Calculated Gas Temperature Research Articles

Parameters of Surface Microwave Discharge Initiated by the Passage of a Gyrotron Microwave Pulse through a Quartz Plate with Embedded Metal Particles

The results of an experimental study of the initiation, development and maintenance of a plasma surface discharge initiated by microwave (microwave) radiation of a gyrotron (75 GHz, 300 kW, 6 ms) in air under normal conditions on the surface of a quartz substrate with metal inclusions are presented. It is shown that the velocity of the propagation of the discharge ionization front reaches 40 m/s, which corresponds to the thermal conduction propagation mechanism. In this case, the maximum calculated gas temperature of the plasma reaches 5500 K, which leads to the sublimation of metal inclusions. For the first time, the plasma parameters of a surface microwave discharge on metal-dielectric targets, which have been used in various aeroplasma and plasma-chemical applications, are presented.

Error Estimation of Measured Exhaust Gas Temperature in Afterburner Mode in an Aero Gas Turbine Engine

In a turbofan engine, thrust is a key parameter which is measured or estimated from various parameters acquired during engine testing in an engine testbed. Exhaust Gas Temperature (EGT) is the most critical parameter used for thrust calculation. This work presents a novel way to measure and correct the errors in EGT measurement. A temperature probe is designed to measure EGT in the engine jet pipe using thermocouples. The temperature probe is designed to withstand the mechanical and temperature loads during the operation. Structural analysis at the design stage provided a strength margin of 90% and eigenfrequency margin of more than 20%. Thermal analysis is carried out to evaluate maximum metal temperature. Errors are quite high in high-temperature measurements which are corrected using the available methodologies. The velocity error, conduction error, and radiation error are estimated for the measured temperature. The difference of 97 K between the measured gas temperature and calculated gas temperature from measured thrust is explained. The estimated velocity error is 1 K, conduction error is 3 K, and radiation error is 69 K. Based on the error estimation, the measurement error is brought down to 24 K. After applying the above corrections, the further difference of 24 K between measured and estimated value can be attributed to thermocouple error of +/-0.4% of the reading for class 1 accuracy thermocouple, other parameter measurement errors, and analysis uncertainties. The present work enables the designer to calculate the errors in high-temperature measurement in a turbofan engine.

Impact of environmental and installation conditions on the heat exchange process in selected industrial diaphragm gas meters

Since 2016, Oil and Gas Institute – National Research Institute (INiG – PIB) has been conducting new research to determine the relationship between ambient temperature and gas temperature in industrial diaphragm gas meters during the measurement, and to develop new recommendations for billing systems using industrial diaphragm gas meters with a throughput of until 25 m3/h. In the first stage, work was carried out, in which the obtained test results confirmed that the heat exchange process in an industrial diaphragm gas meter depends on the ambient temperature, the gas temperature at the inlet to the gas meter, the flow rate of the gas flowing, as well as the casing surface and the gas volume of the gas meter. In the next stage, work was carried out to determine the relationship between ambient temperature and gas temperature at the industrial diaphragm gas meter connection during the measurement. The obtained results undermined the thesis, which indicated that the gas inlet temperature is equal to the gas temperature at the depth of the gas network. In the last stage, work was carried out to determine the course of changes in gas temperature in industrial diaphragm gas meters as a function of ambient temperature and cyclical changes of the gas flow rate, which were to reflect the work of gas meters installed at customers’ premises. The analysis of the obtained test results once again showed a strong dependence of the gas temperature inside industrial diaphragm gas meters on the ambient temperature, but also on the flow rate of gas. The obtained results of laboratory tests will be used to carry out a thermodynamic description of the heat exchange process in an industrial diaphragm gas meter, which would allow the determination of the gas billing temperature as a function of the ambient temperature, the temperature of the inflowing gas and the gas flow rate. The calculated gas temperature values could be used to determine the temperature correction factors applicable when settling gas consumers billed on the basis of measurement with the use of industrial diaphragm gas meters.

Characterization of the planetary nebula Tc 1 based on VLT X-shooter observations

ABSTRACT We present a detailed analysis of deep VLT/X-Shooter observations of the planetary nebula Tc 1. We calculate gas temperature, density, extinction, and abundances for several species from the empirical analysis of the total line fluxes. In addition, a spatially resolved analysis of the most intense lines provides the distribution of such quantities across the nebula. The new data reveal that several lines exhibit a double peak spectral profile consistent with the blue and redshifted components of an expanding spherical shell. The study of such components allowed us to construct for the first time a three-dimensional morphological model, which reveals that Tc 1 is a slightly elongated spheroid with an equatorial density enhancement seen almost pole on. A few bright lines present extended wings (with velocities up to a few hundred km s−1), but the mechanism producing them is not clear. We constructed photoionization models for the main shell of Tc 1. The models predict the central star temperature and luminosity, as well as the nebular density and abundances similar to previous studies. Our models indicate that Tc 1 is located at a distance of approximately 2 kpc. We report the first detection of the [Kr iii] 6825 Å emission line, from which we determine the Krypton abundance. Our model indicates that the main shell of Tc 1 is matter bounded; leaking H ionizing photons may explain the ionization of its faint AGB-remnant halo.

Time efficient radiation model for determination of plasma parameters in atmospheric plasmas

A simple and time efficient model for atmospheric arc plasmas is presented in this work. It uses experimentally recorded emission spectra in order to estimate radial temperature and electron density profiles in welding arc plasmas. The plasma parameters are calculated using the Elenbaas–Heller and Saha equations, together with welding current, gas composition and simplified cylindrical arc geometry with a particular radius as input parameters. From these parameters an emission spectrum is calculated under the assumption, that the individual lines are mainly broadened due to the Stark effect. Here only second order perturbation theory for the Stark effect without any further influences of ion collision or other additional effects is considered. The comparison of measured and calculated spectra leads to a cost function. Its minimisation is used to find the radius of the arc model. This model was successfully applied for the estimation of plasma parameters in gas tungsten arc welding processes with argon and argon–helium as shielding gases. The calculated gas temperature and electron density profiles were compared with experimental data obtained by Thomson scattering. Further extension of the model for dynamic processes containing metal vapours and its application in feedback control are planned in the future.

A Convenient Method to Realize Large-Area APGD for Wool Surface Modification

In this paper, a method of realizing large-area atmospheric pressure glow discharge (APGD) plasma in ambient air was investigated. The dielectric barrier discharge (DBD) type was adopted, and the electrode arrangement of a tubular array was designed to achieve large-area APGD (about $1000 \times 60$ mm $^{2}$ ). Optical emission spectroscopy (OES) was used to identify active particles and calculate gas temperature. The results show that the seed electrons can react with N2, O2, and H2O in the air to produce N2 (C-B), N2+, OH, and O3. The gas temperature was calculated to be 410 K–514 K, which is suitable for low-added-value materials treatment. The homogeneity of the plasma temperature was also verified by an infrared camera. Furthermore, a prototype for the wool surface modification was also investigated. The scanning electron microscope (SEM) micrographs and wettability test were adopted, which shows that the plasma can damage the squamae of the natural wool to improve the wettability greatly without burning the wool fiber.

Determining Total Radiative Intensity in Combustion Gases Using an Optical Measurement

A method is presented whereby spectral radiation measurements made in a combustion flue gas can be used with a spectral gas absorption model to calculate gas temperature, H2O concentration, CO2 concentration, and total radiation intensity for the gas. Measured spectral intensities from a natural gas-air flame in a 150 kWth furnace were used in conjunction with a spectral gas absorption model to calculate gas temperature and H2O concentration. The measured spectral intensities matched spectral intensities predicted by a one-dimensional intensity model when peaks were shifted and convolved to account for FTIR biases. On the basis of a successful prediction of intensities in the measured range of 1.709–2.128 μm, the calibrated intensity model was used to predict intensities for various wavelength bands including H2O and CO2 relative contributions. The total intensity for a wavelength range of 1–50 μm for the conditions studied was 10 659 W/m2/sr, with an equivalent total gas emissivity of 0.163.

Investigations of discharge and post-discharge in a gliding arc: a 3D computational study

In this study we quantitatively investigate for the first time the plasma characteristics of an argon gliding arc with a 3D model. The model is validated by comparison with available experimental data from literature and a reasonable agreement is obtained for the calculated gas temperature and electron density. A complete arc cycle is modeled from initial ignition to arc decay. We investigate how the plasma characteristics, i.e., the electron temperature, gas temperature, reduced electric field, and the densities of electrons, Ar+ and ions and Ar(4s) excited states, vary over one complete arc cycle, including their behavior in the discharge and post-discharge. These plasma characteristics exhibit a different evolution over one arc cycle, indicating that either the active discharge stage or the post-discharge stage can be beneficial for certain applications.

Use of thermocouples and argon line broadening for gas temperature measurement in a radio frequency atmospheric microplasma jet.

This paper presents the use of thermocouples and line broadening of argon 2p-1s emission lines for the measurement of gas temperature of an atmospheric argon microplasma jet. The measured temperatures are compared with rotational spectra fitting of OH (A-X) and N2 (C-B) emission. An rf microplasma jet with two electrical configurations and different temperature ranges was used. The calculated gas temperatures with thermocouples, argon lines, and OH ranged from 290 to 423 K and 393-510 K for the two configurations, depending on the rf power. The temperature from fitting the N2 spectra overestimated the gas temperatures in both configurations (593-680 and 664-853 K). The non-nitrogen temperature measurements agree well with each other within the measurement uncertainty. The results show that not all optical emission temperature methods are appropriate and the accuracy of argon line broadening is dependent on the device configuration. The results also show that conventional thermocouples are surprisingly accurate and viable for these plasmas.

Modeling of a Non‐Thermal RF Plasma Jet at Atmospheric Pressure

An RF driven non‐thermal atmospheric pressure plasma jet used for plasma enhanced chemical vapor deposition is investigated by hydrodynamic modeling. The model describes the gas flow and heating, the plasma generation in the active zone, reactions of active plasma particles with precursor molecules in the effluent, and the transport of precursor fragments toward the substrate. Molecular argon ions are found to be the dominant active species transported into the effluent together with slow electrons. The radial profiles of the fluxes of precursor fragments onto the substrate depend sensitively on the flow conditions. Satisfactory agreement of the calculated gas temperature with measured profiles is obtained.

Study of argon–oxygen flowing afterglow

The reaction kinetics in argon–oxygen flowing afterglow (post-discharge) was studied using NO titration and optical emission spectroscopy. The flowing DC post-discharge in argon–oxygen mixture was created in a quartz tube at the total gas pressure of 1000 Pa and discharge power of 90 W. The O(3P) atom concentration was determined by NO titration at different places along the flow tube. The optical emission spectra were also measured along the flow tube. Argon spectral lines, oxygen lines at 777 nm and 844.6 nm and atmospheric A-band of were identified in the spectra. Rotational temperature of was determined from the oxygen atmospheric A-band and also the outer wall temperature of the flow tube was measured by a thermocouple and by an IR thermometer. A zero-dimensional kinetic model for the reactions in the afterglow was developed. This model allows the time dependencies of particle concentrations and of gas temperature to be calculated. The wall recombination probability for O(3P) atoms and wall deactivation probability for (b ) molecules were determined from the fit of model results to experimental data. Sensitivity analysis was applied for the analysis of kinetic model in order to reveal the most important reactions in the model. The calculated gas temperature increases in the afterglow and then decreases at later afterglow times after reaching the maximum. This behavior is in good agreement with the spatial rotational temperature dependence. A similar trend was also observed at outer wall temperature measurement.

Simulation of microwave-induced formation of gas bubbles in liquid n-heptane

A model has been built and the formation of gas bubbles by exciting an atmospheric-pressure microwave discharge in liquid n-heptane has been numerically simulated in the approximation of axial symmetry. The model is based on the simultaneous solution of Maxwell’s equations, Navier–Stokes equations, the heat conduction equation, a balance equation for the electron number density (using the ambipolar diffusion approximation), Boltzmann’s equation for free plasma electrons, and the overall equation for the thermal degradation of n-heptane. The two-phase medium has been described using the phase field method. The calculation has made it possible to describe both the dynamics of the formation of gas bubbles in the liquid and the thermal processes in the system. The calculated gas temperature in the gas bubble with the plasma is in agreement with the measurement results.

Molecular line mapping of the giant molecular cloud associated with RCW 106 – IV. Ammonia towards dust emission

Here we report observations of the two lowest inversion transitions of ammonia with the 70-m Tidbinbilla radio telescope. They were conducted to determine the kinetic temperatures in the dense clumps of the G333 giant molecular cloud associated with RCW 106 and to examine the effect that accurate temperatures have on the calculation of derived quantities such as mass. This project is part of a larger investigation to understand the timescales and evolutionary sequence associated with high-mass star formation, particularly its earliest stages. Assuming that the initial chemical composition of a giant molecular cloud is uniform, any abundance variations within will be due to evolutionary state. We have identified 63 clumps using SIMBA 1.2-mm dust continuum maps and have calculated gas temperatures for most (78 per cent) of these dense clumps. After using Spitzer GLIMPSE 8.0 $\mu$m emission to separate the sample into IR-bright and IR-faint clumps, we use statistical tests to examine whether our classification shows different populations in terms of mass and temperature. We find that clump mass and column density show no significant population difference, and that kinetic temperature is the best parameter to distinguish between the gravitationally bound state of each clump. The kinetic temperature was the only parameter found to have a significantly low probability of being drawn from the same population. This suggests that clump radii does not have a large effect on the temperature of a clump, so clumps of similar radii may have different internal heating mechanisms. We also find that while the IR-bright clumps have a higher median virial mass, both samples have a similar range for both virial mass and FWHM. There are 87 per cent (40 of 46) of the clumps with masses larger than the virial mass, suggesting that they will form stars or are already undergoing star formation.

Temperature of a partially embedded connection subjected to fire

When subject to fire, structural steel and connectors lose both their strength and stiffness. Structures expand when heated and contract on cooling. Furthermore, the effect of restrained thermal movement can introduce high strains in both the steel member and the associated connections. Fire tests on steel structures have shown that the temperature within the connections is lower compared to the connected steel members. The beneficial effect of the partial embedding of a connection in a concrete slab for its resistance in fire conditions was already intuitively utilised by structural engineers. Three sets of tests provide the measuring of the accuracy of the developed numerical and analytical model for heat transfer and temperature distribution in the partially embedded connections. The connection shadow factor is proposed further to allow the prediction of temperatures in connections from the calculated gas temperature during a post-flashover fire.

先端可視化: Temperature Sensitive Particles

The instantaneous wall temperature was measured in an RCEM/engine cylinder, with or without the fire, by the phosphor thermometry. The measured wall temperature and its distribution had good correlation with a change of calculated gas temperature from the pressure. An oil flow and a gaseous flow in the cylinder were measured using a high speed camera, a single-pulsed UV laser and temperature sensitive phosphor particles. The temperature was calculated from the lifetime and the velocity was obtained from the phosphor particle images during a single decay. The temperature changes dependently on the crank angle agreed qualitatively with the gas temperature estimated from the pressure.

A study of combustion and emission formation characteristics during production engine transients using optical diagnostics

In order to identify some of the special combustion and emission formation phenomena that occur in a turbocharged heavy-duty diesel engine during transient operation, the transient strategy of a production engine has been characterized at four different engine speeds. From each transient some points have been selected for further investigation by recreating these load points as steady-state points in a single-cylinder engine. This allows the emissions to be measured with a high degree of accuracy. An endoscope which makes it possible to evaluate flame temperatures was used in both engines. An empirically derived method of calculating nitric oxide (NO) formation from a combination of measured flame temperature, calculated gas temperature, and heat release rate has been developed and applied. This provides an increased understanding of combustion and emission formation phenomena during transient operation. An optical engine was also used to provide a full combustion chamber view for some of the operating points, and a specially developed software was used to calculate temperature distributions based on high-speed camera colour information. The NO formation formula was applied on these images, which resulted in spatially resolved NO formation distributions.

Combined Measurement of Temperature and Velocity of a Gaseous Flow in an Optical Engine Using Phosphor Particles

A combined velocity and temperature measurement method using a high speed camera, a single-pulsed UV laser and temperature sensitive phosphor particles had been proposed. The method was extended to a measurement of a gaseous flow at high temperature. The phosphor particles are the powders of rare earth-doped ceramics, which have strong sensitivity to temperature, resulting in a small intensity and a short lifetime of luminescence at high temperature. The phosphor material was painted on the solid wall in an engine cylinder, and the instantaneous wall temperature was measured, in order to confirm the applicability of phosphor particles to the in-cylinder measurement. The measured wall temperature increased with the increase of measured pressure in the cylinder. The measured wall temperature distribution and its temperature had good correlation with a change of calculated gas temperature from the pressure. Then, the combined temperature and velocity measurement of the gas flow in the cylinder was performed. The temperature was calculated from the lifetime and the velocity was obtained from the phosphor particle images during a single decay. Two dimensional velocity and temperature distribution in the engine cylinder was successfully visualized. The temperature changes dependently on the crank angle agreed qualitatively with the gas temperature estimated from the pressure. However, the absolute values of the measured temperature had differences from the estimated ones.

Simulation of turbulent combustion and NO formation in a swirl combustor

A presumed probability density function (PDF) model for temperature fluctuation is proposed and formulated in this paper. It incorporates a two-step reaction mechanism for propane combustion and the thermal and prompt NO formation mechanisms. The present model, together with a new algebraic Reynolds stress model (ASM), is employed to simulate the turbulent combustion and NO formation in a swirl combustor. The calculated propane, carbon monoxide, and carbon dioxide concentrations agree with the measurement. The calculated gas temperature and oxygen and NO concentrations are in general agreement with the measured data. The simulated results show that NO forms mainly in the upstream region of the combustor. The flue gas recirculation effectively abates the nitrogen oxides ( NO x ) emission in the combustor.

Study on the Combustion Model and Turbulent Model for Thermal-Flow Analysis of Impinging Jet Flame during line Heating Process

A new turbulent combustion model to predict thermal flow in the impinging jet flame, which is based on mixing controlled reaction rates, is developed. The main feature of the proposed model is that the rate of the combustion will be determined by the rate of dissipation of eddies and concentration of fueloxygen in the flame. The proposed model is proved to be the most effective in the practical computation of impinging jet flame during line heating process by comparing calculated gas temperature with the measured one.

Study on Combustion Analysis in the Impinging Jet Flame during Line Heating Process

In order to analyze heat flow in the impinging combustion flame which is generated during line heating process, a 3-dimensional computer program has been developed.Reduced reaction mechanism model and Mixing combustion model are employed in this program.It is found that the calculated gas temperature distribution in the flame is in agreement with the experimental one except the peak temperature of center part of the flame when Mixing combustion model is employed.