JP3094808B2 - Combustion control method for 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 control method applied to various combustion apparatuses such as a boiler and an industrial furnace, and more particularly, to a combustion apparatus suitable for a combustion apparatus having an exhaust gas recirculation treatment facility. The present invention relates to a combustion control method.

[0002]

When burning a fuel in a combustion apparatus such BACKGROUND ART boiler, nitrogen oxides (NO _X) is generated. Nitrogen oxides, fail NO _X generated from the nitrogen component in the fuel, or nitrogen contained in the combustion air is divided into a thermal NO _X generated by being high-temperature oxidation. Since these nitrogen oxides are substances that cause air pollution, acid rain and the like, strict regulations are imposed on the concentration of nitrogen oxides contained in the exhaust gas.

[0003] Therefore, various methods for suppressing the production of nitrogen oxides have been proposed and put into practical use in order to suppress the production of nitrogen oxides accompanying combustion. In order to control the failure NO _X , it is effective to preliminarily denitrify the nitrogen component contained in the fuel. At present, it has not been reached.

On the other hand, as a method for suppressing the thermal NO _X, change the combustion conditions, it is known that combustion control such as changing a combustion method is effective, the exhaust gas recirculation into one of the modified technique of the combustion process There is removal.

[0005] The exhaust gas recirculation method, by mixing the exhaust gas to the combustion air supplied to the combustion chamber, which suppresses combustion control method the generation of thermal NO _X. In general, it is known that lowering the combustion temperature and lowering the oxygen concentration are effective in suppressing the generation of thermal NO _X. However, in actual combustion, when the oxygen concentration is reduced, the combustion temperature approaches the stoichiometric combustion, so that the combustion temperature becomes high, and it can be said that the combustion conditions are mutually contradictory.

However, in the exhaust gas recirculation method, the temperature of the exhaust gas supplied to the combustion chamber together with the combustion air is usually 200.
℃ ~ 300 ℃, compared with the combustion temperature is low,
The heat generated in the combustion chamber at the time of combustion can be absorbed, and the temperature rise in the combustion chamber due to the combustion can be suppressed. Further, since the exhaust gas is a complete combustion gas containing N ₂ , CO ₂ , H ₂ O, etc. as a main component, it does not burn even if it is supplied to the combustion chamber again, and the heat of reaction (heat generation) accompanying the combustion does not occur. Also does not occur.
Furthermore, since the combustion air contains exhaust gas containing almost no oxygen components, the oxygen concentration of the combustion air supplied to the combustion chamber is reduced compared to combustion air that does not use the exhaust gas recirculation method. Is done.

Hereinafter, a conventional combustion control method will be described with reference to FIG. 16 showing a schematic configuration of a combustion apparatus B4 having a configuration for applying the exhaust gas recirculation method. The fuel for combustion is supplied to the burner 80 from a fuel tank (not shown), and the fuel for combustion is atomized from the burner 80 into the combustion chamber 81. On the other hand, the combustion air is passed through a combustion air duct 83 by a combustion air fan 82 and a wind box 84.
And is supplied into the combustion chamber 81 from behind the burner 80. At this time, a part of the exhaust gas discharged from the combustion chamber into the chimney through the exhaust duct 85 is mixed into the combustion air supplied into the combustion chamber 81.

That is, a branch exhaust duct 86 is formed in the exhaust duct 85.
Are connected to an exhaust gas circulation fan 87. Therefore, a part of the exhaust gas is sucked to the branch exhaust duct 86 side. Since the exhaust gas circulation fan 87 and the combustion air duct 83 are connected by the circulation exhaust duct 88, the exhaust gas sucked into the branch exhaust duct 86 is supplied to the upstream side of the combustion air duct 83. is there.

The circulation exhaust duct 88 is provided with an exhaust gas recirculation amount adjustment damper 89 for adjusting the exhaust gas recirculation amount (mixing amount). The opening is fixed to a predetermined value by feedforward control based on experience values.

Therefore, the ratio of the exhaust gas mixed into the combustion air is constant, and feedback control for adjusting the opening of the exhaust gas recirculation amount adjusting damper 89 in consideration of the combustion state in the combustion chamber 81 is performed. Absent.

[0011] Here will be described with reference to the graph shown in FIG. 15 the relationship of the NO _X concentration in the exhaust gas recirculation rate and the exhaust gas. This graph shows that the maximum combustion amount is 28.5M
In a J / h A-fuel oil boiler, the combustion amount is 1.8 MJ
/ H shows the measurement results, and the vertical axis shows O ₂ 4%
The converted NO _X concentration is shown, and the horizontal axis shows the exhaust gas recirculation rate.

The exhaust gas recirculation rate and the O ₂ 4% -converted NO _X concentration are determined by increasing the O ₂ 4% -converted NO _X
Concentration is inversely proportional to decreases, it can be seen that it is sufficient high exhaust gas recirculation rate to reduce the NO _X concentration. However, increasing the exhaust gas recirculation rate means that the oxygen concentration in the supplied combustion air decreases, and when the oxygen concentration decreases extremely,
Flame blows out, and poor combustion such as lift and vibration combustion occurs.

Therefore, when the opening of the exhaust gas recirculation amount adjusting damper 89 is feedforward controlled as described above, the exhaust gas recirculation amount of about 20 to 30% is considered in consideration of a change in combustion conditions due to disturbance or the like. Depending on the circulation rate, a combustion control method using an exhaust gas recirculation method has been implemented.

The exhaust gas recirculation rate is the amount of combustion air.
[Nm^Three/ H] [Nm^Three/ H]
And is obtained by the following equation: Exhaust gas recirculation rate = Exhaust gas recirculation amount / Combustion air amount_Two4% conversion NO_XThe concentration [ppm]
Measurement NO with variation_XStandardize concentration [ppm]
This is an indicator used to facilitate comparison
In the following equation,_Two= 4
Conversion NO obtained _XConcentration. Where the fuel is liquid
In that case, O_Two4% conversion NO_XConcentration is NO_XConcentration and
If the fuel is gaseous, O_Two0% conversion N
O_XConcentration or O_Two6% conversion NO_XConcentration is converted N
O_XUsed as concentration. Conversion NO_X= (21-O_Two) / (21-exhaust gas
O_Two) × Measurement NO_X

[0015]

However, in the conventional combustion control method using the exhaust gas recirculation method, which determines the exhaust gas recirculation rate by feedforward control, the optimum exhaust gas recirculation rate for the actual combustion state is determined. As a result, there was a problem that generation of nitrogen oxides could not be suppressed to the maximum.

That is, in the case of the feedforward control, since the actual combustion state is not detected, for example, a change in the absolute volume of the combustion air due to a change in the outside air temperature, a change in the ventilation amount from the exhaust duct 85 to the chimney. The fluctuation of the exhaust gas recirculation rate due to the above must be considered.

Therefore, it is necessary to take a safety margin when determining the exhaust gas recirculation rate, and the exhaust gas recirculation rate tends to be set lower. Under such an exhaust gas recirculation rate, a sufficient reduction of nitrogen oxides cannot be expected even when other combustion control methods such as a two-stage combustion method are combined.

As described above, in the exhaust gas recirculation method, which is extremely effective as a method for suppressing nitrogen oxides, the exhaust gas recirculation rate cannot be increased to the limit because the combustion chamber 81
This is because it was not possible to directly detect the combustion state in the inside.

Here, although not a control device for a continuous combustion type combustion device, an EGR control device for an internal combustion engine that directly controls the opening and closing of an EGR valve by directly detecting a combustion state in the internal combustion engine is disclosed in Japanese Patent Laid-Open No. 2-298657. No. 6,086,045.

In this control device, a tip of an optical fiber is provided in a combustion chamber, and combustion light in the combustion chamber is guided to a photoelectric conversion element using the optical fiber as a transmission medium, and is converted into an electric signal. It has. Therefore, if this concept is applied to a combustion apparatus, it is possible to directly detect the combustion state, and it seems that the exhaust gas recirculation method can be effectively used.

However, the combustion mechanism is different between a single combustion type internal combustion engine in which combustion is interrupted each time combustion (explosion) occurs and a continuous combustion type combustion apparatus in which combustion is not interrupted. Can not be converted. That is, the control device described in the publication does not include a means for detecting and analyzing the turbulent state of the combustion flame, so that even if it is possible to simply detect the luminous intensity due to the explosion, it is not possible to change the combustion condition. Cannot detect the turbulent state of the combustion flame associated with the turbulence.

Further, the control device described in the publication merely executes ON / OFF control of the EGR valve with a certain light emission intensity as a boundary value, and does not aim at optimizing the exhaust gas recirculation rate. Things cannot be effectively suppressed. Further, there is no means for correcting disturbances such as radiant heat in the combustion furnace, and as a result, it can be applied only under an exhaust gas recirculation rate with a safety margin.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. By directly detecting a turbulent state (combustion state) of a combustion flame, an exhaust gas optimal for the detected turbulent state is provided. It is an object of the present invention to realize a recirculation rate and reduce the concentration of nitrogen oxides generated by fuel combustion. Also, when executing the optimal exhaust gas recirculation rate,
An object of the present invention is to provide a combustion control method for a combustion device in which carbon monoxide is not generated by incomplete combustion.

[0024]

[0025]

Means for Solving the Problems]請 combustion control method for Motomeko combustion apparatus according to one aspect of the present invention, an exhaust gas recirculation system for supplying a part of the discharged flue gas again the combustion chamber with combustion air from the combustion chamber A turbulence state detecting means for detecting a turbulent state of the combustion flame in the combustion chamber, and a turbulent state of the flame light from the turbulent state data detected by the turbulent state detecting means. A first step of extracting a light emission intensity representative component of the flame and a flame, a frequency analysis process of calculating an intensity integrated value in an entire frequency region with respect to the vibration component extracted in the first step , A second step of obtaining a first vibration power by performing in combination with an influence removing process for removing an influence of the component on the vibration component;
A first oscillation power obtained in the second step, comparing the pre-computed second vibrating power to achieve a predetermined turbulent state, thereby the first oscillation power coincides with the second vibration power Therefore, the third step of determining the amount of exhaust gas recirculation, and the third step of adjusting the exhaust gas recirculation amount adjusting valve based on the amount of exhaust gas recirculation determined in the third step to adjust the amount of exhaust gas mixed into the combustion air. And four processes as a configuration.

Here, in the second step , the influence removing process of dividing the vibration component by the light emission intensity representative component is performed, and the frequency analysis process is performed on the vibration component subjected to the influence removing process. Thus, the first vibration power may be obtained. In addition, the second step includes:
A process of obtaining the first vibration power by performing the frequency analysis process on the vibration component, and performing the influence removal process of dividing the vibration component subjected to the frequency analysis process by the emission intensity representative component. .

Preferably, the turbulence state detecting means is an optical sensor which converts the turbulence state of the flame light into an electric signal and outputs it as turbulence state data. Preferably, the ion current sensor converts the turbulent state of the flame light into an electric signal and outputs it as turbulent state data.

[0028]

[0029]

[Action] In the combustion control method of the combustion apparatus provided with the configuration described in 請 Motomeko 1, in a first step, detecting a turbulent state of the combustion flame in the combustion chamber due to the turbulent flow state detecting means, turbulent state detection A vibration component of the flame light and a representative component of the luminous intensity of the flame are extracted from the turbulence state data detected by the means. Here, when an optical sensor is used as the turbulent state detecting means, the turbulent state of the flame light is detected by the optical sensor, and the turbulent state is replaced with a current corresponding to the turbulent state and output. If an ion current sensor is used as the turbulence state detecting means, the turbulence state of the flame light is detected by the ion current sensor, and a current corresponding to the turbulence state is output.

In the following second step , of the components extracted in the first step, a frequency analysis process for calculating an integrated value of the intensity in the entire frequency range for the vibration component, The first vibration power is obtained by performing a combination with an effect removing process for removing the effect on the vibration.

Next, in the third step, comparing the pre-computed second vibrating power to achieve a first oscillation power and predetermined turbulent obtained in the second step, the first vibrating power Is determined to be equal to the second vibration power.

In the fourth step , the exhaust gas recirculation amount adjusting valve is adjusted based on the exhaust gas recirculation amount determined in the third step to determine the amount of exhaust gas to be mixed into the combustion air.

[0033] Here extraction, the combustion control method of the combustion apparatus provided with the configuration described in claim 2, in the second step, first, the effect removal processing for dividing the vibration component in the emission intensity representative components in the first step The first vibration power is obtained by performing the frequency analysis process on the vibration component subjected to the effect removal process on the subjected vibration component.

According to a third aspect of the present invention, in the combustion control method for a combustion apparatus having the configuration described above, in the second step , first, the vibration component extracted in the first step is subjected to a frequency analysis process, and the frequency analysis is performed. The first vibration power is obtained by performing an influence removing process of dividing the processed vibration component by the emission intensity representative component.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Several embodiments in which the present invention is applied to a boiler for supplying steam to a heating device in a factory will be described below with reference to the drawings.

First, the configuration of a boiler B1 to which the combustion control method for a combustion device according to the first embodiment is applied will be described with reference to FIGS. The boiler B1 includes a main body 10 including a combustion chamber 11, an exhaust gas duct 12 for guiding exhaust gas in the combustion chamber 11 to a chimney (not shown), and a combustion air supply duct 13 for supplying combustion air into the combustion chamber 11. An exhaust gas recirculation duct 14 for recirculating a part of the exhaust gas to the combustion air supply duct 13, and a fuel supply unit 20 for supplying fuel into the combustion chamber 11.

The main body 10 is formed in a horizontally long, substantially cylindrical shape, and has a combustion chamber 11 in which a mixture of fuel and combustion air is burned, and a liquid such as water which functions as a heat medium. A liquid chamber 15 for heating by the flame F is provided. Further, the combustion chamber 11 and the liquid chamber 15 are defined by AA in FIG.
As shown in the line sectional view, it is partitioned by the furnace wall 16.

A burner 17 for spraying and burning the air-fuel mixture into the combustion chamber 11 is attached to a right side wall of the combustion chamber 11, and an exhaust gas duct 12 is connected to a left side wall.

The burner 17 has a fuel supply section 20 and a fuel supply pipe 2 for supplying fuel to the burner 17.
1 and a combustion air supply duct 13 for supplying combustion air to a burner 17 are connected. Therefore, an air-fuel mixture in which the fuel and the combustion air are mixed is generated, and when the air-fuel mixture is ignited, continuous combustion of the air-fuel mixture occurs, and a combustion flame F is generated.

A viewing window 18 is formed on the left side surface of the combustion chamber 11, and a sensor amplifier 30 is connected to the viewing window 18 via an optical fiber OF for detecting a turbulent state of the combustion flame F. It is connected.

The liquid chamber 15 is filled with a liquid L such as water, which functions as a heat medium, with a small space S left above. Heat is transferred to the liquid L in the liquid chamber 15 via the furnace wall 16. As shown in FIG. 2, a plurality of smoke tubes 19 are disposed in the liquid chamber 15, and exhaust gas generated by combustion in the combustion chamber 11 passes through the smoke tube 19, passes through the exhaust gas duct 12, and passes through a chimney. From the exhaust gas to the atmosphere, the heat of the exhaust gas is also transferred to the liquid L in the liquid chamber 15.
Is transmitted to

As a result, the liquid L is heated to become a vapor, and the space S in the liquid chamber 15 is filled with the vapor.
Since a steam pipe (not shown) is connected to the space S in the liquid chamber 15, the steam filling the space S passes through the steam pipe and passes through each heating device (not shown).
To increase the room temperature in the factory, for example. Note that a liquid L having a large specific heat, such as water, is placed on the furnace wall 16.
, The temperature of the furnace wall 16 rises only up to about 200 to 300 ° C. Further, a pressure sensor PS is provided in the space S in the liquid chamber 15, and the fluctuation of the vapor pressure in the liquid chamber 15 is detected.

The fuel supply unit 20 includes a fuel tank 22, a fuel pump 23 for feeding the fuel in the fuel tank 22 to the burner 17, and a fuel tank 22 and the fuel pump 23.
A fuel supply pipe 21 connected to the burner 17 and a fuel flow control valve 24 for controlling the flow of fuel supplied to the burner 17 are provided.
The fuel flow control valve 24 is connected to a first control motor 26 for adjusting the opening through a link mechanism 25a.

The first control motor 26 is a motor capable of rotating the drive shaft by an angle corresponding to an input signal, and is used even when the steam generated in the liquid chamber 15 is consumed by the heating device. Is controlled according to the pressure fluctuation detected by the pressure sensor PS so as to keep the vapor pressure in the liquid chamber 15 constant. In addition, the fuel flow control valve 24
Between the fuel pump 23 and the fuel pump 23, a fuel flow meter 27 for detecting a fuel flow rate is provided.

The combustion air supply duct 13 draws in the outside air and supplies the combustion air to the burner 17.
And a combustion air amount adjustment damper AD for adjusting the amount of combustion air supplied to the burner 17. The combustion air amount adjusting damper AD is connected to the first control motor 26 via a link mechanism 25b, and is controlled in conjunction with the fuel flow rate adjusting valve 24 in this manner to always maintain a constant air-fuel ratio. Has been realized.

The exhaust gas recirculation duct 14 is disposed so as to connect the exhaust gas duct 12 and the combustion air supply duct 13 on the upstream side of the combustion air amount adjusting damper AD. An exhaust gas recirculation amount adjustment damper RD for adjusting the circulation amount is provided. The exhaust gas recirculation amount adjustment damper RD is connected to the second control motor 40 via a link mechanism 41, and is driven and controlled by a control method described later so as to realize an optimum exhaust gas recirculation rate.

Next, the circuit configuration of the input circuit such as the pressure sensor PS disposed in the boiler B1 and the output circuit such as the first and second control motors 26 and 40 will be described. A pressure sensor PS is connected to an input side of the pressure regulator 45, and a first control motor 26 is connected to an output side of the pressure regulator 45. The pressure regulator 45 takes in pressure data in the liquid chamber 15 detected by the pressure sensor PS and outputs a drive signal to the first control motor 26 so that the pressure in the liquid chamber 15 is kept constant. The opening of the fuel flow control valve 24 is adjusted. As a result, the pressure in the liquid chamber 15 is always maintained at a predetermined value, and stable supply of steam to the heating device is realized.

A sensor amplifier 30 and a fuel flow meter 27 are connected to the input side of the combustion control device 50, and the second control motor 40 is connected to the output side of the combustion control device 50.
Is connected. The combustion control device 50 fetches an analog signal from the sensor amplifier 30 and a fuel flow signal from the fuel flow meter 27, and executes a frequency analysis process, an exhaust gas recirculation amount determination process, and the like, which will be described later, to execute the second control motor 40. Control the opening degree. As a result, the exhaust gas recirculation rate optimal for the current turbulent state of the combustion flame F is realized, and NO
_X generation is suppressed.

The combustion control device 50 includes a control panel 46.
Are connected, and signals are exchanged between the two. For example, when any trouble occurs in the boiler B1, a command signal for forcibly stopping the operation of the boiler B1 is output from the combustion control device 50 to the control panel 46.

Next, the configuration of the sensor amplifier 30 will be described in detail with reference to the block circuit diagram shown in FIG. The sensor amplifier 30 includes an optical sensor 31, a current / voltage converter 3
2. It includes a DC / AC converter 33, an integrator 34, an analog divider 35, and an amplifier 36. The optical fiber OF is connected to the input side of the optical sensor 31, the current / voltage converter 32 is connected to the output side, and the DC / AC converter 33 is connected to the output side of the current / voltage converter 32. And an integrator 34 are connected. DC / AC converter 3
3 and an output of the integrator 34, an analog divider 35
Is connected to the output side of the analog divider 35.
6 is connected to the output side of the amplifier 36.
0 is connected.

The optical sensor 31 is an infrared detecting element that detects the disturbance of the combustion flame F light, converts it into a current signal, and outputs it. For example, a germanium photodiode or a phototransistor is suitable.

Next, the processing executed in the sensor amplifier 30 will be described with reference to FIG. First, combustion chamber 1
The turbulence state (flickering of light) of the combustion flame F in the inside 1 is detected by the optical sensor 31 via the viewing window 18 and the optical fiber OF.
And the turbulent state is converted into a current signal.
The amplitude of the vibration component (turbulence of the combustion flame F) included in the current signal obtained at this time changes in proportion to the change of the emission intensity component of the combustion flame F.

That is, when the emission intensity component of the combustion flame F is large, the amplitude of the vibration component becomes apparently large,
When the emission intensity component is small, the amplitude of the vibration component is apparently small. As a result, an actual vibration component cannot be obtained accurately. Therefore, the vibration component is smoothed by the extraction process and the division process described below.

The current / voltage converter 32 converts the current signal output from the optical sensor 31 into a voltage signal as shown in FIG. The waveform of this voltage signal oscillates with the passage of time around a predetermined DC voltage. In this voltage signal waveform, the average value of the DC voltage represents the light emission intensity component, and the vibration component is the flicker (turbulence) of the combustion flame F.
Is represented.

The DC / AC converter 33 removes the emission intensity component from the voltage signal waveform of FIG. 5A and converts only the vibration component into an AC voltage signal. As a result, as shown in FIG. 5B, only the vibration component is extracted from the current signal output from the optical sensor 31. On the other hand, the integrator 34 shown in FIG.
Of the voltage signal waveform to smooth the vibration component in the voltage signal waveform and calculate the average light emission intensity component. Here, the time constant of the integrator 34 can be set arbitrarily, and is adjusted as necessary. In this embodiment, the light emission intensity component itself is used as a light emission intensity representative component, and is used for the subsequent arithmetic processing.

Here, the output signal from the current / voltage converter 32 is integrated and smoothed by the integrator 34 in the analog divider 35 in the subsequent stage, for example, the output signal from the DC / AC converter 33. If (vibration component) is divided by the output signal from the current / voltage converter 32 instead of the output signal from the integrator 34, the following problem occurs.

That is, the signal (vibration component) output from the DC / AC converter 33 changes with time, and the signal output from the current / voltage converter 32 also changes with time. Therefore, if the output signal from the DC / AC converter 33 is divided by the output signal from the current / voltage converter 32, there is no problem in the division in the low frequency range, but the output waveform is distorted by the division in the high frequency range,
This is because a large error occurs.

The analog divider 35 divides the output signal (oscillation component) from the DC / AC converter 33 by the output signal (emission intensity component) from the integrator 34 to remove the influence of the emission intensity component. Output a signal. This electric signal is constituted only by a component caused by the disturbance of the combustion flame F. As a result, an actual vibration component can be accurately obtained.

Therefore, as shown in FIG. 6, after the current / voltage conversion, two types of waveforms a and b different from each other are obtained, and even if the emission intensity components are different, the influence of the disturbance of the combustion flame F is obtained. Are the same, an electric signal having substantially the same waveform can be obtained by performing the above-described extraction processing and division processing.

That is, in the case of the waveform a having a large amplitude, since the voltage of the average value (light emission intensity component) increases, the amplitude of the first electric signal obtained as a result of the division processing decreases. On the other hand, in the case of the waveform b having a small amplitude, the voltage of the average value (light emission intensity component) becomes low, and thus the amplitude of the second electric signal obtained as a result of the division process is as small as that of the first electric signal. Become. As described above, in the present embodiment, the amplitude fluctuation of the vibration component due to the influence of the light emission intensity component is removed by dividing the vibration component by the light emission intensity component.

The electric signal thus obtained is composed of a low-frequency component signal having a predetermined amplitude and a high-frequency component signal contained in the signal and having a smaller amplitude than the low-frequency component signal. Have been.

Then, the amplifier 36 amplifies the amplitude of the electric signal after the division processing to a predetermined level, and outputs the electric signal to the combustion control device 50. Next, the contents of processing executed in the combustion control device 50 will be described with reference to FIG.

In the combustion control device 50, the first vibration power of the combustion flame F is calculated based on the analog signal output from the sensor amplifier 30, and the first vibration power which is optimal for the fuel flow rate detected by the fuel flow meter 27 is calculated. The opening degree of the exhaust gas recirculation amount adjustment damper RD is adjusted so as to be adapted to the two vibration powers.

First, the A / D converter 51 converts an analog input signal from the sensor amplifier 30 into a digital signal. After the A / D conversion, the DSP 52 (digital signal processor)
FFT (fast Fourier transform) processing is performed on the digital signal.

In this embodiment, an A / D converter 51 having a 12-bit resolution is used.
In addition, the upper limit of the measurement frequency range at the time of the FFT processing can be set up to 500 Hz.

Here, the FFT processing will be described with reference to FIG. FIG. 7 is a graph showing the relationship between the power spectrum intensity obtained by the FFT processing and the measurement frequency. The vertical axis shows the power spectrum intensity (dB), and the horizontal axis shows the frequency (Hz). Represents a power spectrum at an exhaust gas recirculation rate of 1.00, represents a power spectrum at an exhaust gas recirculation rate of 1.10, and represents a power spectrum at an exhaust gas recirculation rate of 1.15.

The FFT processing is an arithmetic processing for obtaining the intensity of each frequency component in the digital signal.
The frequency waveform of the digital signal is analyzed by the T processing, so that the intensity waveform (power spectrum) of each frequency component is obtained.
Is obtained. The waveform area of the power spectrum represents the turbulence state and brightness of the combustion flame F. As described above, since a strong correlation is established between the waveform area of the power spectrum and the turbulent state of the combustion flame F,
By determining the waveform area of the power spectrum, the turbulent state can be quantified.

For the above reason, in the present embodiment, the FFT processing unit 53 integrates the intensity waveform of each frequency component in all frequency regions, and calculates the waveform area of the power spectrum, that is,
The first vibration power is determined.

By the division process in the sensor amplifier 30, the influence of the light emission intensity component on the amplitude of the vibration component is excluded from the electric signal used for calculating the first vibration power. Therefore, the first vibration power exhibits a primary characteristic with respect to the exhaust gas recirculation rate without being affected by the emission intensity component.

This situation will be described with reference to FIGS. 8 and 9. FIG. 8 is a graph showing the relationship between the change rate of the first vibration power and the exhaust gas recirculation rate. The vertical axis indicates the change rate of the first vibration power, and the horizontal axis indicates the exhaust gas recirculation rate. . The change rate of the first vibration power is an index indicating the degree of change of the first vibration power at another exhaust gas recirculation rate based on the first vibration power when the exhaust gas recirculation rate is 1.00. is there.

FIG. 9 is a graph for explaining the general relationship between the first vibration power and the exhaust gas recirculation rate. The vertical axis indicates the first vibration power and the horizontal axis indicates the exhaust gas recirculation rate. ing.

As can be seen from FIGS. 8 and 9, there is a negative correlation (primary characteristic) between the first vibration power and the rate of change of the first vibration power and the exhaust gas recirculation rate. This is supported by the fact that as the exhaust gas recirculation rate increases, the proportion of the oxygen concentration in the combustion air supplied to the burner 17 decreases, the flame becomes longer, and the turbulence of the combustion flame F decreases. Can be.

Here, thermal N generated during combustion is
O _X is can be suppressed by increasing the exhaust gas recirculation rate is as described above. However, if the exhaust gas recirculation rate is increased, incomplete combustion is caused due to a decrease in the oxygen concentration in the combustion air, and CO is generated.

That is, the region on the right side of the CO generation boundary point shown in FIG. 9 represents an incomplete combustion region in which CO is generated, and the obtained first vibration power is reduced under the set exhaust gas recirculation rate. In the case of such an incomplete combustion region, it is necessary to lower the exhaust gas recirculation rate.

More specifically, the turbulence state of the combustion flame F is directly detected by using the first vibration power, and is compared with the second vibration power measured in advance at the CO generation boundary point. As a result, it is possible to increase the exhaust gas recirculation rate to the limit, it is possible to effectively suppress the generation of NO _X.

Next, the first moving average processing unit 54
The first vibration power obtained by the processing unit 53 is averaged by the average number set in the first moving average number table 55. This process is a process for reducing the variation between data obtained by the FFT process. That is, there is variation in each data obtained by the FFT processing, and accurate control of the exhaust gas recirculation rate cannot be executed by using such variation data.

On the other hand, the second moving average processing section 56 averages the fuel flow rate signal detected by the fuel flow meter 27 by the average number set in the second moving average number table 57. Then, with reference to the broken line table 58, the second vibration power corresponding to the fuel flow rate subjected to the averaging process is read into the first adder 59.

As shown in FIG. 10, the broken line table 58 previously stores a second vibration power as a target value for the fuel flow rate. Here, FIG. 10 is a graph showing the relationship between the fuel flow rate stored in the polygonal line table 58 and the second vibration power, and the vertical axis represents the second vibration power.
The horizontal axis indicates the fuel flow rate. Note that the horizontal axis represents the fuel flow rate% where the minimum fuel flow rate is 0% and the maximum fuel flow rate is 100% as a scale.

Further, the broken line graph shown in FIG. 10 is obtained from the graph of FIG. 9 showing the relationship between the second vibration power and the exhaust gas recirculation rate at a certain fuel flow rate, for example, for every 10% fuel flow rate. It is a graph obtained by arranging the graph perpendicular to the paper surface.

Each point plotted in this graph is a boundary value of the second vibration power at which CO is generated at the fuel flow rate, and a region located below a broken line connecting the points indicates a region at which CO is generated. This is an incomplete combustion region. Therefore, the first signal obtained through the FFT processing unit 53
When the vibration power is applied to a region below the broken line, it is necessary to reduce the exhaust gas recirculation rate.

Therefore, the first adder 59 subtracts the first vibration power of the combustion flame F detected by the optical sensor 31 from the second vibration power corresponding to the fuel flow rate, and obtains a difference between the two. For example, in FIG.
If the vibration power is located below the broken line, the deviation takes a negative value, and if the vibration power is located above the broken line, the deviation takes a positive value.

Subsequently, the dead zone processing section 60 performs dead zone processing on the deviation signal obtained by the first adder 59. That is, a dead zone is set in the dead zone processing unit 60 in advance, and when the deviation fluctuates within the dead zone, the deviation signal is regarded as not fluctuating.
As a result, unnecessary control processing due to a measurement error caused by the optical sensor 31 or the like is suppressed, and proper operation of the boiler B1 is guaranteed.

The PID calculation unit 61 performs a PID calculation on the deviation signal subjected to the dead zone processing in the dead zone processing unit 60, and controls the second control motor 40 to eliminate the deviation between the first vibration power and the second vibration power. A drive signal for drive control is calculated and output to the second adder 62.

That is, as described above, by searching the graph shown in FIG.
An optimum exhaust gas recirculation rate is obtained for the obtained first vibration power, and the drive signal is calculated by performing an arithmetic process on the recirculation rate. Then, the output limiter 63 limits the signal that has passed through the second adder 62.

That is, in the output limiter 63, the upper limit value and the lower limit value of the signal intensity output to the second control motor 40 are set. Therefore, the second
When the signal passing through the adder 62 exceeds the upper limit value or falls below the lower limit value, processing for forcibly matching the upper limit value or the lower limit value is executed.

The drive signal processed by the output limiter 63 is output to the second control motor 40, and the opening of the exhaust gas recirculation amount adjustment damper RD is adjusted by driving the second control motor 40. Is done.

The measured data obtained by the combustion control method according to the present embodiment will be described with reference to FIGS. 11 and 12. FIG. Here, the amount of evaporation was 10 t / h in the test experimental device.
LSA heavy oil was used as the fuel. Further, a rotary cup type burner is used, and the maximum heat output is 28.5 MJ / h. The measurement was performed with the combustion amount fixed at 1.8 MK / h.

FIG. 11 shows NO _X generated in the combustion chamber.
4 is a graph showing the relationship between the O ₂ 4% converted NO _X concentration and the fuel flow rate, and the vertical axis represents the O ₂ 4% converted NO _X concentration (ppm).
And the horizontal axis shows the fuel flow rate (L / h). FIG. 12 is a graph showing the relationship between the CO concentration generated in the combustion chamber and the fuel flow rate. The vertical axis indicates the CO concentration (p
pm), and the horizontal axis shows the fuel flow rate (L / h).

In the graph, ○ indicates a measured value obtained by a conventional combustion control method using feedforward control in which the exhaust gas recirculation amount adjustment damper opening is fixed to about 34 degrees. In the graph, ● indicates a measured value obtained by the combustion control method by feedback control according to the present embodiment.

First, as can be seen from FIG. 11, according to the combustion control method of the present embodiment, the NO _X concentration is suppressed in the entire fuel flow region, and in particular, when the fuel flow is 1%.
In the range of 50 to 500 L / h, about 30% of N
The reduction in _OX concentration has been realized. In addition, as can be seen from FIG. 12, the CO concentration which is likely to be generated by increasing the exhaust gas recirculation rate is increased by only about 1 to 2% at the maximum, and the suppression of nitrogen oxides and the It can be said that the opposite goal of preventing complete combustion has been achieved. That is, the combustion flame to detect turbulence state of F to determine the optimum exhaust gas recirculation rate, by combustion control on the basis of the exhaust gas recirculation rate, while avoiding incomplete combustion, effectively NO _X It can be seen that the occurrence of the phenomenon can be suppressed.

In the combustion control device 50, in addition to the control described above, the correction combustion for the purpose of improving the followability to the change in the turbulence state of the combustion flame F and optimizing the exhaust gas recirculation rate at a partial load. Control is being performed.

The correction combustion control will be described with reference to FIG. The PV lower limit monitor 64 detects whether or not the average value of the first vibration power obtained by the first moving average processing section 54 is lower than a preset lower limit value. For example, when a value corresponding to −10% of the second vibration power with respect to the fuel flow rate at the time is set in the PV lower limit monitor 64 and the average value of the first vibration power is lower than the set value for some reason. Means that the PV lower limit monitor 64 detects the state.

Here, when the PV lower limit monitor 64 detects that the average value of the first vibration power has fallen below the set value, P
The V lower limit monitor ratio calculator 65 performs a predetermined ratio calculation. A predetermined ratio (for example, 10%) is preset in the PV lower limit monitor ratio calculation unit 65, and outputs the set ratio to the second adder 62 via the comparison selection unit 66.

Then, in the second adder 62, the set ratio is added to the output signal from the PID calculation unit 61, and the exhaust gas recirculation amount adjustment damper RD is forcibly closed. Such processing is performed when the average value of the first vibration power obtained by the first moving average processing unit 54 falls below the set value set by the PV lower limit monitor 64. This is because it can be determined that the amount of oxygen contained in the gas is absolutely insufficient.

Therefore, in order to avoid incomplete combustion, the exhaust gas recirculation amount adjustment damper RD is fully closed to prevent the exhaust gas from being mixed into the combustion air, and to increase the oxygen amount in the combustion air. It is necessary to try.

On the other hand, the change rate monitor 67 constantly detects the degree of change in the fuel flow rate. Specifically, a predetermined change rate (for example, 5%) is preset in the change rate monitor 67, and it is determined whether or not the fuel flow rate rapidly increases and the change rate is equal to or more than the predetermined change rate. Is detected.

When the change rate monitor 67 detects that the change rate of the fuel flow rate is equal to or more than the predetermined change rate, the fuel change rate monitor ratio calculation section 68 performs a ratio calculation. The fuel change rate monitor ratio calculating section 68 has a predetermined ratio (%).
Are set in advance, and the set ratio is output to the second adder 62 via the comparison / selection unit 66. Then, the second adder 6
In 2, the set ratio is added to the output signal from the PID calculation unit 61, and the exhaust gas recirculation amount adjustment damper RD is forcibly closed.

The reason why such a process is performed is that when the fuel flow rate is rapidly increased, it is necessary to feed combustion air containing an oxygen amount corresponding to the increased amount to the burner 17 to avoid incomplete combustion. For this reason, it is necessary to fully close the exhaust gas recirculation amount adjustment damper RD to increase the amount of oxygen in the combustion air.

That is, when the amount of oxygen in the combustion air is increased in accordance with an increase in the fuel flow rate, if the followability is poor, the required amount of oxygen cannot be obtained, resulting in incomplete combustion. Therefore, the rate of change of the average value of the output signal from the fuel flow meter 27 is
The change rate monitor 67 constantly monitors the fuel flow rate to determine the fuel flow rate.
The opening degree information is further added to the PID output signal and output.

The comparison / selection unit 66 includes a PV lower limit monitor ratio calculator 65 and a fuel change rate monitor ratio calculator 68.
This is a circuit for comparing and judging which signal is to be prioritized when both operate simultaneously. In the present embodiment, the comparison and selection unit 66 is set to select a signal having a large absolute value.

With the above-described correction, the situation where the amount of oxygen in the combustion air is insufficient is prevented beforehand, and when the fuel flow rate sharply increases, the amount of the combustion gas is increased according to the increase in the fuel flow rate. By increasing the amount of air, the combustion chamber 11
The incomplete combustion in is prevented beforehand.

Next, a combustion control method for a combustion apparatus according to a second embodiment will be described with reference to the drawings. First, a configuration of a boiler B2 to which a combustion control method for a combustion device according to a second embodiment is applied will be described with reference to FIG.

In the boiler B2 used in the second embodiment,
The boiler B1 used in the first embodiment is an optical sensor 3
1 is that the turbulent state of the combustion flame F is detected by the ion current probe 37, whereas the turbulent state of the combustion flame F is detected by the ion current probe 37. Since the other components are the same, the same reference numerals are used as in the first embodiment, and the description is omitted.

The ion current probe 37 is disposed on the wall surface in the longitudinal direction of the main body 10, and the tip of the probe 36 is disposed in the combustion flame F. The ion current probe 37 is a sensor that is grounded, detects a change in the current (flame ion current) flowing through the combustion flame F that is a conductor, and outputs the change to the sensor amplifier 30.

The value of the current flowing through the combustion flame F is
Change with the disturbance of the ion current probe 37
, The turbulence state of the combustion flame F can be detected in the same manner as when the flicker of the combustion flame F is detected by using the optical sensor 31.

Therefore, as obtained in the first embodiment, the sensor amplifier 3 does not respond to the flame ion current.
0, the exhaust gas recirculation rate can be controlled in accordance with the turbulent flow state by the first vibration power obtained by performing the arithmetic processing in the combustion control device 50. Therefore, it is possible to suppress thermal NO _X generated by combustion and to avoid a situation in which CO is generated due to incomplete combustion.

Next, a combustion control method for the combustion apparatus according to the third embodiment will be described with reference to FIG. The third
Since the configuration of the boiler (not shown) to which the combustion control method of the combustion device according to the embodiment is applied is the same as the configuration of the boiler B1 to which the combustion control method of the combustion device according to the first embodiment is applied, a description thereof will be given. Is omitted.

In the combustion control method for the combustion apparatus according to the first and second embodiments, the analog divider 35 in the sensor amplifier 30 is used.
After the division correction by, the corrected signal is digitally converted by an A / D converter 51 in the combustion control device 50. Then, the first vibration power is obtained through the frequency analysis of the digital signal by the FFT processing unit 53.

On the other hand, in the third embodiment, as shown in FIG.
The signal output from the optical sensor 31 is processed by executing after the D conversion and the FFT processing.

The sensor amplifier 30 includes a DC / AC converter 33 instead of the analog divider 35 in the first embodiment.
And a fourth amplifier 36b connected to the integrator 34.

On the other hand, the combustion control device 50 includes the third amplifier 3
A third A / D converter 51a corresponding to 6a and a fourth A / D converter 51b corresponding to the fourth amplifier 36b are provided. In addition, the combustion control device 50 controls the F
Instead of the FT processing unit 53 (see FIG. 1), an FFT / light quantity correction unit 70 surrounded by a broken line is provided. This FFT /
The light quantity correction unit 70 includes an FFT processing unit 71, a division division unit 7
2, an end determination unit 73 that determines the end of division and division, and a corrected first vibration power calculation unit 74.

The third amplifier 36a is connected to the DC / AC converter 3
Amplifies the vibration component output from the third amplifier 36, and a fourth amplifier 36b
Amplifies the emission intensity component output from the integrator 34. At this time, the amplification factor (gain) of the third amplifier 36a and the amplification factor of the fourth amplifier 36b are adjusted to completely match.

The vibration component amplified by the third amplifier 36a is digitized by the third A / D converter 51a, and the FFT processing unit 71 converts each frequency in the frequency analysis by the DSP 52 based on the digital signal. Compute the power spectrum of the corresponding signal. The division divide unit 72, the 4A / D converter 51b to the power spectrum value calculated in the FFT processing unit 71
Divided by the luminescence signal intensity signal digitized by

The end determination unit 73 determines whether or not the division unit 72 has performed the division process by the number of times (N) corresponding to the resolution of the FFT process. That is, FFT
The division process in the division unit 72 is repeated until all the power spectrum values calculated by the process are subjected to the respective division corrections. Then, finally, a corrected power spectrum corresponding to each frequency is calculated over all the measurement frequency regions subjected to the frequency analysis processing.

For example, when the measurement frequency range in the frequency analysis is 0 to 200 Hz and the resolution of the FFT is 200 lines, the division and division unit 72 and the end determination unit 73 correspond to each frequency at 1 Hz intervals by loop processing. 200 corrected power spectrum values are calculated.

The corrected first vibration power calculator 74 calculates the corrected first vibration power by summing all the obtained corrected power spectrum values. According to the previous example, the sum of the 200 corrected power spectrum values is
It is obtained as the first vibration power excluding the influence of the light emission intensity.

The first vibration power obtained in the third embodiment is equivalent to the first vibration power obtained in the first embodiment, and can be used as an index of the exhaust gas recirculation rate in the boiler.

As described above in detail with reference to some embodiments, according to the combustion method of the combustion apparatus according to the above embodiments, the turbulent state of the combustion flame F is directly detected by the optical sensor 31 and the ion current probe 37. The first vibration power is obtained by performing a division process and a frequency analysis process on the detected turbulence state data (electric signal). Then, the exhaust gas recirculation rate is determined so that the first vibration power matches the previously calculated second vibration power corresponding to the turbulent flow state, and the exhaust gas recirculation method is performed under the determined exhaust gas recirculation rate. Combustion control is being performed.

Therefore, the amount of exhaust gas contained in the combustion air can be increased to the limit, the combustion temperature can be reduced, and the oxygen concentration can be suppressed. As a result, the thermal NO _X concentration generated when burning the fuel can be significantly reduced. In addition, the second line in the linear table 58 used for determining the exhaust gas recirculation rate
The vibration is calculated from a CO generation boundary value that is an index of incomplete combustion. Therefore, even when the exhaust gas recirculation rate is increased to the limit, carbon monoxide is not generated due to incomplete combustion due to lack of oxygen concentration.

Further, the electric signal detected by the optical sensor 31 and the like is extracted into a vibration component and a light emission intensity component, and the analog divider 35 divides the vibration component by the light emission intensity component. Therefore, unlike the conventional combustion control method in which the emission intensity of the combustion flame F is simply detected,
The exhaust gas recirculation rate can be determined without considering the effect of the emission intensity component.

That is, the influence (disturbance) of the light emission intensity component can be excluded from the vibration component, and only the vibration component caused by the turbulent state of the combustion flame F can be extracted. As a result, the power spectrum shape of the combustion flame F is substantially the same regardless of the combustion state, so that it is possible to obtain highly accurate first vibration power without setting a high frequency at the time of frequency analysis.

Further, in the combustion control method according to the third embodiment, the ionic current probe 37 is used as the turbulence state detecting means. Therefore, unlike an infrared detecting element such as the optical sensor 31, the first vibration power and the exhaust gas recirculation rate can be temporarily related without being affected by the radiant heat in the combustion chamber 11. As a result, the turbulent state of the combustion flame F can be directly detected, and the exhaust gas recirculation rate can be determined more precisely.

The present invention has been described based on the embodiments. However, the present invention is not limited to the above embodiments, and various modifications and improvements can be made without departing from the spirit of the present invention. It is easily speculated.

For example, in this embodiment, the combustion control method is applied to a boiler for generating steam, but may be applied to an industrial furnace for heat treatment or the like. In such a case as well, it is desired to reduce nitrogen oxides. By applying the combustion control method of the combustion device according to the present embodiment, nitrogen oxides can be significantly reduced.

In general, since an industrial furnace is a combustion device for heat-treating a work, the combustion temperature in the combustion chamber is higher than the combustion temperature of the boiler, and a refractory material is attached to the furnace wall of the combustion chamber. And the refractory temperature reaches about 1000 ° C. Therefore, when detecting the turbulent state of the combustion flame F using the optical sensor 31 composed of an infrared element, the detection accuracy is deteriorated due to radiant heat from a refractory material or the like.

That is, when the influence of the radiation other than the combustion flame F is large, only the emission intensity component increases greatly and the amplitude of the vibration component hardly changes as compared with the case where there is no influence.

As a result, the signal processing is performed by dividing the vibration component by the light emission intensity component on the assumption that the change in the vibration component changes in proportion to the change in the light emission intensity component. The control method does not hold.

Therefore, it is necessary to correct the amplitude of the vibration component by a method that does not use the light emission intensity component and is not affected by radiant heat. This combustion control method is characterized in that, when the temperature of the combustion flame F itself rises, the vibration component also increases with the increase of the luminous intensity component, and when there is the influence of radiant heat from the refractory material or the work, the luminous intensity increases. This method takes into account that the component increases but the amplitude of the vibration component hardly changes.

Specifically, a value representing the amplitude of the vibration component which is not affected by radiant heat is taken, and the value is used as a substitute value (light emission intensity component) for the light emission intensity component. As a result, even in a combustion apparatus that is affected by radiant heat, the vibration component that changes with a change in the combustion state is reliably made constant, and the first vibration power that always corresponds to the exhaust gas recirculation ratio on a one-to-one basis is used. Obtainable.

A high-pass filter may be interposed between the analog divider 35 and the amplifier 36 in the sensor amplifier 30. That is, the amplifier 36 of the sensor amplifier 30
In the amplification of the electric signal in the above, the amplification factor is adjusted so that the maximum amplitude of the electric signal falls within the allowable input voltage with reference to a signal in a low frequency range having a large amplitude. Therefore, the electric signal in the high frequency band in the amplified electric signal has a relatively small amplitude as compared with the amplitude of the electric signal in the low frequency band, and is not recognized by the A / D converter 51 having a low resolution. is there.

Therefore, a low-frequency component signal in the electric signal is removed by a high-pass filter, and a primary characteristic is defined between the vibration power and the exhaust gas recirculation rate without using an expensive high-resolution A / D converter. You can have. As a result, the exhaust gas recirculation rate can be controlled by the first vibration power.

Furthermore, the optical sensor is not limited to a germanium photodiode or a phototransistor, but may be any element that can convert the light (flicker) of the combustion flame F into an electric signal. This is because if light can be converted into an electric signal, the combustion control method in each embodiment can be implemented.

Further, in the above embodiment, the combustion control method is applied to a boiler or a combustion furnace as a combustion device, but it is needless to say that the present invention is effective for other combustion devices.

Further, in addition to the representative amplitude value used in the third embodiment, the voltage value of the electric signal detected at regular intervals is extracted, and the square root of the squared value is used as the representative amplitude value. May be used. That is, any data obtained from the vibration component can be used as the representative amplitude value.

Further, in each of the above embodiments, the second vibration power is stored in advance in the linearity table 58. However, the provision of a carbon monoxide detection sensor and the like allows the combustion state (whether or not the combustion is incomplete) to be detected. Then, a more optimal exhaust gas recirculation rate may be determined from the detection data and the first vibration power.

In the case where such a configuration is provided, compared with the case of calculating the exhaust gas recirculation rate from the broken line table 58,
An exhaust gas recirculation rate closer to the limit can be achieved, and the generation of nitrogen oxides can be significantly suppressed.

Although not described in the claims, the technical ideas grasped from each of the above embodiments are described below.
The effect is described below. (1) In the combustion control method for a combustion device according to any one of claims 1 and 2 , the light emission intensity representative component is an electric power output from the optical sensor 31 or the ion current sensor. A combustion control method for a combustion apparatus, wherein the light emission intensity component is extracted separately from the vibration component from a signal.

In the case where such a structure is provided, in a combustion device such as a boiler having a relatively low furnace wall temperature, a primary characteristic can be provided between the turbulent state of the combustion flame F and the vibration power, and the vibration power can be increased. Can be used to control the exhaust gas recirculation rate. (2) In the combustion control method for a combustion device according to any one of claims 1 and 2 , the emission intensity representative component is an electric power output from the optical sensor 31 or the ion current sensor. A combustion control method for a combustion device, comprising a representative amplitude value extracted from an amplitude of the vibration component in a signal.

In the case where such a configuration is provided, the amplitude of the vibration component not affected by the radiant heat is used as the representative component of the light emission intensity. A primary characteristic can be given to the vibration power, and the exhaust gas recirculation rate can be controlled by the vibration power.

[0140]

[0141]

[0142]

Combustion control method for combustion apparatus according to the present invention is configured to detect directly the turbulent state of the combustion flame by turbulence state detecting means, the light emission intensity representative component and the vibration component from the detected turbulence state data Are extracted respectively. Further, a frequency analysis process and an influence exclusion process are performed on the extracted vibration component in combination to obtain a first vibration power,
The exhaust gas recirculation amount adjusting valve is adjusted so that the first vibration power matches the second vibration power prepared in advance.

Therefore, an optimum exhaust gas recirculation rate for the detected turbulent flow state can be realized. As a result, the combustion temperature decreases, and the amount of oxygen in the combustion air decreases, so that the concentration of nitrogen oxides generated with the combustion of the fuel can be reduced. In addition, when executing the optimum exhaust gas recirculation rate, it is possible to avoid generation of carbon monoxide due to incomplete combustion.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a combustion device to which a combustion control method for a combustion device according to a first embodiment is applied.

FIG. 2 is an enlarged sectional view of the combustion device shown in FIG. 1 taken along line AA in FIG.

FIG. 3 is a functional block diagram illustrating signal processing in a sensor amplifier in the combustion control method for the combustion device according to the first embodiment.

FIG. 4 is a functional block diagram illustrating signal processing in the combustion control device in the combustion control method for the combustion device according to the first embodiment.

FIGS. 5A to 5C are waveform diagrams for explaining the behavior of various electric signals processed in the sensor amplifier in the first embodiment.

FIG. 6 is a waveform chart showing a comparison between two types of electric signals obtained by processing in a sensor amplifier in the first embodiment.

FIG. 7 is a graph showing the relationship between power spectrum intensity and frequency for three types of exhaust gas recirculation rates.

FIG. 8 is a graph showing a general relationship between a power change rate and an exhaust gas recirculation rate.

FIG. 9 is a graph for explaining a correlation between a second vibration power and an exhaust gas recirculation rate.

FIG. 10 is a graph showing a relationship between a second vibration power and a fuel flow rate stored in a broken line table.

[11] The combustion control method for combustion device obtained as a result of the implementation of the first embodiment, is a graph showing the relationship between the O ₂ 4% in terms of NO _X concentration and the fuel flow rate.

FIG. 12 is a graph showing the relationship between the CO concentration and the fuel flow rate, obtained as a result of performing the combustion control method for the combustion device according to the first embodiment.

FIG. 13 is a schematic configuration diagram of a combustion device to which the combustion control method for the combustion device according to the first embodiment is applied.

FIG. 14 is a functional block diagram illustrating signal processing in a sensor amplifier and in a combustion control device in a combustion control method for a combustion device according to a third embodiment.

15 is a graph showing the relationship between the O ₂ 4 terms NO _X concentration and the exhaust gas recirculation rate.

FIG. 16 is a schematic configuration diagram of a combustion apparatus to which a combustion control method for a conventional combustion apparatus is applied.

[Explanation of symbols]

10: body, 11: combustion chamber, 12: exhaust gas duct, 13
... combustion air supply duct, 14 ... exhaust gas recirculation duct,
Reference numeral 15: liquid chamber, 16: furnace wall, 17: burner, 20: fuel supply unit, 30: sensor amplifier, 31: optical sensor, 32: current / voltage converter, 33: DC / AC converter, 34: integrator , 35 ... analog divider, 36 ... amplifier, 37 ... ion current probe, 50 ... combustion control device, 51 ... A / D converter, 52 ... DSP, 53 ... FFT processing unit, 54 ... first
Moving average processing unit, 55: first moving average number table, 5
6: second moving average processing unit, 57: second moving average number table, 58: broken line table, F: combustion flame, RD: exhaust gas recirculation amount adjustment damper, WF: blowing fan, OL ...

Continued on the front page (72) Inventor Toshiharu Tachibana 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Toshiyuki Otsubo 1 Toyota City Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) Reference Document JP-A-3-110320 (JP, A) JP-A-5-87333 (JP, A) JP-A-5-288343 (JP, A) JP-A-6-180117 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) F23N 5/00 F23N 5/08 F23N 5/12

Claims (5)

(57) [Claims] 1. A combustion control method for a combustion device having an exhaust gas recirculation system for re-supplying a part of exhaust gas discharged from a combustion chamber together with combustion air into the combustion chamber. detecting a turbulent state of the combustion flame, a first step of extracting a vibration component of the flame light and flame emission intensity representative component and respectively from the detected turbulence state data by the turbulence state detecting means, the first step For the vibration component extracted in the above, a frequency analysis process of calculating an intensity integrated value in all frequency regions and an effect removal process for removing an influence of the emission intensity representative component on the vibration component are combined. a second process of obtaining a first vibration power by applying a first oscillation power obtained in the second step, in advance in order to realize a predetermined turbulent Comparing the second vibration power is calculated, and a third step of determining an exhaust gas recirculation amount for the first oscillation power coincides with the second vibration power, exhaust gas recirculation is determined in the third step combustion control method for combustion equipment which adjusts the exhaust gas recirculation amount adjusting valve, characterized in that it is composed of a fourth step of adjusting the amount of exhaust gas to be mixed into the combustion air based on the amount. 2. The combustion control method for a combustion device according to claim 1 , wherein said second step performs said effect removing process of dividing said vibration component by said emission intensity representative component. A combustion control method for a combustion device, wherein the first vibration power is obtained by performing the frequency analysis processing on the vibration component that has been performed. 3. The combustion control method for a combustion device according to claim 1 , wherein in the second step , the frequency component is subjected to the frequency analysis process, and the frequency component subjected to the frequency analysis process is subjected to the light emission. A combustion control method for a combustion apparatus, wherein the first vibration power is obtained by performing the influence removing process of dividing by an intensity representative component. 4. A combustion control method for combustion apparatus according to any one of claims of claims 1 to 3, wherein the turbulent state detection means, converts the turbulent state of the flame light into an electrical signal A combustion sensor for outputting the turbulent state data as an optical sensor. 5. A combustion control method for combustion apparatus according to any one of claims of claims 1 to 3, wherein the turbulent state detection means, converts the turbulent state of the flame light into an electrical signal A combustion control method for a combustion apparatus, wherein the ion current sensor outputs the turbulent flow state data.