RU2072480C1 - Flame check device - Google Patents

Abstract

FIELD: heat-power engineering; thermal power stations and boiler plants working on gaseous and liquid fuel. SUBSTANCE: device is provided with the following units arranged in series in optical axis: projection unit, flame radiation spectral components separation unit, photodetector unit, converter unit and unit for communication with computer. Flame radiation spectral components separation unit is made in form of disperse element and telescopic system with spectral filter and multi-channel deflecting element located in series in optical axis in focal plane of first objective of telescopic system; spectral filter has M slots. Multi-channel deflecting element consists respectively of M sections. Photodetector unit has linear multi-element photodetector; string of photosensitive elements is located in focal plane of second objective of telescopic system in parallel with row of slots of spectral filter. EFFECT: enhanced efficiency. 2 cl, 5 dwg

Description

 The invention relates to a power system, and in particular to devices for automatic control of the flame of burners of various heat generating units, and can be used in thermal power plants and boiler plants operating on gaseous and liquid fuels.

 A known flame detector [1] which uses the phenomenon of fluctuations in flame during combustion. The sensor contains a lens focusing the image of the flame on the surface of the photosensitive matrix, which contains two groups of photodetectors connected respectively to two buses. The sensor contains a circuit for isolating the difference of the signals from the indicated groups of photodetectors and a threshold key element that is triggered when the difference signal exceeds a predetermined level. The number of elements in the matrix can be arbitrary.

 The disadvantage of this device is the low reliability of the selective control of the flame of the burners with the simultaneous presence of several working burner devices, since at any time the output signal from the group of photodetectors is the sum of the signals from individual photodetectors of the group. When changing the operation mode of one of the burners, changing the output signal from the group of photodetectors may not be sufficient for the threshold element to operate. In addition, the sensor uses only one method of monitoring the flame by its oscillations as the basis and does not use a combination of different methods that increase the reliability of the control.

 A device [2] for controlling a flame is also known, comprising a projection device, a beam splitter, dividing the radiation beam coming from the flame into two separate beams, and two radiation receivers. The first receiver detects the infrared components of one beam, and the second receiver detects the UV components of another beam. The receivers can transmit an analog signal characterizing the flicker frequency of the IR component and a digital signal characterizing the total energy of the UV component to the processor. The processor decides on the state of the flame.

 The disadvantage of this device is the low reliability of the selective control of the torch of one burner device in case of simultaneous operation of several burners due to the unstable position of the sighting point of the control device, depending on the effect of torches of neighboring burners. In addition, this device cannot be used for simultaneous selective control of the torches of several burners, since the use of two single photodetectors does not provide the separation of information from several burner devices.

 Closest to the proposed one is a method and device for detecting or monitoring a flame [3] comprising registering the radiation of a flame in two fixed ranges and measuring the ratio of intensities in these ranges. The device comprises a projection unit, a unit for isolating the spectral components of the flame radiation, a photodetector unit, comparison, indication and ignition units. The unit for isolating the spectral components of the flame radiation is made in the form of a dichroic beam splitter, and the photodetector unit includes two single photodiodes. In the device in question, the ratio of the intensities of the radiation of the wavelength in the region of 470-530 nm and a wavelength of about 670 nm is measured. The value of this ratio from 0.1 to 1.0 means the presence of flame; if the ratio is outside these limits, there is no flame, and a signal is supplied to the ignition unit.

 This device does not provide the possibility of selective monitoring of several burners at the same time due to the use of single photodetectors, which record the intensity of the total flame in certain spectral ranges. Against the background of a strong signal from a common flame, selective control of a single torch will be unreliable. In addition, when using single photodetectors, it is not possible to analyze the spatial distribution of flame parameters, which can increase the reliability of the selective control of torch torches. In the considered device, information is recorded only in two spectral ranges, while the spectral composition of flame radiation during the combustion of hydrocarbon fuels has a larger number of characteristic spectral ranges, the simultaneous operation of which also increases the reliability of control.

 The purpose of the invention is the expansion of the functionality of the device and improving the reliability of selective flame control.

 The proposed device comprises a projection unit sequentially located on the optical axis, a unit for isolating the spectral components of the flame radiation and a photodetector unit, as well as a conversion unit and a computer communication unit.

 The proposed device is characterized in that the unit for separating the spectral components of the flame radiation is made up of a dispersing element and a telescopic system sequentially located on the optical axis with a spectral filter and a multi-channel deflecting element installed in the focusing plane of the illuminating beam by the first lens of the telescopic system, the spectral filter having M slots, the multichannel deflecting element consists of M sections, respectively, and the photodetector unit contains a linear photocell detector, the line of photosensitive elements of which is located in the focal plane of the second lens of the telescopic system parallel to a number of slots of the spectral filter.

 In addition, the photodetector unit contains a driver of linear multi-element photodetector control signals, the first input of which is connected to the output of the first generator, the second and third inputs, respectively, through the first and second single vibrators are connected to the output of the second generator. Each output of the shaper of control signals of the linear multi-element photodetector is connected through a corresponding amplifier to the corresponding input of the linear multi-element photodetector, the output of which is connected through the signal amplifier to the input of the conversion and computer communication unit.

 In FIG. 1 is a diagram of the proposed flame control device (1a side view, 1b top view); figure 2 diagram of the photodetector block; figure 3 an example implementation of anamorphic lens; figure 4 timing diagrams of the operation of the photodetector block; figure 5 is a block diagram of one of the possible algorithms for processing information in a computer.

 The proposed device (figure 1) consists of sequentially located on the same optical axis of the projection unit 1, the unit for extracting the spectral components of the radiation of the flame 2, the photodetector unit 3. The conversion and communication unit 4 is connected to the output of the photodetector unit 3. In turn, the unit for isolating the spectral components of the radiation of flame 2 consists of a dispersing element 5 sequentially located on the optical axis and a telescopic system 6 with a spectral filter 7 and a multi-channel deflecting element 8 installed in the focusing plane of the illuminating beam by the first lens of the telescopic system 6. Moreover, the spectral filter 7 made in the form of M slots, and the multi-channel deflecting element 8 consists respectively of M sections. The composition of the photodetector unit 3 includes a linear multi-element photodetector (LMF) 9, the line of photosensitive elements of which is located in the focal plane of the second lens of the telescopic system 6 parallel to the row of slots of the filter 7.

 The photodetector unit 3 (Fig. 2) consists of a series-connected clock pulse generator 10, a driver 11 of the LMF control signals, a node 12 of the amplifiers of the LMF control signals, an amplifier 13 of the LMF signals. Moreover, each of the six outputs of the driver 11 of the LMF control signals is connected to the corresponding input of the amplifier of the amplifier unit 12 of the control signals, consisting of six identical amplifiers, and each of the six outputs of the node 12 is connected to the corresponding one of the six inputs of the LMF 9. The photodetector unit 3 also includes a rectangular pulse generator 14, single vibrators 15 and 16. The output of the generator 14 is connected to the inputs of the single vibrators 15 and 16, and the outputs of the single vibrators 15 and 16 are connected respectively to the second and third inputs of the driver i am 11.

 The proposed device operates as follows.

 The image of a series of N burners 17 by the projection unit 1 is displayed on the plane of the dispersing element 5 of the unit 2 for separating the spectral components of the flame radiation, at which the light beams are deflected at different angles depending on the radiation wavelength. As the dispersing element 5, for example, a diffraction grating or a prism can be used. The telescopic system 6 projectively couples the plane of the dispersing element 5 and the LMF plane 9. The first lens of the telescopic system 6 of block 2 performs the Fourier transform of the input image, so that the light distribution in the focus plane of the illuminating beam by the first lens of the telescopic system 6 is a composition shifted relative to each other other (depending on the radiation wavelength) and spatial Fourier spectra located parallel to a number of burners th torch burners.

где d_m размер m-й щели, l_m длина волны излучения, f - фокусное расстояние первого объектива системы 2, δ размер элемента разрешения входного изображения. Ширину выделяемой спектральной полосы излучения Dl_ср в линейном приближении можно оценить из соотношения

где d_cp средняя ширина щели, λ_max и λ_min значения максимальной и минимальной длин волн излучения, D апертура объектива. Тогда ширина выделяемой спектральной полосы излучения ограничивается величиной

где g = f/D светосила объектива. Например, при значениях параметров λ_max 0,9 мкм, λ_min 0,4 мкм, γ 1,5 мкм и d 50 мкм ширина выделяемой спектральной полосы будет ограничиваться величиной Dl_ср≥ 10 нм.The spectral filter 7 of block 2 transmits burner images in narrow wavelength ranges Δλ _m ,, where m is the slot number. The minimum slit size is determined by the spatial spectrum of the input image

where d _{m is the} size of the mth slit, l _m is the radiation wavelength, f is the focal length of the first lens of system 2, δ is the size of the resolution element of the input image. The width of the emitted spectral band of radiation Dl _cf in the linear approximation can be estimated from the relation

where d _{cp is the} average slit width, λ _max and λ _min are the maximum and minimum radiation wavelengths, D is the lens aperture. Then the width of the emitted spectral band of radiation is limited by

where g = f / D aperture of the lens. For example, with the parameter values λ _max 0.9 μm, λ _min 0.4 μm, γ 1.5 μm and d 50 μm, the width of the emitted spectral band will be limited to Dl _cf ≥ 10 nm.

где L длина ЛМФ 9, М число щелей спектрального фильтра 7, а l - размер изображения горизонтального ряда горелок 17 во входной плоскости телескопической системы 6. Углы отклонения многоканального отклоняющего элемента 8 выбираются из такого расчета, чтобы в каждом последующем канале изображения горелок на ЛМФ 9 в направлении, параллельном ряду горелок 17, были сдвинуты на величину L/M, равную размеру этого изображения. Для этого угол отклонения m-го элемента выбирается равным

где m=1,2,М.Light beams passing through the slots of the spectral filter are deflected by the multi-channel deflecting element 8 of block 2 and transmitted to the plane of the LMF 9 of the photodetector block 3 by means of a second lens of the telescopic system 6. The multi-channel deflecting element 8 can be made of a set of consecutive triangular prisms with different angles at the apex . As the LMF 9, a photodiode array operating in the signal accumulation mode, FUK1L2, can be used. The magnification coefficient k of the telescopic system 6 is determined by

where L is the length of the LMF 9, M is the number of slots of the spectral filter 7, and l is the image size of the horizontal row of burners 17 in the input plane of the telescopic system 6. The deflection angles of the multichannel deflecting element 8 are selected so that in each subsequent channel of the image of the burners on the LMF 9 in the direction parallel to the row of burners 17, were shifted by L / M equal to the size of this image. For this, the deviation angle of the mth element is chosen equal to

where m = 1,2, M.

At a different coordinate, the image of the torch torches from the plane of the dispersing element 5 is also transferred by the telescopic system 7 to the plane of the LMF 9 (Fig. 1b). The LMF integrates the incident light flux in the direction perpendicular to the direction of the row of burners 17, for which a photodetector with elements extended along this direction is used (Fig. 1b, view A). Additional integration can be performed by using a focon or anamorphic optics as part of the photodetector 3, which integrate light beams in the direction perpendicular to the row of burners 17. An example of the use of anamorphic optics is shown in FIG. 3. In this case, the composition of the photodetector unit 3 includes two cylindrical lenses 18 and 19 (Fig. 3) with focal lengths f _x and f _y , respectively, projecting the image from the output plane of the telescopic system 6 of the unit for extracting the spectral components of the radiation of flame 2 (plane P ₁ ) in the plane of the photodetector elements of the LMF 9 (plane P ₂ ) with different magnifications in X (fig.3a) and Y (fig.3b) coordinates. By changing the ratio of focal lengths f _x and f _y , you can change the magnification (decrease) of the input image in X and Y coordinates. In Fig. 3, the direction of the coordinate axis X coincides with the direction of the row of burners 17 (Fig. 1a). The direction of the y axis is perpendicular to the x axis.

 Integration of the torch image multiplied by different wavelengths along one coordinate allows to increase the information content of the signal and improve the signal-to-noise ratio at the output of the photodetector unit 3.

 After registration of light signals at the LMF 9 is completed, it is read. In block 4 of the conversion and communication with the computer, the output signal from the photodetector block 3 is converted from analog to digital and transmitted to the computer. The conversion and communication unit 4 can be implemented as part of one of the standard interfaces, providing software exchange of information with a computer using standard exchange protocols.

Let us consider in more detail the operation of the photodetector unit 3. The photodetector unit operates in an autonomous mode, providing periodic erasure, accumulation and reading of information from the LMF 9. Generator 14 generates a continuous sequence of rectangular pulses (Fig. 4a). The single-vibrator 15 generates narrow pulses "Launch erase" the LMF on the leading edges of the pulses from the generator 14 (Fig.4B), and the single-vibrator 16 forms the "Trigger reading" LMF on the leading edges of the pulses (Fig.4B). With the arrival of the “Start Erase” pulse in the driver 11 of the LMF control signals from clock pulses (Fig. 4d), a sequence of signals is generated from the generator 10 from the erasing phases Ф _1ст , Ф _2ст , Ф _оst in accordance with the diagrams shown in Fig. 4e, e , w. These signals from the three outputs of the shaper 11 are amplified in three identical power amplifiers 12 and are supplied to the corresponding inputs of the LMF 9. When the LMF 9 is supplied as shown in Fig.4d, f, g signals Ф _st , the previous information is erased on the elements of the LMF 9 by charging the capacitance photodiodes up to some constant voltage. After erasing the information on all the photodiodes before the “Start reading” pulse, the LMF 9 is in the signal accumulation mode. The next erasing cycle will be repeated only when the corresponding pulse is received at the input Ф _оst LMF9 in phase Ф _оst from the shaper 11, which is formed from the signal “Erase start”. With the arrival of the signal “Start of reading” to the shaper 11 from the generator 14, a sequence of signals is generated in it according to the read phases Ф _1сч , Ф _2сч , Ф _ocч by analogy with the diagrams shown in fig.4d, e, g. These signals from the 4th, 5th, 6th outputs of the shaper 11 are amplified in three identical power amplifiers of the amplifier unit 12 and are fed to the corresponding inputs of the LMF 9. When the signals Ф _1сч , Ф _2сч , Ф _ocч are _fed to the _LMF , the registered information is read to the LMF output 9. Next, the signal is amplified in the amplifier 13 and is fed to the output of the photodetector unit 3.

 Shaper 11 of the control signals LMF 9 can be implemented on a series 555 microcircuits taking into account the above time diagrams of work.

 The pulse generators 14 and 10 can be performed on the microcircuit series 155 or 555.

 As single vibrators 15 and 16, the 155AG3 (555AG3) chip can be used.

 As the amplifier 13, you can use the operational amplifier K544UD1A.

 The light distribution read by a linear multi-element photodetector for subsequent data input into a computer is M one-dimensional images of a number of burners, respectively, in M spectral ranges. Further processing of the received signals can be performed in various ways. In particular, histogram analysis, other methods for converting or improving image quality may be used.

где n номер горелки, m номер спектрального диапазона, К количество элементов фотоприемника на одну горелку, k ≅ [1,K] Далее вычисляются отношения суммарных сигналов в различных спектральных диапазонах для каждой горелки (т.е. производится попарная нормировка сигналов в различных спектральных диапазонах):
a $\genfrac{}{}{0ex}{}{\text{n}}{\text{m0,m1}}$ =I $\genfrac{}{}{0ex}{}{\text{n}}{\text{m0}}$ / I $\genfrac{}{}{0ex}{}{\text{n}}{\text{m1}}$
где m_o номер нормируемого спектрального диапазона горелки;
m₁ номер нормирующего спектрального диапазона горелки, m_o ≠ m₁.The data read by a linear multi-element photodetector are entered into a computer (Fig. 5). Within each spectral range, the summation of the signals from the photodetector elements corresponding to one burner is carried out, the total signals are calculated

where n is the number of the burner, m is the number of the spectral range, K is the number of photodetector elements per burner, k ≅ [1, K] Next, the ratios of the total signals in different spectral ranges for each burner are calculated (ie, pairwise normalization of signals in different spectral ranges is performed ):
a $\genfrac{}{}{0ex}{}{\text{n}}{\text{m0, m1}}$ = I $\genfrac{}{}{0ex}{}{\text{n}}{\text{m0}}$ / I $\genfrac{}{}{0ex}{}{\text{n}}{\text{m1}}$
where m _{o the} number of the normalized spectral range of the burner;
m ₁ number of the normalizing spectral range of the burner, m _o ≠ m ₁ .

 At this stage, in the simplest case, the ratio of the magnitude of the signal in a given spectral range to the total signal for the burner over all spectral ranges can be used, however, the presented normalization method provides greater flexibility in developing a decision rule. This operation can be performed both over all spectral ranges and over some of their samples.

т. е. значения коэффициентов, попадающих в диапазон допустимых величин, приравниваются единице, а большие или меньшие нулю. Окончательное определение спектральных диапазонов, в которых должна производиться взаимная нормировка сигналов, и значение величин P $\genfrac{}{}{0ex}{}{\text{min}}{\text{m0,m1}}$ и a $\genfrac{}{}{0ex}{}{\text{n}}{\text{m0,m1}}$ осуществляется в процессе настройки системы контроля в конкретных рабочих условиях.Threshold processing of the calculated coefficients a $\genfrac{}{}{0ex}{}{\text{n}}{\text{m0, m1}}$ performed by comparing them with the maximum (P $\genfrac{}{}{0ex}{}{\text{max}}{\text{m0, m1}}$ ) and minimal (P $\genfrac{}{}{0ex}{}{\text{min}}{\text{m0, m1}}$ ) allowable signal ratios for different spectral ranges according to the following rule:

i.e., the values of the coefficients falling into the range of permissible values are equal to unity, and large or less than zero. The final determination of the spectral ranges in which the mutual normalization of the signals should be carried out, and the value of the values of P $\genfrac{}{}{0ex}{}{\text{min}}{\text{m0, m1}}$ and a $\genfrac{}{}{0ex}{}{\text{n}}{\text{m0, m1}}$ carried out in the process of setting up a control system in specific operating conditions.

. Решение о том, работает горелка или нет, принимается путем сравнения значения сⁿ c минимально допустимым c_min, которое, как и в предыдущем случае, определяется в процессе настройки системы контроля в конкретных рабочих условиях в зависимости от допустимых режимов работы горелки и возможных изменений в составе топлива. В случае, если cⁿ < c_min, выдается сообщение о погасании горелки, если сⁿ ≥ c_min сообщение о нормальной работе. Кроме того, возможно введение сравнения с промежуточным порогом c_min1, и при условии c_min1 > cⁿ > c_min может выдаваться сообщение о серьезных изменениях в режиме работы горелки.After the threshold treatment, for each burner, the total number of coefficients falling into the range of admissible values is calculated

. The decision about whether the burner works or not is made by comparing the value with ⁿ with the minimum allowable c _min , which, as in the previous case, is determined in the process of setting up the monitoring system in specific operating conditions depending on the permissible operating conditions of the burner and possible changes in fuel composition. If c ⁿ <c _min , a burner extinction message is issued if, with ⁿ ≥ c _min , a normal operation message is displayed. In addition, it is possible to introduce a comparison with the intermediate threshold c _min1 , and provided c _min1 > c ⁿ > c _min , a message can be issued about serious changes in the burner operation mode.

Claims (2)

 1. A flame monitoring device comprising a projection unit and a unit for isolating the spectral components of the flame radiation connected in series with the photodetector unit connected via a conversion and communication unit to an electronic computer, characterized in that the unit for isolating the spectral components of the flame radiation is made from sequentially located on the optical axis of the dispersing element, a telescopic system with a spectral filter and multi-channel deflecting e with an element installed in the focus plane of the first lens of the telescopic system illuminating the beams, the spectral filter having M slots, the multi-channel deflecting element consists of M sections, respectively, and the photodetector block contains a linear multi-element photodetector, the line of photosensitive elements of which is located in the focal plane of the second lens of the telescopic system a number of slots of the spectral filter.  2. The device according to claim 1, characterized in that the photodetector unit comprises a driver for controlling a linear multi-element photodetector, the first input of which is connected to the output of the first generator, the second and third inputs, respectively, are connected to the output of the second generator through the first and second single vibrators, and each output the shaper of the control signals of the linear multi-element photodetector is connected through an appropriate amplifier to the corresponding input of the linear multi-element photodetector, the output of which is black Without a signal amplifier, it is connected to the output of the conversion and communication unit with an electronic computer.

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