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1
Bhattacharjee, S., M. King, W. Cobb, R. A. Altenkirch i K. Wakai. "Approximate Two-Color Emission Pyrometry". Journal of Heat Transfer 122, nr 1 (2.08.1999): 15–20. http://dx.doi.org/10.1115/1.521431.
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Approximate methods for the determination of a temperature field using pure emission pyrometry applied to a two-dimensional nonoptically thin flame without variation along a line of sight are presented. In the absence of an absorption measurement, emission pyrometry depends on theoretical spectral information. Limitations of existing techniques stem from the fact that spectral information is a function of temperature only for the optically thin situation, by and large the situation to which current techniques apply, and temperatures above 1000 K. Through extensive narrow-band calculation using a simulated flame over polymethylmethacrylate, we show that the spectral information contained in the equivalent bandwidth ratio is approximately a constant for the 2.8 μm/1.8 μm band pair and appropriate bandwidths. The constant can be evaluated from emission measurements at a point where the temperature is known or can be estimated using, e.g., the maximum flame temperature of a simulated flame and the peak band intensities. The temperature field evaluated with this approximately constant value of the equivalent bandwidth ratio, Ar, is accurate to within five percent for temperatures down to 450 K. [S0022-1481(00)02601-3]
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Khosravi, Mahdiar, i Patrick Kirchen. "Refinement of the two-color pyrometry method for application in a direct injection diesel and natural gas compression-ignition engine". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 233, nr 14 (11.03.2019): 3787–800. http://dx.doi.org/10.1177/0954407019832774.
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The soot emissions from internal combustion engines have significant health and environmental impacts and, as such, are subject to increasingly stringent regulations. Two-color pyrometry provides the in-cylinder soot cloud temperature and soot volume fraction and can provide insight to the in-cylinder soot formation and oxidation processes to guide research for reducing engine-out soot emissions. This work demonstrates improvements to the two-color pyrometry methodology, with a focus on low-temperature, low-soot regimes such as low-temperature combustion or combustion of direct injected natural gas. Through selection of a fast and robust numerical algorithm, characterizing and increasing the detection envelope, performing static and dynamic perspective adjustments, accounting for non-uniform and non-linear system response, as well as localized signal-to-noise ratio enhancement through image filtering, the performance of the pyrometric method was improved by a 40% increase in the resolved signal fraction. The refined two-color method was evaluated for both direct injected diesel and natural gas fueling strategies using a pilot-ignited direct injected natural gas fuel system and facilitated evaluation of local temperatures and soot concentrations in pilot-ignited direct injected natural gas combustion, despite the generally low soot levels in this combustion strategy.
3
Deep, Sneh, i Gopalan Jagadeesh. "Spatially resolved solid-phase temperature characterization in a sillimanite tube furnace using a broadband two-color ratio pyrometry". Review of Scientific Instruments 90, nr 7 (lipiec 2019): 074903. http://dx.doi.org/10.1063/1.5088149.
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Deep, Sneh, Yedhu Krishna i Gopalan Jagadeesh. "Temperature characterization of a radiating gas layer using digital-single-lens-reflex-camera-based two-color ratio pyrometry". Applied Optics 56, nr 30 (19.10.2017): 8492. http://dx.doi.org/10.1364/ao.56.008492.
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Shim, Hanseul, Sanghoon Lee, Jae Gang Kim i Gisu Park. "CO2 number density measurement in a shock tube with preheated carbon surface". Physics of Fluids 34, nr 6 (czerwiec 2022): 067105. http://dx.doi.org/10.1063/5.0095517.
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The interaction between a heated carbon-based material and high-temperature air may produce ablation gas species such as CO2, affecting heat transfer onto the surface of a thermal protection system. The prediction of ablation gas production is critical for heat flux prediction and the design of a thermal protection system. In this study, we present a system that measures the number density of CO2 formed by the gas–surface interaction between a hot carbon surface and high-temperature gas. The heated carbon wall is exposed to high-temperature air by using a shock tube and surface heating model. The surface temperature of the carbon wall is measured using two-color ratio pyrometry. The number density of CO2 is predicted by performing numerical calculations for the shock tube flow with gas–surface interaction modeling. The number density of CO2 molecules is measured using infrared emission spectroscopy. The measured CO2 number density is 9.60 × 1023 m−3 at an area-weighted average surface temperature of 1212 K. The measured number density matches the predicted value within an error of 6%. The proposed system is applicable for CO2 number density measurement under various gas–surface interaction conditions, and it can be used for the investigation of ablative gas production and numerical research on gas–surface interactions.
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Ngo Huu, Manh, Anh Nguyen Van, Tuan Nguyen Van, Dang Tran Hai, Thanh Nguyen Van, Dung Nguyen Tien i Thanh-Hai Nguyen. "Material Flow Behavior on Weld Pool Surface in Plasma Arc Welding Process Considering Dominant Driving Forces". Applied Sciences 10, nr 10 (21.05.2020): 3569. http://dx.doi.org/10.3390/app10103569.
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In this study, the effect of oxygen in the shielding gas on the material flow behavior of the weld pool surface was discussed to clarify the dominant driving weld pool force in keyhole plasma arc welding (KPAW). To address this issue, the convection flow on the top surface of weld pool was observed using a high-speed video camera. The temperature distribution on the surface along keyhole wall was measured using the two-color pyrometry method to confirm the Marangoni force activity on the weld pool. The results show that the inclination angle of the keyhole wall (keyhole shape) increased especially near the top surface due to the decrease in the surface tension of weld pool through surface oxidation when a shielding gas of Ar + 0.5% O2 was used. Due to the change in the keyhole shape, the upward and backward shear force compositions created a large inclination angle at the top surface of the keyhole. From the temperature measurement results, the Marangoni force was found to alter the direction when 0.5% O2 was mixed with the shielding gas. The shear force was found to be the strongest force among the four driving forces. The buoyant force and Lorentz force were very weak. The Marangoni force was stronger than the Lorentz force but was weaker than shear force. The interaction of shear force and Marangoni force controlled the behavior and speed of material flow on the weld pool surface. A strong upward and backward flow was observed in the case of mixture shielding gas, whereas a weak upward flow was observed for pure Ar. The heat transportation due to the weld pool convection significantly changed when only a small amount of oxygen was admixed in the shielding gas. The results can be applied to control the penetration ratio in KPAW.
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Valke, A. A., D. G. Lobov i A. G. Shkaev. "Color sensor application in high-temperature spectral ratio pyrometer". IOP Conference Series: Materials Science and Engineering 1211, nr 1 (1.01.2022): 012022. http://dx.doi.org/10.1088/1757-899x/1211/1/012022.
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Abstract Contactless thermal control tools play an important role in solving the high-temperature technological processes improving energy efficiency problems. In order to create such controls, the authors analyzed the developing possibility of spectral ratio high-temperature pyrometer using a multispectral radiation receiver (color sensor) TCS34725. In the paper this receiver application coefficients are determined, signals ratio graphs in different spectral intervals on temperature are given for two applications: without additional filtration of the control object radiation infrared component and using an opaque in the infrared spectrum part external filter.
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Zhukov, Leonid, i Dmytro Petrenko. "TWO-COLOR COMPENSATIVE THERMOMETRY WITH CORRECTED ADJUSTMENT USING NONLINEARITY EQUATION OF EMISSIVITY SPECTRAL DISTRIBUTION". Measuring Equipment and Metrology 82, nr 3 (2021): 18–25. http://dx.doi.org/10.23939/istcmtm2021.03.018.
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The article is directed on metrological characteristics increase and extension of the optical thermometry field of use, including two-color compensative thermometry with a priori averaged adjustment. The investigations have been performed for the tungsten. This metal studied in thermometry and metal optics has tabulated quantitative estimations of emissivity which are similar to the most widespread in metallurgy iron-carbon alloys. To increase the reliability and extend the field of use of obtained results, approximated and linearized spectral distributions of tungsten, as well as their mirror representations with decreasing and increasing, convex, linear, and concave distributions of emissivity have been researched. The influence of qualitative and quantitative characteristics of the spectral distributions of emissivity on their nonlinearity coefficient has been studied. The equation of nonlinearity has been obtained. This equation connects the nonlinearity coefficient at the middle wave with the emissivity value at one of the boundary waves through the measured one-color radiation temperatures at 3 operating waves. With a priori knew quantitative estimates of the nonlinearity coefficient at the middle wave and measured onecolor radiation temperatures, the obtained equation can be used for the calculation of emissivity values at the boundary waves. For example, in the linear spectral distributions of emissivity, the nonlinearity coefficient is equal to 0. The number of solutions for linear distributions of emissivity varies from 1 to 2, and for nonlinear – from 1 to 3. The influence of measurement errors of one-color radiation temperatures at operating waves on the errors of emissivity determination by nonlinearity equation is established. The metrological advantages of two-color compensative thermometry using the emissivity values, corrected by the nonlinearity equation, are proved. It was found, that at the nonselective distribution of measurement errors of one-color radiation temperatures, measurement errors of the object temperature for two-color compensative, spectral ratio, and energy thermometry are insignificant for technical measurements. Under conditions of selective distribution of measurement errors of one-color radiation temperatures, these errors respectively are 0.04-0.25 %; 1.66-9.30 %; 0.18-0.34 %. For nonlinear emissivity spectral distributions, real for tungsten and iron-carbon alloys, the methodical component due to the nonlinearity doesn’t exceed 0.48 %, which is also acceptable for technical measurements. The method has been developed for practically acceptable conditions of primary pyrometric information obtaining.
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Schwarzkopf, Karen, Richard Rothfelder, Michael Rasch i Michael Schmidt. "Two-Color-Thermography for Temperature Determination in Laser Beam Welding of Low-Melting Materials". Sensors 23, nr 10 (19.05.2023): 4908. http://dx.doi.org/10.3390/s23104908.
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Spatial and temporal knowledge of temperature evolution is crucial in laser beam welding of low-melting materials such as aluminum alloys. Current temperature measurements are restricted to (i) one-dimensional temperature information (e.g., ratio-pyrometers), (ii) a priori knowledge of emissivity (e.g., thermography), and (iii) high-temperature regions (e.g., two-color-thermography). This study presents a ratio-based two-color-thermography system that enables acquiring spatially and temporally resolved temperature information for low-melting temperature ranges (<1200 K). The study demonstrates that temperature can be accurately determined despite variations in signal intensity and emissivity for objects emitting constant thermal radiation. The two-color-thermography system is further transferred into a commercial laser beam welding set-up. Experiments with varying process parameters are conducted, and the ability of the thermal imaging method to measure dynamic temperature behavior is assessed. Image artifacts presumably caused by internal reflections inside the optical beam path limit the direct application of the developed two-color-thermography system during dynamic temperature evolution.
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Ishii, Naoto, Ryutaro Tanaka, Yuto Kojima, Katsuhiko Sekiya, Keiji Yamada i Shuho Koseki. "Influence of the Cutting Fluid on Tool Edge Temperature in End Milling of Titanium Alloy". Key Engineering Materials 656-657 (lipiec 2015): 296–301. http://dx.doi.org/10.4028/www.scientific.net/kem.656-657.296.
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In this study, tool edge temperature was measured by a two-color pyrometer with an optional fiber and the novel method to evaluate the cooling effect of cutting fluid was proposed. After one cut, the tool edge passes over the fine hole at workpiece where inserted into an optical fiber so that the one peak signal can be obtained by each of two detectors with different spectral sensitivities in the pyrometer. The tool edge temperature can be calculated by taking the ratio of outputs from these two detectors. In previous research dealing with the cutting temperature in end milling obtained by a two-color pyrometer with an optional fiber, the average temperature calculated from some large peak values was used for an index as cutting temperature. However, this method was not suitable to estimate the tool edge temperature in wet milling. In the proposed method, the tool edge temperature was calculated only by the peak signals just after full length cut and used for an index as cutting temperature. The frequency distribution of tool edge temperature was made by the obtained temperature data. Comparing dry cutting to wet cutting, there was almost no difference in maximum temperature but obvious difference in the frequency distribution. The temperature range in wet cutting was wider than that in dry cutting.
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Kottenstette, J. P. "Measuring Tool-Chip Interface Temperatures". Journal of Engineering for Industry 108, nr 2 (1.05.1986): 101–4. http://dx.doi.org/10.1115/1.3187043.
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A two-color pyrometer was developed for monitoring the surface temperature of metal chips formed during high-speed machining processes. Optical access to the tool-chip interface was obtained by cementing a plastic light pipe into a 1/16-in. (1.6-mm) hole milled through the carbide tool insert. The light pipe serves to transmit radiation falling on the rake face of the insert to radiation detectors located elsewhere. Radiation captured by the light pipe is passed through a lens-beam splitter combination and imaged on two identical photodiode detectors. The diodes have integral operational amplifiers to achieve high detectivity and low-noise operation. Each photodiode is masked by an interference type narrow-band filter having spectral bandpass frequencies chosen to match the point where the emittance of several metals is constant for all temperatures. Thus, the temperature of the chip stream monitored by the diodes is a function of the intensity measured for each spectral band at the same instant in time. The functional relationship between true temperature and the ratio of signal amplitudes (the calibration curve) was established for pyrometer over the interval 1000–1750 K using standard laboratory methods.
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Araki, Yosuke, Ryutaro Tanaka, Yuto Kojima, Katsuhiko Sekiya, Keiji Yamada i Shuho Koseki. "Relationship between Cutting Heat and Tool Edge Temperature in End Milling of Titanium Alloy". Key Engineering Materials 749 (sierpień 2017): 15–20. http://dx.doi.org/10.4028/www.scientific.net/kem.749.15.
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In this study, tool edge temperature was measured by a two-color pyrometer with an optional fiber. During one revolution of spindle, the tool edge passes over the fine hole at workpiece after cutting workpiece. An optical fiber inserted into the fine hole transmits infrared ray radiated from tool edge to two detectors with different spectral sensitivities. One peak signal from each detector can be obtained by each spindle revolution. The tool edge temperature can be calculated by taking the ratio of outputs from these two detectors. The relation between cutting heat calculated from cutting force and tool edge temperature was discussed. The tool edge temperature at the same cutting heat could be compared. The wet cutting condition caused lower tool edge temperature than the others at the same cutting heat. MQL and dry showed almost same tool edge temperature. The dispersion of tool edge temperature in wet cutting is wider than that in dry cutting and MQL cutting.
13
Nickel, J., N. Baak, P. Volke, F. Walther i D. Biermann. "THERMAL INFLUENCE ON THE SURFACE INTEGRITY DURING SINGLE-LIP DEEP HOLE DRILLING OF STEEL COMPONENTS". MM Science Journal 2021, nr 3 (30.06.2021): 4636–43. http://dx.doi.org/10.17973/mmsj.2021_7_2021070.
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The thermomechanical load on the workpiece surface during the machining process strongly influences its surface integrity and the resulting fatigue strength of the components. In single-lip drilling, the measurement of the mechanical load using dynamometers is well established, but the thermal interactions between the tool and the workpiece material in the surface area are difficult to determine with conventional test setups. In this paper, the development and implementation of an in-process measurement of the thermal load on the bore subsurface is presented. The experimental setup includes a two-color ratio pyrometer in combination with thermocouples, which enable temperature measurement on the tool’s cutting edge as well as in the bore subsurface. In combination, a force measurement dynamometer for measuring the occurring force and torque is used. Thus, the influence of different cutting parameter variations on the thermomechanical impact on the bore surface can be evaluated.
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Ai, Weiguo, Nathan Murray, Thomas H. Fletcher, Spencer Harding i Jeffrey P. Bons. "Effect of Hole Spacing on Deposition of Fine Coal Flyash Near Film Cooling Holes". Journal of Turbomachinery 134, nr 4 (25.07.2011). http://dx.doi.org/10.1115/1.4003717.
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Particulate deposition experiments were performed in a turbine accelerated deposition facility to examine the nature of flyash deposits near film cooling holes. Deposition on both bare metal and thermal barrier coating (TBC) coupons was studied, with hole spacing (s/d) of 2.25, 3.375, and 4.5. Sub-bituminous coal ash particles (mass mean diameter of 13 μm) were accelerated to a combustor exit flow Mach number of 0.25 and heated to 1183°C before impinging on a target coupon. The particle loading in the 1 h tests was 310 ppmw. Blowing ratios were varied in these experiments from 0 to 4.0 with the density ratio varied approximately from 1.5 to 2.1. Particle surface temperature maps were measured using two-color pyrometry based on the red/gree/blue (RGB) signals from a camera. For similar hole spacing and blowing ratio, the capture efficiency measured for the TBC surface was much higher than for the bare metal coupon due to the increase of surface temperature. Deposits on the TBC coupon were observed to be more tenacious (i.e., hard to remove) than deposits on bare metal coupons. The capture efficiency was shown to be a function of both the hole spacing and the blowing ratio (and hence surface temperature). Temperature seemed to be the dominant factor affecting deposition propensity. The average spanwise temperature downstream of the holes for close hole spacing was only slightly lower than for the large hole spacing. Roughness parameters Ra and Rt decreased monotonically with increased blowing ratio for both hole spacing analyzed. The roughness for s/d=3.375 was lower than that for s/d=4.5, especially at high blowing ratio. It is thought that these data will prove useful for designers of turbines using synfuels.
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Koch, S., F. P. Hagen, L. Büttner, J. Hartmann, A. Velji, H. Kubach, T. Koch, H. Bockhorn, D. Trimis i R. Suntz. "Influence of Global Operating Parameters on the Reactivity of Soot Particles from Direct Injection Gasoline Engines". Emission Control Science and Technology, 11.05.2022. http://dx.doi.org/10.1007/s40825-022-00211-y.
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Abstract The aim of this study is to investigate the impact of global operating parameters, e.g., engine speed, brake mean effective pressure, and air–fuel ratio, of a turbocharged 4-cylinder GDI engine on the reactivity of soot particles against oxidation. The knowledge of soot reactivity is crucial for optimizing gasoline particulate filter regeneration strategies and is, consequently, a key parameter for reducing fuel consumption and CO2 emissions. In this work, time-resolved in-cylinder soot concentrations and exhaust particle size distributions are measured by using two-color pyrometry, engine exhaust particle sizer and smoke meter, respectively. Reactivity against oxidation by molecular oxygen is determined by temperature programmed oxidation analysis. To derive a physicochemical explanation for varying soot reactivity, the morphological and nanostructural primary particle structure of collected samples is analyzed using high-resolution electron microscopy and image analysis algorithms. The results reveal that engine operating parameters affect soot reactivity differently. While engine speed has only a slight effect, a reduction of air/fuel ratio (λ < 1.0) or an increase of BMEP > 10 bar significantly reduces the soot oxidation reactivity. These findings give evidence, that the quality of the fuel/air mixture is a significant parameter influencing soot reactivity. Measured soot concentrations substantiate the hypothesis that low-sooty homogeneous premixed combustion of a homogeneous fuel/air mixture favors formation of high-reactive soot particle fractions. Reactive soot particle aggregates are composed of multiple soot fractions of different reactivity. Reactive primary particles are composed of short graphene-like layers and vice versa, providing a physicochemical explanation for varying soot reactivity depending on engine operating conditions.