Search

The target surface to be treated in reality is often not smooth and horizontal and may also be in different tilting angles. The treatment of the tilted dielectric surface by the atmospheric pressure plasma jet (APPJ) undoubtedly increases the complexity of surface modification. Therefore, a two-dimensional fluid model is established to reveal the internal mechanism of the interaction between the He APPJ and the tilted dielectric surface by means of numerical simulation. The distribution of the gas flow in a small angular range (0°, 3°, 5°, 8°, 10°, and 15°) is studied. In addition, the effects of the tilt angle on the jet morphology, discharge dynamic properties, and species distribution of the He APPJ are emphatically discussed. It is found that the jet morphology and parameters are no longer symmetrical under the tilted surface. With the increase in the tilt angle, the enhanced electric field in the upper surface region leads to the increase in the ionization rate and electron density here, and also accelerates the propagation speed of the jet to the dielectric surface in the atmospheric environment. Driven by the electric field force, the jet is closer to the dielectric surface, resulting in a decrease in the thickness of the cathode sheath and an increase in the surface charge density in the area to the right of the central axis. The influence of the gas flow structure leads to the shortening of the jet development distance and a decrease in the jet velocity on the upper surface. N and O also form higher fluxes on the upper surface due to the increase in the electron density. [ABSTRACT FROM AUTHOR]

A reduced pressure glow discharge is produced by passing a high-power pulsed DC source of 0–500 W with a frequency of 50 Hz across two parallel disk electrodes. A hydrogen peroxide aqueous solution is used as a flowing gas for discharge generation. Optical emission spectroscopy is employed to diagnose the discharge generated at a reduced pressure of 0.2 mbar with an electrode gap of 4 cm. The spectra are recorded at a power density of 9.4 mW/cm3 and typically lie in the visible wavelength range of 380–880 nm. The spectra are analyzed using the line intensity ratio method to estimate electron temperature and density. The results indicated that the electron temperature and density are, respectively, 0.87 eV and 6.4 × 1014 cm−3. [ABSTRACT FROM AUTHOR]

The microwave electrothermal thruster (MET) utilizes wave-exited microdischarges to heat gas flows, enhancing the specific impulse of the thruster. Our computational study investigates a 17.5 GHz helium-propellant MET, employing a two-dimensional, axisymmetric fluid model of plasma coupled with electromagnetic wave and gas flows. The discharges operate in the glow regime, remaining weakly ionized, and in thermal non-equilibrium. The plasma densities reach approximately 10 20 m − 3 , and the gas temperature is around 2000 K. Even a slight off-resonant frequency operation results in a significantly lower plasma density and gas temperature. Gas heating, primarily driven by electromagnetic Joule heating, plays a critical role in influencing the overall discharge behavior. The measured peak thrust and specific impulse are 8.24 mN and 292 s, respectively, at a mass flow rate of 3.2 mg/s with 30 W of power. Compared to a cold gas thruster, there is a significant increase in the specific impulse by a factor of approximately 1.7. The enhanced performance trades off with propulsive efficiency, which decreases by a factor of 1.5 from the peak 65% at 10 W. This is due to higher energy losses to cavity walls from heat conduction with increased power. These findings underscore the critical balance between the input power and mass flow rate to improve the MET performance, highlighting the importance of power management to maximize thrust and efficiency. Furthermore, the predicted thrust and specific impulse agree well with experimental values for nominally similar MET thruster studies in the literature. [ABSTRACT FROM AUTHOR]

Photothermal spectroscopy, and more specifically photothermal interferometry (PTI), is a highly sensitive technique for measuring gas and aerosol concentrations. Numerous implementations of different PTI configurations have demonstrated the versatility of the technique. This theoretical study presents a comprehensive analysis and an optimization of the PTI optical path length (OPL) amplitude using characteristic times. We investigate how the OPL amplitude depends on the dimensions and orientations of the interferometer laser beam and the continuous-wave excitation laser beam. This analysis quantifies the impact of advection on the OPL amplitude based on the relative orientation of the two laser beams and the gas flow direction. It is analytically shown that the possibilities for photothermal OPL amplitude optimization are limited when thermal diffusion is dominant. Theoretically, advection has the potential to double or cancel the OPL amplitude, depending on the specific configurations. In summary, we provide an in-depth understanding of the design and parameter considerations required when tailoring and optimizing a PTI sensor for different fields of applications. [ABSTRACT FROM AUTHOR]

As volatile organic compounds (VOCs), gaseous ethylbenzene has adverse effects on human health and ecology. Therefore, an effective degradation process is highly desirable. The Fenton process under UV 365 nm was selected as the first option to remove gaseous ethylbenzene in a bubble column reactor. The main parameters for the batch experiments were systematically studied, including H2O2 concentration, [H2O2]/[Fe2+], pH, UV wavelength, UV intensity, gaseous ethylbenzene concentration, gas flow rate, and process stability towards removal efficiency. The optimum conditions were found to be H2O2 concentration of 100 mmol·L−1, [H2O2]/[Fe2+] of 4, pH of 3.0, UV wavelength of 365 nm, UV power of 5 W, gas flow rate of 900 mL·min−1, and gaseous ethylbenzene concentration of 30 ppm, resulting in a removal efficiency of 76.3%. The study found that the Fenton process, when coupled with UV 365 nm, was highly effective in removing gaseous ethylbenzene. The degradation mechanism of gaseous ethylbenzene was proposed in the UV365/Fenton process based on EPR, radical quenching experiments, iron analysis, carbon balance, and GC-MS analysis. The results indicated that •OH played a crucial role in the process. [ABSTRACT FROM AUTHOR]

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]

Introduction: Soil gas permeability is critical to the study of soil pore structure, soil gas transport, and crop growth. Methods: In this paper, a pressure decay method is proposed to calculate soil gas permeability based on the law of conservation of mass, which is measured and compared with the steady-state method in a variety of soils, including compacted soils and soils with different moisture contents. The applicability of the two methods and the effects of compaction and water content on soil gas permeability were explored. Results: The experimental results show that in low-permeability soils, there is a bias in the measured values of the steady-state method. In contrast, the results calculated based on the pressure decay method are more accurate. Increasing the water content of the soil or compacting the soil results in a 20%–88% or 63%–93% decrease in soil gas permeability, respectively, with the degree of decrease correlating with the viscosity of the medium. Discussion: The findings show that calculating soil gas permeability based on the pressure decay method helps compensate for the inaccuracy of the steady-state method in measuring results in low-permeability soils. This leads to a better evaluation of soil aeration conditions, which, in turn, serves environmental, agricultural, and ecological research. [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]

Background: The Rapid-O2 oxygen insufflation device® (Rapid-O2) was designed primarily for rescue oxygenation in cannot intubate, cannot oxygenate (CICO) events; thus, hypercapnia is inevitable. Rapid-O2 was modified to enhance ventilation using the Venturi effect during expiration. Methods: To determine the most effective combination of inner catheters (20 gauge [G], 18 G, 16 G, 14 G, and 2-mm inner diameter [ID] transtracheal catheter [TTC]) and insufflation catheters (16 G, 14 G, and 2-mm ID TTC) for achieving optimum ventilation, insufflating and expiratory flows were measured at an oxygen flow rate of 15 L/min. The insufflating and expiratory pressures were measured at 6-15 L/min. The flows and pressures were measured using a gas flow analyzer. The insufflating and expiratory times were measured using a trachea-lung model to obtain minute volumes. To assess the improvement by modifying the Rapid-O2, minute volumes were measured using the Rapid-O2. Results: The most appropriate inner catheter was 18 G. The insufflating pressures ranged from 97 (2-mm ID TTC) to 377 cmH2O (16 G) at 15 L/min. During expiration, similar negative pressures of 50 cmH2O were measured in the insufflation catheters at 15 L/min. At lung compliance of 100 ml/cmH2O, the minute volumes through a 2-mm ID and 14 G insufflation catheters were 7.0 and 5.37 L/min, respectively, at 15 L/min. The minute volumes were significantly greater in modified Rapid-O2. Conclusions: Modified Rapid-O2 provided sufficient minute volumes in adults using a 14 G or 2-mm ID insufflation catheter at 15 L/min, demonstrating its potential for ventilation in CICO events. [ABSTRACT FROM AUTHOR]

3-D numerical simulations based on diffusion combustion technology were employed to optimize the multi-stage air/gas supply system in a coke oven battery with 7.1 m coking chambers. In the heating flues, the Eddy-Dissipation Concept (EDC) model and the ideal gas model were utilized to numerically investigate diffusion combustion. What is more, the radiation between the flue gas and the silicon brick was calculated using the Discrete Ordinates (DO) model. After validating the reliability of the model with field-measured data, insights into the temperature field and gas flow in the heating flue, and heat flux distribution over the heating wall were obtained. To characterize the vertical heating uniformity, an index of the standard deviation of the heat flux over the vertical heating walls was proposed. By optimizing the multi-stage air/gas supply design of heating flues, the vertical heating uniformity was improved by 60% according to the index values. The approach developed in this work can be a useful tool for the design of large-capacity coke oven batteries at different scales. [ABSTRACT FROM AUTHOR]

This paper presents the construction of a high-quality, robust hybrid grid for near-wellbore modeling in the vicinity of a deviated well. The far-field region is modeled using a cornerpoint grid, while the near-wellbore region-referred to as the volume of interest-is remeshed using a layered unstructured grid, which consists of a combination of Voronoi and radial sub-grids. A detailed gridding and simulation workflow is outlined. The construction of the novel layered unstructured grid begins with building a base surface grid on the surface typically aligned to middle well point. The grids on the other surfaces are built through preserving the base topology but adjusting the nodes of base grid to fit the well points deviating from the base well point. A flow-based node rearrangement method is proposed to adjust the grid nodes to gain high-quality grids on each surface. The positions of new nodes are determined by ensuring equal streamlines and pressure values between nodes on the base and target surfaces, improving grid orthogonality as streamlines remain perpendicular to equipotential lines. The method's ability to generate high-quality grids for deviated wells is demonstrated through illustrative and validation examples. Computational performance is assessed through direct comparisons across three case studies, showing that the new near-wellbore modeling model provides accurate well solutions and pressure maps with a reasonable computational cost. Additionally, the near-wellbore modeling model outperforms standard models in capturing gas flow with high compressibility, describing flow behavior in heterogeneous reservoirs, and predicting production parameters in multilayer systems. [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]

In this work, a foam composed of helical carbon nanofiber arrays was successfully synthesized via chemical vapor deposition. By controlling synthesis parameters including the synthesising temperature and gas flow rate, carbon nanofibers with straight, kinked, and spring-like morphologies were obtained. Adjusting the precursor feed led to the formation of foams with well-ordered carbon nanofiber structures. The nanofibers exhibit diameters ranging from 98 to 175 nm and lengths extending to the centimetre scale. Experimental results confirm that these fibers are organic carbon nanofibers, attributed to low-temperature catalytic synthesis. Structural characterization reveals that the catalyst assumes a regular polyhedral shape and becomes embedded within the fibers, which symmetrically grow from both faces of the catalyst. Structural analysis indicate that the carbon nanofibers are hollow, multi-walled structures with numerous defects. The resulting foam demonstrates porous, along with excellent elasticity and high mechanical strength. [ABSTRACT FROM AUTHOR]

In this paper, the effect of the process parameters such as laser power, shielding gas flow and scanning velocity on the actual laser power reaching the surface and thermal efficiency is investigated. For this purpose, the response surface methodology was used to investigate the effect of the process parameters at three levels. In order to measure the data from a 316L stainless steel, four k-type thermocouples are installed in different positions relative to the motion of the laser beam. The actual power was calculated by reverse analysis using the simulated annealing technique and the temperature history was measured by the thermocouples. The thermal model used is an optimized Rosenthal model, which is considered variable with temperature. The results show that for all thermocouples, the highest values of actual power that reached the surface were obtained at laser power of 200 W, scanning velocity of 2 mm/s and shielding gas flow of 30 Lit/min. In addition, by increasing the laser power from 100 to 200 W, the thermal efficiency decreases by about 4% to 12%. The thermal efficiency also decreases by about 8%, when the scanning velocity increased from 1 to 3 mm/s. Moreover, the increase of the shielding gas flow from 25 to 35 Lit/min initially improved the thermal efficiency and then decreased it. The models obtained from the analysis of variance in the heating cycle are in good agreement with the experimental results, but in the cooling cycle, the accuracy of this model decreases. [ABSTRACT FROM AUTHOR]

The oxidation of ammonium sulfite must be inhibited to improve the economy and cycle performance of the ammonia flue gas desulfurization process. A stirred bubbling reactor was used to investigate the macrokinetics of oxidation inhibition of ammonium sulfite by sodium thiosulfate in wet ammonia desulfurization. The effects of initial SO32−${\rm SO}^{2-}_{3}$ concentration, Na2S2O3 concentration, pH value, gas flow rate, and temperature on the oxidation rate were discussed. The results show that the apparent activation energy of the reaction is 37.3 kJ/mol. The macrokinetics equation of sodium thiosulfate inhibiting sulfite oxidation in the ammonia desulfurization process was established. Combined with the kinetic model, it is inferred that the rate of sodium thiosulfate inhibiting ammonium sulfite oxidation is controlled by the intrinsic chemical reaction. The results can provide a reference for the regeneration of ammonium sulfite in the wet ammonia desulfurization process. [ABSTRACT FROM AUTHOR]

The erosion of elbows in shale gas-gathering pipelines is influenced by both internal tensile stress and solid particle erosion. However, scholarly attention to the occurrence of elbow erosion in such pipelines under stress is lacking. To address this gap, this study establishes a numerical model accounting for the two-way coupling between elbows and natural gas under internal pressure while also considering particle erosion under stress. Numerical simulations were conducted to analyze the erosion behavior of elbows under varying gathering pressures, gas flow rates, and particle sizes. The results indicate that the location of maximum stress coincides with the position of the highest erosion rate, suggesting that stress concentration renders the material highly susceptible to erosion. Additionally, an increase in collector pressure exacerbates the impact of stress on the erosion process. Gray-scale correlation analysis subsequently identifies the priority order of factors influencing the maximum erosion rate in the elbow as follows: collector pressure has the highest influence, followed by gas flow rate, and then particle size. [ABSTRACT FROM AUTHOR]

As a novel coating spray technique, the aerosol deposition method is applied for the fabrication of dense, nanostructured ceramic coatings at room temperature via an impact consolidation mechanism. It is widely recognized that the successful deposition of coatings is strongly dependent on processing parameters during the deposition process. In this study, a brush‐type aerosol generator was employed to enhance the continuity and stability of the aerosol supply. The uniformity of powder consumption at different packing densities was evaluated; an optimal loading density of 33% was identified for the alumina powders used in this study. Both simulation and experimental studies were performed to investigate the influence of gas flow rate and standoff distance (SoD) on coating fabrication and properties. The predicted particle impact velocity increased with increasing gas flow intensity and SoD, resulting in enhanced mechanical properties of the coatings, including adhesive strength and hardness. The maximum compressive residual stress value of 389 MPa was determined for an alumina coating fabricated at a gas flow rate of 20 L/min. [ABSTRACT FROM AUTHOR]

The complex disaster of gas and coal spontaneous combustion is a major challenge in coal gob, especially under conditions of three-dimensional extraction. Taking the 15,101 mining face in Shigang Mine as the field background, COMSOL Multiphysics software was employed to construct models of airflow, methane migration, and stress distribution in gob under the stereo extraction method of "U+high-low level roadway." The range of oxidation zone was divided by combining the oxygen concentration and wind velocity field. The results showed that the methane can be discharged through the low-level airway and the return airway, and most of the methane at the top area in gob can also be discharged from the high-level roadway, indicating that the stereo ventilation was beneficial for methane dilution at both the upper and lower region. However, the oxidation zone in the middle of gob was the widest and closed to the mining face, it on the return side was narrower than intake side, and its distribution range was closer to the mining face. And finally, the range of the oxidation zone expanded with the increase in height in the vertical direction. These indicate the dangerous area for preventing gas and coal spontaneous combustion disasters in gob. [ABSTRACT FROM AUTHOR]

Liquid holdup is a crucial factor in the study of hydrodynamic behaviors in the micro‐packed bed reactor (μPBR). In this work, the values of liquid holdup are studied with the weighing method with good accuracy. The packed bed is a tube made of stainless steel with a length of 20 cm and an inner diameter of 4 mm, packed with 177–250 μm or 350–500 μm microbeads. The gas and liquid flow rates vary from 5 to 20 mL/min and 0.25 to 2 mL/min, respectively. A new hypothesis of the flow regions is proposed based on the experimental results. Furthermore, a new set of empirical correlation is built with great agreement, particularly for viscous liquids, whose viscosity ranges from 0.99 to 5.98 mPa·s, showing an atypical tendency. [ABSTRACT FROM AUTHOR]

Classic oxidation often entails parabolic, diffusion-controlled scale growth. In aggressive environments, linear scale volatility may occur, resulting in paralinear oxidation. Tedmon kinetics were fitted to show weight change vs time with oxide type, growth rate (kp), and volatility rate (kv). 25 model cases were represented by one plot when normalised by weight (½ kp /kv) and time constants (½ kp /kv2), and stoichiometry, as embodied in weight change and time to achieve a maximum. Convergence illustrates functional commonality for widely divergent behaviours. Example curves are presented for Ti2AlC, Ni-40Cr, SiC, Si3N4, BN, and Pb oxidised in slowly flowing gas or burner environments at 300° − 1300°C. The raw data, show wide variations, but converge to a single curve when normalised. This single universal function thus represents all paralinear oxidation behaviour. [ABSTRACT FROM AUTHOR]

Efficient separation of residual carbon and ash in coal gasification fine slag is of great significance for clean utilization of coal, resource conservation, and environmental protection. In this study, a novel corona charging approach was proposed to enhance particle charging and improve the electrostatic separation efficiency of coal gasification fine slag. A multiphysical model was established to investigate the coupling effects of the electrostatic field, gas flow field, and particle charging behavior. The results showed that, under the effect of positive DC corona on particle charging, the electric field voltage was positively correlated with the charge-to-mass ratio (CMR) of the particles. As the particle size increased, their charge amount increased, while the CMR decreased. The inlet gas velocity obviously affects the charging time of particles, resulting in a decrease in the average CMR with increasing gas velocity. Comparative experiments revealed that implementing corona charging promoted the decarbonization efficiency and carbon recovery efficiency (REC) by 17.99% and 23.66%, respectively, significantly improving the electrostatic separation of carbon and ash particles in coal gasification fine slag. [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]

In the winter, a certain LNG receiving terminal operates exclusively with the submerged combustion vaporizer (SCV). However, due to the high operational costs associated with the SCV, a new combined operation scheme utilizing both the SCV and the open rack vaporizer (ORV) has been proposed. First, models for the SCV and ORV gasification units were developed in Aspen HYSYS and validated using actual operational parameters. Next, the relationship between the seawater inlet–outlet temperature difference and the minimum seawater flow rate for the ORV was determined, and an optimized seawater pump operation strategy, considering LNG export volumes, was formulated. Additionally, the relationship between the SCV fuel gas flow rate and LNG export volume was analyzed, and a comparison was made between the operating costs of SCV running independently and the combined SCV-ORV operation under winter conditions. The results of the combined operation experiments indicated that at a seawater inlet–outlet temperature difference of 3 °C, the joint operation mode could save costs by 70–77%; at 2.5 °C difference, it saves 60–67%; at 2 °C difference, it saves 45–50%; at 1.5 °C difference, it saves 35–38%; and at 1 °C difference, it saves 20–23%. This approach achieves optimized economic performance for LNG terminal operations. [ABSTRACT FROM AUTHOR]

In this study, the transportation of reactive species from argon (Ar) and helium (He) atmospheric-pressure plasma jets (APPJs) to water is comparatively investigated using two-dimensional (2D) fluid models. For the same gas flow rate and reactive species concentration at the jet orifice, the transportation efficiency of the Ar APPJ is found to be higher than that of the He APPJ by 3.7 times. This is primarily attributed to the difference in the gas flow between the Ar and He APPJs. Ar has a higher molecular weight than air, which allows the reactive species in the Ar gas flow to sufficiently contact the water surface. He is much lighter than air, and consequently, the He gas flow floats upwards and inhibits transportation. Increasing the gas flow rate can reduce the floating of He and enhance the transportation of all reactive species in the He APPJ, but can only improve the transportation of short-lived species in the Ar APPJ. The use of shielding air gas reduces the floating of He and promotes the production of reactive species in the plasma plume, thus, the normalised concentration of the reactive species in the He APPJ-treated water increases drastically by 30.3 times. The numerical results conform to the trends observed in the available experimental data, which explains the reason why the Ar APPJ has stronger sterilization and anticancer effects than the He APPJ. The findings also serve as a reference for improving the He APPJ for biomedical applications. [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]

Aerosol jet printing (AJP) is a cutting‐edge additive manufacturing technique, ideal for fabricating conformal electronics due to its extended working distance, simplicity, and environmental sustainability. However, achieving optimal resolution is hindered by complex interactions between aerosol droplets and substrates, as well as the influence of various process parameters. This study focuses on precise AJP control to enable high‐resolution conformal electronics fabrication. Through randomized single‐factor experiments, the effects of gas flow rates, focusing ratio, and print speed, highlighting the role of back pressure on focusing limits are examined. A computational fluid dynamics model, incorporating accurate particle size data, predicts aerosol stream width to expedite operating window identification. The interaction mechanisms between aerosol droplets and substrates are elucidated, achieving a resolution of 5 µm. A precision manufacturing protocol is developed, ensuring high‐quality features with resolutions ranging from 10 to 300 µm across diverse 3D substrates without overspray. The successful integration of a heater, temperature sensor, and display demonstrates AJP's potential for multi‐functional conformal electronics. [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]

We designed a MEMS microvalve based on the nanoscopic electrostatic drive (NED) technology (Nat Commun 6:10078, 2015). NED actuators, electrostatically controlled bending beams, are implemented in a clamped-clamped configuration. A normally open plunger valve was designed and characterized. The device is manufactured from silicon. Gas flow rates of up to 37 SCCM can be proportionally controlled between 10% and 100%. A 10% leakage is always present at low backpressures (< 10 kPa) and increases to roughly 20% at 75 kPa backpressure. The structure has been tested up to backpressures of 300 kPa without damage to the structures, but the leakage increases to over 95%. Our unprecedented microvalve concept shows that it is possible to manufacture all-silicon MEMS microvalves with proportional control of the flow rate. The presented work is a proof of concept to test the capabilities of the NED technology for the use in microvalves. There are plans to decrease the leakage in future designs by introducing an additional sealing layer as well as manufacturing a shutter instead of a plunger design. [ABSTRACT FROM AUTHOR]

Gas drilling technology remains a superior method for discovering and protecting oil and gas reservoirs in the petroleum exploration and development industry. However, its widespread application and further advancement have been significantly hindered by safety risks associated with surface equipment. Owing to the constraints of mountainous terrain, the connection of the blooie line inevitably adopts multiple elbow connections. As a result, aerodynamic flutter will occur when high-speed gas flow enters the blooie line, which threatens drilling safety. In this study, a series of comprehensive two-way fluid–structure interaction numerical simulations are conducted on the blooie line with multiple bends to determine its structural responses of the aerodynamic flutter induced by a sudden high-speed gas flow during gas drilling. The results suggest that a large quantity of rock cuttings and rock fragments, suddenly ejected when a high-production reservoir was unexpectedly encountered during drilling, tends to accumulate at the bends, leading to blockages and a reduction in the circulation area. This blockage is found to expose the blooie line to a significant risk of fracture, thereby threatening its structural integrity. The higher the gas production, the more severe the aerodynamic flutter of the blooie line. To address the challenge of blockage on the flutter, novel tank equipment is designed to effectively manage the sudden ejection of massive cuttings, aiming to prevent abrupt blockages in the blooie line during the drilling process. The application of this equipment, integrated into the blooie line, ensures the safety of gas drilling operations. [ABSTRACT FROM AUTHOR]

The article presents the results of visualization of two-stream gas targets for a point source of vacuum ultraviolet and extreme ultraviolet radiation. Measurements of the gas concentration spatial distribution were carried out using a Michelson interferometer. It is shown that adding a light gas to the peripheral channel significantly moves the region of breakdown concentration of injected gas through the central channel away from the nozzle, while maintaining the overall gas flow and background pressure. [ABSTRACT FROM AUTHOR]

Diffusion and seepage collectively govern the mass transfer behavior of gases in the CO2 enhancing coalbed methane recovery (CO2-ECBM) process, significantly influencing both coalbed methane extraction efficiency and CO2 sequestration capacity. Conventional theoretical models typically assume a uniform gas distribution within the coal matrix during injection. However, extensive field studies have revealed inconsistent conclusions. This paper delves into the gas equilibrium time lag property during the CO2-ECBM process, introducing the concept of sub-matrix mass transfer behavior to describe the non-uniform distribution of pressure, and construct the modified binary gas flow control equations and the permeability evolution model that takes this behavior into account. This model is used to investigate how sub-matrix mass transfer influences gas seepage characteristics. Findings show that the equilibrium time lag property intensify with coalbed extension but diminish over time. Despite an increased sub-matrix proportion enhancing CO2 adsorption capacity, the difference fades away due to the decay of the gas equilibrium time lag property. Furthermore, fixed-point monitoring reveals that a higher sub-matrix proportion aggravates permeability evolution, constraining fluid flow capacity. Based on these observations, a hypothesis of multi-level diffusion behavior within the coalbed is proposed, alongside an exploration of optimized CO2 injection strategies, providing new theoretical insights for CO2 sequestration in deep coalbeds. [ABSTRACT FROM AUTHOR]

This study employs computational fluid dynamics (CFD) coupled with the population balance model (PBM) to explore the sensitivity of the drag model for the predictive accuracy of the gas–liquid two-phase flow in continuous casting (CC) mold. Several single bubble drag models have been numerically evaluated for high turbulent intensity and gas flow rate operation parameters. Then, the influence of turbulence effect and bubble swarm mechanisms on bubble dynamic behaviors are investigated. The predicted mean bubble diameter and flow pattern were studied and compared with the experimental data. The results show that all single bubble drag models, except for the Grace model, can predict the bubble size distribution (BSD) well. Meanwhile, all models significantly overestimate the bubble diameter near the nozzle under high gas flow rate conditions. A novel drag correction factor based on local gas holdup and BSD is proposed, which takes into account both the hindrance effect of small bubbles and the accelerating effect of large bubbles. The proposed drag correction factor can accurately predict BSD and flow pattern transition in the CC mold under high gas holdup regions. Compared with the simulation results of the previous single bubble drag model, the mean relative error predicted by the novel drag correction factor is decreased by 69.33%. [ABSTRACT FROM AUTHOR]

The objective of this research is to investigate the influence of a moving shock wave on a dense particle curtain using a coupled supersonic Eulerian–Lagrangian solver. The numerical investigation seeks to gain a deeper understanding of the interactions between particles and gas flow through a four-way coupling approach that incorporates interparticle collisions. Upon interaction, the particle curtain undergoes rapid expansion, generating transmitted and reflected shocks. This work focuses on how different particle arrangements affect the fluid flow dynamics and vice versa. By systematically varying the shock Mach number, we elucidate the effects of these interactions across a range of shock strengths, providing a comprehensive picture of the phenomenon. Our findings reveal the crucial role of particle properties and interparticle forces in shaping the dynamics of shock–granular interactions, paving the way for a deeper understanding of multiphase shock flows in various applications. [ABSTRACT FROM AUTHOR]

This paper presents the results of a study aimed at obtaining new experimental data on the regularities of evaporation of droplets of polyfractional composition in a high-enthalpy gas flow. This study considers the features of heating and subsequent vaporization of water droplets with diameters of 5...100 μm in an air flow with initial temperature up to ∼600 K and velocity up to ∼100 m/s at subcritical Weber numbers. The description of the laboratory setup equipped with laser-shadow means of diagnostics of two-phase flows and the proposed methodology of processing of the registered parameters are presented. On the basis of the conducted experiments, quantitative indicators of the intensity of the process of evaporation of polydisperse water droplets in the air flow are determined. The database of experimental data on the motion and evaporation of water droplets in the air flow, which has been developed according to the available literature sources, has been supplemented with new results, which makes it possible to clarify the corresponding physical and mathematical models. The results obtained can be used in planning and conducting subsequent studies. [ABSTRACT FROM AUTHOR]

In this study, the influence of the discharge orifice shape of swirl liquid jets injected in transverse gas flow was investigated by high-speed photography and shadowgraphy techniques. Three shapes of discharge orifice, including circular, square, and elliptical were tested at different flow conditions. Due to the cross-sectional asymmetry in the ellipse, it is important to place it horizontally or vertically in airflow, and these two states are considered in this study. The main characteristics of liquid jets in transverse air, including trajectory, breakup point, jet width, breakup length, drop size distribution, and Sauter mean diameter, were obtained by image processing. Visualization of flow development revealed that the asymmetry of the swirl hollow cone in the transverse air causes an expanded new structure that cannot be seen in the circular cross section. This structure was called the conical bag and the inflated sheet in elliptical and square cross sections, respectively. The results indicate that the variations of momentum ratio are more effective in the path of non-circular swirl jets. The ellipse in the horizontal direction and square cross section have the breakup point's lowest transverse and longitudinal coordinates, respectively. Theoretical models for predicting swirl liquid jet trajectory and its breakup point were developed and presented. Gamma probability distribution function was fitted on the drop size according to the discrete distribution of the drop size. The results indicated that the distribution of elliptical shapes in the horizontal direction produces the smallest droplets among them while square cross section has a wider distribution. [ABSTRACT FROM AUTHOR]

The presence of natural gas hydrates often coincides with the formation of bubble plumes, serving as evidence for their existence and potential exploitation. Bubble formation boundaries are non-rigid and differ from those formed at rigid boundaries. This study employed an image and acoustic signal synchronization acquisition device in the experimental area to investigate the effects of gas flow rate on the dynamics and acoustics of bubble release from particle layers. The results indicate that as gas flow rate increases, bubble size, production frequency, and particle displacement range increase, while the primary frequency of bubble acoustics decreases. Additionally, the time domain waveform of bubble formation changes from triangular to spindle-shaped; the primary frequency of acoustic signals decreases from 1072 to 625 Hz, with a gradual concentration in distribution. Acoustic frequencies calculated using the Minnaert formula and equivalent diameter are higher than those measured by hydrophones. The initial bubble's acoustic signal intensity and duration are greater than those of subsequent bubbles. This work contributes to the advancement of natural gas hydrate detection techniques and the analysis of their distribution patterns. [ABSTRACT FROM AUTHOR]

Ultrasonic gas flowmeters employ non-intrusive measurement techniques, characterized by rapid responsiveness and exceptional anti-interference capabilities. These attributes not only minimize disruption to the gas during measurement but also facilitate dynamic process control while ensuring robust performance under complex operational conditions. This paper provides an overview of the key components of ultrasonic gas measurement systems, briefly summarizing the fundamental principles of commonly used measurement methods. After focusing on the evolution of transducer structures and materials within ultrasonic probes, it categorizes different types of transducers and outlines the latest designs of excitation circuits in both hardware and software. The review also critically assesses the determination of echo signal reception characteristics and the accuracy and effectiveness of time-of-flight calculations. Based on innovative analyses of the critical nodes within the measurement system's components, a framework system is established for corresponding measurement scenarios. The measurement results show that the repeatability error of the new transducer remains below 0.3%. The optimized signal processing method expands the measurable flow range to 30–1200 m3/h, and the zero drift is reduced to approximately half of the system's original zero drift. This paper aims to provide clear guidance for researchers and professionals in related industries, enabling them to conduct more in-depth studies based on their research interest and enhancing their understanding of ultrasonic measurements. [ABSTRACT FROM AUTHOR]

The main problem considered here is how the obstacle embedded in a gas flow can organize self-protection, by means of surrounding gas, against the gas flow and fluctuations. We show that this is possible in the regime of the nonlinear dynamical screening, which is a result of the nonequilibrium transition that is accompanied by the emergence dense gas phase ahead of the obstacle due to blockade effect in a gas, the emergence of local invariants (invariant behavior of obstacle state that becomes insensitive to the main system parameters), spatial localization of induced gas fluctuations near gas domain wall. As a result, the domain wall in a gas, instead of obstacle, becomes the main scatterer of the flow and protects obstacle state against external driving noise and fluctuations. This can be associated with nonequilibrium protection effect. Considered effects are closely related with skin- and edge-correlation ones inherent to non-Hermitian systems. To demonstrate these phenomena, we resort to the limiting case of the two-component lattice gas in a narrow channel with ring geometry. To describe the nonlinear nonequilibrium steady-state gas structures and long-time gas fluctuations near them, the local equilibrium approach and the mean-field approximation are used. [ABSTRACT FROM AUTHOR]

In the production of castings, intrusive gas pore represents a kind of common defects which can lead to leakage in high gas-tightness requirement castings, such as cylinder blocks and cylinder heads for engines. It occurs due to the intrusion of gases generated during the resin burning of the sand core into castings during the casting process. Therefore, a gas generation and flow constitution model was established, in which the gas generation rate is a function of temperature and time, and the flow of gas is controlled by the gas release, conservation, and Darcy's law. The heat transfer and gas flow during casting process was numerically simulated. The dangerous point of cores is firstly identified by a virtual heat transfer method based on the similarity between heat transfer and gas flow in the sand core. The gas pores in castings are predicted by the gas pressure, the viscosity and state of the melt for these dangerous points. Three distinct sand core structures were designed and used for the production of iron castings, and the simulated gas pore results were validated by the obtained castings. [ABSTRACT FROM AUTHOR]