JPS586A - Combustion device - Google Patents

Abstract

PURPOSE:To contrive the enlargement in high-load combustion and TDR (Turn Down Ratio) range in a combustion device for a heating system in which forced air supply is made through a fan, by a mechanism where in the combustion chamber walls are composed of fins and water tubes, with secondary air outlets being provided in stages in a part of the combustion chamber walls. CONSTITUTION:The amount of secondary air to be supplied via the No.1 and No.2 passages is properly adjusted through the adjustable dampers 6 and 7 respectively to be fed into the secondary air chambers 8 and 9. The secondary air then flows out of the secondary air outlets 10 and 11 to be directed uniformly at the flame forming in the combustion chamber 15. The secondary air jet stream sends the flame spreading all over the combustion chamber 15 so that the flame undergoes heat exchange at the heat exchanger 17 which is of one-piece construction with fin pipes to be let out of the exhaust port 18. In this way, the supply of secondary air enables large-capacity, high-load combustion, helping extend TDR control range. Besides, the combustion chamber walls designed to serve as heat exchanger help prevent rise in temperature of the secondary air chamber and keep secondary air from being heated excessively. This enables miniaturization of the burning system employing a small-size fan.

Description

[Detailed Description of the Invention] The present invention relates to a combustion device for supplying forced air using a fan or the like in hot water supply equipment, heating equipment, etc., and an object of the present invention is to provide a combustion device that satisfies the following items. .

(1) Achieve high-load combustion with a combustion chamber load on the order of 107θ/hm3, and aim to downsize the combustion chamber.

(2) To improve usability when applied to equipment,
To maintain good combustion even if the amount of combustion changes over a wide range.

(3) To maintain good combustion even when using various fuels with different characteristics and to make the roasting device universal.

(4) Make the combustion device simple in structure and downsize the entire combustion system including the fan.

In general household combustion equipment, the premixed gas ejected from the burner nozzle forms a primary flame above the flame nozzle, and a secondary flame is formed in the downstream region of the flame that entrains surrounding air and burns. In general, in hydrocarbon fuels, the secondary flame is an oxidation process of unburned components containing large amounts of CO and H2, and oxygen supply is achieved by so-called entrainment (entrainment of surrounding air) and molecular diffusion, so the reaction rate is slow, and the flame is Extends toward the wake. -Increasing the primary air ratio causes most of the reaction to occur in the primary flame, which shortens the secondary flame. In combustion that exceeds theoretical air by increasing secondary air, so-called full-fire combustion, secondary flames are hardly seen, but on the other hand, oscillating combustion is likely to occur.
Furthermore, since the flame comes into close contact with the flame nozzle, the flame nozzle is heated and often causes a flashback. Furthermore, since the combustion range is relatively narrow, highly accurate control of the amount of premixed air is required. Furthermore, when it comes to hot water supply and space heating, water temperature and air temperature change depending on the season.

In addition, it is required to greatly vary the amount of combustion in response to load fluctuations (when heating multiple taps or heating multiple rooms). That is, it is required to have a large ratio between the maximum combustion amount and the minimum combustion amount, so-called TDR (Turn Down Ratio), which allows maintaining a good combustion state. Therefore, if the TDR is set to a large value, highly accurate flow rate control is required at a minute flow rate, which has the disadvantage of making the device complicated and large.

On the other hand, Bunsen combustion, in which the amount of air in the flame is set below the theoretical amount of air, has a wider combustion range. Therefore, it is possible to increase the TDR without using highly accurate control of the primary and secondary air amounts and the total combustion. However, because the secondary flame expands significantly, high-load combustion cannot be achieved with this method. Therefore, many attempts have been made to achieve high-load combustion by forcibly feeding air using a fan or the like to accelerate the combustion reaction and shorten the flame.

As one conventional example, a burner 101 as shown in FIG.
There is a combustion device in the vicinity of which has a structure in which secondary air supplied by a fan 102 is deflected by a guide plate 103 and introduced into the flame. In this case, increasing the amount of supplied air will cause burner 1
Air is also supplied to the base of the flame outlet at 0o at high speed, making the flame itself unstable. Conversely, if the supply amount is reduced, guide plate 1
At step 03, most of the gas flows parallel to the combustion gas, reducing the amount of gas supplied into the flame and preventing the flame from becoming shorter. Furthermore, since the guide plate 103 becomes hot, its material and durability become problematic, and there is a limit to the high load, as it becomes difficult to extend it near the flame.

There is another conventional example shown in FIG. 8 that has a similar configuration. This is because secondary air that has passed near the burner 104 is deflected by the backflush 105 and supplied to the flame. In this case, the structure becomes more complicated than the case shown in FIG. 7, and the heat capacity of the combustion chamber including the buckle 105 becomes larger. Therefore, the flame is cooled and incomplete combustion tends to occur, resulting in a narrow combustion range. There are restrictions on the machining dimensional conditions of each part and the control of the amount of air supplied, making it impossible to obtain a large TDR.

In another embodiment shown in FIG. 9, a water-cooled combustion chamber wall 10 is used.
6, and air is supplied toward the flame from a secondary air outlet 107 in the center of the combustion chamber. This method has a relatively simple structure and can achieve high-load combustion. However, since the flame is constantly cooled by the combustion chamber wall 107, when the combustion amount is reduced, the amount of heat taken by the combustion chamber wall 107 increases more than the calorific value, and flame cooling occurs, the combustion reaction is frozen, and GO etc. Unburned fuel may be discharged as is. Therefore, TI)R cannot be set large.

Furthermore, there is a combustion device shown in FIG. 10 as another conventional example.

A flame port plate 109 is inserted into an inner cylinder 108 forming a combustion chamber, and an outer cylinder 110 is provided around the outer periphery of the inner cylinder 10B to form a secondary air chamber 111. The secondary air supplied here is ejected from the secondary air outlet 112 provided in the inner cylinder 108 toward the flame formed on the flame port plate 1 blade, and the flame is shortened by forced mixing. The aim is to achieve high-load combustion. In this case, flame is formed not only in the center of the combustion chamber but also in the vicinity of the inner cylinder 108. Therefore, the inner cylinder 108 becomes high temperature and is heat resistant.

At the same time that durability becomes a problem, the air within the secondary air chamber 111 is heated and expanded, and the internal pressure of the secondary air chamber 111 increases. Therefore, in order to send the required amount of air into the combustion chamber through the secondary air outlet 112, a fan with high blowing pressure is required, which has the disadvantage of increasing the size of the fan and increasing the noise level, resulting in a high load. The ability to respond is not sufficient.

As explained below, none of the conventional combustion devices intended for high-load combustion can simultaneously satisfy high-load combustion and expansion of TDR. Furthermore, the combustion device has become complicated, and miniaturization of the entire combustor including the fan has not been sufficiently pursued.

In the present invention, the combustion chamber wall is constructed of fins and water pipes, and a heat exchanger is provided with secondary air jet ports in multiple stages to stabilize the secondary air temperature (normal temperature level) and supply air according to the load. By doing so, the above-mentioned conventional drawbacks can be solved. An embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

1 and 2, 1 is a fan that supplies combustion air, and its supply port 1' is connected to the primary air passage 2 and the first passage 3. of the secondary air supply passage. It communicates with the second passage 4.

A movable damper 5.6.7 for air adjustment is provided in each passage 2, 3.4. The first passage 3 communicates with a secondary air chamber 8 provided downstream thereof and also serves as a pressure equalization chamber, and the second passage also leads to a secondary air chamber 9. The secondary air chambers 8 and 9 are in close contact with the fin and pipe integrated heat exchanger section 16 forming the combustion chamber 16, and communicate with secondary air jet ports 10.11 provided in a part thereof.

Reference numeral 13 denotes a burner main body, and the burner port 14 faces the combustion chamber 16, and is located in stages with the secondary air jet ports 10 and 11 in the combustion chamber 16 downstream of the burner port 14. Burner body 1
A primary air passage 2 communicates with the upstream side of the primary air passage 4, and a fuel injection nozzle 12 is installed in the passage. 17 is a water passage of the fin-pipe integrated heat exchanger 16, and 18 is an exhaust outlet provided downstream of the combustion chamber 15.

The operation 9 of the combustion apparatus of the present invention having the above-mentioned configuration will be described. A part of the combustion air supplied by the fan 1 passes through the water-air passage 2 and the movable damper 6.
After adjusting the supply amount to an appropriate amount, it is mixed with fuel injected from a fuel injection nozzle 12 provided midway to form an air-fuel mixture, which is sent to the burner body 13. Burner body 13
After further promoting mixing and rectifying the supplied air-fuel mixture, it is uniformly injected into the combustion chamber 15 from the flame port 14 to form a flame, while being supplied through the first passage 3 and the second passage. After the secondary air is adjusted to an appropriate supply amount by the movable damper 6.7, it enters the secondary air 8.9, passes through the secondary air outlet 10.11, and is uniformly formed in the combustion chamber 15. It erupts towards the flames. The flame is caused by this secondary air jet in the combustion chamber.

After exchanging heat with the fin-pipe integrated heat exchanger 17, it is discharged from the exhaust outlet 18. Water is normally used as the heat medium in the water passage 17, but depending on the purpose, any heat medium that can be transported such as oil or Freon gas may be used.

Next, the operation of the above combustion device will be explained using FIGS. 3 to 6. When the amount of combustion is large, the first passage 3. The movable dungeons C-6 and C-7 provided in the middle of the second passage 4 are opened to supply secondary air to the flame formed in the combustion chamber 15 from the secondary air jet ports 10.11 on the upstream and downstream sides. Spray it towards you. As mentioned above, the secondary flame contains a large amount of unburned components such as CO and H2, but the oxidation reaction is significantly accelerated by forced air supply and forced mixing by secondary air injection to this flame. Ru. In this way, as shown in Fig. 3, the secondary flame is spread over almost the entire area of the combustion chamber 15 due to the secondary air jet, and the combustion reaction is carried out in the entire area by fully utilizing the space of the combustion chamber 16. It will be done. Therefore, even if the combustion chamber 16 is small, large-capacity combustion is possible, and the load on the combustion chamber can be about 1 to 2θX 10'/hm3. In addition, the flame spread over almost the entire area inside the combustion chamber 16 undergoes sufficient heat exchange with the fin-pipe integrated heat exchanger 17, which greatly reduces the temperature rise of the secondary air inside the secondary air chambers 8 and 9. At the same time, the temperature rise at the secondary air outlet 10.11 is also small, and a stable secondary air supply is maintained. Therefore, the blowing pressure of the secondary air supply reservoir can be lowered, and the fan 1 is also made smaller and the noise is reduced.

On the other hand, if the flame is narrowed in this state, the secondary flame B will be strongly influenced by the secondary air supplied from the secondary air outlet 1o, as shown in FIG. 4, and will approach the flame outlet 14. An explanation will now be given based on FIG. 6, which shows the relationship between combustion chamber load and CO concentration. In the case of fuel with a low combustion rate or a fuel with a low diffusion rate, the rapid cooling caused by the secondary air injection from the secondary air jet port 10 to the flame base disrupts the balance with the heat generation rate due to the combustion reaction, causing the combustion reaction to slow down. Causes freezing and lifting. Therefore, as shown in curve B, when the combustion chamber load becomes low, unburned components such as GO are suddenly generated. In addition, if the fuel has a high burning speed, the flame may come into close contact with the flame nozzle 14 and cause the flame nozzle 14 to become red hot in the area indicated by the diagonal line b' of the curve, which may induce flashback. However, if the movable damper 6 provided in the first passage 3 is closed to reduce the air supply to the secondary air chamber 8 as in the present invention, the second flame C will be moved downstream as shown in FIG. The secondary air outlet 11 that supplies secondary air on the side expands and expands to the point where there is a lack of oxygen. In this case, unless there is rapid cooling of the flame base as in the case of FIG. 4, the flame becomes a stable flame. Therefore, the upstream side of the secondary air jet port 11 becomes a stable high-temperature region, so rapid flame cooling by the secondary air can be avoided, and even when fuel with a low combustion rate or a low diffusion rate is used, the combustion chamber 16 The flame C that spreads inside continues stable combustion. Furthermore, even in the case of a fuel with a high combustion speed, the two flames C cannot spread widely in the combustion chamber 16, and the effect of separating from the flame nozzle 14 and heating it is significantly reduced. Therefore, the red heat of the flame port 14 and the flashback phenomenon described above can be completely prevented. By satisfying these conditions, it is possible to obtain the characteristics of curve C shown in Figure 6 for any fuel, and achieve good combustion in a wide range of combustion chamber loads, that is, in a large TDR region. can do.

As is clear from the above description, the combustion apparatus of the present invention provides the following effects.

(1) Secondary air is injected into the flame, and by forced air supply and forced mixing, a combustion reaction occurs in almost the entire combustion chamber space, and this is promoted to achieve large-capacity combustion in a small combustion chamber. This makes it possible to downsize combustion equipment.

(2) A plurality of independent secondary air chambers are provided in the flow direction of combustion gas, and secondary air is supplied to the flame from all air outlets during large combustion, and from the downstream side during small combustion. By reducing the air supply, it is possible to realize combustion under high load and stable combustion under low load, and to widen the control range of TDR combustion.

(3) In addition to controlling the secondary air supply method described above, since there is no need to provide a guide plate or baffle inside the combustion chamber, the combustion chamber has a simple configuration and is suitable for various fuels with different characteristics. Both can maintain good combustion and make combustion devices universal.

(4) By configuring the combustion chamber wall as a heat exchange part and providing a jet nozzle, it is possible to prevent the temperature rise in the secondary air chamber, reduce air heating, and lower the internal pressure, resulting in low blowing pressure. Since a small fan can be used, noise is reduced and the entire combustor system can be made smaller and lighter. Furthermore, the cost advantage is also sufficient.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the overall configuration of an embodiment of the combustion device of the present invention, FIG. 2 is a perspective view of a cross-section of the combustion device, and FIG.
Figures 5 to 5 are cross-sectional views of the structure of the flame formed by the same combustion device, and Figure 6 is the TD in the same combustion device.
This shows one of the R characteristics, and is a comparative characteristic diagram of each combustion method showing the CO concentration with respect to the combustion chamber load. FIGS. 7 to 10 are cross-sectional views of the conventional example. 1...Fan, 3...1st aisle, 4.
・・・・Second passage, 8, 9...Secondary air chamber,
1o, 11... Secondary air outlet, 13...
...Burner body, 14... Flame mouth, 15...
... Combustion chamber, 16... Fin-pipe integrated heat exchanger, M, B, C... Two flames. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. Combustion chamber

Claims (1)

[Claims] A combustion apparatus comprising a combustion chamber, a device for supplying combustion air, and a means for introducing secondary air onto the flame port of a burner facing into the combustion chamber, the wall of the combustion chamber being formed by fins and pipes. 1. A combustion device comprising a heat exchanger processed by a method such as a heat exchanger, the heat exchanger being provided with a plurality of secondary air jet ports.