CN101769792A - Burning-flame detection method - Google Patents
Burning-flame detection method Download PDFInfo
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- CN101769792A CN101769792A CN200810204937A CN200810204937A CN101769792A CN 101769792 A CN101769792 A CN 101769792A CN 200810204937 A CN200810204937 A CN 200810204937A CN 200810204937 A CN200810204937 A CN 200810204937A CN 101769792 A CN101769792 A CN 101769792A
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Abstract
The invention provides a burning-flame detection method. The method comprises the steps of: firstly, collecting time-domain and frequency-domain signals for continuously sampling a burning flame in a finite time domain and a finite frequency domain at equal intervals and a corresponding burning-flame strength signal; and establishing a burning-flame detection system which comprises a signal acquisition module, a filter module, a power spectrum calculation module and a power spectrum analysis module. Interference signals, which are not required, among the collected signals are filtered by the filter module in the burning-flame detection system; a signal strength value of the corresponding frequency is calculated by the power spectrum calculation module; and the power spectrum analysis module performs comparison and analysis on a power spectrum to generate the power spectrum which is detected in real time, the burning state of the flame is analyzed according to the power spectrum, and the obtained result is real and extract.
Description
Technical field
The present invention relates to a kind of detection method of combustion flame, be specially adapted to the analysis of boiler internal combustion flame condition.
Background technology
The direct impression that boiler flame burns to the people is the power of brightness and the pulsation of flame root brightness.According to theoretical analysis and verification experimental verification, the flicker of flame or pulsation, its frequency and fuel type have much relations.Because the flame characteristic frequency difference during different types of fuel combustion, the intensity of the flame under every kind of frequency is also different, therefore accurately detects, the flame situation during the control fuel combustion is not easy very much.Especially in large-scale boiler, the flame situation during fuel combustion is complicated more.Yet during traditional flame detector observation flame combustion, mainly be after converting the light intensity signal of the combustion flame that receives to voltage signal by photoelectric commutator, carry out simply amplitude relatively after, just flame is had or not distinguishing of fire, and the analysis of combustion position.Such measurement, it has ignored the frequecy characteristic of different fuel flare up fire, also just is difficult to flame detection situation exactly, is easy to produce the wrong report phenomenon, influences the production safety of boiler.
Summary of the invention
The objective of the invention is to the combustion flame of different fuel in the boiler is detected.Provide spectrum curve, promptly provide the energy intensity distribution value of flame under difference burning frequency.According to this power spectrumanalysis contrast, obtain the accurate operating mode of combustion flame in real time.
To achieve the above object, the technical scheme taked of the present invention is:
A kind of detection method of combustion flame is provided, and its concrete steps are:
＜1〉at first adopt the combustion flame pick-up unit to gather the combustion flame signal, this signal be included in time-limited time domain and the frequency domain uniformly-spaced the time-domain signal of continuous sampling and frequency-region signal and with the corresponding flame intensity signal of frequency-region signal, and convert digital signal to;
＜2〉at the built-in burning fame detecting system of computing machine, in this detection system, set up signal acquisition module, filtration module, power spectrum computing module and power spectrumanalysis module;
＜3〉the flame combustion digital signal of above-mentioned collection is input in the burning fame detecting system in the aforementioned calculation machine, filter undesired signal by the filtration module in the burning fame detecting system, calculating by the power spectrum computing module obtains power spectrum, be analyzed by the power spectrumanalysis module, provide the power spectrum after the comparison;
＜4〉according to the above-mentioned power spectrum that provides, the situation of analytic combustion flame.
Above-mentioned the＜1〉in the step, described collection combustion flame signal adopts the combustion flame pick-up unit, the combustion flame pick-up unit to the simulating signal of combustion flame by the opto-electronic conversion in the pick-up unit, convert the light signal of flame to current signal, convert voltage signal through amplification treatment circuit in the pick-up unit to the current signal amplification and with current signal, by A/D converter the analog photoelectricity conversion of signals is become digital signal then.Regularly read digital signal and be kept at the collection of finishing in the data sequence signal.This digital signal be included in time-limited time domain and the frequency domain uniformly-spaced the time-domain signal of continuous sampling and frequency signal and with the corresponding flame intensity signal of time-domain signal;
The described burning fame detecting system of setting up in computing machine, wherein signal acquisition module is gathered the digital signal of above-mentioned input, will carry out Filtering Processing through filtration module then.Because Industrial Boiler internal combustion situation more complicated, the signal interference source is more, so must carry out filtering.Employing IIR low-pass filter filters (frequency) undesired signal in the combustion flame frequency signal that is mingled with in the signal among the present invention.By field experiment and test, the frequency of the combustion flame in the on-the-spot boiler is below 200Hz, so the low-pass filter of Shi Yonging mainly is the undesired signal that filtering is higher than frequency 200Hz in the present embodiment;
Described employing power spectrum computing module obtains the power spectrum of combustion flame.The present invention is by placing the fast fourier transform FFT formula of power spectrum computing module, time-domain signal is become frequency-region signal, be about to the power spectrum curve that intensity (ordinate)-time (horizontal ordinate) curve becomes intensity (ordinate)-frequency (horizontal ordinate) curve.Be the flare up fire intensity level under the respective frequencies.
Described power spectrumanalysis module is analyzed the power spectrum curve of above-mentioned acquisition, analyzes for the flame energy distribution under the different frequency, makes having or not fire to judge.
The effect of flame detecting method of the present invention is remarkable.
● in the detection method of the present invention, because comprise frequency signal in the signal of collection combustion flame, therefore, burning fame detecting system of the present invention can be by the frequecy characteristic of flame under the different fired states of comparison, by the frequecy characteristic situation of flame detection burning exactly;
● in the detection method of the present invention, because set up filtration module, unwanted undesired signal can be filtered, make that the characteristic frequency that detects is more accurate, the testing result of gained is more reliable and more stable;
● in the detection method of the present invention, because set up a burning fame detecting system that comprises power spectrum computing module and power spectrumanalysis module, calculate and power spectrumanalysis carry out frequency spectrum through filtered frequency signal, by the fast fourier transform FFT formula in the power spectrum computing module, calculate the intensity level under the respective frequencies, obtain the frequency of combustion flame and the power spectrum of intensity values corresponding (power), detect combustion flame based on power spectrum, can be comprehensive and more accurate reflect the combustion position of real flame.
● in the detection method of the present invention,, contain a different fuel in this module, the different type of furnaces, the database module of the flame combustion spectrum distribution characteristic pattern under the different fired states because comprise the power spectrumanalysis module in the burning fame detecting system of setting up.Therefore can be according to the Power Spectrum Distribution curve of the burning frequency of different fuel, compare the situation of flame detection burning so more accurately in real time with the power spectrum of the actual flame combustion that records.
Description of drawings
Fig. 1 is the structural representation of burning fame detecting system one embodiment that sets up of detection method of the present invention;
Fig. 2 is the process flow diagram of burning fame detecting system one embodiment of the present invention;
Fig. 3-1,3-2 are the process flow diagrams that detection method of the present invention adopts FFT formula operation one embodiment;
Fig. 4 is the characteristic curve diagram that the power spectrumanalysis module is stored in the burning fame detecting system set up of detection method of the present invention storage combustion flame normal frequency spectrum distributes.
Embodiment
Further specify the feature of detection method of the present invention below in conjunction with embodiment and accompanying drawing.
As mentioned above, the concrete steps of detection method of the present invention are:
＜1〉adopt the combustion flame pick-up unit to gather the combustion flame signal.In the present embodiment, the combustion flame pick-up unit that is adopted is to be provided by Shenming Control Engineering Co., Ltd., Shanghai.The flare up fire of combustion flame pick-up unit collection is the real-time burned flame signal of interior oil gun of boiler furnace or coal burner, the combustion flame signal enters in this device through photoelectric conversion section, this part is converted to electric signal by photodiode (PHOTODIODE) with light signal, be converted to voltage signal through discharge circuit again, then through the DC component in the capacitance removal flame voltage signal, only keep AC compounent (flash signal of flame), carry out processing and amplifying through discharge circuit again, ac voltage signal is amplified to proper level, delivers to the A/D change-over circuit at last.In conversion of signals and amplifying circuit, resistance is big more in this combustion flame pick-up unit, easy more being interfered, so the single-stage enlargement factor is difficult for excessively, must adopt the form of multistage amplifier circuit.This combustion flame pick-up unit adopts one-level current-voltage conversion circuit, one-level every the pre-amplifying circuit of direct sum homophase, two-stage in-phase amplification circuit and two-stage second-order active filter device.Current-voltage conversion of signals and signal amplify the use discharge circuit, select for use the design of suitable amplifier and discharge circuit most important, photoelectric sensor has a parameter to play a part most critical for the design of circuit, and that is exactly light sensitivity (Photo Spectral Sensitivity or Spectral Sensitivity).This combustion flame pick-up unit adopts ADI company to aim at the preposition amplification of photodiode and the operational amplifier (model is AD823) that designs, also comprises current-voltage conversion of signals and pre-amplifying circuit.The model that multistage amplifier circuit and active filter adopt TI company to provide is the four high guaily unit of LM224A (the perhaps OP484FS of ADI company).Send into the A/D change-over circuit at last through the analog voltage signal of a series of processing and be converted to 16 position digital signals.
The collection of flame data there is crucial effects to the accuracy of whole detection, so following method is adopted in data acquisition: in order to obtain the discrete spectrum distribution character of boiler flame signal, flame on time domain (in a period of time) carry out Digital Discreteization, promptly at first the time domain flare up fire is carried out every interval (uniformly-spaced) for 0.13ms continuous sampling 256 points, be defined as the sequence that length N equals 256 flame intensity signal.According to Shannon's sampling theorem, if the highest frequency of flame flicking signal is ft, for preventing mixing, selected sampling frequency fs 〉=2ft.In the present embodiment, the sample frequency fs that selects is 768Hz, by whenever being spaced apart 0.13ms to sample continuously 256 times strength signal of flame, through the digital signal processing (transfer process is in the power spectrum computing module in detail) that time domain is changeed frequency domain, can in the frequency domain scope, recover the frequency signal below the 384Hz.Flicker frequency according to (having data to show) boiler flame is no more than 250Hz, so such sample frequency is enough for the application of actual boiler flame.
＜2〉in computing machine, set up a burning fame detecting system (software), this burning fame detecting system is as shown in Figure 1: it comprises the signal acquisition module 101 that the combustion flame signal is gathered, the digital signal of gathering is carried out the filtration module 102 of Filtering Processing, carry out the power spectrum computing module 103 of rated output spectrum, and the power spectrumanalysis module 104 of power spectrum being analyzed contrast.The flow process of its detection as shown in Figure 2.
Fig. 2 is the process flow diagram of burning fame detecting system one embodiment.As shown in Figure 2, burning fame detecting system brings into operation, at first by the combustion flame pick-up unit regularly the combustion flame signal (digital signal) of (every interval 0.13ms) continuous acquisition be input in the burning fame detecting system in the signal acquisition module 101, in the present embodiment, signal acquisition module 101 is carried out digital signal samples with the sample frequency of 768Hz, is input in the filtration module 102 after counting when adopting full 256; Filtration module 102 adopts the IIR low-pass filter to filter undesired signal, signal is input to power spectrum computing module 103 again; Power spectrum computing module 103 adopts fast fourier transform (FFT) formula rated output spectrum, and the power spectrum of acquisition is input in the power spectrumanalysis module 104; The characteristic curve that the combustion flame normal frequency spectrum that power spectrumanalysis module 104 has been stored this power spectrum distributes compares, and differentiates the situation of flame combustion.
Described filtration module 102 adopts the filtering of IIR low-pass filter.The IIR low-pass filter carries out filtering with unwanted undesired signal.Because the flame more complicated of boiler internal combustion adds that environment is more abominable in the boiler, so gather the flare up fire more complicated.In the undesired signal that in A/D converts the process of digital signal to, may have some high frequencies by analog quantity, influenced the pure property of flare up fire.102 pairs of flame digital signal sequences of filtration module x (n), (as n=0～255) carry out filtering, the undesired signal of filtering high frequency.In the present embodiment, the IIR low-pass filter of employing is to be low frequency signal according to the combustion flame signal in the boiler in the present embodiment, and the flicker frequency of flare up fire is lower than 200Hz, so adopt the IIR low-pass filter.Its passband width is 0Hz～200Hz.
In the present embodiment, the specific targets of IIR low-pass filter are:
Cut-off frequecy of passband Wp:200Hz; Stopband cutoff frequency Ws:350Hz;
Pass band damping Rp:0.5db; Stopband attenuation Rs:20db; Sample frequency Fs:768Hz.
Actual filter coefficient is drawn by matlab emulation:
By calling the matlab function:
[n, wn]=buttord (Wp/ (Fs/2), Ws/ (Fs/2), Rp, Rs) and [b, a]=butter (n, wn)
The filter coefficient a, the b that calculate:
a1＝1； a2＝0.88492； a3＝0.31357
b1＝0.54962； b2＝1.0992； b3＝0.54962
The difference equation of wave filter is:
y(n)＝0.54962*x(n)+1.0992*x(n-1)+0.54962*x(n-2)-0.88492*y(n-1)-0.31357*y(n-2)；
Power spectrum computing module 103 in the described burning fame detecting system adopts fast fourier transform (FFT) formula rated output spectrum.For obtaining the flame power spectrum, it at first to carrying out the FFT computing through filtered signal, is converted to frequency domain (energy-frequency curve) with signal by time domain (energy-time curve), calculates the energy value of signal on each frequency band.As in the present embodiment being the flame of boiler internal combustion, when boiler combustion, exist main flame and background flame in the burner hearth, there is very big difference in the frequency of main flame and the flicker of background flame burning, by the furnace flame signal frequency-domain is analyzed, main flame and the energy value of background flame on different frequency bands are very different.So flicker frequency by the main flame of locking, the standard-frequency signal (power spectrum) that utilization is stored in the interior flame combustion database module of power spectrumanalysis module is analyzed, can go out and remove the background flare up fire that is different from main flame flicking frequency effectively respectively, can solve the disconnected problem of the erroneous judgement that detects for flame in the burner hearth preferably.
Described power spectrum computing module carries out frequency spectrum to the frequency signal through above-mentioned filtration module filtering interference signals and calculates, and employing FFT formula calculates the intensity level under the respective frequencies.As above-mentioned, be to calculate the intensity level of boiler combustion flame under characteristic frequency in the present embodiment, carry out spectrum analysis to sampled data x (n).Adopt the fast fourier transform of decimation in time (DIF) base 2 in the present embodiment.According to the discrete Fourier transform (DFT) on the signal Processing, this group signal x (n) is done the FFT computing just can obtain the correspondence of this time-domain signal on frequency domain and represent that the FFT conversion formula that is adopted is:
Wherein x (n) be row length be 256 (n=0,1 ... 255) list entries; X (k) is a spectrum factor after the discrete Fourier transform (DFT) of sequence x (n) of N for the limit for length is arranged, and X (k) be plural, W
N=e
-j (2 π/N)Be the butterfly coefficient of FFT calculating, N=256 in the present embodiment.
The calculation process of described FFT conversion formula 1 such as Fig. 3-1, Fig. 3-2.
Because X (k) is a plural number, then can convert thereof into power spectrum P (k), conversion formula is:
P(k)＝|X(k)|
2/N，k＝0～(N-1) …………(2)
Fig. 3-1,3-2 are the concrete calculation process of above-mentioned formula (1), and wherein Fig. 3-1 is the bit reversed order flow process, and it finishes the bit reversed order operation.In the FFT computing, N is necessary for 2 integral number power, and A in the calculation process (I) is natural order (for original data sequence), but calculates in order to adapt to original position, should carry out inverted order to sequence A (I) earlier before computing.A among Fig. 3-1 (J) is the bit reversed order sequence.The rule of inverted order is exactly that the binary digit of Ser.No. is inverted, and can obtain the inverted order value.The inverted order number is to add one in M bit most significant digit, meets 2 carries to the right.For, the weights of M bit most significant digit are N/2, and from left to right the weights K of binary digit is followed successively by power N/4, N/8 ..., 2,1.Therefore, most significant digit adds one and is equivalent to decimal arithmetic J+K.(J represents the decimal system numerical value of current inverted order number).
Fig. 3-2 is the flow process that FFT formula (1) calculates, and is the sequence input of separating by the time, and the flow process of carrying out the FFT computing.U among Fig. 3-2, W, J are plural number; I, IP are two nodes of butterfly knot; M is a place progression; LE is a butterfly knot spacing; LEI is two nodal pitches participating in computing in the same butterfly; J is a loop variable.Setting L is that whole FFT calculates nested loop number of times, wherein L=Log2N.The whole circulation recursive process is made of three nested loop.The computing that cycle index of outer cycle control is L, each dish-like computing of the same one-level of the cycle control of internal layer (M is identical), M represents that (M is 1,2,3 to the M level ... L).Wherein interior one deck cycle control is with a kind of computing of dish-like knot, and middle one deck is then controlled the computing of different dish-like knots.
Innermost loop among Fig. 3-2, its loop variable are I, and I is used for control with a kind of dish-like knot computing.Obviously its step value is dish-like knot distance values LE, and wherein LE=2M is LE1, wherein LE1=2M-1 with the spacing of participating in two nodes of computing in a kind of dish-like knot.
The second layer circulation of Fig. 3-2, its loop variable J is used for controlling the dish-like knot that calculates (different coefficient) not of the same race, and the step value of J is 1.
Fig. 3-2 outermost loop is controlled the progression of computing with loop variable M, and M is 1～L, when M changes, and LE1 then, LE and coefficient U can change.
The characteristic curve diagram (see figure 4) that power spectrumanalysis module 104 portion's storage within it combustion flame normal frequency spectrum distributes in the described burning fame detecting system.
Fig. 4 is stored in three typical cases (standard) spectral distribution curve in power spectrumanalysis module 104 database module.Horizontal ordinate is a frequency, and ordinate is a power.
Curve 02 is the spectral distribution curve of gaseous combustion, and center (peak power place) frequency mainly is distributed in the scope about 40Hz, and its frequency range is in the scope about 30～60Hz;
As shown in Figure 4, the histogram of flame combustion is exactly the database of the different flame combustion situations of different fuel in the boiler in fact.According to on-the-spot test and analysis of experiments, flame combustion has following feature: when fuel was coal dust, the energy of flame combustion concentrated in the frequency band range of 15Hz substantially; When fuel was gas, the energy of flame combustion concentrated in the frequency band range of 40Hz substantially; When fuel was heavy oil, the energy of flame combustion concentrated in the frequency band range of 80Hz substantially.
After calculating by the FFT power spectrum, the power spectrumanalysis module is compared to the Actual combustion flame power spectrum of acquisition and the flame combustion spectrum distribution characteristic pattern of standard, in conjunction with to the flame characteristic frequency and have or not the default definite value of fiery threshold value, realize accurate judgement to (single burner or multi-combustor) boiler internal combustion flame status.
Claims (4)
1. the detection method of a combustion flame is characterized in that the concrete steps of detection method are:
＜1〉at first adopt the combustion flame pick-up unit to gather the combustion flame signal, this signal be included in time-limited time domain and the frequency domain uniformly-spaced the time-domain signal of continuous sampling and frequency-region signal and with the corresponding flame intensity signal of frequency-region signal, and convert digital signal to;
＜2〉at the built-in burning fame detecting system of computing machine, in this burning fame detecting system, set up signal acquisition module, filtration module, power spectrum computing module and power spectrumanalysis module;
＜3〉the flame combustion digital signal of above-mentioned collection is input in the burning fame detecting system in the aforementioned calculation machine, filter undesired signal by the filtration module in the burning fame detecting system, calculating by the power spectrum computing module obtains power spectrum, be analyzed by the power spectrumanalysis module, provide the power spectrum after the comparison;
＜4〉according to the above-mentioned power spectrum that provides, the situation of analytic combustion flame.
2. the detection method of combustion flame according to claim 1 is characterized in that described filtration module adopts the filtering of IIR low-pass filter.
3. the detection method of combustion flame according to claim 1 is characterized in that described power spectrum computing module adopts the fast fourier transform formula to obtain power spectrum.
4. the detection method of combustion flame according to claim 1 is characterized in that described power spectrumanalysis module portion's storage within it combustion flame normal frequency spectrum distribution characteristics curve map.
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| CN106652307A (en) * | 2016-12-05 | 2017-05-10 | 郑州大学 | Subway station heat release rate prediction method based on flame oscillation frequency detection |
| CN108010253A (en) * | 2017-11-24 | 2018-05-08 | 上海曜成电子科技有限公司 | A kind of flame detection method and device |
| CN110578941A (en) * | 2018-06-08 | 2019-12-17 | 宁波方太厨具有限公司 | Automatic control system of range hood and control method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106384102A (en) * | 2016-09-30 | 2017-02-08 | 深圳火星人智慧科技有限公司 | IR-card-equipped day-night digital network camera flame detection system and method |
| CN106652307A (en) * | 2016-12-05 | 2017-05-10 | 郑州大学 | Subway station heat release rate prediction method based on flame oscillation frequency detection |
| CN106652307B (en) * | 2016-12-05 | 2019-04-23 | 郑州大学 | The prediction technique of Subway Station Fire power based on flame oscillation frequency sonding |
| CN108010253A (en) * | 2017-11-24 | 2018-05-08 | 上海曜成电子科技有限公司 | A kind of flame detection method and device |
| CN108010253B (en) * | 2017-11-24 | 2020-01-21 | 上海曜成电子科技有限公司 | Flame detection method and device |
| CN110578941A (en) * | 2018-06-08 | 2019-12-17 | 宁波方太厨具有限公司 | Automatic control system of range hood and control method thereof |
| CN110578941B (en) * | 2018-06-08 | 2021-04-16 | 宁波方太厨具有限公司 | Automatic control system of range hood and control method thereof |
| CN110617627A (en) * | 2018-06-19 | 2019-12-27 | 芜湖美的厨卫电器制造有限公司 | Gas water heater |
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