Determination Of Gas Temperature Research Articles

Temperature measurement using frequency comb absorption spectroscopy of CO2.

Absorption spectroscopy on CO2 for the determination of gas temperature is reported. Direct absorption of a frequency comb laser through a gas cell at atmospheric conditions is analysed with a virtually imaged phased array spectrometer. Several measurement and analysis techniques are investigated to find the parameters most sensitive to changes in the temperature. Some of these show qualitative agreement with theoretical predictions where the trend is similar to the calculated values.

Gas temperature determination in an argon non-thermal plasma at atmospheric pressure from broadenings of atomic emission lines

In this work a new spectroscopic method, allowing gas temperature determination in argon non-thermal plasmas sustained at atmospheric pressure, is presented. The method is based on the measurements of selected pairs of argon atomic lines (Ar I 603.2nm/Ar I 549.6nm, Ar I 603.2nm/Ar I 522.1nm, Ar I 549.6nm/Ar I 522.1nm). For gas temperature determination using the proposed method, there is no need of knowing the electron density, neither making assumptions on the degree of thermodynamic equilibrium existing in the plasma.The values of the temperatures obtained using this method, have been compared with the rotational temperatures derived from the OH ro-vibrational bands, using both, the well-known Boltzmann-plot technique and the best fitting to simulated ro-vibrational bands. A very good agreement has been found.

CO(B 1Σ+→A 1Π) Angstrom System for Gas Temperature Measurements in CO2 Containing Plasmas

CO2 containing plasmas are of growing interest for greenhouse gas remediation and dry gas reforming. In this paper, we show that the optical emission spectrum of CO(B-A) transition can be used for gas temperature determination in CO2 containing plasmas. The study was performed in a packed-bed reactor and compared with previously published results for a MW discharge. The CO emission is mainly produced by direct electron excitation from ground state CO. The rotational temperature is determined by a fitting algorithm of the CO(B-A) (0-1) spectrum and the accuracy of the deduced rotational temperature is shown to be better than 30 K. Meanwhile, we also compared the results with the widely used Boltzmann plots of the CO(B-A) (0-1). The rotational lines corresponding to Q(18–24) yield accurately the gas temperature for spectra with a resolution in excess of 0.05 nm FWHM. Rotational lines with N < 18 cannot be used due to the overlap of rotational lines from different branches unless a spectral resolution of at least 5 pm is used.

2D numerical modelling of gas temperature in a nanosecond pulsed longitudinal He-SrBr2 discharge excited in a high temperature gas-discharge tube for the high-power strontium laser

An active volume scaling in bore and length of a Sr atom laser excited in a nanosecond pulse longitudinal He-SrBr2 discharge is carried out. Considering axial symmetry and uniform power input, a 2D model (r, z) is developed by numerical methods for determination of gas temperature in a new large-volume high-temperature discharge tube with additional incompact ZrO2 insulation in the discharge free zone, in order to find out the optimal thermal mode for achievement of maximal output laser parameters. A 2D model (r, z) of gas temperature is developed by numerical methods for axial symmetry and uniform power input. The model determines gas temperature of nanosecond pulsed longitudinal discharge in helium with small additives of strontium and bromine.

Calculation of gas temperature at the outlet of the combustion chamber and in the air-gas channel of a gas-turbine unit by data of acceptance tests in accordance with ISO

This article describes a high accuracy method enabling performance of the calculation of real values of the initial temperature of a gas turbine unit (GTU), i.e., the gas temperature at the outlet of the combustion chamber, in a situation where manufacturers do not disclose this information. The features of the definition of the initial temperature of the GTU according to ISO standards were analyzed. It is noted that the true temperatures for high-temperature GTUs is significantly higher than values determined according to ISO standards. A computational procedure for the determination of gas temperatures in the air-gas channel of the gas turbine and cooling air consumptions over blade rims is proposed. As starting equations, the heat balance equation and the flow mixing equation for the combustion chamber are assumed. Results of acceptance GTU tests according to ISO standards and statistical dependencies of required cooling air consumptions on the gas temperature and the blade metal are also used for calculations. An example of the calculation is given for one of the units. Using a developed computer program, the temperatures in the air-gas channel of certain GTUs are calculated, taking into account their design features. These calculations are performed on the previously published procedure for the detailed calculation of the cooled gas turbine subject to additional losses arising because of the presence of the cooling system. The accuracy of calculations by the computer program is confirmed by conducting verification calculations for the GTU of the Mitsubishi Comp. and comparing results with published data of the company. Calculation data for temperatures were compared with the experimental data and the characteristics of the GTU, and the error of the proposed method is estimated.

Quantitative schlieren diagnostics for the determination of ambient species density, gas temperature and calorimetric power of cold atmospheric plasma jets

A measurement and evaluation technique for performing quantitative Schlieren diagnostics on an argon-operated cold atmospheric plasma jet is presented. Combined with computational fluid dynamics simulations, the method not only yields the temporally averaged ambient air density and temperature in the effluent of the fully turbulent jet, but also allows for an estimation of the calorimetric power deposited by the plasma.The change of the refractive index due to mixing of argon and air is in the same range as caused by the temperature increase of less than 35 K in the effluent of the plasma jet. The Schlieren contrast therefore needs to be corrected for the contribution from ambient air diffusion. The Schlieren system can be calibrated accurately using the signal obtained from the argon flow when the plasma is turned off. The temperature measured in this way is compared to the value obtained using a fibre-optics temperature probe and shows excellent agreement. By fitting a heat source in a fluid dynamics simulation to match the measured temperature field, the calorimetric power deposited by the plasma jet can be estimated as 1.1 W.

The thermal Sunyaev–Zeldovich effect of primordial recombination radiation

It is well known that recombination radiation of primordial hydrogen-helium plasma leads to the distortions of the planckian spectrum shape of the cosmic microwave background radiation (CMB). We discuss the thermal Sunyaev-Zeldovich (SZ) effect with taking into account primordial recombination radiation (PRR). Since in the thermal SZ effect the redistribution of the photons depends on the derivatives of the spectrum, the value of relative correction to SZ effect due to PRR significantly higher than relative corrections due to PRR in the initial spectrum. Calculations of corrections to the thermal SZ effect due to PRR show that depending on the cluster parameters: 1) in the range of frequencies $\nu$ = 0.3 - 700 GHz where the cosmic microwave background (CMB) dominates and spectrum is very close to the planckian one the relative corrections due to PRR have an order of $10^{-9} - 10^{-6}$ of "pure" SZ effect (i.e. SZ effect for pure planckian spectrum). The difference of intensities of PRR coming from different directions (through intracluster and near intercluster medium) reaches values up to 22 mJy/ster at $\nu\simeq 337$ GHz (maximum in considered range). 2) In the range of frequencies $\nu$ = 700 - 5000 GHz where cosmic infrared background (CIB) becomes significant or even dominates the relative corrections due to PRR can reach $10^{-8}$ - $10^{-5}$ of "pure" SZ effect. Corresponding intensity difference reaches values up to 25 mJy/ster (at $\nu\simeq 1700$ GHz). In addition we suggest a modification of the method of electron gas temperature determination using corrections of the SZ effect due to PRR. Such modification allows one to simplify the determination of the cluster electron gas temperature in comparison with known methods.

Simple method for gas temperature determination in CO₂-containing discharges.

A simple gas temperature determination method based on the line ratio between two rotational peaks from the CO Angstrom rotational emission band is reported. A formula based on CO spectral synthesis provides a way for temperature control in plasmas containing CO molecules. This approach is validated in a CO2 flowing gas surfaguide microwave discharge operating at 2.45 GHz. The gas temperature results are compared with the ones obtained using a Boltzmann plot approach, as well as using direct comparison of measured and calculated rotational spectra of the same rotational band.

The Experimental Study of Full-scale Biomass-fired Bubbling Fluidized Bed Boiler

This paper presents experimental data concerning combustion characteristics of full-scale biomass-fired bubbling fluidized bed (BFB) steam boiler with a thermal output of 31 MW. The purpose of the experimental measurements is to show how the values of selected combustion parameters vary in reality depending on measurement position. Experimentation involves specifically a determination of combustion gas temperature and concentration of gas species i.e. O2, CO2, CO and NOX at different positions in the furnace and the flue gas trains. Character of results from the furnace indicates the intermediate stage of thermochemical reactions. Increased levels of CO close to the wall have been found, this may be indicating reducing atmosphere and thereby increased corrosion risk. Results from flue gas trains demonstrate that behavior there is related to the fluid dynamics and heat transfer, the temperature is too low for further combustion reactions. Results show great variations among measured values of all measurands depending on a distance along the line from the wall to the center of the boiler. The measurements from permanently installed fixed sensors are not giving value representing average conditions, but overall profiles can be correlated to online measurements from fixed sensors.

Gas temperature determination in microwave discharges at atmospheric pressure by using different Optical Emission Spectroscopy techniques

Non-thermal plasmas sustained at atmospheric pressure are considered as a very promising technology for different purposes, in which the knowledge of the gas temperature is an important issue. In this paper, the gas temperatures of different argon microwave (2.45GHz) plasma torches were determined by using different Optical Emission Spectroscopy techniques. Thus, they were estimated through the analysis of N2+(B-X) and OH(A-X) molecular spectra. On the other hand, a method based on the measurement of the van der Waals broadening of 588.99nm Na I line was employed, and the temperatures obtained from it were compared to the rotational temperatures derived from N2+(B-X) and OH(A-X) rotational bands. A reasonable good agreement was found between the values of temperatures obtained by using the 588.99nm Na I line and those obtained from N2+ rotational band.

2-D Numerical Modeling of Gas Temperature in Large-Volume Sr Laser Excited in Nanosecond Pulsed Longitudinal ${\rm He{-}SrBr}_{2}$ Discharge

An active volume scaling in bore and length of a Sr atom laser excited in a nanosecond pulse longitudinal He-SrBr2 discharge is carried out. Considering axial symmetry and uniform power input, 2-D model (r, z) is developed by numerical methods for determination of gas temperature in nanosecond pulsed longitudinal He-Ne-SrBr2 discharge to find out the optimal temperature regime for achieving of a maximal multiline average output power.

Spectroscopic diagnostics of laboratory air plasmas as a benchmark for spectral rotational (gas) temperature determination in TLEs

We have studied laboratory low pressure (0.1 mbar ≤ p ≤2 mbar) glow air discharges by optical emission spectroscopy to discuss several spectroscopic techniques that could be implemented by field spectrographs, depending on the available spectral resolution, to experimentally quantify the gas temperature associated to transient luminous events (TLEs) occurring at different altitudes including blue jets, giant blue jets, and sprites. Laboratory air plasmas have been analyzed from the near UV (300 nm) to the near IR (1060 nm) with high (up to 0.01 nm) and low (2 nm) spectral resolution commercial grating spectrographs and by an in‐house intensified CCD grating spectrograph that we have recently developed for TLE spectral diagnostic surveys with ≃0.45 nm spectral resolution. We discuss the results of lab tests and comment on the convenience of using one or another technique for rotational (gas) temperature determination depending on the altitude and available spectral resolution. Moreover, we compare available low resolution (3 nm ≤Δλ≤7 nm) N2 1PG field recorded sprite spectra at 53 km (≃1 mbar), and resulting vibrational distribution function, with 1 mbar laboratory glow discharge spectrum (Δλ=2 nm) and synthetic sprite spectra from models. We found that while the relative population of N2(B3Πg,v=2−7) in sprites and laboratory produced air glow plasmas are similar, the N2(B3Πg,v=1) vibrational level in sprites is more efficiently populated (in agreement with model predictions) than in laboratory air glow plasmas at similar pressures.

A combined vacuum crushing and sieving (CVCS) system designed to determine noble gas paleotemperatures from stalagmite samples

This paper presents a novel extraction device for water and noble gases from speleothem samples for noble gas paleotemperature determination. The “combined vacuum crushing and sieving (CVCS) system” was designed to reduce the atmospheric noble gas contents from air inclusions in speleothem samples by up to 2 orders of magnitude without adsorbing atmospheric noble gases onto the freshly produced grain surfaces, a process that had often hampered noble gas temperature (NGT) determination in the past. We also present the results from first performance tests of the CVCS system processing stalagmite samples grown at a known temperature. This temperature is reliably reproduced by the NGTs derived from Ar, Kr, and Xe extracted from the samples. The CVCS system is, therefore, suitable for routine determinations of accurate NGTs. In combination with stalagmite dating, these NGTs will allow reconstructing past regional temperature evolutions, and also support the interpretation of the often complex stable isotope records preserved in the stalagmites' calcite.

Determination of gas temperature in the plasmatron channel according to the known distribution of electronic temperature

An analytical method to calculate the temperature distribution of heavy particles in the channel of the plasma torch on the known distribution of the electronic temperature has been proposed. The results can be useful for a number of model calculations in determining the most effective conditions of gas blowing through the plasma torch with the purpose of heating the heavy component. This approach allows us to understand full details about the heating of cold gas, inpouring the plasma, and to estimate correctly the distribution of the gas temperature inside the channel.

Determination of gas temperature of high-frequency low-temperature electrodeless plasma using molecular spectra of hydrogen and hydroxyl-radical

In this study we determine gas temperature of He+H2, Ar+H2 and Ne+H2 high frequency electrodeless lamps using intensity distribution in rotational spectra of hydrogen molecule and hydroxyl radical. The measurement results show that OH rotational spectra can be successfully used for estimation of gas temperature of the high-frequency electrodeless lamps at very small amounts of hydrogen present in plasma. The analysis of the measurement results leads to the conclusion that in “pure” plasma the applied energy is used to heat plasma, while for the plasma with hydrogen addition the energy is used in chemical reactions.

On the Gas Temperature Determination from Van Der Waals Broadening in Argon - Neon Microwave Plasmas

Abstract Recently we proposed a method to determine the gas temperature using the van der Waals broadening of atomic spectral lines for atmospheric pressure Ar-He plasma. Here our investigations are continued by studying the influence of Ar*-Ne interactions in order to enlarge the applicability of the proposed method for the determination of gas temperature in argon - neon mixtures. The Ar I 425.9 nm line is found to be suitable for the gas temperature determination.

Analytical Calculation of Gas Temperature and Experimental Determination of Electron Temperature in Gas Discharge in Ne–He Mixtures

Thermal conductivities of binary gas systems are calculated on the basis of existing experimental data and of 12-6 Lennard-Jones and rigid-sphere interatomic interaction approximations for the case of gas discharge in Ne-He mixtures. Assuming that the gas temperature varies only in the radial direction and using the calculated thermal conductivities, an analytical solution of the steady-state heat conduction equation is found for uniform power input. Two cases are considered: taking or not taking into account the radiance of a ceramic tube insert. Measurement of the relative intensities of some He and Ne spectral lines, originating from different upper levels, has enabled us to determine the average electron temperature, using a line-ratio method of optical emission spectroscopy.

Pulsed corona plasma source characterization for film deposition on the inner surface of tubes

A microplasma jet has been constructed for chemical vapour deposition on the inner surface of narrow long tubes and is tested on a quartz tube with the inner diameter of 6 mm and the outer diameter of 8 mm. A long plasma filament (>100 mm) is generated inside the tube in argon with methane admixture. Depending on the quantity of admixture in argon, the negative as well as the positive corona discharges are ignited. Both modes of plasma are characterized using optical emission spectroscopy. For this purpose, nitrogen is admixed with argon and its emission is used for the determination of gas temperature, electron velocity distribution function and electron density at various places along the axis of the tube. The formation of active species, such as C, C2 and CH during the dissociation of methane, is observed through their characteristic emission. The rate of methane dissociation is determined at various places along the axis of the tube during both modes of discharge. Since the chemical kinetics of the film growth process is different, different kinds of films are obtained during different modes of discharge.

Theoretical and experimental determination of gas and electron temperatures for gas discharges in Ne and He mixtures with copper, bromine, hydrogen and strontium

Thermal conductivities of binary gas systems are calculated on the basis of 12-6 Lennard-Jones and rigid sphere inter-atomic interaction approximations for the case of gas discharges in He and Ne with small admixtures of copper, bromine, hydrogen and strontium. Assuming that the gas temperature varies only in the radial direction and using the calculated thermal conductivities, an analytical solution of the steady-state heat conduction equation is found for two discharge tube constructions. Two cases of uniform and non-uniform power input are considered. For both cases the average gas temperature is found by averaging the radial gas temperature distribution over the radius. Measurement of the relative intensities of some He and Ne spectral lines, originating from different upper levels, has enabled us to determine the average electron temperature.

Electronic quenching of OH(A) by water in atmospheric pressure plasmas and its influence on the gas temperature determination by OH(A–X) emission

In this paper it is shown that electronic quenching of OH(A) by water prevents thermalization of the rotational population distribution of OH(A). This means that the observed ro-vibrational OH(A–X) emission band is (at least partially) an image of the formation process and is determined not only by the gas temperature. The formation of negative ions and clusters for larger water concentrations can contribute to the non-equilibrium. The above is demonstrated in RF excited atmospheric pressure glow discharges in He–water mixtures in a parallel metal plate reactor by optical emission spectroscopy. For this particular case a significant overpopulation of high rotational states appears around 1000 ppm H2O in He. The smallest temperature parameter of a non-Boltzmann (two-temperature) distribution fitted to the experimental spectrum of OH(A–X) gives a good representation of the gas temperature. Only the rotational states with the smallest rotational numbers (J ⩽ 7) are thermalized and representative for the gas temperature.