Temperature Measurement Error Research Articles

Analysis of cooling effects and measurement errors in water-cooled thermocouples for total temperature measurement in aviation engine combustion chambers

Accurate measurement of the total temperature in the main combustion chamber of an aviation engine is crucial for assessing engine performance. However, a significant challenge exists in balancing the heat transfer errors caused by the necessary cooling of the measuring device with measurement precision. The research employs a combination of numerical simulations and experimental methods to investigate this issue. The numerical simulations utilized the Reynolds-averaged Navier Stokes (RANS) coupled with a conjugate heat transfer approach to study the primary flow characteristics and heat transfer properties within the combustion chamber and the probe body. The experiments were conducted in a heat-calibration wind tunnel, validating the results of the numerical simulations. The results show that by implementing water cooling, the probe's body temperature can be reduced from 1200 °C in high-temperature conditions to 400 °C, with localized temperature imbalances still present in the edge areas of the probe. Tracing the cooling water path reveals that the vertical bends in the internal channels lead to an increase in localized pressure loss of the cooling water. The study quantitatively analyzes measurement errors caused by three heat transfer modes: radiation, convection, and conduction. In low-load conditions of the combustion chamber, heat conduction plays a dominant role, with measurement errors due to conduction reaching up to 70 % of the total measurement error. Radiation further increases the temperature measurement errors of the thermocouple's junctions near the chamber wall. As the combustion chamber temperature increases, entering high-load conditions, the cooling effect of water becomes limited, reducing conduction errors and increasing radiation errors. In these conditions, radiation errors constitute 60–70 % of the total measurement error. It suggests the importance of considering temperature corrections when using water-cooled temperature measurement devices. The research reveals several crucial insights regarding the performance and limitations of water-cooled thermocouples.

Half-wave voltage controllable optical voltage sensor with arbitrary electric field direction modulation*

Abstract An optical voltage sensor with an arbitrary electric field direction modulation (AEFDM) mode is proposed to increase the half-wave voltage. The mode is realized by heterogeneous electrodes arranged in a center-symmetric way, and generates an electric field with a direction at an arbitrary angle to the light propagation direction. The finite element method and coupling wave theory are used to design and optimize the electrodes and field distribution. The experimental results show that heterogeneous electrodes and AEFDM mode are able to regulate the sensor’s half-wave voltage in a range from 1 to 30 times (47–1409 kV), with 0.5 class accuracy and 99.99% linearity. This novel AEFDM method proposes a new electrode shape and position, reducing temperature drift to 50% compared to solid-state voltage divider method.

Thermal analysis of V-pad thermocouple used on once-through steam generator tubes

Once-Through Steam Generators (OTSGs) are used in the oil sands industry to produce steam, which is injected into oil sands reservoirs to produce bitumen. OTSGs consist of a combustion zone where natural gas is combusted to generate thermal energy, which boils water within tubes that pass through the OTSG. In a typical OTSG, the temperature at the external wall of the tubes can reach as high as 500 °C, or even higher. Temperature measurement of the tube wall is critical for safe operation and this can be determined by using thermocouples. However, the placement of the thermocouple and its shield to protect it on the tube outer wall interferes with heat transfer and, thus, the measured temperature from the thermocouple may not be equal to the bare tube (no thermocouple) temperature. Here, we examine how the placement of a thermocouple on a tube wall in an OTSG affects the tube wall temperature by using finite-element-based heat transfer modelling. Depending on the foulant thickness, and the placement of the thermocouple, the local tube wall temperature increases by 45 to 55 °C. The results show that using thermocouples with shields can yield a temperature measurement error of order of 15–30 °C above the actual bare tube temperature. The results provide a basis for correcting the thermocouple/shield derived value to the actual temperature of the tube wall.

Precision Temperature Measurement and Error Analysis for Three-Wire PT100 Resistance Temperature Detector (RTD) using LTSpice

This work focuses on temperature measurement and error extraction for Resistance Temperature Dependence (RTD). RTD is notable for its high accuracy, linearity, and stability. However, obtaining a system error of less than unity in RTD is critical. A platinum RTD is an ideal option if the system requires an accuracy level over a wide temperature range (-200°C to +800°C). Therefore, this work investigated the temperature measurement and extraction of error in RTD by simulating a three-wired PT100 RTD using LTSpice. The analytical calculations were also developed to demonstrate the RTD’s error and were compared with the simulation results for verification purposes. It was discovered that the optimized temperature measurement and percentage errors are 0.01°C and 0.004% respectively. The values of Vc, Sense Resistor (RSENSE), and Reference Resistor (RREF) for the excitation current were found to be significant to maximize the output voltage and mean absolute error (MAE) on the test set, offering insights into the model's overall fit, average deviation, and sensitivity to outliers. Results reveal strong correlations between PV module temperature, irradiance, and AC power generated.

Multi-physical field coupling modeling of microwave heating and reduction behavior of zinc oxide

Microwave heating provides a cleaner pyrometallurgical method for separating zinc from electric arc furnace dust (EAFD, a solid waste generated during steel production with excellent dielectric properties). Despite its undisputed heating efficiency, the impact of microwave heating characteristics on the zinc removal process from EAFD remains unclear. This paper focuses on ZnO, one of the primary components of EAFD, and develops an electromagnetic-thermal-chemical reaction model to analyze the effects of microwave power and graphite addition on heating behavior, reduction reactions, field distributions, and reaction kinetics. The results indicate that the heat generated from the interaction between microwaves and materials exhibits inherent non-uniformity, leading to the localized thermal effect and making the error of general temperature measurement methods. Increasing microwave power and adding graphite enhance heating efficiency and promote the reduction reaction but also result in significant internal-external temperature disparity and worse temperature distribution. At 1000 W, with 1.2 times the stoichiometric amount of graphite addition, the temperature measurement error reaches approximately 200 °C, potentially affecting the kinetic results to a certain degree. The non-isothermal kinetics results from simulations indicate that the localized thermal region exhibits a lower average activation energy of 47.5 kJ/mol compared to experimental results, suggesting that the lower activation energy of the ZnO reduction reaction during microwave heating is primarily caused by the localized thermal effect rather than the non-thermal effect. Additionally, in the energy distribution, the higher proportion of return loss during heating underscores the importance of a well-designed microwave heating system.

Automatic adjustment of the parameters of the temperature measurement algorithm in a wide range

Existing methods and devices for measuring temperature are described, and it is noted that resistance thermometers are most widely used as temperature sensors in systems for collecting and monitoring environmental parameters. It is shown that the main source of temperature measurement errors when connecting sensors remotely is the resistance of the connecting lines, determined by their length. The main methods for reducing the measurement error caused by the influence of the resistance of the vehicle connection line on the temperature measurement results are considered. The advantages of two-wire circuits in comparison with three- and four-wire circuits are formulated. As an analogue, a two-wire method of measuring temperature with an integrating converter is considered in detail, implemented on the basis of a device with a built-in microcontroller, and allowing to obtain such advantages as reducing measurement time, detuning from interference and quantization noise and, as a result, reducing the temperature measurement error in comparison with similar two-wire measurement methods. An alternative two-wire method for measuring temperature with automatic adjustment of the parameters of the measurement algorithm is proposed, aimed at increasing the measurement accuracy by weakening the influence of the time constant. The search for the optimal time of the first integration step was carried out. Experimental studies and evaluation calculations were carried out to confirm the effectiveness of the proposed solution. The coefficient of variation when the resistance of the vehicle changes in the range of 1–4 kOhm lies in the range, and the range of change in the relative error of resistance measurement when using auto-tuning within the specified range has decreased by more than 4 times. The results of the experiment allow us to count on the possibility of using the method in control and regulation systems with remote connection of temperature sensors.

High-performance Smart Home System based on Optimization Algorithm

Background: With the recent COVID-19 pandemic, people have become increasingly concerned about their physical health. Therefore, the ability to monitor changes in the surrounding environment in real-time and automatically improve the environment has become a current hot topic to improve the overall health level. Objective: This article describes the design of a high-performance intelligent home system that can simultaneously perform monitoring and automatic adjustment functions. Methods: The ESP8266 was used as the core controller, and the DHT11 and G12-04 sensors were used to collect data, such as temperature, humidity, and ambient light intensity. The sampling frequency was increased and the sampled data were processed to improve data accuracy. The sampled data were wirelessly transmitted to a PC or mobile terminal for real-time display. When the sampled data underwent sudden changes, an alert message was sent via the mobile terminal. Based on the real-time changes in ambient light, an improved lighting brightness adjustment algorithm combining bang-bang and single neuron adaptive PID control was used to adjust the lighting brightness. Results: After testing the system designed in this paper and analyzing the errors compared to standard values, the temperature measurement error ranged from 0% to 0.01107%, and the humidity measurement error ranged from 0% to 0.03797%. The improved algorithm was simulated and tested using MATLAB software and compared with traditional PID algorithms and single-neuron adaptive PID algorithms. The improved algorithm did not overshoot during adjustment, and the system reached a steady state much faster than traditional algorithms. Conclusion: The system showed good performance in real-time, stability, and accuracy, fully demonstrating the effectiveness of the devices and algorithms used in the system. This provides ideas for the design and improvement of future smart homes.

Heat transfer error analysis of high-temperature wall temperature measurement using thermocouple

Thermocouples are widely employed as the temperature measuring element for an aero-engine. However, due to the unique characteristics of the aero-engine test environment, there exist significant temperature measurement errors of the thermocouple. The steady-state heat transfer error of the thermocouple can be attributed to convection heat transfer error, wire heat transfer error, and radiation heat transfer error. The flow and heat transfer process of wall temperature measurements using armored K-type thermocouples were simulated numerically by Fluent software at the Mach number of 0.1–0.5 and the temperature of 700∼1200 K. The results indicate that convective error accounts for more than 55 % of the total transfer error. To reduce excessive temperature measurement errors, a novel airflow stagnation cover structure around the thermocouple was presented. When the diameter of the stagnation cover is 2 mm, the error of the thermocouple is reduced to less than 1 %.

Theoretical and numerical investigation of introduced errors in surface temperature measurements of pistons applied in internal combustion engine

DMP (Differences in Material Properties) often exists between temperature sensors and combustion chamber components of ICE (Internal Combustion Engine), resulting in IEs (Introduced Errors) in the temperature measuring process. In this paper, we present a comprehensive theoretical analysis of the correlation between introduced errors on chamber components and the DMP. The analysis process considers the characteristics of the chamber's heat transfer BC (Boundary Condition). Then, simulations are used to investigate the introduced error of hardness plug and thermocouple sensors on the top surface of an ICE aluminum alloy piston. The theoretical analysis results indicate that heat transfer BC can be segmented into the time-averaged and fluctuation parts, and IEs are linearly superimposed under these two parts of BCs. The heat conductivity impacts the time-averaged error and the product of heat conductivity, density, and heat capacity impacts the fluctuation error. The experimental and simulation results indicate that the max time-average error of the hardness plug on piston is 2.4 °C, with a fluctuation introduced error of 3.6 °C and a total introduced error of 6 °C; and the time-average introduced error of thermocouple sensor is 9.4 °C, with a fluctuation error of 5.8 °C and a total introduced error of 15.2 °C. Finally, a fluctuation error correction method is proposed to reduce error. After correction, the error is reduced by 71 % and 66 % for hardness plug and thermocouple, respectively.

Real-Time Temperature Monitoring of Lithium Batteries Based on Ultrasonic Technology.

Electrochemical energy storage stations serve as an important means of load regulation, and their proportion has been increasing year by year. The temperature monitoring of lithium batteries necessitates heightened criteria. Ultrasonic thermometry, based on its noncontact measurement characteristics, is an ideal method for monitoring the internal temperature of lithium batteries. In this study, temperature and ultrasonic time delay measurement experiments were conducted on 18650 lithium batteries and laminated and wound lithium batteries to obtain the corresponding relationship between temperature and time delay and validate the temperature measurement for the same type of battery. The experimental results show that (1) the ultrasonic temperature measurement technique exhibits a relatively large error when used for 18650 Li-ion batteries under experimental conditions; (2) in the experiments on laminated and wound soft-pack lithium batteries, the relationship between temperature and time delay exhibits a nonlinear characteristic; and (3) under the experimental conditions, the ultrasonic temperature measurement errors were ±1.1 °C for stacked Li-ion batteries and ±1.4 °C for wound Li-ion batteries.

ВПЛИВ УМОВ РОБОТИ НА ТЕМПЕРАТУРНИЙ РЕЖИМ ПІДШИПНИКІВ З МЕТАЛЕВИМИ ТА КЕРАМІЧНИМИ КУЛЬКАМИ

The results of an experimental study of the temperature mode of operation of rolling bearings under different lubrication conditions are presented. Comparative tests of all-metal bearings and similar bearings with rolling elements made of silicon nitride (hybrid bearings) when lubricated with an oil jet and an oil-air mixture in the range of rotor rotation frequencies from 0 to 35000 rpm were carried out. For the experiments, a specially created set was used, which allows you to study the temperature of the bearings and the temperature of the lubricant at the entrance and exit from the bearings. The axial load on the bearings was created with the help of a compression spring, which rested on the outer rings of the bearings. This made it possible to close the load inside the system. During the tests, the load was 0 N, 1000 N, and 2000 N. Tests were carried out for two modes of bearing lubrication: oil jet and oil-air mixture. The method of measuring the temperature of the outer ring of bearings is described. The temperature measurement error was considered as a complex of instrumental error and method error. It was assumed that the temperature error is subject to a normal distribution. The conducted analysis showed that the error of measuring the temperature of the bearing ring was ± 2.8 °C with a confidence probability of 95 %. It has been established that bearings with ceramic balls in the entire studied range behave qualitatively and quantitatively in approximately the same way as with steel ones. The temperature level of hybrid bearings is slightly higher when lubricated with both an oil jet and an oil-air mixture. There is a clear connection between the values of the bearing temperature and the moment of resistance in the bearing: the increase in temperature is observed under the same conditions under which the moment of resistance increases.

A WGM-FP hybrid microcavity for simultaneous measurement of NaCl concentration and temperature

Whispering gallery mode (WGM) resonator is sensitive to the external medium change due to its strong light-matter interaction. However, the temperature sensitivity of silica-based WGM resonators would cause crosstalk, which is a fatal shortcoming for those high-quality (Q) resonators. In this paper, a hybrid microcavity including WGM resonance and Fabry–Pérot (FP) interference is proposed for simultaneous measurement of NaCl concentration and temperature, using the same microcavity in the same system to obtain two types of optical signals. The experimental results indicate that the maximum measurement error of NaCl concentration and temperature without compensation is about ± 0.026 % and ± 1.1 °C, while they would be ± 0.012 % and ± 0.3 °C after compensation. Sharing one microcavity enables temperature compensation to achieve temperature synchronization, and sharing of one system ensures the simplicity and stability of the sensing platform.

Design and implementation of a Li River water quality monitoring and analysis system based on outlier data analysis.

The detection of water quality indicators such as Temperature, pH, Turbidity, Conductivity, and TDS involves five national standard methods. Chemically based measurement techniques may generate liquid residue, causing secondary pollution. The water quality monitoring and data analysis system can effectively address the issues that conventional methods require multiple pieces of equipment and repeated measurements. This paper analyzes the distribution characteristics of the historical data from five sensors at a specific time, displays them graphically in real time, and provides an early warning of exceeding the standard; It selects four water samples from different sections of the Li River, based on the national standard method, the average measurement errors of Temperature, PH, TDS, Conductivity and Turbidity are 0.98%, 2.23%, 2.92%, 3.05% and 3.98%.;It further uses the quartile method to analyze the outlier data over 100,000 records and five historical periods are selected. Experiment results show the system is relatively stable in measuring Temperature, PH and TDS, and the proportion of outlier is 0.42%, 0.84% and 1.24%. When Turbidity and Conductivity are measured, the proportion is 3.11% and 2.92%. In the experiment of using 7 methods to fill outlier, K nearest neighbor algorithm is better than others. The analysis of data trends, outliers, means, and extreme values assists in making decisions, such as updating and maintaining equipment, addressing extreme water quality situations, and enhancing regional water quality oversight.

A correction method for radial distortion and nonlinear response of infrared cameras.

The key feature of non-contact temperature measurement provided by infrared (IR) cameras underpins their versatility. However, the accuracy of temperature measurements with IR cameras depends on imaging quality due to their non-contact nature, such as the lens, body temperature, and measurement environment. This paper addresses the correction of radial distortion and nonlinear response issues in IR cameras. To address radial distortion, we have designed a passive checkerboard calibration board specifically for infrared cameras. This board is used to calibrate the IR camera and derive the necessary camera parameters. Subsequently, these parameters are applied during the actual measurement process to rectify radial distortion effectively. Building on the radial distortion correction method mentioned above, we propose a multi-point segmented calibration approach that considers different temperature ranges and imaging regions. This method alleviates the issue of reduced temperature measurement accuracy due to variations in camera responses by computing gain and offset coefficient matrices for each temperature range. Experimental results demonstrate the effectiveness of the calibration board in correcting radial distortion in IR cameras, with a mean reprojection error of less than 0.16 pixels. Regarding the nonlinear response problem, the introduced method significantly reduces the relative error in temperature measurement. In the verification phase, spanning from 100 to 500 °C, the average relative error in temperature measurement decreases by 0.49% from 1.61% before and after correction, which highlights a substantial improvement in temperature measurement accuracy. This work gives a useful reference to improve the imaging quality and temperature measurement accuracy using infrared cameras.

Intelligent decision-making in healthcare telemonitoring via forward-backward chaining and IoT

Healthcare telemonitoring has emerged as a promising approach to remotely monitor patients remotely, enabling timely intervention and personalized care. Internet of things (IoT) device-generated patient data necessitates innovative solutions for intelligent healthcare decision-making, as current methods struggle to provide timely, context-aware, and data-driven recommendations, resulting in suboptimal patient care. This study aims to develop an intelligent decision-making framework for healthcare telemonitoring by leveraging forward-backward chaining and IoT technology. The research focuses on a system using forward-backward chaining algorithms to analyze real-time patient data from IoT devices. It utilizes machine learning models to adapt to changing conditions and refine decision-making, demonstrating its ability to provide real-time context-aware recommendations. Temperature, blood pressure, oxygen level, and heart rate measurement errors are 2.01%, 1.74 to 2.13%, 0.61%, and 1.45%, respectively. The success rate of early disease diagnosis using an expert system is 81%, with an average application interface responsiveness time of 4.978 s. The integration of IoT data with intelligent decision-making algorithms in healthcare telemonitoring has the potential to revolutionize patient care. However, future work should focus on scalability and interoperability for diverse healthcare settings.

Continuous light-guide control of melts temperature in induction furnaces

The article is devoted to the question of the most effective for the full use of the induction furnaces technological flexibility continuous temperature control. The aim of the work is to create a light-guide technology for continuous temperature control of the processes of induction melting, treatment and pouring of liquid metal in metallurgy of machine building. The investigations of crucible and channel, melting, holding and pouring induction furnaces from the standpoint of light-guide thermometry have been developed. Materials, designs, as well as technologies of manufacturing, mounting and safe operation of the light-guide and auxiliary devices have also been investigated. Using the results of complex studies, the base light-guide thermometry system, general and particular methods of the light-guide temperature measurements have been developed. On the base of the Huygens construction, as well as the laws of geometric and crystal optics, techniques for calculation of the optical characteristics of the light-guide and focusing devices, as well as schemes of their optical joint have been developed. These techniques increase the metrological characteristics of the light-guide thermometry. Standard construction of the secondary part of thermometry system requires classical pyrometry methods application. These methods are acceptable for continuously operated metallurgical aggregates, where stable emissivity of the light-guide operating end takes place. The secondary part of thermometry system has been modernized in order to widen application field of light-guide thermometry on periodically operated metallurgical aggregates where emissivity of light-guide immersion end randomly changes. Modernized secondary part is purposed for spectral (multicolor) pyrometry methods realization. These methods minimize influence of the instability of emissivity of light-guide immersion end on methodical errors of temperature measurements. Research and industrial exploitation, at domestic and foreign enterprises, have shown obvious metrological advantages of the light-guide thermometry technology in comparison with known solutions. Implementation of the light-guide thermometry systems on induction furnaces has high technical-economic efficiency, including by reduction the spoilage of metal products and resource costs for production. Keywords: induction furnace, continuous temperature control, light-guide thermometry, amorphous, poly- and single-crystalline materials, measurement error, Huygens construction, technical-economic efficiency.

Management of thermal drift of bolometric infrared cameras: limits and recommendations

ABSTRACT In this article, the authors propose a general framework for checking the calibration of the A325sc camera and then minimizing the temperature measurement errors due to thermal drift. Thermal drift and non-uniformity affect the measurement accuracy of infrared bolometric cameras and remain a major problem for the reproducibility and repeatability of radiance quantification. Any thermal camera is pre-calibrated at the factory to correct for thermal drift. This pre-calibration was done for specific case temperatures, and variations in these temperatures are a major source of uncertainty. To improve the accuracy of the camera measurements, it’s important to control the housing temperatures. To this end, a cold box was build up. The effectiveness of the thermal drift compensation was examined over the two ranges of the camera. In the [-20°C; 120°C] range, the thermal drift compensation is efficient up to 110°C. The range [0°C; 350°C] highlights two behaviors: for an emitting temperature within [65-225] °C, the thermal drift compensation is made difficult by the self-heating of the measurement chain due to the intensity of the source. Above 225°C, the self-heating of the optics is significant, as it becomes more absorbent. A correction of the thermosignal is suggested.

Rayleigh Doppler Lidar Technology Based on a Quadruple Dual-pass Fabry–Perot Interferometer

A novel Rayleigh Doppler lidar technology based on a quadruple dual-pass Fabry–Perot interferometer (FPI) that can accurately measure wind field, temperature and aerosol backscatter ratio from the troposphere to lower stratosphere is proposed. This study aims to analyse the detection principle of wind speed, temperature and aerosol backscatter ratio in detail and obtain their measurement error formulas. The structure of this type of lidar is studied and designed. The FPI consists of two edge channels FPI-1 and FPI-2, aerosol channel FPI-M and locking channel FPI-L. FPI-1, FPI-2 and FPI-M use a dual-pass optical path, whereas FPI-L uses a single-pass optical path. The parameters of FPI are optimised as follows: the free spectral spacing (FSR) is 12 GHz, the FWHM of FPI-1 and FPI-2 are both 2.2 GHz, the peak-to-peak interval of FPI-1 and FPI-2 is 5.8 GHz, the FWHM of FPI-M and FPI-L are both 1.2 GHz, the peak-to-peak interval of FPI-M and FPI-1 is 2.9 GHz and the peak-to-peak interval of FPI-L and FPI-1 is 2.3 GHz. Under simulated atmospheric conditions, for a daytime sky background brightness of 0.3 Wsr−1m−2nm−1 at 355 nm, using a laser with a pulse energy of 350 mJ and a repetition frequency of 50 Hz and a telescope with a 0.45-m aperture, with a vertical range resolution of 30 m at 0–10 km, 100 m at 10–20 km and 500 m at 20–35km, temporal resolution of 30 min, zenith angle of 0° for temperature and aerosol backscatter ratio detection and temporal resolution of 3 min and zenith angle of 30° for radial wind speed detection, the detection performance of the designed Rayleigh Doppler lidar is determined. The simulation results show that the measurement errors of aerosol backscatter ratio, temperature and radial wind speed of the lidar system in the daytime and night-time are less than 4.36 × 10−3 and 3.32 × 10−3 (excluding cirrus cloud area), 4.0 K and 3.0 K and 3.8 m/s and 1.9 m/s, respectively, from an altitude of 0.06 to 35km.

Design and Implementation of Temperature Sensor Based on Dynamic Current Gain Compensation Technology

Complementary metal oxide semiconductor (CMOS) temperature sensors are widely used in on-chip systems for their low cost, high integration and low power consumption. A temperature sensor based on parasitic transistor front-end and dynamic current compensation technology is proposed in this paper, which is used to detect temperature in CMOS bipolar junction transistor. In this paper, the parasitic bipolar junction transistor (BJT) device in CMOS process and its temperature sensing principle are introduced, and a temperature sensor based on BJT temperature sensing front-end and dynamic current compensation technology is proposed. In this scheme, the high-resolution current comparator dynamic current compensation technology is used instead of the large capacitance which is necessary in the traditional current domain temperature sensor, which not only ensures the accuracy of the temperature sensor, but also ensures the accuracy of the temperature sensor, it also saves area and power consumption. The sensor’s control circuit uses a novel bucket search algorithm that allows current measured temperature values to be obtained by comparing as few times as possible. In addition, threshold setting technology is adopted to further improve the temperature sensing accuracy with lower power consumption and area cost. In the end, the test results and analysis are introduced. The CMOS temperature sensor proposed in this paper has been used in the standard 55 nm CMOS process. The test results show that the temperature range from −15 °C to 90 °C, the temperature measurement error is ± 0.5 °C and the area is only 0.021 mm2 after single point calibration.

Numerical simulation of laser heating effect in optical temperature measurement based on Kubelka-Munk theory

The fluorescence intensity ratio (FIR) technique is widely used in many fields as one of the sensing methods of phosphor thermometry. In the gas turbine field, the rare earth ions are often doped to thermal barrier coating (TBC). When excited by laser pulses TBC glows phosphorescent, and it can be utilized for thermometry. The laser energy absorbed by the TBC is not only used to generate the luminescence but also introduces heat into the TBC and causes a temperature rise further increasing optical temperature measurement error. Therefore, it’s essential to predict the temperature rise and the temperature measurement error, and take measures to reduce the error due to the laser heating effect. However, there are few researches concerning this problem, and most of them focus on the relationship between the laser energy and the point temperature measured by the FIR technique. Here we show a method for evaluating the effect of laser heating on temperature fields and optical temperature measurement errors by establishing thermal equivalent model and discrete model of body luminescence, considering laser and phosphorescence scattering in coatings made of YSZ based on Kubelka-Munk theory. We found that continuous pulsed laser heating caused severe temperature rise and significant temperature measurement error. Furthermore, the temperature rise can be decreased to the level of a single pulsed laser heating by decreasing the frequency of laser. In addition, the main influencing factors of the temperature measurement error are the density of laser energy and coating thickness.