JPS6327606B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention provides a combustion device for household combustion appliances such as water heaters and space heaters that uses a fan or the like to perform forced combustion and shorten the flame length to reduce the size of the combustion part. It is related to.

An example of a conventional combustion apparatus of this type is one having a configuration as shown in FIGS. 7A and 7B. This is mainly a liquid fuel combustion device, but it is constructed by forming independent vaporization chambers, an upper vaporization chamber 102 and a lower vaporization chamber 103, which are separated by a partition wall 101 that is equipped with a vaporization heater 100 inside. A cylindrical vaporizer 104 is provided, and each vaporization chamber 102, 103 of this vaporizer 104 is provided with a spray nozzle 10.
A two-system liquid fuel supply system is provided in which liquid fuel 5, 106 and liquid feed pumps 107, 108 are independently supplied through oil feed pipes 109 which are branched from each other.
Various partition plates 11 are placed on the top of the vaporized body 104.
A conical burner plate 112 equipped with a large number of flame opening grooves 111 is connected to the upper part of the 0 to form a first fuel mixing system, and a communication hole 113 provided at the lower part of the vaporizer 104 and the vaporizer 104 A burner plate 1 equipped with a large number of slit-like flame ports 114 on both sides of the upper part of the burner plate 1.
15 to form a second fuel mixing system.
Further, a pair of left and right secondary air chambers 116 are provided on the outside of the burner plate 115, and an injection plate 118 provided with a large number of side injection ports 117 for secondary air is provided at an angle at the upper part. . The combustion air is supplied to the ventilation duct 11 by a fan (not shown).
9 to the combustion section.

In the case of this combustion device, the combustion air supplied from the ventilation duct 119 is supplied to the left and right secondary air chambers 1.
16 and the upper vaporization chamber 102 and lower vaporization chamber 103 in the vaporizer 104 as secondary air and primary air, respectively.

On the other hand, the liquid fuel passes through an oil feed pipe 109, is pressurized by liquid feed pumps 107 and 106, and is supplied to upper and lower vaporization chambers 102 and 103 by spray nozzles 105 and 106, respectively. The liquid fuel supplied into the upper vaporization chamber 102 as the first fuel mixing system is heated and vaporized by the vaporization heater 100, mixes with primary air while passing through the partition plate 110, and reaches the burner plate 112. Enguchi groove 11
1 and forms a central flame. Similarly, the liquid fuel supplied into the lower vaporization chamber 103 as the second fuel mixing system is vaporized and flows out from the lower part of the vaporization body 104 through the communication hole 113 and flows between the vaporization body 104 and the secondary air chamber 116. While passing through the gap, it mixes with the primary air, reaches the burner plate 115, flows out from the flame port 114, and forms side flames on both sides of the vaporized body 104. On the other hand, the secondary air is in the secondary air chamber 11
6 passes through the side injection ports 117 and is supplied to the flames on the burner plates 112, 115 from both sides.

In this way, the flame forms independent central flames and side flames on the burner plates 112 and 115 through independent fuel supply systems, so the so-called TDR (Turn Down Ratio) allows the flame to be adjusted while maintaining stable combustion. ) The range can be further changed by changing the initial flow rate setting ratio of the spray nozzles 105 and 106 by stopping either one of the liquid feed pumps 107 and 108 to create only one of the central flame and side flame. By doing so, by stopping one of the liquid feed pumps 107 and 108, it becomes possible to significantly expand the originally possible TDR range.

However, at the maximum combustion amount, the burner plate 112
A central flame is formed above, and side flames are formed on the burner plates 115 on both sides, so that the flame width becomes wide. Therefore, the secondary air supplied from the side injection ports 117 provided on both sides has difficulty reaching the central flame, and therefore the central flame extends long in the downstream direction, and yellow tends to appear. Therefore, the combustion chamber is required to be long in the downstream direction. FIG. 4 shows this in more detail. The yellow curve shows that if you increase the secondary air injection velocity _V2 , the stoichiometric ratio [= (supplied fuel) / (supplied primary air amount)]
/ (unit fuel) / (theoretical air amount of unit fuel)] retreats to the larger side, and the stable blue fire region expands, as revealed by experiments by the inventors. That is, when v ₂ is increased, the yellow curve a of the conventional example in FIG. 4 retreats to the position shown by the curve of the present invention, and the stable blue frame region expands. Also, the ejection speed of secondary air
If v ₂ is the same, the distance from the secondary air outlet to the flame center is small. Conventional yellow curve b
It was also found that the stable blue frame area is expanded compared to the yellow curve a, which has a large distance.
Therefore, in the combustion apparatus shown in FIGS. 7A and 7B, the distance between the center of the central flame and the side injection ports 117 is large, so the yellow curve for the same secondary air injection velocity V ₂ is as shown in FIG. 4. It exhibits characteristics like curve a, with a narrow stable range and a long flame. on the other hand,
If the width of the burner plates 112, 115 is narrowed while keeping the combustion amount constant, the load at the flame port will increase and the mixture injection speed V _nix will increase, so the position where secondary air is supplied to the center of the flame will be more downstream. As it moves to the side, the flame becomes longer and a larger combustion chamber is required.

It is conceivable to solve this problem by increasing the secondary air jet velocity _V2 , but this has the following two problems.

First of all, in order to increase _V2 , a large fan with high blowing pressure is required. Also, increasing the rotation speed with a small fan can cause noise problems.

The second problem is that the flame base becomes unstable due to the influence of large V ₂ , resulting in an unsteady flame, which causes the so-called "green burning" phenomenon in which the flame zone breaks intermittently and unburned components such as CO are generated. It is an occurrence. FIG. 5 illustrates this. The flame forms a stable blue flame within the range surrounded by both the limit lines of the yellow curve and the green curve described above. Here, in a burner with a large flame load, the yellow color disappears with a small V ₂ , but at the same time the V ₂ at which "raw burning" occurs also becomes small. Therefore, if a large _V2 is applied to a burner that simply increases the load on the burner, "raw burning" will occur.

In addition to the above two problems, when using fuel with a high combustion speed, the flame may not reach the burner plate 11.
Combustion is completed near 2,115. Therefore, the burner plate 112 located particularly in the center is heated by the surrounding flames and the temperature of the flame opening tends to rise, which tends to cause flashback. Therefore, it is not suitable for use with fuels that have a high burning rate.

Furthermore, since two fuel supply systems are provided, two spray nozzles and two liquid pumps are required, which becomes a major cost increase factor.

Another conventional example is a combustion apparatus having a configuration as shown in FIG. This has a mixture chamber 122 inside the main body 120, which has a communication hole 121 at the top.
and a secondary air chamber 125 equipped with a secondary air outlet 124 at the tip of the constriction part 123 are separated by a partition wall 126, and triangular flame ports 127 inclined downstream are provided on both sides of the constriction part 123. A passage body 128 provided with
It is supported by both ends of 7.

In this combustion device, the air-fuel mixture that has flowed out from the air-fuel mixture chamber 122 through the communication hole 121 passes through the gap between the passage body 128 and the main body 120, is ejected into the combustion chamber from the flame port 127, and is ejected along the combustion chamber wall of the main body 120. form a flame. On the other hand, the secondary air increases the flow velocity at the constriction part 123 from the secondary air chamber 125 and the secondary air outlet 124
The injection is supplied to the flames on both sides.

In this way, when the flame port is divided into two parts and secondary air is supplied from the center to the flames on both sides, the distance from the secondary air outlet to the position of the flame where secondary air is to be supplied (in this case, the combustion chamber The distance to the flame along the wall can be set short. Therefore, the characteristics of the yellow curve for the same secondary air ejection velocity V ₂ are as shown by curve b in FIG. 4, and the stable combustion region is somewhat expanded compared to that of the conventional example. Furthermore, since the flame length is significantly shorter than that of the conventional example, the combustion chamber can be made smaller.

Here, the flame port becomes thinner as it approaches the combustion chamber wall, and the ventilation resistance of the mixture becomes smaller than in the center, so the mixture injection speed on the combustion chamber side increases as it approaches the combustion chamber wall. growing. The flame thus formed will extend along the walls of the combustion chamber. In this case, if the amount of combustion is reduced, if the fuel has a slow combustion rate, it will be cooled on the wall of the combustion chamber, resulting in so-called flame extinction, resulting in incomplete combustion. On the other hand, if the fuel has a high combustion speed, combustion will be completed near the flame nozzle, so the flame nozzle will be heated. However, since the flame port on the wall side of the combustion chamber has a small heat capacity and a large amount of combustion, the flame port is susceptible to abnormal heating and is likely to cause flashback.

In this case as well, increase the flame outlet load at the maximum combustion amount.
It is possible to solve the above problems by increasing V _nix and simultaneously increasing the secondary air jet velocity V ₂ , but
In this case as well, as explained in the prior art example, the problem of increasing the size of the fan and occurrence of "green burning" occurs.

As explained above, conventional combustion devices are all about miniaturization of the combustion device, miniaturization of the entire combustor including the fan, universality of the device for different types of fuel, expansion of TDR, and expansion of the stable combustion range. It was not possible to satisfy both of these requirements at the same time.

The present invention satisfies the requirements of miniaturization of the combustion device and miniaturization of the fan, expansion of TDR, and universality, which conventionally conflicted with each other and could not satisfy all the performance requirements at the same time. The aim is to realize a wide combustion device.

In order to achieve this object, the present invention provides an air chamber consisting of a large air chamber and a small air chamber communicating with the large air chamber and adjacent to a flame outlet, and a flame outlet consisting of a large number of flame outlets arranged in a straight line. A large number of small nozzles are provided on both sides of the flame nozzle and communicate with a small air chamber near the flame nozzle, and a large number of small jet nozzles are provided on the downstream side of the flame nozzle and communicate with a large air chamber and in the downstream direction of the combustion gas flow. A large number of large air outlets are provided on an open and inclined plane, and the large air chamber and the small air chamber are communicated with each other by a pressure reducing means, so that the air ejection speed from the small air outlet is lower than the air ejection speed from the large air outlet. It is also a small structure.

With this configuration, the flame formed on the flame nozzle flows from the large air chamber through the pressure reducing means into the small air chamber adjacent to the flame nozzle, and the low-velocity flame that is supplied from the small nozzle near the flame nozzle flows into the small air chamber adjacent to the flame nozzle. Since air is supplied to the flame base by the air flow, a steady and stable flame is formed due to a gentle reaction. In addition, in the downstream region, air is forced into the flame from both sides by a large air vent that is open in the downstream direction of the combustion gas flow and jets out at high speed from the large air chamber at high speed without being depressurized. It is supplied to accelerate the combustion reaction and shorten the flame length. Here, the flame base is also affected by turbulence due to the high-speed airflow, but because a steady flame is formed due to the stabilizing effect of the flame base mentioned above, the flame zone does not break and "live combustion" occurs. does not occur either. In other words, the flame is stabilized by the low-velocity air flow from the small nozzle and prevents "raw burning", while the high-speed air flow from the large nozzle prevents the occurrence of yellow, and the air supply method corresponds to the phenomena that define the limits of each. By realizing this, the stable combustion range is expanded. In addition, the flame nozzle is indirectly cooled by the air flowing through the large and small air chambers on both sides, so even when using fuel with a high combustion rate that reduces the amount of combustion, the flame nozzle may become abnormally heated and cause flashback. Even in the case of fuel with a low combustion speed, the flame is surrounded by an air layer and does not come in contact with the walls of the combustion chamber and extinguish the flame.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 6 in the case where it is applied to a water heater.

In Figures 1 to 3, 1 is a fan that supplies combustion air, and at its discharge port there is a dividing plate that divides the combustion air into primary air and several types of secondary air according to the opening area ratio. It is connected to the burner body 3 via 2. On the upstream side of the dividing plate 2, a nozzle 6 is provided at the tip of a fuel pipe 5 having a solenoid valve 4 in the middle. The burner body 3 consists of a symmetrical molded body 7 and a passage body 8 in the center. The molded body 7 includes a flame port 10 consisting of a large number of slit-shaped flame ports 9, a small air chamber 12 equipped with a large number of small jet ports 11 near the flame port 10, and a small air chamber 12 provided with a large number of small jet ports 11 on the downstream side of the flame port 10. A large air chamber 15 having a large number of large jet ports 14 is provided on the inclined surface 13, and the small air chamber 12 and the large air chamber 15 are provided with a plurality of communication ports 1 having a small diameter and large passage resistance as pressure reducing means.
6 and communicate with each other. On the other hand, the passage body 8 is provided with a large air chamber 17 and a constriction section 18 on the downstream side, and a small air chamber 20 with a large number of small nozzles 19 near the flame opening section 10 on both sides of the constriction section. is provided. A large number of large jet ports 21 are provided at the tip of the throttle portion 18, and a plurality of communication ports 22 are provided between the small air chamber 20 and the large air chamber 17. Further, between the passage body 8 and the molded body 7, a mixture passage 23 is formed on the upstream side of the passage body 8, and gap portions 24 are formed on both sides.
Note that the passage body 8 is supported by the flame port 10 from both sides via a stepped portion 25 provided on the outside of the small air chamber 20.

A combustion chamber 26 and a number of fins 27 protruding into the combustion chamber are provided on the downstream side of the burner body 3, and an exhaust passage 28 and an exhaust port 29 are provided further downstream.
is connected. Further, a water pipe 30 is provided around the outer periphery of the combustion chamber 26 to exchange heat and supply hot water.

Next, to explain the operation of the above configuration, the combustion air supplied by the fan 1 is transferred to the dividing plate 2.
The air is divided into primary air, which is supplied to the flame port 10, and three types of secondary air, which are supplied to the passage body 8 and the molded bodies 7 on both sides, depending on the opening area ratio. On the other hand, fuel is supplied through the electromagnetic valve 4 and through the fuel pipe 5, injected from the nozzle 6 at the tip, and supplied to the mixture passage 23 in the burner body 3 together with the primary air dividedly supplied from the dividing plate 2. . The fuel and primary air are uniformly mixed while passing through the mixture passage 23 , and further uniformly distributed while passing through the gap 24 , and flow out into the combustion chamber 26 through the flame port 9 to form the flame port 10 .
Form a flame on top. On the other hand, the secondary air supplied into the molded bodies 7 provided in pairs on both sides enters the large air chamber 15 and enters the large air outlet 14 provided on the inclined surface 13.
High-speed secondary air is injected and supplied to the downstream side of the flame formed on the flame port 10 through the flame opening. Further, a part of the secondary air in the large air chamber 15 is depressurized and its flow rate is restricted while passing through the communication port 16 which has a small diameter and large passage resistance, and is uniformly distributed within the small air chamber 12 while the flow velocity is reduced. The flame port 10 passes through the small spout 11
Low-velocity secondary air is supplied to the flame base formed above, forming a gentle and stable steady flame at the flame base. Similarly, the secondary air supplied into the passage body 8 is uniformly distributed while passing through the constriction part 18 from the large air chamber 17, and passes through the large jet port 21 to send high-speed secondary air to the downstream side of the flame. Supply injection. Similarly, a part of the flow rate is restricted by the communication port 22, and the small air chamber 2
Evenly distributed while being decelerated within 0, the small jet nozzle 1
9 to supply low velocity secondary air to the flame base. The combustion exhaust gas that has completed combustion within the combustion chamber 26 is
After exchanging heat with the fins 27, it passes through the exhaust passage 28 and is discharged to the outside air from the exhaust port 29. Furthermore, heat transferred from the combustion exhaust through the combustion chamber wall and the fins 27 is transferred to a water pipe 30 provided on the outer periphery of the combustion chamber 26 and the fins 27, and is supplied to hot water.

In this way, the flame formed on one flame port 10 is supplied with high-speed secondary air from both sides of the flame port, so that the flame reaches the center of the flame at a lower secondary air flow velocity V ₂ than before. Secondary air will be supplied. That is, the flame length is also significantly shorter than before. Conventionally, this was dealt with by increasing V ₂ in order to expand this stability range and shorten the flame length.
In this case, the blowing pressure increases, so the size of the fan increases.

In the present invention, by shortening the flame length in this manner, it is possible to realize miniaturization of the combustion section and the combustion device including the fan.

In addition, a flame with a large primary air ratio (small stoichiometric ratio) has a high combustion speed and is itself relatively stable, resulting in a flame shape as shown in Figure 3 (b).
A flame with a small primary air ratio (high stoichiometric ratio) has a low combustion speed, and oxygen is supplied by diffusion from the surroundings, making it an unstable flame that is strongly affected by the surrounding flow conditions. The flame form is as shown by A in the figure.

However, when the primary air ratio is increased, so-called oscillatory combustion occurs, and the combustion speed is high and the flame comes into close contact with the flame nozzle, which increases the flame nozzle temperature and makes flashback more likely to occur. Therefore, the primary air ratio is generally set low. At this time, the flame base becomes unstable as described above, but in the present invention, low-velocity secondary air is supplied to the flame base through the small jets provided on both sides of the flame mouth, so the flame base remains calm. A steady stable flame of reaction will be formed. FIG. 5 compares this with the conventional characteristics. Due to this stabilization of the flame base, the air-fuel mixture injection speed V _MIX
In other words, even when the combustion amount is small, a stable flame is formed even for a large V ₂ , and the limit of "live burning" that occurs when the flame zone is ruptured by the secondary air flow recedes toward the larger V ₂ . The stable combustion range expands. Furthermore, since the flame base remains stable even if the primary air ratio changes, similar results can be obtained over a wide range of primary air ratios.

Furthermore, the flame opening part is large, which is provided on both sides.
Because it is indirectly cooled by the secondary air flowing in the small air chamber, there is no flashback caused by flame opening heating, which tends to occur with fuel with a high combustion rate, and the flame does not come into contact with low-temperature parts such as the combustion chamber walls. Therefore, quenching, which tends to occur with fuels with low combustion speeds, does not occur. FIGS. 6A and 6B are shown as an example for explaining these. Let's take the CO/CO ₂ value, which has been standardized as a standard for evaluating flammability, and examine its permissible range. When examining the allowable air supply range for a certain combustion amount, it generally shows the characteristics shown in A in the figure, and if the allowable value is set to 0.005, upper and lower limits as shown in the figure appear. Graph B in the figure is an example of examining this over a wide range of combustion amounts. In the figure, the characteristics of the conventional combustion apparatus shown in FIGS. 7A and 7B and FIG. 8 are also indicated by a and b in the figure, respectively. In case a, a large TDR can be achieved, but the flame is elongated, resulting in high-load combustion, making it difficult to downsize the combustion chamber.On the other hand, in b, the flame is short, allowing for high-load combustion and a smaller combustion chamber, but it is difficult to extinguish the flame. It is not possible to increase the TDR due to flashbacks and flashbacks. Compared to these conventional examples, the present invention does not cause flashback or extinction even when fuels with different combustion speeds are used as described above, making the combustion device universal, and at the same time
TDR can be expanded. In the embodiment, the flame spout is divided into two parts, but it goes without saying that a single flame spout may be used in the same manner.

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

(1) The flame formed on the flame port is supplied with secondary air from the large jet nozzle of the large air chamber that opens and slopes in the downstream direction of the combustion gas flow, so the ejection speed of the secondary air is low. The secondary air is sufficiently supplied to the center of the flame, promoting the combustion reaction, shortening the flame length, and making the combustion chamber smaller.In addition, the blowing pressure of the fan is also low because the secondary air injection speed is small, and the blowing pressure of the fan is also small. The entire combustion device including the combustion equipment can be downsized.

(2) The flame formed on the flame port enters the small air chamber via the pressure reducing means from the small jet ports provided on both sides, and is pressure-equalized and rectified, and then low-velocity secondary air is supplied. As a result, a steady and stable flame is formed at the flame base due to a gentle reaction, and "raw combustion" does not occur even when affected by high-speed secondary air flow.
Since a stable flame is formed in a wide range even when the primary air and secondary air fluctuate, the variation in allowable air volume when performing combustion control can be increased, making control easier.

(3) Because the flame nozzle is indirectly cooled by the secondary air flowing in the large and small air chambers on both sides, it is possible to prevent flame nozzle heating and flashback caused by fuel with a high combustion speed when the combustion amount is reduced. Furthermore, since the flame does not touch low-temperature parts such as the walls of the combustion chamber, extinguishing of fuel with a low combustion rate does not occur, so it is possible to expand the TDR and make the device universal for different types of fuel at the same time.

[Brief explanation of the drawing]

Fig. 1 is an overall sectional view showing a combustion device according to an embodiment of the present invention, Figs. 2 and 3 are partial sectional perspective views of Fig. 1, and Fig. 4 shows the behavior of the yellow line due to secondary air. Figure 5 is a comparison diagram comparing the raw combustion limit with the conventional example, Figure 6A is a characteristic diagram of CO/CO ₂ characteristics with respect to excess air ratio,
Figure 6B is a characteristic diagram showing the reduction in size of the combustion chamber and TDR performance with respect to fan airflow, Figure 7A is an overall sectional view of the conventional example, Figure 7B is a perspective view of the same, and Figure 8 is another example. FIG. 2 is a sectional view of a conventional example. 9...flame mouth, 10...flame mouth part, 12,20...
Small air chamber, 15, 17... Large air chamber, 11, 19
...Small spout, 14,21...Large spout.

Claims (1)

[Claims] 1. An air chamber consisting of a large air chamber and a small air chamber that communicates with the large air chamber and is adjacent to a burner port is provided on both sides of a burner port that is made up of a large number of linearly arranged burner ports, and A large number of small nozzles communicating with the small air chamber are provided in the vicinity, and on the downstream side of the flame nozzle part, a flat surface is provided which communicates with the large air chamber and opens in the downstream direction of the combustion gas flow. A large number of large air outlets are provided, and the large air chamber and the small air chamber are communicated with each other through a pressure reducing means, so that the speed of air ejection from the small air outlet is adjusted to the speed of air ejected from the large air outlet. A combustion device configured smaller than the .