High Temperature Gas Research Articles

High-Temperature-Resistant Dual-Scale Ceramic Nanofiber Films toward Improved Air Filtration.

Currently, air pollution primarily arises from industrial emissions, coal combustion, and automobile exhaust, posing significant challenges for mitigation. This highlights the urgent need for advanced and efficient filtration materials with low pressure drop and high-temperature resistance. Traditionally, improving filtration property has involved increasing the thickness of the filtration materials, which consequently leads to higher costs. Here, dual-scale mullite nanofiber (MNF) films containing interwoven thick nanofibers (606 nm) and thin nanofibers (186 nm) are prepared using solution blow spinning. The dual-scale structure design enables the films to maintain a low pressure drop while achieving high filtration efficiency. At an airflow velocity of 5.3 cm s-1, the films with an areal density of 3.8 mg cm-2, achieve a filtration efficiency of 98.23% and a pressure drop of 141 Pa for PM0.3. In addition, the MNF films exhibit excellent flexibility and high-temperature resistance, making them have great potential for use in high-temperature flue gas filtration.

Exploring the benefits of hydrogen-water injection technology in internal combustion engines: A rigorous experimental study

Previous hydrogen researchers have demonstrated the great potential of hydrogen as a zero-carbon fuel and its wider operational ability to directly replace the existing fossil-fuelled internal combustion engines (ICE). Hydrogen direct-injection technology can operate at stoichiometric combustion conditions, fully eliminating the intake backfire phenomena, which has the benefit of low airflow requirements and is a suitable solution for naturally aspirated ICE platforms. However, significant challenges must be addressed when operating an H2 ICE at or near stoichiometric. These include rapid pressure rise rate, high in-cylinder gas pressure and temperature and the consequential higher engine-out NOx emissions. This study provides a comprehensive experimental analysis of the effect of water injection on a light-duty H2 engine’s performance, efficiency, burn durations and NOx emission. The engine was modified to operate with hydrogen via a centrally-mounted direct H2 injector and an intake port-mounted water injection system. The study included water vapour measurements, NOx concentrations and other exhaust gases. The practical implications of these findings are significant. The results demonstrated that the NOx emissions were reduced by 79% when the water was injected at a rate of 5 kg/h at 10 bar IMEP and 2000 rpm. This reduction in emissions, coupled with the observed decrease in cylinder pressure and the rate of pressure rise, could substantially improve engine performance and efficiency. At higher load regions, the water injection extended the maximum engine load to 24 bar IMEP and increased the engine torque output by 10%. The maximum Indicated Thermal Efficiency (ITE) increased from 41% at 16.5 bar IMEP to 42.5% at 18 bar IMEP at a lower lambda, with a corresponding reduction in the intake-air-boost pressure requirement. Of particular note, the use of water injection decreased the engine-out NOx emissions under high-load conditions by more than 55%, even at richer AFR compared to pure hydrogen operation.

Design and performance analysis of a coupled burner for the Solid Oxide Fuel Cell system

The Solid Oxide Fuel Cell (SOFC) system is characterized by high energy conversion efficiency and low emissions. The energy supply and recovery of the SOFC system are facilitated through the ignition burner and the off-gas burner, respectively. This study proposes a coupled design of the ignition burner and the off-gas burner to reduce the burner volume, thereby enhancing the power density of the SOFC system. The ignition burner employs radially opposed jet combustion with fully premixed natural gas, while the off-gas burner uses swirl diffusion combustion with the anode off gas. When the premixed gas and lean anode off gas are unable to sustain the flame, catalytic combustion is initiated. Simulation and experiment methods are utilized to analyze the performance of the coupled burner in this paper. The results indicate that uniform mixing is achieved with a high swirl number (s1 = 2.6) for the premixed gas, and the maximum excess air coefficient for stable flame combustion at 400 °C is 2.47. As the temperature of the cathode off gas increases, the flameout boundary for the premixed gas gradually increases; conversely, with increasing burner power, the flameout boundary gradually decreases. The intersection cooling effect of mixed air and circumferential high-temperature flue gas is effective, and the flame does not exceed the tolerance temperature of the catalytic carrier. The diffusion combustion of anode off gas with a swirl number (s2 = 0.5) exhibits great gas mixing uniformity without a high-temperature core region. When transitioning from flame to catalytic combustion with premixed natural gas and anode off gas, there is a temperature lag of approximately 60 s. The isotropic cylindrical cordierite catalytic carrier with a 400 mesh and a coating of 60 g/ft3 Pt0.1Pd0.5 achieves stable catalytic combustion in an environment with preheated air temperatures ranging from 400 to 600 °C and H2 concentrations of 0.25–2.91 %.

Unusual mineralization in basaltic andesite of submarine volcano Esmeralda (Mariana Island Arc)

The results of studies of a basaltic andesite sample complicated by a mineralized crack and voids, with a crack and gas voids filled with secondary mineralization dredged on the Esmeralda underwater volcano, are presented. A detailed comparative study of the mineral composition of the substance lining the crack, the space around the crack, and the part of basaltic andesite unaffected by secondary changes made it possible for the first time for the underwater Esmeralda volcano to establish the presence of an association of minerals that is not characteristic of unaltered volcanic rocks. In the intracrack space and adjacent zones of basaltic andesite, wide ranges of plagioclase composition were determined, isomorphism in the Fe-Ca-pyroxene series was studied, REE oxides, hydroxides and fluorohydroxides were studied, and variability in the composition of minerals in the magnetite-hematite series was shown. It is assumed that tectonic movements led to the emergence of permeable zones in the previously formed basaltic andesites through which new portions of the melt leaked. In a limited space, high fluid gas saturation, temperature and pressure made it possible to extract metal compounds from the melt and host rocks.

Simulation of a Microwave Plasma Torch Used for Hydrogen Production via Methane Pyrolysis

ABSTRACTHydrogen is often envisioned as a green fuel and energy carrier. However, a greenhouse gas‐free production method is still needed for this purpose. A promising method is the pyrolysis of methane. In this study, we present the three‐dimensional simulation of methane pyrolysis in a microwave plasma torch operated in an argon–methane mixture. Due to the high gas temperatures, the chemistry is dominated by reactions between neutral particles. Therefore, the plasma is treated only as a heat source using space‐resolved gas temperature measurements as input. The end‐of‐pipe results of the simulation are compared to measured values, showing good agreement for methane conversion.

Thermal hydraulic analysis of a high-temperature gas reactor steam generator after loss of feed water accidents

The helical coil steam generator is widely employed in the energy conversion process of high-temperature gas-cooled reactors for its high thermal efficiency in producing superheated steam within the helical tubes. These tubes necessitate materials specifically designed to endure high temperatures, prevent ruptures, and ensure durability under various operational conditions. This study aims to identify the maximum temperatures arising from potential transients in the secondary system and to propose immediate safety measures for minimizing associated risks. The RELAP5/MOD3.4 code was used to simulate the behavior of the next generation nuclear plant steam generator's conceptual design using steady-state conditions. Following the validation of the model, the established steady-state conditions were utilized to simulate accident scenarios, including the feed water line break and the loss of feed water flow to the steam generator. The transient scenarios assumptions include closed flap valves and retained hot helium in the shell side. The simulation tasks were conducted both with and without activating the depressurization system, in order to assess its effect on the temperature of tubes on the wall side. The analysis results indicate that tube wall temperatures can reach 720 °C at the steam generator outlet region and 620 °C at the weld region. The immediate activation of the depressurization system with a controlled relief valve can effectively reduce these temperatures by 239 °C in the steam generator outlet and by 133 °C in the weld region. This also lowers the steam generator's secondary side pressure. As a result, an upgrade and enhancement of operational procedures is straightforward.

Optimizing thermal performance in internal passage cooling with extended rib: Applying response surface method with artificial neural networks

Efficient cooling technology is crucial for high-temperature gas turbines which are significant applications in thermal processes particularly in industries such as power generation aerospace and marine propulsion. Enhancing cooling efficiency in these systems not only improves energy utilization but also plays a critical role in reducing fuel consumption increasing operational reliability and minimizing environmental impacts. This research focuses on optimizing the thermal performance of internal passage cooling channels with extended ribs using a combination of the response surface method and artificial neural networks. By varying the extended rib length and rib width the study aims to enhance heat transfer and minimize flow loss leading to improvements in overall system efficiency. Latin Hypercube Sampling is employed to strategically select variables and automated numerical simulations are conducted to perform a thorough parametric analysis. A steady-state k-ω shear stress transport turbulence model is applied in the simulations and the numerical results are validated against experimental data ensuring accuracy. The combined response surface method–artificial neural network approach integrated with TensorFlow-based modeling allows for the prediction of heat transfer and friction factor ultimately generating a comprehensive response surface to identify the optimal design point. Applying the optimized design leads to a 23.99 % improvement in the thermal performance factor compared to the reference case. The findings of this study highlight a significant enhancement in the thermal performance of the cooling channel structure particularly in high heat flux environments. This research provides valuable insights into the design of more efficient thermal management systems for gas turbines and has broader implications for other high-temperature thermal processes. The proposed optimization methodology offers a reliable approach for improving cooling technologies contributing to the development of the next generation of energy-efficient high-performance gas turbines and other industrial applications where effective thermal management is essential.

High-Temperature Gas and Salt Corrosion of Nickel Alloy

High-Temperature Gas and Salt Corrosion of Nickel Alloy

The corrosion behavior of Al2O3-SiO2 refractory in reducing atmosphere

Hydrogen metallurgy technology is essential for reducing CO2 emissions. Hydrogen (H2) serves as an ideal energy carrier to replace carbon-based fuels, producing only water as a byproduct. Al2O3-SiO2 refractories are commonly used in hydrogen metallurgy technology, including in technologies like HyCROF(Hydrogen-enriched Carbonic oxide Recycling Oxygenate Furnace) and gas heating furnaces. It is important to systematically study their corrosion in high-temperature reducing gas environments. The results indicated that the Al2O3-SiO2 refractory remained stable in pure H2 atmosphere at temperatures below 1200 °C. However, SiO2 and mullite were reduced by H2 when the temperature was increased above 1200 °C. Carbon precipitation was observed in both pure CO atmosphere and H2-CO mixed atmosphere, resulting in an increase weight of the sample. Additionally, the sample developed mullite whiskers after heating treatment at 1200 °C in H2-CO mixed atmosphere. This study aims to clarify the corrosion mechanism of Al2O3-SiO2 refractory in reducing atmosphere and to provide a theoretical basis for the selecting and optimizing refractories for hydrogen metallurgy technology.

Smoke control and temperature distribution of tunnel fires under longitudinal ventilation combined with shaft exhaust

Longitudinal segmental smoke exhaust is often used for fire tunnels longer than 5 km. With the combined effect of longitudinal ventilation in the main tunnel and fan suction in the exhaust shaft, the smoke exhaust path is different from that of a traditional single-tube tunnel. Findings reported in the literature is insufficient to support the rapid development of extra-long road tunnels. In this paper, a numerical model was established by FDS (Fire Dynamics Simulator), and a 1:15 model test platform was built for verification. The effects of different longitudinal velocities, exhaust velocities, bifurcation angles, and exhaust shaft slopes on tunnel fires were analyzed for the longitudinal ventilation combined with shaft exhaust smoke evacuation mode (LVSE). The results show that when the exhaust velocity is greater than 4.5m/s, increasing the exhaust velocity has a limited effect on reducing the smoke length downstream of the exhaust shaft. The bifurcation angle has a significant effect on the velocity distribution in the ventilation shaft and the main tunnel. When the bifurcation angle is less than 45°, the airflow in the main tunnel is more likely to enter the exhaust shaft, and the velocity in the exhaust shaft is more than 5m/s. It is more favorable to reduce the smoke length when the slope of the exhaust shaft is not less than 7%. The high-temperature flue gas collects and forms a vortex near the vent under the LVSE mode, which makes the temperature decay rate slower than that when only longitudinal ventilation is used. The temperature decay model for the LVSE mode is obtained. This study is intended to provide a reference basis for the fire safety design of extra-long road tunnels under the LVSE mode.

Pt-Ta microhotplate with low resistance temperature coefficient and low resistance drift

Micro thermal plates are widely used in various sensors in the aerospace and automotive fields. With the reduction of chip size and the development of MEMS, micro thermal plates are also moving towards integration. The device failure caused by the Pt film at high temperatures seriously affects the stability of the sensor, and degradation determines the sensor's operating temperature and service life. In this paper, Pt, Pt-Ta, and Pt-Pd microcalorimetric plates were prepared and analyzed for their sintering behavior, microstructure, electrical properties, and high-temperature stability using co-firing of resistors and alumina substrates. The film layers prepared by co-firing were better matched to the alumina substrate, and the sintered network of the film layers was better. The Pt-10%Ta microthermal plate has a 46% lower resistance temperature coefficient TCR compared to the Pt microthermal plate, and the resistance drift at 800°C is reduced to 2.11%/Day. And even at 1100°C, the Pt-Ta system also has a very low resistance drift -12%/Day (Pt26.6% /Day and Pt-Pd35.18%/Day) with improved high temperature stability. The addition of Ta allows the membrane layer to have fewer voids at high temperatures, reinforcing the high temperature characteristics of the resistance thermometer. It improves the stability and accuracy of the heating plate in high temperature gas sensor applications.

Interaction between flow topology and interface curvature of heat transfer interfaces during the evaporation process of liquid fuel droplets in a temporally evolving high-temperature gas jet

Interaction between flow topology and interface curvature of heat transfer interfaces during the evaporation process of liquid fuel droplets in a temporally evolving high-temperature gas jet

Failure behavior of RE2M2O7/YSZ TBCs prepared by EB-PVD in gas thermal shock-CMAS corrosion environment

Three types of thermal barrier coatings (TBCs), YSZ, LZC/YSZ and GZO/YSZ, were deposited by EB-PVD. These coating systems were then subjected to thermal shock-CMAS corrosion testing using a high-temperature gas spray gun. The results demonstrate that the double-layer thermal barrier coatings exhibit excellent resistance to thermal shock-CMAS corrosion. Microstructural analysis revealed that the LZC/YSZ coating mitigated thermal damage owing to the formation of a sealing layer at the CMAS/LZC interface through high-temperature chemical interactions with CMAS. Compared to LZC/YSZ, the GZO/YSZ coatings showed greater resistance to CMAS-induced damage, which was associated with lower theoretical optical basicity values. This research provides valuable insights into the coupled thermal shock-CMAS corrosion failure mechanisms of TBCs on turbine blades and paves the way for new system-safe applications of TBCs.

ВЫНОС МИКРОЭЛЕМЕНТОВ ФУМАРОЛАМИ АВАЧИНСКОГО ВУЛКАНА (КАМЧАТКА)

The trace element composition of high-temperature gases of Avachinsky volcano was investigated. For that purpose 25 samples of gas condensates and sublimates deposited in four quartz tubes were analyzed. The total average concentration of trace elements (excluding S, Cl, F, Si) in the condensates was 87 mg/l, the maximum 210 mg/l, among which B, K, Na, Br, As predominated. A large number of samples taken over a period 2013–2023 allowed us to evaluate the variations of element concentrations, their dependence on fumarole temperature and the season of sampling. The enrichment factors normalized for magnesium, made it possible to determine the elements transported in the plume in the form of volatile compounds (S, Cl, Te, I, B, Br, Cd, As, F, Re, Se, Bi, Tl, Hg, Sn, Sb, Pb, etc.) and in the form of silicate aerosol (Ti, Fe, Ga, Al, Ca, Mn, REE et al.). The ore element emission by Avachinsky volcano is comparable to that of Mutnovsky volcano (Kamchatka) and significantly lower than the emission by volcanoes in the stage of stationary degassing, such as Kudryavy and Pallas Peak (Kuril Islands), which can be explained by higher concentrations of HCl in the gases of the latter.

Optimizing Cold Spray Parameters for High Entropy Alloy Coatings Using Taguchi and Box–Behnken Design Approaches for Mechanically Alloyed Powder

AbstractThe present study focused on optimizing the cold spray (CS) process parameters for depositing Fe20Cr20Mn20Ni20Co20 (Cantor alloy) coatings using mechanically alloyed (MA) powder. A two-step design of experiments approach was employed, beginning with the initial screening of input variables using the L8 Taguchi method, followed by the refinement of process parameters through the Box–Behnken design of experiments. Key performance indicators included deposition efficiency (DE), coating thickness per pass, and microstructural parameters including porosity, cracks, and interfacial defects/delamination. The study identified process gas temperature as the primary factor influencing both DE and thickness per pass. Higher gas temperature and pressure, combined with increased scanning speed, resulted in higher DE. The DE of the MA Cantor alloy powder peaked at around 14-15%, with a deposit density greater than 99% achieved at the highest process gas temperature and pressure (1000 °C and 60 bar, respectively). The average hardness of the optimal CS coating deposited using MA powder was found to be 679 ± 17 HV0.1, which is approximately 90% greater than the average hardness reported for CS coatings deposited using atomized powder.

Thermodynamic investigation of biomass-steam gasification in converter vaporisation flue for synthesis gas production

Biomass gasification for hydrogen production is a highly promising technology for energy conversion and utilisation. This paper proposed a novel technology for the injection of biomass and steam into the flue of a converter vaporisation to produce hydrogen-rich syngas. The feasibility of hydrogen generation through gasification between biomass, steam, and carbon dioxide in the high-temperature flue gas was investigated based on the thermodynamic principle of Gibbs free energy minimisation. The influence of gasification parameters on the composition of syngas was also explored. The results indicate that in the gasification process, biomass and steam injected into the converter vaporisation flue can effectively inhibit the generation of by-products such as tar. As the steam volume increases, the volume fraction of hydrogen in the product also increases, while the concentration of carbon monoxide decreases. By adjusting the steam-to-biomass ratio, syngas with a hydrogen content exceeding 20% can be produced. At a reaction temperature of 1200 °C, with a steam addition of 5%, a biomass addition of 8 g/L, and a [Formula: see text] ratio of 3, the gas products are composed of 25% hydrogen and 67% carbon dioxide. The process has the potential to achieve a hydrogen yield of up to 90%, a syngas yield of 94%, and a CO2 conversion rate of 70%. Additionally, the lower heating value of the syngas is measured at 11.24 MJ/Nm3. The research results have confirmed the viability of the new technology, thus establishing a theoretical foundation for the industrial implementation of injecting biomass and steam into the converter vaporisation flue to produce hydrogen-rich syngas.

A Review on Sludge Drying after High Pressure Filter Pressing

Sludge drying is a key step in municipal sludge treatment. After mechanical dewatering, the water content of sludge is usually between 50% and 70%, which needs further drying. The main drying technologies include thermal drying, solar drying, ultrasonic drying and microwave drying, among which thermal drying technology is the most mature. Research shows that low-temperature drying technology has obvious advantages in reducing the release of harmful substances, energy consumption and cost. In terms of technology application, domestic sludge drying process is mainly divided into direct drying and indirect drying. Direct drying directly evaporates water through high-temperature gas, while indirect drying makes use of heat conduction effect to contact with high-temperature media. At present, indirect drying technology is mainly used in China, such as paddle type, disc type and thin layer drying. In particular, the low-temperature heat pump drying technology excels in terms of safety, footprint and energy consumption, with its ability to operate at lower temperatures, reduce the release of hazardous gases, and achieve environmental and economic benefits in a closed-cycle mode. This technology is suitable for small and medium-sized wastewater treatment plants and shows clear advantages in cases of budgetary constraints.

Research on combustion cycle-by-cycle variations under high load in SACI mode and application potential of i-EGR coupling air dilution when fueled with methanol and gasoline

Spark assist compression ignition (SACI) is a efficient combustion mode but roughness combustion under high load limits its application. This test analyzed the combustion parameters variation coefficient and quantified the correlation between combustion parameters with spark ignition ratio under high load SACI mode for engine fueled with methanol and gasoline, further studied the potential of i-EGR combining air dilution on improving combustion performance. Results showed that fueled with methanol can reduce in-cylinder pressure and pressure rise rate, and relieve the combustion roughness. However, compared with gasoline engine, the combustion parameters was more sensitive to ignition timing and i-EGR rate, especially for combustion phase parameters like ignition delay, combustion center and so on. Introducing small amount of high-temperature exhaust gas into cylinder will induce rougher combustion, but cylinder pressure significantly reduced and combustion phase parameters fluctuated with i-EGR rate increasing. Under high i-EGR rate, methanol as an oxygenated fuel was more beneficial to maintain stable combustion. I-EGR coupling air dilution can significantly improve the economic performance under high load SACI mode, fuel economy improvements of up to about 17.4% and 19% compared to the origin point when fueled with gasoline and methanol. EGR combining air dilution can simultaneously improve BSNOX, BSTHC, and BSCO emissions.

Effect of Current Waveform on Microstructure Evolution and Mechanical Properties of GH4169 High-Temperature Alloy Tungsten Inert Gas Additive Manufacturing.

Direct current (DC) and pulsed DC tungsten inert gas (TIG) additive manufacturing processes were employed to fabricate GH4169 high-temperature alloy specimens. Upon comparing and analysing the two additive manufacturing methods, the evolution of microstructure and mechanical properties of the additively manufactured specimens were discussed. It provided a useful reference for the engineering application of pulsed DC TIG technology. The results showed that the overall forming process of the specimen was relatively stable under the DC TIG additive manufacturing and pulsed DC TIG additive manufacturing processes. The aspect ratio of the deposited layer of the pulsed DC-deposited specimen was relatively low, and the deposited layer of the pulsed DC specimen became flatter, which was conducive to maintaining the stability of the molten pool during the deposition process and improving forming accuracy. The microstructure distribution of the deposited layer from bottom to top was relatively uneven, with columnar dendrites in the bottom layer, cellular crystals in the middle layer, and equiaxed crystals in the top layer. Compared with the DC TIG additive manufacturing of GH4169 high-temperature alloy specimens, the Laves phase of the pulsed DC specimens was significantly reduced, which improved the plasticity and brittleness of the material.

A Demonstration of the Risk-Informed NEI 18-04 Design Evaluation Model for the Modular High-Temperature Gas Reactor

Several advanced reactor designs are now under active development in the United States and elsewhere, promising sustainable solutions to the growing world energy needs. The designs currently being considered are quite diverse and different from the more established light water reactor technology that has dominated the operating commercial nuclear landscape. While advanced reactor concepts were first explored in the dawn of the nuclear age, they are now being reconsidered under the light of modern needs, and specifically, for their flexible operating conditions and inherent safety characteristics. In response, the U.S. Nuclear Regulatory Commission staff is moving forward with development of 10 CFR Part 53 rulemaking, which is a more risk-informed, technology-agnostic framework for licensing and regulating such new designs. The nuclear industry response to this regulatory initiative resulted in the technical report by the Nuclear Energy Institute, NEI 18-04 Revision 1, which provides an implementation roadmap of the risk-informed approach when defining the safety case for a new plant design. The implementation of this safety case may be a nontrivial exercise for an actual reactor design. This paper provides a demonstration of performing such an analysis for a representative advanced reactor. Public information from the General Atomics high-temperature gas reactor design was considered in this demonstration. The analysis workflow was facilitated with the FPoliSolutions’ proprietary Risk-Informed System Engineering (RISE) digital platform, a product that was presented in previous publications. RISE is one application of FPoli’s enterprise digital platform, which was created to facilitate orchestration of complex workflows leveraging recent technologies developed at national laboratories, such as Idaho National Laboratory’s RAVEN and EMRALD frameworks. The analysis described in the paper includes the selection and classifications of events, the integration of probabilistic risk analysis artifacts, and event modeling simulations for consequence evaluations. The results are then used for system, structures, and components safety classification and a synthesis of the safety case for the design in line with the frequency-consequence targets presented in NEI 18-04. The purpose of the analysis, as framed in RISE, is to readily produce outputs and views that can aid users and regulators in making risk-informed decisions to demonstrate their plant safety case.