Method for eliminating fluorescence interference in solid fuel OH-PLIF measurement

Abstract

The invention discloses a method for eliminating fluorescence interference in solid fuel OH-PLIF measurement, and belongs to the field of solid fuel combustion parameter measurement. According to a mixed fluorescence signal containing OH fluorescence and polycyclic aromatic hydrocarbon fluorescence, a single polycyclic aromatic hydrocarbon fluorescence signal and a correction coefficient, the fluorescence interference in the solid fuel OH-PLIF measurement can be eliminated; and removing the interference of polycyclic aromatic hydrocarbon in the OH signal in the region in which OH fluorescence and polycyclic aromatic hydrocarbon fluorescence cannot be distinguished. The method established by the invention is suitable for the combustion process of solid fuel (coal and biomass), the workload of OH fluorescence signal measurement is reduced, and the detection accuracy of OH fluorescence signals is improved.

Description

Technical Field

[0001] The invention belongs to the field of solid fuel combustion parameter measurement and relates to a method for eliminating fluorescence interference in solid fuel OH-PLIF measurement. Background Art

[0002] At present, the main means of utilizing traditional fossil energy is direct combustion, but due to the characteristics of fuel and technical means, it will cause a series of environmental problems. Take coal as an example. The structure of coal is extremely complex. Some of the sulfur and nitrogen components in it will be oxidized to form sulfur oxides (SO X ) and nitrogen oxides (NO X ), the above-mentioned pollutants will cause serious problems such as acid rain, photochemical smog and haze. In addition to the environmental problems that directly harm production and life, the large-scale use of fossil energy has caused the carbon elements originally stored in the fuel to be converted into carbon dioxide (CO2) and discharged into the atmosphere on a large scale. There is strong scientific evidence that the release of CO2 is primarily responsible for climate change. Biomass is a renewable energy source. Compared with coal, it has extremely similar physical and chemical properties. There are also a series of problems such as pollutant emissions during its utilization. In terms of solid fuel utilization, the emission of pollutants and carbon emissions during the combustion process can be minimized by improving combustion technology. To improve combustion technology, it is necessary to understand the nature of combustion and master the mechanism of combustion phenomena. Planar laser induced fluorescence (PLIF) technology can achieve time and space resolution and qualitative and quantitative measurement of trace components. It has outstanding advantages in constructing the kinetics of combustion chemical reactions and is of great help in understanding the combustion mechanism.

[0003] OH (hydroxyl) is a highly active, sensitive and selective free radical, which is formed in the high temperature region of most hydrocarbon fuel flames. OH-PLIF is often used to reveal information on flame structure, combustion stage, combustion efficiency, reaction mechanism, etc. OH-PLIF usually selects electron transitions in A 2 Σ+←X 2 The OH group of II is the object of measurement, and its absorption spectrum range is between 280nm-290nm. During the combustion of solid fuels, there will be the release of polycyclic aromatic hydrocarbons, whose absorption and emission spectrum ranges are relatively wide, basically covering the absorption and emission spectra of OH groups, which brings great interference to the detection of OH-PLIF during the combustion of solid fuels. Eliminating the interference of polycyclic aromatic hydrocarbons fluorescence signals is an urgent problem to be solved in the OH-PLIF measurement during the combustion of solid fuels. Summary of the invention

[0004] The present invention provides a method for eliminating fluorescence interference in solid fuel OH-PLIF measurement, which can distinguish the PAH fluorescence interference area, eliminate the interference of PAH fluorescence in OH fluorescence, reduce the workload of specific implementation work, and greatly improve the accuracy of OH group measurement during solid fuel combustion.

[0005] The present invention provides the following technical solutions:

[0006] The method for eliminating fluorescence interference in solid fuel OH-PLIF measurement comprises the following steps:

[0007] Step 1, simultaneously obtaining the distribution of mixed fluorescence signals including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence and the distribution of single polycyclic aromatic hydrocarbon fluorescence signals, dividing the combustion stage of the solid fuel according to the distribution of mixed fluorescence signals including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence, and obtaining the areas where only OH fluorescence signals exist in different combustion stages;

[0008] Step 2: For the area where OH fluorescence and PAH fluorescence cannot be distinguished, the correction coefficients of different excitation wavelengths and different detection wavelengths are calculated;

[0009] Step 3: From the mixed fluorescence signal distribution including OH fluorescence and PAH fluorescence, the corresponding correction coefficient is deducted from the single PAH fluorescence signal distribution to obtain the OH fluorescence signal distribution.

[0010] Preferably, in step 1, the mixed fluorescence signal distribution including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence and the single polycyclic aromatic hydrocarbon fluorescence signal distribution are simultaneously obtained, the combustion stage of the solid fuel is divided according to the mixed fluorescence signal distribution including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence, and the area of ​​the single OH fluorescence signal in different combustion stages is obtained, specifically:

[0011] Method 1: Utilizing the broadband absorption characteristics of PAHs compared to OH, the resonant excitation line of OH and the non-resonant excitation line of OH are selected to respectively excite the solid fuel combustion field;

[0012] The specific measurement system of the method 1 in step 1 specifically includes: a laser system, a sheet beam shaping system, a signal detection system, a timing synchronization system and a computer;

[0013] There are two laser systems, namely laser system L1 and laser system L2, with a laser pulse width of less than 10ns. The excitation wavelength of laser system L1 is OH A 2 X+(0, 0)←X 2 The resonant excitation line of the Π(0, 1) spectral band has a wavelength of 282.95 nm (not limited to 282.95 nm). The excitation wavelength of the laser system L2 is the non-resonant excitation line of OH, with a wavelength of 282.52 nm (not limited to 282.52 nm);

[0014] The sheet beam shaping system is mainly composed of a cylindrical plano-concave lens and a spherical biconvex lens;

[0015] There are two signal detection systems, namely signal detection system C1 and signal detection system C2. The two signal detection systems have the same composition and settings, consisting of a filter unit, a CCD camera, and an image intensifier. The exposure time of the image intensifier is set to 200ns. The filter unit is mainly composed of a bandpass filter with a transmission wavelength of 305-315nm.

[0016] The timing synchronization system is used to control the exposure time and sampling synchronization of the signal detection system. The laser flash delay time is 0μs, the Q-switching delay time is 455μs, the CDD camera delay time is 362μs, and the image intensifier delay time is set to 455.02650μs;

[0017] The computer calculates the accurate OH fluorescence signal by acquiring the mixed fluorescence signal including OH fluorescence and PAH fluorescence, the individual PAH fluorescence signal and the correction coefficient;

[0018] Step 1-1, use the laser system L1 to excite the solid fuel combustion field, and the signal detection system C1 is used to detect the fluorescence signal. The sampling time of the signal detection system C1 is synchronized with the laser system L1. The fluorescence signal is a mixed fluorescence signal distribution S including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence. C1 (x, y);

[0019] Step 1-2: Use the laser system L2 to excite the solid fuel combustion field, and the signal detection system C2 to detect the fluorescence signal, which is the distribution S of the individual PAH fluorescence signal. C2 (x, y);

[0020] Step 1-3, dividing the combustion stage of the solid fuel into a de-volatilization stage, a volatile combustion stage, and a coke combustion stage according to the mixed fluorescence signal including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence;

[0021] Step 1-4, comparing the image of the mixed fluorescence signal containing OH fluorescence and PAH fluorescence with the image of the single PAH fluorescence signal at the same combustion stage, if there is a mixed fluorescence signal of OH and PAHs in the region but no single PAH fluorescence signal, it can be determined that only OH fluorescence signal exists in the region;

[0022] Step 1-5: In the region, there are both mixed fluorescence signals of OH and PAHs and fluorescence signals of individual PAHs, which is a region where OH fluorescence and PAH fluorescence cannot be distinguished;

[0023] Method 2: Using the broadband absorption characteristics of PAHs compared to OH, the detection wavelength of the mixed fluorescence signal including OH fluorescence and PAH fluorescence, and the detection wavelength of only PAH fluorescence are selected to detect the fluorescence signal excited by the laser system;

[0024] The specific measurement system in the second method in step 1 is different from that in the first method in step (1) as follows:

[0025] There is one laser system, which is laser system L1. The laser pulse width is less than 10ns. The excitation wavelength of laser system L1 is OH A 2 X+(0, 0)←X 2 The resonance excitation line of the Π(0, 1) spectral band has a wavelength of 282.95nm (not limited to 282.95nm);

[0026] There are two signal detection systems, namely signal detection system C1 and signal detection system C2. Both signal detection system C1 and signal detection system C2 are composed of a filter unit, a CCD camera, and an image intensifier. The exposure time of the image intensifier is set to 200ns. The transmission wavelength of the filter unit in signal detection system 1 is 305-315nm, which can pass a mixed fluorescence signal including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence. The transmission wavelength of the filter unit in signal detection system 2 is 425-435nm, which can only pass polycyclic aromatic hydrocarbon fluorescence signals.

[0027] Step 1-1, use the laser system L1 to excite the solid fuel combustion field, and the signal detection system C1 and the signal detection system C2 are used to detect the fluorescence signal. The sampling time of the signal detection system C1 is synchronized with the laser system L1. The fluorescence signal is a mixed fluorescence signal distribution S including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence. C1 (x, y), the sampling time of the signal detection system C2 is synchronized with the laser system L1, and the fluorescence signal is the distribution S of the fluorescence signal of individual PAHs C2 (x, y);

[0028] Step 1-2, dividing the combustion stage of the solid fuel into a de-volatilization stage, a volatile combustion stage, and a coke combustion stage according to a mixed fluorescence signal including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence;

[0029] Step 1-3, comparing the image of the mixed fluorescence signal containing OH fluorescence and PAH fluorescence with the image of the single PAH fluorescence signal at the same combustion stage, if the mixed fluorescence signal containing OH fluorescence and PAH fluorescence exists in the region but the single PAH fluorescence signal does not exist, it can be determined that only OH fluorescence signal exists in the region;

[0030] Step 1-4: In the region, there are both mixed fluorescence signals of OH and PAHs and single PAH fluorescence signals, which is a region where OH fluorescence and PAH fluorescence cannot be distinguished;

[0031] Preferably, in step 2, for the area where OH fluorescence and PAH fluorescence cannot be distinguished, the correction coefficients for different excitation wavelengths and the correction coefficients for different detection wavelengths are calculated, including:

[0032] Method 1: For the measurement of method 1 in step 1, due to the difference in excitation wavelengths when measuring with a dual laser system, it is necessary to calculate the correction coefficients for different excitation wavelengths;

[0033] The difference between the measurement system of method 1 in step 2 and method 1 in step 1 is:

[0034] There are two signal detection systems, namely signal detection system C1 and signal detection system C2. Both signal detection system C1 and signal detection system C2 are composed of a filter unit, a CCD camera, and an image intensifier. The exposure time of the image intensifier is set to 200ns, and the transmission wavelength of the filter unit is 425-435nm, which can only detect the fluorescence signal of polycyclic aromatic hydrocarbons;

[0035] Step 2-1: The sampling time of the signal detection system C1 is synchronized with the laser system L1 to obtain the fluorescence signal distribution S' of individual PAHs. C1 (x, y), the sampling time of the signal detection system C2 is synchronized with the laser system L2 to obtain the fluorescence signal distribution S' of individual PAHs C2 (x, y), a delay time is set between the laser system L1 and the laser system L2, and the delay time is greater than the minimum value of the OH fluorescence lifetime;

[0036] Step 2-2, Correction coefficient k=S' for different excitation wavelengths C1 (x, y) / S' C2 (x, y);

[0037] Method 2: For the measurement of method 2 in step 1, due to the difference in detection wavelengths when measuring with a dual-signal detection system, it is necessary to calculate the correction coefficients for different detection wavelengths;

[0038] The specific measurement system in the second method in step 2 is different from that in the second method in step 1 in that:

[0039] There is one laser system, which is the laser system L1. The laser pulse width is less than 10 ns. The excitation wavelength of the laser system L1 is the OH non-resonance excitation line, and the wavelength is 282.52 nm (not limited to 282.52 nm).

[0040] Step 2-1: The sampling time of the signal detection system C1 is synchronized with the laser system L1 to obtain the fluorescence signal distribution S' of individual PAHs. C1 (x, y), the sampling time of the signal detection system C2 is synchronized with the laser system L1 to obtain the fluorescence signal distribution S' of individual PAHs C2 (x, y);

[0041] Step 2-2, Correction coefficient k = S' for different detection wavelengths C1 (x, y) / S' C2 (x, y).

[0042] Preferably, in step 3, the corresponding correction coefficient is deducted from the mixed fluorescence signal distribution including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence to obtain the OH fluorescence signal distribution, specifically:

[0043] The OH fluorescence signal distribution in the region containing the mixed fluorescence signal of OH fluorescence and polycyclic aromatic hydrocarbon fluorescence is S C1 (x, y)-k•S C2 (x,y).

[0044] The present invention has the following advantages:

[0045] 1. The present invention divides the solid fuel combustion stages based on the differences in the fluorescence signal structures at different stages, and determines the area where only OH groups exist according to different excitation wavelengths and different detection wavelengths, thereby reducing the workload of the implementation method and improving the feasibility of accurate measurement of OH fluorescence.

[0046] 2. The present invention proposes two measurement systems and methods, which make the method of eliminating the interference of PAH fluorescence in the mixed fluorescence of OH and PAHs simpler and more flexible, and can adapt to various conditions and scenarios.

[0047] 3. The present invention eliminates or reduces the interference of polycyclic aromatic hydrocarbons fluorescence on OH fluorescence measurement in solid fuel combustion field OH fluorescence measurement by additionally measuring and correspondingly deducting polycyclic aromatic hydrocarbons fluorescence, thereby greatly improving the accuracy of OH fluorescence intensity measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 Schematic diagram of the measuring device of the present invention.

[0049] Figure 2 Schematic diagram of excitation line selection for fluorescence measurement of OH and polycyclic aromatic hydrocarbons.

[0050] Figure 3 Logic diagram for OH fluorescence measurement.

[0051] Figure 4These are the fluorescence signals of the three stages in the solid particle combustion process: OH resonance excitation line excitation, which can be detected by the wavelength of OH and polycyclic aromatic hydrocarbon fluorescence signals.

[0052] Figure 5 These are the fluorescence signals of the three stages in the solid particle combustion process: OH non-resonant excitation line excitation, which can be detected by the wavelength of OH and polycyclic aromatic hydrocarbon fluorescence signals.

[0053] Figure 6 These are the fluorescence signals of the three stages of the solid particle combustion process: OH resonance excitation line excitation, and detection only by the wavelength of the polycyclic aromatic hydrocarbon fluorescence signal.

[0054] Among them: 1-laser system, 2-sheet beam shaping system, 3-signal detection system, 4-timing synchronization system, 5-computer. DETAILED DESCRIPTION

[0055] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be pointed out that the embodiments described below are intended to facilitate understanding of the present invention and do not have any limiting effect on the present invention.

[0056] The measuring device required for the method of the present invention is as follows Figure 1 , the basic architecture includes a laser system 1, a sheet beam shaping system 2, a signal detection system 3, a timing synchronization system 4, and a computer 5;

[0057] Laser system 1 is used to excite OH and PAHs to produce mixed fluorescence including OH fluorescence and PAH fluorescence (excitation wavelength is 282.95 nm, inline), and to excite PAHs only to produce single PAH fluorescence (excitation wavelength is 282.52 nm, offline). The positions of the two excitation lines are shown in Figure 2 shown. Figure 1 There are two sets, namely laser system L1 and laser system L2;

[0058] The sheet beam shaping system 2 can realize the adjustment and control of the light path, including the direction adjustment of the light beam and the beam shaping to achieve uniform thin sheet light excitation, with a typical sheet light width greater than 30mm and a thickness less than 0.5mm. Its specific structure includes a cylindrical plano-concave lens O1 and a spherical biconvex lens O2;

[0059] The signal detection system 3 is used to select the fluorescence wavelength band to be detected and suppress the stray light of the excitation light: it includes at least one bandpass filter. The signal detection system 3 is used to detect the fluorescence of OH and polycyclic aromatic hydrocarbons (detection wavelength 305-315nm) and the fluorescence of only polycyclic aromatic hydrocarbons (detection wavelength range 425-435nm). Figure 1 There are two sets, namely signal detection system C1 and signal detection system C2;

[0060] The timing synchronization system 4 is connected to the laser system 1, the signal detection system C1, and the signal detection system C2. The flash lamp pump delay time of the laser L1 is set to 0 μs, the Q-Switch delay time of the laser L1 is set to 455 μs, the delay time of the signal detection system C1 is set to 455.02650 μs, and the exposure time is 200 ns.

[0061] The computer 5 calculates an accurate OH fluorescence signal by acquiring a mixed fluorescence signal including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence, a single polycyclic aromatic hydrocarbon fluorescence signal and a correction coefficient;

[0062] The principle method logic diagram is as follows Figure 3 As shown:

[0063] (1) The mixed fluorescence signal distribution including OH fluorescence and PAH fluorescence and the single PAH fluorescence signal distribution are simultaneously obtained, and the combustion stage of the solid fuel is divided according to the mixed fluorescence signal distribution including OH fluorescence and PAH fluorescence, and the area with only OH fluorescence signal in different combustion stages is obtained;

[0064] (2) For the area where OH fluorescence and PAH fluorescence cannot be distinguished, calculate the correction coefficients for different excitation wavelengths and different detection wavelengths;

[0065] (3) In the mixed fluorescence signal distribution including OH fluorescence and PAH fluorescence, the corresponding correction coefficient is deducted from the single PAH fluorescence signal distribution to obtain the OH fluorescence signal distribution.

[0066] The method of the present invention is described in more detail below with examples:

[0067] Embodiment 1:

[0068] Laser system L1 and laser system L2 are used, the laser pulse width is less than 10ns, and laser system L1 is in OHA 2 X+(0,0)←X 2 The Π(0,1) spectral band resonant excitation line has a wavelength of 282.95nm (not limited to 282.95nm), which resonates and excites the OH ground state rotation energy level, and at the same time excites the combustion field PAHs to produce PAH fluorescence; the excitation wavelength of laser system L2 is close to that of laser system 1, but far away from the OH resonant excitation line, with a wavelength of 282.25nm (not limited to 282.95nm), which only excites PAH fluorescence. There is a delay time between the two laser systems, and the delay time interval is adjustable. Within the detection system parameter range, a minimum value greater than the OH fluorescence lifetime is selected to reduce the mutual interference between the two signal detection systems. The excitation delay time of the two laser systems is selected to be 300ns.

[0069] The signal detection systems C1 and C2 connected to the filter unit both use a bandpass filter for receiving 305-315nm to filter out the stray light of the excitation laser and selectively transmit the OH fluorescence and some polycyclic aromatic hydrocarbon fluorescence bands.

[0070] The specific measurement method of Example 1 comprises the following steps:

[0071] Step 1: Use laser system L1 and laser system L2 to excite the solid fuel combustion field, synchronize the signal detection system C1 with L1, and synchronize the signal detection system C2 with L2 to obtain the mixed fluorescence signal distribution S including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence C1 (x, y) and the fluorescence signal distribution S of individual PAHs C2 (x, y);

[0072] Step 2: Distribution of S based on mixed fluorescence signals of OH and PAHs C1 (x, y) divides the solid fuel combustion process into the de-volatilization stage, the volatile combustion stage, and the coke combustion stage. In this embodiment, the solid fuel combustion stages are as follows: Figure 4 As shown;

[0073] Step 3: Compare the distribution of the mixed fluorescence signal including OH fluorescence and PAH fluorescence at different combustion stages with the distribution of the single PAH fluorescence signal, and divide the area where only the OH fluorescence signal exists. In this embodiment, the single PAH fluorescence signal at different combustion stages is as follows: Figure 5 As shown. Figure 4 and Figure 5 It can be clearly found that only OH groups exist in the coke combustion stage, and only OH groups exist downstream of the flame front in the volatile combustion stage. The OH fluorescence signal in these areas is S C1 (x, y);

[0074] Step 4: For areas where OH fluorescence and PAH fluorescence cannot be distinguished, adjust the detection wavelength of the signal detection system C1 to 425-435nm (not limited to 425-435nm), and synchronize the signal detection system C1 with the laser system L1 to obtain the PAH fluorescence signal S' only through PAH fluorescence. C1 (x, y);

[0075] Step 5: Adjust the detection wavelength of the signal detection system C2 to 425-435nm (not limited to 425-435nm), and synchronize the signal detection system C2 with the laser system L2 to obtain the PAH fluorescence signal S' only through the wavelength of PAH fluorescence. C2 (x, y);

[0076] Step 6: Calculate the correction coefficient k=S' for different excitation wavelengthsC1 (x, y) / S' C2 (x, y);

[0077] Step 7: Based on the mixed fluorescence signal including OH fluorescence and PAH fluorescence, the single PAH fluorescence signal and the correction coefficient in the above step, the OH fluorescence signal in the area of ​​the mixed fluorescence signal including OH fluorescence and PAH fluorescence is calculated as S C1 (x, y)-k•S C2 (x,y).

[0078] Embodiment 2:

[0079] In this embodiment, the laser system L1 has a laser pulse width of less than 10ns, and the laser system L1 is in OHA 2 X+(0,0)←X 2 Π(0,1) spectral band resonance excitation line, with a wavelength of 282.95nm (not limited to 282.95nm), resonantly excites OH free radicals to produce OH fluorescence signals, and at the same time excites the combustion field to produce polycyclic aromatic hydrocarbon fluorescence;

[0080] The signal detection systems C1 and C2 connected to the filter unit respectively use a bandpass filter for receiving 305-315nm and a bandpass filter for receiving 425-435nm (not limited to 425-435nm). They are used to filter out the stray light of the excitation laser, selectively transmit OH fluorescence and part of the PAH fluorescence band, and only transmit the PAH fluorescence band;

[0081] The specific measurement method of Example 2 comprises the following steps:

[0082] Step 1: Use the laser system L1 to stimulate the solid fuel combustion field. The signal detection system C1 and the signal detection system C2 are synchronized with the laser system L1 to obtain the mixed fluorescence signal S of OH and PAHs. C1 (x, y) and individual PAH fluorescence signals S C2 (x, y);

[0083] Step 2: The combustion process of the solid fuel is divided into the de-volatilization stage, the volatile combustion stage, and the coke combustion stage according to the distribution of the mixed fluorescence signal including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence. As in Example 1, the combustion stages of the solid fuel are as follows: Figure 4 As shown;

[0084] Step 3: Compare the distribution of the mixed fluorescence signal including OH fluorescence and PAH fluorescence at different combustion stages with the distribution of the single PAH fluorescence signal, and divide the area where only the OH fluorescence signal exists. In this embodiment, the single PAH fluorescence signal at different combustion stages is as follows: Figure 5 As shown. Figure 4and Figure 6 It can be clearly found that only OH groups exist in the coke combustion stage, and only OH groups exist downstream of the flame front in the volatile combustion stage. The OH fluorescence signal in these areas is S C1 (x, y);

[0085] Step 4: For areas where OH fluorescence and PAH fluorescence cannot be distinguished, adjust the wavelength of laser L1 to 282.25 nm (not limited to 282.25 nm) to excite only PAH fluorescence. The signal detection system C1 is synchronized with the laser system L1 to obtain the PAH fluorescence signal S' C1 (x, y);

[0086] Step 5: Synchronize the signal detection system C2 with the laser system L1 to obtain the PAH fluorescence signal S' C2 (x, y);

[0087] Step 6: Calculate the correction coefficient k = S' C1 (x, y) / S' C2 (x, y);

[0088] Step 7: Based on the mixed fluorescence signal including OH fluorescence and PAH fluorescence, the single PAH fluorescence signal and the correction coefficient in the above step, the OH fluorescence signal in the area of ​​the mixed fluorescence signal including OH fluorescence and PAH fluorescence is calculated as S C1 (x, y)-k•S C2 (x, y).

[0089] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for eliminating fluorescence interference in solid fuel OH-PLIF measurement, characterized in that: The following steps are involved: Step 1, simultaneously obtaining the distribution of mixed fluorescence signals including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence and the distribution of single polycyclic aromatic hydrocarbon fluorescence signals, dividing the combustion stage of the solid fuel according to the distribution of mixed fluorescence signals including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence, and obtaining the areas where only OH fluorescence signals exist in different combustion stages; Step 2: For the area where OH fluorescence and PAH fluorescence cannot be distinguished, the correction coefficients of different excitation wavelengths and different detection wavelengths are calculated; Step 3: From the mixed fluorescence signal distribution including OH fluorescence and PAH fluorescence, the corresponding correction coefficient is deducted from the single PAH fluorescence signal distribution to obtain the OH fluorescence signal distribution.

2. The method for eliminating fluorescence interference in solid fuel OH-PLIF measurement according to claim 1, characterized in that: Step 1 includes: Step 1-1, using two sets of laser systems, namely the laser system L1 in the PLIF device and the additional laser system L2, the laser system L1 is used to excite OH and polycyclic aromatic hydrocarbons to produce a mixed fluorescence signal distribution including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence, and the laser system L2 is only used to excite polycyclic aromatic hydrocarbons to produce a single polycyclic aromatic hydrocarbon fluorescence signal distribution; Step 1-2, using two signal detection systems, namely, the signal detection system C1 in the PLIF device and the additional signal detection system C2. By setting the detection wavelengths of the signal detection system C1 and the signal detection system C2, the signal detection system C1 and the signal detection system C2 can both detect the distribution of OH fluorescence and polycyclic aromatic hydrocarbon fluorescence signals; Step 1-3: The sampling time of the signal detection system C1 is synchronized with the laser system L1 to obtain a mixed fluorescence signal distribution S including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence. C1 (x, y), the sampling time of the signal detection system C2 is synchronized with the laser system L2 to obtain the fluorescence signal distribution S of individual PAHs C2 (x, y), a delay time is set between the laser system L1 and the laser system L2, and the delay time is greater than the minimum value of the OH fluorescence lifetime; Step 1-4: Distribute S according to the mixed fluorescence signal including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence C1 (x, y), dividing the solid fuel combustion stage into a de-volatilization stage, a volatile combustion stage and a coke combustion stage; Step 1-5: In the de-volatilization stage, the volatile combustion stage, and the coke combustion stage, the region where there is no single PAH fluorescence signal but a mixed fluorescence signal including OH fluorescence and PAH fluorescence is a region where only OH fluorescence signal exists, and the fluorescence signal distribution of this region is S C1 (x, y); Step 1-6: In the devolatilization stage, the volatile combustion stage and the coke combustion stage, the region where the OH fluorescence and the PAH fluorescence cannot be distinguished is referred to as a region containing mixed fluorescence signals of the OH fluorescence and the PAH fluorescence.

3. The method for eliminating fluorescence interference in solid fuel OH-PLIF measurement according to claim 1, characterized in that: Step 1 includes: Step 1-1, using a laser system, which is the laser system L1 in the PLIF device, the laser system L1 is used to excite OH and polycyclic aromatic hydrocarbons to generate a mixed fluorescence signal distribution including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence; Step 1-2, using two signal detection systems, namely the signal detection system C1 in the PLIF device and the additional signal detection system C2. By setting the detection wavelengths of the signal detection system C1 and the signal detection system C2, the signal detection system C1 can detect the OH fluorescence and the distribution of the polycyclic aromatic hydrocarbon fluorescence signals, and the signal detection system C2 can only detect the distribution of the polycyclic aromatic hydrocarbon fluorescence signals; Step 1-3: The sampling time of the signal detection system C1 is synchronized with the laser system L1 to obtain the fluorescence signal S C1 (x, y), the sampling time of the signal detection system C2 is synchronized with the laser system L1 to obtain the fluorescence signal S C2 (x, y); Step 1-4: Based on the mixed fluorescence signal S including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence C1 (x, y), dividing the solid fuel combustion stage into a de-volatilization stage, a volatile combustion stage and a coke combustion stage; Step 1-5: In the de-volatilization stage, the volatile combustion stage, and the coke combustion stage, the region where there is no single PAH fluorescence signal but a mixed fluorescence signal including OH fluorescence and PAH fluorescence is a region where only OH fluorescence signal exists, and the fluorescence signal distribution of this region is S C1 (x, y); Step 1-6: In the devolatilization stage, the volatile combustion stage and the coke combustion stage, the region where the OH fluorescence and the PAH fluorescence cannot be distinguished is referred to as a region containing mixed fluorescence signals of the OH fluorescence and the PAH fluorescence.

4. The method for eliminating fluorescence interference in solid fuel OH-PLIF measurement according to claim 2, characterized in that: Step 2 includes: Step 2-1, using two sets of laser systems, namely, the laser system L1 in the PLIF device and the additional laser system L2, the laser system L1 is used to excite OH and polycyclic aromatic hydrocarbons to generate a mixed fluorescence signal distribution including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence, and the laser system L2 is only used to excite polycyclic aromatic hydrocarbons to generate polycyclic aromatic hydrocarbon fluorescence signal distribution; Step 2-2, using two signal detection systems, namely the signal detection system C1 in the PLIF device and an additional signal detection system C2, by setting the detection wavelengths of the signal detection system C1 and the signal detection system C2, the signal detection system C1 and the signal detection system C2 are only used to detect the distribution of polycyclic aromatic hydrocarbon fluorescence signals; Step 2-3: The sampling time of the signal detection system C1 is synchronized with the laser system L1 to obtain the individual PAH fluorescence signal S' C1 (x, y), the sampling time of the signal detection system C2 is synchronized with the laser system L2 to obtain the individual PAH fluorescence signal S' C2 (x, y), a delay time is set between the laser system L1 and the laser system L2, and the delay time is greater than the minimum value of the OH fluorescence lifetime; Step 2-4, Correction coefficient k=S' for different excitation wavelengths C1 (x, y) / S' C2 (x, y).

5. The method for eliminating fluorescence interference in solid fuel OH-PLIF measurement according to claim 3, characterized in that: Step 2 includes: Step 2-1, using a laser system, which is L1 in the PLIF device, to excite only the PAHs to generate fluorescence of individual PAHs; Step 2-2, using two signal detection systems, namely the signal detection system C1 in the PLIF device and an additional signal detection system C2. By setting the detection wavelengths of the signal detection system C1 and the signal detection system C2, the signal detection system C1 can detect OH fluorescence and polycyclic aromatic hydrocarbon fluorescence signals, and the signal detection system C2 is only used to detect polycyclic aromatic hydrocarbon fluorescence signals; Step 2-3: The sampling time of the signal detection system C1 is synchronized with the laser system L1 to obtain the fluorescence signal distribution S' of individual PAHs. C1 (x, y), the sampling time of the signal detection system C2 is synchronized with the laser system L1 to obtain the fluorescence signal distribution S' of individual PAHs C2 (x, y); Step 2-4, Correction coefficient k=S' for different detection wavelengths C1 (x, y) / S' C2 (x, y).

6. The method for eliminating fluorescence interference in solid fuel OH-PLIF measurement according to claim 1, characterized in that: In step 3, the OH fluorescence signal distribution in the region containing the mixed fluorescence signal of OH fluorescence and polycyclic aromatic hydrocarbon fluorescence is S C1 (x, y)-k•S C2 (x, y).

7. The method for eliminating fluorescence interference in solid fuel OH-PLIF measurement according to any one of claims 2 to 5, characterized in that: In addition to the laser system and the signal detection system, the PLIF device also includes a sheet beam shaping system, a signal detection system, a timing synchronization system and a computer; The sheet beam shaping system is composed of a cylindrical lens and a spherical lens, which focuses the laser into a laser sheet; The timing synchronization system is used to control the triggering time of the equipment in the PLIF device; The computer calculates the OH fluorescence intensity distribution by acquiring the mixed fluorescence intensity distribution including OH fluorescence and polycyclic aromatic hydrocarbon fluorescence and the single polycyclic aromatic hydrocarbon fluorescence intensity distribution.

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