High-temperature Gas Environment Research Articles

Chondrules as direct thermochemical sensors of solar protoplanetary disk gas.

Chondrules, millimeter-sized igneous spherules comprising the major component of most chondritic meteorites, formed during the first 4 million to 5 million years of the evolution of the solar protoplanetary disk and, therefore, can potentially offer important constraints on the conditions in the disk, provided that the processes that led to their formation can be understood. High-resolution cathodoluminescence (CL) survey of chondrules from various chondrite groups revealed changes of CL activator concentrations of magnesium-rich olivines. We show that these overlooked internal zoning structures provide evidence for high-temperature gas-assisted near-equilibrium epitaxial growth of olivines during chondrule formation. We argue that this interaction with the surrounding gas, rather than various cooling histories, defined chondrule composition and texture. Chondrules are thus direct thermochemical sensors of their high-temperature gaseous environment, and high partial pressures of gaseous Mg and SiO are required in their solar protoplanetary disk-forming region to maintain olivine saturation in chondrules. The inferred crystallization of olivines, from stable melts approaching equilibrium with the surrounding gas, provides an explanation for the notable absence of large and systematic isotopic fractionations in chondrules.

Corrosion-resistant systems of formate packer fluid for G3/N80/TP110SS pipes at high temperature, high pressure and high H2S/CO2 ratios.

A series of corrosion problems caused by high-temperature, high-pressure and high-acid gas environments has been an issue in oil and gas production for a long time. During the development of a high-acid gas field, the petroleum pipe is subjected to many aspects of corrosion, and the corrosion mechanism is complicated by the condition of the coexistence of H2S/CO2. Based on the study of the corrosion problem associated with the formate packer fluid in Southwest China, three kinds of steels were studied for corrosion prevention in the alloy G3/N80 steel/TP110SS steel. The study shows that the corrosion rate of the formate packer fluid is low, but corrosion is severe in environments characterized by high temperatures, high pressures and high-acid gas contents. Based on the consideration of cost and the difficulty of realization, an anti-corrosion system was constructed based on the existing packer fluid, mainly through the introduction of a variety of anti-corrosion additives. Through the selection of various additives and corrosion experiments, a corrosion protection system of formate packer fluid was developed. Corrosion tests show that the corrosion rate of the system must be less than 0.076 mm yr−1 to achieve the purpose of corrosion protection. The formate packer fluid with corrosion protection can meet the needs of the current application.

Methods of Accelerated Tests of Turbine Blades in Power Plants Operated under Multicomponent Loading Conditions

The article presents a method of accelerated tests (ATs) of turbine blades in gas turbine power plants (GTPPs) (aircraft gas turbine engines, gas turbine drives of compressors and electric generators, etc.). It is known that the reliability and service life of GTPPs are mainly determined by the elements of the hot section (the moving blades and nozzle vanes, turbine disks), they are exposed to multicycle loads, repeated static (low-cycle) loads and long-term static loads, as well as to a high temperature gas environment. Gas corrosion is one of the serious types of blade damage which causes a decrease in reliability and efficiency of turbines in GTPPs. The existing methods of ATs of turbine blades which are performed on individual test benches do not reproduce a complete picture of their damage rate, while the ATs of GTPPs reproduce the damage rate of blades caused only by multicycle loads, low-cycle loads and long-term static loads, but they do not reproduce the damage rate caused by the gas environment due to an insignificant duration (as compared to the service life) of the exposure of a blade to a gas environment. Two options of performing blade ATs are examined. The first option consists in testing a blade separately from the GTPP. The blade is subjected to block loading which consists of individual blocks. Each block reproduces in a successive order the damage rate caused by multicycle loads, low-cycle loads and long-term static loads and the damage rate caused by the gas environment. The second option consists in ATs of a GTPP fitted with blades which have already become outdated in terms of corrosion damage rate. The examined methods of blade ATs enable to increase the reliability of the integrated assessment of the robustness of GTPP blades operated under multicomponent loading conditions.

Mid-infrared laser absorption spectroscopy of NO2 at elevated temperatures

A mid-infrared quantum cascade laser absorption sensor was developed for in-situ detection of NO2 in high-temperature gas environments. A cluster of spin-split transitions near 1599.9cm−1 from the ν3 absorption band of NO2 was selected due to the strength of these transitions and the low spectral interference from water vapor within this region. Temperature- and species-dependent collisional broadening parameters of ten neighboring NO2 transitions with Ar, O2, N2, CO2 and H2O were measured and reported. The spectral model was validated through comparisons with direct absorption spectroscopy measurements of NO2 seeded in various bath gases. The performance of the scanned wavelength modulation spectroscopy (WMS)-based sensor was demonstrated in a combustion exhaust stream seeded with varying flow rates of NO2, achieving reliable detection of 1.45 and 1.6ppm NO2 by mole at 600K and 800K, respectively, with a measurement uncertainty of ±11%. 2σ noise levels of 360ppb and 760ppb were observed at 600K and 800K, respectively, in an absorption path length of 1.79m.

Aerodynamic breakup of an n-decane droplet in a high temperature gas environment

The aerodynamic droplet breakup under the influence of heating and evaporation is studied numerically by solving the Navier-Stokes, energy and transport of species conservation equations; the VOF methodology is utilized in order to capture the liquid-air interphase. The conditions examined refer to an n-decane droplet with Weber numbers in the range 15–90 and gas phase temperatures in the range 600–1000K at atmospheric pressure. To assess the effect of heating, the same cases are also examined under isothermal conditions and assuming constant physical properties of the liquid and surrounding air. Under non-isothermal conditions, the surface tension coefficient decreases due to the droplet heat-up and promotes breakup. This is more evident for the cases of lower Weber number and higher gas phase temperature. The present results are also compared against previously published ones for a more volatile n-heptane droplet and reveal that fuels with a lower volatility are more prone to breakup. A 0-D model accounting for the temporal variation of the heat/mass transfer numbers is proposed, able to predict with sufficient accuracy the thermal behavior of the deformed droplet.

Numerical investigation of aerodynamic droplet breakup in a high temperature gas environment

The Navier–Stokes equations, energy and vapor transport equations coupled with the VOF methodology and a vaporization rate model are numerically solved to predict aerodynamic droplet breakup in a high temperature gas environment. The numerical model accounts for variable properties and uses an adaptive local grid refinement technique on the gas–liquid interface to enhance the accuracy of the computations. The parameters examined include Weber (We) numbers in the range 15–90 and gas phase temperatures in the range 400–1000K for a volatile n-heptane droplet. Initially isothermal flow conditions are examined in order to assess the effect of Weber (We) and Reynolds (Re) number. The latter was altered by varying the gas phase properties in the aforementioned temperature range. It is verified that the We number is the controlling parameter, while the Re number affects the droplet breakup at low We number conditions. The inclusion of droplet heating and evaporation mechanisms has revealed that heating effects have generally a small impact on the phenomenon due to its short duration except for low We number cases. Droplet deformation enhances heat transfer and droplet evaporation. An improved 0-D model is proposed, able to predict the droplet heating and vaporization of highly deformed droplets.

Evaporation and Vapor Formation of Graphite Suspensions Based on Water in a High-Temperature Gas Environment: an Experimental Investigation

We performed an experimental research on evaporation and vapor formation of water droplets containing large (2 mm in size) and small (0.05 mm and 0.2 mm in diameter) graphite inclusions, when heated in a high-temperature gas environment. We applied a high-speed (up to 104 fps) video recording to establish mechanisms of the processes considered. Moreover, we revealed the positive influence of addition of small graphite inclusions on intensifying the evaporation of heterogeneous suspension droplets. In addition, we made the assumption on the formation of vapor layer around the 10 and 15 μl suspension droplets, as well as its negative influence on the lifetimes of suspension droplets τh (increasing the times) in a high-temperature gas environment.

Evaporation Features of Water Droplets with Typical Subsoil Impurities During the Motion Through High-Temperature Gas Environment: Research Experience at Tomsk Polytechnic University

This paper investigates experimentally the evaporation rate of water droplets with typical subsoil impurities (clay, silt, soil, sand) during the motion through high-temperature gas environment. The experiments were conducted at Tomsk Polytechnic University using high-speed video recording and modern video processing methods. Here, we analyze the influence of the impurity concentration on the intensity of heating and phase changes. The present study defines, how the preheating of impurities affects the completeness of the evaporation of water droplets with impurities. As a result, of studies, we draw the conclusion that it is possible to use water from natural reservoirs without prior preparation for wildfires extinguishing.

Analysis of the Water Droplet Evaporation Features with a Solid Nontransparent Inclusion in High-Temperature Gas Environment as a Part of University Research Work

This paper examines the features of the heating and evaporation of heterogeneous liquid (water) droplets (with the initial radius from 1.5 to 2.5mm) in the combustion products of typical liquid combustible substances (acetone, technical ethanol, butane-propane gas mixture) and heated air explored as a part of university research work. The investigations have been performed by means of high-speed video recording and software “TEMA Automotive” and “Phantom Camera Control”. The gas temperature varied from 300 to 850K in the experiments. The characteristic times of droplet existence (complete evaporation) have been determined. The influence of radiative, convective and conductive heat transfer has been defined.

Conditions of Intensive Evaporation of Heterogeneous Water Droplet in High Temperature Gas Environment

AbstractThe results of a numerical simulation of heat and mass transfer during evaporation of a water droplet with solid inclusion in air at temperature as high as 1000K are presented. Typical heating steps of droplet until it reaches the conditions of intensive evaporation (i.e.the interface “solid inclusion – liquid” reaches the boiling temperature) are described. The roles played by the external air temperature and by the main properties of inclusion are detailed. The droplet size, the relation between the sizes of inclusion and a liquid layer during the heating up is determined. The necessary and sufficient conditions of intensive evaporation in the system “water droplet with solid inclusion in high-temperature air” are pointed out.

Corrosion resistances of alloys in high temperature hydrogen iodide gas environment for sulfur–iodine thermochemical cycle

The hydrogen iodide (HI) decomposition process is a limiting step for the efficiency of the sulfur–iodine nuclear hydrogen production process, owing to its low kinetics and complicated reaction characteristics. Therefore, the Korea Advanced Institute of Science and Technology (KAIST) suggested a simple high-temperature HI decomposition process at 650–700 °C for higher efficiency. For practical application of the high-temperature HI decomposition process, along with the catalyst study, we performed structure material selection and corrosion resistance tests. A number of candidate alloys were considered in various aspects and exposed to the high-temperature HI gas environment, which is extremely corrosive, at 850 °C for 100 h. Nine alloys with different nickel and iron compositions have been tested and analyzed. Test results indicated the degrees of resistances to corrosion of each alloy, on the basis of weight change and cross-sectional micrographs. Thus, because of their resistance to internal oxidation and formation of stable external oxide layers, five types of alloys, Haynes 214, aluminizing and inter-diffusion heat-treated or electron beam surface-treated Alloy 617 are suggested as appropriate candidates for fabricating high-temperature HI decomposer. In particular, surface-treatment of Alloy 617 gave it a high stability because of the resultant formation of an Al-rich layer; this was confirmed by experimental results, so IDHT Alloy 617 is recommended as a suitable structural material for fabricating HI decomposer. However, further long-term testing is suggested to ensure safety and confirm applicability.

Mechanism of killing of spores of Bacillus anthracis in a high-temperature gas environment, and analysis of DNA damage generated by various decontamination treatments of spores of Bacillus anthracis ,Bacillus subtilis and Bacillus thuringiensis

To determine how hydrated Bacillus anthracis spores are killed in a high-temperature gas environment (HTGE), and how spores of several Bacillus species including B. anthracis are killed by UV radiation, dry heat, wet heat and desiccation. Hydrated B. anthracis spores were HTGE treated at c. 220°C for 50 ms, and the treated spores were tested for germination, mutagenesis, rupture and loss of dipicolinic acid. Spores of this and other Bacillus species were also examined for mutagenesis by UV, wet and dry heat and desiccation. There was no rupture of HTGE-treated B. anthracis spores killed 90-99·9%, no mutagenesis, and release of DPA and loss of germination were much slower than spore killing. However, killing of spores of B. anthracis, Bacillus thuringiensis and Bacillus subtilis by UV radiation or dry heat, but not wet heat in water or ethanol, was accompanied by mutagenesis. It appears likely that HTGE treatment kills B. anthracis spores by damage to spore core proteins. In addition, various killing regimens inactivate spores of a number of Bacillus species by the same mechanisms. This work indicates how hydrated spores treated in a HTGE such as might be used to destroy biological warfare agent stocks are killed. The work also indicates that mechanisms whereby different agents kill spores are similar with spores of different Bacillus species.

Corrosion of Alloy 617 in high-temperature gas environments

High-temperature gas-cooled reactors (HTGRs) with helium gas as the primary coolant have been considered as one type of the Generation IV nuclear power reactor systems. Several nickel-based superalloys, including Alloy 617, are potential structural materials to serve as pressure boundary components, such as the intermediate heat exchanger (IHX) in an HTGR. Impurities in a helium coolant, such as H2O and O2, can interact with structural materials at working temperatures of >900°C, leading to serious degradation on these materials. In addition, defects in IHX surface coatings would allow these species to reach and interact with the external surfaces of these components, leading to similar or even more serious degradation. In this study we investigated the oxidation behavior of Alloy 617 in high-temperature, gaseous environments with various levels of O2 and H2O. A series of general corrosion tests were conducted at test temperatures of 650°C, 750°C, 850°C and 950°C under various coolant compositions of dry air, 1% O2, 10% relative humidity (RH), and 50% RH. Preliminary results showed that the surface morphologies of the Alloy 617 samples exhibited distinct evidence of intergranular corrosion. Compact chromium oxide layers were observed on the sample surfaces. The oxidation mechanisms of this alloy in the designated environments are discussed.

Corrosion of Nickel and Iron Based Superalloys in High Temperature Gas Environments

High-temperature gas-cooled reactors (HTGRs) with helium gas asthe primary coolant have been considered as Generation IV nuclearpower reactor systems. Several iron- and nickel-based superalloys,including Incoloy 800H, Hastelloy X, and Inconel 617, arepotential structural materials in pressure boundary components,such as the intermediate heat exchanger (IHX) in an HTGR.Impurities in a helium coolant, such as H2O and O2, can interactwith structural materials at working temperatures of >900 oC,causing serious degradation. This study investigates the oxidationbehavior of three selected alloys (Hastelloy X, Incoloy 800H, andInconel 617) in high-temperature, gaseous environments withvarious levels of O2 and H2O. A series of corrosion tests wereconducted at test temperatures of 650 oC, 750 oC, 850 oC and 950oC under various coolant compositions of dry air, 1% O2, 10%humidity, and 50% humidity.

Analysis of Fractal-Like Spore Aggregates in Direct Simulation Monte Carlo

DOI: 10.2514/1.T3824 The work presented in this paper is a continuation of the authors’ previous efforts to develop a realistic bioengineering model for predicting the survivability of anthrax spores subjected to a high-temperature gas environment. One of the major mechanisms of deactivating spores is to expose them to elevated temperatures, and careful, exposure-tube experiments have been carried out to ascertain the deactivation mechanism. Spores typically exist in nature as aggregates, but simulating the heat transfer to clumps of spores is difficult because of the highly irregular geometry of spore clumps. In this work, the tunable particle-cluster and cluster-cluster algorithms are implemented to generate fractal-like spore aggregates. The algorithm output as a function of algorithm parameter input is compared with a typical spore-clump image. Because the spore aggregate size is small and is on the order of the mean free path even at atmospheric conditions, the direct simulation Monte Carlo method is used to model the heat transfer to each of the spores in the aggregate. The shielding effect of aggregate spores on a single spore in the clump is studied, revealing that, for aggregates on the order of 100, the shielding effect is about 25% 45% compared with a single, isolated spore.

Corrosion Resistance of SOFC and SOEC Glass-Ceramic Seal Materials in High Temperature Steam/Hydrogen

There exists concern that glass-ceramic seal materials may not tolerate the high temperature gaseous environment in solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) applications, potentially leading to the poisoning of electrodes by silica and ultimate loss of hermeticity. A mechanism for the loss of silicon from glass seals has been proposed by other workers. To address this concern, material samples of proprietary glass-ceramics were exposed to steam/hydrogen atmospheres at 800 °C for up to 1000 h. The mass losses of the samples were measured at intervals and their changes in surface chemistry were analyzed using techniques such as X-ray photoelectron spectroscopy and dynamic secondary ion mass spectroscopy. It was shown that the extent of corrosion depends on composition and surface microstructure and that some glass-ceramics are particularly resistant to steam/hydrogen corrosion.

Corrosion of Nickel and Iron Based Superalloys in High Temperature Gas Environments

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Thermo-structural studies of spores subjected to high temperature gas environments

One of the major mechanisms of deactivating spores is to expose them to elevated temperatures. Experiments carried out in an exposure tube to study the effects on spores in a high temperature gas environment provide evidence of spore deactivation, although the deactivation mechanism is not clear. Numerical studies have been performed to complement the experimental work and to study the effects of various parameters, such as gas temperature, exposure time, and internal pressure on spore survivability. The laminar and turbulent flow fields of a sudden expansion inside the thermal exposure system were simulated by computational fluid dynamics. A thermo-structural model with wall porosity was developed to take into account the dynamic response of the spore wall structure to the internal pressure exerted by the heated vapor on the spore wall. Finally, the results of the transient heat transfer and the thermo-structural models are discussed in the context of the uncertainties in biological system parameters and spore survivability.

Thermal Protection System Crack Growth Simulation Using Advanced Grid Morphing Techniques

An extension of previous [Titov, E., Zhong, J., Levin, D., and Picetti, D., Simulation of RCC Crack Growth Due to Carbon in High-Temperature Gas Environments, Journal of Thermophysics and Heat Transfer, Vol. 23, No. 3, July-Sept. 2009, pp. 489-501.] modeling of crack damage growth in reinforced carbon-carbon specimens is presented in this work. The specimens were studied in an arcjet and represented a portion of the space shuttle wing [Lewis, R., Quick Look Report, Atmospheric Reentry Materials and Structures, 2004.] and a high-velocity meteoroid impact [Curry, D. M., Pham, V. T., Norman, I., and Chao, D. C., Oxidation of Reinforced Carbon-Carbon Subjected to Hypervelocity Impact, NASA TP 2000-209760, March 2000.]. The test geometry and flow conditions rendered the flow regime as transitional to continuum; therefore, a Navier-Stokes-based gas-dynamic approach with the temperature jump and velocity slip correction to the boundary conditions was used. The modeled mechanism for wall material loss was atomic oxygen reaction with the bare, exposed carbon surface. The purpose of this work is to improve the predictive modeling of crack growth damage assessment by developing procedures that use coupled, advanced topology-based surface and grid-meshing tools. A recessing three-dimensional surface morphing procedure was developed and tested by comparison with arcjet experimental results. A multiblock structured adaptive meshing was used to model the computational domain changes due to the wall recession. This approach made it possible to model full three-dimensional crack growth scenarios as well as to include the presence of realistic reinforced carbon-carbon material features such as delamination, both of which affect damage growth because they enable higher atomic oxygen penetration. Comparison with the arcjet data show that the inclusion of these two factors further improves the comparison between modeling and data. The predicted channel growth and shape change were found to agree with arcjet observations, and local gas flowfield results were found to affect the oxidation rate in a manner that cannot be predicted by previous mass loss correlations. The method holds promise for future modeling of materials gas-dynamic interactions for hypersonic flight.

Field Test of High-Temperature Corrosion Sensors in a Waste-to-Energy Plant

Abstract Electrochemical probes originally designed for use in aqueous environments were shown to measure corrosion rates in a high-temperature gaseous environment where electrolyte consisted of conductive ashes and liquid slag. The field trial of the probes was conducted over a five-month period to monitor fireside corrosion in a waste-to-energy (WTE) plant. The three-electrode air-cooled corrosion sensors, each including a thermocouple to monitor sensor temperature, were installed in four different ports at approximately the same level of the WTE boiler. A total of 12 sensors were tested: six with electrodes using the carbon steel boiler tube material and six using the nickel-chromium alloy used for weld overlays for the electrodes. Corrosion rates and temperatures of the sensors were monitored continuously throughout the trial. Metallographic measurements of sensor thickness loss were used to calibrate the electrochemical corrosion rates. Air cooling of the sensors was found to be necessary to bring th...