Three-dimensional measurement device and method for optical signals in optical engine cylinder based on three-dimensional chromatography

Abstract

The invention discloses a three-dimensional measurement device and method for optical signals in an optical engine cylinder based on a three-dimensional chromatography method, and belongs to the technical field of combustion diagnosis and optical testing of internal combustion engines. The control acquisition system is respectively matched with the first high-speed camera and the second high-speed camera to finish acquisition of output signals, transmits the acquired data to the control acquisition system, and finally obtains instantaneous three-dimensional distribution of optical signals in the cylinder through three-dimensional reconstruction; according to the three-dimensional measurement device and method for the optical signals in the optical engine cylinder based on the three-dimensional chromatography, projection data of the optical signals in the cylinder are synchronously obtained through a plurality of side cylinder wall visual angles and a bottom surface visual angle, and three-dimensional distribution of the optical signals in the cylinder is reconstructed by utilizing a three-dimensional chromatography algorithm, so that the spatial resolution is improved, and the measurement accuracy is improved. The measurement precision is enhanced, and accurate combustion process analysis is realized in a high-temperature and high-pressure environment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of combustion diagnosis and optical testing of internal combustion engines, and particularly relates to a three-dimensional measurement device and method for optical signals in an optical engine cylinder based on a three-dimensional tomography method. BACKGROUND

[0002] With the continuous development of internal combustion engine technology, the combustion process, combustion efficiency and emission control have become the focus of research. The engine combustion process is complex and dynamic, involving multiple couplings such as turbulence, chemical reaction and heat transfer, and optimization of combustion performance and reduction of emissions face great challenges. Traditional combustion process analysis mainly relies on gas pressure, temperature measurement and chemical analysis, but these methods are difficult to comprehensively, real-time and accurately capture the flow, flame propagation and free radical distribution in the cylinder.

[0003] In recent years, optical measurement technology has been widely used in internal combustion engine combustion research, such as direct photography, laser-induced fluorescence (LIF), schlieren method, etc., which can be used to observe flame morphology, component concentration and density distribution. However, most of the researches are still limited to two-dimensional imaging, which is limited by the angle of view, and it is difficult to obtain complete three-dimensional information of the combustion process, especially in high temperature, high pressure and complex flow field environment, two-dimensional data is difficult to meet the needs of fine combustion research.

[0004] To overcome the limitations of two-dimensional measurement, three-dimensional tomographic imaging technology has gradually become a research hotspot. Tomographic particle image velocimetry (Tomo-PIV) has been used for three-dimensional flow measurement in engine cylinders, and laser absorption spectroscopy tomography has shown superior performance in combustion temperature and component distribution measurement. However, the existing three-dimensional measurement methods still have problems such as insufficient viewing angle, limited imaging accuracy, high computational complexity, etc., making it difficult to achieve efficient and accurate three-dimensional measurement on an optical engine test bench.

[0005] Therefore, a new multi-view synchronous measurement and computational tomographic reconstruction method is needed to improve the viewing angle coverage, optimize the three-dimensional reconstruction accuracy, and reduce the computational complexity, so that it can be applied to real-time analysis of optical engine combustion process and provide a high-precision three-dimensional testing means for combustion optimization and emission control. SUMMARY

[0006] The purpose of the present application is to provide a three-dimensional measurement device and method for optical signals in an optical engine cylinder based on a three-dimensional tomography method, which synchronously acquires projection data of optical signals in the cylinder through multiple side cylinder wall viewing angles and one bottom surface viewing angle, and reconstructs the three-dimensional distribution of optical signals in the cylinder using a three-dimensional tomographic algorithm, solving the problems of spatial information loss and low measurement accuracy in engine optical measurement of the prior art, improving the spatial resolution and enhancing the measurement accuracy.

[0007] In order to achieve the above object, the application provides a three-dimensional measurement device for optical engine in-cylinder optical signal based on three-dimensional tomography, which comprises a dynamometer, an optical engine crankcase, an angle marker, a control collection system, an oil tank, an oil pump, an oil rail, an ECU, an oil injector, a cylinder pressure sensor, a charge amplifier, a transparent cylinder liner, a transparent piston top, a 45° mirror and a multi-view synchronous imaging system; one end of the optical engine crankcase is connected with the dynamometer, which is used for controlling the rotating speed of the optical engine; the other end of the optical engine crankcase is connected with the angle marker, which transmits the monitored rotating speed data to the control collection system; the oil pump sucks diesel from the oil tank, pressurizes and injects into the oil rail; the ECU monitors the pressure of the oil rail in real time, transmits the data to the control collection system in real time and controls the oil injection time and pulse width of the oil injector; the cylinder pressure sensor is arranged inside the transparent cylinder liner and is used for monitoring the pressure in the transparent cylinder liner in real time; the monitored signal is transmitted to the control collection system through the charge amplifier; the transparent piston top is arranged below the transparent cylinder liner; the 45° mirror is arranged directly below the transparent piston top and is installed on the optical engine bench; the transparent cylinder liner ensures the lateral view angle collection of the in-cylinder optical signal; the transparent piston top and the 45° mirror together ensure the bottom view angle collection of the in-cylinder optical signal; the multi-view synchronous imaging system comprises a first 1 / 4 optical fiber bundle, a second 1 / 4 optical fiber bundle, a first high-speed camera arranged at the output end of the first 1 / 4 optical fiber bundle and a second high-speed camera arranged at the output end of the second 1 / 4 optical fiber bundle.

[0008] Preferably, the first 1 / 4 optical fiber bundle comprises ①, ②, ③ and ④ optical fiber input ends; the ①, ② and ④ optical fiber input ends are arranged to transmit the optical signal data penetrating through one side of the transparent cylinder liner to the optical fiber output ends; the ③ optical fiber input end is arranged to transmit the optical signal data penetrating through the transparent piston top and the 45° mirror to the optical fiber output end; finally, the optical fiber output end signal of the first 1 / 4 optical fiber bundle is collected by the first high-speed camera and the collected data is transmitted to the control collection system.

[0009] Preferably, the second 1 / 4 optical fiber bundle comprises ⑤, ⑥, ⑦ and ⑧ optical fiber input ends; the ⑤, ⑥, ⑦ and ⑧ optical fiber input ends are arranged to transmit the optical signal data of the other side of the transparent cylinder liner to the optical fiber output ends; finally, the optical fiber output end signal of the second 1 / 4 optical fiber bundle is collected by the second high-speed camera and the collected data is transmitted to the control collection system.

[0010] The application further provides a method for the three-dimensional measurement device for optical engine in-cylinder optical signal based on three-dimensional tomography, which comprises the following steps: Step 1, arranging the equipment of the test device; the ③ optical fiber input end is arranged in front of the 45° mirror; the ①, ② and ④ optical fiber input ends are arranged on one side of the transparent cylinder liner; the ⑤, ⑥, ⑦ and ⑧ optical fiber input ends are arranged on the other side of the transparent cylinder liner; Step 2, after the arrangement is completed, install the calibration plate on the calibration fixture to calibrate the input end positions of the first 1 / 4 fiber bundle and the second 1 / 4 fiber bundle; three calibration plate installation positions are provided on the calibration fixture, which are P1, P2 and P3, and the included angle between the calibration plate installation positions P1 and P2 can be observed from the top view to be 120°, and the front surface of the calibration plate needs to be respectively perpendicular to the black mark arrows ① and ② during installation, and the calibration plate installation position P3 can be observed from the bottom view, which is perpendicular to P1 and P2, and the center coincides with the center of the calibration fixture; wherein the outer diameter of the calibration fixture and the transparent sleeve is the same; Step 3, after the calibration is completed, the projection data is collected; Step 4, after the projection data collection is completed, three-dimensional reconstruction is performed to obtain the instantaneous three-dimensional distribution of the in-cylinder optical signal.

[0011] Preferably, the process of step 2 is as follows: S21, remove the transparent sleeve to remove the influence of the curved cylinder wall refraction on the calibration process; S22, install the calibration plate at the P1 position, and shoot the calibration plate projection collected through the fiber input ends ①, ② and ④ in the first 1 / 4 fiber bundle; S23, install the calibration plate at the P2 position, and shoot the calibration plate projection collected through the fiber input ends ⑤, ⑥, ⑦ and ⑧ in the second 1 / 4 fiber bundle; S24, install the calibration plate at the P3 position, and shoot the calibration plate projection collected through the fiber input end ③ in the first 1 / 4 fiber bundle; S25, input the collected eight calibration plate projections into the image calibration program for calculation to obtain the object-image ratio of the virtual imaging system m , focal length f , relative distance parameters of the fiber input ends ①-⑧ , relative azimuth angle parameter and relative pitch angle parameter ; S26, according to the relative position relationship of the three calibration plate installation positions, unify the coordinate system of the calibration parameters to obtain the relative distance parameters of the fiber bundle input ends , relative azimuth angle parameter and relative pitch angle parameter .

[0012] Preferably, step 3 is as follows: First, the injection pressure, injection timing, injection pulse width, and camera trigger timing are set through the ECU electronic control unit, and the rotational speed of the optical engine is set using an electric dynamometer. At the same time, the shooting parameters of the first high-speed camera and the second high-speed camera are configured in the operation interface of the control and acquisition system. After the parameters are set, the electric dynamometer is started to reverse-drive the optical engine. When the engine reaches a steady-state speed, the injection is started through the ECU electronic control unit, and the first high-speed camera and the second high-speed camera are triggered to shoot simultaneously. After receiving the trigger signal, the first high-speed camera and the second high-speed camera simultaneously acquire optical signal projection data from 7 side views and 1 bottom view.

[0013] Preferably, step 4 is performed as follows: S41. Based on the calibration results of step 2, input the relative position information of the 8 fiber optic input ends into the tomography algorithm. S42. The point diffusion matrix is ​​calculated using a three-dimensional cross-interface tomography algorithm to calculate the point diffusion matrix of the seven light signals collected through the transparent cylinder liner and to correct the refractive distortion. S43. The point diffusion matrix of a light signal projected through the top of a transparent piston is directly calculated using a three-dimensional tomography algorithm. S44. Arrange the point diffusion matrices of the 8 fiber input ends in columns to obtain the total point diffusion matrix P. Input the 8 projection data and the calculated 8 point diffusion matrices P into the algebraic iterative reconstruction algorithm, perform multiple iterative calculations, optimize the three-dimensional reconstruction result of the optical signal, and obtain the instantaneous three-dimensional distribution of the in-cylinder optical signal.

[0014] Preferably, the process of S42 is as follows: S421, when the calibration board B The light emitted from a point, at the point B After being refracted by the inner wall of the transparent cylinder liner at two points, B One point is refracted again by the transparent cylinder liner outer wall, passing through the virtual imaging center point. C Ultimately, it was on the camera chip. Point acquisition, calculation of light rays angle of incidence The calculation expression is as follows: (1); in, Indicates that the outer cylinder wall of the transparent cylinder liner is in B The normal vector at point 1; S422. Calculate the ray according to Snell's law of refraction. angle of departure The calculation expression is as follows: (2); in, and These represent the refractive indices of air and transparent cylinder liners, respectively. S423, Calculate the light rays As it continues to move forward, it interacts with the inner cylinder wall of the transparent cylinder liner. B Angle of incidence at point 2 and the angle of departure The calculation expression is as follows: (3); (4); in, Indicates the inner cylinder wall of the transparent cylinder liner. B The normal vector at point 2; S424. Divide the three-dimensional space inside the transparent cylinder liner into several cubic voxel micro-elements. According to the calculation process of Equation 1-4, obtain the point-to-point mapping position of each voxel on the camera chip. Then, calculate the pixel range occupied by the voxel on the camera chip according to the object-to-image ratio of the imaging system and the focal length. Define the imaging weight of each pixel within the pixel range according to the Gaussian distribution to obtain the point diffusion relationship of the voxel to the pixels on the camera chip. Perform the above calculation on all voxels to obtain the point diffusion matrices of the seven fiber input ends ①, ②, ④, ⑤, ⑥, ⑦, and ⑧ affected by refraction: P1, P2, P4, P5, P6, P7, and P8.

[0015] Preferably, the process of S43 is as follows: S431. Under conditions unaffected by the refraction of the transparent cylinder liner, the voxels inside the transparent cylinder liner ( X , Y , Z The corresponding pixel position on the camera chip () x , z According to the calibrated distance of the imaging system d Azimuth θ and pitch angle φ The calculation is as follows: (5); S432. Divide the three-dimensional space inside the transparent cylinder liner into several cubic voxel micro-elements. According to the calculation process of Equation 5, obtain the point-to-point mapping position of each voxel on the camera chip. Then, calculate the pixel range occupied by the voxel on the camera chip according to the object-to-image ratio and focal length of the imaging system. Define the imaging weight of each pixel within the pixel range according to the Gaussian distribution to obtain the point diffusion relationship of the voxel to the pixels on the camera chip. Perform the above calculation on all voxels to obtain the point diffusion matrix of the fiber input end ③ that is not affected by refraction: P3.

[0016] Preferably, the process of S44 is as follows: S441, the two-dimensional projection matrix collected through the 8 optical fiber input ends Arranged by column S442, the projection and the corresponding point spread matrix Input algebraic iterative reconstruction method, initialize the three-dimensional light signal distribution F in the transparent sleeve 0 Matrix, initialized to a 0 matrix or a uniform matrix; according to the point spread matrix , the simulation projection of the current three-dimensional light signal distribution is calculated, and the calculation expression is as follows: (6); S443, calculate the projection error e n The calculation expression is as follows: (7); S444, iterative optimization is performed on the current three-dimensional light signal distribution, and the expression is as follows: (8); Wherein, lambda is a relaxation factor, used to control the amplitude of optimization, to avoid iteration not convergent; S445, judge Whether it is less than the error threshold or the iteration step Whether the step size is greater than the upper limit, if not, return to S442 to continue to calculate the simulation projection according to the current three-dimensional signal distribution; if yes, end the iteration and output the reconstruction result The three-dimensional reconstruction of the instantaneous light signal in the cylinder is completed.

[0017] Therefore, the optical engine in-cylinder optical signal three-dimensional measurement device and method based on the three-dimensional tomography method has the following beneficial effects: (1) The optical engine in-cylinder optical signal measurement method based on three-dimensional tomography provided by the present application realizes high-precision three-dimensional measurement of in-cylinder optical signals by combining multi-view synchronous imaging technology with computational tomographic reconstruction technology; 7 side views and 1 bottom view are used to obtain optical projection data, breaking through the limitation of traditional two-dimensional measurement and improving the spatial resolution of the combustion process, so that the key information such as in-cylinder combustion flame structure and free radical distribution can be accurately reconstructed in three-dimensional form; (2) The present application adopts three-dimensional cross-interface tomographic algorithm for refraction correction, and combines algebraic iterative reconstruction algorithm to optimize the three-dimensional reconstruction process, so as to improve the measurement accuracy; the point spread matrix is calculated to correct the refraction effect, so that the optical signal can more accurately restore the real combustion state in the cylinder; compared with the traditional three-dimensional tomographic method, the present application improves the reconstruction accuracy and reduces the error accumulation caused by refraction effect; ​(3) The application utilizes an ECU electric control unit to control engine speed, and synchronously sets injection pressure, injection time, injection pulse width and camera trigger time, so as to realize precise synchronization of an optical measurement system and an engine combustion process; in combination with a high-pressure common rail fuel injection system and an electric dynamometer, the application ensures time sequence consistency of each visual angle data, avoids data mismatching problems caused by rapid changes of the combustion process, and improves time-space consistency of three-dimensional measurement results; (4) The application has strong applicability, can be compatible with various optical signals, including flame spontaneous emission signals and laser-induced fluorescence (LIF) signals, and is suitable for optical engine experimental researches of different types; the method can be widely applied to engine combustion optimization, low-emission combustion technology development and combustion mechanism research, and provides precise experimental data support for development of high-efficiency and low-pollution engine technologies.

[0018] The technical solutions of the application will be further described in detail below with the aid of drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 FIG. 1 is a structural schematic view of an optical engine in-cylinder optical signal three-dimensional measurement device based on a three-dimensional tomography method according to the application; Figure 2 FIG. 2 is a light path top view of a multi-view angle synchronous imaging system according to an embodiment of the application; Figure 3 FIG. 3 is a schematic view of a calibration fixture according to an embodiment of the application; Figure 4 FIG. 4 is a flowchart of projection data acquisition according to an embodiment of the application; Figure 5 FIG. 5 is a flowchart of three-dimensional reconstruction according to an embodiment of the application; Figure 6 FIG. 6 is a schematic view of calculation of a point spread matrix by a three-dimensional cross-interface tomography algorithm according to an embodiment of the application; Figure 7 FIG. 7 is a flowchart of calculation of an algebraic iterative reconstruction method according to an embodiment of the application; Figure 8 FIG. 8 is an instantaneous reconstruction result diagram under different crankshaft rotation angles according to an embodiment of the application; REFERENCE SIGNS 1, electric dynamometer; 2, optical engine crankcase; 3, angle gauge; 4, control and acquisition system; 5, oil tank; 6, oil pump; 7, oil rail; 8, ECU electric control unit; 9, fuel injector; 10, cylinder pressure sensor; 11, charge amplifier; 12, transparent cylinder liner; 13, transparent piston top; 14, 45° mirror; 15, first 1 / 4 optical fiber bundle; 16, first high-speed camera; 17, second 1 / 4 optical fiber bundle; 18, second high-speed camera. DETAILED DESCRIPTION

[0020] The following detailed description of embodiments of the application provided in the accompanying drawings is not intended to limit the scope of the application as claimed, but merely represents selected embodiments of the application. Based upon the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present application.

[0021] Please refer to Figures 1-2 , the three-dimensional optical signal three-dimensional measurement device of optical engine in-cylinder based on three-dimensional tomography includes electric power dynamometer 1, optical engine crankcase 2, angle marker 3, control acquisition system 4, oil tank 5, oil pump 6, oil rail 7, ECU electric control unit 8, oil injector 9, cylinder pressure sensor 10, charge amplifier 11, transparent cylinder liner 12, transparent piston top 13, 45° mirror 14 and multi-view synchronous imaging system;One end of the optical engine crankcase 2 is connected with the electric power dynamometer 1, which is used to control the speed of the optical engine, the other end of the optical engine crankcase 2 is connected with the angle marker 3, and the monitored speed data is transmitted to the control acquisition system 4;The oil pump 6 sucks diesel oil from the oil tank 5, pressurizes and injects it into the oil rail 7, the ECU electric control unit 8 monitors the pressure of the oil rail 7 in real time, transmits the data to the control acquisition system 4 in real time, and controls the oil injection time and pulse width of the oil injector 9;The cylinder pressure sensor 10 is arranged inside the transparent cylinder liner 12, which is used to monitor the pressure in the transparent cylinder liner 12 in real time, and the monitored signal is transmitted to the control acquisition system 4 through the charge amplifier 11;The transparent piston top 13 is arranged below the transparent cylinder liner 12, the 45° mirror 14 is arranged directly below the transparent piston top 13, and is installed on the optical engine bench;The transparent cylinder liner 12 ensures the side view angle collection of the in-cylinder light signal, and the transparent piston top 13 and the 45° mirror 14 together ensure the bottom view angle collection of the in-cylinder light signal;The multi-view synchronous imaging system includes first 1 / 4 optical fiber bundle 15, second 1 / 4 optical fiber bundle 17, first high-speed camera 16 arranged at the output end of the first 1 / 4 optical fiber bundle 15 and second high-speed camera 18 arranged at the output end of the second 1 / 4 optical fiber bundle 17;Among them, the first 1 / 4 optical fiber bundle 15 includes ①, ②, ③ and ④ optical fiber input ends, wherein ①, ② and ④ optical fiber input ends are arranged to transmit light signal data through one side of the transparent cylinder liner 12 to the optical fiber output end;The ③ optical fiber input end is arranged to transmit the light signal data through the transparent piston top 13 and the 45° mirror 14 to the optical fiber output end;Finally, the optical fiber output end signal of the first 1 / 4 optical fiber bundle 15 is collected by the first high-speed camera 16, and the collected data is transmitted to the control acquisition system 4;The second 1 / 4 optical fiber bundle 17 includes ⑤, ⑥, ⑦ and ⑧ optical fiber input ends, wherein ⑤, ⑥, ⑦ and ⑧ optical fiber input ends are arranged to transmit light signal data of the other side of the transparent cylinder liner 12 to the optical fiber output end, and finally the optical fiber output end signal of the second 1 / 4 optical fiber bundle 17 is collected by the second high-speed camera 18, and the collected data is transmitted to the control acquisition system 4.

[0022] A method for a three-dimensional measurement device for in-cylinder optical signals of an optical engine based on three-dimensional tomography includes the following steps: Step 1: Arrange the equipment of the testing device; fiber optic input end ③ is set in front of the 45° reflector, fiber optic input ends ①, ② and ④ are set on one side of the transparent cylinder sleeve, and fiber optic input ends ⑤, ⑥, ⑦ and ⑧ are set on the other side of the transparent cylinder sleeve. Step 2: After the setup is complete, install the calibration plate using calibration clamps, such as... Figure 3 As shown, the input positions of the first 1 / 4 fiber optic bundle and the second 1 / 4 fiber optic bundle are calibrated. The calibration fixture has three calibration plate mounting positions, P1, P2, and P3. From a top viewpoint, the angle between calibration plate mounting positions P1 and P2 is 120°. When installing the calibration plates, the front faces the black arrows ① and ② respectively. From a bottom viewpoint, calibration plate mounting position P3 is perpendicular to P1 and P2, and its center coincides with the center of the calibration fixture. The calibration fixture and the transparent cylinder liner have the same outer diameter. The specific process is as follows: S21. Remove the transparent cylinder liner to eliminate the influence of the curved cylinder wall refraction on the calibration process; S22. Install the calibration board at position P1 and take pictures of the calibration board projections collected through the fiber input ends ①, ②, and ④ in the first 1-to-4 fiber bundle. S23. Install the calibration board at position P2 and take pictures of the calibration board projections collected through the fiber input ends ⑤, ⑥, ⑦, and ⑧ in the second 1-to-4 fiber bundle. S24. Install the calibration board at position P3 and take a picture of the calibration board projection collected through the fiber input end ③ in the first 1-to-4 fiber bundle. S25. The eight calibration plates collected are projected into the image calibration program for calculation to obtain the object-to-image ratio of the virtual imaging system. m ,focal length f And the relative distance parameters of fiber optic input ends ①~⑧ Relative azimuth angle parameter and relative pitch angle parameters ; S26. Based on the relative positional relationship of the three calibration plates, unify the calibration parameters into a coordinate system to obtain the relative distance parameters of the fiber optic bundle input end after calibration. Relative azimuth angle parameter Relative pitch angle parameter .

[0023] Step 3: After calibration, collect the projection data, such as... Figure 4The specific process is as follows: first, set the injection pressure, injection time, injection pulse width and camera trigger time through the ECU, set the speed of the optical engine using the electric dynamometer, and configure the shooting parameters of the shooting frame rate and exposure time of the first high-speed camera and the second high-speed camera in the operation interface in the control collection system; after the parameter setting is completed, start the electric dynamometer to drag the optical engine, and when the engine reaches a steady speed, start injection through the ECU, and trigger the first high-speed camera and the second high-speed camera to shoot at the same time, and the first high-speed camera and the second high-speed camera receive the trigger signal and collect optical signal projection data of 7 side angles and 1 bottom angle at the same time.

[0024] Step 4, after the projection data collection is completed, three-dimensional reconstruction is performed, as shown in Figure 5 , the instantaneous three-dimensional distribution of the optical signal in the cylinder is obtained; the specific process is as follows: S41, according to the calibration result of step 2, the relative position information of the 8 optical fiber input ends is input to the tomography algorithm; S42, the three-dimensional cross-interface tomography algorithm is used to calculate the point spread matrix of the light signal projection collected through the transparent cylinder liner, and the refraction distortion is corrected; as shown in Figure 6 , a calibration plate is arranged at the center layer position of the cylinder liner as a signal source to facilitate the description of the subsequent calculation process. First, a Cartesian right-handed coordinate system is established in the internal space of the cylinder liner, the coordinate origin O is located at the center of the internal space of the cylinder liner, X the axis direction is parallel to the plane of the calibration plate, Y the axis direction is perpendicular to the plane of the calibration plate, Z the axis direction is perpendicular to O - XY the plane upward. Point C is the center point of the virtual imaging system, o is the center point position of the camera chip, and the coordinate system is o - xz , the dashed line OCo marks the optical axis. The position of the optical axis is determined by the distance d = Oo , the azimuth angle θ (the angle between the projection of the optical axis on the O - XY axis and the X axis), and the pitch angle φ (the angle between the optical axis and the Y axis). The specific process is as follows: S421, when the light emitted by the point B on the calibration plate is refracted by the inner wall of the transparent cylinder liner, it is refracted at point B 2, and the refracted light is collected by the first high-speed camera and the second high-speed camera at point BOne point is refracted again by the outer wall of the transparent cylinder liner, and finally seen by the camera chip through the virtual imaging center point C. Point-based acquisition, then based on the reversibility of the optical path, then... The point is emitted through the virtual imaging center point C The light will pass through B Therefore, to conserve computational resources, the reverse ray tracing method is used to calculate the point spread matrix of the projected light signal affected by refraction; the ray tracing method is then used to calculate the point spread matrix of the projected light signal affected by refraction. angle of incidence The calculation expression is as follows: (1); in, Indicates that the outer cylinder wall of the transparent cylinder liner is in B The normal vector at point 1; S422. Calculate the ray according to Snell's law of refraction. angle of departure The calculation expression is as follows: (2); in, and These represent the refractive indices of air and transparent cylinder liners, respectively. S423, Calculate the light rays As it continues to move forward, it interacts with the inner cylinder wall of the transparent cylinder liner. B Angle of incidence at point 2 and the angle of departure The calculation expression is as follows: (3); (4); in, Indicates the inner cylinder wall of the transparent cylinder liner. B The normal vector at point 2; S424. Divide the three-dimensional space inside the transparent cylinder liner into several cubic voxel micro-elements. According to the calculation process of Equation 1-4, obtain the point-to-point mapping position of each voxel on the camera chip. Then, calculate the pixel range occupied by the voxel on the camera chip according to the object-to-image ratio of the imaging system and the focal length. Define the imaging weight of each pixel within the pixel range according to the Gaussian distribution to obtain the point diffusion relationship of the voxel to the pixels on the camera chip. Perform the above calculation on all voxels to obtain the point diffusion matrices of the seven fiber input ends ①, ②, ④, ⑤, ⑥, ⑦, and ⑧ affected by refraction: P1, P2, P4, P5, P6, P7, and P8.

[0025] S43. The point diffusion matrix of a light signal projected through the top of a transparent piston is directly calculated using a three-dimensional tomography algorithm; the specific process is as follows: S431. Under conditions unaffected by the refraction of the transparent cylinder liner, the voxels inside the transparent cylinder liner ( X , Y , Z The corresponding pixel position on the camera chip () x , z According to the calibrated distance of the imaging system d Azimuth θ and pitch angle φ The calculation is as follows: (5); S432. Divide the three-dimensional space inside the transparent cylinder liner into several cubic voxel micro-elements. According to the calculation process of Equation 5, obtain the point-to-point mapping position of each voxel on the camera chip. Then, calculate the pixel range occupied by the voxel on the camera chip according to the object-to-image ratio and focal length of the imaging system. Define the imaging weight of each pixel within the pixel range according to the Gaussian distribution to obtain the point diffusion relationship of the voxel to the pixels on the camera chip. Perform the above calculation on all voxels to obtain the point diffusion matrix of the fiber input end ③ that is not affected by refraction: P3.

[0026] S44. Arrange the point spread matrices of the eight fiber input ends column-wise to obtain the total point spread matrix P. Input the eight projection data and the calculated eight point spread matrices P into the algebraic iterative reconstruction algorithm, perform multiple iterative calculations, optimize the three-dimensional reconstruction result of the optical signal, and obtain the instantaneous three-dimensional distribution of the in-cylinder optical signal, such as... Figure 7 As shown; the specific process is as follows: S441, The two-dimensional projection matrix acquired through 8 fiber optic input terminals Arranged in columns ; S442, Project and the corresponding point spread matrix Input algebraic iterative reconstruction method to initialize the three-dimensional optical signal distribution F inside the transparent cylinder liner. 0 The matrix is ​​initialized to either a zero matrix or a uniform matrix. Based on the point spread matrix P, the simulated projection of the current 3D light signal distribution is calculated using the following expression: (6); S443, Calculate the projection error e n The calculation expression is as follows: (7); S444. Iteratively optimize the current three-dimensional light signal distribution, as shown in the following expression: (8); Where λ is the relaxation factor, used to control the magnitude of optimization and avoid iteration non-convergence; S445, judging whether less than the error threshold or the iteration step number n is greater than the step upper limit, if not, return to S442 to continue calculating the simulated projection according to the current three-dimensional signal distribution; if yes, end the iteration and output the reconstruction result , complete the three-dimensional reconstruction of the in-cylinder instantaneous light signal.

[0027] This example gives the instantaneous reconstruction results at different crank angles under the engine speed of 800 rpm and the injection pressures of 60 / 100 / 140 MPa, as shown in Figure 8 .

[0028] Therefore, the optical engine in-cylinder optical signal three-dimensional measurement device and method based on the three-dimensional tomography method are adopted, the projection data of the in-cylinder optical signal is synchronously acquired through multiple side cylinder wall angles and one bottom surface angle, and the three-dimensional distribution of the in-cylinder optical signal is reconstructed by using the three-dimensional tomography algorithm, so that the spatial resolution is improved, the measurement accuracy is enhanced, and the accurate combustion process analysis can be realized under the high-temperature and high-pressure environment.

[0029] Finally, it should be noted that: the above examples 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 preferred embodiments, those skilled in the art should understand that: it can still modify or equivalently replace the technical solutions of the present application, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A device for three-dimensional measurement of optical signals in the cylinder of an optical engine based on three-dimensional tomography, characterised in that: It includes an electric dynamometer, an optical engine crankcase, a protractor, a control and acquisition system, a fuel tank, a fuel pump, a fuel rail, an ECU (Electronic Control Unit), fuel injectors, a cylinder pressure sensor, a charge amplifier, a transparent cylinder liner, a transparent piston top, a 45° reflector, and a multi-view synchronous imaging system. One end of the optical engine crankcase is connected to the electric dynamometer to control the speed of the optical engine, and the other end of the optical engine crankcase is connected to the protractor to transmit the monitored speed data to the control and acquisition system. The fuel pump draws diesel fuel from the fuel tank, pressurizes it, and injects it into the fuel rail. The ECU (Electronic Control Unit) monitors the fuel rail pressure in real time, transmits the data to the control and acquisition system, and controls the injection timing and pulse width of the injectors. The cylinder pressure sensor is located inside the transparent cylinder liner to monitor the pressure inside the transparent cylinder liner in real time. The monitored signal is transmitted to the control and acquisition system via a charge amplifier. The transparent piston top is located below the transparent cylinder liner, and a 45° reflector is located directly below the transparent piston top and mounted on an optical engine test bench. The transparent cylinder liner ensures the side-view acquisition of the in-cylinder light signal, while the transparent piston top and the 45° reflector together ensure the bottom-view acquisition of the in-cylinder light signal. The multi-view synchronous imaging system includes a first 1:4 splitter fiber optic bundle, a second 1:4 splitter fiber optic bundle, a first high-speed camera located at the output end of the first 1:4 splitter fiber optic bundle, and a second high-speed camera located at the output end of the second 1:4 splitter fiber optic bundle.

2. The optical engine in-cylinder optical signal three-dimensional measurement device based on three-dimensional tomography according to claim 1, characterized in that: The first 1-to-4 fiber optic bundle includes fiber input terminals ①, ②, ③, and ④. Fiber input terminals ①, ②, and ④ are configured to transmit optical signal data transmitted through the transparent cylinder sleeve on one side to its fiber output terminal. Fiber input terminal ③ is configured to transmit optical signal data transmitted through the transparent piston top and the 45° reflector to its fiber output terminal. Finally, the signal from the fiber output terminal of the first 1-to-4 fiber optic bundle is acquired by the first high-speed camera, and the acquired data is transmitted to the control acquisition system.

3. The optical engine in-cylinder optical signal three-dimensional measurement device based on three-dimensional tomography according to claim 1, characterized in that: The second 1-to-4 fiber optic bundle includes fiber input terminals ⑤, ⑥, ⑦, and ⑧. Fiber input terminals ⑤, ⑥, ⑦, and ⑧ are configured to transmit optical signal data from the transparent cylinder sleeve on the other side to its fiber output terminal. Finally, the signal from the fiber output terminal of the second 1-to-4 fiber optic bundle is acquired by the second high-speed camera, and the acquired data is transmitted to the control acquisition system.

4. A method of three-dimensional measurement of optical signals in the cylinder of an optical engine based on three-dimensional tomography according to any one of claims 1 to 3, characterized in that, Includes the following steps: Step 1: Arrange the equipment of the testing device; fiber optic input end ③ is set in front of the 45° reflector, fiber optic input ends ①, ② and ④ are set on one side of the transparent cylinder sleeve, and fiber optic input ends ⑤, ⑥, ⑦ and ⑧ are set on the other side of the transparent cylinder sleeve. Step 2: After the setup is completed, a calibration fixture is used to install the calibration plate to calibrate the input end positions of the first 1 / 4 fiber optic bundle and the second 1 / 4 fiber optic bundle. The calibration fixture has three calibration plate installation positions: P1, P2, and P3. From a top viewpoint, the angle between calibration plate installation positions P1 and P2 is 120°. From a bottom viewpoint, calibration plate installation position P3 is perpendicular to P1 and P2, and its center coincides with the center of the calibration fixture. The calibration fixture and the transparent cylinder liner have the same outer diameter. Step 3: After calibration, collect the projection data; Step 4: After the projection data acquisition is completed, perform three-dimensional reconstruction to obtain the instantaneous three-dimensional distribution of the in-cylinder optical signal.

5. The method of three-dimensional tomography based optical engine in-cylinder optical signal three-dimensional measurement apparatus according to claim 4, characterized in that, Step 2 is as follows: S21. Remove the transparent cylinder liner to eliminate the influence of the curved cylinder wall refraction on the calibration process; S22. Install the calibration board at position P1 and take pictures of the calibration board projections collected through the fiber input ends ①, ②, and ④ in the first 1-to-4 fiber bundle. S23. Install the calibration board at position P2 and take pictures of the calibration board projections collected through the fiber input ends ⑤, ⑥, ⑦, and ⑧ in the second 1-to-4 fiber bundle. S24. Install the calibration board at position P3 and take a picture of the calibration board projection collected through the fiber input end ③ in the first 1-to-4 fiber bundle. S25, the collected 8 calibration board projection input to the image calibration program for calculation, obtain the virtual imaging system of object image ratio m , focal length f , and the relative distance parameters of the input end of the optical fiber ① ~ ⑧ , the relative azimuth angle parameter and the relative pitch angle parameter ; S26, according to the relative position relationship of the three calibration board installation positions, the calibration parameters are uniformly coordinated to obtain the relative distance parameters of the input end of the optical fiber bundle after calibration , the relative azimuth angle parameters , the relative pitch angle parameters .

6. The method of three-dimensional tomography based optical engine in-cylinder optical signal three-dimensional measurement apparatus according to claim 5, characterized in that, Step 3 is as follows: First, the injection pressure, injection timing, injection pulse width, and camera trigger timing are set through the ECU electronic control unit, and the rotational speed of the optical engine is set using an electric dynamometer. At the same time, the shooting parameters of the first high-speed camera and the second high-speed camera are configured in the operation interface of the control and acquisition system. After the parameters are set, the electric dynamometer is started to reverse-drive the optical engine. When the engine reaches a steady-state speed, the injection is started through the ECU electronic control unit, and the first high-speed camera and the second high-speed camera are triggered to shoot simultaneously. After receiving the trigger signal, the first high-speed camera and the second high-speed camera simultaneously acquire optical signal projection data from 7 side views and 1 bottom view.

7. The method of three-dimensional tomography based optical engine in-cylinder optical signal three-dimensional measurement apparatus according to claim 6, characterized in that, Step 4 is as follows: S41. Based on the calibration results of step 2, input the relative position information of the 8 fiber optic input ends into the tomography algorithm. S42. The point diffusion matrix is ​​calculated using a three-dimensional cross-interface tomography algorithm to calculate the point diffusion matrix of the seven light signals collected through the transparent cylinder liner and to correct the refractive distortion. S43. The point diffusion matrix of a light signal projected through the top of a transparent piston is directly calculated using a three-dimensional tomography algorithm. S44. Arrange the point diffusion matrices of the 8 fiber input ends in columns to obtain the total point diffusion matrix P. Input the 8 projection data and the calculated 8 point diffusion matrices P into the algebraic iterative reconstruction algorithm, perform multiple iterative calculations, optimize the three-dimensional reconstruction result of the optical signal, and obtain the instantaneous three-dimensional distribution of the in-cylinder optical signal.

8. The method for three-dimensional measurement of in-cylinder optical signals of an optical engine based on three-dimensional tomography according to claim 7, characterized in that, The process of S42 is as follows: S421, when the calibration board B The light emitted from a point, at the point B After being refracted by the inner wall of the transparent cylinder liner at two points, B One point is refracted again by the transparent cylinder liner outer wall, passing through the virtual imaging center point. C Ultimately, it was on the camera chip. Point acquisition, calculation of light rays angle of incidence The calculation expression is as follows: (1)； in, Indicates that the outer cylinder wall of the transparent cylinder liner is in B The normal vector at point 1; S422. Calculate the ray according to Snell's law of refraction. angle of departure The calculation expression is as follows: (2)； in, and These represent the refractive indices of air and transparent cylinder liners, respectively. S423, Calculate the light rays As it continues to move forward, it interacts with the inner cylinder wall of the transparent cylinder liner. B Angle of incidence at point 2 and the angle of departure The calculation expression is as follows: (3)； (4)； in, Indicates the inner cylinder wall of the transparent cylinder liner. B The normal vector at point 2; S424. Divide the three-dimensional space inside the transparent cylinder liner into several cubic voxel micro-elements. According to the calculation process of Equation 1-4, obtain the point-to-point mapping position of each voxel on the camera chip. Then, calculate the pixel range occupied by the voxel on the camera chip according to the object-to-image ratio of the imaging system and the focal length. Define the imaging weight of each pixel within the pixel range according to the Gaussian distribution to obtain the point diffusion relationship of the voxel to the pixels on the camera chip. Perform the above calculation on all voxels to obtain the point diffusion matrices of the seven fiber input ends ①, ②, ④, ⑤, ⑥, ⑦, and ⑧ affected by refraction: P1, P2, P4, P5, P6, P7, and P8.

9. The method for three-dimensional measurement of in-cylinder optical signals of an optical engine based on three-dimensional tomography according to claim 8, characterized in that, The process of S43 is as follows: S431. Under conditions unaffected by the refraction of the transparent cylinder liner, the voxels inside the transparent cylinder liner ( X , Y , Z The corresponding pixel position on the camera chip () x , z According to the calibrated distance of the imaging system d Azimuth θ and pitch angle φ The calculation is as follows: (5)； S432. Divide the three-dimensional space inside the transparent cylinder liner into several cubic voxel elements. According to the calculation process of Equation 5, obtain the point-to-point mapping position of each voxel on the camera chip. Then, calculate the pixel range occupied by the voxel on the camera chip according to the object-to-image ratio and focal length of the imaging system. Define the imaging weight of each pixel within the pixel range according to the Gaussian distribution to obtain the point diffusion relationship of the voxel to the pixels on the camera chip. Perform the above calculation on all voxels to obtain the point diffusion matrix of the fiber input end ③, which is not affected by refraction. .

10. The method for three-dimensional measurement of in-cylinder optical signals of an optical engine based on three-dimensional tomography according to claim 9, characterized in that, The process of S44 is as follows: S441, The two-dimensional projection matrix acquired through 8 fiber optic input terminals Arranged in columns ; S442, Project and the corresponding point spread matrix Input algebraic iterative reconstruction method to initialize the three-dimensional optical signal distribution inside the transparent cylinder liner. The matrix is ​​initialized to a zero matrix or a uniform matrix. Based on the point diffusion matrix The simulated projection of the current three-dimensional light signal distribution is calculated using the following expression: (6)； S443, Calculate projection error The calculation expression is as follows: (7)； S444. Iteratively optimize the current three-dimensional light signal distribution, as shown in the following expression: (8)； Where λ is the relaxation factor; S445, Judgment Is it less than the error threshold or the number of iterations? If the step size is greater than the upper limit, return to S442 to continue calculating the simulated projection based on the current 3D signal distribution; if it is, end the iteration and output the reconstruction result. This completes the three-dimensional reconstruction of the instantaneous optical signal inside the cylinder.

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