A system for measuring the internal structure and temperature field of a strong turbulent ammonia combustion flame

Abstract

The present application relates to a kind of strong turbulent ammonia combustion flame internal structure and temperature field measurement system, a small amount of oxygen-containing fuel is added in strong turbulent ammonia combustion field to generate CH2O mark preheating zone, a Nd:YAG pumping laser is used to emit 355nm and 532nm laser simultaneously, wherein 355nm laser is used to excite CH2O and Rayleigh scattering signal;303nm laser is obtained after 532nm laser pumps dye laser to be frequency doubled, for exciting NH;CH2O fluorescence signal, Rayleigh scattering signal and NH fluorescence signal are detected by using three ICCD cameras distribution.By the present application, it can be realized to use a set of Nd:YAG, dye laser and three ICCD cameras, the synchronous measurement of ammonia combustion flame preheating zone, reaction zone and temperature field.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of combustion using ammonia as fuel, and relates to synchronous measurement of preheating zone, reaction zone and temperature field in ammonia flame combustion process, in particular to a system for measuring internal structure and temperature field of strong turbulent ammonia combustion flame. BACKGROUND

[0002] The combustion rate of ammonia fuel is very slow, only 7 cm / s under premixed equivalence ratio condition, about one fifth of methane (the main component of natural gas), and the flame thickness is thick, which can reach about 1 mm. Therefore, in the actual combustion process, it is very easy to be in a strong turbulent environment. Under this condition, turbulent vortex will affect the distribution characteristics of the preheating zone and even the reaction zone of the flame. The difference in flame structure such as reaction zone or preheating zone will cause changes in heat release rate and temperature distribution, which has a great influence on the combustion efficiency and combustion stability of the actual combustor. Therefore, it is necessary to study the ammonia flame structure and temperature distribution under strong turbulent conditions.

[0003] Planar Laser-induced Fluorescence (PLIF) technology and Rayleigh Scattering Thermometry (RST) are non-contact optical diagnostic measurement technologies that have emerged since the birth of the laser. Laser diagnosis is based on the rules of laser and matter interaction, which can realize online measurement of components, temperature and velocity in the combustion field with high precision, high spatial and temporal resolution and weak interference. The current experimental research work on ammonia flame is mainly to separate the post-combustion zone (OH or NO characterization), reaction zone structure or temperature field for separate research. However, the flame structure and temperature field obtained by using laser-induced fluorescence method or Rayleigh scattering thermometry alone cannot be used to study the coupling process of flow and chemical reaction in the strong turbulent combustion process of ammonia fuel. Moreover, there is no suitable component to characterize the preheating zone of ammonia combustion at present, and a suitable technical method is needed to identify and measure the preheating zone.

[0004] In the study of multi-parameter interaction, synchronous measurement technology is usually used. Synchronous measurement generally controls the trigger / detection time and the measured space of multiple devices at the same position to achieve the goal of obtaining multi-parameter spatial and temporal information. However, laser synchronous measurement generally requires more lasers, which greatly increases the pre-experimental investment cost and the complexity of experimental operation. SUMMARY

[0005] In order to overcome the above-mentioned defects of the prior art, the present application aims to provide a strong turbulent ammonia combustion flame internal structure and temperature field measurement system to achieve the goal of synchronously measuring ammonia flame reaction zone, preheating zone and temperature field by using a set of lasers, and to provide a basis for studying the interaction mechanism of ammonia turbulent flame flow and chemical reaction.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present application is:

[0007] A strong turbulent ammonia combustion flame internal structure and temperature field measurement system, comprising a Nd:YAG pump laser, a dye laser, a temperature measurement ICCD camera, an NH measurement ICCD camera and a CH2O measurement ICCD camera.

[0008] The Nd:YAG pump laser simultaneously emits 355nm laser and 532nm laser.

[0009] The dye laser pumps a dye cell with the 532nm laser to generate 606nm laser, and frequency doubles the 606nm laser to obtain 303nm laser.

[0010] The 355nm laser and the 303nm laser are configured to pass through the jet outlet of a strong turbulent premixed jet combustor with a pilot flame, so that the 355nm laser excites CH2O fluorescence signal and Rayleigh scattering signal, and the 303nm laser excites NH fluorescence signal.

[0011] The temperature measurement ICCD camera, the NH measurement ICCD camera and the CH2O measurement ICCD camera synchronously collect Rayleigh scattering signal, NH fluorescence signal and CH2O fluorescence signal respectively.

[0012] In one embodiment, the Nd:YAG pump laser generates 1064nm laser, the 1064nm laser outputs 532nm laser after passing through a double frequency crystal, and then outputs 355nm laser after passing through a triple frequency crystal; the Nd:YAG pump laser is provided with a 355-R-532-T dichroic mirror, the 355-R-532-T dichroic mirror separates the 355nm laser and the 532nm laser to achieve simultaneous emission of the 532nm laser and the 355nm laser.

[0013] In one embodiment, the 532nm laser enters the dye laser, the oscillation stage dye cell and the amplification stage dye cell of the dye laser have different concentrations of dye solution circulating therein respectively to excite base frequency laser of 580nm-630nm, after passing through a grating, 606nm laser is output, and then passing through a double frequency crystal, 303nm laser is obtained.

[0014] In one embodiment, the measurement system further comprises a mirror set, which is composed of mirrors corresponding to the laser wavelength, for adjusting the laser incident and emission direction.

[0015] In one embodiment, the measurement system further comprises a light polarization adjuster, which is a rotating half-wave plate, for adjusting the polarization direction of the 355nm laser to obtain vertically polarized laser, in the following way:

[0016] The rotating half-wave plate is arranged in the laser light path at a convenient adjustment position;

[0017] Uniform gas is introduced into the area to be measured through which the laser sheet passes;

[0018] The half-wave plate is rotated by 1-3° each time, and the Rayleigh scattering signal intensity is sequentially captured by the camera;

[0019] The captured results are spatially and temporally averaged to obtain the average signal intensity value, and a graph of different half-wave plate angles and average signal intensity values is drawn to obtain the corresponding relationship between the highest signal intensity and the half-wave plate angle. The half-wave plate angle position corresponding to the highest signal intensity is the required vertically polarized light.

[0020] In one embodiment, the measurement system further comprises a 303-R-355-T dichroic mirror, which is used to combine the 355nm laser and the 303nm laser, and the combined laser passes through the jet outlet of the strong turbulent premixed jet combustor, so that the NH fluorescence signal and the CH2O fluorescence signal are 90° separated.

[0021] In one embodiment, the measurement system further comprises a sheet light generating mirror set, which comprises a plano-concave lens and a convex lens arranged in sequence along the light path. The plano-concave lens shapes the circular laser spot obtained after combination into a spindle-shaped long sheet light. After the sheet light passes through the convex lens, the thinnest sheet light is formed at the focal position. The position to be measured by the flame is adjusted to the thinnest sheet light.

[0022] In one embodiment, the temperature measurement ICCD camera is arranged on one side of the laser sheet light, the NH measurement ICCD camera and the CH2O measurement ICCD camera are arranged vertically on the other side of the laser sheet light, and the 337-R-364-T dichroic mirror is arranged on the other side to transmit the reflected signal and the transmitted signal to the NH measurement ICCD camera and the CH2O measurement ICCD camera, respectively.

[0023] In one embodiment, the central jet pipe of the strong turbulent premixed jet combustor is introduced with premixed gas containing ammonia, and 1-2% of oxygen-containing fuel is mixed in the premixed gas.

[0024] In one embodiment, a filter is arranged in front of the lens of the temperature measuring ICCD camera, the NH measuring ICCD camera and the CH2O measuring ICCD camera, the filter in front of the temperature measuring ICCD camera is a band-pass filter with a wavelength range of 355±10nm, the filter in front of the NH measuring ICCD camera is a band-pass filter with a wavelength range of 337±10nm, and the filter in front of the CH2O measuring ICCD camera is a filter set composed of a long-pass filter with a wavelength of 364nm and a short-pass filter with a wavelength of 468nm.

[0025] Compared with the prior art, the present application can realize the synchronous detection of the preheating zone, reaction zone structure and temperature field of the ammonia combustion turbulent flame by using only one set of Nd:YAG pumping laser, a dye laser and three ICCD cameras. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The optical path for the synchronous measurement of the internal structure and temperature field of the strong turbulent ammonia combustion flame.

[0027] Figure 2 The schematic diagram of a strong turbulent premixed jet combustor with a pilot flame.

[0028] Figure 3 The example of the change of the Rayleigh scattering signal intensity with the angle of the half-wave plate. DETAILED DESCRIPTION

[0029] The specific embodiments of the method for the synchronous measurement of the preheating zone, reaction zone structure and temperature field of the ammonia combustion turbulent flame provided by the present application will be described in detail below with reference to the accompanying drawings.

[0030] In view of the foregoing status, the present application provides a system for measuring the internal structure and temperature field of a strong turbulent ammonia combustion flame, which comprises Figure 1 and mainly includes an Nd:YAG pumping laser 1, a dye laser 7, a temperature measuring ICCD camera 19, an NH measuring ICCD camera 20 and a CH2O measuring ICCD camera 21.

[0031] The system only uses one set of Nd:YAG pumping laser 1, cooperates with the dye laser 7 and three ICCD cameras, and can realize the synchronous measurement of the preheating zone, reaction zone structure and temperature field of the ammonia combustion turbulent flame. The reaction zone of the ammonia combustion adopts the NH free radical representation, 1-2% of oxygen-containing fuel (such as dimethyl ether, DME) is mixed in the ammonia-containing premixed gas for generating the CH2O free radical to identify the preheating zone, and the CH2O-PLIF measurement representation is used to represent the combustion preheating zone.

[0032] The measuring system adopts a Nd:YAG pump laser 1 to simultaneously emit 355nm and 532nm lasers, wherein the 355nm laser is used to excite CH2O fluorescence signal and Rayleigh scattering signal; the 532nm laser pumps a dye laser 7 to generate 606nm laser and to generate 303nm laser by frequency doubling, which is used to excite NH; wherein, to realize excitation, the 355nm laser and the 303nm laser should be configured to pass through the jet outlet of the strong turbulent premixed jet combustor 15 with a pilot flame. The temperature measuring ICCD camera 19, the NH measuring ICCD camera 20 and the CH2O measuring ICCD camera 21 constitute a signal imaging receiving system, which respectively detects Rayleigh scattering signal, NH fluorescence signal and CH2O fluorescence signal, i.e. realizes synchronous measurement.

[0033] In an embodiment of the present application, the strong turbulent ammonia combustion flame internal structure and temperature field synchronous measurement optical path is as shown in the accompanying drawings. Figure 1 The Nd:YAG pump laser 1 generates 1064nm laser, outputs 532nm laser after passing through a second frequency doubling crystal, and then outputs 355nm laser after passing through a third frequency doubling crystal, finally obtains laser beams of 355+532+1064nm, separates the 355nm laser and the 532nm laser by the 355-R-532-T dichroic mirror 2 internally installed, and the 1064nm laser passes through a high reflection mirror and is captured by the beam collector 6. Thus, the Nd:YAG pump laser 1 simultaneously emits the 532nm laser and the 355nm laser respectively.

[0034] In an embodiment of the present application, the 532nm laser enters the dye laser 7, and different concentrations of dye solutions are circulated in the oscillation stage dye pool and the amplification stage dye pool of the dye laser 7 respectively, for example, the oscillation stage can be selected as 1×10 -3 mol / L Rhodamine 610 / ethanol solution and the amplification stage can be selected as 3.8×10 -5 mol / L Rhodamine 640 / ethanol solution, which can excite fundamental frequency laser of about 580nm-630nm, then adjust the grating position in the dye laser 7 to about 606nm, adjust the angles of each mirror group in the dye laser 7 and the angle of the frequency doubling crystal, so that the output energy of the dye laser 7 is in an optimal condition. After grating selection, about 606nm laser is output, and then 303nm laser is obtained by passing through a second frequency doubling crystal.

[0035] In an embodiment of the present application, the measuring system further comprises a mirror group, which is composed of high-efficiency mirrors corresponding to laser wavelengths, and is used for adjusting the incident and outgoing directions of laser.

[0036] For example, in the Nd:YAG pump laser 1, the first 355nm high reflection mirror 3 can be arranged to adjust the propagation direction of the 355nm laser beam outputted by the 355-R-532-T dichroic mirror. Outside the Nd:YAG pump laser 1, the second 355nm high reflection mirror 9 and the third 355nm high reflection mirror 10 can be arranged to adjust the propagation direction of the 355nm laser beam again. Meanwhile, outside the Nd:YAG pump laser 1, the first 532nm high reflection mirror 4 and the second 532nm high reflection mirror 5 can be arranged to adjust the propagation direction of the 532nm laser beam and then enter the dye laser 7. On the route of the 303nm laser outputted by the dye laser 7, the ultraviolet high reflection mirror 8 can be arranged to adjust the propagation direction of the beam.

[0037] It is worth mentioning that the adjustment of the beam propagation direction is mainly for the consideration of device layout, and the mirror set can also have other various setting forms under the premise of meeting the functional requirements.

[0038] In an embodiment of the present application, the measurement system further comprises a light polarization adjuster 11, which is a rotatable half-wave plate, used to adjust the polarization direction of the 355nm laser to obtain the vertically polarized laser to obtain the strongest Rayleigh scattering signal. The light polarization adjuster 11 should obviously be arranged on the route of the 355nm laser. The present application also provides a specific adjustment method for obtaining the vertically polarized laser as follows:

[0039] 1) The rotatable half-wave plate is arranged at a position convenient for adjustment in the laser light path;

[0040] 2) A uniform gas, such as air, nitrogen, etc., is introduced into the to-be-measured region through which the laser beam passes;

[0041] 3) The half-wave plate is rotated by 1-3° each time, and the Rayleigh scattering signal intensity is sequentially captured by the camera;

[0042] 4) The captured results are spatially and temporally averaged to obtain the average signal intensity value, and a graph of different half-wave plate angles and average signal intensity values is drawn, as shown in FIG. 4, to obtain the corresponding relationship between the highest signal intensity and the half-wave plate angle, and the half-wave plate angle position corresponding to the highest signal intensity is the required vertically polarized light. Figure 3

[0043] In an embodiment of the present application, the measurement system further comprises a 303-R-355-T dichroic mirror 12, which is used to realize the transmission of light in a specific wavelength range and the reflection of light in other wavelengths. In this embodiment, the 303-R-355-T dichroic mirror 12 is used to realize the beam combination of the 355nm laser and the 303nm laser, and the combined laser passes through the jet outlet of the strong turbulent premixed jet burner 15 to obtain the NH fluorescence signal and the CH2O fluorescence signal 90° separated.​

[0044] In the case of the aforementioned setting of the mirror group, the 355 nm laser is reflected by the second 355 nm high reflection mirror 9 and the third 355 nm high reflection mirror 10 to adjust the light beam propagation direction, and then passes through the light polarization adjuster 11 arranged in the light path, and then is combined with the 303 nm laser output by the dye laser 7 at the position of the 303-R-355-T dichroic mirror 12.

[0045] In an embodiment of the present application, the measurement system further comprises a sheet light generating mirror group, which mainly comprises a plano-concave lens 13 with a specific focal length and a convex lens 14 with a specific focal length arranged in sequence along the light path. The plano-concave lens 13 shapes the circular laser spot obtained after the combination into a spindle-shaped sheet light. After passing through the convex lens 14, the spindle-shaped sheet light can form the thinnest sheet light at the focal length position. Adjusting the position of the flame to be measured to the thinnest sheet light can obtain a better signal.

[0046] In the embodiment, after the combination of the two laser beams, the sheet light is formed by the mirror group composed of the plano-concave lens 13 and the convex lens 14. At this time, the position of the strong turbulent premixed jet burner 15 is adjusted so that the sheet light passes through the center of the jet outlet of the burner. The schematic diagram of the structure of the burner is shown in FIG. 2. Figure 2 Then, the front and back positions of the plano-concave lens 13 and the convex lens 14 of the sheet light generating mirror group are adjusted so that the sheet light focal point is also located at the center of the jet outlet of the strong turbulent premixed jet burner 15, and the strong turbulent premixed jet burner 15 is fixed. The laser protection plate 16 can be arranged after the laser passes through the strong turbulent premixed jet burner 15 to prevent the laser from passing through the experimental area.

[0047] In the present application, the strong turbulent premixed jet burner 15 is used to stabilize the generation of ammonia / air or ammonia / oxygen / nitrogen premixed jet flames in each working condition to be measured. Under the condition of strong turbulence, the central jet ammonia premixed flame is extremely difficult to self-sustain and stabilize, and a standby flame needs to be provided for stabilization. The standby flame usually adopts a hydrocarbon / air premixed flame, such as a methane / air premixed flame, to burn in quasi-laminar flow and near stoichiometric ratio, and the heat released by the combustion is propagated downstream. The high-temperature burned gas and active free radicals are used to maintain the central jet ammonia premixed flame on the one hand, and to prevent the low-temperature air from being sucked into the central jet on the other hand, thereby preventing low-temperature blowout.

[0048] In an embodiment of the present application, the central jet pipe of the strong turbulent premixed jet burner 15 is connected to the premixed gas containing ammonia, and 1-2% of oxygen-containing fuel (such as dimethyl ether, DME) is mixed in the premixed gas. By this means, more CH2O free radicals can be generated, which is more conducive to identifying the preheating zone of the ammonia combustion field with CH2O free radicals and measuring and characterizing the preheating zone with CH2O-PLIF, so as to make up for the current defect that there is no suitable free radical to characterize the preheating zone of the ammonia flame.

[0049] In one embodiment of the present application, three ICCD cameras can be respectively equipped with ultraviolet lenses (CH2O detection can use visible light lenses) and specific filters 18. Specifically, the temperature measurement ICCD camera 19 is equipped with an ultraviolet lens, and the filter 18 in front of the lens is a 355±10 nm band-pass filter. The NH measurement ICCD camera 20 is also equipped with an ultraviolet lens, and the filter 18 in front of the lens is a 337±10 nm band-pass filter. The CH2O measurement ICCD camera 21 is equipped with a visible or ultraviolet lens, and the filter 18 in front of the lens is a filter group composed of a 364 nm long-pass filter and a 468 nm short-pass filter.

[0050] In one embodiment of the present application, since the preheating zone and reaction zone signals are both laser-induced fluorescence (LIF) signals, and the temperature information is a Rayleigh scattering signal, the signal intensity of the latter is about two orders of magnitude lower than that of the former. In order to reduce the loss of the Rayleigh scattering signal, the temperature measurement ICCD camera 19 is arranged alone on one side of the laser sheet light, and the NH measurement ICCD camera 20 and the CH2O measurement ICCD camera 21 are arranged vertically on the other side of the laser sheet light, and a 337-R-364-T dichroic mirror 17 is arranged on the other side, which transmits the reflected signal and the transmitted signal to the NH measurement ICCD camera 20 and the CH2O measurement ICCD camera 21, respectively.

[0051] The arrangement positions of the three ICCD cameras can be based on the arrangement of the optical path shown in FIG. 2. Figure 1 As shown in FIG. 2, the 337-R-364-T dichroic mirror 17 can reflect 337 nm laser and transmit laser above 364 nm, and the NH measurement ICCD camera 20 and the CH2O measurement ICCD camera 21 are arranged vertically to capture NH and CH2O.

[0052] The synchronous measurement method of the present application includes two parts of NH radical and CH2O radical planar laser-induced fluorescence (PLIF) detection and Rayleigh scattering temperature measurement. The NH-PLIF captures the flame reaction zone structure, the CH2O-PLIF captures the flame preheating zone structure, and the Rayleigh scattering temperature measurement captures the flame temperature field. The three are measured by a measurement system of a set of Nd:YAG pump lasers, a dye laser, three ICCD cameras, and a series of optical elements. The strong turbulent ammonia flame formed by the premixed jet combustor with the standing flame is studied, and the synchronous measurement of the preheating zone, the reaction zone, and the temperature field of the ammonia flame can be realized. The steps of the above measurement method can be described as follows:

[0053] (1) Adjust the wavelength of the dye laser 7, and arrange the optical elements in the system according to the light path, so that the 355 nm laser and the 303 nm laser are combined and output to the cylindrical lens assembly to generate laser sheet light;

[0054] (2) Adjust the laser sheet light to pass through the center of the jet tube of the strong turbulent premixed jet burner 15, and the focal point of the sheet light is also in the center of the jet tube;

[0055] (3) Adjust the ICCD cameras, move the cameras forward and backward, adjust the size of the measured view window, and adjust the focal length of the cameras so that the focal plane of the camera view window is in the center of the jet tube of the burner;

[0056] (4) Take pictures of the scale and calibration board of the camera, and this result will be used as a reference for the later synchronous image absolute position superposition comparison processing and analysis;

[0057] (5) Ignite the ammonia flame, and mix 1-2% oxygen-containing fuel (such as dimethyl ether, DME) in the ammonia flame to generate CH2O free radicals in the combustion process.

[0058] (6) Install the filter 8, adjust the camera delay and gate width, so as to obtain high-quality NH fluorescence signal and CH2O fluorescence signal;

[0059] (7) Rotate the half-wave plate angle, process to obtain the variation law of Rayleigh scattering signal intensity with the half-wave plate angle, refer to this result, and rotate the half-wave plate to the vertical polarization position, at which the Rayleigh scattering signal is the strongest;

[0060] (8) Further, measure the electronic delay and optical delay of the synchronous measurement system using an oscilloscope and a photomultiplier tube, and optimize the camera setting parameters.

[0061] More specifically, in use, the temperature measurement ICCD camera 19 and the CH2O measurement ICCD camera 21 are coarsely adjusted to be perpendicular to the light path, the NH measurement ICCD camera 20 is coarsely adjusted to be parallel to the light path, and the camera front and back positions and the camera lens focal length are finely adjusted, so that the imaging sizes of the three ICCD cameras tend to be consistent, and the lens focal points are at the laser passing plane. It is worth noting that during the adjustment of the imaging size and the focal length of the ICCD camera, the 337-R-364-T dichroic mirror 17 can be removed, the imaging and the focal length of the CH2O measurement ICCD camera 21 are adjusted first, then a high-reflective mirror in the visible light range is placed at the position of the 337-R-364-T dichroic mirror 17, and the imaging and the focal length of the NH measurement ICCD camera 20 are adjusted.

[0062] After the imaging size and the focal length of the three ICCD cameras are adjusted, a clear and identifiable calibration board is placed above the outlet of the strong turbulent premixed jet burner 15, and the three ICCD cameras respectively take pictures of the calibration board, which is used as a reference for the later image processing and analysis. After the camera position calibration is completed, the filter 18 is added in front of the camera.

[0063] After that, the jet outlet of the strong turbulent premixed jet burner 15 is connected with stable gas with uniform composition and temperature, such as air or nitrogen. Then the angle of the light polarization adjuster 11 is adjusted, and the Rayleigh scattering signal intensity is photographed by the temperature measurement ICCD camera 19 in several times with 1-3° rotation each time. The photographed results are spatially and temporally averaged to obtain the average signal intensity value, and the image of the average signal intensity value versus the angle of the half-wave plate is drawn, as shown in FIG. 4, to obtain the corresponding relationship between the maximum signal intensity and the angle of the half-wave plate, and the corresponding vertical polarized light is obtained, and the light polarization adjuster 11 is rotated to the corresponding angle. Figure 3

[0064] After the light path of the synchronous measurement system is prepared, the ammonia flame can be ignited. First, the premixed gas of hydrocarbon fuel / air or hydrocarbon fuel / oxygen / nitrogen is connected to the duty class of the strong turbulent premixed jet burner 15, and the mixture ratio is kept near the stoichiometric ratio. The duty class flame is ignited, and then the premixed gas of ammonia fuel / air or ammonia fuel / oxygen / nitrogen is connected to the center jet, and 1-2% of oxygen-containing fuel (such as dimethyl ether) is mixed in the premixed gas for generating CH2O free radicals that can characterize the preheating zone. After the premixed gas of the center jet is connected, it will be automatically ignited by the high-temperature atmosphere of the duty class flame.

[0065] After the flame is ignited, the delay and gate width of the ICCD camera image intensifier are adjusted so that the signal image with high signal-to-noise ratio is obtained in the camera. The adjustment of the delay can be accurately determined by connecting the oscilloscope with the photomultiplier light matching filter, and the gate width is generally kept below 100 ns. In this way, the synchronous measurement results of the preheating zone, the reaction zone and the temperature field of the ammonia flame can be obtained.

[0066] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various flexible modifications and optimization methods. Any modification, equivalent replacement, improvement and optimization made within the spirit and principle of the present application shall be included in the protection scope of the present application.​

Claims

1. A system for measuring internal structure and temperature field of a strongly turbulent ammonia combustion flame, characterized by, The measurement system comprises a Nd:YAG pump laser (1), a dye laser (7), a temperature measurement ICCD camera (19), a NH measurement ICCD camera (20) and a CH2O measurement ICCD camera (21); The Nd:YAG pump laser (1) simultaneously emits 355nm laser and 532nm laser; The dye laser (7) pumps the dye pool with the 532nm laser to generate 606nm laser, and the 606nm laser is frequency-doubled to obtain 303nm laser; The 355nm laser and the 303nm laser are configured to pass through the jet outlet of the strong turbulent premixed jet combustor (15) with a standing flame, so that the 355nm laser excites CH2O fluorescence signal and Rayleigh scattering signal, and the 303nm laser excites NH fluorescence signal; The temperature measurement ICCD camera (19), the NH measurement ICCD camera (20) and the CH2O measurement ICCD camera (21) synchronously collect Rayleigh scattering signal, NH fluorescence signal and CH2O fluorescence signal respectively.

2. The system for measurement of internal structure and temperature field of a strongly turbulent ammonia combustion flame according to claim 1, characterized in that, The Nd:YAG pump laser (1) generates 1064nm laser, the 1064nm laser is output after passing through a second harmonic generation crystal to output 532nm laser, and then passes through a third harmonic generation crystal to output 355nm laser; the Nd:YAG pump laser (1) is provided with a 355-R-532-T dichroic mirror (2), the 355-R-532-T dichroic mirror (2) separates the 355nm laser and the 532nm laser, and simultaneously emits the 532nm laser and the 355nm laser.

3. The system for measurement of internal structure and temperature field of a strongly turbulent ammonia combustion flame according to claim 1, characterized in that, The 532nm laser enters the dye laser (7), the oscillation stage dye pool and the amplification stage dye pool of the dye laser (7) have dye solutions with different concentrations circulating therein respectively, a fundamental frequency laser of 580nm-630nm is excited, after passing through a grating, 606nm laser is output, and then passing through a second harmonic generation crystal, 303nm laser is obtained.

4. The system for measuring internal structure and temperature field of a strongly turbulent ammonia combustion flame according to claim 1 or 3, characterized in that, The measurement system further comprises a mirror group, the mirror group is composed of mirrors corresponding to laser wavelengths, and is used for adjusting the incident and emission directions of laser.

5. The system for measurement of internal structure and temperature field of a strongly turbulent ammonia combustion flame according to claim 1, characterized in that, The measurement system further comprises a light polarization adjuster (11), the light polarization adjuster is a rotating half-wave plate, and is used for adjusting the polarization direction of the 355nm laser to obtain vertically polarized laser, and the method is as follows: (1) the rotating half-wave plate is arranged in the laser light path at a position convenient for adjustment; (2) uniform gas with the same state is introduced into the to-be-measured area through which the laser sheet light passes; (3) the half-wave plate angle is rotated by 1-3° each time, and the Rayleigh scattering signal intensity is sequentially captured by the camera; (4) the captured results are spatially and temporally averaged to obtain average signal intensity values, a graph of different half-wave plate angles and average signal intensity values is drawn, the corresponding relationship between the highest signal intensity and the half-wave plate angle is obtained, and the half-wave plate angle position corresponding to the highest signal intensity is the required vertically polarized light.

6. The system for measurement of internal structure and temperature field of a strongly turbulent ammonia combustion flame according to claim 1, characterized in that, The measurement system further comprises a 303-R-355-T dichroic mirror (12) for combining the 355nm laser and the 303nm laser, and the combined laser passes through the jet outlet of the strong turbulent premixed jet burner (15), so that the NH fluorescence signal and the CH2O fluorescence signal are 90° separated.

7. The system for measurement of internal structure and temperature field of a strongly turbulent ammonia combustion flame according to claim 6, characterized in that, The measurement system further comprises a sheet light generating mirror group, which comprises a plano-concave lens (13) and a convex lens (14) arranged in sequence along the light path, the plano-concave lens (13) shapes the circular laser spot after combination into a spindle-shaped long sheet light, and the sheet light forms the thinnest sheet light at the focal length position after passing through the convex lens (14), and the position to be measured of the flame is adjusted to the thinnest sheet light.

8. The system for measurement of internal structure and temperature field of a strongly turbulent ammonia combustion flame according to claim 1, characterized in that, The temperature measurement ICCD camera (19) is arranged on one side of the laser sheet light, the NH measurement ICCD camera (20) and the CH2O measurement ICCD camera (21) are arranged vertically on the other side of the laser sheet light, and the other side is provided with a 337-R-364-T dichroic mirror (17) for transmitting the reflected signal and the transmitted signal to the NH measurement ICCD camera (20) and the CH2O measurement ICCD camera (21) respectively.

9. The system for measurement of internal structure and temperature field of a strongly turbulent ammonia combustion flame according to claim 1, characterized in that, The central jet pipe of the strong turbulent premixed jet burner (15) is connected to the premixed gas containing ammonia, and 1-2% of oxygen-containing fuel is mixed in the premixed gas.

10. The system for measurement of internal structure and temperature field of a strongly turbulent ammonia combustion flame according to claim 1, characterized in that, A filter (18) is arranged in front of the lens of the temperature measurement ICCD camera (19), the NH measurement ICCD camera (20) and the CH2O measurement ICCD camera (21), the filter (18) in front of the temperature measurement ICCD camera (19) is a 355±10nm band-pass filter, the filter (18) in front of the NH measurement ICCD camera (20) is a 337±10nm band-pass filter, and the filter (18) in front of the CH2O measurement ICCD camera (21) is a filter group composed of a 364nm long-pass filter and a 468nm short-pass filter. A filter (18) is arranged in front of the lens of the temperature measurement ICCD camera (19), the NH measurement ICCD camera (20) and the CH2O measurement ICCD camera (21), the filter (18) in front of the temperature measurement ICCD camera (19) is a 355±10nm band-pass filter, the filter (18) in front of the NH measurement ICCD camera (20) is a 337±10nm band-pass filter, and the filter (18) in front of the CH2O measurement ICCD camera (21) is a filter group composed of a 364nm long-pass filter and a 468nm short-pass filter.

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