Identifying the enhancement mechanism of Al/MoO_(3) reactive multilayered films on the ignition ability of semiconductor bridge using a one-dimensional gas-solid two-phase flow model

Energetic Semiconductor bridge(ESCB)based on reactive multilayered films(RMFs)has a promising application in the miniature and intelligence of initiator and pyrotechnics device.Understanding the ignition enhancement mechanism of RMFs on semiconductor bridge(SCB)during the ignition process is crucial for the engineering and practical application of advanced initiator and pyrotechnics devices.In this study,a one-dimensional(1D)gas-solid two-phase flow ignition model was established to study the ignition process of ESCB to charge particles based on the reactivity of Al/MoO_(3) RMFs.In order to fully consider the coupled exothermic between the RMFs and the SCB plasma during the ignition process,the heat release of chemical reaction in RMFs was used as an internal heat source in this model.It is found that the exothermal reaction in RMFs improved the ignition performance of SCB.In the process of plasma rapid condensation with heat release,the product of RMFs enhanced the heat transfer process between the gas phase and the solid charge particle,which accelerated the expansion of hot plasma,and heated the solid charge particle as well as gas phase region with low temperature.In addition,it made up for pressure loss in the gas phase.During the plasma dissipation process,the exothermal chemical reaction in RMFs acted as the main heating source to heat the charge particle,making the surface temperature of the charge particle,gas pressure,and gas temperature rise continuously.This result may yield significant advantages in providing a universal ignition model for miniaturized ignition devices.

A transient production prediction method for tight condensate gas wells with multiphase flow

Considering the phase behaviors in condensate gas reservoirs and the oil-gas two-phase linear flow and boundary-dominated flow in the reservoir,a method for predicting the relationship between oil saturation and pressure in the full-path of tight condensate gas well is proposed,and a model for predicting the transient production from tight condensate gas wells with multiphase flow is established.The research indicates that the relationship curve between condensate oil saturation and pressure is crucial for calculating the pseudo-pressure.In the early stage of production or in areas far from the wellbore with high reservoir pressure,the condensate oil saturation can be calculated using early-stage production dynamic data through material balance models.In the late stage of production or in areas close to the wellbore with low reservoir pressure,the condensate oil saturation can be calculated using the data of constant composition expansion test.In the middle stages of production or when reservoir pressure is at an intermediate level,the data obtained from the previous two stages can be interpolated to form a complete full-path relationship curve between oil saturation and pressure.Through simulation and field application,the new method is verified to be reliable and practical.It can be applied for prediction of middle-stage and late-stage production of tight condensate gas wells and assessment of single-well recoverable reserves.

Simulation of gas-solid flow characteristics of the circulating fluidized bed boiler under pure-oxygen combustion conditions

Under the pressure of carbon neutrality,many carbon capture,utilization and storage technologies have witnessed rapid development in the recent years,including oxy-fuel combustion(OFC)technology.However,the conventional OFC technology usually depends on the flue gas recirculation system,which faces significant investment,high energy consumption,and potential low-temperature corrosion problem.Considering these deficiencies,the direct utilization of pure oxygen to achieve particle fluidization and fuel combustion may reduce the overall energy consumption and CO_(2)-capture costs.In this paper,the fundamental structure of a self-designed 130 t·h^(-1) pure-oxygen combustion circulating fluidized bed(CFB)boiler was provided,and the computational particle fluid dynamics method was used to analyze the gas-solid flow characteristics of this new-concept boiler under different working conditions.The results indicate that through the careful selection of design or operational parameters,such as average bed-material size and fluidization velocity,the pure-oxygen combustion CFB system can maintain the ideal fluidization state,namely significant internal and external particle circulation.Besides,the contraction section of the boiler leads to the particle backflow in the lower furnace,resulting in the particle suspension concentration near the wall region being higher than that in the center region.Conversely,the upper furnace still retains the classic core-annulus flow structure.In addition to increasing solid circulation rate by reducing the average bed-material size,altering primary gas ratio and bed inventory can also exert varying degrees of influence on the gas-solid flow characteristics of the pure-oxygen combustion CFB boiler.

Phase-Based Optical Flow Method with Optimized Parameter Settings for Enhancing Displacement Measurement Adaptability

To enhance the applicability and measurement accuracy of phase-based optical flow method using complex steerable pyramids in structural displacement measurement engineering applications, an improved method of optimizing parameter settings is proposed. The optimized parameters include the best measurement points of the Region of Interest (ROI) and the levels of pyramid filters. Additionally, to address the issue of updating reference frames in practical applications due to the difficulty in estimating the maximum effective measurement value, a mechanism for dynamically updating reference frames is introduced. Experimental results demonstrate that compared to representative image gradient-based displacement measurement methods, the proposed method exhibits higher measurement accuracy in engineering applications. This provides reliable data support for structural damage identification research based on vibration signals and is expected to broaden the engineering application prospects for structural health monitoring.

Numerical Simulation on Gas-Solid Two-Phase Turbulent Flow in FCC Riser Reactors(Ⅰ) Turbulent Gas-Solid Flow-Reaction Model

Gas-solid two-phase turbulent flows,mass transfer,heat transfer and catalytic cracking reactions areknown to exert interrelated influences in commercial fluid catalytic cracking(FCC)riser reactors.In the presentpaper,a three-dimensional turbulent gas-solid two-phase flow-reaction model for FCC riser reactors was devel-oped.The model took into account the gas-solid two-phase turbulent flows,inter-phase heat transfer,masstransfer,catalytic cracking reactions and their interrelated influence.The k-V-k_P two-phase turbulence modelwas employed and modified for the two-phase turbulent flow patterns with relatively high particle concentration.Boundary conditions for the flow-reaction model were given.Related numerical algorithm was formed and a nu-merical code was drawn up.Numerical modeling for commercial FCC riser reactors could be carried out with thepresented model.

Experimental investigation of erosion rate for gas-solid two-phase flow in 304 stainless/L245 carbon steel

Erosion is one of the most concerning issues in pipeline flow assurance for the Oil&Gas pipeline industries,which can easily lead to wall thinning,perforation leakage,and other crucial safety risks to the steady operation of pipelines.In this research,a novel experimental device is designed to investigate the erosion characteristics of 304 stainless and L245 carbon steel in the gas-solid two-phase flow.Regarding the impacts on erosion rate,the typical factors such as gas velocity,impact angle,erosion time,particle material and target material are individually observed and comprehensive analyzed with the assistance of apparent morphology characterized via Scanning Electron Microscope.Experimental results show that the severest erosion occurs when the angle reaches approximate 30°whether eroded by type I or type II particles,which is observed in both two types of steel.Concretely,304 stainless steel and L245 carbon steel appear to be cut at low angles,and impacted at high angles to form erosion pits.In the steady operational state,the erosion rate is insensitive to the short erosion time and free from the influences caused by the“erosion latent period”.Based on the comparison between experimental data and numerical results generated by existing erosion models,a modified model with low tolerance(<3%),high feasibility and strong consistency is proposed to make an accurate prediction of the erosion in terms of two types of steel under various industrial conditions.

Flow Characteristics Analysis of TC18 Titanium Alloy during Hot Deformation Based on Phase Transformation

An accurate flow stress model was established by considering the parameters of strain rate,strain and temperature as well asβ→a+βphase transformation in order to develop the plastic forming theory of TC18 titanium alloy.Firstly,the phase transition kinetics of TC18 titanium alloy during isothermal and continuous cooling at 1073 and 1273 K was studied by thermodynamic calculation,meanwhile,the relationship of volume fraction of phase transition with temperature and time was obtained.Constitutive models were calculated by investigating flow behaviors under hot compression tests with the strain rates of 0.001-1s^(-1) and temperatures of 973-1223 K in the singleβand a+βregions in TC18 titanium alloy,respectively.By combining the phase transformation dynamic kinetics with constitutive models,an accurate flow stress model was established,providing theoretical basis and data support for the hot forging of TC18 titanium alloy.

Experimental Investigation of Regular or Wavy Two-Phase Flow in a Manifold

An experimental study was conducted to investigate the properties of stratified regular or wavy two-phase flow in two parallel separators located after a manifold.A total of 103 experiments with various gas and liquid velocity combinations in three inlet pipes were conducted,including 77 groups of outlet pipe resistance symmetry and 26 groups of outlet pipe resistance asymmetry trials.The experimental results have revealed that when the gas-liquid flow rate is low,the degree of uneven splitting is high,and“extreme”conditions are attained.When the superficial gas velocity is greater than that established in the extreme case,the direction of the liquid-phase displacement is reversed,while that of the gas remains unchanged.Thus,the degree of gas phase bias tends to be mitigated with an increase in the gas velocity,while the uneven splitting degree of liquid approaches 10%.Finally,varying the gas-phase outlet pipe resistance is shown to effectively change the gas-liquid two-phase flow distribution.

Numerical simulation of the gas-solid two-phase flow inside the multi-channel nozzle for the surface nanocrystallization induced by the ultrasonic particulate peening

Using a gas-solid two-phase model(a discrete phase model),the authors investigated the flow field inside the multi-channel nozzle for surface nanocrystallization(SNC)induced by the ultrasonic particulate peening(USPP).By computation,the velocity fields of both the gas and the solid phases were simulated and the track of the solid phase was analyzed in detail.It can be found that the velocities of the two phases are able to reach an ultrasonic level;meanwhile,the dispersion width of the solid phase at the nozzle exit is less than that of the gas phase.When particle diameters are less than 5 μm,there is a decreasing trend in the dispersion width of the solid phase with an increase in particle diameters.The trend becomes stable as the particle diameters are greater than 5 μm;in the meantime,the distribution of solid particles is near the axis of the jet flow.The optimal standoff distance between the nozzle and the substrate in the process of USPP is about 120 mm.Simulation results can help improve the design of mass-production-oriented multi-channel nozzles for SNC induced by USPP.

One‑Step Gas-Solid‑Phase Diffusion‑Induced Elemental Reaction for Bandgap‑Tunable Cu_(a)Agm_(1)Bim_(2)I_(n)/CuI Thin Film Solar Cells

Lead-free inorganic copper-silver-bismuth-halide materials have attracted more and more attention due to their environmental friendliness,high element abundance,and low cost.Here,we developed a strategy of one-step gas-solid-phase diffusioninduced reaction to fabricate a series of bandgap-tunable Cu_(a)Agm_(1)Bim_(2)I_(n)/CuI bilayer films due to the atomic diffusion effect for the first time.By designing and regulating the sputtered Cu/Ag/Bi metal film thickness,the bandgap of Cu_(a)Agm_(1)Bim_(2)I_(n)/CuI could be reduced from 2.06 to 1.78 eV.Solar cells with the structure of FTO/TiO_(2)/Cu_(a)Agm_(1)Bim_(2)I_(n)/CuI/carbon were constructed,yielding a champion power conversion efficiency of 2.76%,which is the highest reported for this class of materials owing to the bandgap reduction and the peculiar bilayer structure.The current work provides a practical path for developing the next generation of efficient,stable,and environmentally friendly photovoltaic materials.

Numerical Simulation of Gas-Solid Two-Phase Flow in Reverse Blowing Pickup Mouth

Pickup mouth is a key component for the service performance of a street sweeper. Computational fluid dynamics( CFD) technology,as an analysis tool in fluid flow simulation,is employed in this work because it can greatly shorten the design period. To obtain higher simulation accuracy,the gas-solid coupling inside the process cannot be neglected during numerical simulation.Our optimization procedure considers the influence of structure and operational parameters. It is recommended that the outlet diameter is less than 0. 42 of the width and the outlet inclination angle is 110°for structure parameters. The dust collection efficiency is improved when the reverse flow rate is 70% of the total volume,the sweepertraveling speed is 10 km / h,and the pressure drop is 2 400 Pa.Simulation results exhibit well consistency with the physical experimental results.

Numerical Simulation of the Gas-solid Two-phase Flows in a Precalciner

The gas-solid two-phase flous of the precalciner were simulated by different multiphase models,such as mixture model,the Enderium model,including mixture and dispersed,and discrete phase model（DPM）,The results of the different multiphase models were analyzed and compared.showing the rationality of the diffusion and mixture of the cenment raic meals and coal poroder some extent Moreover,the results also shose the rationality of the given inlets parameters of actual process of the precalciner.

Thermophoresis effects on gas-particle phases flow behaviors in entrained flow coal gasifier using Eulerian model

A numerical model based on the Eulerian–Eulerian two-fluid approach is used to simulate the gasification of coal char inside an entrained flow gasifier. In this model, effects of thermophoresis of coal char particles are thoroughly investigated. The thermophoresis is due to the gas temperature gradient caused by absorpted heat of coal char gasification. This work, firstly, calculates the gas temperature gradient and thermophoretic force at1100 °C,1200 °C,1300 °C and 1400 °C wall temperatures. Then, the changes of particle volume fraction and velocity in the gasifier are studied in the simulation with thermophoresis or not. The results indicate that considering the particle thermophoresis has some effects on the calculation of particle volume fraction in the gasifier, especially at wall temperature of 1400 °C, and the maximum particle volume fraction variance ratio reaches up to 1.38% on wall surface of the gasifier. These effects are mainly caused by large gas temperature gradient along the radial direction of the gasifier. For the particle velocity, the changes are small but can be observable along radial direction of the gasifier, which has good agreement with the distributions of radial gas temperature gradient and thermophoretic force. These changes above may have certain effects on gasification reaction rates in this Eulerian model. So the change of gasification reaction rates in the simulation with thermophoresis or not is studied finally.

Heat Transfer Method for Solid Flow Rate Measurement in Gas-Solid Two Phase Flow

ＨｅａｔＴｒａｎｓｆｅｒＭｅｔｈｏｄｆｏｒＳｏｌｉｄＦｌｏｗＲａｔｅＭｅａｓｕｒｅｍｅｎｔｉｎＧａｓＳｏｌｉｄＴｗｏＰｈａｓｅＦｌｏｗＹｕａｎＺｈｕｌｉｎ（袁竹林）ＬｕＺｕｏｊｉ（卢作基）（ＴｈｅｒｍｏｅｎｅｒｇｙＥｎｇｉｎｅｅｒｉｎｇＲｅｓｅａｒ...

Computational fluid dynamics simulation of gas-liquid two phases flow in 320 m^3 air-blowing mechanical flotation cell using different turbulence models

According to the recently developed single-trough floating machine with the world's largest volume(inflatable mechanical agitation flotation machine with volume of 320 m3) in China, the gas-fluid two-phase flow in flotation cell was simulated using computational fluid dynamics method. It is shown that hexahedral mesh scheme is more suitable for the complex structure of the flotation cell than tetrahedral mesh scheme, and a mesh quality ranging from 0.7 to 1.0 is obtained. Comparative studies of the standard k-ε, k-ω and realizable k-ε turbulence models were carried out. It is indicated that the standard k-ε turbulence model could give a result relatively close to the practice and the liquid phase flow field is well characterized. In addition, two obvious recirculation zones are formed in the mixing zones, and the pressure on the rotor and stator is well characterized. Furthermore, the simulation results using improved standard k-ε turbulence model show that surface tension coefficient of 0.072, drag model of Grace and coefficient of 4, and lift coefficient of 0.001 can be achieved. The research results suggest that gas-fluid two-phase flow in large flotation cell can be well simulated using computational fluid dynamics method.

Effect of droplet characteristics on liquid-phase distribution in spray zone of internal mixing air-mist nozzle

In continuous casting production,droplet characteristics are important parameters for evaluating the nozzle atomization quality,and have a significant impact on the secondary cooling effect and the slab quality.In order to study the behavior of atomized droplets after reaching the slab surface and to optimize the spray cooling effect,the influence of droplet diameter and droplet velocity on the migration behavior of droplets in the secondary cooling zone was analyzed by FLUENT software.Results show that the droplets in the spray zone and on the slab surface are mainly concentrated in the center,thus,the liquid volume fraction in the center is higher than that of either side.As the droplet diameter increases,the region of high liquid volume fraction on the slab surface becomes wider,and the liquid phase distribution in the slab width direction becomes uneven.Although increasing the droplet velocity at the nozzle exit has little effect on droplet diffusion in the spray zone,the distribution becomes more uneven due to more liquid reaches the slab surface per unit time.A prediction formula of the maximum water flow rate on the slab surface for specific droplet characteristics was proposed based on dimensionless analysis and validated by simulated data.A nozzle spacing of 210 mm was recommended under the working conditions in this study,which ensures effective coverage of the spray water over the slab surface and enhances the distribution uniformity of water flow rate in the transverse direction.

Discrete Group Gas-Solid Two-Phase Flow Model and Its Simulation in the Large Caliber High Speed Davis Gun

Aiming at the characteristics of the long tubular powder,a one-dimensional discrete group gas-solid two-phase flow model was established for the large caliber high speed Davis gun with a tubular modular charge.In this model,the tubular modules were described by the Lagrangian system without being assumed as pseudofluid,whereas the gas field is described by Eulerian system.The new model was used to simulate a 480 mm Davis gun.The simulation results were compared with test results,and the model was verified to be feasibility.This study provides a new method to research the interior ballistic performance of Davis guns.

PREDICTIONS OF 3-D STRONGLY SWIRLING GAS-SOLID TWO-PHASE FLOW WITH GAS COMBUSTION

ＰＲＥＤＩＣＴＩＯＮＳＯＦ３┐ＤＳＴＲＯＮＧＬＹＳＷＩＲＬＩＮＧＧＡＳ┐ＳＯＬＩＤＴＷＯ┐ＰＨＡＳＥＦＬＯＷＷＩＴＨＧＡＳＣＯＭＢＵＳＴＩＯＮＷａｎｇＺｈｅｎｙｕ（王振宇）（ＳｈａｎｇｈａｉＷｕｊｉｎｇＴｈｅｒｍａｌＰｏｗｅｒＰｌａｎｔ）ＨｕａｎＢｏ...

Annular multiphase flow behavior during deep water drilling and the effect of hydrate phase transition

It is very important to understand the annular multiphase flow behavior and the effect of hydrate phase transition during deep water drilling. The basic hydrodynamic models, including mass, momentum, and energy conservation equations, were established for annular flow with gas hydrate phase transition during gas kick. The behavior of annular multiphase flow with hydrate phase transition was investigated by analyzing the hydrate-forming region, the gas fraction in the fluid flowing in the annulus, pit gain, bottom hole pressure, and shut-in casing pressure. The simulation shows that it is possible to move the hydrate-forming region away from sea floor by increasing the circulation rate. The decrease in gas volume fraction in the annulus due to hydrate formation reduces pit gain, which can delay the detection of well kick and increase the risk of hydrate plugging in lines. Caution is needed when a well is monitored for gas kick at a relatively low gas production rate, because the possibility of hydrate presence is much greater than that at a relatively high production rate. The shut-in casing pressure cannot reflect the gas kick due to hydrate formation, which increases with time.