JPS6410733B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a gas combustion control device configured to improve the stable combustion region according to the combustion characteristics of a burner.

Conventional structure and its problems Conventionally, as this type of gas combustion control device, the first
Pressure equalization valve method (or zero governor method) shown in the figure
is well known. That is, the air sent by the blower 1 passes through the air throttle 2 to the mixing unit 3, the gas passes through the pressure equalizing valve 4 and the air throttle 5 to the mixing unit 3, where the air and gas are mixed, and this mixed gas is passed through the diffuser 6. After the pressure is restored, it passes through the first pressure equalizing plate (not shown) in the burner 7 to the flame hole (not shown).
It blows out and burns. On the other hand, the secondary air that is branched from between the blower 1 and the air restrictor 2 passes through a fixed secondary air restrictor 8 (usually installed inside the burner 7) and then passes through the secondary air outlet of the burner 7 (not shown). gushing out from). The pressure upstream of the air throttle 2 is introduced into the back pressure chamber 9 of the pressure equalizing valve 4, and the pressure equalizing valve 4 automatically adjusts the pressure at the outlet of the pressure equalizing valve to be equal to the pressure in the back pressure chamber 9. Note that 10 is a diaphragm, and 11 is a valve that is directly connected to the center portion of the diaphragm 10 and is movable.

Here, if the pressure upstream of the air throttle 2 is P _A and the pressure upstream of the gas throttle 5 is P _G , then the air-fuel ratio, which is a mixture of gas and air, is set by the pressure equalizing valve so that P _A = P _G. If it can be controlled at 4, the value will remain almost constant even if the combustion amount is adjusted. However, in the pressure equalizing valve 4, a control error occurs that prevents P _A = P _G due to changes in the rigidity of the diaphragm, effective pressure receiving area, etc., and this becomes especially noticeable when the combustion amount is reduced.
1/ required for household combustion equipment such as gas water heaters
This made it difficult to achieve a combustion amount adjustment ratio of about 5 to 1/10. Furthermore, since the air restrictor 2 is a fixed restrictor, the primary air ratio is constant, and the restrictor that adjusts the amount of secondary air disposed inside the burner 7 is a fixed restrictor.
The second air restrictor 8 cannot be adjusted according to the combustion characteristics of the burner, so if the combustion amount is reduced depending on the type of gas, yellowing may occur or the burner may become unstable, resulting in stable combustion of the burner. The disadvantage was that the combustion range was narrow, and therefore the combustion adjustment range could not be widened.

Purpose of the Invention The present invention solves these conventional problems, and aims to increase the control ratio of the combustion amount and control the control ratio so that it remains almost constant even when the type of gas changes. .

Structure of the Invention The present invention includes a differential pressure sensor that detects a pressure difference between the upstream side of a variable gas throttle and the upstream side of a primary air throttle, and uses the output of this differential pressure sensor to control the gas amount adjusting means or the air amount adjusting means. A variable throttle mechanism configured to control either one or both of the above, and the amount of primary air and secondary air required for combustion are inserted into the variable gas restriction and the bypass passage. It is configured to be adjustable with a throttle and a variable secondary air throttle, and by improving the combustion characteristics of the burner, which differs depending on the gas type, the combustion amount adjustment range is expanded, and
This ensures that the combustion amount control ratio does not change even if the gas type changes.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 2 to 4.

1A is an air side passage that supplies combustion air, 1G
2 is a gas-side passageway for guiding gas, 2 is a gas amount adjusting means such as a gas pressure proportional control valve, and 3 is a variable gas throttle.

3a is the type of gas with the maximum flow rate (for example, city gas) when the rated input gas is flowing at a specified pressure.
A fixed gas restriction, i.e. a gas nozzle, defined by 3
b is an adjustment throttle that is necessary when changing gas type from city gas to propane gas, etc., which requires a small flow rate when flowing gas at the rated input, 4 is a blower that supplies the air necessary for combustion, and 5 is a blower. 4
6 is a primary air passage; 6 is a primary air passage; 7 is a bypass passage;
8 is a secondary air passage, 9 is a primary air throttle that determines the amount of primary air at the rated input flow rate, 10 is a variable throttle mechanism inserted through the bypass passage 7, and 11 is arranged in the secondary air passage 8. A variable secondary air restrictor 12 for controlling secondary air is a mixing section configured in the shape of a ventilate tube for mixing gas and air with low pressure loss. 13 is a differential pressure sensor that detects the pressure difference between the upstream pressure P _G of the variable gas throttle 3 and the upstream pressure P _A of the primary air throttle 9; and 14 is the output signal of the differential pressure sensor 13 that controls the gas amount adjusting means 2. A control circuit section 15 for driving is a burner.

In the above configuration, the variable gas throttle 3 and the variable throttle mechanism 10 are already connected to a predetermined gas type (for example, city gas).
It is assumed that the variable secondary air restrictor 11 and the variable secondary air restrictor 11 are appropriately set in accordance with the combustion characteristics of the burner 15, and good combustion is achieved. In such a state, if the load on the burner 15 is changed, for example to increase the amount of combustion, the air amount adjusting means 5 operates to increase the amount of air. Therefore, the differential pressure sensor 13 detects a difference based on the pressure difference between the upstream pressure P _A of the primary air restriction 9 and the upstream pressure P _G of the variable gas restriction 3 (i.e., ΔP = P _A - P _G > O). Pressure force is generated. Then, this differential pressure output signal is processed by the control circuit section 14 and the gas amount adjusting means 2
is controlled so that P _A = P _G by adjusting the amount of gas to increase. That is, variable gas throttle 3b
The pressure difference between the upstream side of the primary air restrictor 9 and the upstream side of the primary air restrictor 9 is controlled to be always zero. If there is no error in the differential pressure sensor 13 including the electric control system, the air-fuel ratio will always be maintained at a constant value even if the combustion amount is adjusted.

FIG. 4 is a diagram showing the air-fuel ratio characteristics in this case. In other words, the horizontal axis is the air amount Q _A and the vertical axis is the gas amount.
If we take Q _G , as long as the variable throttle mechanism 10 and the variable secondary air throttle 11 are constant, the ratio of the total air volume (combining the primary air volume and secondary air volume) to the gas volume will adjust the combustion volume. However, the change occurs along the straight line b (standard). In other words, the air-fuel ratio remains constant even if the combustion amount changes. Further, the relationship between the primary air amount and the gas amount in this case is a straight line b' (standard).

Note that straight lines a and c indicate the minimum total air volume.
q _tN and the characteristics when adjusted to the maximum p _tM , a′,
The straight line c′ corresponds to a and c, and the primary air amount is the minimum
These are the characteristics when adjusted to q _IN and maximum q _IM .

If the air-fuel ratio characteristic for a given gas (for example, city gas) is b, then when changing from city gas to a gas type such as propane gas that has a high calorific value and a low flow rate, , First, the adjusting aperture 3b is converted to a predetermined one. Next, in order to match the combustion characteristics of the burner 15 corresponding to the gas type,
The variable throttle mechanism 10 is adjusted to set a predetermined amount of primary air, and the variable secondary air throttle mechanism 11 is also adjusted.
The maximum rated gas volume can be increased by setting the
The ratio of primary air volume and total air volume to G _MAX is:
They can be set in any combination between q _IN and q _IM and between q _tN and p _tM , respectively.

For example, it is possible to maintain the gas amount total air amount characteristic at characteristic b and change the gas amount primary air amount characteristic to a characteristic between a' and c' in accordance with the gas type. It is possible to maintain the quantity characteristic at b' and vary the gas quantity and air quantity characteristic to a characteristic between a and c in accordance with the gas type.

Effects of the Invention As described above, the gas combustion control device of the present invention always maintains the upstream pressure of the variable gas restriction and the upstream pressure of the primary air restriction or the variable secondary air restriction equal even when the combustion amount is adjusted. The differential pressure sensor is configured to control one or both of the gas amount adjusting means and the air amount adjusting means, and
Depending on the combustion characteristics of the burner or the type of gas, variable gas throttle and variable throttle mechanism and variable
By adjusting the secondary air restriction so that the primary air amount and the total air amount can be arbitrarily varied, the following effects are achieved.

That is, 1. The accuracy of air-fuel ratio control in gas combustors, especially high-load burner combustion equipment, is improved, and the combustion amount can be controlled in a wider range than before.

2. The stable combustion range can be adjusted to expand according to the combustion characteristics of the burner, which vary depending on the type of gas.

3. Therefore, even if the gas type is changed, the combustion amount adjustment range can be kept constant.

4 Furthermore, the discharge pressure of the blower is almost constant, and the amount of primary air can be variably adjusted.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional gas combustion control device, Fig. 2 is a block diagram showing an embodiment of the gas combustion control device of the present invention, Fig. 3 is a flow path system diagram of the same device, and Fig. 4 is a block diagram showing an embodiment of the gas combustion control device of the present invention. FIG. 3 is an air-fuel ratio control characteristic diagram of the same device. 1A...Air side passage, 1G...Gas side passage, 2
...Gas amount adjustment means, 3...Variable gas throttle, 4...
...Blower, 5...Air amount adjustment means, 6...Primary air passage, 7...Bypass passage, 8...Secondary air passage, 9...Primary air throttle, 10...Variable throttle mechanism, 11... ...Variable secondary air throttle, 12...Mixing section, 13...Differential pressure sensor, 15...Burner.

Claims (1)

[Claims] 1. The gas side passage is provided with a gas amount adjusting means and a variable gas throttle, and the air side passage is provided with a blower for supplying combustion air and an air amount adjusting means, and the downstream of this blower is provided with a primary air It branches into a passage, a bypass passage, and a secondary air passage, and the primary air passage has a primary air restriction, and the primary air restriction and the variable gas restriction are combined downstream to mix gas and combustion air. A mixing section is arranged to guide the air to the burner, a variable throttle mechanism is inserted in the bypass passage to guide the air downstream of the mixing section, and a variable secondary air throttle is arranged in the secondary air passage. a pressure difference between the upstream pressure of the variable gas restrictor and the upstream pressure of the primary air restrictor to control at least one of the gas amount adjusting means and the air amount adjusting means; A gas combustion control device consisting of a pressure sensor. 2. Claim 1 in which a part of the primary air constriction and the mixing part are integrated and have a bench-like pipe shape.
Gas combustion control device as described in section.