RU2805134C1 - Panoramic multispectral visualization device for studying combustion processes - Google Patents

Abstract

FIELD: spectroscopy.

SUBSTANCE: panoramic multispectral imaging device for studying combustion processes. The device consists of an optical emission spectrometer unit, a spectral camera unit, a shadow instrument unit and a data processing unit. The data processing unit is configured to receive data from the optical emission spectrometer unit, the spectral camera unit and the shadow device unit, to isolate the spectral bands of chemiluminescence of excited hydroxyl OH*, C₂ Swann molecular vibrational bands, chemiluminescence of excited hydrocarbon CH* and molecular bands of CO and CO₂. The optical emission spectrometer unit is additionally connected by a control communication channel to the data processing unit and is configured to determine the presence of interfering components and transmit a control signal about the presence of interfering spectral components to the data processing unit.

EFFECT: possibility of simultaneously obtaining a temperature field, relative heat release rates, and combustion completeness coefficients and eliminating the possibility of incorrect interpretation of the combustion process.

1 cl, 2 dwg

Description

The invention relates to panoramic multispectral imaging devices and can be used to study the combustion processes of various types of fuel.

The study of the energy and spatiotemporal characteristics of combustion can be carried out by recording the emission spectra of the active components of the flow. Most often, the emission of electronically excited radicals OH* or CH* is studied using special spectral recording devices. Linear spectrometers or single-channel panoramic spectral recording cameras are used. The disadvantage of these devices is the inability to simultaneously interpret a wide spectrum of radiation and the spatial distribution of spectral components.

The basis of these systems is panoramic recording of spectral-selective data. This type of equipment is widely used to study the earth's and water surfaces from space. Multi- and hyperspectral sensing devices for the atmosphere and surfaces of land and water have contributed to the development of multispectral systems for the study of luminous media and light phenomena resulting from chemical, electromagnetic or radiative excitation of mono- and polyatomic gases. One of the most common light phenomena in technology is associated with the combustion processes of hydrocarbon fuels in the combustion chambers of furnaces and various engines. The main characteristics of the flame are the spatial distribution of temperatures of the chemical components of the flame, combustion completeness coefficients and heat release rates. All these characteristics together make it possible to evaluate the efficiency of the combustion process.

Most known devices for flame visualization are tuned to one spectral component and do not visualize complex characteristics, but only the emission intensity of a separate spectral component, which does not make it possible to evaluate the combustion efficiency, but only to get an idea of the spatial distribution of the selected chemical component of the flame. Obtaining complex flame characteristics is associated with an increase in the number of heterogeneous measuring channels in the visualization system and the use of intensive processing of recorded data, that is, the use of multichannel multispectral systems.

From the existing state of the art, the approach described in the article by Lauer, M., and Sattelmayer, T., “On the adequacy of chemiluminescence as a measure for heat release in turbulent flames with mixture gradients” // Journal of Engineering for Gas Turbines and Power . - 2010. - T. 132. No. 6, pp. 1-8.

This paper examines the use of a device for panoramic multispectral visualization of relative heat release rates in flames, taking into account the distribution fields of combustion completeness coefficients and flame turbulence intensity. As the main measuring units, instead of panoramic spectral cameras, a planar coherent laser-induced luminescence OH-PLIF unit is used to measure the luminescence fields of chemiluminescence of excited radicals, and instead of a shadow device to study the flame structure, a laser digital anemometry system based on PIV particle images is used. The disadvantages of this device are the use of complex pulsed coherent equipment, and the recorded data must undergo post-processing, and the lack of output of temperature fields, which does not make it possible to correctly assess the flame structure in real time.

Also known is the device described in the article Ikeda, Y., Nishiyama, A., Kim, S., Kawahara, N., and Tomita, E., “Anchor point siructure measurements for laminar propane/air and methane/air premixed flames using local chemiluminescence spectrum" // Proceedings of the 31st International Symposium on Combustion. 2006.

The system under consideration uses a phenomenological approach using an empirical formula for logical-arithmetic pixel-by-pixel image synthesis (several panoramic fields are used). An approach based on joint analysis of ultraviolet and blue panoramic channels (measuring units) is considered.

The disadvantage of this device is the lack of control of the emission spectrum using a linear spectrometer, and, as a consequence, the lack of correction of the relative heat release rate field for the emission spectrum of “interfering” spectral components, such as CO and CO ₂ .

The well-known article is Lauer, M., 2011. “Determination of the heat release distribution in turbulent flames by chemiluminescence imaging.” PhD thesis, Technische Universitat Munchen. The article describes a multichannel device for multispectral analysis of combustion processes. The device also allows you to determine the flow velocity field using the PIV method (particle image velocimetry - measurement of flow velocity by recording the movement of particles embedded in the flow). Correction of the ultraviolet channel is used based on modeling the distribution of radiation in the spectra of excited radicals OH*, CH*, C2 and CO2.

The disadvantage of the described device is the absence of a module for determining temperature from the continuous thermal spectrum of soot radiation using a linear spectrometer. Continuous recording of emission spectra has been replaced by a software module for mathematical modeling of optical spectra. The spectral temperatures of the components used in the correction algorithms, obtained in calculations for electronically excited levels, differ greatly from each other as a result of the complex chemical nature of the excitation and do not take into account the issues of copying the energy distribution over the vibrational and rotational levels of molecules from the ground level to the electronically excited levels. All of these disadvantages make it impossible to correctly visualize the combustion process.

The application Multispectral Flame Detector is known (No. US 20140184793 A1, IPC G08B 17/25, publication date 07/03/2014). This device uses multispectral cameras that operate exclusively in the thermal part of the infrared radiation spectrum, which does not allow determining the distribution field of the relative heat release rate.

The disadvantage of this device is also the absence of a control linear spectrometer, which positions this device as nothing more than a flame detector.

The prototype is the “System for multispectral panoramic visualization of combustion flows”, D.V. Bezrukov, V.V. Vlasenko, M.A. Ivankin, A.N. Morozov, V.M. Rybakov, “Models and methods of aerodynamics” Proceedings of the Twentieth International School-Seminar, Moscow 2020, pp. 23-24.

The device under consideration is a system for multispectral panoramic visualization of combustion flows, used on a high-enthalpy stand to study the process of ethylene combustion in a high-speed flow. The device detects radiation from excited molecular components in a wide spectral range of optical radiation and contains nine panoramic channels, including five spectral cameras and four high-definition visible cameras, two spectral linear channels of optical emission spectrometers, and a channel representing a shadow device.

The recording channel of the optical emission spectrometer is a block that includes focusing optics, a broadband optical spectrometer, while the optical emission spectrometer block is connected by a transmission line to the monitor and allows for analysis of the emission spectra of the flux with combustion. The recording channel of the spectral camera is a block that includes an optical spectral filter, image-forming optics, a camera with a matrix photodetector, and the spectral camera block is connected by a transmission line to the monitor and allows one to obtain the emission intensities of the spectral components of the flame. The channel of the shadow device is a block that includes a radiation source, collimators, a visualizing diaphragm, a spectral camera consisting of an optical spectral filter, image-forming optics, a camera with a matrix photodetector, while the shadow device block is connected by a transmission line to the monitor and makes it possible to obtain shadow picture of the flame. Data from all blocks are simultaneously displayed on the monitor.

The disadvantage of the device is the absence of a module for generating the main spatial characteristics of the process, namely the temperature field, the field of relative heat release rates and the field of combustion completeness coefficients. The spectrometers available in the device are not used to control the operation of the system, and the described device contains only a set of scattered recording channels, which does not allow for complete correct visualization of the combustion process.

The objective and technical result of the claimed invention is the development and creation of a panoramic multispectral visualization device for studying combustion processes, which will simultaneously obtain temperature fields, relative heat release rates and combustion completeness coefficients.

The solution to the problem and obtaining a technical result is ensured due to the fact that the panoramic multispectral imaging device for studying combustion processes consists of an optical emission spectrometer unit, including focusing optics, a broadband optical spectrometer, a spectral camera unit, including an optical spectral filter, image-forming optics , a camera with a matrix photodetector, a shadow device unit, including a radiation source, collimators, a visualizing aperture, a spectral camera, and the device additionally contains a data processing unit connected by data lines to the monitor, an optical emission spectrometer unit, a spectral camera unit, a shadow unit a device configured to receive data from an optical emission spectrometer unit, a spectral camera unit and a shadow device unit, identifying spectral bands of chemiluminescence of excited hydroxyl OH*, molecular vibrational bands of Swan C ₂ , chemiluminescence of excited hydrocarbon CH* and molecular bands of CO and CO2, and also with the possibility of simultaneous display on the monitor of a temperature field, a field of relative heat release rates, a field of combustion completeness coefficients, while the optical emission spectrometer unit is additionally connected by a control communication channel with the data processing unit and is configured to determine the presence of interfering components and transmit a control signal about presence of interfering spectral components in the data processing unit.

The essence of the invention is illustrated by the following figures.

In fig. 1 shows a panoramic multispectral imaging device for studying combustion processes described in the prototype.

In fig. Figure 2 shows the proposed panoramic multispectral imaging device for studying combustion processes.

List of elements:

1 - Focusing optics

2 - Broadband optical spectrometer

3 - Data line

4-Monitor

5 - Optical spectral filter

6 - image-forming optics

7 - Camera with matrix photodetector

8 - Radiation source

9 - Collimator 1

10 - Object of study (flame)

11 - Collimator 2

12 - Imaging diaphragm

13 - Control communication channel

14 - Data processing unit (for collecting data from the temperature field, relative heat release field, combustion efficiency field and further display through the data line on the monitor).

The proposed panoramic multispectral imaging device for studying combustion processes consists of four blocks (optical emission spectrometer block, spectral camera block, shadow data processing device block) and a monitor, rigidly fixed with screws on the frame (not indicated in the figures). A bed is a fixed base, a frame on which individual parts of a device are mounted (S.I. Ozhegov, N.Yu. Shvedova. Ozhegov’s Explanatory Dictionary. 1949-1992).

The optical emission spectrometer block includes focusing optics 1, a broadband optical spectrometer 2, while the optical emission spectrometer block is connected by a transmission line 3 to the data processing unit 14, the data processing block is connected by a data transmission line to the monitor 4, and the optical emission spectrometer block is connected by a data transmission line to the monitor 4. emission spectrometer is additionally connected by a control communication channel 13 with a data processing unit 14. Data transmission line - means that are used in information networks to distribute signals in the desired direction, this can be a coaxial cable, twisted pair, wire, light guide (I.P. Norenkov , V.A. Trudonoshin, Telecommunication technologies and networks, Bauman MSTU, Moscow, 1999, www.translate.academic.ru). A communication channel is a means of one-way data transmission (I.P. Norenkov, V.A. Trudonoshin. Telecommunication technologies and networks. MSTU named after N.E. Bauman. Moscow 1999), while the communication channel can also be made in in the form of coaxial cable, twisted pair, wire or fiber.

In the proposed device, the communication channel is the control channel and serves to transmit a control signal about the presence of interfering spectral components from the broadband optical spectrometer 2 to the data processing unit 14 to prevent incorrect interpretation of the combustion process.

The spectral camera block includes an optical spectral filter 5, image-forming optics 6, a camera with a matrix photodetector 7, and the spectral camera block is connected by a transmission line 3 to the monitor 4. Depending on the experimental conditions, the device may include several spectral camera blocks, for simultaneous recording of several spectral components that cannot be recorded independently using a single spectral camera unit.

The shadow device block includes a radiation source 8, collimators 9 and 11, a visualizing aperture 12, a spectral camera consisting of an optical spectral filter 5 that forms an image of optics 6, a camera with a matrix photodetector 7, and the shadow device block is connected by a data transmission line 3 with monitor 4.

The data processing unit receives data from the optical emission spectrometer unit, the spectral camera unit and the shadow device unit to collect the initial data and convert them into a temperature field, a field of relative heat release rates, a field of combustion completeness coefficients - for simultaneous display via a data line on the monitor.

The device for studying combustion processes operates as follows.

The spectral camera unit records the radiation intensity field of spectral components of the flow, such as excited hydroxyl molecules OH* and hydrocarbon CH*, Swan bands of molecular carbon C ₂ , radiation of CO and CO ₂ molecules, radiation of the high-energy molecular ion N ₂ ⁺ . Isolation of these components in the general spectrum of flame radiation is achieved by using an optical spectral filter 5 (interference spectral-selective filter), tuned to individual flame components, and the spectral-selective sensitivity of the matrix photodetector of the camera 7. The use of a standard visible range camera allows you to simultaneously register up to three components, provided that the emission spectra of the corresponding bands lie in the transmission region of the spectral filters of the matrix photodetectors. Modified cameras with high spatial resolution silicon matrix photodetectors can record up to six spectral components simultaneously. In this case, image-forming optics 6 of a wide spectral range are used. Quartz optics allows you to detect radiation in the range of 300 nm - 1100 nm using a standard silicon matrix photodetector. The resulting spectral images are sent to the data processing unit 14 via data lines 3.

If it is necessary to independently record spectral components located in the spectral sensitivity region of one filter of the matrix photodetector of a spectral camera, several blocks of spectral cameras with spectral-selective filters tuned to individual spectral components of the flame can be used.

The optical emission spectrometer unit records the emission spectrum of the flame in a wide range of wavelengths of optical radiation. Focusing optics 1, for example quartz, operates in a wide range of wavelengths, and allows the broadband optical spectrometer 2 to record the emission spectrum in the spectral region of 200 nm - 1100 nm wavelengths of optical radiation. The resulting emission spectra are supplied to the data processing unit 14 via data line 3.

The shadow device block allows you to register an instantaneous picture of the turbulent structure of the flame as follows - light from the radiation source 8 is converted into a beam of parallel rays using a collimator 9, then the beam of parallel rays passes through the object of study 10, while some of the rays are deflected, refracting at inhomogeneities in the density of the object, the refracted beam of rays is focused by the collimator 11 on the imaging diaphragm 12, allowing one to obtain a shadow picture of the inhomogeneity of the object densities. The resulting shadow pattern is recorded using a spectral camera unit and is sent to data processing unit 14 via communication line 3.

Data processing unit 14 makes it possible to identify a number of characteristic spectral bands, such as chemiluminescence of excited hydroxyl OH*, which characterizes heat release, molecular vibrational bands of Swan C ₂ and chemiluminescence of excited hydrocarbon CH*, allowing to assess the degree of completeness of combustion, bands of the molecular ion N ₂ ⁺ , allowing to assess the presence of catalytic impurities in the flame, molecular bands of CO and CO2, which, as a result of superposition on the spectral bands of OH* and CH*, contribute to a distortion of the interpretation of OH* chemiluminescence emission as a relative rate of heat release.

Additionally, data processing unit 14 allows you to estimate the spectral temperature of the flame from the spectral region of the continuous continuum of soot radiation (article “Measurement of the temperature of a hydrocarbon flame using optical pyrometry methods” / Mosharov V.E., Radchenko V.N., Senyuev I.V. // XV Minsk International Forum on Heat and Mass Transfer, 2016). Isolation of the continuum region, without additional spectral molecular bands, is based on analysis of the flame emission spectrum. The parameters of the continuum region are recorded in the optical-electronic spectrometer unit. In the case when the spectrometer detects the presence of interfering components, a signal is transmitted through the control communication channel indicating that it is not possible to calculate the flame temperature field, which helps prevent incorrect interpretation of the combustion process.

Additionally, the data processing unit makes it possible to correct the field of relative heat release rates obtained from the radiation of excited flame components OH* and/or CH*, by taking into account the overlap of emission bands of interfering components.

The data processing unit, based on two-dimensional spectral analysis, allows you to determine turbulence zones and their intensity. Active turbulent mixing of the flame reduces the intensity of the glow of excited hydroxyl OH* as a result of quenching by active oxygen. The data processing unit corrects the hydroxyl OH* chemiluminescence signal based on an analysis of the turbulence level.

Thus, the data processing unit allows you to generate the following panoramic fields characterizing the combustion process - a field of spectral temperatures, a field of relative heat release rates and a field of combustion completeness coefficients, and display them on monitor 4, which, in turn, allows you to obtain the most complete picture of visualization of the combustion process . In the event of an incorrect assessment of these fields, the optical emission spectrometer transmits a signal via the control communication channel, which will make it impossible to display the corresponding distorted field on the monitor.

A panoramic multispectral visualization device has been created to study combustion processes, which makes it possible to simultaneously obtain temperature fields, relative heat release rates and combustion completeness coefficients.

Claims (1)

Panoramic multispectral imaging device for studying combustion processes, consisting of an optical emission spectrometer unit, including focusing optics, a broadband optical spectrometer, a spectral camera unit, including an optical spectral filter, imaging optics, a camera with a matrix photodetector, a shadow device unit, including a radiation source , collimators, imaging aperture, spectral camera, characterized in that the device additionally contains a data processing unit connected by data transmission lines to the monitor, optical emission spectrometer unit, spectral camera unit, shadow device unit, configured to receive data from the optical emission spectrometer unit, emission spectrometer, spectral chamber unit and shadow device unit, identifying spectral bands of chemiluminescence of excited hydroxyl OH*, molecular vibrational bands of Swan C ₂ , chemiluminescence of excited hydrocarbon CH* and molecular bands of CO and CO ₂ , as well as with the possibility of simultaneous display of temperature fields on the monitor , fields of relative heat release rates, fields of combustion completeness coefficients, while the optical emission spectrometer unit is additionally connected by a control communication channel to the data processing unit and is configured to determine the presence of interfering components and transmit a control signal about the presence of interfering spectral components to the data processing unit.

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