Two-dimensional CMC surface infrared temperature measurement angle calibration and heat exchange coefficient correction method

Abstract

The invention discloses a two-dimensional CMC surface infrared temperature measurement angle calibration and heat exchange coefficient correction method, and the method comprises the steps: building a coupling correction model between an imaging angle and a temperature deviation based on the protruding and recessed geometric features of a surface weaving texture, and carrying out the system comparison of infrared temperature measurement results at different visual angles and the actual measurement temperature of a thermocouple, the infrared correction formula considering the surface height and the observation angle is obtained through fitting, quantitative temperature correction of a non-vertical imaging area is achieved, temperature distortion caused by infrared temperature measurement in a complex morphology area can be effectively eliminated, and the temperature measurement precision of infrared thermal imaging on the complex CMC surface is remarkably improved. On the basis of the corrected real temperature field, a transient thermal response inversion method is combined, and more accurate local convective heat transfer coefficient distribution is obtained. The method has relatively high measurement reliability and spatial resolution capability in a CMC turbine blade area with remarkable geometric fluctuation on the surface.

Description

Technical Field

[0001] This invention relates to the field of heat transfer testing and infrared temperature measurement accuracy correction for high-temperature components of aero-engines, and particularly to a method for calibrating the angle and correcting the heat transfer coefficient of infrared temperature measurement on a two-dimensional CMC surface. Background Technology

[0002] With the continuous development of advanced aero-engines and hypersonic vehicles, the service temperatures of their hot-end components (especially high-pressure turbine guide vanes and moving blades) have approached or exceeded the performance limits of high-temperature metal alloys. Ceramic matrix composites (CMCs), with their excellent high-temperature mechanical properties, low density, and oxidation resistance, are considered to be a new generation of high-temperature structural materials that can significantly improve engine thermal efficiency and thrust-to-weight ratio.

[0003] However, the weaving-densification molding processes of CMC materials (such as two-dimensional weaving, chemical vapor infiltration, and polymer infiltration ablation) create a periodically undulating woven morphology on its surface. Unlike the smooth surface of traditional metal blades, the CMC surface is composed of protrusions and depressions caused by interlaced fiber bundles, uneven matrix filling, and localized spalling. This complex morphology significantly affects the accuracy of infrared thermography measurements in heat transfer testing.

[0004] Infrared thermal imaging, as a non-contact temperature measurement technique, is widely used in the study of heat transfer characteristics on blade surfaces. However, when there are significant geometric undulations on the blade surface, the infrared imaging angle changes due to local surface tilt, leading to systematic biases in temperature measurement results. This is particularly true on two-dimensional woven CMC surfaces, where the normal directions of concave and convex areas are inconsistent with the infrared imaging direction, causing distorted infrared temperature measurement signals and resulting in misjudgments of temperature distribution and errors in heat transfer coefficient retrieval.

[0005] Existing studies mostly employ infrared imaging methods with fixed angles or vertical viewing angles, neglecting the influence of surface geometry on the temperature measurement perspective. Some studies have attempted to improve temperature measurement accuracy through overall angle correction or empirical calibration, but it remains difficult to quantitatively correct for local uneven regions under complex woven textures. Furthermore, traditional infrared thermometry and heat transfer inversion methods do not consider the coupling effect of local normal deviation and height changes, leading to significant errors in the calculation of heat transfer coefficients in areas with significant surface undulations.

[0006] Therefore, there is an urgent need to propose a temperature measurement correction method that can identify surface geometric features and combine the relationship between infrared imaging angle and local normal. Summary of the Invention

[0007] This invention provides a method for calibrating the infrared temperature measurement angle and correcting the heat transfer coefficient on two-dimensional CMC surfaces. This method addresses the problems of viewing angle distortion, local temperature measurement deviation, and the resulting errors in heat transfer coefficient calculation in existing infrared thermal imaging on CMC surfaces with woven textures. By establishing a quantitative relationship between surface geometry and infrared imaging angle, it achieves accurate correction of infrared temperature measurement errors in concave and convective regions, thereby obtaining a more realistic surface temperature distribution and local convective heat transfer coefficient. This provides reliable experimental support for the study of flow heat transfer mechanisms and cooling design of high-temperature components such as aero-engine turbine blades.

[0008] This invention provides a method for calibrating the angle and correcting the heat transfer coefficient of infrared thermometry on a two-dimensional CMC surface, comprising the following steps: Step 1: Use a laser confocal microscope to scan the surface of the two-dimensional braided ceramic matrix composite test blade to identify the geometric features of the surface protrusions and depressions. Step 2: Based on the angle relationship between the local normal and the overall normal of the blade obtained from the geometric features, select multiple imaging angles and use an infrared thermal imager to perform multi-angle transient imaging of the surface of the two-dimensional braided ceramic matrix composite test blade. At the same time, the true surface temperature of the two-dimensional braided ceramic matrix composite test blade is measured synchronously through an embedded thermocouple. Step 3: Based on the difference between the infrared temperature and the actual surface temperature of the thermocouple under different imaging angles, analyze the influence of the imaging angle change on the temperature measurement deviation, and obtain the infrared temperature measurement angle calibration formula by fitting. Step 4: Use the infrared angle calibration formula to perform pixel correction on the infrared temperature field to obtain the true temperature distribution on the surface of the two-dimensional braided ceramic matrix composite test blade. Based on the corrected infrared temperature field, calculate the local convective heat transfer coefficient and Nusselt number distribution through transient thermal response.

[0009] Optionally, in one embodiment of the present invention, in step 1, the geometric features of the surface protrusions and depressions include the difference in texture height and the local normal angle, the surface texture height ranges from 0.2 mm to 0.6 mm, and the difference in the normal angle between the depression area and the protrusion area is between 0° and 40°.

[0010] Optionally, in one embodiment of the present invention, in step 2, the shooting angle range of the infrared thermal imager is 30° to 90°.

[0011] Optionally, in one embodiment of the present invention, in step 3, the infrared temperature measurement angle calibration formula adopts a polynomial fitting form, and the temperature measurement deviation is controlled within ±0.2 K.

[0012] Optionally, in one embodiment of the present invention, in step 4, the modified infrared temperature field is used for heat transfer characteristic analysis under different mainstream pressure gradients and turbulence intensities, providing experimental data for aerodynamic heat transfer research and cooling optimization design of two-dimensional braided ceramic matrix composite blades.

[0013] This invention presents a method for calibrating the infrared thermometry angle and correcting the heat transfer coefficient of two-dimensional woven CMC surfaces. By combining surface geometric feature recognition with infrared imaging angle analysis, it achieves quantitative correction of infrared thermometry errors in complex concave-convex morphological regions. This method establishes a mapping relationship between the forward imaging angle of the concave region and the normal imaging angle of the blade, and proposes an infrared calibration model based on texture height and imaging angle, effectively improving the accuracy of infrared thermometry under non-perpendicular viewing conditions. Compared with traditional infrared thermometry methods, this invention significantly improves the reliability and spatial resolution of two-dimensional woven CMC surface temperature and heat transfer measurements, providing accurate and repeatable experimental support for the study of flow heat transfer mechanisms, cooling structure optimization, and thermal protection design of aero-engine turbine blades under complex morphological conditions.

[0014] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0015] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a flowchart of a two-dimensional CMC surface infrared thermometry angle calibration and heat transfer coefficient correction method according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the 2D CMC woven texture infrared shooting angle correction process according to an embodiment of the present invention; Figure 3 This is a schematic diagram of temperature calibration results at different correction angles according to an embodiment of the present invention; Figure 4 This is a comparison cloud map of the Nusselt number before and after infrared angle correction in an embodiment of the present invention. Detailed Implementation

[0016] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0017] Figure 1This is a flowchart illustrating a method for calibrating the angle and correcting the heat transfer coefficient of a two-dimensional CMC surface infrared thermometry according to an embodiment of the present invention.

[0018] like Figure 1 As shown, the method for calibrating the infrared thermography angle and correcting the heat transfer coefficient on the surface of the two-dimensional braided ceramic matrix composite (2D CMC) includes the following steps: Step 1: Use a laser confocal microscope to perform high-precision scanning on the surface of the two-dimensional braided ceramic matrix composite test blade to identify the geometric features of the surface protrusions and depressions, including the texture height difference and local normal angle, for subsequent infrared imaging angle analysis.

[0019] In embodiments of the present invention, the geometric features of the surface protrusions and depressions include the difference in texture height and the local normal angle. The surface texture height ranges from 0.2 mm to 0.6 mm, and the difference in the normal angle between the depression area and the protrusion area is between 0° and 40°.

[0020] Step 2: Based on the angular relationship between the local normal and the overall normal of the blade obtained from geometric features, several typical imaging angles (including the forward imaging angle of the concave region and the imaging angle of the blade's normal) are selected. Multi-angle transient imaging of the surface of the two-dimensional braided ceramic matrix composite test blade is performed using an infrared thermal imager. Simultaneously, the true surface temperature of the two-dimensional braided ceramic matrix composite test blade is measured using an embedded thermocouple. Constant heat flux density and airflow conditions are maintained during the experiment to ensure the comparability of temperature measurement results at different imaging angles.

[0021] In an embodiment of the present invention, the surface of a two-dimensional braided ceramic matrix composite test blade is photographed using an infrared imaging system. The infrared imaging system includes an adjustable-angle infrared thermal imager, a constant-temperature heating device, an airflow control unit, and an infrared window, with a shooting angle range of 30° to 90°.

[0022] Step 3: Based on the difference between the infrared temperature and the actual surface temperature of the thermocouple under different imaging angles, analyze the influence of the imaging angle change on the temperature measurement deviation, and obtain the infrared temperature measurement angle calibration formula by fitting.

[0023] In the embodiments of the present invention, the infrared angle calibration formula adopts a polynomial fitting form, and the calibration results are verified by multiple sets of experiments, with the temperature measurement deviation controlled within ±0.2 K.

[0024] Step 4: The infrared temperature field is pixel-corrected using the infrared angle calibration formula to obtain the true temperature distribution on the surface of the two-dimensional braided ceramic matrix composite test blade. Based on the corrected infrared temperature field, the local convective heat transfer coefficient and Nusselt number distribution are obtained through transient thermal response calculation, thereby achieving reliable characterization of the heat transfer characteristics of complex surfaces.

[0025] In the embodiments of the present invention, the modified temperature field can be used to analyze the heat transfer characteristics under different mainstream pressure gradients and turbulence intensities, providing high-precision experimental data for the aerodynamic heat transfer research and cooling optimization design of two-dimensional braided ceramic matrix composite blades.

[0026] The equivalent geometric model was used to fabricate test pieces via SLA 3D printing. Scanning measurements showed that the geometric accuracy of the characterization model was within ±0.05 mm, effectively reproducing the surface texture features of real CMC. This characterization modeling method can accurately depict the main weave morphology of 2D CMC blade surfaces, providing a unified geometric model basis for aerodynamic heat transfer analysis, cooling design, and thermal protection performance prediction, thereby improving the accuracy and reliability of heat transfer prediction under high-temperature component service conditions.

[0027] The method described in this invention can quantitatively describe the correspondence between the forward imaging angle of the recessed region and the normal imaging angle of the blade, establish an infrared thermometry angle calibration formula under different texture heights, and obtain a more accurate convective heat transfer coefficient and Nusselt number distribution based on the corrected temperature field. This method can effectively improve the accuracy and reliability of infrared thermometry on two-dimensional woven CMC surfaces, providing crucial experimental support for the study of flow heat transfer mechanisms and thermal protection design of blades with complex morphologies.

[0028] The method for calibrating the infrared thermometry angle and correcting the heat transfer coefficient of the surface of two-dimensional braided ceramic matrix composite (2D CMC) proposed in this invention is based on the establishment of the relationship between surface geometry and imaging angle to achieve accurate calibration of the infrared thermometry deviation in the braided texture area, thereby obtaining a more realistic temperature field distribution and heat transfer characteristics.

[0029] like Figure 2 The diagram illustrates the process of correcting the infrared imaging angle of the two-dimensional woven CMC surface according to the present invention. When the infrared camera captures the image at the normal angle, the temperature field distribution in region A can be accurately obtained. However, in the recessed region B, due to the deviation between the surface normal direction and the infrared imaging direction, the temperature measurement results are affected by the viewing angle distortion, resulting in a lower temperature. Therefore, using a typical two-dimensional woven CMC test blade as the research object, angle calibration experiments were conducted in region A at different observation angles (θ = 50°, 60°, 75°). The results were based on the texture height corresponding to different observation angles. H 0 The tilt imaging results of the concave region B are compared and corrected with the normal imaging results of the region A to establish an infrared angle calibration relationship.

[0030] First, a high-precision scan of the test blade surface was performed using a laser confocal microscope to identify and extract the geometric feature parameters of the protrusions and depressions in the texture unit, including texture height. H0 Angle with local normal θ A surface geometry database was constructed to provide a basis for subsequent infrared imaging angle selection and correction.

[0031] Based on this, infrared thermography experiments were conducted using both the forward shooting angle of the concave region and the normal angle of the blade, and embedded thermocouples were placed at the characteristic locations to simultaneously measure the actual temperature. By comparing the infrared temperature measurements at different angles with the actual temperatures measured by the thermocouples, a quantitative relationship between angle changes and temperature measurement deviations was obtained.

[0032] like Figure 3 The figure shows the temperature calibration results of this invention under different correction angles. The figure presents the correction data for region A under multiple imaging angles and temperature conditions, where the horizontal axis represents the number of recordings and the vertical axis represents the measured temperature. After data fitting, the following infrared angle calibration formula is obtained: ; in, T 75 , T 60 , T 0 These represent the infrared temperatures measured in region B at different tilt angles (75°, 60°, and 50°). T 0 This represents the reference temperature obtained under normal imaging conditions. As the formula shows, as the shooting angle deviates from the normal, the infrared thermometry results exhibit systematic errors. This calibration formula can be used to achieve temperature correction at multiple angles.

[0033] like Figure 4 The image shows a comparison of the Nusselt number distribution on the surface of the two-dimensional braided CMC before and after infrared angle correction according to the present invention. Before correction, the temperature in the concave area was underestimated and the local heat transfer coefficient was overestimated due to the deviation in the infrared thermography viewing angle, resulting in increased fluctuations in the Nusselt number distribution and a violation of the weaving periodicity. After angle calibration and temperature field correction, the local Nusselt number distribution is smoother, the periodicity is clearer, and it is highly consistent with the flow heat transfer law under the actual weaving morphology, significantly improving the accuracy and interpretability of the experimental data.

[0034] Experimental results show that the infrared thermometry angle calibration method proposed in this invention can effectively eliminate the imaging deviation caused by surface geometric undulations, accurately reflect the true heat transfer characteristics of the two-dimensional woven CMC blade surface, and significantly improve the reliability of the convective heat transfer coefficient and Nusselt number distribution.

[0035] The present invention provides a method for calibrating the infrared thermometry angle and correcting the heat transfer coefficient of two-dimensional braided ceramic matrix composite surfaces. By combining surface geometric feature identification, imaging angle modeling, and infrared temperature field correction, this method achieves high-precision calibration of temperature measurement errors in complex uneven regions. Compared with traditional uncorrected infrared thermometry methods, this method has significant advantages in temperature measurement accuracy, spatial resolution, and reliability of heat transfer analysis. It can provide a precise and repeatable experimental basis for the study of aerodynamic heat transfer mechanisms, cooling structure optimization, and high-temperature service performance evaluation of two-dimensional braided CMC turbine blades.

[0036] This invention relates to the field of surface heat transfer testing and infrared thermography accuracy correction for high-temperature components in aero-engines. It proposes an infrared thermography calibration and accurate inversion method for heat transfer coefficients applicable to complex surface morphologies of two-dimensional braided ceramic matrix composites (2D CMCs). Addressing the problems of viewing angle distortion, local temperature measurement deviations, and resulting errors in heat transfer coefficient calculation in existing infrared thermal imaging on CMC surfaces with braided textures, this invention establishes a coupled correction model between imaging angle and temperature deviation based on the geometric features of the protrusions and depressions in the surface braided texture. By systematically comparing infrared thermography results from different viewing angles with thermocouple-measured temperatures, an infrared correction formula considering surface height and observation angle is obtained, achieving quantitative temperature correction for non-perpendicular imaging areas. This method effectively eliminates temperature distortion caused by infrared thermography in complex morphology areas (such as fiber bundle protrusions and matrix depressions), significantly improving the temperature measurement accuracy of infrared thermal imaging on complex CMC surfaces. Furthermore, based on the corrected true temperature field, this invention combines a transient thermal response inversion method to obtain a more accurate distribution of local convective heat transfer coefficients. This method has high measurement reliability and spatial resolution in the CMC turbine blade region with significant surface geometric undulations, and can provide accurate experimental support for flow heat transfer analysis of complex woven surfaces, cooling structure design and thermal protection research under high temperature service conditions.

[0037] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0038] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0039] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or N executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

Claims

1. A method for calibrating the angle and correcting the heat transfer coefficient of infrared thermometry on a two-dimensional CMC surface, characterized in that, Includes the following steps: Step 1: Use a laser confocal microscope to scan the surface of the two-dimensional braided ceramic matrix composite test blade to identify the geometric features of the surface protrusions and depressions. Step 2: Based on the angle relationship between the local normal and the overall normal of the blade obtained from the geometric features, select multiple imaging angles and use an infrared thermal imager to perform multi-angle transient imaging of the surface of the two-dimensional braided ceramic matrix composite test blade. At the same time, the true surface temperature of the two-dimensional braided ceramic matrix composite test blade is measured synchronously through an embedded thermocouple. Step 3: Based on the difference between the infrared temperature and the actual surface temperature of the thermocouple under different imaging angles, analyze the influence of the imaging angle change on the temperature measurement deviation, and obtain the infrared temperature measurement angle calibration formula by fitting. Step 4: Use the infrared angle calibration formula to perform pixel correction on the infrared temperature field to obtain the true temperature distribution on the surface of the two-dimensional braided ceramic matrix composite test blade. Based on the corrected infrared temperature field, calculate the local convective heat transfer coefficient and Nusselt number distribution through transient thermal response.

2. The method according to claim 1, characterized in that, In step 1, the geometric features of the surface protrusions and depressions include the difference in texture height and the local normal angle. The surface texture height ranges from 0.2 mm to 0.6 mm, and the difference in the normal angle between the depression area and the protrusion area is between 0° and 40°.

3. The method according to claim 1, characterized in that, In step 2, the shooting angle range of the infrared thermal imager is 30° to 90°.

4. The method according to claim 1, characterized in that, In step 3, the infrared temperature measurement angle calibration formula adopts a polynomial fitting form, and the temperature measurement deviation is controlled within ±0.2 K.

5. The method according to claim 1, characterized in that, In step 4, the corrected infrared temperature field is used to analyze the heat transfer characteristics under different mainstream pressure gradients and turbulence intensities, providing experimental data for the aerodynamic heat transfer research and cooling optimization design of two-dimensional braided ceramic matrix composite blades.

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