Pyrometric Method Research Articles

THE POSSIBILITY OF APPLICATION OF PYROMETRIC METHOD IN INDUSTRIAL DOSIMETRY OF ELECTRON BEAM RADIATION

Validation of process of medical product sterilization includes absorbed dose mapping in a phantom made of material representative of the object to be processed. Commonly, such measurements are carried out using the disposable chemical dosimeters placed in the phantom at the nodes of the 3D grid. Such a procedure is very laborious and costly in terms of the consumption of dosimeters. In the work, we investigated the possibility of using pyrometric method for prompt mapping of the absorbed dose. The studies were carried out using a rectangular phantom in the form of a set of expanded polystyrene plates, which is exposed to a scanned electron beam. The temperature and absorbed dose distributions in the phantom were measured. A linear dependence between them has been established. The calculation of the absorbed dose profile was also performed by MC simulations. Satisfactory agreement of the calculated dose distribution with the measured one is shown. The limitations of applicability of the proposed method are determined.

Development of a Non-contact Skin Temperature Measurement System for Newborns Based on Intelligent Analysis of Thermometric Data

Measurement of body temperature is a vital parameter when monitoring newborns. The peculiarity of thermometry of newborns involves certain anatomical features of children, which make them vulnerable to changes in environmental temperature. These features include: the reduced amount of subcutaneous fat, thin epidermis, blood vessels located near the surface of the skin. This paper demonstrates the choice of the method of converting the original biometric data into the thermal map, as well as the analysis of the obtained experimental thermal imaging data of using the pyrometric method of scanning the incubator bed for newborns.

METHOD AND MEANS FOR MEASURING THE TEMPERATURE OF THE POLE WINDINGS OF THE ELECTRIC MACHINE ROTOR

The temperature of the pole windings is one of the main informative parameters, the deviation of which may indicate the presence of a number of common defects of electrical machines. However, the implementation of high-precision means for measuring the temperature of the pole windings of the electric machine rotor is associated with a number of technical difficulties. The aim is to increase the accuracy of measuring the temperature of the pole windings of the rotor of an electric machine by developing a contactless method and means of measuring the temperature of the pole windings of the rotor in real time. The paper shows that the existing most common methods of temperature measurement have significant disadvantages that limit the possibility of their use for the implementation of means of measuring the pole windings of the rotor of an electric machine. A bispectral pyrometric method of temperature measurement is proposed, which provides simultaneous conversion into voltage of functionally temperature-dependent spectral densities of radiation for two spectrally close electromagnetic waves with subsequent finding of their ratio, which allowed to remove the most significant components of methodical measurement characteristic of classical pyrometers. The design of the bispectral pyrometric measuring system of temperature of pole windings of a rotor of rotating electric machines realized on the basis of the offered method of measurement, suitable for work in a real-time mode together with systems of control of a technical condition and diagnostics is developed.

Simulation of silicon wafers heating during rapid thermal processing using “UBTO 1801” unit

The present work is devoted to determination of the dependence of the heating temperature of the silicon wafer on the lamps power and the heating time during rapid thermal processing using “UBTO 1801” unit by irradiating the wafer backside with an incoherent flow of constant density light. As a result, a mathematical model of silicon wafer temperature variation was developed on the basis of the equation of nonstationary thermal conductivity and known temperature dependencies of the thermophysical properties of silicon and the emissivity of aluminum and silver applied to the planar surface of the silicon wafer. For experimental determination of the numerical parameters of the mathematical model, silicon wafers were heated with light single pulse of constant power to the temperature of one of three phase transitions such as aluminum-silicon eutectic formation, aluminum melting and silver melting. The time of phase transition formation on the wafer surface during rapid thermal processing was fixed by pyrometric method. In accordance with the developed mathematical model, we determined the conversion coefficient of the lamps electric power to the light flux power density with the numerical value of 5.16∙10-3 cm-2 . Increasing the lamps power from 690 to 2740 W leads to an increase in the silicon wafer temperature during rapid thermal processing from 550°to 930°K, respectively. With that, the wafer temperature prediction error in compliance with developed mathematical model makes less than 2.3 %. The work results can be used when developing new procedures of rapid thermal processing for silicon wafers.

Dependence of diameter on flow velocity of liquid metal jet for repeatable pulse powered plasma sources

To realize a pulsed-power discharge plasma using a liquid metal, we investigated the dependence of the diameter on the flow velocity of a liquid metal flow consisting of a U-alloy. The plasma temperature was measured using a pyrometric method. The results show that the flow velocity estimated by the parabolic corresponds to a theoretical value derived from the difference between the gas pressure and atmospheric pressure. The diameter of the liquid metal flow was found to be 0.5 to 0.9 times smaller than the nozzle diameter. We have also demonstrated pulsed-power discharge using this liquid metal load by observing optical emission from plasma. The results indicated that a low-temperature plasma was generated by the proposed method.

Refinement of the two-color pyrometry method for application in a direct injection diesel and natural gas compression-ignition engine

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.

Assessment of Double Modulation Pyrometry as a diagnostic tool for use in concentrated solar facilities

Double modulation pyrometry (DMP) is a pyrometric method developed to enable radiometric temperature measurements in solar simulators, where solar blind pyrometry cannot be applied due to the continuous spectrum of the artificial light source. Sofar, DMP has been characterized in two solar simulator facilities, but no direct comparison to a reference pyrometer has been performed until now due to the limitations of applying pyrometry in solar simulators. Here, a series of experiments is reported that were conducted in concentrated natural sunlight where reference pyrometers are available. They demonstrate the performance enhancement gained by utilizing the inherent advantages of DMP, i.e. the in-situ reflectance measurement and the freedom to select the operation wavelength.

Detonation temperature of an emulsion explosive with a polymer sensitizer

Dependences of the brightness temperatures of the detonation front and detonation products on detonation pressure were determined in the range of 0.7–9.4 GPa by a pyrometric method. The pressure was varied by changing the initial density of the emulsion explosive in the range of 0.43–1.2 g/cm3. Polymer microballoons were used as sensitizer. The dependence of the brightness temperature in the Chapman–Jouguet plane on detonation pressure was found to be nonmonotonic. In the investigated pressure range, the measured temperature values varied from 2250 to 1830 K. A comparative analysis of the application of polymer and glass microballoons as sensitizers was performed. The obtained experimental data were compared with the calculation results available in the literature.

3-D Reconstruction Algorithm of Flame Based on Inversion Calculation of Thermal Radiation

This paper presents the design, method, and evaluation of a 3-D field reconstruction of a combustion flame. Three images under three different wavelengths were captured together using charge-coupled device cameras, which were specially processed by filters. Three sets of data about the value of radiation under different wavelengths were transformed from the images that were obtained according to the law of thermal radiation and derivation. For a pixel point in flame image, its irradiance can be expressed as the accumulation of the emissive power from luminous flame with different temperatures along the rays through the pixel. Then, through the calculation of the thermal radiation inversion based on the data from pixels in images, the 3-D temperature field of the flame is obtained and displayed. Experimental tests were done using candle flame to evaluate the effectiveness of the system. Ultimately, this method can restore the temperature distribution of the flame temperature field effectively. Compared with other methods, such as the two-color pyrometric method, the device of this method can get synchronous monochromatic images under three different wavelengths, the beams of which were through a beam splitter at the same time to avoid the errors of spatiotemporal matching. Else, we can reproduce the validity and efficiency of temperature field using the reconstruction algorithm that is built on improved simulated annealing algorithm.

3-D Reconstruction of Flame Temperature Distribution Using Tomographic and Two-Color Pyrometric Techniques

Two-color pyrometric methods have been widely used in noncontact temperature measurement area. However, it is difficult to get synchronous monochromatic images for two-color pyrometric formula. Some researches use beam splitter to obtain two or more optical paths to capture the different monochromatic images, but the complex optical paths will bring spatiotemporal matching errors. Another method uses color camera to capture the Red, Green, Blue (RGB) channel images as the RGB monochromatic images, but substituting the Dirac delta function for spectral response function will result in the inaccuracy of the measurement results. In fact, the RGB monochromatic images can be obtained from the color image if the irradiance attenuations from color channel to single wavelength are calibrated. In this paper, a novel 3-D reconstruction method is proposed to measure the temperature distribution of combustion flame. First, the irradiance attenuations are calibrated to calculate the synchronous monochromatic images at $R$ and $G$ wavelengths. Second, the tomographic reconstruction of flame monochromatic emissive power is improved with visual hull restriction so that the energy distribution is more reasonable. Finally, the 3-D temperature distribution is calculated from the reconstructed monochromatic emissive power fields at $R$ and $G$ wavelengths using two-color pyrometric method. The alcohol and butane flames are tested in the laboratory-scale test rig. The experimental results indicate that our approach performs well in flame temperature field reconstruction.

Determination of the Integral Emissivity of a Periclase-Carbon Lining

Experimental values have been determined for the integral emissivity (blackness) of periclase-carbon refractories used in the working layer of the lining of steel-pouring ladles. The values were found for the range 500–900°C. It was established that the emissivity of periclase-carbon refractories is considerably higher than that of periclase refractories. Use of the data which were obtained is making it possible to more accurately measure the temperature of such linings by the pyrometric method.

Detonation parameters of pressed charges of benzotrifuroxane

The brightness temperature and pressure profiles of the detonation products of pressed charges of benzotrifuroxane were determined by a pyrometric method, and the heat of explosion and propellant performance were experimentally determined. The temperature of the detonation products (4100±150 K) was significantly lower than the calculated values reported in most theoretical papers. Compared to HMX, benzotrifuroxane has a higher heat of explosion but lower expansion velocity of the shell (T-20) method and Gurney energy.

Measurement of Temperature Distribution on Mineral Surface During Argon-Argon Laser Step Heating Dating

New pyrometric method of temperature distribution measurement on surface of natural mineral during laser 40Ar/39Ar dating has been devised. Peculiarity of this method is that it is relatively simple and does not require in availability of information about under test object absorption ability. It is very important during measurement of temperature distribution on surface of natural mineral. Proposed method includes forming of two digital pictures of sample in one frequency only, using of proposed method in conventional laser complexes intended for 40Ar/39Ar dating does not require large additional technical expense. Special program on the basis of platform Framework 4.0 has been devised for data processing automatization. Temperature field in several geological samples has been researched using method proposed. Data obtained indicates that temperature distribution in some of the samples during laser stepwise dating is sufficiently heterogeneous. Nonuniformity of temperature distribution can result in appearance do not taking into account inaccuracy in age value, that larger of analytical inaccuracy in few time. Thus, data obtained indicates that control of temperature distribution homogeneity during laser 40Ar/39Ar stepwise dating is necessary condition of accuracy dating result

Measurement of the brightness temperature of shock-compressed epoxy resin

The brightness temperature of shock-compressed EC141 NF epoxy resin was measured by a pyrometric method in the pressure range of 19–42 GPa. The experimental points are in good agreement within the error with the calculation performed in the work. From the results of experiments, it follows that the presumed phase-transition region is not apparent in the pressure—temperature plane. Particle velocity records at the epoxy-water interface suggest the absence of a chemical reaction in EC141 NF epoxy compound at a pressure of 22.5 GPa during the observation time.

Measuring temperatures in a high concentration solar simulator – Demonstration of the principle

A new single color pyrometric method for samples heated radiatively via an artificial light source is presented. The method allows separation of the external radiation reflected by a sample from its thermal emission as the intensity of arc lamps, commonly used in high concentration solar simulators, can be electrically modulated at frequencies well above the thermal response (ω≫1/τth) of the sample. Thus, the external radiation reflected off the sample can be measured separately using a phase sensitive detection scheme at the modulation frequency of the light source. In addition, a composite signal consisting of the thermal emission with the reflected external radiation superimposed is detected. This signal is obtained by observing the sample with a mechanical chopper operating at a different frequency placed in the observation path. The composite signal is measured simultaneously with identical optics and detector. The thermal emission of the sample can then be extracted as the difference of the two measured signals after suitable calibration. The working principle of the method and its calibration is explained and the performance of the method is demonstrated using its implementation on a lab scale.

In situ observations of solidification processes in γ-TiAl alloys by synchrotron radiation

In situ observations of phase transformations involving melts are performed using energy-dispersive diffraction of synchrotron X-rays on electromagnetically levitated γ-TiAl alloys containing Nb. The determined primary solidification modes, confirmed by microstructure analysis, delivered new reliable data about the boundary of the α(Ti) solidification domain, which differs in the various Ti–Al–Nb phase diagram descriptions. These data have been used for a reassessment of the thermodynamic database of the ternary Ti–Al–Nb system. The new description realistically reflects the experimental findings. Liquidus and solidus temperatures determined by the pyrometric method agree fairly well with the calculated values. Direct experimental information on the nature of the reactions along the univariant lines is provided.

Pyrometric Method of Temperature Measurement with Compensation for Solar Radiation

Pyrometric Method of Temperature Measurement with Compensation for Solar RadiationOutdoor remote temperature measurements in the infrared range can be very inaccurate because of the influence of solar radiation reflected from a measured object. In case of strong directional reflection towards a measuring device, the error rate can easily reach hundreds per cent as the reflected signal adds to the thermal emission of an object. As a result, the measured temperature is much higher than the real one. Error rate depends mainly on the emissivity of an object and intensity of solar radiation. The position of the measuring device with reference to an object and the Sun is also important. The method of compensation of such undesirable influence of solar radiation will be presented. It is based on simultaneous measurements in two different spectral bands, shor-twavelength and long-wavelength ones. The temperature of an object is derived from long-wavelength data only, whereas the short-wavelength band, the corrective one, is used to estimate the solar radiation level. Both bands were selected to achieve proportional changes of the output signal due to solar radiation. Knowing the relation between emissivity and solar radiation levels in both spectral bands, it is possible to reduce the measurement error several times.

Influence of heat distribution and zone shape in the floating zone growth of selected oxide compounds

The effects of heat distribution, process parameters, and the ambient atmosphere on the characteristics of the molten zone are considered for floating zone (FZ) crystal growth of selected oxide compounds with special reference to cuprates. The outer shape of the FZ, which is stabilized only by capillary forces, and the interfaces between melt and growing crystal are decisive for process stability and crystal perfection. They do not only depend on external parameters such as zone heights, growth velocity, and rotation mode but are closely related to the phase diagram and the constitution of the individual substance. Therefore, the choice of the optimum process conditions is a subtle balance of parameters like appropriate focusing or defocusing of the light, the direction of growth and the ambient atmosphere, which are adapted to the individual substance. A pyrometric method of FZ temperature measurement was developed as an appropriate tool for process control.

1 kW imaging furnace with in situ measurement of surface temperature

This article describes the development and characterization of a 1kW imaging furnace that allows to investigate materials such as sulfides at ultrahigh temperatures under controlled atmosphere. Peak flux densities up to (15.37±0.66)×106Wm−2 corresponding to a maximum stagnation temperature of 3090K can be reached in the center of the heating zone of 3mm diameter (full width at half height). Individual sample holders can be mounted on a generic sample stage that is aligned in three axes. Together they define an experiment. Experiments can thus be easily interchanged without requiring any realignment. The use of a specific sample holder is reported where the sample rests on a water-cooled tip to avoid contamination by crucible material and where a protective glass dome can be mounted to allow the study of samples releasing condensable or corrosive gases. With the dome in place the peak flux density decreases to a value of (13.59±0.45)×106Wm−2 (Tstag=2980K). The surface temperature of the sample and the average irradiance can be measured simultaneously by the pyrometric method flash assisted multiwavelength pyrometry. The irradiance on the sample and, thus, the temperature reached can be controlled by adjusting the position of the sample. This is effected by a computer controlled fork lift with a resolution of 0.05mm.

Effects of Pressure and Oxygen Concentration on the Combustion of Different Coals

A pyrometric method was used for simultaneous in situ measurement of the temperature and size of individual coal particles in a pressurized entrained flow reactor. Several series of measurements we...