JPS59202318A - Gas combustion controller - Google Patents

Abstract

PURPOSE:To increase the control ratio of a combustion amount and to maintain a constant control ratio even if the kind of gas is changed, by a method wherein a pressure on the upstream side of a gas throttle is normally equal to a pressure on the upstream side of a variable primary air throttle. CONSTITUTION:A differential pressure output, based on a pressure difference DELTAP=PA-PG>0 between a pressure PA on the upstream side of a variable primary air throttle 8 and a pressure PG on the upstream side of a gas throttle 3, is produced in a differential pressure sensor 11. The differential pressure signal is processed by an electric circuit part 12, and a gas amount regulating means 2 regulates a gas amount so that it is increased, and controls PA=PG, i.e., a pressure difference so that it is brought to zero. In case the kind of gas is changed, a variable primary air throttle 7 is regulated to a given value through replacement of a regulating throttle 3a, and further a variable secondary air throttle 10 is set to a given throttle. This permits increasing of the regulating ratio of a combustion amount, and besides, enables maintenance of the regulating ratio at an approximately constant value even if the kind of gas is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a gas combustion control device that is capable of improving combustibility according to the combustion characteristics of a burner. As a gas combustion control device, the pressure equalization valve method (or zero gas method) shown in FIG. Equalizing valve 4 and gas throttle 6
The air and gas enter the mixing section 3 through the dephasor 6, where the pressure is recovered by the dephasor 6, and then pass through the first pressure equalizing plate (not shown) in the nozzle 7 to the flame hole. (not shown) and burns. On the other hand, the secondary air branched from between the blower 1 and the air restrictor 2 is transferred to the fixed secondary air restrictor 8 (
2 of burner 7)
Air is ejected from the next air blowout hole (not shown). The pressure upstream of the air throttle 2 is led to 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 1o is a diaphragm, and 11 is a movable valve that is directly connected to the center portion of the diaphragm 10.

Here, if the pressure upstream of the air throttle 2 is Pi and the pressure upstream of the gas throttle 6 is fPc, then the air-fuel ratio, which is the mixture ratio of gas and air, is controlled by the pressure equalizing valve 4 so that PA=Pc. If possible, y will be a constant value even if the combustion amount is adjusted. However, in the pressure equalizing valve 4, a control error occurs that prevents PA:PG from changing due to changes in the rigidity of the diaphragm, effective pressure receiving area, etc., and this becomes noticeable especially when the combustion amount is reduced, and this is especially noticeable when the combustion rate is reduced. This makes it difficult to achieve a combustion amount adjustment ratio of about 115 to 1/1o, which is required for household combustion equipment. 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 the fixed secondary air restrictor 8. Because it cannot be adjusted according to the combustion characteristics of the burner, if the combustion amount is reduced depending on the type of gas, yellow color may occur or backlash may occur, narrowing the stable combustion range of the burner. The drawback was that the range could not be widened.

OBJECT OF THE INVENTION The present invention solves the above-mentioned conventional problems, and an object of the present invention is to widen the control ratio of the combustion amount and to suppress electricity so that the control ratio is kept almost constant even if the type of gas changes. It is something.

Structure of the Invention The present invention includes a differential pressure sensor that detects the pressure difference between the upstream side of a gas throttle and the upstream side of a variable 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. configured to control either one or both of the E+,
In addition, the amount of primary air and secondary air required for combustion can be varied.
It is configured to be adjustable with a secondary air restriction and a variable secondary air restriction, and by improving the combustion characteristics of the burner, the combustion amount adjustment range can be expanded, and the combustion amount adjustment ratio can be maintained even when the gas type changes. It was designed not to change.

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

1 is an air side passage that supplies combustion air, 1G is a gas side passage that guides combustion gas, and 2 is a gas amount adjusting means such as a gas pressure proportional control valve. 3 is the type of gas with the highest flow rate (city gas, etc.) when the rated input flows at the specified pressure.
32L is a gas throttle (i.e. gas nozzle) determined by 32L, which requires a small flow rate when flowing the rated input, and is necessary when changing gas types such as propane gas, 4 is a blower that supplies the air necessary for combustion, and 5 is a Air volume adjustment means such as dampers, 6 is a primary air passage, 7 is a secondary air passage, 8 is a variable primary air throttle that adds up the primary air volume at the rated input, 9 is a means for adjusting gas and air. This is a mixing section constructed in the shape of a Venturi tube for mixing with low pressure loss.

10 is a variable secondary air throttle for adjusting the amount of secondary air disposed in the secondary air passage 7; 11 is the pressure pc on the upstream side of the gas throttle 3 (or adjustment throttle Sa) and the variable primary air throttle 8
A differential pressure sensor 1 detects a differential pressure between the upstream pressure PA and the pressure PA on the upstream side of the
2 is an electric circuit section for driving the gas amount adjusting means 2 using the output signal of the differential pressure sensor.

13 is the total pipe resistance of the mixed gas system including the flame hole through which the mixed gas of gas and air flows, 14 is the total pipe resistance of the secondary air system including the secondary air nozzle, and 1 and 6 are the combustion burners. be.

In the above configuration, the gas throttle 3.
Variable primary air restriction8. It is assumed that the variable secondary air throttles 10 are set in accordance with the burner combustion characteristics of the combustion burner 16, and combustion is occurring. In such a state, if the load on the combustion burner 15 is changed, for example to increase the amount of combustion, the air amount adjusting means 6 operates to increase the amount of air. Therefore, the differential pressure sensor 11 detects the pressure difference between the upstream pressure Pi of the variable primary air throttle 8 and the upstream pressure PG of the gas throttle 3 (or adjustment throttle 31L) based on the pressure difference Δp=pmu−Pσ〉0. Output occurs. Then, this differential pressure output signal is processed by the electric circuit section 12, and the gas amount adjusting means 2 is adjusted so that the gas amount increases, and is controlled so that PA-=PG, that is, the pressure difference becomes zero. ○And if there is no error in the differential pressure sensor 11 including the electric control system, the air-fuel ratio will be maintained constant even if the combustion amount is adjusted.Figure 4 shows the air-fuel ratio characteristics in this case. FIG. In other words, if we take the air amount Qm on the horizontal axis and the gas amount Qe on the vertical axis, we get
As long as the variable primary air restrictor 8 and the variable secondary air restrictor 1o are constant, the ratio of the total air amount, which is the sum of the primary air amount and secondary air amount, and the gas amount is a straight line b' (standard). In other words, the air-fuel ratio remains constant even if the combustion amount changes. In addition, the relationship between the primary air amount and the gas amount in this case is b(
Standard) straight line.

Note that the straight lines a / and c / correspond to the characteristics when the total air volume is adjusted to the minimum qtN and maximum qtM, respectively, and the straight lines a and c correspond to a / and c /, and the primary air volume is This is the characteristic when adjusted to the minimum qjN and the maximum q1M.

Now, when the air-fuel ratio characteristic is b' when a predetermined gas is set (for example, city gas), if the gas type is a gas with a high calorific value and a low flow rate, such as propane gas, then First, replace the adjustment 3a diaphragm.

Next, in order to match the combustion characteristics of the combustion burner 15 corresponding to the gas type, the variable primary air throttle 8 is adjusted to a predetermined value, and the variable secondary air throttle 10 is further set to a predetermined value. , the primary air volume at the maximum rated gas volume GMAX,
The ratio of the total air amount can be set in any combination between qlN and qjM, and between qtN and qtM, respectively.

For example, by maintaining the gas amount-order air amount characteristic at the characteristic b, and changing the gas amount total air amount characteristic from a to C according to the gas type.
As described in the detailed description of the invention, the present invention is capable of varying the characteristics between 0 and 0.
A differential pressure sensor is used to adjust the upstream pressure of the variable primary air restrictor (or variable secondary air restrictor) to either the gas amount adjusting means or the air amount adjusting means so that it is always equal even when the combustion amount is adjusted. The structure is configured to control one or both, and the variable primary air restriction and the variable secondary air restriction can be adjusted in accordance with the combustion characteristics of the burner or the type of gas. , which has the following effects.

That is, (1) the stable combustion range can be adjusted to expand according to the combustion characteristics of the burner.

(2) The accuracy of air-fuel ratio control in gas combustion equipment, especially high-load burner combustion equipment, is improved, and the range of combustion amount adjustment can be made wider than before.

(3) Even when the gas type is changed, the combustion amount adjustment range can be kept constant.

[Brief explanation of drawings]

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, and FIG.
The figure shows the configuration of the device in terms of a pipe resistance system, and FIG. 4 shows the air-fuel ratio control characteristics of the device. 1m...Air side passage, 1G...Gas side passage, 2...Gas amount adjustment means, 3. River/gas throttle, 4...Blower , 6...Air amount adjustment means, 6...Primary air passage, 7...Secondary air passage, 8...Variable primary air restriction, 9... ...Mixing section, 1o...Variable secondary air throttle, 11...
・Differential pressure sensor, 16...Burner. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 4 ff Figure 2

Claims (1)

[Claims] (1) The gas side passage is provided with a gas amount adjustment means and a gas throttle, and the air side passage is provided with a blower that supplies combustion air and an air amount adjustment means, and the downstream of this air amount adjustment means is used as the primary air passage. The primary air passage is branched into a secondary air passage, and the primary air passage includes a variable primary air restriction, and a mixing part that joins the variable primary air restriction and the gas restriction downstream to mix gas and air. 6, and a variable secondary air throttle is arranged in the secondary air passage,
A differential pressure sensor is provided which outputs an electrical signal corresponding to the pressure difference between the upstream pressure of the gas throttle and the upstream pressure of the variable primary air throttle, and the variable primary air Z that changes the aperture and the variable secondary air aperture
Gas combustion control device configured. ? ) The gas combustion control device according to claim 1, wherein a part of the variable primary air throttle and the mixing part are integrated and have a venturi tube shape.