JPS5926849B2 - Forced supply/exhaust type combustion control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a forced air supply/exhaust type combustion apparatus that stabilizes combustion by keeping the excess air ratio constant.

Conventional configuration and its problems FIG. 1 shows an example of a conventional forced air supply/exhaust type combustion apparatus.

Preventing incomplete combustion in forced air supply and exhaust combustion equipment,
In order to prevent the generation of CO2NOx, prevent dangers such as flame lift and bank fire, and maintain high thermal efficiency of equipment, it is necessary to maintain the excess air ratio within an appropriate range.

Therefore, in general, the air supply that supplies gas according to the combustion air volume.
A gas proportional mixing device is used.

In Figure 1, air
It has a gas mixing pipe 1 and a zero governor 2, and the pressure in the air passage upstream of the gas mixing pipe 1 is guided to the air chamber of the zero governor 2 to control the outlet pressure of the zero governor to be equal to the pressure in the air passage.

As a result, as shown in FIG. 2, a gas amount proportional to the air volume of the air passage is automatically supplied, so that the excess air ratio is kept constant regardless of changes in the air volume.

On the other hand, as described above, the amount of air that determines the combustion amount varies greatly due to voltage fluctuations of the fan 3, changes in the length of the supply and exhaust ducts 4 and 5, and the influence of strong winds that are applied to the supply and exhaust ducts 4 and 5.

Immediately after ignition, the temperatures of the burner 6, heat exchanger 7, combustion gas, etc. are low, and ventilation resistance is low.Furthermore, the temperature of the exhaust gas passing through the fan 3 is low, so the density is high and the rotation speed of the fan 3 remains the same. However, the actual air volume increases.

Depending on the conditions of the burner 6, heat exchanger 7, fan 3, etc., this value may reach 2 to 3 times the rated air volume.

For these reasons, when the air volume increases, the gas volume is supplied proportionally, resulting in an excessive combustion volume, leading to overheating of the equipment and an increase in combustion noise.

Furthermore, when the supply gas pressure is low or the supply and exhaust pipes 4 and 5
When the internal pressure of the combustion device increases due to strong winds, even if the air volume does not increase, if the pressure in the air passage becomes higher than the gas supply pressure, the outlet pressure of the zero governor 2 will not be able to follow the pressure in the air passage.

That is, since the required amount of gas is not supplied, the excess air ratio increases and exceeds the upper limit of the excess air ratio shown in FIG. 4, resulting in incomplete combustion.

This problem has a large effect on household gas fuels, especially city gas, where the gas supply pressure is low, as the minimum gas pressure is about 5 Qmi water column.

This has made it difficult to apply this type of combustion control device to household appliances.

Purpose of the Invention The present invention solves these conventional problems by eliminating changes in combustion amount due to changes in duct length, fan voltage, and strong winds, and eliminating overheating of equipment and combustion noise caused by excessive input immediately after ignition. The purpose is to suppress the increase in excess air ratio, especially at low gas times, to maintain a stable combustion value, and to make it possible to use low gas pressure fuel for household appliances.

Structure of the Invention For the above-mentioned purpose, the present invention provides an air/gas mixing pipe having an air nozzle that generates a differential pressure depending on the air volume and a gas nozzle that generates a differential pressure depending on the gas volume. A gas pressure regulator is provided in the air passage for guiding the pressure upstream of the air nozzle and adjusting the outlet pressure connected upstream of the gas nozzle to be equal to the pressure upstream of the air nozzle, and further detecting the air volume and adjusting the air volume setting value. An air volume stabilizing device is provided to control the air volume compared to the air flow rate, and a differential pressure detector is provided to detect the differential pressure between the pressure upstream of the air nozzle and the outlet pressure of the gas pressure regulator, and the output of the differential pressure detector is provided. The air volume setting value of the air volume stabilizing device is changed according to the configuration.

According to this configuration, when the supply gas pressure is sufficiently high, the outlet pressure of the gas pressure regulator is approximately equal to the pressure upstream of the air nozzle, and air and gas are mixed at a constant ratio determined by the opening ratio of the air nozzle and gas nozzle. .

On the other hand, the air volume is maintained approximately equal to the air volume setting value because the air volume is detected by the air volume stabilizing device and compared with the air volume setting value, and feedback control is performed.

When the gas supply pressure decreases to be lower than the pressure upstream of the air nozzle, the outlet pressure of the gas pressure regulator will be lower than the pressure upstream of the air nozzle and a differential pressure detector output signal will be generated.

The output signal of the differential pressure detector works to reduce the air volume setting value of the air volume stabilizing device, and as a result, the air volume is reduced and the pressure upstream of the air nozzle becomes about the gas supply pressure, which stabilizes the excess air ratio. has.

DESCRIPTION OF EMBODIMENTS Embodiments of the present invention will be described in detail below with reference to FIGS. 5 and 6.

In FIG. 5, an air nozzle 13 and a gas nozzle 10 are provided in the gas mixing pipe 11, and a zero governor 12 is provided upstream of the gas nozzle 10 to constitute a gas pressure regulator.

The pressure upstream of the air nozzle 13 is guided to the back pressure chamber 16 of the zero governor 12 by a pressure guiding pipe 14 .

The diaphragm 15 of the zero governor 12 adjusts the valve body of the gas passage in response to the difference between the pressure in the back pressure chamber 16 and the pressure at the outlet 17, and adjusts the pressure at the outlet 17 to the pressure in the back pressure chamber 16, that is, the upstream pressure of the air nozzle 13. It is adjusted to be approximately equal to .

An air volume stabilizer 20 is provided in the air passage upstream of the air nozzle 13.
is provided to detect the air volume and adjust the air volume to be equal to the air volume setting value.

The pressure upstream of the air nozzle 13 and the pressure at the outlet 17 of the zero governor 12 are introduced to the differential pressure detector 21, which generates an output according to the differential pressure and changes the air volume setting value of the air volume stabilizer 20.

With this configuration, when the pressure at the inlet 22 of the zero governor 12 is sufficiently higher than the upstream pressure of the air nozzle 13, the pressure at the outlet 17 is adjusted to be approximately equal to the pressure upstream of the air nozzle 13, and the opening ratio of the air nozzle 13 and the gas nozzle 10 is adjusted. Since air and gas are mixed at a constant ratio determined by , the burner 23 can maintain safe combustion.

When the air volume is changed by changing the air volume setting value of the air volume regulator 20, the gas volume automatically follows.

During this time, as mentioned above, the pressure upstream of the air nozzle 13 and the pressure at the outlet 17 of the zero governor 12 are adjusted to be almost equal, so the differential pressure detector 21 to which the differential pressure is guided generates an output. Therefore, the air volume setting value of the air volume stabilizer 20 is not changed by the differential pressure detector 21.

Now, if the gas supply pressure decreases or the supply and exhaust pipe (not shown) receives strong winds and the internal pressure of the equipment increases as a whole even though the air volume does not change, the pressure upstream of the air nozzle 13 will be lower than that of the zero governor 12. The pressure at the inlet 22 becomes higher than the pressure at the outlet 17.
The pressure does not exceed the pressure at the inlet 22 even when the valve is fully opened, and cannot follow the upstream pressure of the air nozzle 13.

Here, the differential pressure detector 21 detects the pressure difference and generates a signal to reduce the air volume setting value of the air volume stabilizer 20, and the air volume stabilizer 20 adjusts the air volume so that the output of the differential pressure detector 21 becomes smaller. Adjust.

Therefore, the air volume can be reduced until the upstream pressure of the air nozzle 13 approaches the pressure at the outlet 17 of the zero governor 12, thereby suppressing an increase in the excess air ratio.

FIG. 6 shows a specific configuration example of the air volume stabilizing device 20 and the differential pressure detector 21, and the same parts as in FIG.

In FIG. 6, the air volume stabilizing device 20 and the differential pressure detector 21 have an integrated structure.

Air entering from the air passage 24 passes through the valve 25 and reaches the upstream 19 of the air nozzle 13.

The valve body 25 is connected to the upstream pressure chamber 33 and the pressure guide path 34 of the air nozzle 13.
Air nozzle 1 to which the downstream pressure of air nozzle 13 is guided by
The pressure upstream of the air nozzle 13 is connected to the air volume detection diaphragm 26 that partitions the downstream pressure chamber 35 of the air nozzle 13.
It is also connected to a differential pressure detection diaphragm 27 that partitions a pressure chamber 28 branched from 4 and guided by a pressure guide pipe 30 and a pressure chamber 29 to which the pressure at the outlet 17 of the zero governor 12 is guided by a pressure guide pipe 31.

The differential pressure detection diaphragm 27 is arranged to act in a direction to close the valve body 25 when the pressure of the air nozzle 13 is higher than the pressure of the outlet 17 of the zero governor 12.

The valve 25 to which the diaphragms 26 and 27 are connected is biased by a spring 32 in the direction in which the valve opens.

The biasing force of the spring 32 is adjusted by rotating the knob 36.

In the above configuration, the effective area of the air volume detection diaphragm 26 is AdAl, the force it receives is FdA1, the effective area of the differential pressure detection diaphragm 27 is AdB, and the force it receives is FdB.
, the force of the spring 23 is Fs, and Fd41. Assuming that FdB is positive upward, Fs is positive downward, and the constant of the differential pressure generated with respect to the air volume QA of the air nozzle 13 is 1, then P33 is the pressure of the pressure chamber 33, and P35 is the pressure of the pressure chamber 35.
, P28 is the pressure in the pressure chamber 28, P2. is pressure chamber 2
9 pressure.

The relationship between the differential pressure ΔP generated at the air nozzle and the air volume QA is ΔP-P
Since 33-P35- is 1·QA2, it can be expressed as follows.

Here, P28 is the upstream pressure of the air nozzle 13, P2. is equal to the pressure at the zero governor outlet 17.

When the gas supply pressure is higher than the pressure upstream of the air nozzle 13, the zero governor 12 works to keep it at P28 and P29, and almost no force is generated on the differential pressure detection diaphragm 27.

In other words, equation (3) becomes as follows, and the air volume is stabilized to be determined by the force Fs of the spring 32, the area AdA of the diaphragm 26, and the constant of the air nozzle 13 of 1.

That is, even if there is a change in ventilation resistance in a portion not shown or the influence of strong wind, the differential pressure generated in the air nozzle 13 is fed back and the air volume is stable.

Next, when the inlet pressure P2□ of the zero governor 12 becomes lower than the upstream pressure of the air nozzle 13, the zero governor 1
The pressure at the outlet 17 of No. 2 is lower than the upstream pressure of the air nozzle 13, that is, P28>P2O.

Therefore, in equation (3), AdB・(P28P29)
The force is applied in the opposite direction to the force Fs of the spring 32, and the set air volume is reduced.

As a result, the air volume is reduced by the valve 25 until the result reaches P28 (air nozzle upstream pressure) that satisfies equation (3).

The resulting value of (P28 P2O) remains as a change in the excess air ratio, but it can be made sufficiently small by increasing the area AdB of the diaphragm 27, and the change in the excess air ratio is smaller than when no correction is made. It can be kept small.

Effects of the Invention According to the present invention, an air leading type air/gas proportional mixing device consisting of a mixing pipe and a gas pressure regulator is provided with an air volume stabilizing device that detects the air volume and controls the air volume by comparing it with an air volume setting value. ,
Furthermore, by configuring the air flow rate setting value of the air flow stabilizer to be changed by the output of the differential pressure detector that detects the differential pressure between the air nozzle upstream pressure of the mixing tube and the outlet pressure of the gas pressure regulator, the gas supply pressure can be adjusted. When the temperature is high enough, the air volume is feedback-controlled to the set value, so disturbances such as changes in ventilation resistance due to temperature, changes in duct length, and the effects of strong wind are absorbed to maintain the air volume at the set value, preventing equipment failure due to excessive input. In addition to preventing overheating and an increase in combustion noise, when the internal pressure of the equipment increases due to a drop in gas pressure or strong wind, a differential pressure detector detects the control error of the zero governor and adjusts the air volume setting value of the air volume stabilizer. It is possible to suppress the increase in excess air ratio and maintain stable combustion.

This makes it possible to apply the air-gas proportional mixing device to equipment that uses household city gas fuel with low supply gas pressure.
We can provide safe and stable equipment.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional forced air-fuel combustion system, Figure 2 is an explanatory diagram of the operation of an air/gas proportional mixing system, and Figure 3 shows the amount of combustion immediately after ignition of a conventional forced air/gas combustion system. FIG. 4 is a characteristic diagram showing the combustion performance of the burner, FIG. 5 is a block diagram showing one embodiment of the present invention, and FIG. 6 is a block diagram showing another embodiment of the present invention. be. 10...Gas nozzle, 11...Air
Gas mixing pipe, 12...Zero governor, 13...
... Air nozzle, 20 ... Same amount stabilizer, 2
1... Differential pressure detector, 23... Burner,
24...Air passage, 32...Spring.

Claims (1)

[Claims] 1. An air/gas mixing pipe that joins the air passage and the gas passage and supplies mixed gas to the burner has an air nozzle that generates a differential pressure according to the air volume and a gas nozzle that generates a differential pressure according to the gas volume. , there is a gas pressure regulator upstream of the gas nozzle that guides the pressure upstream of the air nozzle and adjusts its own outlet pressure to be equal to the pressure upstream of the air nozzle, and the air passage detects the air volume and sets an air volume setting value. and a differential pressure detector that detects a differential pressure between the pressure upstream of the air nozzle and the outlet pressure of the gas pressure regulator. A forced air supply/exhaust type combustion control device configured to change the air volume setting value of the air volume stabilizing device based on the output of the detector.