JPS605856B2 - Forced air supply/exhaust combustion control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for stabilizing the excess air ratio in a forced air supply/exhaust type combustion device, and is capable of continuously and widely changing the gas input while stabilizing the excess air ratio. It is an object of the present invention to provide a control device which can further reduce pressure loss at maximum input.

Since the operation of using a gas-air mixing tube and a zero governor as a method for stabilizing the excess air ratio of a fully premixed combustor has been repeatedly explained in previous applications, the explanation will be omitted in this specification.

When stabilizing the excess air ratio by absorbing various fluctuation factors, the accuracy required on the governor side is related to the differential pressure depending on the air volume generated by the gas-air mixing pipe, so if the performance of the governor is limited, A pressure difference above a certain level is required.

An example is now shown in Figure 3. When the combustion air volume is constant and the differential pressure between the gas nozzles is small, the tolerance of the gas governor, which controls the gas outlet pressure in conjunction with the air pressure, decreases. For example, if the gas nozzle differential pressure is 5 sides ^q, when the gas pressure is 2.8 sides ^q higher than the air pressure, the excess air ratio becomes the lowest permissible excess air ratio allowed for the combustion section. However, the gas nozzle differential pressure 1
If there is a difference, the gas pressure will be 5.6 sides higher than the air pressure, and the minimum allowable excess air ratio will be reached, making it easier for the gas governor. As will be described later, this gas nozzle differential pressure corresponds to a component that reduces the static strength depending on the air volume caused by the ejector effect of the air nozzle in the gas-air mixing tube inserted into the air circuit. Therefore, in order to increase the gas nozzle differential pressure, it is necessary to throttle the air nozzle in order to enhance the ejector effect. As a result, the pressure loss in the air circuit increases, so it is necessary to select an air nozzle that provides a good balance between the performance of the gas governor and the performance of the blower.
By the way, this device has the feature that as long as the combustion air volume increases, the gas input will automatically increase at the same rate.
If the diameter of the air nozzle is determined to ensure the required gas nozzle differential pressure at the minimum input, there is a problem in that the pressure loss in the air circuit increases significantly as the input increases. For example, according to experiments, if the gas nozzle differential pressure requires at least 5 legs (from the point of view of gas governor performance, it is difficult to manufacture anything below this value)
At this time, the pressure loss due to passing through the gas-air mixing pipe is approximately 3 cm. Now, if we increase the input to 4 times,
The pressure loss is about 48 sides Aq, and a large blower is required. The present invention attempts to compensate for these drawbacks and to continuously change the input. An embodiment of the present invention will be described below with reference to the accompanying drawings. A combustion blower 1 sucks air from an air supply duct 2 and sends it to an air volume regulator 3.

Subsequently, it passes through the gas-air mixing section 4, mixes with gas at an appropriate ratio, burns at the combustion section 5, passes through the heat exchanger 6, and is discharged from the exhaust duct 7. The gas side then passes through a cock 8, a gas governor 9, a gas amount regulator 10, and a solenoid valve 11 to enter the gas-air mixing section. Furthermore, gas for the pilot burner is supplied to the pilot burner 13 via a pilot gas governor 12, and combustion air for this purpose is introduced through a pipe 14 from the upstream side of the air volume regulator 3. Further, the air volume regulator 3 is composed of a butterfly valve-shaped continuous regulator 15, and a switching device in which a bypass path 17 and a switching solenoid valve 16 are arranged in parallel. Reference numeral 18 denotes a solenoid valve coil, which acts as a switch and changes the air volume in steps by turning it on and off.

Next, the gas-air mixing section 4 is composed of an air nozzle 19 and a low-pressure chamber 20 and a mixing chamber 21 generated by the ejector effect of the air nozzle 19. A gas nozzle 22 faces the low pressure chamber 20. The gas amount regulator 1 has a configuration in which a bypass nozzle 23 and a switching gas solenoid valve 24 are connected in parallel, and the resistance of the gas circuit is switched by turning the coil 25 on and off. Coils 18 and 25 are connected in parallel and actuated simultaneously by opening and closing switch 27. In addition, the gas governor automatically adjusts the air pressure between the continuous regulator 15 and the solenoid valve 16 so that the air pressure is transmitted through the pressure equalization pipe 26 and the gas outlet pressure is equal to this pressure. The difference between the outlet pressures of the low pressure chamber 20 and the governor 9 is the pressure at which gas is to be supplied, and this is the gas nozzle differential pressure.
This is equal to the difference between the air pressure in the low pressure chamber 20 and in front of the functional solenoid valve 16. Now, when the switching solenoid valve 16 is open, the pressure drop in this part is ignored, so the gas nozzle differential pressure is only the bottom part of the static pressure due to the ejector effect of the air nozzle 19, and this is the curve B shown in Figure 4. It is. At air volume q2, the gas nozzle differential pressure is 5 yanagi^q. Continuous regulator 15
When the nozzle is gradually opened and fully opened, the nozzle differential pressure increases to q3 and reaches the nozzle differential pressure of 2. In this way, since the gas input of the same ratio changes in accordance with the change in the combustion air volume from q2 to q3, the input can be continuously controlled by operating the continuous regulator 15. However, when the input is reduced to below q2, the gas nozzle differential pressure decreases, and the error of the gas governor becomes relatively large.Therefore, there is a risk that fluctuations in the excess air ratio will increase, making it dangerous to reduce the air volume below q. It is. However, when the switch 27 is opened and the switching solenoid valve 16 and the switching gas solenoid valve 24 are closed, the resistance on the air side increases, so the gas nozzle differential pressure changes to curve A. In other words, the differential pressure increases even with the same air volume q2, but at the same time the switching gas solenoid valve 24
Since the bypass nozzle 23 is closed, if the bypass nozzle 23 is appropriately determined, it can be designed so that the excess air ratio does not change. and,
By operating the continuous regulator 15, the number can be narrowed down to q. In Figure 4, things that could only be changed between q3 and q2 can now be changed from q3 to q. If the gas nozzle range is from 5th side ^q to 2nd ratio Aq, the change width is 1/2
This means that it has been expanded from 1'4 to 1'4. Also, considering q as a standard, the blower's capacity can change up to 2 times as it is, 4
It is now possible to double the amount. Next, an example of the relationship between the continuous regulator 15, the sliding solenoid valve 16, and the switching gas solenoid valve 24 will be described.

In Fig. 5, the continuous regulator 15 is in the fully open position, and the cam 28, which rotates coaxially with this, is not pressing the switch 27 and 27 is on, so both the air side and the gas side are fully open. So here we are at point A. Then, when b rotates about 90 degrees, it reaches the maximum aperture position and becomes the mouth point. If the switch is turned a little further, the switch is opened as shown in c, and both electromagnetic valves are closed, moving to curve B in Fig. 4, resulting in two points. If you turn it further 90 degrees, it will look like ○ and become point C. That is, a rotation of 180 degrees results in an input change of E-Low-Knee-Ha.
In that case, since the nozzle differential pressure on the gas side is at least 5 side ^q, the gas governor has a pressure difference of 12.8 side ^q, -1.
It is good if the error is less than 5 Yanagi^q. Of course, for points A and C, the tolerance can be expanded even further. If the air volume is reduced to the position q while keeping curve B in Figure 4, the gas nozzle differential pressure will drop to the 1.5 side ^q, so the gas governor will be 10.8 leg^q, 0.45 skin Aq. Precision is required. This was an unreasonable value considering various fluctuation factors. Figures 3 and 4 describe an example.
Depending on the design, the range of governor tolerance changes and the values of the A and B curves also change. However, for the reasons mentioned above, it is an advantageous method to change a part of the air volume regulator in steps to expand the range of possible input changes. Furthermore, another example of the air volume regulator is shown in FIG. In the figure, 27 is the switch shown in FIG. 2, and 29 is a damper that is always biased in the opening direction by a spring 30, and the degree of damping can be changed by a rod 31. Further, 32 is a cam, which is shown unfolded in the same figure, but is a round cam whose mouth surface and mouth surface are connected, and can be rotated from a to c by operating a shaft (not shown). Now, point a is at point A shown in FIG. 4 because the damper is fully open and the switch is on. Next, in state b, the damper is at the maximum aperture position and reaches the exit point in Figure 4. If you turn it slightly from here, it will reach position c, and the damper will be fully opened all at once, but since switch 27 is turned off, it will be at point c in Figure 4. If you turn it further, the damper will be at its maximum aperture with the switch 27 turned off, resulting in two points. If you turn it further, it will be in the state a again and return to point a. In other words, by operating the round cam 32, the air volume (i.e., gas input) can be changed continuously in the order of A -> 口 -> C -> 2. Although this method is a little more complicated, it is easier to change the amount of air by operating the round cam 32 than in the case of Fig. 5. It can be said that the input changes are continuous and smooth. In this embodiment, switching is performed in two stages, but the range of input adjustment can be further expanded by increasing the number of stages of the switching device that switches the air volume and gas volume in steps. That is, if there are N stages, the governor, mixing section, and blower can be changed up to N times the change ratio when only the continuous regulator is used. Moreover, it is of course possible to use a mechanical method for switching between the air side and the gas side without using a solenoid valve. Furthermore, the continuous regulator does not need to be located upstream of the gas-air mixing section, and may be located at any location and in any structure as long as it can change the overall combustion air volume. As explained above, while stabilizing the ratio of gas and air within a certain range to match the performance of the combustion section, it is possible to secure a wide range of changes in the gas input, making it possible to proportionally control the input according to the load. This increases the effectiveness of the combustion device. 2. To obtain a wide variation range of gas input, there is no need to increase pressure loss in the air circuit, and the blower, governor, and mixing section can remain the same.

3. Easy to operate and continuous gas input control possible.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of a forced air supply/exhaust combustion control device showing an embodiment of the present invention, Fig. 2 is an electrical wiring diagram thereof, Fig. 3 is a diagram showing the permissible error of the gas governor, and Fig. 4 is a combustion air volume. 5 and 6 are diagrams showing an example of the air volume regulator. 4...Gas/air mixing section, 3...Air volume regulator, 9...Gas governor, 10...Gas volume regulator, 16, 17...Switcher A switching solenoid valve and a bypass path constitute, 15...a continuous regulator. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Scope of Claims] 1. A gas-air mixing section, a plurality of air volume regulators that adjust the amount of air entering the gas-air mixing section, a gas governor having an outlet gas pressure according to the pressure on the air side; A forced air supply/exhaust combustion control device comprising an air volume regulator and a gas volume regulator interlocked with the gas/air mixing pipe. 2 A part of the air volume regulator is composed of a switching device that can change in steps, and this switching device is installed immediately before the gas-air mixing pipe,
The forced air supply/exhaust combustion control system according to claim 1, wherein a gas governor is made to respond to the air pressure flowing into the switching device, and a gas amount regulator is linked to the switching device. 3. The forced air supply/exhaust device according to claim 1 or 2, wherein the air volume regulator is constituted by a continuous regulator capable of continuous adjustment and a switching device capable of stepwise changes. Combustion control device. 4. The forced air supply/exhaust combustion control device according to claim 3, wherein the switching device is driven in conjunction with the operation of the continuous regulator. 5. Each time the switch switches, the continuous regulator returns to the fully open position or
The forced intake/exhaust combustion control device according to claim 3, wherein the forced air supply/exhaust combustion control device is at the maximum throttle position.