JP2973849B2 - Method for determining air volume switching in combustion device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion apparatus of the type in which the supply amount of combustion air is switched and adjusted stepwise according to the amount of combustion, and a method for determining whether or not this switching adjustment has been performed reliably. It is about.

[0002]

2. Description of the Related Art When adjusting the amount of combustion in a combustion apparatus, a fuel valve provided in each of a plurality of fuel supply passages is selectively opened and closed to adjust the flow rate of fuel in a stepwise manner. In addition, there is a type in which the blowing amount of the combustion air is adjusted stepwise so as to maintain the ratio of fuel to combustion air (air ratio) at a predetermined value. Adjustment of the supply amount of combustion air in such a combustion device can be performed by changing the opening degree of a damper provided in a blower duct or by controlling the number of rotations of a blower using an inverter or the like. In order to obtain stable combustion performance, the supply state of fuel or combustion air is monitored.

In the above-described combustion apparatus, the switching of the supply amount of combustion air is confirmed by detecting the position of the damper or detecting the air volume by an air volume detector using a pressure sensor. Is going. A pressure sensor using a semiconductor may be used as a detector for detecting such an air volume. A pressure sensor using this semiconductor generally has a characteristic in which a signal value changes in accordance with a change in ambient temperature (generally referred to as a temperature drift characteristic). If the ambient temperature rises due to the operation of the apparatus, a change in climate, or the like, this affects the pressure sensor and hinders accurate detection. Therefore, the reliability of the control of the apparatus and the determination of the abnormality is reduced.

For example, in a boiler room or the like in which a boiler is installed, the temperature change may be remarkable depending on the operating condition of the boiler. In the case of an inexpensive semiconductor type pressure sensor, the amount of temperature drift is large, so the signal value from the pressure sensor is large. However, the value greatly deviates from the actual value, and the deterioration of accuracy becomes more remarkable.
Therefore, in such a combustion apparatus, it is necessary to use a sensor having a good temperature drift characteristic in order to ensure the accuracy of control and abnormality detection, which has led to an increase in cost. That is, if the switching state of the supply amount of the combustion air is erroneously determined and the combustion is performed without supplying the combustion air corresponding to the supplied fuel amount, unburned substances such as soot and carbon monoxide remain, and the combustion noise is reduced. This causes problems such as an increase in fuel consumption, generation of vibration combustion, and a problem that fuel cannot be used effectively.

[0005]

In view of the above problems,
The present invention relates to a combustion device for switching and controlling a supply amount of combustion air in a stepwise manner in accordance with a combustion amount. It is intended to provide a switching determination method.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, in the combustion apparatus stepwise switching controlled according to the supply amount of combustion air to the combustion amount of combustion air the air amount detector for detecting the state of supply of the combustion air supply path is provided, put on before and after the switching of the supply amount of combustion air
The ratio of the detection signal value from the air amount detector with a predetermined value that,
Wherein a ratio of the detection signal value is to provide the air volume switching determination method in a combustion apparatus, wherein the switching of the supply amount of combustion air to be determined to have been normally performed when greater than a predetermined value.

[0007]

According to the present invention, when the combustion device (1) is instructed to change the amount of combustion in order to increase or decrease the amount of combustion, the amount of combustion air is changed according to the amount of combustion. The switching is adjusted step by step. Before and after switching of the supply amount of combustion air
The ratio of the detection signal value from the airflow detector (8) at
You. When the ratio of the detection signal values is larger than a predetermined value, it is determined that the switching of the supply amount of the combustion air has been normally performed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment in which the present invention is applied to a boiler combustion apparatus will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a specific embodiment of the present invention, and FIG. 2 is an explanatory diagram of a judgment procedure in the present invention. In the drawing, a combustion device (1) is mounted on an upper part of a boiler (2). This combustion device (1)
(3) and a wind box that is a supply path for combustion air
(4) is provided. A wind volume detector (8) is attached to the wind box (4), and this output is connected so as to be input to a determination circuit (9). This air flow detector (8)
As described above, the supply amount of the combustion air is detected as a wind pressure, and more specifically, the pressure of the combustion air flowing in the wind box (4) is detected.

The combustion device (1) according to the present invention is of a type in which the amount of combustion is adjusted stepwise, and in the embodiment shown in the drawing, it corresponds to a three-position control system. That is,
Since the amount of combustion is controlled in three stages: stop, low combustion, and high combustion, the fuel pipe (3) has two branch pipes.
(3a) and (3b) are provided, and fuel valves (5a) and (5b) are connected to each of the branch pipes (3a) and (3b). The fuel supply amount is adjusted stepwise by selectively opening and closing the fuel valves (5a) and (5b). A blower (6) is connected to the wind box (4) at the upstream end, and the amount of combustion air supplied from the blower (6) is adjusted stepwise according to the adjustment of the fuel supply amount. Is adjusted to still,
Adjustment of the supply amount of the combustion air is performed by a method of providing an air flow adjusting damper downstream of the blower (6), a method of controlling the rotation speed of the blower (6) by an inverter, or the like.

The adjustment of the fuel supply amount and the combustion air supply amount is performed by a combustion control device (7). In addition to the above-described control of the combustion amount, the combustion control device (7) controls the following. The following control is performed. That is, when the operation of the boiler (2) is started, the combustion control device (7) activates the blower (6) to perform scavenging of the furnace prior to actual combustion (prepurge). After the prepurge operation for a predetermined time, one of the fuel valves (5a) is opened to start supplying fuel. This fuel is ignited by an ignition device (not shown), and actual combustion is started. Thereafter, the adjustment of the combustion amount in accordance with the increase or decrease of the required load on the boiler (2) is as described above, but if the required load further decreases, the combustion device (1) is temporarily stopped and the standby state is set. Or when the operation of the boiler (2) is stopped after the operation for a desired time, the fuel valve (5
The fire was extinguished by closing fuel supply by closing a) and (5b), and then the blower (6) was operated as it was to scavenge the exhaust gas after combustion from the furnace (post-purge). After performing the post-purge operation for a predetermined time, the blower (6) is stopped.

According to the present invention, when the supply amount of the combustion air is switched stepwise in accordance with the combustion amount, the detection from the air volume detector (8) is performed before and after the switching of the supply amount of the combustion air. Since the ratio of the signal values is compared with a predetermined value, and it is determined whether or not the supply amount switching is normally performed based on the ratio of the detected signal values , the detection of the air volume detector (8) is performed. When a signal is input and this determination process is performed,
That is, a determination circuit that receives an air flow rate switching instruction signal from the combustion control device (7) in order to determine the timing of switching the air flow rate.
(9) is provided. In the determination circuit (9), a detection signal value from the air volume detector (8) before air volume switching and an instruction signal for air volume switching from the combustion control device (7) are issued, and the air volume after the switching is stable. The detected signal value from the air flow detector (8) at the time of the comparison is compared with the detected signal value , and the ratio of the large detected signal value to the small detected signal value is obtained. If the ratio is larger than a preset value, it is determined that the air volume has been properly switched. Conversely, detection before and after the air volume switching
If the ratio of the signal values is smaller than a preset value , it is determined that the air volume has not been properly switched due to a failure of the blower, the damper, or the like. The above-mentioned set values are set in consideration of the supply range of the combustion air corresponding to each combustion amount, an adjustment range for each combustion amount, an error in the adjustment, an error due to the aforementioned temperature drift amount, and the like. Thus, the same set value can be applied to various models while maintaining the same value.
In addition, since the wind pressure is proportional to the square of the supply amount per unit time, the determination is reliably performed. In addition, the air volume detector
Detection signals from (8) is outputted to the combustion controller via a decision circuit (9) (7), the determination result of the decision circuit (9), together with the detection signal of the air amount detector (8) Combustion control device
Output to (7). Then, based on the detection signal of the air volume detector (8) and the determination result of the determination circuit (9) , the combustion control device (7) stops the combustion device or notifies the occurrence of an abnormal situation.

The above determination procedure will be described with reference to FIG. This drawing shows the switching timing of the air volume and the change of the air volume. The vertical axis indicates the supply pressure of the combustion air based on the detection signal value of the air volume detector (8). In this figure,
This shows a state in which the combustion shifts to a high combustion after the low combustion for a predetermined time, and further maintains the high combustion for a predetermined time and then shifts to a low combustion. First, when switching from the low combustion state to the high combustion state, when switching from the low combustion state to the high combustion state, in addition to the fuel valve (5a), the remaining fuel valve (5b) is opened, and the blower ( 6) Increase the supply of combustion air by controlling itself or the damper. At this time, if the switching is performed normally, the pressure PL during low combustion
Changes to the high combustion pressure PH shown by the solid line in the figure. However, when the pressure after switching to the high combustion is lower than the normal value, for example, as shown by a dotted line in the drawing, the pressure does not substantially change due to the failure of the blower, its driving device, the damper, and the like. The ratio between PH 'and the pressure PL during low combustion becomes smaller. The ratio of the detected pressure at this time is compared with the set value described above, and if it is smaller than the set value, it is determined that the switching has not been properly performed.

Next, when switching from the high combustion state to the low combustion state, when switching from the high combustion state to the low combustion state, one fuel valve (5b) is closed and the remaining fuel valve (5b) is closed. Is open and the blower
(6) Reduce the supply of combustion air by controlling itself or the damper. At this time, if the switching is performed normally, the pressure PH at the time of high combustion changes to the pressure PL at the time of low combustion indicated by a solid line in the figure. However, when the pressure after switching to the high combustion is higher than the normal value, for example, as shown by a dotted line in the drawing, the pressure does not change if the pressure after switching to the high combustion is hardly changed due to the failure of the blower, the driving device thereof, the damper, and the like. PH
And the pressure PL 'at the time of low combustion becomes small. The ratio of the detected pressure at this time is compared with the set value as described above, and if it is smaller than the set value, it is determined that the switching has not been properly performed.

[0014] Thus, at all times, by the ratio of the detection signal value of air volume before and after switching the air <br/> amount detector (8) Thus by performing the determination of the air flow switch, temperature characteristics of air volume detector (8) Can be determined irrespective of the error caused by the air flow, and the error of the detection value due to the individual difference of each air volume detector (8) can be absorbed to make a reliable determination, and in general, the accuracy of control and abnormality detection can be extended. Can be maintained over. As described above, a temperature detector for temperature compensation is not required without using an expensive detector having good temperature drift characteristics and the like, and the control itself can be made simple. still,
Above example, application of the present invention, may be provided to adjust flow rate damper downstream of the blower (6), in that to adjust the supply amount of combustion air by controlling the rotational speed of the blower (6) Was described, but in recent years,
Adjustment of the supply amount of the combustion air is controlled by a damper only during a specific operation such as ignition, and is usually performed by controlling the rotation speed of a blower (6). It is needless to say that the present invention can be similarly applied. In the above embodiment, the air volume detector (8) is directly attached to the wind box (4), but in the boiler (2) as described above, the air volume detector (8) is compared. The air flow detector (8) and the wind box (4) are connected by a conduit to reduce the influence of temperature described above. The present invention can be similarly applied to such a mounting structure.

[0015]

As described above, according to the present invention, when the supply amount of the combustion air is switched in a stepwise manner in accordance with the combustion amount, the air flow detector is provided before and after the switching of the supply amount of the combustion air. Is compared with a predetermined value, and when the ratio of the detection signal values is larger than the predetermined value, it is determined that the switching has been normally performed. Since it can be accurately determined whether or not the control has been performed, control and abnormality detection can be performed with high accuracy. Moreover, the detection signal before and after switching of the combustion amount
Since the determination is made using the ratio of the values , the error of the air volume detector can be absorbed to perform the reliable detection.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a specific embodiment of the present invention.

FIG. 2 is an explanatory diagram of a procedure for determining the quality of air volume switching according to the present invention.

[Explanation of symbols]

 (1) Combustion device (4) Wind box (combustion air supply path) (8) Air flow detector (9) Judgment circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F23N 1/02 102 F23N 5/18 101

Claims (1)

(57) [Claims] 1. A combustion device (1) for adjusting stepwise switching in accordance with the combustion rate of the supply quantity of combustion air, the air volume for detecting the state of supply of combustion air to the supply path of the combustion air (4) Detector (8) is installed , and before and after switching the supply amount of combustion air .
Takes the ratio of the detection signal value from the airflow detector (8) is compared with a predetermined value, the detection ratio of the signal value normally switched supply amount of <br/> combustion air when greater than a predetermined value A method for determining air volume switching in a combustion device, comprising determining that the air flow has been performed.