JPS6014974B2 - Forced supply/exhaust type combustion device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a forced air supply/exhaust type combustion device that supplies combustion air with a blower, mixes it with gas fuel, burns it with a burner, and exchanges the generated heat with a fluid or solid. be.

More specifically, the present invention relates to a device that has means for adjusting the amount of gas in response to combustion air, and that manually or automatically adjusts the amount of combustion, and that changes the air-fuel ratio according to the amount of combustion. It is characterized by: An object of the present invention is to downsize a blower without reducing the amount of air blown, or to downsize a heat exchanger without reducing heat exchange efficiency. Still another object of the present invention is to prevent corrosion of a heat exchanger due to striped fog. Still another object of the present invention is to improve the controllability of the air-fuel ratio when the combustion amount is low. FIG. 1 shows a conventional example of the characteristics of the air-fuel ratio with respect to the combustion amount of a combustion device in which combustion air is supplied by a blower and the combustion amount can be adjusted.

That is, as shown by the solid line A, the air-fuel ratio is designed to remain constant regardless of the increase or decrease in the combustion amount. If the performance of the air flow rate adjusting device or the gas amount adjusting device is not sufficient, the air-fuel ratio will fluctuate as shown by the broken line B or the broken line C, but ideally it will be configured to have the characteristics shown by the solid line A. However, the combustion device having the characteristics shown by the solid line A had the following drawbacks. That is, the first drawback is that when the combustion amount increases at a constant air-fuel ratio, the amount of combustion air must also increase at a constant ratio to the combustion amount, resulting in pressure loss in the burner, heat exchanger, and air supply and exhaust passages. This requires a large blower. The second drawback is that when the combustion amount changes at a constant air-fuel ratio, a relatively large heat exchanger with a large heat exchange area is required to maintain high heat exchange efficiency when the combustion amount is large. If is small, the thermal efficiency is too high, causing fog to form inside the heat exchanger, causing corrosion and resulting in poor durability. The present invention eliminates these conventional drawbacks, and embodiments thereof will be described below.

FIG. 2 shows the relationship between combustion amount and air-fuel ratio according to the present invention. As shown in FIG. 2, the present invention maintains the air-fuel ratio high when the amount of combustion is small, and keeps the air-fuel ratio low as the amount of combustion increases. A specific configuration for achieving the above purpose is shown in FIG. FIG. 3 shows an air-fuel ratio control device, in which a differential pressure generating section 2 having an air nozzle 1 is provided in the combustion air ventilation path, and the gas pressure of the main diaphragm 5 to which the control valve 4 of the gas pressure regulator 3 is fixed. A high pressure section 8 of the differential pressure generating section 2 is placed in a diaphragm chamber 7 opposite to the chamber 6.
The gas pressure regulator 3
The main diaphragm 5 balances the output pressure with the pressure of the high pressure section 8 of the differential pressure generating section 2 to control the air-fuel ratio. The relationship between the amount of combustion air and the amount of gas mixed is as described below. That is, the pressure of the high pressure part 8 of the differential pressure generating part 2 is Pai, the pressure of the low pressure part 12 is Pno, the pressure of the inlet part 13 of the gas pressure regulator 3 is Pzz, and the pressure of the outlet part 14 is Pz.
zo, the weight of the movable parts such as the control valve 4, balance diaphragm 11, and main diaphragm 5 is W, the displacement based on the position of the control valve 4 in close contact with the valve seat 15 is x, and the displacement of the control valve 4 is x.
When = 0, the load of the spring 10 is F, the spring constant of the spring 10 is k, and the effective pressure receiving area of the balance diaphragm 11 is Ab
, the effective pressure receiving area of the main diaphragm 5 is Am, the area on which the gas inlet pressure Pzz and the gas outlet pressure Pzo act on the control valve 4 is Av, the specific weight of air is ya, the specific weight of gas is y
g, and the acceleration of gravity is g, then in the combustion air side differential pressure generating section 2, the combustion air amount Qa is Qa2KaJ (P
a←Pn.

) '11. Here, Ka is a constant determined by the shape of the air nozzle 1. On the other hand, gas amount Q
g is Qg=KgJ plan (PZ.

-Pn. ) ■Represented by. Here, Kg is a constant determined by the shape of the gas nozzle 16. In the gas pressure regulator 3, the pressure Pai of the high pressure section 8 of the differential pressure generating section 2 is introduced into the diaphragm chamber 7, so that the following equation holds true. PzoAv ten PziAb ten PzoAm+V
V=PziAv+PzoAb+PaiAm+F−kx'
3' Here, the effective area Ab of the balance diaphragm 11, the gas inlet pressure Pzz and the gas outlet pressure Pzo of the control valve 4 are calculated.
If the area Av on which is applied is set equal, the formula [3' becomes,
PZ.

=Pai+Forget(F-w-kX) '41■Formula '2}
Substituting into the equation, Qg=Kg false JPai-W-(F-kX
)-Pn.

'5'Am air fuel ratio R is It is expressed as

Figure 4 shows the combustion amount and air nozzle differential pressure Pai.
-Pno, and Pai-Pn
o increases in proportion to the square of the combustion amount.

Now, when the combustion amount is small (point S in Figure 4), F-
When adjusting with spring 10 so that kxs<W, {6
}From the formula. Here, as is clear from Figure 4, 4.
Since Pai-Pno at the time of combustion is relatively small, Qs>1
Therefore, Rs becomes a high value. Next, if the combustion amount is large (
At point L), the formula '6} becomes.

Displacement illusion m-xs of control valve 4 and spring constant k of spring 10
' Since it is small, the value of k (xm - total) can be ignored,
Due to the significant increase in Pai and Pno, Q becomes 1, and the air-fuel ratio R becomes a low value. That is, the air-fuel ratio characteristics shown in FIG. 2 are obtained. Figure 5 shows the relationship between the gas outlet pressure Pzo and the air nozzle high pressure part pressure Pai relative to the gas amount Qg of the gas pressure regulator, that is, the combustion amount. Becomes a characteristic. FIG. 5 shows the characteristics of a gas regulating device using another method for obtaining the air-fuel ratio characteristics as shown in FIG.

In FIG. 5, B is a normal characteristic, and C is a characteristic adopted in the present invention. In other words, the configuration is such that the gas outlet pressure increases as the gas flow rate increases. Specifically, it is obtained by providing a venturi pipe at the gas outlet and guiding the pressure of the low pressure part to the diaphragm chamber 7. Fifth
It is clear that by using a gas pressure regulator with the characteristics shown in the figure, the air-fuel ratio becomes low when the combustion amount is large.
FIG. 6 shows another embodiment of the present invention, and is a block diagram for controlling the amount of combustion air in response to the amount of gas (that is, the amount of combustion).

The amount of gas adjusted by an electrical or mechanical gas amount controller is converted into a plexus pressure using a differential pressure generator such as an orifice or venturi tube, and then converted into an electrical amount by a pressure converter, which is then sent to the combustion air ventilation path. The signal is compared with the signal from the installed differential pressure generating section, and the difference is compared with a reference voltage, and the trigger circuit controls the conduction of the thyristor to change the amount of electric power supplied to the outside of the motor, thereby controlling the rotation of the blower. The air-fuel ratio is adjusted by controlling the number of fuels. If the reference voltage is 0, the air-fuel ratio is 7th.
As shown in the figure, Rs, Pm, R, the air-fuel ratio becomes constant. That is, for example, when the amount of air is large, the output of the pressure transducer on the air side becomes high, which reduces the amount of electric power supplied to the motor, lowers the rotational speed of the blower, and operates to reduce the amount of air. The air-fuel ratio is determined by the shape of the differential pressure generating section provided on the gas or air side. However, if the reference voltage is kept at a constant positive value, when the combustion amount is small, the amount of combustion air is large, that is, the air-fuel ratio is high, and when the combustion amount is large, the air-fuel ratio approaches the shape determined by the shape of the differential pressure generating part.
The air-fuel ratio can be lowered by setting the differential pressure generating section so that the air-fuel ratio is lower. That is, the characteristics shown by the solid line in FIG. 7 are obtained. B is a normal characteristic, and C is a characteristic adopted in the present invention.

In other words, the configuration is such that the gas outlet pressure increases as the gas flow rate increases. Specifically, this can be obtained by providing a venturi pipe at the gas outlet and guiding the pressure of the low pressure part to the diaphragm chamber 7. It is clear that by using a gas pressure regulator having the characteristics as shown in FIG. 5, the air-fuel ratio becomes low when the combustion amount is large. As described above, according to the present invention, the following excellent effects can be expected.

1. When the combustion volume is large, the air-fuel ratio is low, so the amount of combustion air decreases, the required air volume of the blower decreases, and the blower becomes smaller.

0 Since the air-fuel ratio is low when the combustion amount is large, the heat exchange efficiency is high, and the heat exchanger can be made smaller for the same heat exchange efficiency. m Since the air-fuel ratio is high when the combustion amount is small, fog formation does not occur due to an excessive increase in thermal efficiency, and corrosion of the heat exchanger can be prevented.

W Since the air-fuel ratio is high when the combustion amount is small, the air nozzle differential pressure Pai-Pno becomes a large value as shown in Figure 4.■
As is clear from the equation, the air-fuel ratio is highly stable against fluctuations in gas inlet pressure.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the characteristics of conventional air-fuel ratio control, Fig. 2 is a graph showing the characteristics of the air-fuel ratio control of the present invention, Fig. 3 is a sectional view showing an embodiment of the present invention, and Fig. 4 is a graph showing the characteristics of the air-fuel ratio control of the present invention. A graph showing the relationship between the combustion amount and the differential pressure between air nozzles according to the invention, FIG. 5 is a graph showing the characteristics of a gas pressure regulator according to another embodiment of the invention, and FIG. A block diagram showing the embodiment, FIG. 7 is a graph showing air-fuel ratio characteristics. 1...Air nozzle, 2...Differential pressure generating section, 3...Gas amount control device (gas pressure regulator),
8...High pressure part, 12...Low pressure part, 16
...Gas nozzle. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. A burner, a heat exchanger that exchanges heat with combustion gas from the burner, a blower that supplies combustion air, and a gas amount control that adjusts gas fuel in response to the amount of combustion air. Forced supply/exhaust combustion that has a device or an airflow control device that adjusts the amount of combustion air in response to the amount of gas, and lowers the air-fuel ratio when the amount of combustion is large, and increases the air-fuel ratio when the amount of combustion is small. Device. 2. A differential pressure generating section is provided in the combustion air ventilation path, a gas nozzle is provided in the resistance pressure section of the differential pressure generating section, and the pressure of the high pressure section of the differential pressure generating section is conducted to the gas amount control device to control the gas amount. 2. The forced air supply/exhaust type combustion apparatus according to claim 1, wherein the outlet pressure of the control device is set lower than the pressure of the high pressure section of the differential pressure generating section. 3. The forced air supply/exhaust type combustion device according to claim 1, wherein the pressure difference between the outlet pressure of the gas amount control device and the air nozzle high pressure portion pressure is increased as the combustion amount increases.