Turbine blade surface film thermocouple temperature measurement data deviation analysis method

Abstract

The invention discloses a turbine blade surface thin film thermocouple temperature measurement data deviation analysis method, which takes thin film thermocouple temperature measurement of a turbine blade in an aero-engine as a research object, combines a deviation analysis method with numerical simulation, and changes various thermal physical property parameters through control variables. The radiation-convection-heat conduction coupling heat transfer mechanism of the thin film thermocouple and the turbine blade base layer under the high-temperature and high-pressure working conditions is obtained, then the temperature measurement deviation change rule between the node temperature of the thin film thermocouple and the blade base layer is obtained, and a theoretical basis is provided for deviation correction of temperature measurement of the turbine blade through the thin film thermocouple.

Description

Technical Field

[0001] The invention belongs to the technical field of aviation engines, and in particular relates to a method for analyzing temperature measurement data deviation of thin-film thermocouples on the surface of turbine blades. Background Art

[0002] Modern high-performance aircraft engines pursue increasingly higher thrust-to-weight ratios and thermal efficiency, leading to increasing turbine inlet gas temperatures. To prevent fatigue fracture of turbine blades, cooling technologies, such as film cooling, are widely used. However, film cooling accelerates the drop in gas temperature, reducing aircraft engine performance. Therefore, measuring and acquiring aircraft engine turbine blade temperature is crucial for evaluating cooling effectiveness. Furthermore, accurate turbine blade temperature measurement is crucial for accurately monitoring aircraft engine operating conditions and assessing their health. Due to the harsh operating environment within aircraft engines, conventional thermocouples, such as armored and embedded thermocouples, suffer from slow response times, large temperature measurement errors, and susceptibility to detachment. To address these challenges in aircraft engine turbine blade temperature measurement, the integration of thin film fabrication technologies has led to the development of micro- and nano-scale thin film thermocouples. Due to their small size, low heat capacity, fast response times, no interference with the operating airflow, high mechanical strength, vibration and shock resistance, and the ability to integrate the thin film thermocouple with the measured surface, thin film thermocouples provide highly accurate and reliable turbine blade surface temperature data.

[0003] However, under the high-temperature operating conditions of aircraft engines, the temperature measurement of thin-film thermocouples will still be affected by the radiation heat transfer and convection heat transfer of high-temperature fuel gas, as well as heat conduction between the components being measured. Among them, due to the relatively high temperature of the fuel gas, the deviation caused by thermal radiation is particularly significant, resulting in the temperature measured by the thin-film thermocouple being unable to truly reflect the temperature of the component being measured. In order to improve the temperature measurement accuracy of thin-film thermocouples, it is necessary to calibrate the deviation effects from radiation, heat conduction and convection processes. The calibration of temperature measurement deviation is generally achieved through CFD simulation numerical calculations, but existing simulation studies generally find it difficult to fully analyze the deviation factors from the three heat transfer methods. In the "Research on Thermal Resistance Correction Model of Thin-Film Thermocouple Based on CFD Technology" published in 2021 by Wang Yufang et al. from the Beijing Great Wall Metrology and Testing Technology Research Institute of Aviation Industry, a three-dimensional heat transfer model with CFD numerical simulation for thermal resistance correction was established, which only studied the influence of the thermal conduction term, and lacked research on temperature measurement deviation and calibration caused by thermal radiation. In the 2014 paper “Conjugate heat transfer simulations of athermocouple sensor in a lowtemperature nitrogen gas ambient”, Sarantis P et al. established a three-dimensional model that studied the conjugate effects of heat conduction and convection, while ignoring the deviation caused by thermal radiation. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the present invention provides a method for analyzing the deviation of thin-film thermocouple temperature measurement data on the surface of turbine blades. The thin-film thermocouple temperature measurement of turbine blades in aircraft engines is taken as the research object, and the deviation analysis method is combined with numerical simulation. By controlling variables to change various thermal physical parameters, the radiation-convection-conduction coupled heat transfer mechanism of the thin-film thermocouple and the turbine blade substrate under high temperature and high pressure conditions is obtained, and then the temperature measurement deviation change law between the thin-film thermocouple node temperature and the blade substrate is obtained, providing a theoretical basis for deviation correction of turbine blade temperature measurement using thin-film thermocouples.

[0005] The technical solutions adopted by the present invention to solve the technical problems are as follows:

[0006] Step 1: Create a three-dimensional model of an aircraft engine turbine blade with a thin film thermocouple installed;

[0007] Step 2: Mesh each part of the turbine blade 3D model, perform mesh independence tests, and simulate multiple operating conditions. Under the radiation-convection-conduction coupled setting, change the characteristic parameters of the operating condition to obtain multiple sets of numerical results.

[0008] Step 3: Combined with the calculation formula of temperature measurement deviation, calculate the absolute temperature measurement deviation and relative temperature measurement deviation between the thermocouple hot node temperature and the turbine blade surface temperature under various working conditions;

[0009] Step 4: Analyze the temperature distribution obtained by numerical calculation and the variation law of temperature measurement deviation;

[0010] Step 5: Compare the absolute temperature measurement deviation and relative temperature measurement deviation values ​​obtained in step 3 with the temperature measurement values ​​of the turbine blade surface under test conditions provided by the research institute to verify the reliability and accuracy of the results.

[0011] Furthermore, the three-dimensional model of the turbine blade in step 1 includes a gas inlet, a cooling gas inlet, a turbine blade, a thin film thermocouple, a gas outlet and a cooling gas outlet.

[0012] Furthermore, a hexahedral structure grid is drawn for the thin film thermocouple part in step 2, a tetrahedral grid is drawn for the gas domain and the turbine blade part, and encryption processing is performed on the interface between the thin film thermocouple and the turbine blade to meet the requirements of temperature measurement accuracy of the turbine blade under complex working conditions inside the aircraft engine.

[0013] Furthermore, the grid independence test is to detect the change of the average temperature of the turbine blade and the thin film thermocouple temperature measurement area as the number of grids increases.

[0014] Furthermore, when setting up the simulation calculation, it must be ensured that the radiation-convection-heat conduction coupling setting is completed, including setting up the solution of the energy equation, the gas multi-component transport equation, the turbulence equation and the radiation transfer equation.

[0015] Furthermore, the characteristic parameters of step 2 are parameters related to heat transfer in the operating conditions of the aircraft engine, including inlet gas temperature, gas composition, and gas velocity.

[0016] Furthermore, the absolute temperature measurement deviation in step 3 is calculated using the following formula:

[0017] ΔT ab =|T tc -T dut |

[0018] The relative temperature measurement deviation uses the following formula:

[0019]

[0020] Where, ΔT ab is the absolute temperature measurement deviation value, is the relative temperature measurement deviation value, T tc is the temperature of the thin film thermocouple hot node, T dut is the temperature of the device under test.

[0021] The beneficial effects of the present invention are as follows:

[0022] This paper provides a method for analyzing temperature measurement data deviations from thin-film thermocouples on turbine blade surfaces, specifically focusing on the often-overlooked temperature measurement deviations caused by radiation heat transfer. Compared to calculations that ignore radiation terms, the resulting numerical results are closer to experimental values, demonstrating improved simulation accuracy and reliability. The following general conclusions, more consistent with practical applications, are also provided:

[0023] (1) The temperature of the component measured in the radiation-convection-conduction coupled heat transfer case is higher than the temperature in the non-radiation heat transfer process calculation example, indicating that both the measured component and the thermocouple absorb the radiation of the high-temperature gas, which is consistent with the correct radiation heat transfer direction under actual working conditions; when the inlet gas temperature is low, the heat conduction and convection heat transfer processes occupy the main position in the coupled heat transfer, but as the inlet gas temperature increases, the share of radiation heat transfer in the coupled heat transfer becomes higher and higher, which is also in line with the trend of the fourth power law.

[0024] (2) In the coupled heat transfer process of the turbine blade temperature measurement model, the temperature measurement deviation of the thin film thermocouple is reduced compared with the calculation example of the non-radiative heat transfer process. This conclusion can be drawn by studying the calculation results of the proportion of gas components, that is, Figure 7 As shown in (a) and (b), this shows that coupled heat transfer will make the turbine blades and thin film thermocouples closer to thermal equilibrium in actual working conditions.

[0025] The radiation-convection-conduction coupled heat exchange setting in the present invention can more comprehensively analyze the temperature measurement data deviation factors of turbine blades equipped with thin-film thermocouples inside aircraft engines, effectively improve the temperature measurement accuracy of thin-film thermocouples, and provide a theoretical basis for the calibration of temperature measurement deviation of thin-film thermocouples of turbine blades. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the process of the embodiment of the present invention;

[0027] Figure 2 Schematic diagram of the physical model for temperature measurement of turbine blades according to the present invention, (a) is an overall view of the three-dimensional model, (b) is a forward transparent view of the three-dimensional model, (c) is a schematic diagram of the relative positions of the thin-film thermocouples, and (d) is an enlarged view of the thin-film thermocouple film layer;

[0028] Figure 3 Schematic diagram of the equivalent multi-layer semi-transparent flat plate radiation transfer model of the present invention;

[0029] Figure 4 Schematic diagram of a simplified multi-layer plate model involved in radiation transmission according to the present invention;

[0030] Figure 5 This is a schematic diagram showing the temperature results of the present invention;

[0031] Figure 6 Schematic diagram of the change of relative temperature measurement deviation values ​​corresponding to various thermophysical variables in an embodiment of the present invention, (a) is the change law of relative temperature measurement deviation with the surface emissivity of the platinum-iridium layer, (b) is the change law of relative temperature measurement deviation with the surface diffuse fraction of the platinum-iridium layer, (c) is the change law of relative temperature measurement deviation with the inlet gas temperature, and (d) is the change law of relative temperature measurement deviation with the proportion of H2O and CO2 components.

[0032] Figure 7 Schematic diagram comparing relative temperature measurement deviations for coupled radiation heat exchange (a) and non-radiation heat exchange (b) when the gas component ratio is used as a variable in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to the accompanying drawings and examples.

[0034] A method for analyzing deviations in temperature measurement data of thin-film thermocouples on the surface of a turbine blade comprises the following steps:

[0035] Step 1: Create a three-dimensional model of an aircraft engine turbine blade with a thin film thermocouple installed;

[0036] Step 2: Conduct grid independence tests and simulation calculations for multiple typical operating conditions. Under the radiation-convection-conduction coupled setting, change the typical characteristic parameters of the operating conditions to obtain multiple sets of numerical results.

[0037] Step 3: Combined with the calculation formula of temperature measurement deviation, calculate the absolute temperature measurement deviation and relative temperature measurement deviation between the thermocouple hot node temperature and the turbine blade surface temperature under various working conditions.

[0038] Step 4: Analyze the temperature distribution and temperature measurement deviation change patterns obtained through numerical calculations, and draw final conclusions.

[0039] Step 5: Compare the simulation results with the data provided by the research institute to verify the reliability and accuracy of the results.

[0040] The turbine blade fluid domain in step 1 consists of six parts: gas inlet, cooling gas inlet, turbine blade, thin film thermocouple, gas outlet, and cooling gas outlet.

[0041] In step 2, a hexahedral structure grid is drawn for the thin film thermocouple part, and a tetrahedral grid is drawn for the gas domain and the turbine blade part. The interface between the thin film thermocouple and the turbine blade is encrypted to meet the requirements for temperature measurement accuracy of the turbine blade under complex working conditions inside the aircraft engine.

[0042] In step 2, to prevent the mesh number from significantly affecting the simulation results, a mesh independence test is performed. This test examines the average temperature changes of the turbine blades and the thin-film thermocouple temperature measurement area as the mesh number increases. If no errors are made, the average temperatures of both areas gradually stabilize as the mesh number increases. Furthermore, by balancing calculation accuracy and computing power, the optimal mesh set for subsequent calculations can be determined.

[0043] When setting up simulation calculations, it is necessary to ensure that the radiation-convection-heat conduction coupling settings are completed, such as setting the solution of the energy equation, gas multi-component transport equation, turbulence equation and radiation transfer equation, etc. The specific settings should refer to the actual situation of the CFD simulation software used.

[0044] The typical parameters selected for simulation calculations in step 2 should be core parameters related to heat transfer in aircraft engine operating conditions, such as inlet gas temperature, gas composition, gas velocity, etc.; then, multiple typical values ​​of the parameters are selected to carry out multiple sets of case calculations of control variables; in particular, if there are drastic changes in the temperature measurement values ​​within a smaller parameter range, interpolation should be performed in this interval, and additional cases should be added to obtain a more accurate change pattern.

[0045] To obtain the absolute temperature measurement deviation value in step 3, you need to use the following calculation formula:

[0046] ΔT ab =|T tc -T dut |

[0047] To obtain the relative temperature measurement deviation value, the following formula should be used:

[0048]

[0049] Where ΔT ab is the absolute temperature measurement deviation value, is the relative temperature measurement deviation value, T tc is the temperature of the thin film thermocouple hot node, T dut is the temperature of the measured part (turbine blade).

[0050] Specifically, the numerical results obtained in step 4 can be expressed in the form of temperature cloud maps, contour maps, etc., which makes the calculation results more intuitive.

[0051] In step 4, the obtained temperature measurement deviation value can be expressed in a corresponding form such as a table or a line graph, so that the variation pattern of the thin film thermocouple temperature measurement deviation can be clearly seen.

[0052] Example:

[0053] This embodiment is a study on the temperature measurement deviation analysis of platinum-iridium thin film thermocouples taking into account radiation correction. Figure 1 The implementation scheme flow chart shown is as follows.

[0054] Step 1: Create a three-dimensional model of an aircraft engine turbine blade with a thin film thermocouple installed.

[0055] Based on the internal structure of the aircraft engine turbine, a physical model for temperature measurement of the turbine blade including the flow field is established. Figure 2 (a) Figure 2 As shown in (b), it includes turbine blades, thin-film thermocouples, inlet gas flow field and cooling air flow field. The turbine blades are equipped with an air film cooling structure to simulate the actual working conditions of the aircraft engine to the greatest extent possible.

[0056] Figure 2 (c) Figure 2 (d) is an enlarged cross-sectional view of a turbine blade equipped with a platinum-iridium thin-film thermocouple. In this model, the thin-film thermocouple is applied to the suction surface of the blade. To prevent the thickness of the thin-film thermocouple from interfering with the flow field and causing excessive velocity errors during the simulation, the thermocouple junction is modeled as embedded. This modeling treatment has a negligible impact on the simulation results. The platinum-iridium thin-film thermocouple studied in this example has a multilayer structure: from bottom to top, it consists of a NiCrAlY transition layer, a YSZ / Al2O3 composite insulation layer, a platinum-iridium alloy dipole sensitive layer, and an Al2O3 protective layer.

[0057] Since the size of the platinum-iridium thin film thermocouple is micron-level, it can be regarded as a semi-transparent film for calculation from the perspective of optical properties. Therefore, the internal radiation transfer process is relatively complicated, such as Figure 3 As shown. Therefore, the following simplification is made: the interaction between radiation and semi-transparent medium is equivalent to the interaction between radiation and the two surfaces of the medium, that is, the semi-transparent medium is equivalent to two semi-transparent surfaces with absorption, reflection, transmission or refraction capabilities, and equivalent radiation characteristic parameters are given to them. The simplified equivalent physical model is as follows Figure 4 .

[0058] Step 2: Carry out grid independence tests and simulation calculations of multiple typical working conditions. Under the radiation-convection-heat conduction coupling setting, change the typical characteristic parameters of the working conditions to obtain multiple sets of numerical results.

[0059] The model was meshed. Meshing independence was verified by performing coupled radiation-convection-conduction heat transfer calculations at an inlet gas temperature of 1600K. The temperatures of the blade suction surface and the upper surface of the platinum-iridium thin-film thermocouple's temperature-measuring layer were compared for different mesh sizes to determine when the difference stabilized. Ultimately, balancing accuracy and efficiency, a relatively optimal mesh size of 21,427,079 and a node count of 4,271,011 were selected for subsequent simulations.

[0060] In this embodiment, the typical radiation characteristic parameters of the platinum-iridium temperature measurement layer of the thin-film thermocouple are selected: surface emissivity (0.3, 0.5, 0.6, 0.7, 0.9), surface diffuse fraction (0.2, 0.4, 0.5, 0.6, 0.8), and thermal boundary conditions: inlet gas temperature (1200K, 1400K, 1600K, 1800K, 2000K), the proportion of gas components H2O, CO2, N2, and air (mainly studying the ratio of H2O to CO2, such as 1:2, 1:1, 2:1) as variables for example setting, and analyzing the influence of each of these variables on the temperature measurement deviation. The surface temperature of the turbine blade and the temperature of the thin-film thermocouple hot node under each example are obtained by calculation. The schematic diagram of the details of the calculated temperature in the physical model is shown as follows. Figure 5 shown.

[0061] Step 3: Combined with the calculation formula of temperature measurement deviation, calculate the absolute temperature measurement deviation and relative temperature measurement deviation between the thermocouple hot node temperature and the turbine blade surface temperature under various working conditions.

[0062] At this time, the temperature measurement deviation calculation formula is applied:

[0063] ΔT ab =|T tc -T dut |

[0064]

[0065] Based on the obtained data, the absolute temperature measurement deviation and the relative temperature measurement deviation can be obtained.

[0066] Step 4: Analyze the temperature distribution and temperature measurement deviation change patterns obtained through numerical calculations, and draw final conclusions.

[0067] The results and conclusions of this embodiment are analyzed as follows:

[0068] (1) For the surface emissivity of the platinum-iridium layer, when the surface emissivity of the platinum-iridium layer gradually increases and the temperature of the platinum-iridium layer gradually increases, the corresponding temperature measurement deviation value also has a trend of first decreasing and then increasing, such as Figure 6As shown in (a); for the surface diffusion fraction of the platinum-iridium layer, when the surface diffusion fraction of the platinum-iridium layer increases from small to large, the temperature of the platinum-iridium layer gradually decreases, and the corresponding temperature measurement deviation value first decreases and then increases, as shown in Figure 6 (b) shown.

[0069] (2) As the inlet gas temperature increases, the temperature measurement deviation of the thin film thermocouple will become larger and larger, such as Figure 6 As shown in (c), in this case, the temperature of the platinum-iridium temperature measuring layer is always higher than the suction surface of the blade.

[0070] (3) When the total proportion of H2O and CO2 increases, the heat conduction and radiation heat transfer of the gas to the solid domain becomes more obvious, and the temperature measurement deviation of the thin film thermocouple also increases. Figure 6 As shown in (d), compared with CO2, the increase in the proportion of H2O has a more significant effect on enhancing the thermal conductivity and radiation heat transfer of the gas.

[0071] Step 5: Compare the simulation results with the data provided by the research institute to verify the reliability and accuracy of the results.

[0072] The comparison and verification show that the numerical calculation results obtained in this embodiment are highly consistent with the experimental values, and have good accuracy and reliability. Due to the particularity of the experimental data, we will not elaborate on it in detail here.

Claims

1. A method for analyzing temperature measurement data deviation of thin film thermocouples on the surface of turbine blades, characterized in that: The steps include: Step 1: Create a three-dimensional model of an aircraft engine turbine blade with a thin film thermocouple installed; Step 2: Mesh each part of the turbine blade 3D model, perform mesh independence tests, and simulate multiple operating conditions. Under the radiation-convection-conduction coupled setting, change the characteristic parameters of the operating condition to obtain multiple sets of numerical results. Step 3: Combined with the calculation formula of temperature measurement deviation, calculate the absolute temperature measurement deviation and relative temperature measurement deviation between the thermocouple hot node temperature and the turbine blade surface temperature under various working conditions; Step 4: Analyze the temperature distribution obtained by numerical calculation and the variation law of temperature measurement deviation; Step 5: Compare the absolute temperature measurement deviation and relative temperature measurement deviation values ​​obtained in step 3 with the temperature measurement values ​​of the turbine blade surface under test conditions provided by the research institute to verify the reliability and accuracy of the results.

2. The method for analyzing temperature measurement data deviation of thin film thermocouples on the surface of turbine blades according to claim 1, characterized in that: The three-dimensional model of the turbine blade in step 1 includes a gas inlet, a cooling gas inlet, a turbine blade, a thin film thermocouple, a gas outlet, and a cooling gas outlet.

3. The method for analyzing temperature measurement data deviation of thin film thermocouples on the surface of turbine blades according to claim 2, characterized in that: In the step 2, a hexahedral structure grid is drawn for the thin film thermocouple part, a tetrahedral grid is drawn for the gas domain and the turbine blade part, and encryption processing is performed on the interface between the thin film thermocouple and the turbine blade to meet the requirements of temperature measurement accuracy of the turbine blade under complex working conditions inside the aircraft engine.

4. The method for analyzing temperature measurement data deviation of thin film thermocouples on the surface of turbine blades according to claim 3, characterized in that: The grid independence test is to detect the change of the average temperature of the turbine blade and the thin film thermocouple temperature measurement area as the number of grids increases.

5. The method for analyzing temperature measurement data deviation of thin film thermocouples on the surface of turbine blades according to claim 4, characterized in that: When setting up the simulation calculation, it is necessary to ensure that the radiation-convection-heat conduction coupling setting is completed, including setting the solution of the energy equation, the gas multi-component transport equation, the turbulence equation and the radiation transfer equation.

6. The method for analyzing temperature measurement data deviation of thin film thermocouples on the surface of turbine blades according to claim 5, characterized in that: The characteristic parameters of step 2 are parameters related to heat transfer in the operating conditions of the aircraft engine, including inlet gas temperature, gas composition, and gas velocity.

7. The method for analyzing temperature measurement data deviation of thin film thermocouples on the surface of turbine blades according to claim 6, characterized in that: The absolute temperature measurement deviation in step 3 is calculated using the following formula: ΔT ab =|T tc -T dut | The relative temperature measurement deviation uses the following formula: Where, ΔT ab is the absolute temperature measurement deviation value, is the relative temperature measurement deviation value, T tc is the temperature of the thin film thermocouple hot node, T dut is the temperature of the device under test.

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