Gas Temperature Measurements Research Articles

Real-time analysis of dry start-up characteristics of polymer electrolyte membrane fuel cell with water storage process under pressurized condition

Polymer electrolyte membrane fuel cells need humidification for proper operation. A membrane humidifier humidifies the gas supplied to the cell. Additional power is not required; however, the large pressure drop and large volume are disadvantageous. To minimize the role of the humidifier, the pressurized operation and water storage process (WSP) was adapted during dry start-up to accumulate the water generated by the reaction. A segmented cell was used. The relative humidity of the discharged gas was analyzed at the cathode outlet. For extreme dry conditions, dehydrated hydrogen and air at 30 °C and 50 °C, respectively, were used. The fuel cell showed easier hydration in the pressurized operation; the performance of the dry start-up improved under high operating pressure. The WSP was effective for all pressure condition, but its effect could not be maintained for high temperature dry start-up. Because water accumulation in the cell at high pressure facilitates hydration, successful dry start-up is possible at high operating temperatures. The dew point temperature measurement of the outlet gas confirmed that water generated by the chemical reaction accumulated in the cell, rather vaporization and discharge to the outlet. Thus, the role of the humidifier in the fuel cell system was minimized.

Hollow plasma structure during the breakdown phase of nanosecond pulsed pin–pin discharges generated with overvoltage

Atmospheric pressure nanosecond repetitive pulsed discharges are of interest for applications in combustion, material processing, plasma medicine and gas treatment. In this paper the observation of a hollow structure at the ignition stage of such discharge in a pin–pin geometry is reported. Plasma images show that the phenomenon occurs in a variety of gases (helium, humid helium, argon and air) suggesting that it is in first approximation non-species specific. The phenomenon is investigated in detail in pure helium discharges for peak applied voltages between 3 and 6 kV and 200 ns voltage pulse duration by performing time-resolved optical emission spectroscopy measurements of electron density, gas temperature and electric field. All the measurements were performed at the mid-gap during the early stages of the discharge, near the breakdown. The transition from a homogeneous filament to a hollow structure occurs between 4 and 5 kV in helium. Electron density measurements by Stark broadening of the He I line at 492.2 nm show no significant difference in electron densities for the applied voltage between 3 and 6 kV. In all cases, a maximum electron density of about 3.5 × 1021 m−3 was found. Electric field measurements performed by Stark polarization spectroscopy of the He I transition at 492.2 nm and of its forbidden counterpart show electric field strengths higher than the DC breakdown field of helium at atmospheric pressure consistent with the generation of the discharges with overvoltage. Moreover, a correlation between electric field values and the appearance of the hollow structure is observed and, remarkably, the phenomenon is not sensitive to the pre-ionization level (memory effect). Possible mechanisms for the phenomenon are discussed.

HCN-to-HNC intensity ratio: a new chemical thermometer for the molecular ISM

Context. The gas kinetic temperature (TK) determines the physical and chemical evolution of the interstellar medium (ISM). However, obtaining reliable TK estimates usually requires expensive observations including the combination of multi-line analysis and dedicated radiative transfer calculations. Aims. This work explores the use of HCN and HNC observations, and particularly the I(HCN)-to-I(HNC) intensity ratio (I(HCN)/I(HNC)) of their J = 1–0 lines, as direct probe of the gas kinetic temperature in the molecular ISM. Methods. We obtained a new set of large-scale observations of the HCN and HNC (1–0) lines throughout the Integral Shape Filament (ISF) in Orion. In combination with ancillary gas and dust temperature measurements, we find a systematic temperature dependence of the observed I(HCN)-to-I(HNC) intensity ratio throughout our maps. Additional comparisons with chemical models demonstrate that these observed I(HCN)/I(HNC) variations are driven by the effective destruction and isomerization mechanisms of HNC under low-energy barriers. Results. The observed variations of I(HCN)/I(HNC) with TK can be described with a two-part linear function. This empirical calibration is then used to create a temperature map of the entire ISF. Comparisons with similar dust temperature measurements in this cloud, as well as in other regions and galactic surveys, validate this simple technique for obtaining direct estimates of the gas kinetic temperature in a wide range of physical conditions and scales with an optimal working range between 15 K ≲ TK ≤ 40 K. Conclusions. Both observations and models demonstrate the strong sensitivity of the I(HCN)/I(HNC) ratio to the gas kinetic temperature. Since these lines are easily obtained in observations of local and extragalactic sources, our results highlight the potential use of this observable as new chemical thermometer for the ISM.

Performance of anodic recirculation by a variable flow ejector for a solid oxide fuel cell system under partial loads

An anode gas recycle (AGR) system driven by a variable flow rate ejector was developed for use in small-scale solid oxide fuel cell (SOFC) systems. The partial load conditions were simulated through recycling power generation experiments to clarify the fundamental characteristics of the variable flow ejector by using actual 1 kW-class SOFC equipment at the steady state. We achieved power generation in a range of recirculation ratios under partial load conditions of 62.5%–80% by controlling the recirculation characteristics with the developed ejector by using a needle. Results showed that the recirculation ratio can be controlled in the range of 0.595–0.694 by adjusting the driving energy with the ejector even at a partial load where the fuel gas flow rate of the ejector changes. Furthermore, the effect of the recirculation ratio on SOFC output was discussed based on the results of gas analyses and temperature measurements. As the recirculation ratio increased, the fuel concentration at the SOFC inlet decreased and the water vapor concentration increased. However, the effect of the recirculation ratio on the stack temperature and output power was proposed to be small. In addition, it was confirmed that the operation was performed under safe conditions where no carbon deposition occurred by circulating the steam generated inside the SOFC without an external water supply. Ejector characteristics during power generation experiments were lower than those at room temperature, which indicates that an ejector upstream pressure of approximately 20–170 kPa gauge pressure was required. Variations in the fluid properties of the driver gas in the ejector motive nozzle heated by the hot suction gas were found to degrade the performance of the ejector installed in the SOFC system, as compared with the results of simulation experiments at room temperature. Nevertheless, the recirculation ratio range required for operation could be satisfied by adjusting the flow velocity of the driving gas through needle control.

Experimental investigation of ionization front propagating in a 28 GHz gyrotron beam: Observation of plasma structure and spectroscopic measurement of gas temperature

Atmospheric millimeter-wave discharge was investigated experimentally using a 28 GHz gyrotron. The propagation velocity of an ionization front, plasma structure, and vibrational and rotational temperatures of nitrogen molecules were measured at a beam intensity lower than 1.0 GW/m2, which is below the breakdown threshold. Results show that the propagation velocity of an ionization front increased monotonically with beam intensity and decreased with ambient pressure. In addition, four typical plasma structures having different space occupancies were observed. Furthermore, at any beam intensity below 0.5 GW/m2, the vibrational temperature was found to be saturated at about 6000 K. The corresponding electron number density is almost equal to the cut-off density. Finally, it was suggested that the propagation velocity depends on the plasma space occupancy.

Experimental combustion characteristics and NOx emissions at 50% of the full load for a 600-MWe utility boiler: Effects of the coal feed rate for various mills

For realizing higher boiler efficiency and lower NOx emissions at a half load of a 600-MWe utility boiler, a novel approach is proposed for various coal feed rates. In this study, at 50% of the full load, industrial-size experiments were conducted at various coal feed rates with measurements of local gas temperatures and species concentrations (in the burner region and near-wall region, respectively), the carbon content of the fly ash, the carbon content of the slag, and the NOx emissions. The pulverized-coal ignition positions of two burners at low loads were at 0.2–0.3 m from the burner nozzle outlet; hence, satisfactory ignition performance was realized. At larger coal feed rates of mill A, both the ignition performance and the NO reduction performance improved. The unburnt carbon in the fly ash decreased monotonically and the carbon in the slag increased monotonically, with settings from 50%:50%–36%:64% (namely, changing the coal-feed rate pair of the middle and bottom mills from 50%:50%–43%:57%–36%:64%).

Identification of wavelength regions for non-contact temperature measurement of combustion gases at high temperatures and high pressures

Stationary gas turbines are still an important part of today’s power supply. With increasing temperature of the hot combustion gas inside a gas turbine, the efficiency factor of the turbine increases. For this reason, it is intended to operate turbines at the highest possible gas temperature. Therefore, in the combustion chamber and especially at the position of the first stage guide vanes the gas temperature needs to be measured reliably. To determine the gas temperature, one promising approach is the application of a non-contact measurement method using a radiation thermometer. A radiation thermometer can measure the gas temperature remotely from outside of the harsh environment. At ZAE Bayern, a high temperature and high-pressure gas cell has been developed for this purpose in order to investigate gases and gas mixtures under defined conditions at high pressures and high temperatures. This gas cell can be placed in a FTIR-spectrometer in order to characterize the infrared-optical properties of the gases. In this work the measurement setup is introduced and gas mixtures, which are relevant for gas turbine applications are analyzed thoroughly. The derived results are presented and discussed in detail. To identify suitable wavelength regions for non-contact gas temperature measurements, first tests have been performed. Based on these tests, an appropriate wavelength region could be chosen, where future gas temperature measurements can be carried out.

Monitoring the Moisture Content in Pharmaceutical Batch Fluidized Bed Dryers Using Observer-Based Soft Sensors

Tablet manufacturing in the pharmaceutical industry involves batch fluidized bed drying for particle moisture removal. This paper introduces five approaches for moisture content monitoring, relying either on a complex phenomenological model or its simplified version. The first two soft sensors consist of open-loop estimators, i.e. they simply simulate the models fed by the manipulated variables. Three closed-loop moving horizon estimators based on the simplified model are also proposed for improved robustness. In the first one, the measurements of the inlet gas and particle temperatures feed back the soft sensor. The last two closed-loop observers additionally can take into account infrequent delayed moisture content measurements, such as at-line loss on drying analysis. A validation of the soft sensors is performed with experimental data collected on a pilot scale fluidized bed dryer. Results show that the closed-loop observer with the delayed moisture content measurements still has an accuracy that is equivalent (and sometimes better) than the complex phenomenological model.

Simulation and experimental study of diesel engine emission temperature based on tunable diode laser absorption spectroscopy

Based on the temperature measurement technology of tunable diode laser ab-sorption spectroscopy, the simulation and experimental research on the temperature measurement of CO2 gas emitted by D4114B Diesel engine is realized. The light source model, gas chamber model and data detection model were established by using SIMULINK, which is more general numerical simulation tool in MATLAB. Under the simulated Diesel engine emission environment, the measured CO2 gas temperature was obtained by model simulation and analyzed. The simulation relative error was 0.077%. The marine D4114B Diesel engine was used as the test object, the visual window was reconstructed on the exhaust light path, and an optical path test system was established. The tunable diode laser was used as the detection light source to carry out on-line test research on the CO2 gas temperature in the exhaust gas emission. The relative error was 4.4%. The results show that the model built by SIMULINK can reflect the actual laser modulation effect and CO2 gas absorption. The simulation results have certain reference value for the research of tunable diode laser absorption spectroscopy temperature measurement system.

Gas temperature measurement of high-pressure turbine rotor blades during bench tests of a core engine

Gas temperature measurement of high-pressure turbine rotor blades during bench tests of a core engine

Design and analysis of gas temperature measurement module in motor vehicle exhaust online measurement system

The mass flow rate of vehicle exhaust significantly influences the measurement of the exhaust pollutants emission factors, meanwhile the exhaust gas temperature measurement is most important in the measurement of exhaust gas mass flow. In order to measure the temperature of exhaust gas accurately and sensitively, a motor vehicle exhaust online measurement experimental system has been developed. The article reports on the design and analysis of gas temperature measurement module in this system. The gas temperature measurement consists of a high-precision K-type thermocouple and a weak signal amplifier circuit. The K-type thermocouple was used to measure the temperature of exhaust gas. Based on the AD595AQ, which was a complete instrumentation amplifier chip with a cold junction compensator for thermocouple, the weak signal of thermocouple was amplified to achieve accurate and rapid measurement of exhaust gas temperature. The real experimental results showed that the detection time is 0.5 s, the deviation is + 0.2°C, and the detection limit is 573°C. The subsequent analysis showed that the gas temperature measurement module performed well to support the system.

Time-resolved fire heat release rate under a ceiling based on ceiling layer measurements

Measurement of time-resolved fire heat release rate (HRR) is important to characterize fire growth and suppression. Under certain conditions, such as large fire tests conducted under a ceiling with sprinkler protection, quantification of a time-resolved HRR is still a challenging problem. This work attempts to develop a new methodology of estimating convective and chemical HRRs for a fire under a ceiling. The instantaneous measurements of gas temperature, velocity and species concentration in the ceiling layer are used to calculate the HRRs. To verify the proposed method, two heptane pan fire tests were conducted under a ceiling and the chemical HRR was calculated from the fuel mass loss data. The results demonstrate that the proposed method can provide a time-resolved chemical HRR that is comparable to that obtained from the fuel mass loss rate. The fraction of convective HRR to chemical HRR also agrees well with the test data obtained under a calorimeter. The application to rack-storage fires under a ceiling with sprinkler suppression shows that the proposed method can provide the fire growth in the free-burn period and consistent trends for the fire development with water application.

Gas temperature and boundary layer thickness measurements of an inert mixture using filtered broadband natural species emission (Part I)

A new experimental methodology to simultaneously measure gas temperature and boundary layer thickness was developed and explained for the first time in this work. The new methodology is based on the line-of-sight broadband filtered natural infrared emission of species and it solves one of the main challenges of using the broadband spectroscopy to measure gas temperatures: quantification of the absorption of the core gas infrared emission due to the cold boundary layer on the optical access of combustion systems. To evaluate and validate the new methodology, it was applied to measure the gas temperature and boundary layer thickness of a mixture of methane, carbon dioxide, and nitrogen using Rapid Compression Machine RCM). High-speed infrared cameras with two filters at wavelength ranges of 3.329 to 3.629 μm and 4.069 to 4.445 μm were used to measure the filtered natural emission of methane and carbon dioxide during the post-compression period. Measured gas temperatures at two conditions were compared with the modeled temperature calculated using the isentropic compression equation. Excellent agreement, within 1%, was reached between modeled and measured gas temperatures.

Gas temperature and boundary layer thickness measurements of an inert mixture using filtered broadband natural emission of species at Rapid Compression Machine conditions (Part II)

Our understanding of the combustion process is hindered by the boundary layer at the optical access. To be detected by the camera, the infrared emission of the mixture (or the laser) should pass the boundary layer at the window of the combustion system. Regardless of the type of experimental techniques used (either the laser or natural emission of the species), part of the emission could be absorbed by the boundary layer due to its low temperature. Hence, the measured data includes some uncertainty and errors due to the boundary-layer absorption and its thickness (it reduces the optical length), which have not yet been quantified due to the unavailability of the boundary layer thickness, especially during a transient process such as engine compression stroke.A new methodology was used to measure the gas mixture temperature and boundary layer thickness using the Rapid Compression Machine (RCM). The methodology is based on filtering and measuring the infrared natural emission of the species at two different band-pass wavelength ranges. The new methodology was applied to measure the gas temperature and boundary layer thickness by measuring the filtered infrared emission of methane, carbon monoxide and carbon dioxide at two compressed gas pressures and two compressed gas temperatures in this work. The measured and modeled gas temperatures were compared during the post compression. An excellent agreement within 1% between the measured and modeled gas temperatures were reached at all of the studied conditions.

CABARET scheme for modelling the stratification erosion in gas mixtures in hydrogen mitigation experiments for reactor safety

Experiments on atmosphere mixing and stratification in the large scale experimental facility (PANDA), where the initial helium stratification in a vessel is eroded by a vertical jet of steam, were simulated with the CABARET scheme. Good agreement between calculated and measured gas temperature and concentrations has been achieved by refining the mesh and adding the model of radiative heat transfer. The simulation results are presented and discussed.

Mathematical modelling of hydrogen safety problems with CABARET scheme

Experiments on overall fluid transfer and mixing in the large scale experimental facility (PANDA), where the initial helium-rich layer is eroded by a flow resulting from the interaction of a jet/plume with horizontal flow obstruction, were simulated with the CABARET scheme. Computational simulation results are provided for two mesh resolutions and are compared with the experimental data. Good agreement between calculated and measured gas temperature and the breakup of the helium layer dynamics was achieved by refining the mesh in the jet area and by adding the model of radiation heat transfer.

Temperature distribution of gas flows in a grid area activated by chemical vapor deposition

The scheme of gas temperature measurements in flows of rarefied precursor gases by HW CVD was elaborated. The gas flow temperature of air, argon and hexafluoropropylene oxide was measured at different mass flow rates. The presence of a large well-heated area in gas flows forward the activator was discovered. Asymmetric heating of the gas flow in areas above and under an activator was observed. Cooling of gas flows by increase in the precursor gas mass flow rate was confirmed. The parameters, optimal for the formation of the area with uniform temperature flows above the surface of substrate holder, were determined.

Gas and Dust Temperature in Prestellar Cores Revisited: New Limits on Cosmic-Ray Ionization Rate

Abstract We develop a self-consistent model for the equilibrium gas temperature and size-dependent dust temperature in cold, dense, prestellar cores, assuming an arbitrary power-law size distribution of dust grains. Compact analytical expressions applicable to a broad range of physical parameters are derived and compared with predictions of the commonly used standard model. It is suggested that combining the theoretical results with observations should allow us to constrain the degree of dust evolution and the cosmic-ray ionization rate in dense cores, and to help with discriminating between different regimes of cosmic-ray transport in molecular clouds. In particular, assuming a canonical MRN distribution of grain sizes, our theory demonstrates that the gas-temperature measurements in the prestellar core L1544 are consistent with an ionization rate as high as ∼10−16 s−1, an order of magnitude higher than previously thought.

Simultaneous measurements of fuel concentration and temperature in gas jets by laser induced breakdown spectroscopy

Laser induced breakdown spectroscopy (LIBS) enables quantitative measurements of the equivalence ratio in flames, spray and gas jets. Although there are always considerable temperature differences between the calibrations and the LIBS measurements in flames and fuel jets, the temperature effects on LIBS were rarely mentioned and not corrected in the previous LIBS measurements. In this study, a novel method to simultaneously measure the equivalence ratio and the gas temperature by LIBS in a single laser shot is proposed. This method can correct the temperature effects based on the linear correlation between the peak intensity ratio (PIR) of atomic lines and the gas temperature. The PIR of H656/N746 and the full width at half maximum (FWHM) of H656 are employed to establish calibration curves with the equivalence ratio and the gas temperature, respectively, and both of calibrations show high coefficients of determination (R2). Then, the measurement accuracy and precision of the proposed method are discussed in detail. The total uncertainties in measurements of equivalence ratio and gas temperature are estimated by 5.6% and 5.8%, respectively. Finally, the simultaneous measurements of equivalence ratios and gas temperatures in methane jets at different positions and at different injection pressures are conducted. The comparison of equivalence ratios before and after correction of the temperature effects indicates that the accuracy of the fuel concentration measurements by LIBS would be remarkably degraded if the temperature variations were neglected.

Cross-band infrared laser absorption of carbon monoxide for thermometry and species sensing in high-pressure rocket flows

A novel cross-band laser absorption spectroscopy technique has been developed for quantitative measurements of gas temperature and carbon monoxide (CO) in high-pressure, high-temperature rocket combustion flows. The strategy enables a broad range of sensor operability by simultaneously probing rovibrational transitions in both the fundamental and first overtone bands of CO near $$4.98\,\upmu \hbox {m}$$ and $$2.32\,\upmu \hbox {m}$$, respectively, which sustain large differences in temperature dependence despite collisional broadening. Scanned-wavelength modulation spectroscopy methods are integrated for noise rejection in the harsh rocket operating environment. Initial experiments using the cross-band thermometry technique have been conducted on a single-element-injector rocket combustor with RP-2/GOx and $${\hbox {CH}_4}/\hbox {GOx}$$ propellant combinations at pressures up to 75 bar. Measurements of the first overtone bandhead ($$2.32\,\upmu \hbox {m}$$) maintained adequate signal-to-noise at even higher pressures (up to 105 bar), although deviating significantly from spectral simulations. To account for collisional effects at high gas densities, empirical models for line mixing, developed via shock tube studies, were employed to enable quantitative interpretation of measured signals for temperature and CO mole fraction in the rocket combustor.