JPH07198134A - Combustion control device - Google Patents

Abstract

PURPOSE:To assuredly detect either a large or small flame vibration, and suppress a vibration combustion conforming to the result of the detection, and further more, suppress noises effectively by applying a conventional electrode for flame detection, without newly providing a sensor. CONSTITUTION:A vibration judgement means 4 judges that a set first reference value is exceeded by respective detection outputs of a fuel flow rate detecting means 2 and air flow rate detecting means 3, the flow rate of air is increased. In the meantime, when it is judged that a second reference value is exceeded, the flow rate of a fuel is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control device that detects and suppresses combustion vibration that may occur during combustion.

[0002]

2. Description of the Related Art In a burner of a combustor, self-excited vibration of an air column, that is, combustion vibration may be caused by local heating of air. Cause damage. Therefore, conventionally, the occurrence of the above combustion vibration is regarded as a pressure vibration or a flame current vibration, and based on the detection of these vibrations, necessary measures for vibration suppression, for example, fuel supply is stopped. Are operating.

[0003]

However, in order to catch the flame vibration as the pressure vibration as described above, it is necessary to install a separate pressure sensor or the like, and when it is taken as the flame current vibration, it is small. Although the vibration can be detected, there is a problem that a large vibration cannot be recognized as a vibration because the flame current is disturbed.

Further, when the low-level vibration time is short and the vibration suddenly becomes large enough to cause noise, it is difficult to detect the frequency by the flame current.

The present invention has been made in order to solve the above-mentioned conventional problems. By not using a new sensor and using the conventional flame detecting electrodes, flame vibrations of either large or small size can be obtained. It is an object of the present invention to obtain a combustion control device capable of reliably detecting even the above, and effectively suppressing combustion vibration and noise according to the detection result.

[0006]

In the combustion control system according to the present invention, the vibration determining means exceeds the first reference value set based on the detection outputs of the fuel flow rate detecting means and the air flow rate detecting means. In this case, the flow rate of air is increased, and when the second reference value is exceeded, the flow rate of fuel is decreased.

[0007]

The combustion control device according to the present invention utilizes the fact that the magnitude of the combustion oscillation corresponds to the oscillation of the flame current, and the magnitude of the flame current is a predicted value obtained based on the air flow rate and the fuel flow rate. When a certain first reference value is exceeded, the air ratio in the combustor is changed so as to suppress small oscillating combustion, and when it exceeds a second reference value, noise is rapidly suppressed so that the fuel Make the supply controllable.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a flame current detecting means for detecting a flame current in a combustor by using a well-known electrode. One of the plus electrode and the minus electrode is, for example, a conventional flame detection frame rod, and the other is used as the electrode. It can be a burner of a combustor or a cooling pipe. In addition, a DC voltage or an AC voltage having a frequency different from that of the commercial power source is applied between these electrodes.

Further, 2 is a fuel flow rate detecting means for detecting a fuel supply amount to the combustor, 3 is an air flow rate detecting means for detecting an air supply amount, 4 is a vibration determining means such as a microcomputer, and each of the above detections is performed. Based on the output signals of the means 1 to 3, when the flame current exceeds the first reference value set based on the fuel flow rate and the air flow rate, it is determined that a small combustion oscillation occurs and the air flow rate is increased. On the other hand, when the second reference value is exceeded, it is determined that noise has occurred and the flow rate of fuel is reduced.

Reference numeral 5 is an air amount control means for receiving the output of the vibration determining means 4 and controlling the air ratio by valve control or the like, and 6 is a fuel amount control means for receiving the output and controlling the fuel supply amount. . As the fuel flow rate detecting means 2, a flow rate sensor or a flow rate control valve opening detection sensor is used. As the air flow rate detecting means 3, a flow rate sensor or a flow rate control valve opening detection sensor is used. For example, a rotation speed detection sensor of a supply blower is used.

Next, the operation will be described. First, during the combustion operation of the combustor, a flame current flows between the electrodes. Here, in the combustor, as described above, the resonance sound (vibration sound) is generated by the self-excited vibration of the air column,
It is understood that the frequency of this combustion oscillation is the same as the frequency of the flame current, and therefore the occurrence of combustion oscillation can be detected from the flame current.

Therefore, in the present invention, in order to detect such combustion oscillation, the output signal of the flame current detection means 1 is taken into the oscillation determination means 4 composed of a microcomputer or the like. Further, the vibration determination means 4 detects the occurrence of combustion vibration and noise based on the fuel flow rate signal from the fuel flow rate detection means 2 supplied to the combustor and the air flow rate signal from the air flow rate detection means 3. The first reference value and the second reference value set in advance are set and stored in a memory (not shown).

Therefore, the vibration judging means 4 first judges whether or not the magnitude of the flame current corresponding to the combustion vibration exceeds the first reference value, and if it exceeds, the air flow rate controlling means 5 is determined. A control signal is input to, and thereby the air ratio is changed in the direction of increasing the air flow rate. That is, the opening of the air flow rate adjusting valve or the like is increased. As a result, the combustion efficiency is gently reduced to suppress or stop the combustion vibration.

On the other hand, when the magnitude of the flame current exceeds the second reference value, the vibration determination means 4 inputs a control signal to the fuel flow rate control means 6 to reduce the fuel flow rate. In addition, the opening of the fuel flow rate control valve is reduced. As a result, combustion efficiency is rapidly suppressed, and noise is quickly suppressed.

By the way, when the combustion oscillation is most likely to occur, the combustion fluctuates drastically. In this case, the air-fuel ratio is about 1.2 or more as shown in FIG. 2 according to the experimental data. Has been confirmed. Therefore, when combustion oscillation occurs, it can be understood that the combustion oscillation can be suppressed by shifting the air-fuel ratio in either the left or right direction in FIG. 2 to change the combustion state.

In this case, it is practically preferable to shift the air flow rate so as to increase the required heat quantity, and the advantage of changing the air flow rate is that the combustion state can be controlled gently.

Therefore, by adjusting the air flow rate, vibration is first suppressed or stopped so that even if combustion vibration occurs during use of the water heater, the hot water temperature is not significantly changed,
The combustion vibration can be suppressed.

Further, in the present invention, the combustion vibration is suppressed by dividing it into two cases as described above. The reason is that, in order to change the air flow rate, normally, the rotational speed of the blower and the opening degree of the damper are used. Must be changed, and its response operation takes time. On the other hand, in order to change the fuel flow rate, it is only necessary to change the position of the moving coil, and current control can provide a response of 100 msec or less. This is to make it possible.

[0019]

As described above, according to the present invention, when the vibration determining means exceeds the first reference value set by each detection output of the fuel flow rate detecting means and the air flow rate detecting means, the Is increased, while the fuel flow rate is decreased when the second reference value is exceeded, a new sensor is not provided and the conventional flame detection electrode is used. There is an effect that it is possible to reliably detect both large and small flame vibrations, and to effectively suppress vibration combustion and noise according to the detection result.

[Brief description of drawings]

FIG. 1 is a block connection diagram showing a combustion control device according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a flame current and an air-fuel ratio considered in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flame current detection means 2 Fuel flow rate detection means 3 Air flow rate detection means 4 Vibration determination means

Claims (1)

[Claims] 1. A flame current detecting means for detecting a flame current flowing between a pair of electrodes by a flame of a combustor, a fuel flow rate detecting means for detecting a flow rate of fuel supplied to the combustor, and an air flow rate detecting means for detecting a flow rate of air, respectively. When the flow rate detection means and the flame current exceed a first reference value set based on the detection outputs of the fuel flow rate detection means and the air flow rate detection means, it is determined that a small combustion oscillation occurs, and A combustion control device comprising: a vibration determining unit that increases the flow rate, and when it exceeds a second reference value, determines that noise is generated and reduces the fuel flow rate.