JPS5921456B2 - Forced supply/exhaust type 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 and maintaining a good combustion state in a forced air supply/exhaust type combustion device. It is possible to change the gas input continuously and over a wide range, and
The purpose is to obtain a control device with less pressure loss in the ventilation circuit at maximum input.

A fully premixed combustor requires that the ratio between the amount of gas and the amount of combustion air be kept within permissible limits.

However, in practice, this ratio (hereinafter referred to as excess air ratio) tends to become unstable due to external factors such as gas pressure and voltage, and factors associated with changes in gas amount to make gas input variable. A constant-pressure gas governor that simply stabilizes the gas pressure used in gas appliances cannot accomplish its purpose.

For this purpose, it is effective to always keep the air pressure and gas pressure approximately equal and mix them, which often uses a zero governor and a mixing tube.

This method is convenient because it automatically changes the gas input by simply changing the amount of combustion air, but it is difficult to keep the gas pressure always equal to the air pressure, so a certain amount of error must be accepted.

This error results in an error in the excess air ratio, so to reduce this effect, as will be explained later, it is necessary to improve the performance of the mixing pipe, which is accompanied by an increase in the ventilation pressure loss of the mixing pipe. The design points were selected based on the relationship.

However, in order to make the gas input variable, it is necessary to change the combustion air volume, but if the mixing pipe specifications are selected so that the excess air ratio due to the error between gas pressure and air pressure is within the allowable value at the lowest air volume, the mixing pipe Since the pressure loss increases in proportion to approximately the square of the combustion air volume, the pressure loss at the maximum air volume becomes extremely large.

For this reason, there was a problem that the blower became large and the noise became louder.

The present invention eliminates these conventional drawbacks, and embodiments thereof will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a combustion air supply path, which is divided into two directions by a branching section 2, each of which is connected to a mixer 6 and 6 for air and gas.
'to go into.

The mixers 6, 6' are of the same construction, and air is ejected from the air inlet chambers 3, 3' through air nozzles 4, 4', reducing the pressure level in the low pressure chamber 5.5' by its ejector effect.

Burner 7 is then passed through a gradually expanding diffuser.
Enter.

The heat combusted here is transferred to the outside by a heat exchanger 8, and the exhaust gas is passed through an exhaust pipe 9 and sent to an exhaust passage 11 by a blower 10.
It is discharged to.

The waste then enters the gas governor 15 through the passage 14 after the cock 13 and passes through the gases 16, 16' to the waste nozzles 17, 17 facing the low pressure chambers 5, 5' of the mixers 6, 6'.
It is supplied by two gas circuits 12° 12' leading to '.

Note that the gas governor 15 is introduced through an air pressure equalization pipe 18 of the branch section 2, and operates so that changes in air pressure and changes in gas governor outlet pressure are synchronized.

Reference numeral 19 denotes a damper provided in the air supply path 1, which allows continuous changes in the amount of combustion air.

An air valve 20 is provided in the air supply path of the mixer 6', and an orifice 21 is provided in the air supply path of the mixer 6 so as to provide the same resistance as when the valve is opened.

Next, the operation of the system using the mixer as shown in FIG. 1 will be explained.

The symbols are defined as follows. Pressure in air inlet chambers 3 and 3' of mixer Pai〃 Pressure in low pressure chamber Pnδ Output log gas pressure of gas governor Pzδ Combustion air amount Qcy Gas amount Qg 'Tolerable lower limit of excess air ratio M〃 of M groove π〃 Allowable upper limit Group M Now, the pressure difference Pa1-Pnδ between the air inlet chamber and the low pressure chamber due to the ejector effect of the air nozzles 4 and 4' is approximately proportional to the square of Qc as shown in FIG.

Also, the amount of gas is determined by the gas valves 16, 16' and the gas nozzle 17.
It is determined by the resistance of 17', the gas governor outlet pressure Pzδ, and the pressure P of the low pressure chamber, and the pressure difference Pzδ− as shown in FIG.
Pn.

is approximately proportional to the square root of

That is, when the gas governor 15 operates so that Pa1=Pzδ, M is determined only based on the dimensional relationship, and can be made constant regardless of the air volume or gas volume.

However, the outlet pressure of the gas governor varies depending on the gas flow rate and also varies depending on the supply gas source pressure.

Furthermore, if we include production errors, Pa
It is difficult to maintain 1Pnδ.

Now, if we have the relationship Pzδ-Pai+ΔP, , which brings about a change in M.

Figure 7 shows that when Qc is 100%, Pa1-Pnδ-248q, and when the reference air excess ratio is 1.5 when ΔP=O, ΔP2±27/l! If Il −A Q, then
This figure shows how M changes when Qc is lowered for the purpose of reducing gas input.

That is, since Pai PnE decreases as Qc decreases, the change in M becomes larger as the input becomes lower.

Next, when the permissible limit of M is MW, M7#=,", what will be the permissible value of ΔP, that is, the permissible error range of the gas governor, for the determined Pa1-Pnδ?
Shown in the figure.

Once the tolerance of the governor error and the excess air ratio of the burner are determined, the minimum required value of the pressure difference Pa 1 -Pno in the mixers 6, 6' is also determined.

If the input is made variable, the air nozzles 4, 4' will be designed to ensure the minimum required differential pressure when the amount of combustion air corresponds to the minimum human power.

The pressure drop seen from the blower 10 of the mixer 6, 6' is based on the lowest input, and if the input is made variable up to 2 times, the pressure drop will be 4 times, and if the input is made variable up to 3 times, the pressure loss will be 9 times.

For example, the minimum required pressure difference Pa1-Pno is 107 MI
As AQ, the pressure loss of mixer 6, 6' at that time is 67NI
If I A Q, if the input change is tripled, the pressure loss will increase to 54 Aq.

This is not preferable because it increases the size of the blower itself and increases noise.

The above is a general explanation of the system using a mixer and a seven-piece governor, but the present invention solves the problems of increased pressure loss and increased size of the blower that occur when the input variation width is expanded, and also improves its operation. It embodies the power of a signal.

As shown in FIG.
2' are in parallel, air valve 20 and gas valve 16'
(both entering the mixer 6') are closed at the same time.

In Fig. 1, 22 and 26 are differential pressure detectors, chamber 23 is connected to air inlet chamber 3, chamber 24 is connected to low pressure chamber 5, chamber 27 is connected to air inlet chamber 3', and chamber 28 is connected to low pressure chamber 5'. The differential pressure switches 25 and 29 are connected to each other, and the pressure difference therebetween opens and closes the differential pressure switches 25 and 29.

Now, the minimum required pressure difference (Pai-Pno) of the mixer determined by the gas governor 15 and the burner 7 will be expressed as Pn, and the mixer pressure loss in that case will be expressed as Pl.

Assuming that the two mixers bear the input equally, and that the input is variable up to 1/2 for each mixer, the air valve 2
0 and the opening/closing of the gas valve 16', the input can be changed as shown in the following table.

That is, when the total input becomes 1/2, the air valve 20 and the gas valve 16' are closed to stop the mixer 6'.

As a result, the pressure drop in the mixer can be varied up to 1/4 as a whole, but the pressure drop in the mixer is only 4 Pl at most.

If this were a single mixer, the pressure drop would reach 16 Pl.

Now, the gas valves 16 and 16', the air valve 20, and the differential pressure switches 25 and 29 are connected via the operation switch 30 as shown in FIG.

The operating differential pressure of the differential pressure switch 29 is set to be somewhat higher than the operating differential pressure of the differential pressure switch 25.

In this state, when the blower 10 is being operated and the dial 19 is fully open and the input is 100%, the differential pressure switches 29 and 25 are both closed, and both mixtures are operating.

Next, the damper is closed and the air amount decreases, and when it drops to a certain value, the differential pressure in the mixer 6, 6' decreases, and the differential pressure switch 29 opens accordingly.

As a result, the air valve 20 and the gas valve 16' are closed, so the mixer 6' is stopped.

Since the input has become approximately 1/2, the damper 19 is fully opened again (the operation is continued using only the return mixer 6).

In order to further reduce the input, the tambour 19 is closed, the differential pressure switch 25 is opened, and the gas valve 16 is also closed, allowing air to pass through the mixer 6, but combustion is stopped.

At startup, if the air flow is above the set level, the differential pressure switch 25 is activated.
is closed and mixer 6 starts automatically, but mixer 6' does not start because air valve 20 remains closed.

Therefore, if the starting switch 31 is connected in parallel with the differential pressure switch 29 and short-circuited for a moment, the air valve 20 will open and the differential pressure switch 29 will be kept energized, so that the mixer 6' will also operate. Become.

In this way, the air valve 20
, gases 16 and 16' are automatically opened and closed, the operating differential pressure of the differential pressure detectors 22 and 26 is set to be somewhat higher than the above-mentioned minimum required differential pressure Pn, and the operating differential pressure of the detector 26 is set to be slightly higher than the minimum required differential pressure Pn. If the pressure is set somewhat higher than the differential pressure of the detector 22, the air valve 20 will be closed when the air amount decreases, and the differential pressure of the force of the detector 22 will increase. can be avoided from stopping.

FIG. 3 shows another embodiment, in which there is only one differential pressure detector 22, the chamber 23 is connected to the air inlet chamber 3, the chamber 24 is connected to the low pressure chamber 5, and the differential pressure switch 25 operates differently. The pressure is set to a certain value equal to or higher than the aforementioned Pn.

The electric circuit is as shown in Figure 4, where 30 is an operation switch, 31
is a starting switch, which is a switch that opens to the 32 side by pushing or pulling when starting, and returns to the 33 side when released.

A relay coil 34 closes a relay switch 35 when energized.

Now, when the operating switch 30 is closed, the blower 10 starts operating, and when the air volume exceeds a certain level, the differential pressure switch 25 closes, the gas valve 16 opens, and the mixer 6 starts operating.

Furthermore, when the start switch 31 is operated to energize the 32 side, the relay coil 34 is activated, so the relay contact 35 closes, self-holding the relay, and opens the air valve 20.

Next, when the start switch 31 is released and connected to the 33 side, the gas valve 16' will also start operating.

When the air volume decreases and the differential pressure switch 25 turns off once, the relay coil 34 becomes de-energized and the relay switch 35 turns off.
opens, the air valve 20 gas valve 16' closes and the mixer 6'
stops operating, but since the air valve 20 is closed, the differential pressure increases again, the differential pressure switch 25 closes, and the gas valve 16 opens, allowing only the mixer 6 to continue operating.

In this way, control can be performed using the differential pressure of the mixer 6, which is not provided with the air valve 20.

As described above, according to this embodiment, it is possible to reduce the load on the blower 10 and expand the input variation range, and furthermore, the air valve and gas valve are adjusted so that the pressure difference does not fall below the minimum pressure determined by the governor accuracy. Since the opening and closing are controlled, a stable combustion state can always be obtained.

In addition to damper 19, blower 1 can be used to change the input.
A similar effect can be obtained using a method of zero speed control.

Also, the input to the mixer does not have to be equal; the point is,
Air valve 2.0 to ensure that the differential pressure does not go below the minimum required pressure Pn.
, gas valves 16 and 16' may be opened and closed.

As described above, the present invention includes a plurality of mixers arranged in parallel, a plurality of gas circuits that control gas to the mixers,
Stabilizing the excess air ratio by having at least one air valve that opens and closes the air passage to the mixer,
It is possible to vary the gas power continuously and over a wide range.

Moreover, the pressure loss in the ventilation circuit at the maximum input is also not small, which is an extremely excellent effect.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of a forced intake/exhaust type combustion control device showing an embodiment of the present invention, Fig. 2 is an electric circuit diagram of the same device, and Fig. 3 is a forced intake/exhaust type combustion control device in another embodiment. A schematic configuration diagram, FIG. 4 is an electric circuit diagram of the device, and FIGS. 5 to 8 are explanatory diagrams. 3.3'-... Air inlet chamber, 5,51-...
・Low pressure chamber, 6゜6'-...Mixer, 12...
...Gas circuit, 15...Gas governor, 16,
16'-...Gas valve, 20...Air valve,
22.26...Differential pressure detector.

Claims (1)

[Scope of Claims] 1. A plurality of mixers arranged in parallel to mix air and gas, each having an air inlet chamber and a low pressure chamber formed by a nozzle section that produces a high-speed flow downstream of the air inlet chamber; a plurality of gas circuits each having a gas valve in which a governor is inserted to control the gas pressure in accordance with the air pressure, the end of which is led to the low pressure chamber of each of the mixers, and - opening and closing of the air passage to the power mixer The air valve is configured to simultaneously close the air valve and the gas valve of the gas circuit entering the mixer when the pressure difference between the air inlet chamber of the mixer and the low pressure chamber becomes less than a set value. Forced air supply/exhaust type combustion control device 2 Differential pressure detectors that operate based on the differential pressure between the air inlet chamber and the low pressure chamber are installed in the mixer with and without air valves, and each air valve is activated by the signal from each detector. and a gas valve or only a gas valve is configured to open and close, and the operating pressure difference of a differential pressure detector of a mixer with an air valve is set higher than that of a differential pressure detector of a mixer without an air valve. A forced air supply/exhaust type combustion control device according to scope 1. 3 A differential pressure detector is installed that operates on the differential pressure between the air inlet chamber and the low pressure chamber of a mixer without an air valve, and when the differential pressure decreases due to a decrease in air volume, the signal from the differential pressure detector is used to reduce the air in the mixer with an air valve. Close the valve and the gas valve in the gas circuit that goes into the mixer at the same time, and if the differential pressure decreases with the air valve and gas valve closed, close the gas valve in the gas circuit that goes into the mixer that does not have an air valve. A forced air supply/exhaust type combustion control device according to claim 1, which is configured to be closed.