Infrared Temperature Measurement Research Articles

Research on the error influence mechanism of infrared temperature measurement of turbine guide vanes with end walls

Research on the error influence mechanism of infrared temperature measurement of turbine guide vanes with end walls

Infrared temperature measurements on fast moving targets: A novel calibration approach

In this study, an infrared system is developed for accurate measurements of surface temperature and heat transfer on fast moving targets. The system was designed for the Oxford Turbine Research Facility, a world-leading experimental facility delivering highly engine representative, scalable heat transfer results for aerospace research. Infrared thermography is employed to acquire temperature maps of high-pressure turbine blades, allowing assessment of surface thermal conditions including heat transfer coefficient, adiabatic wall temperature, Nusselt number, cooling effectiveness, and metal effectiveness.Achieving accurate infrared thermography measurements in rotating turbomachinery experimental conditions is arduous due to reflections from the surroundings, low emissivity of metallic parts, and motion blur resulting from high speed. To overcome these challenges, calibration procedures were developed against a traceable standard using a bespoke steady experimental facility. A method to determine the reflected temperature from surroundings was also validated. Correction for all measurement disturbances is demonstrated to within the accuracy of the primary measurement thermocouple.Finally, the developed calibration method was validated on a fast-moving rotating geometry demonstrating accurate correction for all measurement disturbances, without the need for an in situ calibration. A detailed uncertainty analysis for each calibration step is also presented.

Effective resistance design and performance evaluation of energy conversion components

The safety and reliability of the initiating explosive devices (IEDs) are critical for the weapon system. As the core components of IEDs, the method of resistance designing and the performance of conversion energy of energy conversion components (ECCs) are worth being studied. In this paper, the design method for the resistance of ECCs is established based on the finite element discrete method, and the currents of melting and electric explosion are presented for evaluating the performance of ECCs. The results show that the resistance of the ECCs is 1 ± 0.05 Ω with consistency. The ECCs were designed by the established design method of resistance and manufactured by the established machining method. The melting current of ECCs is 1.8 A, which is calculated by the infrared temperature measurement and finite element simulation. The electric explosion current of ECCs is 5 A, which was obtained by combining the snapshot obtained via the high-speed camera and finite element simulation.

The Study of Tool Wear Mechanism Considering the Tool–Chip Interface Temperature during Milling of Aluminum Alloy

ADC12 aluminum alloy has been widely used in the aerospace, ship, and automotive fields because of its high specific strength, excellent die-casting performance, and wear resistance. Adhesion wear is the main wear mechanism of high-speed milling ADC12 aluminum alloy. The most important factor affecting adhesion wear is the tool–chip interface friction, which is directly manifested in the tool–chip interface temperature. Therefore, the temperature variation during the milling of aluminum alloy is analyzed using a temperature field model and infrared temperature measurement technology. Then, the tool wear morphology and the tool wear land width are observed using a scanning electron microscope. Finally, the tool wear mechanism considering the tool–chip interface temperature is discussed. The tool–chip interface temperature is related to the friction angle, tool–chip contact length, and friction force at the rake face, which increases first and then decreases as the cutting speed and feed rate increase. During the formation of the adhesive layer, the tool–chip interface temperature increases, the change rate of the cutting force and the tool wear rate increase, and adhesion, oxidation, and abrasive and delamination wear are generated on the tool surface. With the increase in temperature, the tool wear rate increases, the molten adhesive layer on the tool surface is accompanied by crack propagation, and adhesion wear, oxidation wear, and abrasive wear occur on the tool surface.

Volcanic Diffuse Volatile Emissions Tracked by Plant Responses Detectable From Space

AbstractVolcanic volatile emissions provide information about volcanic unrest but are difficult to detect with satellites. Volcanic degassing affects plants by elevating local CO2 and H2O concentrations, which may increase photosynthesis. Satellites can detect plant health, or a reaction to photosynthesis, through a Normalized Difference Vegetation Index (NDVI). This can act as a potential proxy for detecting changes in volcanic volatile emissions from space. We tested this method by analyzing 185 Landsat 5 and 8 images of the Tern Lake thermal area (TLTA) in northeast Yellowstone caldera from 1984 to 2022. We compared the NDVI values of the thermal area with those of similar nearby forests that were unaffected by hydrothermal activity to determine how hydrothermal activity impacted the vegetation. From 1984 to 2000, plant health in the TLTA steadily increased relative to the background forests, suggesting that vegetation in the TLTA was fertilized by volcanic CO2 and/or magmatic water. Hydrothermal activity began to stress plants in 2002, and by 2006, large swathes of trees were dying in the hydrothermal area. Throughout most of the 1990s, the least healthy plants were located in the area which became the epicenter of hydrothermal activity in 2000. These findings suggest that plant‐focused measurements are sensitive to minor levels of volcanic unrest which may not be detected by other remote sensing methods, such as infrared temperature measurements. This method could be a safe and effective new tool for detecting changes in volatile emissions in volcanic environments which are dangerous or difficult to access.

Identification of cladding layer offset using infrared temperature measurement and deep learning for WAAM

In the wire arc additive manufacturing (WAAM) procedure, the stability of the cladding layer’s formation directly impacts the final dimensional precision of the WAAM weldment. To achieve high-precision forming of the WAAM weldment, online monitoring of the cladding layer offset is essential. This article explores the monitoring technology for the cladding layer offset in the WAAM process and introduces a cladding layer offset monitoring technique using infrared temperature measurement and deep learning. First, a temperature field measurement system for the WAAM weldment is set up using an infrared thermal imager. Next, a region of interest (ROI) is selected on the weldment sidewall. The optimised histogram of oriented gradient (HOG) algorithm is then employed to extract the temperature distribution characteristics of the ROI. The separability of the temperature field on the weldment sidewall is analysed under various offset degrees of the cladding layer. Finally, using the temperature image of the ROI as input, a cladding layer offset recognition model is developed using a convolutional neural network (CNN). This study also evaluates the effect of the selected ROI position on the recognition precision of the model for the cladding layer offset. Experimental results indicate that the recognition accuracy of the model for cladding layer offset, as presented in this article, exceeds 99%. Moreover, the model demonstrates strong robustness, further enriching the intelligent monitoring methods for the WAAM process.

Infrared detection of tungsten cracking on actively cooled ITER-like component during high power experiment in WEST

The consequences of tungsten (W) damaging processes, such as cracking and melting, on divertor lifetime and plasma operation are high priority issues for ITER. A sustained melting experiment was conducted in WEST using a 2 mm deep groove geometry on the upstream mono-block (MB) to overexpose the sharp leading edge (LE) of the downstream MB. W-cracking has been evidenced for the first time with a very high spatial resolution infrared camera before tungsten melting was reached. These cracks develop when the monoblock temperature is about 2600 °C, thus higher than both ductile to brittle transition and softening threshold of tungsten, suggesting that these cracks are different from the ones observed in previous campaigns where brittle failure was involved, because of transient events on cold monoblock. Post-exposure analyses have been performed on the damaged monoblock, highlighting 12 main cracks on the LE, with a width varying from 33 µm to 77 µm, and an average spacing of 0.45 mm. Parallel heat flux about 90 MW/m2 has been derived from infrared temperature measurements, with a heat flux decay length on the target of 4 mm. The T-REX modelling code suggest here that with these thermal inputs, a crack can initiates due to thermal cycling without disruption, with a ductile failure, under 1 to 5 cycles for a tungsten DBTT varying from 400 °C to 500 °C.

Energy balance determination of crop evapotranspiration using a wireless sensor network

Determining crop evapotranspiration (ET) is essential for managing water at various scales, from regional water accounting to farm irrigation. Quantification of ET may be carried out by several procedures, being eddy covariance and energy balance the most established methods among the research community. One major limitation is the high cost of the sensors included in the eddy covariance or energy balance systems. We report here the development of a simpler device (CORDOVA-ET: COnductance Recording Device for Observation and VAlidation of ET) to determine crop ET based on industrial-grade, commercial off-the-shelf (COTS) sensors costing far less than research-grade sensors. The CORDOVA-ET contains a sensor package that integrates the basic micrometeorological instrumentation and the infrared temperature sensors required for estimating ET over crops using the energy balance approach. One novel feature is the presence of four different nodes that allow the determination of ET in four different locations within a field or in four different fields of the same crop, thus allowing an assessment of ET spatial variability. The system was conceived as an open-source and hardware alternative to commercial devices, using a collaborative approach for the development of a regional ET network in countries of North Africa and the Near East. Comparisons of radiation, temperature, humidity, and wind against those of research-grade sensors yielded excellent results, with coefficients of correlation (R2) above 0.96. The estimated reference ET calculated from these measurements showed R2 = 0.99 and a root mean square error (RMSE) of 0.22 mm/day. The infrared temperature measurements at the four different nodes showed an RMSE below 0.56°C. The energy balance components and estimates of ET from the CORDOVA-ET were validated against an eddy-covariance system over a wheat crop. The high (R2) for net radiation (0.98), sensible heat (0.88), and latent heat (0.86) showed good agreement between the modeled energy fluxes and the field measurements. The hardware components, acquisition, and data processing software are available as open-source repositories to facilitate adoption for different applications, from water use efficiency research to irrigation management.

Prediction of Isotropic Rough Surface Directional Spectral Emissivity with Surface-Morphology-Dependent Modelling

The surface directional spectral emissivity of rough metal surfaces in industry is of concern in infrared temperature measurement. In this research, the height and slope possibility density functions are introduced as variables, and the directional spectral emissivity of isotropic rough surface is modelled accordingly. The model is designed to derive the directional spectral emissivity of rough metal surfaces from the surface morphology (possibility distribution of the height and slope) and the material property parameters (refractivity). Then, a sandblasted surface is taken as a case study. The sandblasted surface morphology is measured. A Polynomial surface is proposed to describe the sandblasted surface morphology and is compared with a Gaussian surface and a Cox–Munk surface. Finally, the directional spectral emissivity measurement and infrared temperature measurement are conducted. It is shown that the predicted directional spectral emissivity and measured temperature with the surface-morphology-dependent isotropic rough surface directional spectral emissivity model have high precision. In this work, the possibility distribution of the height and slope of the surface is introduced as independent variables to provide better accuracy compared to the reported models. In some cases, the error of the infrared temperature measurement could be reduced to 20% (80 degrees, compared to Gaussian surface). This work contributes to improving the accuracy of IR temperature measurement of rough surfaces.

Protection Performance Investigation of an Infrared Temperature Measurement Probe for Gas Turbine

For the temperature monitoring requirements of gas turbine blades, a new infrared temperature measurement probe structure is designed in this paper. Cooling air is used to cool the probe and prevent flue gas flowing into the probe. The computational fluid dynamics method is used to analyze the working process of the temperature probe. Two cases that the optical opening of probe is facing to and on the back of flue gas are considered. The influences of the air inlet total pressure on the pollution protective performance and thermal protective performance of the probe are analyzed. The results show that when the optical opening of probe is facing to flue gas, the pollution protective performance is poorer while the thermal protective performance is better than that when facing to gas. According to the temperature distribution of the probe, three optimization schemes of the probe are proposed: spraying thermal barrier coating on the wall of the probe, drilling film holes at the bottom of the probe, and combining film holes with thermal protective performance. The results show that the probe maximum temperature is reduced by 97, 187 and 328 K by using these three methods, respectively.

Study on infrared emissivity model based on perturbation method and Kirchhoff approximation and its application in aluminum alloy welding

Infrared temperature measurement ubiquitously finds applications across multifarious domains. The surface infrared emissivity constitutes the critical parameter influencing the precision of infrared temperature measurement. Therefore, investigating the surface infrared emissivity is of tremendous significance. This paper establishes an infrared emissivity analytical model for rough texture surfaces by considering the repercussions of roughness on the infrared emissivity of material surfaces. First, power spectrum analysis of random roughness is performed. The positive and negative power law components of the rough surface model are constructed using the Monte Carlo method and fractal theory, respectively. Second, based on the perturbation method and Kirchhoff approximation, the infrared emissivity model for rough textured surfaces is established. Third, the infrared emissivity of rough textured surfaces with different fractal dimensions (D), characteristic length scales (G), and surface textures is simulated using the FDTD optical simulation software to validate the efficacy of the infrared emissivity model. Finally, the infrared emissivity model is applied to the temperature measurement system of aluminum alloy friction stir welding. The infrared measurement precision before and after rectification is contrasted and scrutinized to validate the accuracy of this model.

A response function expansion method for cooled IRFPA with multiple neutral density filters under a variable integration time

Infrared focal plane array (IRFPA) radiometric calibration is necessary to achieve infrared temperature measurements; however, the traditional method requires separate calibrations of the response functions for different integration times. In this study, based on the response model of a cooled IRFPA, the relationship between the response function (CRF), integration time, and transmittance was presented. The results demonstrated that the mean absolute percentage error (MAPE) of the expansion method with different neutral density filters under a variable integration time was 1.95 %. The MAPE of the expansion method with only changing the integration time was 1.27 %, and that with only changing the neutral density filters was 1.39 %. In addition, the CRF expansion method was applied to infrared temperature measurements, demonstrating that the relative error was less than ±1.5 % in the ambient temperature range and less than ±1 % in the higher temperature range.

A Comparative Study of Abnormal Heating Composite Insulators.

The abnormal heating of composite insulators on transmission lines frequently occurs, seriously threatening the power grid's safe and stable operation. For different types of abnormal heating composite insulators, undifferentiated replacement wastes a lot of labor and material resources. This study explores the abnormal heating composite insulators under different environmental humidity and wind speed conditions. The heating and discharge of composite insulators are observed, and the heating range, heating shape, and temperature rise (ΔT) are analyzed. The abnormal heating of the sheath-aging composite insulator is related to the aging of the silicone rubber and the environmental humidity. The partial discharge caused by the core rod's defect is the primary source of the temperature rise in the decay-like insulator. The heating range of the contaminated insulator is connected to the environmental humidity, and the ΔT increases with the salt density. The ΔT and heating range of the three types of abnormal heating increase with the ambient humidity. The heating phenomenon under low humidity is an important characteristic that distinguishes decay-like and contaminated insulators from sheath-aging insulators. Therefore, the on-site infrared inspection should be carried out in sunny and windless weather to prevent the impact of high humidity and wind speed on infrared temperature measurement.

Design of mask recognition and temperature monitoring system

This design is based on the STM32F103C8T6 mask recognition and temperature monitoring system, mainly including the mask recognition module based on the K210 chip, non-contact infrared temperature sensor module based on the ATmega328P chip, liquid crystal display module, infrared tube sensor module and buzzer module. When the infrared tube sensor senses the measured target, the system starts to supply power to ATmega328P. The infrared temperature measurement sensor module MLX90164 is used to measure the temperature of the target. At the same time, the temperature data is displayed on the LCD1602 display screen. If it exceeds the predetermined value, an alarm will be issued. When the temperature is normal, the system starts to supply power to K210, start the camera, lock the face position, identify whether the target is wearing a mask, and display the measured results through the 2.4-inch TFT screen. If the mask is worn correctly, the face frame will turn green. Through the software program, the three chips are mobilized for coordinated operation, the target body temperature is measured by using the temperature compensation algorithm, and the mask recognition is carried out by using the YoloV2 algorithm. The hardware design and software program design are improved, and finally, the material object is made. After repeated debugging of the real object, the expected effect is finally achieved. After gradual product improvement, it will be widely used in the daily monitoring of mask wearing identification and body temperature detection in the normalization of epidemic prevention and control in public places in the future.

Analysis and optimization of temperature measurement distance on the infrared temperature measurement accuracy of a building envelope

Due to the measuring distance, there are variable degrees of temperature measurement differences when infrared temperature monitoring technology is employed to take the temperature of a building envelope, which can directly lead to distortion in the detection of the building envelope temperature. In order to address this issue, temperature data from 20 sets of different measurement locations were acquired through field testing analyzing the building envelope and the interior latex-painted wall. By fitting polynomials to the temperature error and distance curves, a model of the temperature-distance compensation function was produced. According to the results, it is possible to precisely estimate the temperature of latex-painted interior walls at a distance of 0.25 meters using an instrument. The temperature-distance compensation model is executed as the measurement distance increases, resulting in a maximum error rate of 1% for temperature readings after compensation. Before adjustment, the error rate in measuring temperature was 4.9%; after adjustment, it is 3.9%.

Rapid bubble growth within 200 μs in flat microchannels under “hot spot” heating conditions at ultra-high heat fluxes

The two-phase flow boiling in microchannels is an attractive cooling strategy for high-power density electronic/optoelectronic devices, while the exist of sub-millimeter “hot spots” characterized by ultra-high heat fluxes would degrade the reliability and safety for commercial and consumer applications. In this paper, the bubble nucleation and evolution characteristics of subcooled flow boiling in high aspect ratio flat microchannels were experimentally studied with the aid of high-speed visualization and infrared temperature measurement at localized heat fluxes exceeding 1.5 kW/cm2. Dielectric liquid HFE-7100 was used at mass flow rates ranging from 11.1 to 178.2 kg/(m2·s). Results show that the explosive boiling process was accompanied by an approximately linear bubble growth rate of about 20 m/s at about the first half of growth stage, and the time duration for overall bubble growth was less than 200 μs. The bubble nucleation was suppressed dramatically on the smooth bottom surface of the channel even at a localized “hot spot” heat flux above 2.5 kW/cm2. The introduction of staggered short micro-pin fin arrays at the bottom wall significantly lowered the threshold heat flux and onset temperature of bubble nucleation and reinforced the bubble growth to larger sizes. It is attributed to the reduction in the temperature gradient of thermal boundary layer adjacent to the heated wall, and it would be further reduced by increasing the micro-pin fin denseness. Even at quite high superheats on smooth and micro-structured surfaces, the heterogeneous boiling mechanism was proved to still work.

Adaptive Compensation Method for the Infrared Temperature Measurement Error Based on 3-D Thermal Imaging

Infrared thermal imager can provide two-dimensional temperature information of the measured object on-line without contact, which is one of the most commonly used temperature measurement methods. However, the measuring distance and viewing angle between the thermal imager and the measured object will cause the infrared temperature measurement error. In order to automatically compensate for the temperature measurement error caused by measuring distance and viewing angle when the infrared thermal imager is applied in actual measurement scenarios, this paper proposes an adaptive compensation method for the infrared temperature measurement error based on 3D thermal imaging. Firstly, based on the polynomial regression and infrared temperature measurement principle, a compensation model is established to compensate for the temperature measurement error caused by measuring distance and viewing angle. Secondly, the parameters of the compensation model are determined by using a blackbody furnace and a reference cylinder. Then, a 3D thermal imaging system is constructed with a depth camera and an infrared thermal imager to quantify the measuring distances and viewing angles between all temperature pixels and the thermal imager. Finally, the surface temperature of the measured object can be adaptively compensated using the established compensation model. The experimental results of the blackbody furnace and resin cylinder show that the proposed method can adaptively compensate for the infrared temperature measurement error caused by measuring distance and viewing angle.

Application of infrared temperature measurement in the rubber mixer

Rubber temperature is an important parameter affecting the mixing degree of rubber in mixer. In the mixing process, there is a significant error between the thermocouple temperature and the actual temperature, which will affect the degree of rubber mixing. In order to solve this problem, this paper designs a set of non-contact infrared temperature measuring device to measure the rubber temperature in mixing process. The experimental results show that the temperature rise and discharge temperature of the compound measured by the infrared temperature measuring device are more in line with the actual situation. Compared with the actual discharge temperature, the measurement error of the infrared temperature measuring device is less than 4 %, while the error of the thermocouple temperature measuring device is more than 11 %. Therefore, the infrared temperature measuring device is more suitable for the rubber's dynamic temperature measurement process in the mixer.

Study of Atmospheric Pressure Plasma Temperature Based on Silicon Carbide Etching.

In order to further understand the excitation process of inductively coupled plasma (ICP) and improve the etching efficiency of silicon carbide (SiC), the effect of temperature and atmospheric pressure on plasma etching of silicon carbide was investigated. Based on the infrared temperature measurement method, the temperature of the plasma reaction region was measured. The single factor method was used to study the effect of the working gas flow rate and the RF power on the plasma region temperature. Fixed-point processing of SiC wafers analyzes the effect of plasma region temperature on the etching rate. The experimental results showed that the plasma temperature increased with increasing Ar gas until it reached the maximum value at 15 slm and decreased with increasing flow rate; the plasma temperature increased with a CF4 flow rate from 0 to 45 sccm until the temperature stabilized when the flow rate reached 45 sccm. The higher the RF power, the higher the plasma region's temperature. The higher the plasma region temperature, the faster the etching rate and the more pronounced the effect on the non-linear effect of the removal function. Therefore, it can be determined that for ICP processing-based chemical reactions, the increase in plasma reaction region temperature leads to a faster SiC etching rate. By processing the dwell time in sections, the nonlinear effect caused by the heat accumulation on the component surface is effectively improved.

Study on Temperature Measurement Model of Rare Earth Metal Electrolysis Based on Infrared Image

The temperature of rare earth electrolysis plays an important role in the process of electrolysis control. It is the main parameter to control the efficiency of electrolysis. In production practice, most of the process parameters are controlled by the artificial thermocouple temperature measurement method. This extensive technical management method greatly affects the accuracy of production control. And the traditional thermocouple temperature measurement is artificial and slow, not timely, short life, and has other issues. Therefore, it is extremely urgent to explore a continuous and safe surface temperature measurement method to achieve precise control of process parameters. Therefore, based on the principle of infrared temperature measurement, this paper introduces the theory of infrared temperature measurement, uses Matlab software to extract the average gray value of the infrared image, and obtains the infrared temperature measurement model by least square method and bp neural network for temperature and gray fitting curve. At the same time, the experimental data are measured, and the model is verified. This method provides a reference for online temperature measurement of electrolytic molten metal.