Abstract: A simple and compact temperature and soot volume fraction diagnostic technique based on ratio pyrometry has been studied. Two different consumer digital single lens reflex cameras were evaluated for use as pyrometers. The incandescence from soot and a SiC filament was imaged at the three wavelengths of each camera’s color filter array (CFA). After characterization of the detector’s signal response curves, temperatures were calculated by two-color ratio pyrometry using a lookup table approach. A SiC filament with known emissivity was shown to provide an absolute light intensity calibration, which further allows the soot volume fraction to be determined. Measurements were carried out on four different flames with varying levels of soot loading. The filament-derived gas temperature and soot temperature measurements have been compared with computational results and overall good agreement has been shown. Soot volume fraction measurements have been compared with previous LII results, with excellent agreement for both cameras tested.

Abstract: Laser cladding is a multiple-parameter-dependent process, and a feedback control is critical for the process stabilization. This paper presents a generalized predictive control strategy with input constraints to stabilize the melt pool temperature during a high-power diode laser cladding process. A dual-color pyrometer was used to monitor the melt pool temperature. A state-space dynamic model relating the laser drive signal (laser power) to the melt pool temperature was identified experimentally using the subspace method. A generalized predictive controller with input constraints was implemented in real time using the state-space model. The closed-loop process was able to track the melt pool temperature to a reference temperature profile. Laser cladding of H13 tool steel on a substrate with uneven surface showed that the closed-loop process was able to compensate for an under-fill with 3-mm depth after 40-layer depositions.

Abstract: The soot growth region of a premixed one-dimensional ethylene/air flame has been investigated using two-color laser-induced incandescence (2C-LII) with focus on optical soot properties. From the 2C-LII technique, primary soot particle sizes were deduced together with the temperature from pyrometry of the laser-heated particles, while the gas temperatures were obtained from pure rotational CARS nitrogen thermometry. Soot particle sizes were also measured from thermophoretically sampled soot particles analyzed by transmission electron microscopy (TEM), and the results showed growing isolated primary soot particles up to a height of 10 mm, after which strong soot aggregation occurred and the increase in soot primary particle size ceased. The measured data was used in the evaluation of the soot absorption function, E(m), and a strong increase by a factor of two was observed from the lowest heights to the highest for assumed constant values of soot density and specific heat at all heights. By comparing the 2C-LII particle sizes with the sizes obtained from TEM, differences were observed. Part of the explanation is that the 2C-LII evaluation did not take aggregation into account, but it is additionally speculated that the thermal accommodation coefficient decreases with height above burner. These results are interesting in view of morphological and composition changes of the soot during the growth process and have implications for the use of 2C-LII as a soot diagnostic technique. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved. (Less)

Abstract: Growing demands on the quality of thermally sprayed coatings require reliable methods to monitor and optimize the spraying processes. Thus, the importance of diagnostic methods is increasing. A critical requirement of diagnostic methods in thermal spray is the accurate measurement of temperatures. This refers to the hot working gases as well as to the in-flight temperature of the particles. This article gives a review of plasma and particle temperature measurements in thermal spray. The enthalpy probe, optical emission spectroscopy, and computer tomography are introduced for plasma measurements. To determine the in-flight particle temperatures mainly multicolor pyrometry is applied and is hence described in detail. The theoretical background, operation principles and setups are given for each technique. Special interest is attached to calibration methods, application limits, and sources of errors. Furthermore, examples of fields of application are given in the form of results of current research work.

Abstract: A method and system for calibrating temperature measurement devices, such as pyrometers, in thermal processing chambers are disclosed. According to the present invention, the system includes a calibrating light source that emits light energy onto a substrate contained in the thermal processing chamber. A light detector then detects the amount of light that is being transmitted through the substrate. The amount of detected light energy is then used to calibrate a temperature measurement device that is used in the system.

Abstract: Thermite reactions with nano-scale particles have attracted much study due to their high flame temperatures and combustion velocities. The mechanism by which the reaction propagates is not well understood. The reaction temperature, the heating rate, and the reaction zone thickness are critical parameters to understanding the mechanism. Measurements of the reaction temperature for the Al/CuO, Al/MoO 3 , and Al/Fe 2 O 3 nano-thermite systems were made using multi-wavelength pyrometry for two experimental configurations. In one experiment, the radiative emission from the reaction of a small, unconfined pile (∼10 mg) of reacting nano-thermite is collected over a 50 ms integration time and the temperature is measured. In a second experiment, the radiative emission was collected from a single spot, with a diameter of 1.5 mm, on a transparent tube filled with the nano-thermite as the combustion wave passes and the spectrum is temporally resolved using a streak tube and detected using an intensified CCD camera. Temperature traces from these experiments show a temperature ramping period followed by a plateau in temperature. For Al/CuO, the average temperature from the unconfined pile experiment was 2390 ± 150 K, and the average plateau temperature for the temporally resolved measurements was approximately 2250 ± 100 K. For Al/MoO 3 , the unconfined pile experiment yielded an average temperature of 2150 ± 100 K, and the average plateau temperature was the same. The temperature measured from the Al/Fe 2 O 3 unconfined pile experiment was 1735 ± 50 K. The measured temperatures suggest that the gases generated during the reactions are primarily from the decomposition or vaporization of the various metal oxides. Furthermore, for Al/CuO and Al/MoO 3 , which can be classified as ‘fast’ nano-thermites, it was shown that the length scale associated with the temperature rise is much longer than classical conduction driven reactions.

Abstract: A high-speed imaging pyrometer was developed to investigate the behavior of flames and explosive events. The instrument consists of two monochrome high-speed Phantom v7.3 m cameras made by Vision Research Inc. arranged so that one lens assembly collects light for both cameras. The cameras are filtered at 700 or 900 nm with a 10 nm bandpass. The high irradiance produced by blackbody emission combined with variable shutter time and f-stop produces properly exposed images. The wavelengths were chosen with the expected temperatures in mind, and also to avoid any molecular or atomic gas phase emission. Temperatures measured using this pyrometer of exploded TNT charges are presented.

Abstract: A fast fiber-optic multi-wavelength pyrometer was developed for the ultraviolet-visible-near infrared spectra from 200 nm to 1700 nm using a CCD detector and an InGaAs detector. The pyrometer system conveniently and quickly provides the sufficient choices of multiple measurement wavelengths using optical diffraction, which avoids the use of narrow-band filters. Flexible optical fibers are used to transmit the radiation so the pyrometer can be used for temperature measurements in harsh environments. The setup and calibrations (wavelength calibration, nonlinearity calibration, and radiation response calibration) of this pyrometer system were described. Development of the multi-wavelength pyrometer involved optimization of the bandwidth and temperature discrimination of the multiple spectra data. The analysis results showed that the wavelength intervals, Δλ(CCD) = 30 nm and Δλ(InGaAs) = 50 nm, are the suitable choices as a tradeoff between the simple emissivity model assumption and the multiple signal discrimination. The temperature discrimination was also quantificationally evaluated for various wavelengths and temperatures. The measurement performance of the fiber-optic multi-wavelength pyrometer was partially verified through measurements with a high-temperature blackbody and actual hot metals. This multi-wavelength pyrometer can be used for remote high-temperature measurements.

Abstract: The initial design of a novel multivariate sensor is described for the measurement of melt temperature, melt pressure, melt velocity, melt viscosity, and mold temperature. Melt pressure and temperature are respectively obtained through the incorporation of a piezoceramic element and infrared photodetector within the sensor head. Melt velocity is derived from the initial response of the melt temperature as the polymer melt flows across the sensor's lens. The apparent melt viscosity is then derived from the melt velocity and the time derivative of the increasing melt pressure given the cavity thickness. The feasibility of the envisioned sensor is then analyzed using a production-grade mold that is instrumented with commercial piezoelectric pressure sensors, infrared pyrometer, and thermocouples. Several predictive models of part weight are developed using multiple regression of data obtained from a design of experiments to evaluate the capability of the envisioned multivariate sensor. The results i...

Abstract: A novel method to investigate the microwave hybrid sintering process is presented. The method described measures simultaneously over time the changes in shrinkage and temperature field on the sample's surface. The measurements are carried out continuously by using a CCD camera and an IR pyrometer during microwave heating. Moreover, the equipment used is both contactless and less expensive than conventional approaches.

Abstract: A theoretical and experimental analysis of a time resolved thermal wave microscopy (TRTWM) technique used for thermal transport measurements is presented. TRTWM utilizes elements of frequency and time domain laser based thermoreflectance techniques and is well suited to measure both lateral and cross plane thermal transport. A primary advantage of this method is that the pump and probe spot sizes do not have to be known accurately. Implementation of TRTWM to measure thermal transport in oxide substrates coated with thin metal films is demonstrated.

Abstract: Pyrometric measurements of radiance to determine temperature have been performed on shock physics experiments for decades. However, multi-wavelength pyrometry schemes sometimes fail to provide credible temperatures in experiments, which incur unknown changes in sample emissivity, because an emissivity change also affects the spectral radiance. Hence, for shock physics experiments using pyrometry to measure temperatures, it is essential to determine the dynamic sample emissivity. The most robust way to determine the normal spectral emissivity is to measure the spectral normal-hemispherical reflectance using an integrating sphere. In this paper, we describe a multi-wavelength (1.6–5.0 μm) integrating sphere system that utilizes a “reversed” scheme, which we use for shock physics experiments. The sample to be shocked is illuminated uniformly by scattering broadband light from inside a sphere onto the sample. A portion of the light reflected from the sample is detected at a point 12 deg from normal to the sam...

Abstract: A method of in-situ pyrometer calibration for a wafer treatment reactor such as a CVD reactor 12 desirably includes the steps of positioning a calibrating pyrometer 80 at a first calibrating position A and heating the reactor until the reactor reaches a pyrometer calibration temperature. The method desirably further includes rotating a support element 40 about a rotational axis 42, and while the support element is rotating about the rotational axis, obtaining first operating temperature measurements from a first operating pyrometer 71 installed at a first operating position 1R, and obtaining first calibrating temperature measurements from the calibrating pyrometer 80. Both the calibrating pyrometer 80 and the first operating pyrometer 71 desirably are adapted to receive radiation from a first portion of the wafer support element 40 at a first radial distance D1 from the rotational axis 42 of the wafer support element.

Abstract: Embodiments of the present invention generally relate to methods and apparatus for measuring, calibrating, and controlling substrate temperature during low temperature and high temperature processing. In one embodiment, the method includes epitaxially forming a layer stack on a substrate placed on a support plate, measuring a temperature of the substrate with a first pyrometer disposed over the substrate, measuring a temperature of the support plate with a second pyrometer disposed below the support plate, calibrating the first pyrometer at multiple temperature points based on actual temperature readings of the substrate to generate a first set of calibrated temperature readings associated with the substrate, calibrating the second pyrometer using the set of calibrated temperature readings as a reference to generate a second set of calibrated temperature readings associated with the support plate, and controlling a power supplied to a heat source configured to heat the substrate based on the second set of calibrated temperature readings.

Abstract: To get round two main difficulties of the kinetic study of fast reactions of high-temperature decomposition of energetic materials (EM) (spatial non-isothermality and self-inflammation) two new methods for sample preparation called “mechanical dilution” and “thermal dilution” were applied. In the first part of the presentation, some experimental and theoretical data on kinetics of fast high-temperature decomposition of some typical homogeneous and heterogeneous energetic materials (including pyroxylin, ammonia copper chromate, ammonium perchlorate, solid rocket propellants, and others) are given. In a number of cases, kinetic constants of fast reactions dominating at high temperatures were shown to significantly differ from those of low-temperature reactions. The second part of the presentation deals with a new method of thermal analysis—electrothermal analysis (ETA). By using a multi-channel high-speed optical pyrometer, variation of the temperature field in an electrically heated sample of conductive energetic material (or its mixture with metal powder) during its heating followed by thermal explosion is registered. Due to application of this method in the ETA-100 (allowing one to measure kinetic data at the temperature up to 3800 K with a time step as short as 0.1 ms, i.e., for full conversion times as short as 10−3 s) some important patterns of mechanisms of gasless combustion and explosion in SHS-mixtures (Si + C, Ni + Al, and Ti + C) were identified. More details regarding these and some additional important aspects can be found in [1, 2].

Abstract: The results of measurement of fluctuations of brightness temperature T in the region of exposure to laser radiation of a 3 mm-thick steel plate are presented. The local luminosity along the cut-front was measured using two-color multichannel pyrometer. Cutting trials were carried out with CO2 laser (10.6 μm, 1200 W) and fiber laser (1.07 μm, 1800 W). Special attention was given to the frequency range of temperature fluctuations above frequency of melt overflight, aiming on on-line monitoring applications. It is shown that local fluctuations of T are related to local melt’s surface deformations due to unequal radiation absorption; thus the noise spectrum of T fluctuations reflects turbulent surface deformation, caused by gas jet and capillary waves. It is also shown that the thermo-capillary effect with capillary-wave turbulence generation can be observed in case of exposure to 10.6 μm radiation with a laser intensity of about 1 MW/cm2. The power law of “−7/6” describes the spectrum of the T fluctuation variance in this case of anomalous absorption of radiation, and the standard deviation of T is in excess of 10 K for a frequency of 14 kHz. There is no such effect in case of fiber-laser radiation applying, and the source of the capillary waves is only forced low-frequency deformations of the melt surface. The standard deviation of T does not exceed 3 K on the frequency of 14 kHz, and above, and a power law of the spectrum fluctuation is described by about “−3” in that range.

Abstract: A new setup has been implemented at LCM-LNE-CNAM for the determination “of the spectral responsivity of radiation thermometers for the determination” of the thermodynamic temperature of high-temperature blackbodies at the temperature of a metal–carbon eutectic phase transition. In this new setup, an innovative acoustic-optic modulator feedback loop is used to stabilize the radiance of a wavelength tunable laser. The effect of residual optical interferences on the calibration of a test pyrometer is analyzed. The full uncertainty budget is presented.

Abstract: A series of area temperature maps were obtained from the upper surface of a moving thermomechanical controlled processed (TMCP) microalloyed steel skelp following laminar cooling using an infrared video camera. In addition, an emissivity probe was used to obtain both the emissivity and temperature at the mid‐face of the moving skelp. Properly sampled infrared camera temperature measurements correlated well with both the measured probe temperature and with the process control pyrometer. A finite element thermal model of the system, in conjunction with the transverse skelp temperature profiles obtained from the infrared camera, was used to quantify the size and shape of the laminar cooling water jet’s direct impact zone on the skelp. The region experiencing direct water impact was found to be constrained by the residual water present on the moving skelp.

Abstract: The pursuit for improved engine efficiency is driving the demand for accurate temperature measurement inside turbine engines. Accurate measurement can allow engines to be operated closer to their design limits to improve thermal efficiency. It can enable engineers to verify mechanical integrity, provide better prediction of component life, validate CFD and other design tools and aid the development for leaner more efficient engines. Unfortunately, experimentally measuring surface temperatures under harsh rotating conditions is challenging. This EngD study conducted by Ashiq Hussain Khalid at the University of Manchester and Rolls-Royce plc, reviews the rationale of using phosphor thermometry over existing methods, including thermocouples, pyrometry and thermal paints/melts, which lack detail, accuracy, or are too expensive for continuous testing. Although phosphor thermometry exhibits desirable characteristics, the high temperature and fast rotating engine environment presents some challenges that would need to be addressed before a successful measurement system can be implemented. Examples of such issues include: rising blackbody radiation, restricted optical access, fibre optic constraints and limited time period to collect data. These factors will impose measurement limits and greatly influence the design philosophy of the system, including phosphor choice, phosphor lifetime characteristics, bonding technique, excitation/detection methodologies and probe design. Taking these into consideration, the research focuses on the development of phosphor thermometry systems for use in development gas turbine engines, with measurement solutions for specific engine components. The high pressure turbine blade was given research priority.A number of phosphors including YAG:Tb, YAG:Tm. Y2O3:Eu and Mg3F2GeO4:Mn were investigated and characterised in terms of intensity and lifetime decay, with increasing temperature up to 1500oC. Spectral analysis and absolute intensity measurements established emission peaks and permitted comparative quantitative analysis to optimise system setup. The intensity of phosphor emission relative to Planck?s blackbody radiation was also performed. YAG:Tm under 355nm illumination was found to exhibit the highest emission intensity at high temperatures, and because its spectral emission peak at 458nm was the lowest, its advantage in terms of blackbody radiation was further amplified. For rotating components, an upper temperature limit is reached based on the emission intensity at rising blackbody radiation levels and the system?s ability to detect fast decays. A lower limit is reached based on the quenching temperature, probe design and rotational velocity. There are different methods to correct the distorted decay waveform as it traverses through the acceptance cone of the fibre. A phosphor selection criterion, taking into consideration these limitations, was successfully applied for various rotating engine components. The optical layout was setup and tested on stationary and rotating cases under laboratory conditions using similar design constraints, including fibre choice, maximum permissible lens size and target distances. A series of tests validated design methodologies and assumptions to enable testing on full scale rotating engine components.Mg3F2GeO4:Mn, using 355nm illumination, was found to be the most suitable phosphor for the HP drive cone. The estimated performance under the expected rotational speeds was found to be 624-812oC with a standard uncertainty of �0.99%. YAG:Tm, illuminated with 355nm, was found to be the most promising phosphor for high pressure turbine blade measurements. The performance under the expected rotational speeds was found to be 1117?1375oC with a standard uncertainty of �0.97%. This is better than other competing technologies that are currently available for temperature measurement of rotating turbine blades.

Abstract: We present novel time- and angle-resolved x-ray diffraction (TARXD) capable of probing structural and chemical evolutions during rapidly propagating exothermic intermetallic reactions between Ni-Al multilayers. The system utilizes monochromatic synchrotron x-rays and a two-dimensional (2D) pixel array x-ray detector in combination of a fast-rotating diffraction beam chopper, providing a time (in azimuth) and angle (in distance) resolved x-ray diffraction image continuously recorded at a time resolution of ∼30 μs over a time period of 3 ms. Multiple frames of the TARXD images can also be obtained with time resolutions between 30 and 300 μs over three to several hundreds of milliseconds. The present method is coupled with a high-speed camera and a six-channel optical pyrometer to determine the reaction characteristics including the propagation speed of 7.6 m/s, adiabatic heating rate of 4.0 × 106 K/s, and conductive cooling rate of 4.5 × 104 K/s. These time-dependent structural and temperature data provide ...

Abstract: Two high-temperature blackbodies were developed and tested. The first one is a graphite blackbody with a maximum temperature of 2000 °C, an opening of 40 mm, and an emissivity of 0.995. It is intended for the routine calibration of pyrometers. The second one is a small version of a pyrolytic graphite (PG) blackbody with a cavity diameter of 15 mm, an opening of 10 mm, and an emissivity of 0.9996. The blackbody has two options with maximum temperatures of 2500 °C and 3000 °C, respectively. With these, the list of high-temperature blackbodies developed at VNIIOFI consists of five PG types and one graphite type, which can be used in radiation thermometry as precision Planckian sources or furnaces for fixed-point applications. The article also describes modifications to the PG furnace, where PG heater rings are replaced partly or totally by graphite elements. Such modifications extend the lifetime of the heater, reduce the cost for some applications and, for some cases, improve the temperature uniformity.