JPH03294721A - Combustion control method for burner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a combustion control method for a burner used in combustion equipment such as a boiler.

(Prior art) In a burner that burns liquid or gaseous fuel,
It is desirable to maintain the combustion state optimally during combustion.
Conventional technology for this purpose involves converting the light intensity signal generated by the burner flame into an electrical signal using a photo sensor made of a semiconductor such as a phototransistor, photodiode, or solar cell, and then analyzing the frequency of the vibration waveform. A method and control method for controlling combustion using the integrated value of the resulting power spectrum has been proposed (Japanese Patent Laid-Open No. 63-30
Note that as a method of detecting the power fg in a flame, there is also a method of detecting the ionic current using an electrode rod inserted into the flame, instead of using an optical sensor.

(Problem II to be Solved by the Invention) The technology described in the above publication was achieved by discovering that the air ratio and the ratio of the low frequency component to the high frequency component of the optical power spectrum have a constant relationship. This characteristic is used to control the air-fuel ratio. According to this method, the desired effect can be achieved when the low frequency component and high frequency component of the optical power spectrum are clearly distinguished, that is, when the specific frequency that distinguishes them is determined. Since the frequency had to be determined, the following problems arose.

■ Problems associated with determining a specific frequency When considering the power spectrum of combustion oscillations, it is necessary to consider that the power spectrum changes depending on the air ratio and the amount of combustion. When the air ratio is large, as shown in FIG. 6, there is a tendency for high frequency components to increase compared to FIG. 7, which shows when the air ratio is small.

On the other hand, when comparing the amount of combustion, Figure 8 shows the state where the amount of combustion is large, and Figure 9 shows the state when the amount of combustion decreases.
As can be seen from the comparison with the figure, when the combustion amount decreases,
The tendency is for the overall power level to decrease.

In these figures, the symbol a indicates the position of a specific frequency, and the specific frequency is used as a boundary to divide high frequency components and low frequency components, and the ratio thereof is calculated.

Examining FIGS. 8 and 9 now, it can be seen that as the amount of combustion decreases, the overall power level decreases. That is, there is almost no power spectrum in the portion indicated by the specific frequency a in FIG. 8, and therefore it is impossible to calculate the ratio between the low frequency component and the high frequency component. To solve this problem, when the combustion amount is minimum, a new specific frequency must be set as shown in Figure 9.
Calculations become complicated and the number of items to be set increases significantly.

■ Problems as a control index From what was stated in ■ above, in order to minimize the number of specific frequency settings, if the specific frequency is set on the low frequency side, the ratio between the high frequency side and the low frequency side will be lower than the high frequency component. Therefore, there is a problem in that the numerical value as a control index corresponding to the air ratio greatly varies.

■ Problems regarding the relationship with the combustion amount The index is the ratio of high-frequency components to low-frequency components, and this index is an empirical value that varies greatly depending on the specific frequency, so it is difficult to obtain a functional relationship between the combustion amount and the air ratio. The problem is that it cannot be done.

The present invention has been made in order to solve these problems of the above-mentioned application, and its purpose is to provide a burner combustion control method that eliminates and solves the problems of the above-mentioned application. do.

(Means for Solving the Problems) As a means for solving the above problems, the present invention detects an optical power signal from the flame of a burner, performs frequency analysis on the optical power signal to obtain a power spectrum, and detects an optical power signal in a burner flame. In a burner combustion control method that performs combustion control by knowing the combustion state from the power spectrum and controlling the air ratio so as to eliminate the deviation between the combustion state and the optimal combustion state stored in advance, the power spectrum is Detects the combustion state based on the overall integral value of all generated frequency bands,
The present invention provides a burner combustion control method characterized in that the detected combustion state is compared with a predetermined optimal combustion state and the air-fuel ratio is controlled so as to reduce the difference.

(Function) According to the method of the present invention having such a configuration, the sum total of the vibration energy spectrum caused by turbulent flame can be used as an index for air control.

(Example) Next, the method of the present invention will be explained together with a system system for realizing this method. FIG. 1 shows a system of a combustion apparatus for realizing the method of the present invention, and the symbol l is a furnace for heat-treating metal products and the like.

A burner 2 is attached to this furnace 1 to generate a flame 3. A fuel supply pipe 4 and a combustion air supply pipe 5 are connected to the burner 2 . The fuel supply pipe 4 is provided with a flow ffi control valve 6 and a flow meter 7, and the combustion air supply pipe 5 is provided with a %titi'iR control valve 8.
is provided. The opening degree of the fuel flow rate control valve 6 is controlled by a temperature controller 9. In other words, a thermometer lO is installed in the furnace 1, and the temperature controller 9 is controlled from this thermometer lO. The combustion amount (fuel flow rate) required to obtain the set temperature is calculated from the difference between the furnace temperature and the set temperature by obtaining the signal from the flow meter 7 and the signal from the flow meter 7, and outputs the calculated amount. This output is given to the fuel flow rate control valve 6 and the combustion air flow rate control valve 8. Therefore, if the temperature inside the furnace deviates from the set temperature, the amounts of fuel and combustion air are adjusted so as to return to the set temperature.

The flow rate of combustion air relative to the flow rate of fuel is determined by the temperature controller 9.
It is calculated based on the fuel flow rate, but the value is
It is undesirable for the combustion air flow 1ii to be directly applied to the control valve 8, e.g. the door of the furnace l (not shown).
When the burner 2 is opened and air enters the furnace 1, if the flow control valve 8 is directly controlled with the output calculated based on the fuel flow rate, the exhaust gas loss will increase, and if the burner 2 is abnormal, the fuel If the state of atomization deteriorates, if left untreated, a large amount of soot will be generated due to poor combustion. In order to eliminate such inconvenience, the output from the temperature controller 9 is corrected by the combustion air flow rate corrector II and then output to the flow tr+ control valve 8.

111 tons of combustion air! The corrector 11 together with the temperature regulator 9 constitutes a combustion air flow ffi regulator 12 . A correction output for the combustion air flow rate corrector 11 is produced by the following combustion control device. Let me explain this. As mentioned above, an optical sensor 13 made of a semiconductor such as a phototransistor, a photodiode, or a solar cell is installed at a position facing the flame 3 generated by the burner 2 of the furnace 1, and monitors the flame 3 and detects the flame. It is designed to emit an output signal corresponding to. A detector 14 is connected to the output side of the optical sensor 13, and is configured to shape the signal captured by the optical sensor 13 into a waveform. This detector 14
A frequency analyzer 16 is connected to the output side of the amplifier 15 via an amplifier 15. This frequency analyzer 16 performs frequency analysis of the output signal of the amplifier 15. The output side of the frequency analyzer 16 is connected to the input side of an optical power vibration controller 17. The above-mentioned air flow rate corrector 11 is connected to the output side of the .

The optical power vibration controller 17 detects the combustion state from the power spectrum signal output by the frequency analyzer 16,
This is compared with pre-stored optimal combustion state data, the air flow rate correction coefficient is calculated based on the deviation, and the signal is sent to the flow controller 12, which is then used to correct the deviation. Generate an output signal to obtain a fiil of combustion air and convert this output signal to fiii
There will be a light valve 8 in the m-section valve 8. Thereby, the flow 1m regulating valve 8 sends an appropriate amount of air to the burner 2 to control combustion.

When operating in this manner, the device disclosed in the above publication sets a specific frequency as described above, divides the specific frequency into a high frequency signal and a low frequency signal, and calculates the ratio of these two signals. However, in the method of the present invention, this is not done, and the sum of the vibration power spectrum is used as an index for air ratio control. This is because, in the method of the present invention, the total area of the vibration frequency spectrum of the turbulent combustion flame, that is, the total vibration frequency power, is correlated with the air ratio.

FIG. 2 shows a flowchart in this case.

That is, when a power spectrum signal is input in step 20, a power spectrum is obtained in the next step 21, and an integral value of the entire power spectrum is calculated in step 22.The flow rate correction coefficient is calculated from the deviation E obtained from this calculation. Calculate F. This calculated 8 is applied by the amount correction coefficient F! The iF1 moderator 12 is activated. Note that rFFTJ in step 21 in FIG. 2 refers to fast Fourier transform, which is calculation software for obtaining a vibration power spectrum from an input signal.

Figures 3 (a), (b), and (c) show actual measurement data measured using a furnace and smoke tube boiler. This data uses heavy oil and the combustion amount is 1704! /h
, 283g/h, and 3B21/h, and are plotted with the total power of the flame light vibration spectrum on the horizontal axis and the air ratio on the vertical axis. be. As is clear from this figure, a high correlation with a correlation coefficient of 0.78 or more is obtained on the exponential curve under all three conditions. By organizing this data, we found that the following formula holds true between the combustion amount, air ratio, and total vibration frequency power.

Now, the air ratio is λ, C is a function of combustion amount and is a unique constant, r
If (x) is a function with the combustion amount as a variable, and p is the total vibration frequency power, then λ=Ce4')P.

FIG. 4 shows the variation in measured values for each fuel amount. In this figure, the vertical axis shows the variation in set values, and the horizontal axis shows the combustion amount.

The bar graph represents the total power according to the present invention, and the line graph represents the power spectrum ratio.

As can be seen from this figure, the variation in the measured values based on the total power is smaller.

Comparing the power spectrum ratio according to the prior art as explained above and the total power of 1 according to the present invention, the present invention does not require setting of a specific frequency. This makes it possible to reduce the variation in measurement 1+1 and find the correlation between combustion amount and air ratio, which greatly reduces the number of measurement points required for setting various parameters. This makes it possible to simplify the effort required for parameter setting.

Figure 5 shows the Bacharach Small Scale 2, which shows the dust concentration.
The vertical axis is the total power and the horizontal axis is the combustion amount. This data also shows that there is an exponential relationship between combustion amount and total power when Bacharach Small is constant, and the number of measurement points needed to set the optimal air ratio can be significantly reduced. It turns out that it is possible.

(Effects of the Invention) As explained above, the present invention has discovered that a certain relationship holds true between the total power of the vibration spectrum of a company-style combustion flame, the air ratio, and the amount of combustion, and uses this relationship to control combustion. Since the above-mentioned result 2 can be obtained from actual measurement data, it is possible to prevent the generation of foreign smoke due to low air ratio combustion and improve safety.

Furthermore, since it utilizes the universal physical quantity of the vibration spectrum of turbulent flames, it can be widely used without being restricted by the type of fuel, such as gaseous fuel or liquid fuel. ■Means for measuring the vibrations of turbulent flames include bright flame emission intensity from the flame, OH radical emission intensity, local flow velocity fluctuations within the flame, ion current fluctuation spectrum, local combustion pressure fluctuations, local temperature fluctuations within the flame, combustion noise, etc. can be used.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a system used to implement the method of the present invention, FIG. 2 is a flowchart showing the control sequence of the method of the present invention, and FIGS. 3(a) and (b). (C) is a diagram of actual measured data of the present invention, Figure 4 is a graph comparing the characteristics of the method of the present invention and that of the prior art, Figure 5 is a graph showing Bacharach small scale, Figures 6 to 9 FIG. 2 is an explanatory diagram illustrating a state of change in a power spectrum. l - Furnace 2 - Burner 3 - Flame 6.8 - Flow ffi controller 11 - Air flow rate corrector 13 - Optical sensor 14 - Detector 16 - Frequency analyzer 17 - Optical power vibration controller Patent Applicant Toyota Motor Corporation Co., Ltd. Figure 1 JP 3-294721 (5) Figure 2 Figure 4

Claims (1)

[Claims] (1) Detect an optical power signal from the flame of the burner, perform frequency analysis on the optical power signal to obtain a power spectrum, determine the combustion state from the power spectrum, and determine the combustion state and the optimal combustion state stored in advance. In a burner combustion control method that performs combustion control by controlling the air ratio so as to eliminate deviations from the A burner combustion control method comprising comparing a combustion state with a predetermined optimal combustion state and controlling an air-fuel ratio to reduce the difference.