Determination Of Gas Temperature Research Articles

A comparative study of gas temperature determination in non-thermal atmospheric pressure plasma jet by spectral analysis and scattering technique for plasma-catalyst measurements

Comparison and validation of different methods for the measurements of plasma gas temperature were studied. The investigations depend on optical emission spectroscopy OES, laser scattering technique, and line-broadening mechanisms. The rotational temperature of the second positive system SPS (C3 ∏+ u - B3 ∏+ g) around 380 nm, second positive system SPS at 337.1 nm of nitrogen molecule (C3 ∏+ u - B3 ∏+ g), and first negative system FNS at 391.4 nm of nitrogen ion (B2Σu +→X2Σg +) were investigated. Moreover, Raman scattering spectra at 532 nm were used to measure the gas temperature in the plasma jet. Gas temperature from the emission line broadening method was also calculated. The role of non-thermal plasma in assisting NOx reduction over an Ag/Al2O3 catalyst at low temperatures using simulated diesel fuels (toluene) was confirmed. Importantly, a significant activity of both NOx and hydrocarbons oxidation was observed and obtained at low gas temperatures. It was found that there is a clear correlation between the gas temperature and the conversion efficiency of the catalyst under different operating conditions of the plasma reactor. The main objective of this investigation was to confirm the important role of the non-thermal plasma in catalyst activation at low gas temperatures compared to traditional thermal activation.

Experimental analysis and modeling of gas turbine engine performance: Design point and off-design insights through system of equations solutions

In this article, a systematic approach is presented for simulating turbojet engine performance at both design and off-design points. The construction of gas turbine engines involves a core, with additional components added based on the proposed methodology. Accurate formulation of component characteristics and their matching forms the basis for the system of equations needed for solving off-design engine performance. The developed algorithm's initial step involves comparing results with experimental data obtained from 230 N engines. Experimental testing utilizes a 780 N engine under diverse operating conditions, allowing determination of thrust values, fuel consumption, and outlet gas temperatures. An engine characteristic curve is derived under static conditions at ground level and validated against ground test results in Tehran. Unknown parameters are calibrated using a dedicated model, enabling the extraction of engine performance parameters across different corrected speeds. These results are then compared with GasTurb outputs. Comparative analysis between the proposed model's simulation and experimental data demonstrates high accuracy, affirming the reliability of the presented model.

Fabric and Fluid Inclusions Characterization of a Stalagmite from Eastern Spain: A Precondition for Noble Gas Analysis by Step-Crushing Methodology

Fluid inclusions in stalagmites are becoming increasingly important for paleoclimate research. Within this framework, noble gas thermometry, based on noble gases dissolved in water from fluid inclusions, provides quantitative estimations of cave air paleotemperature. Two major issues of Noble Gas Temperature (NGT) determination on speleothems are (1) the potential lack of enough water for the analysis and (2) the presence of trapped gas not dissolved in water that can be released during the analysis from biphasic or all-gas fluid inclusions, as its contribution to the bulk noble gas signal can hinder NGT results. Although the step-crushing method helps to reduce the second issue, it also decreases the amount of water available for the calculations. In order to obtain reliable NGT results with low uncertainties, a major challenge is still to reach a balance between sufficient water for analysis and a small amount of “atmospheric” gas. The difficulty is that the extraction process cannot be standardized since it strongly depends on the type of sample. The objective of this work is to investigate how the characteristics of the speleothem can determine the adequacy of the extraction process. For this purpose, we consider a stalagmite from a Mediterranean cave that consists of columnar elongated calcite and contains a significant quantity of fluid inclusions, which suggests good potential for NGT analysis. Results, however, were poorly satisfactory. Trying to understand the source of the problems, an integrated study of petrography and petrophysical features was performed. The samples were found to be different depending on the stage of coalescence of crystals and thus separated into “open” and “closed” fabrics. Classic petrographic analysis and non-destructive (nuclear magnetic resonance) techniques were used to characterize the type and amount of fluid inclusions present in both types of fabrics. The study indicates that the closed fabric (total coalescence of calcite crystals) has most water trapped in water-filled, small intracrystalline fluid inclusions that usually contain very little gas. This fabric is very suitable for NGT determination, but since the amount of water is quite small, the sample should be crushed in only one step with a large number of beats to break all the inclusions. In contrast, samples with open fabric (partial coalescence of calcite crystals) contain a higher amount of water and, also, gas-filled large intercrystalline fluid inclusions. For this fabric, step-crushing of the sample is necessary. However, the low amount of water left for the second and third crushings could lead to flawed NGT results. Thus, we suggest modifying the method to get rid of part of the gas in the first crushing while leaving enough water for the following steps. This work shows the importance of characterizing speleothems and fluid inclusions, including their petrography and petrophysical characteristics, before starting NGT analysis, allowing the selection of the most favorable samples and the customization of the step-crushing procedure.

Validation of a Generic Non-Swirled Multi-Fuel Burner for the Measurement of Flame Stability Limits for Research of Advanced Sustainable Aviation Fuels

Future aviation concepts should be both CO2-neutral and without other emissions. One approach to reaching both targets is based on sustainably produced synthetic liquid fuels, which may allow very clean, lean premixed prevaporized (LPP) combustion. For that, fuels are needed with much longer ignition delay times and a lower flashback propensity than current jet fuels. We describe an experimental setup to investigate the flashback stability of liquid fuels in a multi-fuel burner. In this work, the measurement procedure and the determination of the experimentally obtained accuracy are in focus with regard to prevaporized and preheated iso-propanol/air flames in an equivalence ratio range of 0.85 to 1.05 involving three preheating levels (573, 673, and 773 K). As the determination of the accurate unburnt gas temperature just ahead of the flame is of strong importance for flashback but not directly possible, a model is implemented to determine it from the measurable quantities. Even with this indirect method, and also regarding the hysteresis of the experimental preheating temperature, it is found that the relevant quantities, namely, measured temperatures, mass flows, and values derived from them, can be determined with accuracy in the range below 1.7%.

Two-color four-wave mixing contribution to an electrostrictive laser-induced grating signal in CO2-N2 mixtures and gas diagnostics.

Multiparameter determination in the gas phase using the versatile laser-induced grating (LIG) technique is a challenging task due to interdependence of observables on multiple thermodynamic parameters. In C O 2-N 2 mixtures, simultaneous determination of species concentration and gas temperature can be achieved by using an additional C O 2 concentration-dependent contribution to the LIG signal, which appears if 1064 nm pump pulses are employed. This contribution can be attributed to a direct, quasi-resonant two-color four-wave mixing (TCFWM) of the pump and probe radiations in C O 2. A detailed study of the laser power and beam polarization, as well as mixture composition, pressure, and temperature dependencies of the TCFWM intensity relative to that of the LIG signal, allowed for the formulation of analytical relations enabling simultaneous mixture composition and temperature determination.

A Global Model Study of Plasma Chemistry and Propulsion Parameters of a Gridded Ion Thruster Using Argon as Propellant

This work reports on the (zero-dimensional) global model study of argon plasma chemistry for a cylindrical thruster based on inductively coupled plasma (ICP) whose output has a system of two grids polarized with each other with direct current potential. The global model developed is based on particle and energy balance equations, where the latter considers both charged and neutral species. Thus, the model allows the determination of the neutral gas temperature. Finally, this study also investigated the role of excited species in plasma chemistry especially in the ions production and its implications for propulsion parameters, such as thrust. For this, the study was carried out in two different scenarios: (1) one taking into account the metastable species Arr and Arp (multi-step ionization), and (2) the other without these species (single-step ionization). Results indicates a distinct behavior of electron temperature with radiofrequency (RF) power for the investigated cases. On the other hand, the gas temperature is almost the same for investigated power range of up to 900 W. Concern propulsion analysis, a thrust of 40 mN at 450 W was verified for case (1), which represents a remarkable thrust value for electric thrusters.

Oxygen atoms and nitrogen molecules as spectroscopic probes for the temperature determination in non-equilibrium cryogenic helium plasma jets

Determination of the gas temperature in the afterglow plasma jet of pre-cooled helium propagating inside a dense helium vapor at 1.4 K is a difficult task. In this work we analyze the possibility of using the emission spectra from oxygen atoms and nitrogen molecules for deducing the local temperature of the gas. Oxygen is always present as a trace impurity (∼1 ppm) in helium gas and strong emission of the atomic 777 nm triplet lines can be a good candidate because the energy gaps of 3.67 cm−1 (T ∼ 5.3 K) and 2.02 cm−1 (T ∼ 2.9 K) between the sub-levels of its upper state O(5P J ), with J = 1, 2 and 3, are comparable to the kinetic energy of atoms in a cryogenic environment. A detailed analysis of the kinetics of atoms in the O(5P J ) state indicates that at temperatures lower than 10 K, the population transfers between sub-levels are not efficient enough for the establishment of a Boltzmann equilibrium within the sublevels before the radiative decay of O(5P J ) atoms. We suggest the presence of small energy barriers in the He-O(5P J ) transient molecule formed during the collision. It was also shown that the temperature of a gas in non-equilibrium cryogenic helium plasmas containing at least 100 ppm of nitrogen can be determined from the rotational spectra of the 2–0 and 3–1 bands of the first positive system and the 8–3 band of the infrared afterglow system of molecular nitrogen. The application of PGOPHER software (1-T method) gives the rotational temperature of N2 molecules averaged over the observation area and is optimal for the gas temperature determination in locally homogeneous plasmas or mapping the temperature in inhomogeneous plasmas with high spatial resolution. A home-made code to simulate rotational spectra with two temperatures (2-T method) allows determination of the temperature span within the observation region of an inhomogeneous plasma.

Ultra-high-resolution optical absorption spectroscopy of DC plasmas at low pressure using a supercontinuum laser combined with a laser line tunable filter and a HyperFine spectrometer

Optical absorption spectroscopy of non-equilibrium plasmas using a supercontinuum laser combined with a laser line tunable filter and a HyperFine spectrometer is examined. Owing to the <2 pm spectral resolution of the HyperFine system, details on the absorption line intensity, position and width can be obtained with very high precision using a broadband light emission source. As an example, absorption spectroscopy measurements were recorded in a reduced-pressure, nominally pure argon DC plasma column and allowed for the determination of the neutral gas temperature and the Ar 1s2 and Ar 1s4 (Paschen notation) number densities. At a pressure of 1 Torr, a discharge current of 20 mA, and an absorption length of 18 cm, the analysis of the Ar 2p3-1s2 and Ar 2p8-1s4 absorption lines at respectively 840.8 nm and 842.5 nm resulted in number densities of 5.5 1015 m−3 and 1.1 1016 m−3 and a neutral gas temperature of T g = 340 K. These values are typical of DC discharges operated under similar experimental conditions. While the fractional absorption of both lines decreased with decreasing optical absorption path, the number densities remained the same, as expected. Finally, the number densities increased with increasing discharge current, a result also coherent with the literature.

Shifted-excitation rotational Raman spectroscopy and Bayesian inference for in situ temperature and composition determination in laminar flames

Optical, non-invasive techniques for temperature and mole fraction measurements in flames and other reactive flows are often limited to applications under well-defined laboratory environments. These limitations mainly arise from various prerequisites of the techniques e.g. regarding the optical accessibility of the systems under investigation, its environmental conditions such as vibrations and temperature or the need of tracers inside the flow. In order to weaken these constrains, we present a robust, fiber-based sensor system, utilizing tracer-free spontaneous rotational Raman spectroscopy with tunable near-infrared (NIR) continuous-wave laser-excitation capable of a simultaneous point-wise determination of gas temperature and mole fractions in laminar spatially uniform non-sooting reactive flows. Benefits and limits of this method are evaluated investigating a laminar premixed methane/air flat-flame of a McKenna-type burner. In that case, the main rotational Raman-active and, therefore, detectable compounds are nitrogen, oxygen and carbon dioxide. For the subtraction of flame luminosity two different techniques were used: simple background subtraction (BGS) and shifted-excitation Raman difference spectroscopy (SERDS). For both methods, the corrected spectra are matched to simulated spectra via a least-square fit algorithm in order to extract the quantities of interest. Hereby, Bayesian inference enables the determination of the uncertainties of the results. The consideration of the covariance within the multi-variate analysis allows for the combination of the BGS and SERDS method to establish a more advanced analysis routine.

Temperature measurement based on adaptive dual-comb absorption spectral detection

We demonstrate absorption spectroscopy of water vapor for the determination of gas temperature. An adaptive dual-comb detection system is utilized to obtain precise spectroscopic data in a broadband range from 7143 to 7240 cm−1 with a spectral resolution of 0.049 cm−1. The measured spectra are in accordance with the simulated results from the HITRAN (high-resolution transmission molecular absorption) database. Several measurements are investigated in the temperature range of 500–1000 K, revealing relative deviations of less than 5% compared to the thermocouple. This broadband and accurate adaptive dual-comb spectral detection method could be a powerful tool for non-invasive combustion diagnosis.

Accurate Measurements of the Gross Calorific Value of Methane by the Renewed GERG Calorimeter

Due to the commercial transfer of billions of cubic meters of natural gases, the knowledge of the gross calorific value (GCV) of the main natural gas components and, in particular, of methane, is of outstanding interest. On the basis of previous work carried out by a Groupe Européen de Recherches Gazières (GERG)–Physikalisch-Technische Bundesanstalt collaboration, the so-called GERG calorimeter was further developed on the hardware as well as on the software side. With the renewed GERG calorimeter, the GCV of CH4 could be determined with unprecedented precision and accuracy. Important elements for improving the measuring methodology of flame calorimetry included the in situ calibration of the mass of the burned gas, the determination of the actual exhaust gas temperatures, and the detection of the water input by countercurrent water absorption from ambient air. For the first time, it was possible to determine the GCV not only via direct online weighing of the mass of burned gas but also via the stoichiometric water balance with a consistency of about 3.5 ppm. Based on 27 weighings of the mass of burned gas, the real-gas GCV of methane is determined as Hs(CH4) = 890 202.1 J mol−1 with a confidence interval of ±52.6 J mol−1 (t95% = 2.056). This value is by ΔHs/Hs = (−0.0436 ± 0.0059)% below the real-gas GCV of Hs(CH4) = (890 590 ± 380) J mol−1 (k = 2) converted according to ISO 6976:2016. The difference can be explained by systematic influences as well as by failures in the stoichiometric water balance in all other measurements.

Determination of gas temperature in the flow

The paper presents the results of thermal experimental studies, the purpose of which is to obtain the values of the gas flow temperature by the method gradient of the volume (mass) consumption. Explored the pipeline that is heated for on the short middle section. An equation was derived to determine the temperature of the gas in the heating zone by the measured static pressure before heating and after it and the gas consumption before and after heating. The practical significance lies in determining the thermodynamic parameters of the gas in the in the tract of the electrothermal Microdrive of a small spacecraft, when the experimental conditions and design features of the engine do not allow other methods to be used.

Cylinder Pressure-based Virtual Sensor for Gas State Estimation During Compression Stroke

Abstract The gas state during the compression stroke can vary depending on the operating conditions and cycle-to-cycle variations. In this research, determination of polytropic exponent, trapped mass, and gas temperature are addressed. A golden section search method is applied to cyclic polytropic exponent estimation, and then a statistical filter is employed for cyclic estimation to filter out the estimation noise. A novel iterative-∆p-method is finally presented for the determination of the trapped mass and gas temperature simultaneously during the compression stroke. A sequence of trapped mass estimates and a sequence of gas temperature estimates can be obtained along crank angle position. Experimental validations carried out on a gasoline engine demonstrate the effectiveness of the presented methods.

Design of an imaging Fabry-Pérot interferometer for the VEST edge plasma temperature measurement.

A new technique for gas temperature determination in fusion plasmas based on time- and space-resolved imaging interferometry is presented. The proposed imaging interferometer includes a multi-channel optical fiber bundle, a pair of flat mirrors, collimating lenses, and a fast camera for registration of interferometry fringes. The technique is applied for ion temperature measurements in the Versatile Experiment Spherical Torus (VEST) tokamak located at the Seoul National University. The multi-channel operation regime of the interferometer is studied by simulations. The first experimental two-channel results obtained using the Hα emission line from the VEST plasma edge are presented and analyzed. The mentioned apparatus is suggested to be especially useful for the multi-point time-resolved characterization of the non-repetitive processes in low-temperature regions of fusion plasmas.

Plasma diagnostic by optical emission spectroscopy on reactive magnetron sputtering plasma –A Brief Introduction

Optical emission spectroscopy has been employed as non-invasive plasma diagnostics method and it is to detect the light emission during titanium nitride deposition using magnetron sputtering plasma discharge. The optical emission from argon and titanium were used to observe the ionization ratio of each element during the discharge. Then, the optical emission of nitrogen spectrum was used for the calculation of gas rotational temperature by using a simple formula and it was evaluated at various discharge conditions. A comparative of two different spectrometers resolution have been used for the determination of gas temperature. The results showed that the evaluated temperatures were almost the same as expected in high-pressure magnetron sputtering plasmas even when using low-resolution of spectrometer.

Validation of the van der Waals broadening method for the determination of gas temperature in microwave discharges sustained in argon–neon mixtures

Gas temperature is a key parameter to understand the processes that take place in a plasma because this temperature is related to the energy of the heavy plasmas particles which participate in the atomization of molecules and the formation of radicals from the substances introduced into the discharges. The method for the measurement of gas temperature in argon-helium plasma at atmospheric pressure, using the van der Waals broadening of spectral atomic lines, is adapted for the case of argon–neon mixtures. The Ar I lines 425.9 nm and 603.2 nm are determined as recommendable for such measurements, especially when the use of OH radicals is difficult or the contribution of these radicals to the plasma pollution is to be avoided.

Using the Pairs of Lines Broadened by Collisions with Neutral and Charged Particles for Gas Temperature Determination of Argon Non-Thermal Plasmas at Atmospheric Pressure

The spectroscopic method for gas temperature determination in argon non-thermal plasmas sustained at atmospheric pressure proposed recently by Spectrochimica Acta Part B 129 14 (2017)—based on collisional broadening measurements of selected pairs of argon atomic lines, has been applied to other pairs of argon atomic lines, and the discrepancies found in some of these results have been analyzed. For validation purposes, the values of the gas temperature obtained using the different pairs of lines have been compared with the rotational temperatures derived from the OH ro-vibrational bands, using the Boltzmann-plot technique.

Stagnation Temperature Measurements in a Shock-Tunnel Facility Using Laser-Induced Grating Spectroscopy

Experimental determination of test gas temperature and enthalpy in ground testing is a challenging task, particularly regarding excessive pressure and temperature levels as well as minimum characteristic time scales available in transient facilities. Accurate knowledge of test gas conditions and stagnation enthalpy in reentry experiments is, however, crucial for a valid comparison with numerical results. Therefore, to contribute to a more accurate quantification of nozzle flow upstream boundary conditions, laser-induced grating spectroscopy is applied to the nozzle reservoir section of the piston-driven reflected shock tunnel High-Enthalpy Laboratory Munich for nonintrusive stagnation temperature measurement. Single-shot determination of post-shock wave gas temperature involves exact synchronization of the transient event in the test bench with the optical setup. Problems arising from impulse facility recoil are solved and discussed with respect to the laser light geometrical optical pathway. Employing minimum selective seeding by nitric oxide for improved signal intensity, gas temperatures of around 1100 K behind the reflected shock wave are measured by resonant laser-induced grating spectroscopy for a representative low-enthalpy operation condition in air, at pressure and enthalpy of 6 MPa and , respectively.

Confirmation of OH as good thermometric species for gas temperature determination in an atmospheric pressure argon plasma jet

We have proved that the temperatures determined from OH rotational spectra accurately describe the actual gas temperatures in an atmospheric pressure argon plasma jet, expanding in a hot ambient atmosphere. For this, we have operated the radiofrequency jet discharge inside a heated oven at various decreasing forwarded powers and increasing gas flow rates. We compared the rotational temperature values with the temperature of the oven. When extrapolated to zero power or infinite gas flow, the data describing the dependence of the rotational temperatures upon power and mass flow rate indicate the correct oven temperature. We demonstrate that the population of the rotational levels of the OH molecule is in equilibrium with the translational motion of the argon atoms in the plasma jet, from room temperature (RT) to 500 °C.

Gas temperature determination of non-thermal atmospheric plasmas from the collisional broadening of argon atomic emission lines

In this work we propose a new method allowing gas temperature determination in argon non-thermal plasma jets, based on the measurement of the collisional broadening of different argon atomic lines corresponding to transitions into both resonance levels s2 and s4 of the 3p54s configuration. The method was developed for fourteen lines: Ar I 978.45, 935.42, 922.45, 852.14, 840.82, 826.45, 750.39 (corresponding to transitions falling to level s2) and 965.77, 842.46, 810.37, 800.62, 751.46, 738.40, 727.29nm (corresponding to transitions falling to level s4). A carefully study of the relative importance of all broadening mechanisms to the whole profile for these lines, under a broad range of experimental conditions, revealed that for electron densities and gas temperature lower than 1015cm−3 and 2000K, the Stark and Doppler broadenings can be neglected in the method, but the van der Waals contribution should not be ever discarded for gas temperature determination. The gas temperature of a microwave non-thermal plasma jet was determined using nine of these lines. Results were consistent with each other, and with those obtained from the rotational temperature derived from OH ro-vibrational band. Also, the influence of the air entrance on the collisional broadening of the lines has been studied and the way the method should be modified to include this effect is indicated.