Aircraft pollutant multi-component in-situ measurement system and measurement method

Abstract

The invention provides a multi-component in-situ measurement system and method for aircraft pollutants, and belongs to the technical field of measurement of pollutants discharged by aero-engines. The measurement system comprises a sampling measurement module, a time division multiplexing array laser module, an optical transmission module and a data acquisition and processing module. The measurement method comprises the steps of time division multiplexing signal generation, double-path signal acquisition, signal division in a period, etalon signal wavelength extraction, double-path signal comprehensive modeling and synchronous fitting baseline-free measurement. Multi-component in-situ measurement of the pollutant concentration can be performed at the position of the tail nozzle of the aircraft engine, the measurement system is coupled with a conventional sampling measurement system, the gas pollutant concentration at the sampling position is directly obtained, two measurement results are subjected to interactive verification, additional system errors possibly introduced by the sampling system are avoided, and the measurement accuracy is improved. And a new measurement technical support is provided for aircraft engine pollutant emission optimization and airworthiness certification.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of measuring the exhaust pollutants of an aero-engine, and particularly relates to a system and a method for measuring multiple components of pollutants of an aircraft in situ. BACKGROUND

[0002] The pollutants (such as CO, CO2, NOx, etc.) emitted by an aircraft engine are not only an important source of atmospheric pollution, but their emission characteristics are also the core indicators for performance optimization, airworthiness certification, and compliance verification of emission regulations of a civil aircraft engine. The current airworthiness standard stipulates that the pollutant measurement method mainly uses sampling measurement technology, that is, the exhaust gas is collected by a sampling rake and then transported to a gas analyzer (such as a CO and CO2 analyzer based on the NDIR principle, a NOx analyzer based on the chemical luminescence principle, etc.) through a gas path. Although this technology has been maturely applied, it has significant limitations in the dynamic emission scene of an aero-engine: (1) Systematic errors of sampling measurement are difficult to avoid During the sampling process, the high-temperature exhaust gas may change in composition when being transmitted through the gas path, such as condensation, adsorption, chemical reaction, etc. For example, insufficient heating of the gas path may cause water vapor to condense and adsorb acidic gases (such as NOx), thereby making the measured value lower; the chemical action between the pipe material and the exhaust gas may change the component ratio. Such errors cannot be calibrated by standard gas, and seriously affect the reliability of the emission data.

[0003] (2) Dynamic response lag restricts real-time monitoring When an aircraft engine switches between take-off, cruising, and landing conditions, the exhaust gas composition changes dramatically. However, the sampling measurement is limited by the transmission delay (~s) of the gas path and the response speed of the instrument, and the measurement result often lags behind the actual emission state, which cannot capture the pollutant emission characteristics in the transient operating condition, and may cause key data loss for engine combustion optimization control (such as combustion stability adjustment).

[0004] (3) Multiple component measurement efficiency and cost are high The traditional scheme needs to combine multiple single-component analyzers (such as CO, CO2, and NOx analyzers), which not only has a large equipment volume, but also requires independent calibration (at least once a day) for each instrument, which is complicated to operate. In the multi-condition cycle test of airworthiness certification, frequent calibration and sampling change seriously affect the test efficiency.

[0005] (4) Urgency of in-situ measurement technology for aviation application In-situ measurement technology (such as laser absorption spectroscopy) has proved its advantages in power plant flue gas and automobile exhaust monitoring: direct measurement at the source of emission, avoiding sampling errors; millisecond response speed adapting to dynamic working conditions; simultaneous measurement of multiple components simplifying system structure. However, the high temperature (tailpipe temperature > 800℃), high flow rate and strong vibration environment specific to the aviation field pose severe challenges to the high temperature resistance and optical stability of the in-situ measurement system. Currently, there is no research combining the TDLAS (tunable diode laser absorption spectroscopy) based in-situ measurement system with the sampling system certified by airworthiness, realizing joint measurement and mutual calibration comparison, and it is still not possible to use the above in-situ measurement advantages of TDLAS to provide more accurate measurement results for airworthiness certification.

[0006] In summary, the development of a coupled system with in-situ measurement real-time and sampling measurement can provide real-time comparison and calibration for the sampling measurement system using in-situ measurement, which is the key to breaking through the bottleneck of precise measurement of engine pollutants. This technology not only provides transient data support for engine combustion optimization, but also establishes a new measurement standard suitable for airworthiness certification through interactive verification of the dual system, filling the technical gap in the current field of aviation emission monitoring. SUMMARY

[0007] In view of the problems that the traditional sampling measurement system may have unquantifiable system errors in the measurement of aircraft engine pollutant concentration, and slow response speed and lagged measurement results, the present application provides a kind of aircraft pollutant multi-component in-situ measurement system and measurement method.

[0008] The first aspect of the present application discloses a kind of aircraft pollutant multi-component in-situ measurement system, the measurement system includes: sampling measurement module, time division multiplexing array laser module, optical transmission module and data acquisition processing module; The sampling measurement module includes a sampling rake made of high-temperature alloy, a plurality of sampling holes arranged at equal intervals, a gas mixing device and a gas analyzer; the sampling rake has a gas path and an optical fiber passage respectively; the plurality of sampling holes collect the pollutant gas to be measured at the position of the aircraft engine tail nozzle, and send the gas to the gas mixing device through the gas path for gas mixing and then to the gas analyzer; The time division multiplexing array laser module uses a plurality of lasers, which alternately output optical signals under the control of the data acquisition processing module, and output to the optical transmission module after beam combination; The optical transmission module comprises a high-temperature-resistant beam splitting optical fiber, a collimator and an etalon; the light signal after beam combination is divided into two paths through the high-temperature-resistant beam splitting optical fiber; one path is connected with the collimator through a sampling rake reserved optical fiber path; one path is transported to the etalon to obtain an etalon signal; the collimator is installed on the sampling rake and comprises a transmitting end collimator and a receiving end collimator to form a measurement light path, the measurement light path coincides with the sampling path to obtain a tail nozzle position transmission signal; the high-temperature-resistant beam splitting optical fiber has a temperature resistance greater than or equal to a preset value. The data acquisition and processing module is used for controlling the output of the laser and receiving the tail nozzle position transmission signal and the etalon signal respectively, and then calculating the concentration of the to-be-measured polluted gas.

[0009] Optionally, the time division multiplexing array laser module comprises a multi-channel signal generator, a plurality of lasers and a fiber beam combiner; the number of channels of the multi-channel signal generator matches the number of lasers; Under the control of the data acquisition and processing module, the multi-channel signal generator sends a time division multiplexing signal to each laser controller to make each laser output light signals alternately to correspond to different absorption spectral lines of different to-be-measured polluted gases; The fiber beam combiner combines the output light signals of the lasers into one beam and outputs to the optical transmission module.

[0010] Optionally, the data acquisition and processing module comprises two detectors, a data acquisition card and an upper computer; The two detectors receive the tail nozzle position transmission signal and the etalon signal respectively, and send the converted electrical signals to the data acquisition card for analog-digital conversion, and then send the digital signals after analog-digital conversion to the upper computer; The upper computer generates a driving signal based on the type of the to-be-measured polluted gas analyzed by the gas analyzer to control the time division multiplexing array laser module to output light signals alternately through time division multiplexing, and calculates the concentration of the to-be-measured polluted gas through a baseline-free time division multiplexing method according to the digital signals sent by the data acquisition card.

[0011] Optionally, a heating device is additionally arranged outside the gas path in the sampling and measurement module, so that the temperature of the gas path pipeline is always higher than the dew point temperature of the to-be-measured polluted gas.

[0012] The second aspect of the present application discloses a method for measuring multiple components of aircraft pollutants in situ, which is realized by a system for measuring multiple components of aircraft pollutants in situ, and comprises the following steps: S1, the data acquisition processing module generates a time division multiplexing signal to drive multiple lasers to alternately output optical signals, and after being combined, the optical signals are divided into two paths through a high-temperature-resistant splitting optical fiber; one path is connected with a collimator through a sampling rake reserved optical fiber path; the other path is transported to an etalon to obtain an etalon signal; the collimator is installed on the sampling rake and includes a transmitting end collimator and a receiving end collimator to form a measurement light path, and the measurement light path coincides with a sampling path to obtain a tail nozzle position transmission signal; S2, the data acquisition processing module synchronously receives the tail nozzle position transmission signal and the etalon signal ; S3, the data acquisition processing module divides the tail nozzle position transmission signal and the etalon signal in a period to divide effective transmission signals and effective etalon signals of each laser in a period; S4, the data acquisition processing module extracts an interference peak position and assigns a frequency value to the effective etalon signal of each laser; S5, the data acquisition processing module establishes a frequency model and a transmission light intensity model for each laser; S6, model parameters of the frequency model are fitted according to the frequency value obtained in step S4, and then model parameters of the transmission light intensity model are fitted by using the effective transmission signal of each laser to obtain a spectral line area c 0 to calculate the concentration of the to-be-measured contaminated gas.

[0013] Optionally, in step S1, the data acquisition processing module generates a time division multiplexing signal for S lasers, and a total period is T=ST0, and in each sub-period T0, the signal expression U(t) of the i-th channel is: wherein the signal amplitude U0 and the bias U1 make the wavelength scanning range of the laser cover the target absorption spectrum line, and the minimum value is lower than the threshold current to generate a non-excited segment background signal; t is a time variable.

[0014] Optionally, in step S3, the calculation formulae of the effective transmission signal and the effective etalon signal of each laser are: wherein, is the effective transmission signal of the laser i in the i-th sub-period; is the effective etalon signal of the laser i in the i-th sub-period; is the effective transmission signal of the laser i that is excited when being greater than the threshold current; is the background signal average value of the laser i when being lower than the threshold current and not being excited; is the effective etalon signal of the laser i that has been excited; is the background signal average value of the etalon signal that is not excited.

[0015] Optionally, step S4 specifically comprises: Obtaining median position according to effective transmission signal of each laser t peak ; wherein, In the formula, and is the effective transmission signal of laser i Peak position of two absorption peaks in the effective transmission signal; Peak searching is performed on the effective etalon signal of each laser to obtain all interference peak positions; the formula for frequency assignment of each interference peak position is: Wherein, is the frequency value of the jth interference peak; is the free spectral range of the etalon; t j is the jth interference peak position; j is a positive integer value.

[0016] Optionally, in step S5, the expressions of the frequency model and the transmission light intensity model are: Wherein, is the frequency model of laser i; a 0, a 1,…, a 2M is the Fourier series expansion coefficient of the frequency model, and is the model parameter of the frequency model; M is the cutoff frequency of the frequency model; T 0 is the period of the driving signal of each laser; is the transmission light intensity model of laser i; is the incident light intensity model of laser i; b 0, b 1,…, b 2n is the Fourier series expansion coefficient of the incident light intensity model; N is the cutoff frequency of the incident light intensity model; is the gas absorption spectral line characteristic corresponding to laser i; c 0 is the spectral line area, is the Voigt line function, c 1 and c2 is the Gaussian and Lorentzian broadening.

[0017] Optionally, the model parameter fitting formula of the frequency model is: wherein, is the jth interference peak position of the laser i t j at the frequency model calculated frequency value; is the frequency value of the jth interference peak directly extracted from the fiducial signal; the calculation formula of the spectral line area c 0 is: wherein, is the effective transmission signal of the laser i.

[0018] In summary, the scheme proposed by the present application has the following technical effects: The laser absorption spectrum-based aircraft pollutant multi-component in-situ measurement system of the present application has the following advantages: compared with the existing sampling measurement technology, the system can directly measure the in-situ real-time concentration of multi-component pollutants at the tail nozzle of the aircraft engine, solve the problems of system error and response lag that may be introduced by the sampling system in the gas flow, and provide real-time calibration for the existing sampling measurement system, thereby providing a more accurate and powerful measurement method for the optimization and improvement of aircraft engine emission performance, airworthiness certification, and emission compliance.

[0019] The aircraft pollutant multi-component in-situ measurement method (also referred to as the baseline-free time division multiplexing measurement method of sinusoidal scanning) of the present application can be combined with the multi-component in-situ measurement system of the present application to provide measurement method support for the system. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0021] Figure 1 The figure is a schematic diagram of the laser absorption spectrum-based aircraft pollutant multi-component in-situ measurement system of the coupling sampling measurement of the embodiment of the present application. Figure 2 Figure 1 is a flow chart of a sinusoidal scanning baseline-free time-division multiplexing measurement method according to an embodiment of the present application; Figure 3 is a diagram showing the division of a period of (a) a transmission signal and (b) a standard signal according to an embodiment of the present application; Figure 4 is a diagram showing the peak searching of a standard signal of two lasers according to an embodiment of the present application; Figure 5 is a diagram showing the fitting results of a frequency-time model of two lasers according to an embodiment of the present application; Figure 6 is a diagram showing the fitting results of a transmission light intensity model of two lasers according to an embodiment of the present application. DETAILED DESCRIPTION

[0022] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0023] One of the main objectives of the present application is to provide a laser absorption spectrum based in-situ measurement system for multiple components of aircraft engine pollutants coupled with sampling measurement. By measuring the gas before sampling in-situ, the system error in the sampling process can be avoided, real-time and rapid response to the changes of pollutant components can be achieved, and the calibration function of the sampling measurement system can also be achieved. The principle of absorption spectrum also provides the ability of multiple component measurement and periodic calibration-free, which ensures the stability of the measurement results.

[0024] Another main objective of the present application is to provide a baseline-free time-division multiplexing measurement method based on the in-situ measurement system for multiple components of aircraft engine pollutants. The baseline-free measurement is achieved by sinusoidal scanning, and the simultaneous measurement of multiple components is achieved by time-division multiplexing. The collected data can be processed in real time to obtain the change curve of the concentration of multiple components of pollutants over time.

[0025] The objective of the present application is achieved by the following technical solutions: The present application discloses a laser absorption spectrum based in-situ measurement system for multiple components of aircraft pollutants coupled with sampling measurement, which mainly comprises a sampling measurement module, a time-division multiplexing array laser module, an optical transmission module and a data acquisition and processing module.

[0026] The sampling measurement module is a conventional method for measuring pollutants of an aircraft engine, and various concentrations of pollutants to be measured in tail gas are obtained according to airworthiness regulations; the sampling measurement module includes a sampling rake, a sampling hole, an air path, a gas extraction and mixing device (i.e., a gas pump and a mixer), a gas analyzer and the like; the sampling rake is made of a high-temperature alloy and needs to withstand a relatively high total temperature; in addition to the air path, an optical fiber channel is arranged inside the sampling rake to provide space for optical fiber to transmit optical signals; the sampling holes are arranged in one row at equal intervals, and the number of the sampling holes is more than 5; the air path needs to be heated to prevent water vapor from condensing; and the gas pump and the mixer mix and deliver the gas obtained from the sampling holes to the gas analyzer.

[0027] The time division multiplexing array laser module includes a multi-channel signal generator, a plurality of lasers and a matching controller, and a fiber combiner; the number of channels of the multi-channel signal generator matches the number of lasers, and the multi-channel signal generator sends a time division multiplexing signal to each laser controller under the control of a host computer, so that each laser alternately outputs an optical signal, which is used for multi-spectrum simultaneous measurement of corresponding spectral lines of each laser; the parameters and the number of the lasers are determined according to the types of pollutants to be measured and a measurement scheme; and the fiber combiner combines optical signals of the lasers into one beam and delivers the beam to a measurement position.

[0028] The optical transmission module includes high-temperature-resistant optical fibers, a collimator and an etalon; time division multiplexing optical signals generated by the plurality of lasers are divided into two paths through high-temperature-resistant split optical fibers, one path is delivered to a tail nozzle measurement position to connect the collimator to complete absorption spectrum measurement, and the other path is delivered to the etalon to complete wavelength signal measurement; the collimator is installed on the sampling rake of the sampling measurement module and includes a transmitting end and a receiving end, so that a measurement light path is just at a sampling hole position to measure parameters of gas before sampling.

[0029] The data acquisition and processing module includes a detector, a data acquisition card and a host computer; the detector has two parts, which respectively receive optical signals of the etalon and the receiving end collimator in the optical transmission module and convert the optical signals into electrical signals; the data acquisition card collects the electrical signals and converts the electrical signals into digital signals to input the host computer; the host computer controls the entire measurement process, controls the multi-channel signal generator of the time division multiplexing array laser module, and is used for completing data processing.

[0030] Another aspect of the present application discloses a baseline-free time division multiplexing measurement method of sinusoidal scanning, please refer to Figure 2 , which mainly includes the following steps: (1) Step 1 - Time division multiplexing signal generation: A host computer is used to control the signal generator to output a sinusoidal time division multiplexing signal; for S lasers, the total period is T=ST0, and in each period, the signal of the i th channel is: Wherein, the amplitude U0 and bias U1 need to be determined according to the actual output characteristics of each laser, so that the light signal intensity and the wavelength scanning range are large enough, and the minimum value of the signal is below the threshold current of the laser.

[0031] (2) Step 2 - Dual-channel signal acquisition: The two detectors of the data acquisition and processing module respectively acquire the tail nozzle position transmission signal and the etalon signal .

[0032] (3) Step 3 - Signal division in a cycle: For and , the effective light signal of each laser is divided in each cycle, and for the i-th laser, it is and ; the cycle division is characterized by the unexcited segment, which is a constant light intensity signal lasting for a period of time at the junction of the signals of the lasers, representing the background when the laser is not excited and ; taking the unexcited segment as the boundary, the effective signal of each laser that has been excited can be obtained and , but the average value of the background signal below the threshold needs to be deducted: Wherein, is the effective transmission signal of laser i in the i-th sub-cycle; is the effective etalon signal of laser i in the i-th sub-cycle; is the effective transmission signal of laser i above the threshold current; is the average value of the background signal of laser i below the threshold current; is the effective etalon signal of laser i that has been excited; is the average value of the background signal of the etalon signal that is not excited.

[0033] (4) Step 4 - Extraction of etalon signal wavelength: For the etalon signal of each laser , the peak position of the interference peak is obtained by peak searching , and the frequency is assigned ; first, the median position is obtained from the transmission signal of each laser , where , and and are the peak positions of the two absorption peaks in , and the frequency assignment is: wherein is the free spectral range of the etalon.

[0034] (5) Step 5 - dual-path signal comprehensive modeling: For each laser, a frequency model and a transmitted light intensity model are established. Wherein, The function form of The function form of wherein, , M and N are the cutoff frequencies of the two models, which are determined according to the actual measurement accuracy; is a Voigt line function, and c1 and c2 are Gaussian and Lorentz broadening.

[0035] (6) Step 6 - synchronous fitting baseline-free measurement: For each laser, the frequency point of step 4 is used to fit model parameters: Then, the data of each laser is used to fit model parameters to obtain the spectral line area c0: According to the general laser absorption spectrum principle, the concentration of the measured gas can be calculated from the spectral line area c0.

[0036] The schematic diagram of the in-situ multi-component measurement system of the aircraft pollutant based on the laser absorption spectrum of the coupling sampling measurement according to an embodiment of the application is shown in Figure 1 (a), which comprises a sampling measurement module, a time division multiplexing array laser module 2, an optical transmission module and a data acquisition and processing module.

[0037] The sampling and measurement module employs conventional methods for measuring aircraft engine pollutants, acquiring the concentrations of various analyte pollutants in the exhaust gas according to airworthiness regulations. It includes a sampling rake 101, sampling holes 102, an air pump and mixer 103, a gas analyzer 104, and corresponding gas paths. In this embodiment, the sampling rake 101 is made of GH3039 high-temperature alloy, capable of long-term operation at 850℃, making it suitable for aircraft exhaust gas. The sampling rake internally contains both gas paths and fiber optic pathways for transporting the sampled gas and providing space for the fiber optic cable to transmit optical signals. The sampling holes 102 are arranged in a row at equal intervals, with a total length of 60cm. The air pump and mixer 103 mixes the gases from the 12 sampling holes and delivers them to the gas analyzer 104. The gas paths are heated to maintain a temperature between 150℃ and 180℃ to prevent water vapor condensation and adsorption of the analyte gas.

[0038] The detailed structure of the time-division multiplexed array laser module is as follows: Figure 1 As shown in (b), the system includes a 201 multi-channel signal generator, 202 multiple lasers and their corresponding controllers, and a 203 fiber optic combiner. In this embodiment, two lasers (202) are used for demonstration, with wavelengths of 1343nm and 1392nm, for temperature and H2O concentration measurement. The coupling principle of the other components and lasers is exactly the same. The 201 multi-channel signal generator has two channels, matching the number of lasers. Under the control of the host computer, it sends time-division multiplexing signals to the two laser controllers to cause them to output alternately. The 203 near-infrared fiber optic combiner combines the optical signals from each laser into a single beam.

[0039] The optical transmission module includes optical components such as a standard 301, a collimator 302, and high-temperature resistant optical fiber. In this embodiment, the combined optical signal from the time-division multiplexed array laser module is split into two paths via a high-temperature resistant splitting optical fiber. One path connects to the collimator 302 via a reserved optical fiber path in the sampling rake 101, and the other path transmits the optical signal to the standard 301. There are two collimators 302, which are installed on the sampling rake 101. Each collimator includes a transmitter and a receiver, both assembled with a high-temperature alloy shell and a quartz lens. The resulting measurement optical path is located at the sampling aperture to measure the gas parameters before sampling. The free spectral range of the standard 301 is 1.5 GHz.

[0040] The data acquisition and processing module includes a detector 401, a data acquisition card 402, and a host computer 403. In this embodiment, two InGaSb detectors are selected for the detector 401, which respectively receive optical signals from the etalon 301 and the collimator 302 at the receiving end, and convert them into electrical signals; the data acquisition card 402 acquires the electrical signals, converts them into digital signals, and inputs them into the host computer 403; the host computer 403 controls the entire measurement process and completes data processing.

[0041] The sinusoidal scanning baseline-free time division multiplexing measurement method of one embodiment of the application is verified in a 800 DEG C pipe furnace, and mainly includes the following steps: (1) Step 1 - Time division multiplexing signal generation: For two lasers, a host computer is used to control a signal generator to output a sinusoidal time division multiplexing signal. The total period is T = 2T0, and T0 = 10 ms. In each period, the input signal of the 1392 nm laser controller is: The input signal of the 1343 nm laser controller is: (2) Step 2 - Dual-channel signal acquisition: The two detectors of the data acquisition and processing module respectively acquire the tail nozzle position transmission signal and the etalon signal .

[0042] (3) Step 3 - Signal division in a period: For and , the effective light signals of the two lasers and the unexcited segments are divided in each period, as shown in FIG. 3. The unexcited segments are used as background and ; the effective signals excited and need to deduct the average value of the background signal below the threshold: (4) Step 4 - Etalon signal extraction wavelength: For the etalon signals of the two lasers , the peak positions are obtained by searching for peaks , as shown in FIG. 4, and the frequency values are assigned . First, the midpoint of the two absorption peak peak values is obtained as the median position according to the transmission signals of the two lasers , and the frequency assignment is: (5) Step 5 - Dual-channel signal comprehensive modeling: For the two lasers, the frequency model and the transmission light intensity model are established. Among them, the function form is: The function form of is: wherein, , Both models are 3 times frequency cutoff; is Voigt function, c1 and c2 are Gaussian and Lorentz broadening.

[0043] (6) Step 6 - Synchronous fitting of baseline-free measurement: For two lasers, the frequency points of step 4 are used to fit Model parameters, the results are shown in Figure 5: Then, using the data of each laser , the model parameters are fitted , and the results are shown in Figure 6: The integral areas c0 of two spectral lines are obtained as follows: 1392nm: 0.01355, 1343nm: 0.00602.

[0044] Then, according to the calculation, the temperature is 796℃, and the H2O concentration is 3.3%, which is close to the actual temperature of 800℃, verifying the effectiveness of the measurement method.

[0045] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit it. Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can still be modified, or some or all of the technical features can be replaced by equivalents, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An in-situ measurement system for multiple components of aircraft pollutants, characterized in that, The measurement system includes: a sampling measurement module, a time-division multiplexed array laser module, an optical transmission module, and a data acquisition and processing module; The sampling and measurement module includes a sampling rake made of high-temperature alloy, multiple sampling holes arranged at equal intervals, a gas mixing device, and a gas analyzer. The sampling rake has gas passages and optical fiber passages inside. The multiple sampling holes collect the pollutant gas to be tested from the tail nozzle of the aircraft engine and send it to the gas mixing device through the gas passage for gas mixing before sending it to the gas analyzer. The time-division multiplexing array laser module uses multiple lasers, which alternately output optical signals in a time-division multiplexing manner under the control of the data acquisition and processing module, and then output them to the optical transmission module after beam combining; The optical transmission module includes a high-temperature resistant splitting fiber, a collimator, and an etalon. The combined optical signal is split into two paths by the high-temperature resistant splitting fiber. One path is connected to the collimator via a pre-reserved fiber path on the sampling rake. The other path is transmitted to the etalon to obtain the etalon signal. The collimator is mounted on the sampling rake and includes a transmitting collimator and a receiving collimator to form a measurement optical path. The measurement optical path coincides with the sampling path to obtain the transmission signal at the tail nozzle position. The high-temperature resistant splitting fiber has a temperature tolerance greater than or equal to a preset value. The data acquisition and processing module is used to control the laser output and receive the transmission signal and etalon signal at the tail nozzle position, respectively, and then calculate the concentration of the pollutant gas to be measured.

2. The in-situ measurement system for multiple components of aircraft pollutants according to claim 1, characterized in that, The time-division multiplexed array laser module includes a multi-channel signal generator, multiple lasers, and an fiber combiner; the number of channels in the multi-channel signal generator matches the number of lasers. Under the control of the data acquisition and processing module, the multi-channel signal generator sends a time-division multiplexed signal to each laser controller, causing each laser to alternately output optical signals to correspond to the absorption spectrum of different pollutants to be tested. The fiber optic combiner combines the output optical signals of each laser into a single beam, which is then output to the optical transmission module.

3. The in-situ measurement system for multiple components of aircraft pollutants according to claim 1, characterized in that, The data acquisition and processing module includes two detectors, a data acquisition card, and a host computer; The two detectors receive the transmitted signal from the tail nozzle position and the etalon signal respectively, convert them into electrical signals and send them to the data acquisition card for analog-to-digital conversion, and then send the digital signal after analog-to-digital conversion to the host computer. The host computer generates a drive signal based on the type of pollutant gas to be measured obtained from the gas analyzer, and controls the time-division multiplexing array laser module to alternately output optical signals in a time-division multiplexing mode. Based on the digital signal sent by the data acquisition card, the concentration of the pollutant gas to be measured is calculated by the baseline-free time-division multiplexing method.

4. The in-situ measurement system for multiple components of aircraft pollutants according to claim 1, characterized in that, An external heating device is added to the gas path in the sampling and measurement module to ensure that the temperature of the gas path is always higher than the dew point temperature of the pollutant gas being measured.

5. A method for in-situ measurement of multiple components of aircraft pollutants, characterized in that, The method is implemented using the in-situ measurement system for multi-component aircraft pollutants as described in any one of claims 1-4, and the method includes: S1, the data acquisition and processing module generates a time-division multiplexed signal to drive multiple lasers to alternately output optical signals. After beam combining, the signals are split into two paths via a high-temperature resistant splitting fiber. One path connects to the collimator via a pre-reserved fiber optic path on the sampling rake; the other path is sent to the etalon to obtain the etalon signal. The collimator, mounted on the sampling rake, includes a transmitter collimator and a receiver collimator to form a measurement optical path. The measurement optical path coincides with the sampling path to obtain the tail nozzle position transmission signal. S2, the data acquisition and processing module synchronously receives the tail nozzle position transmission signal. and standard etalon signal S3, the data acquisition and processing module processes the transmitted signals at the tail nozzle position. and standard etalon signal The signal is divided within a period to separate the effective transmission signal and effective marker signal of each laser within the period; S4, the data acquisition and processing module extracts the interference peak position and assigns frequency values ​​to the effective marker signal of each laser; S5, the data acquisition and processing module establishes a frequency model and a transmission intensity model for each laser; S6, the model parameters of the frequency model are fitted based on the frequency values ​​obtained in step S4, and then the model parameters of the transmission intensity model are fitted using the effective transmission signal of each laser to obtain the spectral area. c 0, to calculate the concentration of the pollutant gas to be measured.

6. The method according to claim 5, characterized in that, In step S1, the data acquisition and processing module for S Each laser generates a time-division multiplexed signal with a total period of [missing information]. T = ST 0, in each sub-cycle T Within 0, the signal expression of the i-th channel. U ( t )for: Among them, signal amplitude U 0 and bias U 1. Ensure that the laser wavelength scanning range covers the target absorption spectrum, and that the minimum value is below the threshold current to generate the background signal of the unexcited segment; t It is a time variable.

7. The method according to claim 5, characterized in that, In step S3, the formulas for calculating the effective transmission signal and effective marker signal of each laser are as follows: in, Let be the effective transmission signal of laser i during the i-th sub-cycle; Let be the effective datum signal of laser i during the i-th sub-cycle; The effective transmission signal of the laser i is generated when the current is greater than the threshold current. This represents the average background signal when laser i is not excited due to a current below the threshold. The effective datum signal excited by laser i; This represents the average value of the unexcited background signal corresponding to the indicator signal.

8. The method according to claim 5, characterized in that, Step S4 specifically includes: The median position is obtained based on the effective transmission signal of each laser. t peak ;in, In the formula, and There is an effective transmission signal from laser i. The peak positions of the two absorption peaks; Peak finding is performed on the effective datum signal of each laser to obtain the positions of all interference peaks; the formula for assigning frequency values ​​to each interference peak position is as follows: in, Let j be the frequency value of the j-th interference peak; It is the free spectral region of the etalon; t j Let j be the position of the j-th interference peak; j is a positive integer value.

9. The method according to claim 5, characterized in that, In step S5, the expressions for the frequency model and the transmitted light intensity model are as follows: in, Here is the frequency model for laser i; a 0, a 1,…, a 2M represents the Fourier series expansion coefficients of the frequency model, and represents the model parameters of the frequency model; M This is the cutoff harmonic of the frequency model; T 0 represents the drive signal cycle for each laser; Here is the transmitted light intensity model for laser i; Let be the incident light intensity model for laser i; b 0, b 1,…, b 2n These are the Fourier series expansion coefficients of the incident light intensity model; N This is the cutoff frequency of the incident light intensity model; The gas absorption spectral characteristics corresponding to laser i; c 0 represents the spectral area. It is the Voigt linear function. c 1 and c 2 is the Gaussian and Lorentz extension.

10. The method according to claim 9, characterized in that, The formula for fitting the model parameters of the frequency model is: in, The position of the j-th interference peak of laser i t j At that point, by frequency model The calculated frequency value; The frequency value of the j-th interference peak is extracted directly from the indicator signal; Spectral line area c The formula for calculating 0 is: in, This represents the effective transmission signal of laser i.

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