Comparison between visible and near-IR flame spectra from natural gas-fired furnace for blackbody temperature measurements

This paper reports the results from investigating the feasibility of calculating flame temperature from a natural gas-fired furnace based on blackbody radiation in the visible spectral range. If successful, the visible spectral range would provide data for multi-task applications such as emission line analysis and temperature calculation simultaneously. A probe containing a lens connected to the fiber-optic cables is inserted into the furnace and pointed towards the flame. Spectral intensity data are fed back to a spectrometer and then to a monitoring computer. The approach is first applied to various furnace types using the visible range to establish a baseline for the technique. The results for temperature calculations in the visible range are then compared with those taken in the near-IR (NIR) range under the same conditions. This comparison indicates that temperatures calculated from visible region could be as accurate as the one obtained from NIR region. Challenges associated with this technique are also discussed.     

Simultaneous temperature and concentration measurements in hydrogen-air flames using a cars spectrometer

A relatively simple CARS spectrometer has been designed taking advantage of the pure rotational spectra of hydrogen. The spectrometer was used for simultaneous measurement of instantaneous temperatures and concentrations of fuel in hydrogen jets and flames with a high spatial resolution. Data on the fluctuation structure of the flow are reported. Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 5, pp. 34–37, September–October, 1993.     

Time averaged temperature calculations in pulse electrochemical machining, spectral approach

Simulation of the temperature distribution during the Pulse Electrochemical Machining (PECM) process provides information on system design and guidelines for practical use. The pulses that are applied to the PECM system have to be described on a time scale that can be orders of magnitude smaller than the time scale on which the thermal effects evolve. If the full detail of the applied pulses has to be taken into account, the time accurate calculation of the temperature distribution in PECM can become a computationally very expensive procedure. A different approach is used by time averaging the heat sources of the system. Performing this, the time steps used during the calculations are no longer dictated by the pulse characteristics. Using this approach, computationally very cheap, yet satisfying results can be obtained. In previous work of the authors, the hybrid calculation and the Quasi Steady State ShortCut (QSSSC) were introduced. This method allows to perform simplified calculations while getting satisfactory results. The method introduces errors however, which were quantified using analytical solutions and found to be acceptable. The results applied only to rectangular pulses. In this work, the more general case of arbitrary pulse forms is considered using a spectral approach.     

The calibration of NIR reflectance spectrometer for the determination of diverse compositional parameters

Near Infrared Reflectance Spectroscopy (NIRS) has been used to analyze a variety of agricultural commodities. Many times the success or lack of it has been due to inadequate computational capabilities or asking more of the instrument than its capabilities. This study showed that for the development of multiple analytical methods by Near Infrared Reflectance Spectroscopy (NIRS) a sophisticated instrument computer software system can perform multiple analyses and that different data treatments were required for each constituent. In this case a scanning monochromator with a digital mini computer and the USDA/Pennsylvania State University software system could easily be calibrated to determine simultaneously the percentages of moisture, protein and residual oil in cottonseed meal. High RSQ (.98–.99 for all constituents) and low standard errors of prediction (SEP) (0.18 moisture, 0.1 oil and 0.34 protein) were obtained. Success was due to the acquisition of sufficient data for all three analyses (via the monochromator) and the use of sufficient computing power to obtain an optimized calibration where each constituent required a different mathematical data treatment.     

Continuous spatial tuning of laser emissions in a full visible spectral range

In order to achieve a continuous tuning of laser emission, the authors designed and fabricated three types of cholesteric liquid crystal cells with pitch gradient, a wedge cell with positive slope, a wedge cell with negative slope, and a parallel cell. The length of the cholesteric liquid crystal pitch could be elongated up to 10 nm, allowing the lasing behavior of continuous or discontinuous spatial tuning determined by the boundary conditions of the cholesteric liquid crystal cell. In the wedge cell with positive slope, the authors demonstrated a continuous spatial laser tuning in the near full visible spectral range, with a tuning resolution less than 1 nm by pumping with only a single 355 nm laser beam. This continuous tuning behavior is due to the fact that the concentration of pitch gradient matches the fixed helical pitch determined by the cell thickness. This characteristic continuous spatial laser tuning could be confirmed again by pumping with a 532 nm laser beam, over 90 nm in the visible spectral range. The scheme of the spatial laser tuning in the wedge cell bearing a pitch gradient enabled a route to designing small-sized optical devices that allow for a wide tunability of single-mode laser emissions.     

Influence of the composition and temperature of heat treatment of porous glasses on their structure and light transmission in the visible spectral range

The pore structure and light transmission of high-silica porous glasses in the visible spectral range have been investigated as a function of the heat treatment temperature and the composition of the initial two-phase alkali borosilicate glass. The character of light transmission in porous glasses has been analyzed in the framework of the concepts of structural features of their pore space and the processes occurring in the porous glass during heating. It has been demonstrated that an increase in the temperature of heat treatment of porous glasses with different compositions leads to an increase in the pore size and a decrease in their specific surface area (with a nearly constant total porosity), which is associated with the processes of overcondensation of pores due to the rearrangement and the change in the packing density of secondary silica particles. It has been revealed that the introduction of phosphate and fluoride ions into the initial sodium borosilicate glass results in an increase in the light extinction coefficient of porous glasses due to the increase in the sizes of phase-separated inhomogeneity regions in the initial two-phase glasses, the formation of larger pores, and the presence of nanosized microcrystalline phases in porous glasses.     

Area Rules for the diffusion flame of a moving Bunsen burner corresponding to different temperature ranges

A high-speed camera system is used to observe the diffusion flame of a Bunsen burner in linear motion. The resultant sequence of instantaneous motion pictures of the flame accelerating at 3.60 m/s² is processed and used to study the change in the flame area and specific floor area of the flame over different temperature ranges. The results indicate that the total flame area increases in the fuel control zone as the velocity increases over the range of experimental speeds employed (<0.90 m/s); then the total area quickly decreases in the transition region and is stable in the cross-flow wind control zone. As the velocity of the fire source increases, the low-temperature and specific floor areas adopt more dominant positions in the low-speed fuel control zone. In the high-speed cross-flow wind control zone, the area of the high-temperature zone and specific floor area take the dominant positions. The transformation between the two situations occurs in the transition zone. The cross-flow wind increases the high-temperature specific floor area of the fire compared to that of a stationary fire; the consumption in the moving fire also becomes correspondingly more concentrated and fierce.     

关于超长型温度传感器校准用标准恒温槽研制的探讨

本文主要提出研制一种可校准超长型温度传感器的标准恒温槽的设计要求及设计思路,以供研究探讨,希望解决现实存在的超长型温度传感器因传感器太长而浸没深度不足的校准问题。     

Electrical characterizations of PZT ceramics in large frequency and temperature ranges

Electrical properties of PbZr_0.75Ti_0.25O₃ ceramics have been characterized. The measurements have been made in frequency ranging from 20 to 2.10⁹ Hz and between 20 and 730 °C for low and medium frequencies. Typically at room temperature, the dielectric constant ′ is higher than 500 at 1 MHz whereas the loss tangent is close to 0.01. From ′(T) measurements, the Curie temperature of our sample has been determined at 320 °C. In the paraelectric state, ′(T) follows the empirical Curie–Weiss law near the phase transition which is of second order type. The increase of ′ observed at high temperatures and low frequencies in the paraelectric state are explained: this abnormal behavior is due to the migation of oxygen ions towards the electrodes, creating an additional non-ferroelectric interface which generates a Maxwell–Wagner effect.     

GPC calibration for polymers of unknown composition and structure using a real-time computer

A computer technique ultimately yielding, from GPC data, both differential and integral molecular weight distributions of macromolecular products with unknown composition and structure has been worked out, based on a “universal” calibration method previously proposed by other authors to calculate average molecular weights. The technique involves as sole assumption the validity of the “universal” calibration for the kind of sample under investigation. The GPC output data are handled through a realtime computer program and punched on paper tape. Together with two experimental parameters of the polymer (average molecular weights, limiting flow number) and the “universal” calibration of the columns set, the tape is used as input for the off-line programming. Examples are presented, showing the accuracy which can be expected.     

A dynamic FT-IR method for determining the curing temperature ranges of an acetylene-terminated polyisoimide prepolymer

A dynamic FT-IR method was used to determine the individual curing temperature ranges of the isoimide-imide isomerization and crosslinking reactions of an acetylene-terminated polyisoimide prepolymer. The individual curing temperature ranges of these two types of chemical reactions for the polyisoimide system using differential scanning calorimetry (DSC) were totally overlapped. Using dynamic FT-IR spectroscopy, the curing temperature ranges of the isomerization and crosslinking reactions were clearly separated. The isomerization reaction began at lower temperatures than the crosslinking reaction and was complete when only half of the crosslinking reaction had occurred. The temperature width, ΔT_1/2, was twice as great for the crosslinking reaction compared with the isomerization reaction. Activation energies from dynamic FT-IR spectroscopy can be obtained for the two separate reactions, however, for the reactions considered here, the activation energies were similar, 26 kcal/mol for the isomerization reaction and 23 kcal/mol for the crosslinking reaction. © 1996 John Wiley & Sons, Inc.     

Process simulation using the expanded fluid model for viscosity calculations

The expanded fluid (EF) viscosity model was implemented and further developed for efficient integration into a commercial process simulator (VMGSim™). The model has three adjustable parameters per component and its inputs are density, pressure and low pressure gas viscosity. The model was adapted to use densities determined by the Rackett correlation (liquid phase) and the Advanced Peng–Robinson Equation of State (vapor phase). The enhanced EF model fit experimental viscosities of pure hydrocarbons, water and polar compounds important for the simulation of oil and natural gas systems with average absolute errors just above 5%. The implemented EF model was tested against experimental viscosity data that included hydrocarbon and aqueous mixtures with average absolutes errors of 0.7 and 6.2% respectively. Generalized expressions for the estimation interaction parameters of binary mixtures involving paraffins, naphthenes, aromatics, alcohols, glycols and water were obtained. The EF model was also applied to crude oil (bitumen) examples. The three key developments for the efficient implementation of the EF model in a commercial simulator were: (1) the appropriate selection of phase density models; (2) the automatic determination of model fluid specific parameters; and (3) the use of generalized mixing rules for the calculation of binary interaction parameters.     

跨温区直接蒸发冷却的热质传递特性

低温干燥空气直接蒸发冷却用于制备低温冷水甚至冰晶时会跨越常温和低温两个温度区间,其传热传质特性会随温度区间而发生变化。进行了常温工况和非常温工况下氧化铝(Al₂O₃)泡沫陶瓷填料的逆流直接蒸发冷却实验,重点对0~15℃的非常温区间进行研究,对非常温区间的传热驱动力与蒸发冷却效率、传质驱动力与空气含湿量增量、焓差驱动力与焓效率之间的关系进行了定量的计算分析,并对比了常温与非常温工况下的直接蒸发冷却过程。在此基础上,利用分析方法对非常温工况下的能量利用价值进行了计算,并对其性能的提升和应用潜力进行了分析。     

Low temperature synthesis of ZnIn2S4 microspheres as a visible light photocatalyst for selective oxidation

ZnIn₂S₄ microspheres have been synthesized by a facile hydrothermal method at 80 °C. The characterization results show that the as-synthesized sample is hexagonal phase ZnIn₂S₄ microspheres. The results of elemental mapping and thermogravimetric confirm that the sample is the pure ZnIn₂S₄. The ZnIn₂S₄ sample has been first used as visible-light-driven photocatalyst for selective oxidation of benzyl alcohol to benzaldehyde under ambient conditions, which shows the conversion is ca. 69% along with the high selectivity, ca. 94%, after 3 h irradiation. XRD and XPS investigations suggest that ZnIn₂S₄ is relatively stable in the photocatalytic reaction.     

Properties of the Stöber centrifugal aerosol spectrometer at a high sampling flow rate: calibration, resolving power and correction factors for particle losses

A centrifugal aerosol spectrometer designed by Stöber and Flachsbart (1969) was calibrated at a high sampling flow rate (1.91. min⁻¹) for the particle size range 0.2–5 μm and the resolving power was determined. Multiplication factors to correct for particle losses in the aerosol inlet, in the edge layers of the foil and through the exhaust of the spiral duct were determined.     

Simple and accurate correlations for diffusion coefficients of solutes in liquids and supercritical fluids over wide ranges of temperature and density

The binary diffusion coefficients at infinite dilution, D₁₂, are fundamental properties in chemical engineering simulation and design. In this work, very simple and accurate expressions involving two parameters are proposed/analyzed for their estimation. They depend only on temperature and/or solvent density and/or solvent viscosity. Their correlation and prediction abilities are tested with the largest database ever compiled, composed of 539 binary systems and 8219 data points, where polar/non-polar, symmetrical/asymmetrical, small/large, and light/heavy molecules are included without exception. It is shown that only two experimental D₁₂ values are sufficient to get good parameters for the subsequent estimation of reliable diffusivities far away from the conditions of the experimental data utilized to fit them. Globally, Eqs. (2), (3), (4), (9) are recommended for D₁₂ calculation, due to the excellent results achieved for both correlation (average errors between 2.78% and 3.05%) and prediction (average errors between 4.21% and 4.44%). A comparison with models from the literature is also accomplished.     

Phase equilibria calculations for ill-defined mixtures using the prsv equation of state

A method for the calculation of vapor-liquid equilibria (VLE) for multicomponent systems using continuous thermodynamics is presented. The Extended Spline Fit Technique (ESFT) is used to represent the molar distribution curve of petroleum fluids. A continuous version of the Peng-Robinson-Stryjek-Vera (PRSV) equation of state (EOS) with Generalized Single Carbon Number Properties (GSCNP) is utilized. For continuously distributed components, following the suggestion of Hendriks (1987), the number of equations solved is reduced through integration over the range of the distributing variable using Legendre-Gauss quadrature. Integrated equations are solved using accelerated successive substitution. Flash, dew and bubble point calculations for an imaginary and a real system yield satisfactory results.