JPS631493B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is mainly used in household combustion appliances, etc., to increase the burner port load (burning amount kcal/h・mm ² per unit burner port area). This invention relates to a combustion device designed to be miniaturized.

Conventional configuration and its problems Conventionally, this type of combustion device has the following structure as shown in Fig. 1.
Flame ports 2 are provided at large intervals to increase the contact area with secondary air and promote combustion reaction.
Since the flame port load of No. 2 is high, that is, the ejection speed of the air-fuel mixture is high, the main flame A breaks the balance with the combustion speed and tends to blow out. The purpose was to stabilize the main flame A by increasing the combustion speed by decelerating the flame to create a stable flame B and heating the flame base of the main flame A.

In this configuration, as shown in FIG. 5, the flame holding set point b is at the same mixture ratio as the main flame set point a, and is close to the flashback region. Therefore, when the combustion amount is reduced, that is, when the injection velocity of the air-fuel mixture is reduced, the problem of flame-holding backfire or heating of the flame opening becomes a problem, so it is not possible to increase the throttling ratio. In addition, the higher the flame opening load, the narrower the stability area surrounded by the burnout and yellow flames, leading to problems such as the need for highly accurate combustion control.

Purpose of the invention The present invention solves such conventional problems,
The purpose is to make the combustor more compact by increasing the flame port load, improve the usability of the combustion device by increasing the combustion rate, and expand the stable combustion range to make combustion control easier. shall be.

Structure of the Invention In order to achieve this object, the present invention includes a mixing chamber in the center and a large number of flame ports above the mixing chamber, and a flame holding chamber and a secondary air chamber are sequentially arranged on both sides of the mixing chamber. The flame holding chamber has a vent with the secondary air chamber, a communication port with the mixing chamber, and a number of flame holding ports installed near the main flame opening, and the secondary air chamber has a ventilation hole with the secondary air chamber, a communication opening with the mixing chamber, and a number of flame holding ports installed near the main flame opening. A large number of secondary air ports opening into the combustion chamber are installed to blow air toward the flame formed above the main flame port on the side, and the fuel concentration for flame holding is lower than the fuel concentration for the main flame. This is what I did.

As a result, the yellow flame limit that occurs as a result of air shortage is reduced by the secondary air that is forcibly supplied to the main flame through the secondary air port, and the combustion reaction is promoted, so that the flame length is significantly shortened.

In addition, as the yellow flame limit recedes, the stability range is expanded, so the main flame mixture ratio is adjusted to near the conventional yellow flame limit, and the flame holding is adjusted to a point away from the backfire area by adjusting the vents and communication ports. It can be set separately. Therefore, even if the combustion amount is reduced and the air-fuel mixture injection speed is lowered, the flame stability will not pass through the flashback region or cause flame outlet heating.

Furthermore, even if the amount of supplied air decreases, the fuel concentration in the main flame increases, and the combustion speed decreases, the flame holding rate is still high enough because the mixture ratio is different from the main flame, and the flame base of the main flame is heated and combusted. The flame becomes more stable as it increases its speed. Conversely, when the amount of supplied air increases, the combustion rate decreases due to the excess air and the flame becomes unstable or blows out, but the flame is stable because the combustion rate of the main flame itself increases with the amount of air. , the unburned content of the flame holding is completely combusted in a part of the main flame.
Therefore, stable combustion can be achieved over a wide range of supplied air amounts.

DESCRIPTION OF EMBODIMENTS An embodiment in which the present invention is applied to a water heater will be described below with reference to FIGS. 2 to 5.

In Figures 2 to 4, reference numeral 1 denotes a fan that supplies combustion air, and its discharge port is connected to the burner body via a dividing plate 2 for dividing the supplied air into two secondary air and one primary air. Connected to 3. On the upstream side of the dividing plate 2, a nozzle 6 provided at the tip of a fuel pipe 5 with a control valve 4 in the middle is connected to the burner body 3.
are placed facing each other. The burner body 3 is bilaterally symmetrical, and includes a mixture passage 6 in the center, an inclined pressure equalizing plate 8 with a throttle opening 7, a mixing chamber 9 partitioned by the mixture passage 6 and the pressure equalizing plate 8, and a mixing chamber 9 on the downstream side thereof. is provided with a large number of main flame ports 10. Further, a pair of flame stabilizing chambers 11 and a secondary air chamber 12 are sequentially provided on both sides of the mixture chamber 9. The flame holding chamber 11 is communicated with a plurality of communication ports 13 with the mixture chamber, a vent port 14 with the secondary air chamber 12, and a plurality of flame holding ports 15 provided near the main flame port. Furthermore, the secondary air chamber 12 has a combustion chamber 1 on the downstream side of the main flame port 10.
A large number of secondary air ports 17 opened at 6 are in communication with each other. On the downstream side of the combustion chamber 16, there is a heat exchanger 18 having a large number of fins, and an exhaust hood 19.
and an exhaust port 20 are connected. Also, the combustion chamber 16
A water pipe 21 is provided on a part of the outer wall of the heat exchanger 18.
It is connected to the.

To explain the operation of the above configuration, the combustion air supplied by the fan 1 is divided into one primary air supplied into the mixture passage 6 in the center of the burner body 3 by the dividing plate 2, and one primary air supplied from both sides. The secondary air is divided into two secondary air chambers 12 which are supplied into the secondary air chamber 12 located at the secondary air chamber 12. On the other hand, after the fuel is set at a predetermined flow rate by the control valve 4, it is injected and supplied through the fuel pipe 5 from the nozzle 6 at the tip toward the burner body 3, and is supplied into the mixture passage 6 together with the primary air. Mixture passage 6
The primary air and fuel flow together in a mixed manner, and are uniformly supplied into the mixture chamber 9 through the throttle opening 7 by the pressure equalizing plate 8. Most of the air-fuel mixture in the air-fuel mixture chamber flows into the combustion chamber 16 through the main flame port 10, forming a main flame A above the main flame port. A part of the air-fuel mixture enters the flame holding chamber 11 through the communication port 13. Secondary air chambers 12 on both sides
Most of the secondary air supplied into the
7 and is ejected into the combustion chamber 16 toward the main flame A formed above the main flame port 10. A part of the secondary air flows into the flame holding chamber 11 through the vent 14, lowers the fuel concentration of the air-fuel mixture compared to the air-fuel mixture in the mixing chamber, and passes through the flame holding hole 10 into the vicinity of the main flame opening 10. It flows out into the combustion chamber 16 and forms a flame-holding B on the flame-holding port 10. After combustion, the exhaust gas exchanges heat with the water flowing in the water pipe 21 in the downstream heat exchanger 18, is collected in the exhaust hood 19, and is discharged to the outside air through the exhaust port 20.

At this point, secondary air is forcibly supplied to the main flame A from the secondary air port 17, so as shown in FIG. 5, the yellow flame limit resulting from lack of air recedes and the stable region is expanded. Further, the combustion reaction is promoted by forced mixing with the unburned components in the main flame A by the secondary air jet, and the flame length is significantly shortened, making it possible to downsize the combustion chamber. In addition, as mentioned above, the stable region is expanded by forcibly supplying secondary air to the main flame A.
The mixing ratio can be arbitrarily selected within a wide range,
For example, as shown in FIG. 5, it can also be set at a point c near the conventional yellow flame limit. On the other hand, by appropriately selecting the communication port 13 and the vent 14, the mixture ratio of flame holding B can be set at a point on the leaner fuel concentration side than the mixture ratio of main flame A and further away from the flashback region, for example, as shown in FIG. point d
Alternatively, it can be arbitrarily set at point d′. Therefore, in this case, if the combustion amount is continued to be reduced, flame-holding backfire or flame heating will start later than before, as in the case of point d', or will not occur at all, as in the case of point d. The aperture ratio can be increased. Furthermore, if the amount of supplied air fluctuates and decreases, as shown in Figure 4 A, the mixture ratio of main flame A increases and the combustion speed decreases and becomes unstable. The mixture ratio of flame holding flame B is still stable because it has a sufficiently high combustion rate, and the mixture ratio of flame holding flame B is stable.
The main flame A is stabilized because the flame base of the main flame A is heated to increase the combustion speed. On the other hand, when the amount of supplied air increases, as shown in Figure 4 (b), flame holding flame B decreases in combustion speed due to excess air and becomes unstable or blows out, but this time the mixture of main flame A Since the air temperature has reached an appropriate value and the combustion speed has become sufficiently high, it is stable, and the unburnt components of flame holding B, which has become unstable, are completely combusted in a part of the main flame. In this way, even if the amount of supplied air fluctuates, the mixture ratio of main flame A and flame holding flame B is set independently from each other, so one of them will form a stable flame, and the entire flame will be stabilized within a wide mixture ratio range. I will do it.

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

(1) The secondary air port is installed downstream of the main flame port toward the main flame, and the secondary air is forcibly supplied to the main flame and mixed with unburned components, resulting in air shortage. In addition to lowering the yellow flame limit and expanding the stability range, it also accelerates the combustion reaction and significantly shortens the flame length, making it possible to downsize the combustion chamber and downsize the combustion device.

(2) The air-fuel mixture that enters the flame holding chamber through the communication port is further diluted by the secondary air that enters through the vent, creating a flame holding ratio that is independent of the main flame. By appropriately setting the mixture ratio, it is possible to set the mixture ratio to a place that avoids the flashback range, and it is possible to increase the throttle ratio for the combustion amount.
The usability of the combustion device can be improved.

(3) Since the mixture ratio of the main flame and flame stabilization can be set independently of each other, even if the amount of supplied air changes, one of them will create a stable flame and stabilize the entire flame, making it acceptable when performing combustion control. Since a large variation can be taken, control can be easily realized.

(4) As mentioned above in (1), the stability region expands and the mixture ratio of the main flame can be set to the one with the higher fuel concentration, so as shown in Figure 5, the fuel concentration is low and the mixture injection speed is high. It is possible to avoid the oscillating combustion that occurs in the case of combustion, and in this case, it is possible to further increase the flame outlet load by expanding the stability region up to the blowout limit.

(5) Different mixing ratios of the main flame and holding flame widen the ignition range, making ignition operations easier.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional combustion device, Fig. 2 is a sectional view showing an embodiment of the combustion device of the present invention, Fig. 3 is a partially sectional perspective view of the same device, and Fig. 4 is a sectional view of the combustion device according to the present invention. In the explanatory cross-sectional diagrams, A shows the case where the amount of air is small, B shows the case where the amount of air is large, and Figure 5 shows the flame stability range and combustion device with the mixture ratio jet velocity on the vertical axis and the mixture ratio on the horizontal axis. It is a characteristic diagram showing the set point of. 9...Mixture chamber, 10...Main flame port, 11...Flame holding chamber, 12...Secondary air chamber, 13...Communication port, 1
4...Vent, 15...Flame holding port, 16...Combustion chamber, 17...Secondary air port, A...Main flame, B...Flame holding.

Claims (1)

[Claims] 1. A mixing chamber is provided in the center and a large number of main flame ports are provided on the downstream side thereof, and a flame stabilizing chamber and a secondary air chamber are sequentially arranged on both sides of the mixing chamber, and the secondary air is provided in the flame stabilizing chamber. A ventilation port with the chamber, a communication port with the mixture chamber, and a large number of flame holding ports provided near the main flame port are communicated with each other, and the secondary air chamber is provided with a vent on the downstream side of the main flame port. A combustion device in which a large number of secondary air ports provided to blow air toward a flame formed at the main flame port are communicated with each other so that the fuel concentration for flame holding is lower than the fuel concentration for the main flame.