JPS63273726A - Combustion monitoring method and its device - Google Patents

Abstract

PURPOSE:To detect a flameout and reduce a fuel leak accompanying the flameout by a method wherein a power spectrum is obtained by the frequency analysis of the signal from a semiconductor sensor and therefrom the energy area of a specified frequency zone is obtained and the area is compared with a preset energy area at the time of the flameout: when the former is smaller than the latter, a fixed output is delivered. CONSTITUTION:An optical power signals from an optical sensor 5 is fed and a power spectrum is obtained by carrying out the frequency analysis of this signal and the energy area of a frequency zone which is not affected considerably by the difference in combustion condition is obtained. Then, The difference (A) between the energy area at the time of a flameout and the present energy area is obtained. It is judged whether A is larger or smaller than 0: when smaller, a flameout signal for combustion is delivered as the flameout. A relay circuit 8 receives this output and delivers a signal for closing operation to a solenoid valve 4.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method and apparatus for monitoring combustion in gas burners, oil burners, etc.

BACKGROUND ART In order to detect the combustion state of a burner, it is necessary to distinguish between infrared radiation from the furnace wall and radiation from the flame, and to detect only the radiation from the flame.

Conventionally, such detection uses a photomultiplier tube that selectively detects ultraviolet light.

When the amount of ultraviolet rays detected by this photomultiplier tube is less than a predetermined value, it is determined that a misfire has occurred and an output is sent to an alarm device.

Furthermore, there is another technique that is capable of detecting the combustion state of a burner, as described in Japanese Patent Application No. 61-250986.

This uses a photodiode as an optical sensor to detect the optical power signal from the flame, compares the integral value obtained from the vibration part with the integral value of the optimal combustion state, and then adjusts the combustion air to eliminate the deviation. This is to adjust the flow rate.

Furthermore, there is a technique described in Japanese Patent Application No. 113686/1986 that can also detect a burner misfire condition.

This system detects the vibration width of the light intensity received by a semiconductor optical sensor, and if the vibration width is smaller than a predetermined value, it is assumed that a misfire has occurred and an alarm is issued.

Problems to be Solved by the Invention The above method using a photomultiplier tube has a problem with the sensor itself. In other words, a photomultiplier tube is a type of vacuum tube, and atmospheric pressure is constantly applied to the inside of the tube, so if the seal deteriorates due to vibration etc., gas components from the atmosphere will enter and the flame will be removed. If the light from the flame is no longer detected, or if the electrodes deteriorate due to long-term use, there is an inconvenience that a self-discharge phenomenon occurs in which discharge begins between the electrodes regardless of the presence or absence of light from the flame.

In particular, when a self-discharge phenomenon occurs, there is a problem in that fuel continues to be supplied even though the burner has misfired, assuming that it is burning.

Further, the method of Japanese Patent Application No. 61-250986 is for controlling the amount of combustion air, and is not immediately applicable as a means for dealing with misfires.

Further, although the device disclosed in Japanese Patent Application No. 61-313686 can detect a misfire condition, it is necessary to set the detection time to a certain length in order to reduce the error. Therefore, the amount of fuel leakage after a misfire increases accordingly.

Means for Solving the Problems In order to solve the above problems, the present invention processes a signal obtained from a semiconductor optical sensor to determine whether or not the light received by the semiconductor optical sensor is from a combustion flame. In a combustion monitoring method that outputs a constant output when it is determined that the flame is not from a combustion flame, the signal from the semiconductor optical sensor is frequency-analyzed to obtain a power spectrum, and then the energy area of a predetermined frequency band is determined from the power spectrum. is calculated, compared with a preset energy area at the time of misfire, and if it is smaller than that, a certain output is performed.

Although there are various types of optical sensors, the present invention uses photodiodes and phototransistors.

Use devices that use semiconductors such as solar cells, and do not use devices that use electrical resistance such as PbS sensors and PdS sensors.

That is, FIGS. 5 and 6 show the results of measurements of the light intensity of the gas burner flame in the furnace by the present inventors using an Sj photodiode and a CdS sensor, respectively.
As is clear from this, the Si photodiode exhibits a vibration pattern characteristic of a flame during burner combustion, but immediately after the burner is extinguished, the heat radiation from the furnace wall decreases rapidly, and furthermore, the vibration pattern characteristic of a combustion flame is It hasn't appeared.

On the other hand, in a CdS sensor, the electric resistance of the sensor decreases when it senses flame light, and the current value increases.In this sense, flame can be detected, but the vibrations due to flickering light are small and unclear.

Therefore, if a Si photodiode is used, the light from the combustion flame can be detected separately from the emitted light from the furnace wall depending on the presence or absence of the vibration. Also, by looking at the magnitude of the vibration width, it can be determined whether a combustion flame is being formed or not.

The present inventors have confirmed that similar detection can be performed not only with Si photodiodes but also with optical sensors using other semiconductors.

The power spectrum obtained by frequency analysis of the signal from the semiconductor optical sensor is as shown in FIG. 3. This shows the case where the air supply pressure is changed in three ways for a fixed amount of combustion.

These pressures are commonly used for combustion in burners.

As is clear from this figure, the frequency band above 50 Hz varies greatly depending on the combustion state. In other words, as the amount of combustion air increases, the frequency band of the vibration waveform expands toward higher frequencies.

Therefore, in order to determine the presence or absence of a combustion flame, it is desirable to use the energy area in a frequency band of, for example, 50 Hz or less, which is not affected much by differences in combustion conditions.

On the other hand, as shown in FIG. 4, the power spectrum at the time of misfire is not affected by the vibration of light from the flame, and the power spectrum becomes extremely small. However, the energy area in a predetermined frequency band obtained from the power spectrum of the flame immediately before a misfire can be determined through experiments or the like, and this can be used as the energy area at the time of a misfire.

The present invention also provides a combustion monitoring device for carrying out the above method, which includes a semiconductor optical sensor having a light receiving section installed opposite to the combustion flame, and a frequency for determining a power spectrum by frequency-analyzing the signal from the optical sensor. an analysis unit, a calculation unit that calculates the energy area of a predetermined frequency band of the power spectrum and outputs a constant output if it is smaller than a preset energy area at the time of misfire; and a calculation unit that supplies fuel based on the output from the calculation unit. The structure consists of a relay circuit that outputs an output to the solenoid valve in the pipe and causes it to close.

Semiconductor optical sensors are made of photodiodes, phototransistors, etc.

The frequency analysis section is a TF vibration analyzer that performs real-time analysis, FFT (Fast FourierT).
A transform type analyzer or the like can be used.

When a flame is formed in a burner or the like, an optical sensor made of a semiconductor receives light from the flame and emits a signal corresponding to the intensity of the light. This signal vibrates minutely in response to flickering flames.

The optical signal from the semiconductor optical sensor is then subjected to frequency analysis.

When the power spectrum is determined by frequency analysis,
Furthermore, the energy area of the predetermined frequency band is determined and compared with a preset energy area at the time of misfire.

As a result of the comparison, if the former is smaller than the latter, a constant output is performed.

This output is used, for example, to warn of the occurrence of a misfire, or to close a solenoid valve provided in the fuel supply pipe of the burner.

In the case of a combustion monitoring device, a signal is sent from a semiconductor optical sensor to a frequency analysis section. The frequency analysis section outputs a power spectrum, and the calculation section receives this and performs integration of a predetermined frequency band to calculate the energy area.

Further, the calculation section stores in advance the energy area corresponding to the misfire, and compares it with this.

If the comparison result is that the former is smaller than the latter, it is output to the relay circuit.

The relay circuit receives this and outputs an output to the solenoid valve of the fuel supply pipe, causing it to close.

This stops the supply of liquid or gaseous fuel to the burner.

Embodiment An embodiment of the present invention will be explained based on FIGS. 1 to 4.

In FIG. 1, numeral 1 is a combustor consisting of a burner,
A pipe 2 for supplying fuel such as gas or oil and a pipe 3 for supplying combustion air are connected to the combustor 1.

A solenoid valve 4 is provided in the fuel supply pipe 2 .

The solenoid valve 4 is opened and closed by a combustion monitoring device.

The combustion monitoring device includes a semiconductor optical sensor 5, a frequency analysis section 6, a calculation section 7, and a relay circuit 8.

The semiconductor optical sensor 5 is in this case a Si photodiode, the light receiving part of which faces the flame 9 formed by the combustor 1 .

The frequency analysis section 6 is made of an FFT type analyzer, and receives the signal from the optical sensor 5 and performs frequency analysis on the signal to obtain a power spectrum as shown in FIG.

The calculation section 7 and the frequency analysis section 6 form a flame recognizer 10 which is a computer.

The calculation section 7- manually inputs the power spectrum signal from the frequency analysis section 6, performs predetermined calculations, and outputs the result to the relay circuit 8.

The procedures performed in the flame recognizer 10 will be explained based on the flowchart of FIG.

First, in step 1, an optical power signal from the optical sensor 5 is input.

In step 2, the frequency analysis of the signal inputted in step 1 is performed to obtain a power vector.

In step 3, the energy area R of a frequency band that is not significantly affected by differences in combustion state in the power spectrum is determined. The frequency band is from 0 to 50 Hz in the example shown in FIG.

In step 4, the difference A=R between the energy area R8 at the time of misfire and the current energy area R in the frequency band of 0 to 50 Hz.
-R, is determined. R8 is the area shown in FIG. 4, which is stored in the computer in advance.

In step 5, determine whether A is greater or less than 0,
If it is less than 0, it is determined that a misfire has occurred and a combustion misfire signal is output in the next step 6.

Relay circuit 8 receives this output and outputs a closing operation signal to solenoid valve 4.

As a result, the supply of fuel to the combustor 1 is stopped.

Effects of the Invention Since the combustion monitoring method according to the present invention has the above-described configuration, a misfire can be detected without causing malfunction even if the optical power is detected in a shorter time than in the conventional method.

Therefore, fuel leakage due to misfire can be further reduced.

Furthermore, since the combustion monitoring device according to the present invention uses a semiconductor optical sensor to detect optical power, only the light receiving section is installed near the flame, the sensor section is installed inside the operation panel, and the light receiving section and the sensor section are connected to the light receiving section. It becomes possible to connect with fiber. Therefore, it is possible to prevent deterioration of the sensor section due to the effects of temperature, vibration, etc., and also to prevent malfunctions due to noise from the ignition plug or the like.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of an embodiment of the combustion monitoring device according to the present invention, Fig. 2 is a flowchart of the operating procedure performed by the flame detector of the device, and Fig. 3 is a system diagram of an embodiment of the combustion monitoring device according to the present invention. (A) shows the power spectrum obtained by
(B). (C) is a power spectrum diagram under different combustion air supply pressures, Figure 4 is a graph showing the power spectrum at the time of misfire together with R8, Figure 5 is a light intensity one-hour characteristic diagram of S1 photodiode, and Figure 6 The figure is a one-hour current characteristic diagram of a CdS sensor. 1: Combustor, 4: Valve, 5: Semiconductor optical sensor, 6: Frequency analysis section, 7. Arithmetic unit, 8: Relay circuit, 9: Flame, 10
:Flame detector. Utility model registration applicant Toyota Motor Corporation

Claims (1)

[Claims] 1. Processing a signal obtained from a semiconductor optical sensor to determine whether the light received by the semiconductor optical sensor is from a combustion flame, and when it is determined that the light is not from a combustion flame. In a combustion monitoring method that provides a constant output, the signal from the semiconductor optical sensor is frequency-analyzed to obtain a power spectrum, and then the energy area in a predetermined frequency band is determined from the power spectrum, and the energy area at the time of a preset misfire is determined. A combustion monitoring method characterized by performing a constant output if the output is smaller than that. 2. A semiconductor optical sensor with a light receiving section installed facing the combustion flame, a frequency analysis section that frequency-analyzes the signal from the optical sensor to obtain a power spectrum, and a frequency analysis section that calculates the energy area of a predetermined frequency band of the power spectrum. It consists of a calculation section that outputs a certain amount if it is smaller than the preset energy area at the time of misfire, and a relay circuit that receives the output from the calculation section and outputs it to the solenoid valve of the fuel supply pipe to close it. A combustion monitoring device characterized by: