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The physical properties of sealants could be crucial in affecting the performance and longevity of the polymer electrolyte membrane fuel cell (PEMFC). As the sealants' physical properties are temperature and stress-dependent due to their inherent viscoelasticity, their creep response must be explored. The numerical study presented in this article emphasizes evaluating the performance of low-temperature PEMFC (LT-PEMFC) influenced by polytetrafluoroethylene (PTFE) sealants' accelerated creep characterized by the compliance curves (MC-65). The performance of a 3D single-channel PEMFC model is investigated and compared for two cases, wherein the first case focused on PEMFC performance without sealant creep, and the second case incorporated sealants' accelerated creep to assess PEMFC performance. The detailed observation of reactant transport characteristics demonstrates that there is a substantial decline in oxygen reduction reaction (ORR) at the cathode gas diffusion layer (GDL) and cathode catalyst layer (CL) in the case of sealants' accelerated creep. Further, liquid saturation at the cathode GDL is observed to increase significantly, leading to a reduction in the performance of the cell. It is further conveyed that the current density for case 1 (without creep) and case 2 (sealants' accelerated creep) are 1.309655 and 1.041806 Acm−2, respectively, at a cell voltage of 0.4 V. The present study, therefore, addresses the viable interaction between fuel cell performance and the sealants' accelerated creep characteristics. • Influence of sealant creep on PEMFC performance is explored. • Performance study is carried for a 3D PEMFC model with/without sealants' creep. • Current density drops by 20.45% for sealants' creep, compared to no creep at 0.4 V • Concentration overpotential is observed to increase due to sealants'creep. [ABSTRACT FROM AUTHOR]

Active thermal management strategies are critical for optimizing fuel cell performance by regulating stack temperature in response to output power variations. However, existing approaches often fail to adequately consider the impact of multi-source perturbations, such as gas supply perturbations or voltage distribution heterogeneity. To bridge this gap, we propose a nonlinear autoregressive exogenous network surrogate model to simulate fuel cell voltage distribution. This model is integrated into an advanced online thermal management control system. The proposed strategy employs an artificial bee colony optimization algorithm and a tube-based robust model predictive control strategy with relaxation factors. It enables real-time regulation of coolant outlet and inlet temperatures in response to variations in load current, reactant gas flow rate and pressure, and voltage distribution characteristics. Experimental results demonstrate that at a current density of 1.0 A/cm2, the strategy increased the average cell voltage by 6.1 mV, reduced the voltage extreme difference by 40.3%, and lowered the voltage standard deviation by 54.9%. The active thermal management strategy significantly enhances the performance of fuel cells under multi-source perturbations. [Display omitted] • Both thermal management system internal and external perturbations are considered. • Voltage with stack temperature and stack temperature difference is modeled. • A constraint relaxation tube-RMPC is designed for fuel cell steady-state processes. • A NARX neural network is constructed to predict fuel cell performance in real time. • The strategy improves both stack performance and voltage consistency. [ABSTRACT FROM AUTHOR]

A stacked pulsating gas-liquid-solid circulating fluidized bed microbial fuel cell (SPCF-MFC) was proposed and constructed to further improve the power generation and sewage treatment performance. The impact of pulse frequency (f), pulse amplitude (A), solid circulating rate (G s) and gas flow rate (Q g) on the maximum output voltage (U m), chemical oxygen demand (COD) removal rate (R c) and comprehensive energy consumption (W) of the system was investigated using response surface methodology (RSM) and Box-Behnken design (BBD). The results indicated that the introduction of pulsed liquid flow coupled with gas-liquid-solid circulation operation mode can effectively improve the power output and sewage treatment efficiency. Based on the response regression model, the optimal operating condition (f = 0.268 Hz, A = 0.073 m/s, G s = 2.88 kg/(m2·s), Q g = 1.85 L/min) was obtained. The deviation between the predicted and experimental results was less than ±2.5 %, which verified the accuracy of the regression model. [Display omitted] • A stacked pulsating gas-liquid-solid circulating fluidized bed MFC is proposed. • Response surface methodology is used to optimize the experimental conditions. • The impact of various operating parameters on the system is investigated. • Regression models of maximum output voltage and COD removal rate are obtained. • The maximum output power of the system can exceed 1000 mW/m2. [ABSTRACT FROM AUTHOR]

• This review discussed various mineral selenium compounds for Hg0 removal. • The adsorption performance and influence factors are summarized. • The adsorption mechanisms and reusability are also summarized. • MSe adsorbents are effective in removing mercury. Mercury (Hg) pollution has been a global concern in recent decades, posing a significant threat to entire ecosystems and human health due to its cumulative toxicity, persistence, and transport in the atmosphere. The intense interaction between mercury and selenium has opened up a new field for studying mercury removal from industrial flue gas pollutants. Besides the advantages of good Hg° capture performance and low secondary pollution of the mineral selenium compounds, the most noteworthy is the relatively low regeneration temperature, allowing adsorbent regeneration with low energy consumption, thus reducing the utilization cost and enabling recovery of mercury resources. This paper reviews the recent progress of mineral selenium compounds in flue gas mercury removal, introduces in detail the different types of mineral selenium compounds studied in the field of mercury removal, reviews the adsorption performance of various mineral selenium compounds adsorbents on mercury and the influence of flue gas components, such as reaction temperature, air velocity, and other factors, and summarizes the adsorption mechanism of different fugitive forms of selenium species. Based on the current research progress, future studies should focus on the economic performance and the performance of different carriers and sizes of adsorbents for the removal of Hg0 and the correlation between the gas-particle flow characteristics and gas phase mass transfer with the performance of Hg0 removal in practical industrial applications. In addition, it remains a challenge to distinguish the oxidation and adsorption of Hg0 quantitatively. [ABSTRACT FROM AUTHOR]

Methane steam reforming is a key technology for large-scale hydrogen production; however, its performance and lifetime are significantly influenced by carbon deposition. In this study, a new type of methane steam reformer with a self-regulating structure is proposed to inhibit carbon deposition and improve the lifetime of the reformer. By incorporating a main gas channel and branch gas channels within the reformer, the gas flow direction can be automatically adjusted, allowing the primary location of the reforming reaction to shift when partial blockages occur due to carbon deposition. To evaluate the feasibility of the proposed new structure, numerical models are developed to simulate and compare a conventional reformer with the newly designed reformer. The simulation results show that the lifetime of the proposed novel structure reformer is increased by approximately 56.0% compared to that of the conventional reformer with a packed bed structure when β = 2 and L/R = 5. The hydrogen molar fraction at the outlet of the novel structure reformer (β = 2) is on average 5.41% higher than that of the conventional packed bed reformer (β = 3) when their lifetimes are similar. Additionally, the proposed novel structure reformer can achieve superior performance when applied to large L/R conditions. These findings suggest that the proposed design offers a promising strategy for developing a durable and high-performance methane steam reformer. • A new type of methane steam reformer with a self-regulating structure is proposed. • Reformer performance is simulated by numerical models. • The lifetime of the proposed reformer is approximately 1.56 times longer than that of the conventional reformer. [ABSTRACT FROM AUTHOR]

Segmented fuel cell technology is considered as an important real-time diagnostic methodology for proton exchange membrane fuel cell (PEMFC). In the study, physical property characterizations are conducted for both segmented and unsegmented graphite materials, including thickness, thermal conductivity, electrical conductivity, and contact resistance. By combining test results with the developed three-dimensional multi-physics computational fluid dynamics (CFD) model, the output performances and corresponding parameter distribution characteristics are quantitatively investigated for fuel cells with segmented/unsegmented gas flow plates. The measurement results of electrical conductivity between adjacent segments validate the consistency and reliability of presented manufacturing processes. The thermal conductivity at 80 °C is approximately 36.0 W m−1 K−1 for segmented graphite samples and 46.7 W m−1 K−1 for unsegmented material. Simulation results show that the output voltage difference rise from 0.01 V to 0.06 V with current density increasing from 0.5 to 2.0 A cm−2. The lower performance for segmented fuel cell could be attributed to the inhibition of electron transport and thus the increment of ohmic voltage loss. The general distribution characteristics of current density, temperature, and membrane water are similar. However, the local current density of specific regions corresponding to the insulating material is obviously smaller, and higher temperature regions or spots are observed at the junction of segment and insulating material. It is suggested to minimize the proportion of insulating material in segmented graphite flow plates while ensuring enough mechanical strength and gas impermeability. Furthermore, negligible differences of output voltage and ohmic voltage loss are observed for segmented fuel cells when the segment number increases from 27 to 64. The study aims to provide essential data support for numerical simulation models and valuable guidance for segmented fuel cell test technologies. [Display omitted] • Performances are investigated by integrating test results with 3D CFD model. •Thermal conductivity of unsegmented samples is 30% higher than segmented samples. •Output voltage decreases for segmented cell due to increment of ohmic voltage loss. •Higher temperature is observed at the junction of segments and insulating material. • Negligible voltage differences are found for 3 × 9, 4 × 12, and 4 × 16 segmented cells. [ABSTRACT FROM AUTHOR]

To investigate the impact of ammonia volume fraction (X NH3) and obstacle blockage ratios on the explosion propagation of a hydrogen-ammonia mixture, this work conducts a numerical study of flame propagation in a closed duct under three different obstacle blockage ratio configurations, focusing on flame structure, propagation speed, overpressure development, key free radicals, and evolution process of vortex dynamics. The research reveals that increasing the X NH3 decreases the density gradient behind the flame front, weakens velocity shear across gas layers and flow instability, and inhibits the formation rate and quantity of key free radicals, which dampens flame propagation and explosion overpressure in closed ducts. Moreover, obstacle blockage ratios near the ignition source and at the end significantly influence flame propagation. As the X NH3 increased from 0 to 0.2, the steepest attenuation of the flame propagation speed is observed for the decreasing gradient of obstacle blockage ratio (BR-Down), with a 52% attenuation. The arrangement with an increased blockage ratio (BR-Up) exhibits the highest flame propagation speed and overpressure rise rate under all conditions, reaching 373.62 m/s and 2058.59 MPa/s respectively when the X NH3 = 0. Finally, the vortex distribution within the duct is visualized by the numerical simulation results, clearly illustrating the influence of the X NH3 and the obstacle blockage ratio on the generation and evolution of spatial vortices. The research offers a theoretical foundation for the safety of hydrogen-ammonia mixture explosive combustion, particularly in confined spaces containing obstacles. • Adding ammonia reduces flame speed and explosion pressure in ducts. • Flame propagation is significantly affected by obstacles near the ignition source and end. • Increased ammonia volume leads to more intense vortices and complex flame dynamics. • Faster flame propagation and higher pressure peaks are resulted from higher obstacle blockage ratios. [ABSTRACT FROM AUTHOR]

Gas flow influences flame morphology and flame propagation. Resorting to large eddy simulation, this paper analyzes flow characteristics and dynamics of confined hydrogen-air explosion. The results reveal that the gas at flame surface accelerates, then decelerates, and finally reversely accelerates. The variation can be contributed to transition from pressure-induced acceleration to deceleration effects. With initial pressure increasing, the decelerating effect has stronger intensity and wider influencing area. With initial turbulent fluctuation velocity increasing, intensity and influencing scope of the decelerating effect rise under higher initial pressure. In unburnt zone, forward gas flow is dominated by accelerating effect of pressure for equivalence ratios of 1.0 and 2.0. In burnt zone, gas flow is alternately dominated by accelerating and decelerating effects of pressure gradient. Vortex appear after flame surface and is largest near flame wrinkles. Formation of the strongest vorticity is dominated by baroclinic torque which represent Rayleigh Taylor instability. [Display omitted] • Effects of initial pressures and turbulence on flow field are investigated. • Gas on flame surface accelerates, decelerates and finally reversely accelerates. • Increased initial pressure significantly promotes both acceleration stages. • Gas flow at over a half flame surface is dominated by pressure gradient. • Vortices distribute after flame surface and are controlled by baroclinic torque. [ABSTRACT FROM AUTHOR]

Research on hydrogen engines has been actively pursued to achieve carbon neutrality in the transportation sector. To optimize the combustion characteristics of hydrogen engines under various driving conditions, active and precise control of the hydrogen injection flow rate is crucial. Lightweight prediction for hydrogen injection rates from pintle-type injectors, which are widely used in hydrogen engines, is required for the control of the injection rate as well as the model-based engine development. However, lightweight injection rate prediction for gaseous fuel has been conducted solely for hole-type injectors and not for pintle-type injectors that have an annular internal flow path with complex configurations. In this study, a lightweight methodology is introduced to predict the hydrogen injection rate of pintle-type hydrogen injectors based on the compressible flow theory of converging-diverging nozzles with minimum mass flow rate data obtained with a safer surrogate gas. The validity of the method for various injection conditions and gases (nitrogen, helium, and hydrogen) is discussed. The methodology demonstrated prediction accuracy of over 92% for nitrogen and helium injection rates under different injection pressures (1.5–4 MPa) and ambient pressures (0.1–2 MPa). The versatility of the prediction methodology for various gases, including hydrogen, was also confirmed. The error sources were analyzed thoroughly based on the dynamic characteristics of the pintle behavior and differences in gas properties. • A lightweight method for predicting H 2 injection rates from pintle injectors is proposed. • Minimum mass flow rate data were obtained for calculating the nozzle throat area. • Safer surrogate gases can be used to predict H 2 injection rates. • The accuracy of the method showed over 92% for various gases and injection conditions. • Error analysis was conducted based on compressible flow theory and pintle dynamics. [ABSTRACT FROM AUTHOR]

A high performance plasma jet actuator (HPJA) has been developed to address the challenges of ignition difficulty and low combustion efficiency in ramjet combustors operating under transition mode and low pressure conditions. HPJA is capable of realizing the functionalities of large-area hot jet ignition, fuel activation, and enhanced combustion. The discharge characteristics, fuel activation characteristics, spray characteristics, ignition and assisted combustion characteristics of HPJA was investigated through experimental methods. The discharge power of HPJA initially increases, then decreases, and subsequently increases with the rise in carrier gas flow. Following fuel injection, the discharge power exhibits a similar trend but with an increased magnitude, showing a 21.9 % enhancement when Air = 30 SLM. HPJA has the capability to activate fuel, generating small molecule flammable substances such as H 2 and CH 4. The flow rates of fuel and nitrogen have a significant impact on the effective cracking rate. As the fuel flow increases, the effective cracking rate decreases. Similarly, with an increase in nitrogen flow, the effective cracking rate initially decreases before increasing again. Upon activation of HPJA excitation, there is a notable reduction in the particle diameter of outlet fuel, leading to a 41.5 % decrease in D 32 under W N2 = 40 SLM and Fuel = 0.25–1.25 g/s. Based on the stability of the HPJA outlet's hot jet production, it is categorized into two operational modes: fuel excitation mode and jet evolution mode. As the carrier gas flow increases, the fuel required for HPJA to transition into the jet evolution mode decreases, thereby facilitating rapid ignition functionality. Under Ma = 0.2 and T∗ = 320 K conditions, as P∗ decreases from 107 kPa to 45 kPa, HPJA is more prone to forming a stable hot jet, resulting in an 88.9 % reduction in the fuel needed to enter the jet evolution mode. [Display omitted] • Designed an actuator with both ignition and assisted combustion functions – HPJA. • The hot jet performance of the HPJA was studied. • Small molecular products such as H 2 can be produced. • Atomization quality has significantly enhanced. • The performance of HPJA was tested in the ramjet combustor. [ABSTRACT FROM AUTHOR]

During an aging test of a high temperature proton exchange membrane fuel cell (HT-PEMFC) without exhaust pressure control loop, the anode and cathode pressures are dependent on variations in gas flow and atmospheric pressure. The voltage degradation rate is then impacted by atmospheric pressure variations. To extract the aging rate independently of the pressure, a possible solution is to estimate the voltage variation at a given pressure change. In this work, this voltage/pressure sensitivity was estimated in post-processing, by fitting regression planes (on measured voltage data) in the three dimensions: voltage, pressure, and time. It was applied on an aging test of 2753 h at 160 °C, at ambient pressure and at different constant currents (0.2, 0.4, and 0.6 A/cm2) which was carried out on an Advent Technologies Inc. PBI MEA of 45 cm2 active surface. The impact of varying atmospheric pressure on the calculation of degradation rates is then discussed and compared with another method developed in a previous work. It was found that a variation of 6 mV (2.4 % of initial voltage) at 1 A/cm2 during an aging test can be attributed to pressure variation alone, and not to cell degradation. Furthermore, it was observed that the voltage/pressure sensitivity is different depending on the period analyzed, at identical operating conditions (which would indicate that the dependence on pressure varies during aging). Indeed, at 0.2 A/cm2, the voltage response to a variation in pressure was quantified at approximately 50 μV/mbar and 80 μV/mbar at the start and end of life respectively. This method could therefore be used as an on-line diagnostic tool to monitor the fuel cell state of health. [Display omitted] • Aging test of a high temperature proton exchange membrane fuel cell for 2753 h. • Model of the impact of pressure and time on cell voltage. • Obtaining coefficients of the voltage variation against pressure and time. • Degradation rate can significantly be impacted by pressure variations only. • Method for post processing aging tests to correct the voltages against pressure. [ABSTRACT FROM AUTHOR]

The key problem for the long-term operation of the satellite in ultra-low Earth orbits (ULEO) and its safety is to provide the propulsion system with a sufficient amount of working fluid. Gas from the atmosphere can be used as the working fluid, for which the satellite is equipped with an air intake. In this paper, the problem of rarefied gas flow in such an air intake in ultra-low Earth orbit (140 km) was solved. Using the method of event-driven molecular dynamics (EDMD), we studied how the narrowing of the effective aerodynamic cross-section after the air intake (in the ionization chamber) can affect the compression ratio and the flow field. It was shown that the flow field in the air intake depends significantly on the geometry of the subsequent sections of the device, therefore it is incorrect to model the flow in the air intake separately from the rest of the internal tract of the propulsion system, as it was done in the literature earlier. • The rarefied gas flow inside the satellite air intake in ultra-low Earth orbit (140 km) was studied. • Flow field in the air intake depends significantly on the geometry of the subsequent sections of the device. • Partial permeability of the backplate qualitatively changes the dependence of the compression ratio on the channel length. • With a partially permeable backplate the dependence of the compression ratio on the channel length is not monotonic. [ABSTRACT FROM AUTHOR]

To investigate which breathing systems are available and why they are selected in dogs weighing 5–10 kg. Anonymous online voluntary open survey. An online survey, designed following CHERRIES guidelines, was advertised through the American College of Veterinary Anesthesiologists - List, Association of Veterinary Anaesthesia and European College of Veterinary Anaesthesia and Analgesia (February–March 2022). A convenience sample was taken. Of the 256 responses received, 138 were completed. This included (n responses received) veterinarians (107) and veterinary nurses or technicians (29) actively involved in the anaesthesia of dogs. The most prevalent breathing systems available to respondents were circle (99%), coaxial Bain (79%) and modified Ayre's T-piece (with adjustable pressure limiting valve) (72%). When recommending a dog weight range suitable for the use with these systems, respondents advised a median (interquartile range) from 5 (3–10) to 100 (100–100), 3 (0–8) to 20 (10–33) and 0 (0–0) to 10 (7–10) kg, respectively. Respondents agreed or strongly agreed that important factors in selecting a breathing system were the fresh gas flow requirement (92%), dog weight (91%), resistance (83%) and environmental pollution (79%). In clinical scenarios based on 5–10 kg dogs, the circle system was chosen by 58% for a thin and 77% for a keel-chested versus 44% for an obese and 66% for a barrel-chested dog, respectively. The circle system is the most commonly available breathing system. The minimum weight limit used for the circle system is less than that reported by previous surveys. Several factors influence the choice of breathing system other than dog weight. [ABSTRACT FROM AUTHOR]

This study investigated the discharge voltage characteristics of an argon-fed lanthanum hexaboride heaterless hollow cathode to assess the influence of flow rate, discharge current, background pressure, and applied magnetic field strength. Decreasing the flow rate from 15 to 3 sccm led to a considerable increase in discharge voltage and peak-to-peak oscillation, particularly for flow rates below 5 sccm. Subsequently, variation in discharge current was tested at 4–7 A; this test revealed that the discharge voltage decreases from 53 to 48 V as the discharge current increases, while the peak-to-peak oscillation increases by approximately 2 V with the rise in discharge current. At high background pressures (8.1 × 10−4 Torr), the discharge voltage decreased by 15 V, and the peak-to-peak oscillation was maintained at 5 V. Furthermore, the spectral analysis of the discharge voltage indicated the occurrence of high-energy oscillations at 10–500 kHz owing to ionization instability. The discharge voltage decreased when the strength of an externally applied axial magnetic field increased from 0 to 118 G. Such a result can be attributed to increased ionization (caused by the applied magnetic field) in the emitter and cathode-keeper region, thereby decreasing sheath potential on the emitter surface. • Discharge voltage is used as an important parameter for analyzing the cathode performance. • When the gas flow rate decrease, the discharge voltage fluctuation increases. • High background pressure leads to the disappearance of voltage oscillation amplitude variation. • Applying a magnetic field causes a decrease in discharge voltage, and the oscillation of the discharge voltage is suppressed. • The magnetic field reduces discharge voltage by increasing the anode's surface area available for current reception. [ABSTRACT FROM AUTHOR]

One of the important tasks of space flight safety is the ability of a wing to maintain stability in an oncoming turbulent flow. In this case, the spacecraft must move the greatest distance. The paper studies the motion of a thin plate near a boundary in an oncoming flow of rarefied gas. At low Reynolds numbers, the effect of the boundary on the plate is studied, and the possibility of self-propulsion is shown. • The drag force of the plate increases sharply as the distance to the boundary decreases. • The lifting force and moment change from the center of the plate to the boundary decreases. • The point of application of the resultant force shifts to the rear edge of the plate. • Self-motion is possible for plates that have a common rib. [ABSTRACT FROM AUTHOR]

Yttria-stabilized zirconia (YSZ) coatings are widely utilized thermal protective layers for metal and superalloy surfaces. These coatings are employed as thermal barrier coating (TBCs) to insulate metallic parts from higher thermal energy, thereby minimizing the cooling need for the topcoat ceramic layer. The choice of material is 7 wt% YSZ due to its exceptional capability to withstand challenging conditions characterized by extremely high temperatures and pressures, typically employed by the atmospheric plasma spraying (APS) in gas turbines, effectively extending their lifespan and improving performance. The deposition process of TBCs is significantly influenced by various spraying parameters, including gas flow rate and current (amp). These key parameters mutually play a significant role in controlling thermal stability, phase composition, and improved mechanical and microstructure properties. The aim of this research is to evaluate and contrast the impact of various spraying parameters on YSZ TBC performance. Accordingly, the influence of Hydrogen (H 2), Argon (Ar) flow rate, and Current (amp) was investigated. Microstructure and elemental mapping studying was conducted using Field Emission Scanning Electron Microscopy FESEM/EDS and phase studying was examined with X-ray diffraction (XRD). Porosity was measured by IMAGE J software while hardness measurement was calculated by Vickers hardness tester. Additionally, thermal cycling tests were conducted between 700 °C and 1200 °C. The porous coatings exhibited poor performance, delaminating early during the tests. In contrast, dense coatings performed significantly better, enduring up to 140 cycles before failure. [ABSTRACT FROM AUTHOR]

To address the problems of uneven mass distribution and hydrothermal management imbalance in flow fields, this study proposes a snowflake slope composite flow field (SSCFF). A three-dimensional multiphase computational fluid dynamics (CFD) model was developed to analyze the differences between the SSCFF and traditional flow fields, and to investigate the effects of gas inlet and outlet configurations, height ratios (L d / D ), and the number of main channels (N) on the performance. The study shows that the SSCFF excels in gas distribution and temperature control, with a maximum power density 35.5% higher than the honeycomb structure. The diagonal inlet and outlet configuration effectively reduces the risk of local hotspots and flooding. With L d / D of 0.9, the uniformity of oxygen distribution improves significantly and the current density reaches 1.168 A cm−2. Additionally, with 6 main channels, the proton exchange membrane (PEM) achieves a higher hydration level, which boosts catalytic activity and working efficiency. [Display omitted] • The SSCFF enhances net power density by 35% than a honeycomb flow field. • The diagonal inlet and outlet configuration reduces localized concentration loss. • L d / D of 0.9 balances the lateral and longitudinal flow of gases within the channels. • N of 6 improves the hydration level of PEM with a performance of 1.168 A cm−2. [ABSTRACT FROM AUTHOR]

Ammonia has recently attracted attention as a hydrogen carrier and fuel, based on the power-to-fuel concept. This concept can be realized using Ru-supported rare-earth oxides for the synthesis of ammonia from hydrogen and nitrogen (3H 2 + N 2 → 2NH 3) under mild conditions. However, at a high H/N ratio, Ru catalysts exhibit hydrogen poisoning, which reduces their activity for ammonia synthesis. This study investigates the effect of the H/N ratio on the ammonia synthesis activity of the developed Ru catalyst Ru(5 wt%)/Ce 0.5 La 0.4 Si 0.1 O 1.8 under isothermal conditions (350−500 °C). The optimal H/N ratio for achieving the highest catalytic activity decreases as the temperature is lowered (H/N = 0.5 at 350 °C; H/N = 2.0−2.5 at 450 °C). In a multibed reactor, adjusting the H/N ratio to a lower value in the downstream catalyst beds—where the temperature decreases along the gas flow path—can enhance the overall rate of ammonia production by optimizing the reaction conditions in these cooler stages. We propose a system to control the H/N ratio for each catalyst bed in a multibed reactor and demonstrate an increase in the rate of ammonia production when using a double-bed reactor containing the Ru/Ce 0.5 La 0.4 Si 0.1 O 1.8 catalyst. The proposed system offers various opportunities to accelerate the use of ammonia as a hydrogen carrier and fuel. [Display omitted] • An NH 3 synthesis system tailored to the properties of Ru catalysts is proposed. • The developed Ru catalyst is used to demonstrate the effectiveness of this system. • The H/N ratio at which the catalyst exhibits the highest activity shifts toward a lower value at lower temperatures. • A double-bed reactor that enables H/N ratio control in both beds is developed. • The total NH 3 production rate in the reactor is enhanced by H/N ratio control. [ABSTRACT FROM AUTHOR]

The first measures to reduce the environmental harm from volatile anaesthetics are implementation of minimal fresh gas flow strategies and avoidance of desflurane. Although anaesthetic waste gas capture systems generally exert high capturing efficiencies, only about half of volatile anaesthetics used in the operating room are accessible for capture. Industry-sponsored reports promise a reduction of the global warming potential by both incineration and recycling of captured volatile anaesthetics. However, independent high-quality peer-reviewed studies are needed to confirm these findings. [ABSTRACT FROM AUTHOR]

Interest in passive flow filter systems to remove sevoflurane from anaesthetic machine exhaust have increased recently to mitigate the environmental impact of volatile anaesthetics. These filter systems consist of chemically activated carbon, with limited evidence on their performance characteristics. We hypothesised that their efficiency depends on filter material. Binding capacity was tested for three carbon filter materials (CONTRAfluran®, FlurAbsorb®, and Anaesthetic Agent Filter AAF633). Adsorption efficiency and resistive pressure were determined during simulated ventilation at different stages of filter saturation and fresh gas flow. In addition, sevoflurane concentration in filtered gas was measured at randomly selected anaesthesia workstations. Sevoflurane concentration in filtered gas exceeded 10 ppm when saturated with 184 ml sevoflurane each for CONTRAfluran and FlurAbsorb and 276 ml for AAF633. During simulated ventilation, sevoflurane concentration >10 ppm passed through CONTRAfluran and AAF633 at fresh gas flow 10 L min−1 only at maximum saturation, but through FlurAbsorb at all stages of saturation. The resistance pressure of all filters was negligible during simulated ventilation, but increased up to 5.2 (0.2) cm H 2 O during simulated coughing. At two of seven anaesthesia workstations, sevoflurane concentration in filtered exhaust gas was >10 ppm. Depending on the filter material and saturation, the likelihood of sevoflurane passing through passive flow carbon filters depends on the filter material and fresh gas flow. Combining the filter systems with anaesthetic gas scavenging systems could protect from pollution of ambient air with sevoflurane. [ABSTRACT FROM AUTHOR]

To facilitate the formation of bifocal aspheric optical surfaces, we present an approach for predicting the surface profile of bifocal aspheric surfaces formed by the gas-liquid interface when an elliptical nozzle gas jet is employed. Through an analysis of the gas flow field morphology emanating from the elliptical nozzle, we inferred the impact of gas jet parameters on the gas-liquid interface surface shape within the core region of the gas jet. By analyzing the variation in the gas flow field morphology emitted from an elliptical nozzle, we deduced the influence patterns of gas jet parameters on the gas-liquid interface surface shape within the gas jet's core region. Theoretical analysis is substantiated by numerical simulations, confirming regular changes in the vertex curvature and conic constant of mirror blanks concerning variations in jet initial velocity and nozzle aspect ratio. A comparison between experimental data and numerical simulation results reveals an average prediction deviation of 0.0083 mm−1 for the vertex curvature and a prediction deviation of 10.7 % for the conic constant, challenging to rectify within numerical simulations. Hence, an empirical model, incorporating jet parameters, is developed based on experimental data to predict the vertex curvature and conic constant of mirror blanks. This model demonstrates an average prediction error of 2.901 × 10−3 mm−1 for the vertex curvature and 7.64 % for the conic constant, surpassing the predictive accuracy of the numerical simulation model. • Reveals stable 'potential core region' in gas-liquid interface. • Advances continuous elliptic jet flow theories. • Introduces new optical processing method for bi-conic surfaces. • Develops predictive models for precise surface shaping. [ABSTRACT FROM AUTHOR]

Spontaneous ignition induced by high-pressure hydrogen leakage has primarily been discussed qualitatively, focusing on factors such as release pressure, downstream tube size, and the rupture of the burst disk. However, quantitative investigations and prediction models remain limited and unclear. In this paper, we introduce the relative molecular mass M and delve into its influence on the critical pressure threshold for spontaneous ignition of high-pressure hydrogen leaks. Additionally, we introduce the mass flow rate Q , as a metric to quantify the impact of opening area and shape on the ignition process. By integrating six key factors, including tube diameter D , tube length L , atmospheric pressure P a , burst disk opening time t , gas mass flow rate Q , and gas relative molecular mass M , four dimensionless factors affecting the critical leakage pressure were determined by using similarity analysis. The correlation between the dimensionless numbers was verified by correlation analysis and calibrated to the experiments of this paper and other authors. Finally, a critical criterion for spontaneous ignition from leakage in high-pressure hydrogen tubes was established to provide a basis for safety evaluation and prevention techniques for high-pressure hydrogen. [Display omitted] • The effect of the relative molecular mass of gases in the high-pressure region on the spontaneous ignition of high-pressure hydrogen leakage is discussed. • The dimensionless parameter affecting the critical pressure for spontaneous ignition of high-pressure hydrogen leakage is investigated. • The critical pressure criterion for the spontaneous ignition of high-pressure hydrogen leakage is established. [ABSTRACT FROM AUTHOR]

Regulatory authorities in biopharmaceutical industry emphasize process design by process understanding but applicable tools that are easy to implement are still missing. Soft sensors are a promising tool for the implementation of the Quality by Design (QbD) approach and Process Analytical Technology (PAT). In particular, the correlation between viable cell counting and oxygen consumption was investigated, but problems remained: Either the process had to be modified for excluding CO 2 in pH control, or complex k L a models had to be set up for specific processes. In this work, a non-invasive soft sensor for simplified on-line cell counting based on dynamic oxygen uptake rate was developed with no need of special equipment. The dynamic oxygen uptake rates were determined by automated and periodic interruptions of gas supply in DASGIP® bioreactor systems, realized by a programmed Visual Basic script in the DASware® control software. With off-line cell counting, the two parameters were correlated based on linear regression and led to a robust model with a correlation coefficient of 0.92. Avoidance of oxygen starvation was achieved by gas flow reactivation at a certain minimum dissolved oxygen concentration. The soft sensor model was established in the exponential growth phase of a Chinese Hamster Ovary fed-batch process. Control studies showed no impact on cell growth by the discontinuous gas supply. This soft sensor is the first to be presented that does not require any specialized additional equipment as the methodology relies solely on the direct measurement of oxygen consumed by the cells in the bioreactor. • Non-invasive soft sensor method for simplified on-line cell counting. • Implemented in exponential growth phase of CHO cells. • Dynamic oxygen uptake rate as only predictor resulted in a correlation coefficient of 0.92. • No negative influences on cell growth as oxygen starvation was prevented. • 5-k cross validation showed RMSE of 0.7 × 106 cells/mL. [ABSTRACT FROM AUTHOR]

Rare earth ytterbium monosilicate (Yb 2 SiO 5) is one of the most ideal candidates for environmental barrier coatings. In this paper, Yb 2 SiO 5 coating was successfully fabricated by atmospheric plasma spraying technology. The effect of main gas flow rate and spraying powder composition on the microstructure and phase composition of Yb 2 SiO 5 coating were systematically investigated to solve the volatilization of SiO 2 during plasma-spraying process. The results showed that Yb 2 SiO 5 coating was relatively dense with the less internal defects under the main gas flow rate of 35 L/min, and the main gas flow rate from 30 L/min to 40 L/min had no significant effect on the melting effect of spraying powder and the porosity of coating. Yb 2 SiO 5 coating was composed of Yb 2 O 3 , Yb 2 SiO 5 two crystal phases and amorphous phase. The phase composition of coating was not affected by the change of main gas flow rate. After heat-treatment at 1400 °C for 20 h, Yb 2 SiO 5 crystal phase precipitated from the coating, and the content of Yb 2 SiO 5 phase reached 74.29 mol%, and the remaining phase was Yb 2 O 3 phase. The Yb 2 SiO 5 -25.71 mol% SiO 2 coating was still dense, the content of Yb 2 SiO 5 crystal phase was up to 97.76 mol% after heat-treatment, and the content of Yb 2 Si 2 O 7 phase was only 2.24 mol%, indicating that excessive addition of a certain amount of SiO 2 could compensate for the volatilization of SiO 2 , so as to prepare Yb 2 SiO 5 coating with approximate stoichiometric ratio. [ABSTRACT FROM AUTHOR]

To improve the oxidation and ablation resistance of SiC f /SiC composites, the as-synthesized ultrafine HfB 2 powder was used as the modification phase to fabricate SiC f /SiC-HfB 2 composites, and their oxidation and ablation behaviors were investigated. Compared with the unmodified SiC f /SiC composites, the oxidation resistance at 800–1500 °C and the ultra-high temperature ablation resistance of SiC f /SiC-HfB 2 composites were significantly improved. After oxidation, a compact compound glass scale consisting of HfO 2 , HfSiO 4 and Si-Hf-O glass was formed, providing the effective oxidation protection. A dual-phase oxide scale composed of HfO 2 skeleton and Si-Hf-O glass was formed after ablation, exhibiting the high viscosity, the significant oxygen-blocking effect and resistance to gas flow scouring. The improved oxidation and ablation resistance of SiC f /SiC-HfB 2 composites could be attributed to the effective protective role of oxygen-blocking scales formed during the oxidation and ablation processes. [ABSTRACT FROM AUTHOR]

Pt nanoparticles (NPs) loaded on TiO 2 photocatalyst as cocatalyst is well-known for significantly enhancing photocatalytic H 2 production from an aqueous methanol solution since Pt NPs in contact with the TiO 2 surface can improve the charge separation by accepting photoexcited electrons. In this study, another catalytic role of Pt NPs was clearly evidenced by a simple method, using a flow reactor and gas mixture of methanol and water in argon carrier, in which TiO 2 photocatalyst and separately supported Pt NPs are located without physical contact. It was demonstrated that hydrogen radical species, generated on the TiO 2 photocatalyst, are capable of migrating through a quartz wool layer of several millimeters in length and reach the Pt NPs on alumina support, where coupling of the hydrogen radical to form H 2 molecules is catalytically promoted by the Pt NPs. [Display omitted] • Mixture of TiO 2 and Pt/Al 2 O 3 promotes photocatalytic H 2 production and selectivity. • Experiments with a flow reactor evidenced catalytic role of Pt cocatalyst. • Pt NPs catalyze coupling of hydrogen radicals to form H 2. • Hydrogen radical can migrate for millimeter scale in gaseous reaction mixture. • Shorter distance between TiO 2 and Pt NPs gives higher H 2 production rate. [ABSTRACT FROM AUTHOR]

In order to quantify the failure performance of PEMFCs' C/C composite bipolar plates (BPs) under considering the uncertainty in multiscale sizes and loads, the failure probability function (FPF) of BPs at cold start is estimated. A three-stage multiscale simulation method is proposed for mechanical behavior analysis of multi-component heterogeneous composites. And the efficient estimation of FPF for C/C composite BPs is achieved via the proposed multiscale simulation method and decoupling sparse integration method, in which the unified density weight is constructed to decouple the double-loop framework of analyzing FPF, thereby reducing the computational complexity. Results indicate that the dangerous positions of BPs are around the gas flow channels and bolt holes. And the dangerous components are the carbon matrix and the interface between the matrix and fiber. The radius of elliptical fibers affects the distribution of failure factors on microscopic components, thereby affecting the variation of failure probability with fiber sizes significantly. The distribution parameter of composite layer thickness in BPs has a significant effect on structural safety, and the FPF result can be used to effectively guide the design of structure. Therefore, the proposed method is of great significance for guiding the rapid parameter design of composite BPs. • Multiscale and multi-component failure analysis method is first proposed for BPs. • FPF of BPs is decoupled by constructing the unified density weight function. • Dangerous failure position and component are determined in C/C composite BPs. • Influences of macro and micro parameters on FPF of BPs are clarified and analyzed. [ABSTRACT FROM AUTHOR]

An airlift pump is a vertical tube that utilizes the buoyant effects of a gas to lift a liquid. Unlike a standard mechanical pump, the liquid flow rate through the airlift pump is not directly controlled; rather, it depends on the supplied gas flow rate, the tube length and diameter, and the relative height of the liquid supply free surface (submergence ratio). The present study uses the commercial CFD code ANSYS CFX to model the isothermal, 3D, transient flow in an airlift pump using water and air. The model applies pressure boundary conditions at both ends of the tube and specifies the mass flow rate of air through multiple openings in the side of the tube. The bottom of the tube is an inlet of water only and the outlet is a two-phase flow opening. A time-dependent, homogeneous, VOF two-phase RANS CFD modelling approach is used with the air treated as an ideal gas. This work found that a complete 3D domain was necessary for consistent prediction of the airlift performance and physically realistic two-phase flow structures. Statistical analysis of the two-phase flow structures was applied to characterize airlift pump instability and better understand the physics of the airlift pump. [ABSTRACT FROM AUTHOR]

In fluid dynamics, the Atwood number is a dimensionless parameter that quantifies the density difference between two fluids. It is calculated as A t = (ρ 1 − ρ 2) / (ρ 1 + ρ 2) , where ρ 1 and ρ 2 represent the densities of the respective fluids. This research employs high-fidelity numerical simulations to examine the Atwood number impacts on Richtmyer–Meshkov (RM) flows triggered by a shocked forward-pentagonal bubble. Five distinct gases — SF 6 , Kr, Ar, Ne, and He — are considered within the forward-pentagonal bubble, encompassed by N 2 gas. In these simulations, a third-order discontinuous Galerkin approach is applied to solve a two-dimensional set of compressible Navier–Stokes-Fourier (NSF) equations for two-component gas flows. To discretize space, hierarchical modal basis functions based on orthogonal-scaled Legendre polynomials are employed. This approach simplifies the NSF equations into a set of ordinary differential equations over time, which are solved using an explicit third-order SSP Runge–Kutta algorithm. The numerical results highlight the notable impact of the Atwood number on the evolution of RM flows in the shocked forward-pentagonal bubble, a phenomenon not previously reported in the literature. The Atwood number exerts a significant influence on the flow patterns, leading to intricate wave formations, shock focusing, jet generation, and interface distortion. Moreover, a comprehensive analysis of the these impact elucidates the mechanisms driving vorticity formation during the interaction process. Additionally, the study conducts a thorough quantitative examination of the Atwood number impacts on the flow fields based on integral quantities and interface features. [ABSTRACT FROM AUTHOR]

In this novel study, BaCe 0.9 Y 0.1 O 3– δ , BaCe 0. 9 Eu 0.1 O 3– δ , BaCe 0.9 Nd 0.1 O 3– δ , and BaCe 0.9 Dy 0.1 O 3– δ powders were synthesized by the self-combustion method and processed into thick porous films (60–70 % porosity) to investigate the water vapor sensing properties in the 400–700 °C temperature range. All samples showed a stable response value to water vapor in the whole temperature range, expressed as impedance ratio in dry and wet argon (Z dryAr / Z wetAr), and were able to detect 0.03 vol% of water vapor at 550 °C within the impedance range of 103 Ω at 100 Hz. The response values increased with the partial pressure of water and decreased with the temperature, whereas the maximal value of 3.41 reached the BaCe 0.9 Eu 0.1 O 3– δ sample at 550 °C and p (H 2 O) = 4.28 kPa. The average response time was several seconds and only slightly changed with the material type and experimental conditions. The recovery time depended on temperature and the Z dryAr / Z wetAr ratio, whereas the increase in the gas flow rate from 100 cm3/min to 200 cm3/min significantly reduced the recovery time for the BaCe 0.9 Eu 0.1 O 3– δ sample from 230 s to 55 s at 550 °C and p (H 2 O) = 2.14 kPa. All the samples exhibited stability and a high degree of reversibility after multiple exchanges of wet and dry atmospheres at different temperatures. Yet, their tendency to deteriorate in the presence of CO 2 might challenge a potential application in aggressive environments. [ABSTRACT FROM AUTHOR]

A new design of plasma-assisted injector to ignite or stabilize combustion is presented. This design is intended to produce discharges that penetrate the combustion chamber instead of staying at the wall. This plasma-assisted injector, simple and robust, allows compact designs for a weakly intrusive implementation in engines, and is compatible with either air or fuel, depending on the process or application. A prototype was manufactured, implemented and tested with quasi-DC discharges on the LAPCAT2 Dual Mode Ramjet combustor at LAERTE facility in ONERA. Combustion tests showed earlier ignition and increased pressure when the plasma was turned on with a measured plasma power of 1.4 kW. • Presentation of the design and principle of a new plasma assisted injector. • Demonstration of its ability to generate discharges penetrating the flow. • Characterization of the discharge dynamics and its interaction with the gas flow. • Comparison of the discharge behavior in hydrogen vs air. • Ability of the plasma assistance to enhance supersonic combustion. [ABSTRACT FROM AUTHOR]

Carbon black has been successfully converted into silicon carbide by reacting it with SiO vapor at 1500 °C under Ar gas environment. The influence of reaction temperature, duration and Ar gas flow rate on the final product was examined. The structural and microstructural property of synthesized SiC was characterized using X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). Micrographs of synthesized SiC showed that the final product was an agglomeration of SiC nano-powder of 50–500 nm size and nano-whiskers/fibres having a diameter of 50–500 nm and lengths in 0.1–10 μm depending on Ar gas flow rate. The higher conversion of C into SiC was observed at 1500 °C with Ar gas flow rate ∼250 ml/min. [ABSTRACT FROM AUTHOR]

The utilization of liquid organic hydrogen carrier (LOHC) based on acetophenone has been considered a promising approach for high energy density hydrogen storage, but its industrial application is limited by the low reaction and mass transfer rates observed in conventional reactors. Microreactors have the potential to promote hydrogen storage technology, and, in this study, we propose a tubular reactor coupled with a gas/liquid microdispersion module. Via generating microbubbles prior to the flow of gas and liquid reactants in the tubular reactor, our designed reactor facilitates enhanced gas/liquid interaction mass transfer, thereby improving hydrogenation reaction characteristics. To evaluate the performance of this intensified trickle bed reactor, we investigated the hydrogenation of acetophenone (AP) to 1-phenylethanolis. The results demonstrate that compared to traditional trickle bed reactors, the designed hydrogenation reactor exhibits superior performance under pressures below 2 MPa, with an absence of byproducts, increased conversion and selectivity of AP, and an achieved hydrogen storage rate reaching 0.095 mol H 2 / g Pd / min. [Display omitted] • An intensified hydrogenation reactor was proposed for efficient hydrogen storage. • A gas/liquid micro-dispersion system has been incorporated into a tubular reactor. • The reaction performance of reactors is evaluated using acetophenone hydrogenation. • The intensified reactor shows a nearly twofold increase in hydrogen storage rate. [ABSTRACT FROM AUTHOR]

In urban pipelines, blending hydrogen into natural gas has been considered as an effective way of hydrogen usage to reduce carbon emission on household appliances. However, few studies, especially experimental ones are dedicated to address the characteristics of a typical domestic cooker due to the transition from natural gas to 20%hydrogen-enriched natural gas. This study experimentally investigated the changes in terms of the gas flow rate, flame temperature, heat transfer and emission characteristics of a domestic cooker as a result of such transition. Using a self-developed gas blending system, the flow rates of the both the mixed fuel and its components are obtained. The data shows that after blending hydrogen, the mixed gas flow rate becomes higher. Compared to the original cooker burning natural gas, hydrogen blending results in a decreased natural gas flow rate, leading to lower carbon emission. In addition, the thermal input to the cooker is lowered and hydrogen blending leads both the inner and outer combustion zones of the flame to shorten while the flame temperature to increase. As an attempt to optimize the performance of the cooker, the effects of wok stand height on heat transfer efficiency and NO/NO x /CO emissions are examined. It is found that the cooker fueled by 20%hydrogen-enriched natural gas exhibits lower heat transfer efficiency, higher NO/NO x emissions and lower CO emission. According to the fact that the heat transfer efficiency increases at lower wok stand height, the wok stand height is lowered from its original 7 cm–6 cm and 5 cm. The finding indicates that when the wok stand height is moderately decreased to 6 cm, NO/NO x emissions decrease and CO emission is only marginally increased. This study proposes that when natural gas is replaced by 20%hydrogen-enriched natural gas on a swirl flame cooker, the wok stand height can be slightly lowered to exploit the advantages of blended hydrogen combustion. • A systematic experimental study of the flow/temperature/emission/heat transfer of a cooker. • The changed flow rates are measured by using a self-developed device. • The height of the swirling flame shortens after blending hydrogen to natural gas. • The flame temperature/NOx emission increase while CO emission decrease. • Lowering the wok leads to higher heat transfer efficiency, lower NO x while only marginally higher CO. [ABSTRACT FROM AUTHOR]

Gas explosions mostly occur in turbulent environments in practical situations. Meanwhile, the current research on the explosion characteristics of hydrogen-doped natural gas is mostly methane/hydrogen mixed fuel, ignoring the influence of other components of natural gas on the explosion characteristics of the actual situation. Therefore, the effects of different jet intensities (P jet), hydrogen-doping ratios (X H2) and equivalence ratios (φ) on the explosion characteristics of multi-component natural gas/hydrogen mixed fuel are experimentally investigated in cylindrical tanks of 30 L. Additionally, it extensively explored the dual influence of jet disturbance and gas inerting effect on the flame propagation characteristics of multi-component natural gas/hydrogen mixed fuel. With the increase of P jet , both P max and (d p/ d t) max initially increase and then decrease, while τ continuously decreases. When P jet = 0.4 MPa, the promotion effect on P max and (d p/ d t) max is most significant. The lifting of X H2 leads to a gradual increase in P max and decreasing τ. (d p/ d t) max exhibits a trend of initially increasing and then decreasing with the elevation of X H2 , reaching its maximum at X H2 = 40%. The introduction of jet flow significantly reduces the promotion or inhibition effect on explosions of high hydrogen blending ratio mixtures. Furthermore, the introduction of jet flow is more effective in promoting the explosive performance of multi-component natural gas/hydrogen mixed fuel with high equivalence ratios and low hydrogen doping ratios under rich fuel conditions. This study can provide a key reference for the explosion hazard assessment during the practical application of natural gas/hydrogen mixed fuel. • Hydrogen-doped natural gas is used in explosion experiments collected in real environments. • A gas jet disturbance experimental platform has been established. • The flame propagation characteristics under turbulent conditions have been summarized. • The promotion effect on the explosion is most significant when the jet intensity reaches 0.4 MPa. [ABSTRACT FROM AUTHOR]

This study reports a direct approach to synthesizing vertically aligned carbon nanorod arrays (VA-CNRA) using microwave plasma-enhanced chemical vapor deposition (MW-PECVD) at 300 °C, on cobalt (Co) catalyst nanoparticles grown by thermal annealing (750 °C) of 10 nm thick Co layer deposited by radio frequency (RF) magnetron sputtering. To grow the VA-CNRA, the gas ratio in the plasma was optimized, focusing on the kinetics of the source gas dissociation and recombination. The reduced concentrations of acetylene (C 2 H 2) impede the optimal alignment of CNRA in the absence of the steric hindrance, resulting in their horizontal growth along the direction of gas flow via the "kite-mechanism". However, at a higher gas flow ratio, the attractive van der Waals potential among the CNRs was anticipated to induce aggregation when they arrive in proximity and vertical growth alignment of the nanorods via the higher deposition rates. Carbon nanorod films were analyzed using various spectroscopic techniques to understand the growth orientations, which suggests that the carbon nanorods were formed via the base-growth mechanism. Nano flower-like VA-CNRA were formed at higher C 2 H 2 /H 2 ratios. Notably, a distinct flower-like structure with whisker-like nanostructure petals was formed at a C 2 H 2 /H 2 flow ratio of ∼0.57. Compared to other nanorod structures, VA-CNRA, grown at optimal gas ratio, exhibited superior crystalline graphite, with 76 % sp 2 C C bonding along with a maximum of I 2D /I G , and a minimum of I D /I G intensity ratio in the Raman data. High-resolution TEM confirmed robust growth of CNRs, with an average diameter of ∼370 ± 3 nm. This innovative method enables large-scale production of VA-CNRA with high surface areas for energy applications. [ABSTRACT FROM AUTHOR]

The CH 4 -NH 3 (50%:50%) premixed flame with/without the wall effects are simulated and compared at the stoichiometric condition in this study. The effects of cold wall and local flame dynamics on the flame temperature, heat release rate (HRR), CH 4 /NH 3 oxidations and local CO/NO formations are analyzed quantitatively. Results show that the flame temperature and HRR are decreased and increased respectively along the flame front towards the axis of free flame, but they are both declined significantly towards the wall owing to suppressed chemical kinetics by the heat loss. The negative flame stretch and differential diffusion at the flame tip suppress the CH 4 oxidation and the fast path (NH 3 →NH 2 →NH→N 2) of NH 3 oxidation effectively, but affect the slow path (NH 3 →NH 2 →HNO→NO→N 2) of NH 3 oxidation moderately. This contributes to suppressed CH 4 /NH 3 oxidations and improved NO production at the flame tip of free flame. Based on NRR variations and ROP analysis, compared with CH 4 oxidation, wall heat loss exerts stronger suppressions on the fast path of NH 3 oxidation, while it decelerates the slow path of NH 3 oxidation less evidently. Since the fast path is the primary pathway of the NH 3 oxidation, the NH 3 oxidation suffers more effective suppression of the wall heat loss than the CH 4 oxidation. Furthermore, considering the significance of the slow path to the NO formation, the relatively enhanced importance of the slow path to the NH 3 oxidation in the near-wall region predominates the comparatively effective NO formation in the CH 4 -NH 3 flame compared with the pure CH 4 flame under the influence of wall heat loss. For the CO/NO formations, the local CO production/oxidation in the wall-impinging CH 4 -NH 3 flame are decelerated simultaneously due to the strong heat loss, while the local NO production/destruction are inhibited/improved by the wall heat loss. • The CH 4 /NH 3 oxidizations in the near-wall region are compared and investigated. • The individual/coupling effects of flame dynamics and cold wall are studied. • Different oxidization pathways of NH 3 suffer different influence near the wall. • Major oxidization pathway of NH 3 is weakened more effectively by the cold wall. • CO/NO formations are affected by flame dynamics, wall heat loss and burned gases flow. [ABSTRACT FROM AUTHOR]

Using Ambient Pressure X-ray Photoelectron Spectroscopy (APXPS), this study investigates the reduction behavior of iron oxides in direct reduction (DRI) and blast furnace (BF) pellets. H 2 , CO, and a H 2 –CO mixture are used as reducing agents at 650 °C. The investigation aimed to elucidate variations in the rate of reduction over time and under different conditions. Additionally, contour plots are generated to visualize the X-ray photoelectron peak intensity variations as a function of time. Furthermore, phase stability diagrams based on Fe– O –C and Fe– O –H systems are employed to enhance the understanding of reduction behavior. Results revealed that an increased gas flow rate significantly accelerated the reduction rate due to enhanced gas diffusion, while elevated pressure facilitated the reduction of wüstite to metallic iron. Notably, the DRI pellet achieves around 90% metallization degree reduction with hydrogen, but the introduction of carbon monoxide into the reducing gas prevented the reduction of the DRI pellet. In the case of BF pellet reduction, approximately 20% metallization degree is observed using H 2 –CO (50:50), yet subsequent reoxidation of the reduced iron to wüstite and magnetite occurred. Further investigation identified a significant increase in the partial pressure of H 2 O and CO 2 , particularly within the surface porosities, as the underlying cause of this reoxidation phenomenon. • APXPS used to study iron oxide surface reduction in DRI and BF pellets. • Increased gas flow rate and pressure accelerated reduction rate. • DRI pellet achieved ∼90% metallization with H 2 , however, the value was ∼9% for BF. • BF pellet attained ∼20% metallization with H 2 –CO, while DRI showed no reduction. • Using CO–H 2 , reoxidation observed in BF due to a rise in H 2 O–CO 2 partial pressure. [ABSTRACT FROM AUTHOR]

[Display omitted] • PMOB is an economical solution to reduce landfill CH 4 emissions. • Both single- and two-phase flow models are used for calculating LUGM. • LUGM doesn't reflect gas flow rate into MOL. • A novel PMOB design is proposed with a trapezoidal MOL-GDL interface. • Trapezoidal MOL-GDL interface enhances total gas flow rate into MOL. Passive methane oxidation biosystems (PMOBs) are developed as an innovative and cost-effective solution to reduce methane (CH 4) emissions from municipal solid waste landfills. A PMOB consists of a methane oxidation layer (MOL) and an underlying gas distribution layer (GDL). The length of unrestricted gas migration (LUGM) has been recently proposed as the design criterion for PMOBs where the LUGM is calculated as the horizontal length along the MOL-GDL interface with the volumetric gas content (θ a) exceeding the threshold volumetric gas content (θ a,occ). This paper examined water and gas migration within three PMOBs with different MOL-GDL interfaces subject to precipitation and evaporation using verified numerical models. The results show that the use of a single-phase flow model underestimates the LUGM values of the PMOB for heavy precipitation events, and a two-phase flow model should be used to calculate both the LUGM and the total gas mass flow rate into the MOL when designing PMOBs. Both zig-zag and trapezoidal MOL-GDL interfaces can redistribute the gas mass flow rate at the MOL-GDL interface, while the trapezoidal MOL-GDL interface slightly outperforms the zig-zag MOL-GDL interface for enhancing the total gas mass flow rate into the MOL when comparing with the planar MOL-GDL interface. The zig-zag and trapezoidal MOL-GDL interfaces allow gas migration in the upper part of each PMOB segment even when the lower part of each PMOB segment was filled with water, and thus have a potential to minimize hotspot formation. [ABSTRACT FROM AUTHOR]

The flow of gas and heat transfer in the cylinder of a linear hydrogen engine are key factors affecting the homogeneous mixing of engine fuel and energy conversion. In this article, the effects of injection duration on the blending of the fuel spray, the motion of the vortex and the heat transfer of the linear hydrogen engine are explored on the basis of a new coupled thermodynamic and kinetic model. The results show that between 0.05 ms and 0.25 ms, the overall performance of the engine is best when the injection duration is 0.05 ms. At this time, the eddy current distribution is relatively wide, with a maximum turbulent kinetic energy of 20 m2/s2, which is about 51% higher than that at 0.25 ms. The indicated thermal efficiency and cumulative heat release have also reached their maximum values at this time. The heat transfer coefficient and heat flux rate are 16.7% and 33.2% higher than 0.25 ms, respectively. In terms of emission, with the increase of fuel injection duration, incomplete combustion of fuel in cylinder makes Soot emission increase. Taken together, an injection duration of 0.05 ms is the most appropriate. • The effect of diesel pilot hydrogen technology in linear engine is analyzed. • A coupled kinetic and thermodynamic model for heat transfer simulation is used. • Reducing the injection duration can enhance the airflow movement in the cylinder. • The shorter the injection time, the higher the heat transfer loss. [ABSTRACT FROM AUTHOR]

Ammonia decomposition is a key technology for its use as a hydrogen carrier and in the recovery of H 2 from waste streams containing ammonia. The coupling of the catalytic decomposition of ammonia with an H 2 permeoselective membrane improves the process by mitigating thermodynamic constraints and producing a flux of high-purity hydrogen, not requiring further separation/purification. In this study, we compare the behaviour of an eggshell catalyst 1.3 wt % Ru/Al 2 O 3 catalyst in a packed bed reactor (PBR) and a packed bed membrane reactor (PBMR) using an ultrathin Pd membrane (3.4 μm). Tests were made at 11 bar(a) with a weight hourly space velocity of NH 3 in the 0.560–1.68 Lꞏg−1ꞏh−1 range and temperatures of 350–400 °C, e.g. milder conditions than the conventional ammonia cracking catalysts. Under optimised conditions (0.56 Lꞏg−1ꞏh−1, 400 °C, sweep gas flow 0.55 L min−1), the PBMR shows excellent performance, achieving NH 3 conversion, H 2 productivity and recovery factor of 99%, 47 mmol H2 ·g Ru −1·min−1, and 94.9%, respectively. PBMR increases by ∼50% the conversion rate compared to PBR. Without a sweep gas, PBMR performances are lower, even still higher than in PBR. For the first time, superior or comparable performance was demonstrated compared to similar systems using pure ammonia in terms of conversion, hydrogen recovery, H 2 productivity, and Ru utilisation. These results can be further enhanced with vacuum systems to convert diluted ammonia streams into high-purity hydrogen for small-scale distributed systems and can be extended to other reactions. • An egg-shell Ru/Al 2 O 3 with an ultra-thin Pd membrane achieved 99% NH 3 conversion at 400 °C in PBMR, outperforming PBR. • Ultra-thin Pd membranes and sweep gas allow 94.88% H 2 recovery factor by decomposition of diluted ammonia. • Dilute NH 3 can improve safety and decrease noble metal usage, offering economic and environmental benefits. [ABSTRACT FROM AUTHOR]

In rarefied gas dynamics, the Cercignani-Lampis (CL) scattering kernel, containing two accommodation coefficients (ACs), namely the tangential momentum and normal energy ones, is widely employed to characterize gas-surface interaction, particularly in non-isothermal setups, where both momentum and energy may simultaneously be exchanged. Here, a formal and detailed sensitivity analysis of the effect of the CL ACs on the main output quantities of several prototype problems, namely the cylindrical Poiseuille, thermal creep and thermomolecular pressure difference (TPD) flows, as well as the plane Couette flow and heat transfer (Fourier flow), is performed. In each problem, some uncertainties are randomly introduced in the ACs (input parameters) and via a Monte Carlo propagation analysis, the deduced uncertainty of the corresponding main output quantity is computed. The output uncertainties are compared to each other to determine the flow configuration and the gas rarefaction range, where a high sensitivity of the output quantities with respect to the CL ACs is observed. The flow setups and rarefaction regimes with high sensitivities are the most suitable ones for the estimations of the ACs, since larger modeling and experimental errors may be acceptable. In the Poiseuille and Couette flows, the uncertainties of the flow rate and shear stress respectively are several times larger than the input uncertainty in the tangential momentum AC and much smaller than the uncertainty in the normal energy AC in a wide range of gas rarefaction. In the thermal creep flow, the uncertainty of the flow rate depends on the input ones of both ACs, but, in general, it remains smaller than the input uncertainties. A similar behavior with the thermal creep flow is obtained in the TPD flow. On the contrary, in the Fourier flow, the uncertainty of the heat flux may be about the same or even larger than the input ones of both ACs in a wide range of gas rarefaction. It is deduced that in order to characterize the gas-surface interaction via the CL ACs by matching computations with measurements, it is more suitable to combine the Poiseuille (or Couette) and Fourier configurations, rather than, as it is commonly done, the Poiseuille and thermal creep ones. For example, in order to estimate the normal energy AC within an accuracy of 10 %, experimental uncertainties should be less than 4 % in the thermal creep or TPD flows, while may be about 10 % in the Fourier flow. [ABSTRACT FROM AUTHOR]

The effect of external gas injection near the plume on the performance of a microwave discharge cathode is investigated. Experiments were conducted under two gas injection conditions: gas addition and gas distribution. Gas distribution tended to lead to better performance than gas addition. In the gas distribution experiments, the total gas consumption was kept constant, the internal gas flow rate was reduced, and external gas was supplied. The electron current increased from 0.26 to 0.49 A at 35 V when the microwave power was 15 W. When the sum of the internal and external gas flow rates was held constant, external gas injection lowered the neutralization costs and increased the gas utilization efficiency. The neutralization current was successfully increased by 48 % at 12 W of microwave power compared with 8 W of microwave power with the same level of naturalization cost and gas utilization efficiency. The electron temperature and plasma density in the plume, as measured using a Langmuir probe, suggested that an increase of ionization in the plume by the external gas injection enhanced the cathode's performance. • Supplying gas into the plume of a microwave discharge cathode improves its performance. • Neutralization current increased by 58 % with external gas injection. • External gas injection decrease naturalization cost and increase gas utilization efficiency. • An increase of ionization in the plume by the external gas injection enhanced the cathode's performance. [ABSTRACT FROM AUTHOR]

The utilization of hydrogen as an energy carrier faces a challenge due to its limited presence in its pure form in the Earth's atmosphere, necessitating its extraction from various sources. Among hydrogen production methods, microwave-induced plasma molecular cracking shows promise as an alternative. This review explores how different operational parameters of a microwave-induced plasma system with gas-phase discharge impact hydrogen production performance. Performance indicators include hydrogen production rate, energy yield, and final hydrogen concentration. Parameters influencing hydrogen production encompass microwave power, gas flow rate, initial hydrogen concentration, steam addition, gas injection method, and plasma-forming gas type. Other vital system parameters are also discussed. Higher absorbed power leads to increased hydrogen production, albeit less efficiently. Elevated carrier gas flow rate reduces residence time, consequently lowering performance, while higher fuel gas flow rates enhance hydrogen production. Introducing steam can enhance indicators and reduce soot, and injecting fuel gas directly into the plasma torch tip yields optimal hydrogen production. Avoiding excessive power, fuel gas flow, or water vapor is important, as hydrogen saturation can limit further performance enhancement. • Microwave-induced plasma appears as a promising alternative for H 2 production. • Operational parameters' impacts on the system performance were analyzed. • Steam addition and gas injection methods' impacts on H 2 production were discussed. • Optimal practices for enhanced H 2 production were determined. [ABSTRACT FROM AUTHOR]

In order to explore the thermodynamic characteristics of the gradual cooling and liquefaction process of hydrogen, a small-scale open hydrogen liquefaction system with stepwise cooling is proposed, designed and experimentally tested. The fabrication and practical cooling operation of the hydrogen liquefaction system are conducted under the premise of pre-test of neon and safety precautions. The cooling capacity required for hydrogen cooling is continuously provided by two Gifford-Mcmahon (G-M) refrigerators and the returned cold hydrogen. The hydrogen gas is gradually cooled to about 21 K through two pre-cooling heat exchangers (PHEX) and three counter-flow heat exchangers (CHEX) and then throttled to about 120 kPa. Hydrogen gas with a mass flow rate of 0.2 kg/h can be liquefied to meet the design requirements in this system and the experimental results are compared with the Hysys simulation. The comparative analysis reveals that the measured data of key nodes are in good agreement with the simulation results, and the maximum deviation is around 8.70%, which proves the effectiveness of the experimental system and provides validation for the simulation. In addition, the design of the heat transfer module including the structure of the PHEX and the cold shield is reasonable and feasible. In conclusion, the designed experimental system and results can provide a technical reference for the corresponding equipment selection and operating experience in hydrogen liquefaction experiments. • A small-scale open hydrogen liquefaction system with stepwise cooling is proposed. • The temperature is divided into three zones and the throttling process is retained. • A heat transfer module is designed to enhance the heat transfer performance. • Standard operation procedures and safety precautions are conducted to ensure safety. • The experiment data and simulation results are compared to verify the feasibility. [ABSTRACT FROM AUTHOR]

Solid oxide fuel cells (SOFCs) can directly convert the chemical energy in fuels and oxidants into electrical energy because of their high operating temperatures, making them efficient and environmentally friendly. The high-temperature operating characteristic gives SOFCs numerous advantages, including flexible fuel capability and high efficiency. However, it leads to a non-uniform temperature distribution that results in the performance degradation of SOFCs or even system failure. Owing to the high-temperature and gas-sealed operating environment, measuring the temperature distribution in SOFC stacks using experimental methods is extremely difficult. In this study, an SOFC internal temperature measurement device is developed and constructed to investigate the impacts of various factors, including the operating current density and gas flow rate, on the electrical output performance and temperature distribution within an SOFC stack. The experimental results indicate that the SOFC temperature gradually increases with increasing current density. Furthermore, the temperature difference between the spatial locations increases, and the inhomogeneity of the temperature distribution becomes more significant. During the growth of the current density i from 0.1 A/cm2 to 0.5 A/cm2, the maximum temperature gradient on the SOFC electrodes reaches the lowest level at i = 0.3 A/cm2. The maximum current density and power density increase as the gas flow rate increases. However, the electrical efficiency and fuel utilization ratio gradually decrease, and the uniformity of the temperature distribution deteriorates. Air flux is the main factor that dominates the temperature distribution in SOFCs. The temperature on the cathode side is higher than that on the anode side. These results contribute to understanding the temperature distribution patterns in SOFCs and provide some guiding significance for SOFC design and operation optimization. • The real working temperature during SOFC operation was measured experimentally. • The optimal current density minimizes the temperature gradient on the SOFC anode. • Air flux is the main factor dominating the temperature distribution in SOFCs. • The cathode/anode temperature difference is not significant at low current density. • The temperature difference between the cathode/anode cannot be ignored at high current density. [ABSTRACT FROM AUTHOR]

A transient pipeline flow model with gas composition tracking is solved for studying the operation of a natural gas pipeline under nonisothermal flow conditions in a hydrogen injection scenario. Two approaches to high-resolution pipeline flow modeling based on the WENO scheme are presented and compared with the implicit finite difference method. The high-resolution models are capable of capturing fast fluid transients and tracking the step changes in the composition of the transported mixture. The implicit method assumes the decoupling of the flow model components in order to enhance calculation efficiency. The validation of the composition tracking results against actual gas transmission pipeline indicates that both models exhibit good prediction performance, with normalized root mean square errors of 0.406% and 1.48%, respectively. Under nonisothermal flow conditions, the prediction response of the reduced model against a high-resolution flow model, with respect to the mass and energy linepack, is at most 3.20%. [Display omitted] • Two approaches to high-resolution pipeline flow modeling based on the WENO scheme are presented. • The solutions are capable of capturing fast fluid transients and tracking natural gas-hydrogen mixture composition. • High-resolution solutions are compared to the solution with the implicit finite difference method. • The effect of hydrogen injection on pipeline mass and energy linepack is studied in detail. [ABSTRACT FROM AUTHOR]

a -axis-oriented AlN(100) films are identified as promising candidates for surface acoustic wave devices owing to their high transversal-acoustic velocity. Achieving uniform films across a wafer scale is crucial for enhancing device performance and minimizing manufacturing costs. In this study, we employ radio-frequency magnetron sputtering to deposit AlN(100) films on 2-in Si(100) wafers. We further examine the influence of various process parameters on the nonuniformity of film thickness and structural properties, including crystallite size, microstrain, and dislocation density. The optimization of parameters leads to the selection of a gas flow ratio of N 2 :Ar = 4:7, a sputtering power of 160 W, and a substrate temperature of 350 °C. Under these optimized conditions, the AlN films not only demonstrate a preferred (100) orientation and remarkable crystallinity, as indicated by a full width at half maximum of the X-ray diffraction peak of just 0.03°, but also achieve an optimal film thickness nonuniformity of 1.66 %. Our results offer valuable insights for the wafer-scale fabrication of AlN(100) films, potentially enhancing industrial production yields and reducing costs. [ABSTRACT FROM AUTHOR]