JPS62237215A - Combustion control device - Google Patents

Abstract

PURPOSE:To increase the variable width (TDR) of a combustion amount, by a method wherein a distributing means for air for combustion is mounted on the primary air passage side for air-fuel premixture, and when a distribution ratio is varied in a stepped manner, a primary air amount is controlled so that it passes a point where a primary air ratio of air-fuel premixture is reduced to a value lower than a primary air ratio prevailing during maximum combustion. CONSTITUTION:Air for combustion fed from a fan 4 is divided into primary air and secondary air by means of passage resistance determined by a distributor 5 mounted on the primary air side. When throttle of a combustion amount is progressed, if primary air ratio is raised to a point (l), the distributor 5 is actuated to throttle a primary air amount in a stepped manner, and the primary air ratio is steppedly changed to a point (n) being lower than a point (m) being a value during maximum combustion and is raised to a point O during minimum combustion. When a combustion amount is increased, if a primary air ratio is lowered to a point n' being lower than a value being a point (m) during maximum combustion with the decrease in an air surplus factor, the distributor is actuated, a primary amount is opened steppedly, the primary air is steppedly raised to a point l' to a point (n) during maximum combustion. This constitution enables TDR to be widely increased in a condition that stable combustion is maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates primarily to household combustors, and particularly to a combustion control device for greatly varying the amount of combustion in a water heater.

Conventional Technology This type of combustion control method is shown in Fig. 4.
The distribution ratio of primary air and secondary air is determined by the resistance ratio of each passage in the combustor, and the sensor 1 detects the primary air ratio, and the controller 2 controls the fan damper 3' to maintain a predetermined value.
There is something to control f″.

(Japanese Utility Model Publication No. 61-13151) In this case, in order to control the primary air ratio within a predetermined range, the total air amount, that is, the excess air ratio is also changed at the same time. Therefore, when the combustion amount is reduced, the flame tends to adhere to the flame nozzle and generate red heat, and in order to completely prevent this, it is necessary to reduce the excess air ratio and the primary air ratio. However, when applied to water heaters, lowering the excess air ratio lowers the velocity of the exhaust gas ejected from the exhaust port, causing backflow during strong winds, and the thermal efficiency of the heat exchanger, which is designed at the maximum combustion point, is too high. The problem is that the water vapor inside condenses, producing acidic condensed water that corrodes the equipment.

In order to meet these restrictions, the conventional combustion amount variable range (hereinafter referred to as TD)
(referred to as R) could not be made very large.

Problems to be Solved by the Invention It is an object of the present invention to expand the TDR limit, which was limited by the conventional flame glow and dew condensation, and to provide a device with a simple structure.

Means for Solving Problems Therefore, the present invention includes a means for varying the fuel flow rate, a means for supplying combustion air, and a means for distributing the combustion air into primary air for premixing and secondary air for secondary combustion. It has a distribution means that can vary the distribution ratio in all steps, a means for varying the combustion flow rate, a means for supplying combustion air, and a means for controlling the combustion air distribution means, and the combustion air distribution means is premixed. When the distribution ratio is varied in steps, the primary air amount is fully controlled so that the primary air ratio of the premixture passes the point where it becomes less than the primary air ratio at maximum combustion. It is something. Also, when changing the distribution ratio in steps with the distribution means, what is the combustion amount? The operating point of the distributing means with respect to the amount of combustion is shifted between when the combustion amount is reduced and when the amount of combustion is increased to provide hysteresis characteristics.

Effect When the combustion amount is reduced using the above configuration, the excess air ratio will inevitably increase in water heaters, etc. to improve wind resistance and prevent condensation, and at the same time, the primary air ratio will also increase, causing red heat for the rest of the day. However, since the relationship between the combustion amount, excess air ratio, and primary air ratio is known in advance at the time of design, the distribution will start before the prescribed combustion amount is reached, the primary air ratio increases, and the primary air ratio approaches the red-hot region. By activating the means, it becomes possible to reduce the primary air ratio to a value smaller than that at maximum combustion. In this case, at the operating point, the combustion amount is sufficiently small and the flame length is small, and the excess air ratio is large, so secondary air is sufficiently supplied, so the primary air ratio is made smaller than the value at maximum combustion. In this case, incomplete combustion will not occur. Furthermore, since the operating point of the distributing means with respect to the combustion amount has a hysteresis characteristic, even if the combustion amount is set near the operating point, frequent operations of the distributing means will not occur.

EXAMPLE An example of the present invention will be described below with reference to FIGS. 1 to 3. In Fig. 1, 4 is a fan that supplies combustion air, 5 is a distributor installed on the primary air passage side that variably divides primary air and secondary air in a stepwise manner, and 6 is installed on the fuel supply path, and 6 is a fan that supplies combustion air. 7 is a controller that controls the fan 5, the distributor 5, and the proportional valve 6. The combustion system includes a burner 8 supplied with a premixed gas, an air chamber 9 supplied with secondary air, a combustion chamber 10 provided on the downstream side, and a heat exchanger 11.

In the queen configuration, the combustion air supplied by the fan 4 is divided into primary air and secondary air mainly by passage resistance determined by a distributor 5 provided on the primary air passage side. The primary air is mixed with fuel supplied through the proportional valve 6 to form a premixed mixture and supplied to the burner 8, and the secondary air is supplied to the air chamber 9. The premixture injected from the burner 8 into the combustion chamber 10 becomes a flame and forms on the burner 8, and is completely combusted by the secondary air injected into the combustion chamber 10 from the air chamber 9 and becomes high-temperature gas. The heat exchanger 11 is heated and discharged to the outside air.

The water heated while passing through the heat exchanger 11 is used for hot water supply and space heating.

Looking at the relationship between the amount of supplied air and the primary air ratio, as shown in FIG. 2, the excess air ratio and the primary air ratio are in a proportional relationship.

Therefore, as shown in FIG. 3(2), if the combustion amount is reduced and the excess air ratio is increased as a measure to prevent condensation, the primary air ratio increases and approaches the red-hot region. Conventionally, due to this limitation, the relationship between the combustion amount and the primary air ratio was changed from point m to point p as shown in Figure 3 (B), and the corresponding relationship between the excess air ratio and the combustion amount was a as shown in Figure 3 (2). It was possible to vary the combustion amount only from point to point d. In the present invention, the relationship between the combustion amount, excess static electricity ratio, and primary air ratio is fully understood in advance, and the third
When the combustion amount is throttled down as shown in Figure (B), when the primary air ratio reaches 6 points, the distributor 5 is activated and the air volume is throttled in all steps until the maximum combustion value is reached at point m. The value is changed stepwise to a lower value n point to reach the 0 point at the time of minimum combustion. In addition, when the combustion amount is increased, when the excess air ratio decreases and the primary air ratio reaches point n', which is lower than the maximum combustion value at point m, the distributor is activated to increase the primary air amount in steps. It is opened and raised stepwise to point e' on the primary air passage side, reaching point n at the time of maximum combustion. In this way, by operating the distributor 5, excessive changes and increases in the primary air ratio are suppressed, thereby preventing red hot flames, and by providing hysteresis characteristics to the operation of the distributor 5, the distributor 5 can be operated near the operating point. can prevent frequent activation. Furthermore, even if the primary air ratio is lower than the point m at maximum combustion due to the operation of the distributor 5, as shown in point n and point n', the excess air ratio in that case will be at point b and point n', respectively, as shown in Figure 3 (5). At point b', the value is sufficiently larger than that at point a, indicating that sufficient secondary air is being supplied and the amount of combustion is small, so that incomplete combustion does not occur.

While maintaining stable combustion, the TDR can be significantly increased compared to the conventional method.

Effects of the Invention As is clear from the following explanation, the following effects can be obtained according to the present invention.

(1) By limiting the amount of primary air with a distributor, it is possible to suppress an excessive rise in the primary air ratio, so when the combustion amount is reduced, the excess air ratio can be set to a large value, increasing the margin against dew condensation, and Backflow of exhaust gas can be prevented.

(2) Even if the combustion amount is reduced and the excess air ratio is set to a large value, is it still possible to use a distributor? Excessive rise in air ratio following sea by limiting? T because it can suppress and prevent red hot flame.
DRt can be greatly expanded and usability improved.

(j Since the distributor is installed on the primary air passage side, it does not directly control the air volume, which reduces control variation, and because it controls a small amount of primary air volume, the power consumption of the distributor is also small and compact. becomes possible.

(φ By providing a hysteresis characteristic to the operating point of the distributor with respect to the amount of combustion, it is possible to prevent frequent operation near the operating point.
This improves the durability of the distributor and enables stable control.

(5) The distributor may be any device that changes the amount of primary air in a stepwise manner, and can be manufactured at a very low cost.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of a combustion control device showing an embodiment of the present invention, Fig. 2 is a characteristic diagram showing the relationship between the primary air ratio and excess air ratio, and Fig. 3 (4) shows the air FIG. 3(B) is a comparative characteristic diagram showing changes in excess ratio, FIG. 3(B) is a comparative characteristic diagram showing changes in primary air ratio with respect to combustion amount, and FIG. 4 is a configuration diagram of a conventional example. 4...Fan, 5...Distributor, 6...
...Proportional valve, 7...Controller. Name of agent: Patent attorney Toshio Nakao and 1 other person 4-
7 Anne Fig. 2 Air II Mupan Fig. 3 (A)

Claims (2)

[Claims] (1) A means for varying the fuel flow rate, a means for supplying combustion air, and distributing the combustion air into primary air for premixture and secondary air for secondary combustion, and adjusting the distribution ratio in steps. a variable distribution means; a means for varying the fuel flow rate;
It has a means for supplying the combustion air and a means for controlling the combustion air distribution means, and the combustion air distribution means is provided on the side of the primary air passage for premixture, and the distribution ratio is adjusted in steps. A combustion control device that controls the amount of primary air so that it passes through a point where the primary air ratio of the premixture becomes less than or equal to the primary air ratio at maximum combustion. (2) When varying the distribution ratio in steps with the distribution means,
2. The combustion control device according to claim 1, wherein the operating point of the distributing means with respect to the combustion amount is shifted between when the combustion amount is reduced and when the combustion amount is increased, thereby providing a hysteresis characteristic.