio, but is D4XnD/d4Xnd where nD represents the number of large flames and nd represents the number of small flame holes.

, which corresponds to the distribution ratio of the input gas amount, and the above (
C) Similarly to when determining D/d, it is recommended to consider and decide whether the combustion characteristics of PANA should be on the side of excess air or on the side of excess fuel.

In this embodiment, it was set to about 0.9, but a range of 0.5 to 1.5 would be a range where the characteristics of the small dog flame hole can be utilized.

As explained above, this invention is characterized in that a large number of flame holes of two or more different diameters with hole diameters within the range of 1.0 to 3.5 mm are uniformly bored on the plate surface. As a result, the flame hole load (input combustion amount for a single flame hole area) is 1.5 to 3.5 Kcal/mi2, whereas it is 0.3 to 0.4 Kcal/mi2 in the case of the Schwanck burner plate in the conventional open combustion method. It is possible to reduce the heat of OKcal/mm2, improve combustion (reduced CO%), keep the plate temperature at an appropriate level, improve ignitability, and prevent backfire.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a sectional view showing how the burner plate is used, FIG. 2 is a plan view of the burner plate, and FIG. 3 is a plan view showing the arrangement of flame trimmers. . 1...Burner plate, 10a...Canine flame formation, 10b...Small flame hole.

Claims (1)

[Claims] 1. A burner plate for a closed combustion system, in which a large number of flame holes of two or more different diameters with hole diameters within the range of 1.0 to 3.5 mm are alternately and evenly bored on the plate surface;