Gas Flow Behavior Research Articles

(Invited) A Combined Calorimetry and Modeling Approach for Safety Analysis of Large-Size Cells

Safety is a key aspect of battery energy storage systems. Understanding safety aspects of large-size cells is complicated not only by the interplay of multiple physical phenomena but primarily due to limitations in experimental capabilities that can accurately measure all the relevant signals. Due to the limits of battery testing, information such as temperature can be only measured in a practical way. Recognizing this gap, a combined calorimetry and modeling approach is developed for large-size cells to shorten design cycles and reduce cost to optimize batteries with improved safety. Safety of large-size cells is complementarily determined by safety features implemented at multi-levels including material, chemistry, cell and system design. Calorimetry methods have been widely adopted to analyze battery failure mechanisms and hazard under electrical, mechanical and thermal abuse conditions at chemistry and cell levels [1][2]. It prefers sample spatially uniform responses to abuse conditions and is lack of capability to discern orderly sequences to characterize failure evolution within a cell and failure propagation among cells. In this presentation, an integrated multiphysics li-ion battery safety model built on a nonlinear multi-scale multi-domain (MSMD) model framework [3] is introduced. Modularized hierarchical architecture of the MSMD framework allows independent choice of submodels. In the combined approach, the models are adept at utilizing experimental results. calorimetry results serve as guideline to tune the integrated multiphysics model, such as determining physical behaviors being simulated in the submodels and identifying corresponding modeling parameters. Modeling results are then correlated with experimental data to identify potential experimental uncertainties. Safety performance at higher levels can be directly estimated using this model without additional model calibration. The combined approach enables battery safety being addressed efficiently across multiple cells at real-world scenario. It provides insights on functionalities of safety mechanisms and its contribution to overall battery safety. The approach has been applied to study transient gas flow behaviors within an 18650 battery cell subject to internal short circuit and validate safety technical assumptions for the design of a novel packaging architecture for lithium-ion batteries [4]. Moreover, this approach can quantify non-measurable properties and its effects on battery failure severity, such as thermal interfacial properties among large-size cells. Acknowledgement This study was supported by Computer Aided Engineering for Batteries (CAEBAT) project of the Vehicle Technologies Office, Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy. The research was performed using computational resources sponsored by the Department of Energy's Office of Energy Efficiency and Renewable Energy, located at the National Renewable Energy Laboratory. Reference [1] C. Lampe-Onnerud, et al., Safety Studies on Lithium-Ion Batteries by Accelerating Rate Calorimetry, Battery Conference on Applications and Advances, 1999 [2] W. Walker, et al., Statistical characterization of 18650-format lithium-ion cell thermal runaway energy distributions, NASA Aerospace Battery Workshop, Huntsville, Alabama, 2017 [3] G.-H. Kim, K. Smith, K.-J. Lee, S. Santhanagopalan, and A. Pesaran, J. Electrochem. Soc., 58, 8 (2011) [4] Cadenza Innovation, INC (2018). ARPA-E Final Technical Report, Novel low cost and safe Lithium-Ion Electric Vehicle Battery, DE-AR0000392

Continuum Analysis of Rarefaction Effects on a Thermally Induced Gas Flow

A Maxwell gas confined within a micro cavity with nonisothermal walls is investigated in the slip and early transition regimes using the classical and extended continuum theories. The vertical sides of the cavity are kept at the uniform and environmental temperature T0, while the upper and bottom ones are linearly heated in opposite directions from the cold value T0 to the hot one TH. The gas flow is, therefore, induced only by the temperature gradient created along the longitudinal walls. The problem is treated from a macroscopic point of view by solving numerically the so-called regularized 13-moment equations (R13) recently developed as an extension of Grad 13-moment theory to the third order of the Knudsen number powers in the Chapman-Enskog expansion. The gas macroscopic properties obtained by this method are compared with the classical continuum theory results (NSF) using the first and second order of velocity slip and temperature jump boundary conditions. The gas flow behavior is studied as a function of the Knudsen number (Kn), nonlinear effects, for different heating rates T0/TH. The micro cavity aspect ratio effect is also evaluated on the flow fields in this study.

Estimating leaked hydrogen gas flow in confined space through coupling zone model and point source buoyancy plume theory

A semi-analytical model combining zone model and virtual point source buoyancy plume theory is proposed to predict the gas flow and dispersion behaviors of leaked hydrogen in confined space with an opening. The height of interface between the upper and lower layers, outflow velocity and hydrogen molar fraction in outflow at steady stage are quantitively analyzed to study the effects of leakage mass flux and opening geometry. A computational fluid dynamics (CFD) tool, FLACS, is employed to simulate the interested scenarios and validate the reliability of the developed model. The results show that the interface height declines as the leakage mass flux increases, but the outflow velocity and hydrogen molar fraction exhibit inverse tendencies. The interface height is positively proportional to both opening width and height, but the opening height plays a more important role. At steady stage, the simulated interface height fluctuates within 0.1 m uncertainty range, which is identical to the grid size, and it well fits the analytical estimations. The opening width affects the outflow velocity more greatly than that of opening height. The fluctuation of the simulated interface height enhances the inaccuracy of the predicted outflow velocity in the acceptable range. Meanwhile, it is found that with fixed opening geometry the ratio of outflow velocity with higher leakage mass flux to that with lower leakage mass flux remains at 1.28 when the leakage mass flux is doubled. The variations of opening width and height have little and significant effects on outflow hydrogen molar fraction, respectively. Similarly, for given opening geometry the ratio of hydrogen molar fraction with higher leakage mass flux to that with lower leakage mass flux is about 1.58 when the leakage mass flux is doubled.

Numerical investigation of two-phase reactive flow with two moving boundaries in a two-stage combustion system

The quest to achieve higher muzzle velocity is one of the key goals for researchers in the fields of propulsion and ballistic. Based on the conventional chemical propulsion, the two-stage combustion system as a new launch principle can provide higher muzzle velocity without exceeding the maximum pressure in the chamber. In this paper, the modified two-fluid model with two moving boundaries is proposed to simulate the detailed multi-dimensional flow and energy conversion behaviors of the combustion gas and propellant grains in the two-stage chamber. The dynamic self-adapting mesh update method is developed to expand and merge the computational domain for both projectile and piston motions. The application to a standard virtual gun as a standard benchmark for interior ballistic codes is used to validate the accuracy and reliability. The calculation results are in good agreement with those of codes in different countries. After that, a two-stage chamber system is set up based on the standard virtual gun. The numerical results present deep understanding of the two-phase flow behaviors in the two-stage chamber. Then the effects of design parameters on the performances in the additional chamber are numerically investigated. Finally, a suggested scheme of the additional chamber is proposed. The findings of the study put a further prediction tool for the understanding and design of the two-stage combustion system with moving boundaries.

Shale gas transport in wedged nanopores with water films

With the consideration of a mobile high-viscosity water film and a bulk water layer, an analytical model is proposed to predict gas flow behaviors and gas apparent permeability in nanopores. Physical molecular forces are analyzed to determine the properties and formation of the high-viscosity water film and the bulk water layer. Boundary conditions at a solid-liquid interface and a liquid-gas interface are modified to account for water slippage and gas slip. How mobile bulk water molecules influence gas transport capability in pores of different geometry is investigated with different pore sizes and pressure for the whole range of water saturation, which has been validated with experimental data and simulation results. Besides, the effect of a wedged pore structure on multiphase flow behaviors is also investigated to figure out the influences of pore shape.

Numerical investigations on particle separation in dynamic separators

PurposeDynamic separator is an equipment having a rotor and static vanes and is used to separate solids from gas-solids flow based on size. Particle separation in a dynamic separator happens due to complex interchanges between multiple forces exerted in the separation zone. Currently, there is only limited knowledge concerning the working principles of separation. This paper aims to systematically study a dynamic separator using numerical models to get insights into particle separation.Design/methodology/approachThe Lagrangian–Eulerian formulation is used to simulate gas-solid flow. Multiple frames of reference using stage interpolation are used to account for rotation. Periodic symmetry in the equipment is exploited to create a simplified numerical model. The predictions from the numerical model are compared against available experimental data.FindingsThe numerical results indicate that only when particle collision is included, the separation efficiency trend from the experiment is matched by numerical predictions. Further, it is shown that at the same range of rotor speeds where numerical results predict increased separation efficiency, the solid pressure due to particle collision also reaches its maximum value. The gas flow and particle behavior in the separator are explained in detail.Originality/valueThe importance of particle collision in separation is interesting because traditionally, particle separation is assumed to be influenced by three forces, namely, centrifugal force, drag force and gravity. The numerical results, however, point to the contribution by particle collision, in addition to the above three forces.

Dual porosity modelling of the coupled mechanical response of coal to gas flow and adsorption

This paper presents the inclusion of explicit dual poroelastic mechanical behaviour as part of an existing dual porosity numerical model of multiphase, multicomponent chemical-gas transport. The dual poroelastic framework employed considers the pore structure changes occurring as a result of high pressure carbon dioxide injection into coal, particularly the adsorption-induced coal swelling that has been found to limit injectivity in field trials of carbon sequestration in coalbeds around the world. To address this issue, the surface stress of the fluid-solid interface is introduced into the constitutive relation for dual porosity effective stress in order to investigate the coal deformation and porosity changes related to adsorption behaviour. A new porosity model is presented, in which the impacts of gas flow and coal deformation are incorporated, and an interaction coefficient is proposed to explain the effect of fracture-matrix interactions on the porosity evolution. The model is verified and validated in this work against relevant analytical solutions and experimental results, and applied to study the gas flow behaviour and structural changes of coal. The results show that carbon dioxide injection not only causes coal swelling but also has the potential to change the internal pore structure of coal. The variation of fracture porosity is not monotonic as a competing result of effective stress and internal fracture-matrix interactions. However, the matrix porosity is found to increase during carbon dioxide injection, which seems to be a key contributor to the swelling phenomenon.

Analysis of makeup air in a natural smoke vent system in a tall space using numerical simulation and Schlieren technique

Purpose The purpose of this paper is to analyze the phenomenon of makeup effect using numerical simulation and model experiments on seven different natural smoke extraction patterns of tall space. Airflow distribution and heat accumulation phenomenon in different cases are compared. The natural smoke exhaust system for tall spaces has many advantages, including low cost, no power and low maintenance cost. It is more advantageous than the mechanical type of exhaust. However, the internal air distribution is complicated since the large span spatial character. Effective and correct verification method is very important for the analysis of flow fields in tall spaces. Design/methodology/approach This study used fire dynamics simulator (FDS) software to simulate the fire scene. The model experiments are conducted to determine if the numerical simulation results are reasonable. A single-mirror Schlieren system, including an 838 (H) × 736 mm (W) square concave mirror, as well as the focal length of 3,100 mm was adopted to record the dynamic flow of hot gas. Six smokeless candles were burned in a 1/12.5 model in experiments to record the distribution of inflow, accumulation and outflow of airflow in the space. In addition, the thermocouple lines were mounted in the model for temperature measurement. Findings The results of numerical simulation and model experiments have proved that makeup air has a significant effect on the effectiveness of a natural smoke vent system. Larger areas of smoke vents will produce more heat accumulation phenomenon. In this study, the air inlet and vent installed on the same side have a better heat removal effect. Moreover, Schlieren photography technique is proved to be an accurate measurement method to record the dynamic flow of hot air immediately, directly and accurately. The dynamic flow behavior of hot gas in the model has been visualized in this paper. Originality/value At present, there is no examination method other than checking the smoke vent area to validate the effectiveness of a natural smoke vent system in Taiwan, as well as no requirements regarding the makeup inlet. The effect of makeup air in generating the effective push-pull phenomenon of airflow has been analyzed. In addition, the post-combustion hot gas distributions were visualized by using Schlieren photography technology in the model space, compared with the FDS simulation result and thermocouple recorded temperature. A verification method in the model experiments is established to determine if the numerical simulation results are reasonable.

A Numerical Investigation into the Effect of Controllable Parameters on the Natural Gas Storage in a Weak Reservoir-type Aquifer

Natural gas storage process in aquifer, due to fluid flow behavior of gas and water in the porous medium and because of their contact with each other under reservoir conditions, faces several challenges. Therefore, there should be a clear understanding of the injected gas behavior before and after the injection into the reservoir. This research simulates the natural gas storage in aquifer by using Eclipse 300 software. For this purpose, a core sample was considered as the porous medium for gas injection, and a composition of natural gas was injected into the core in different conditions. Moreover, by using Plackett-Burman method, all of the factors affected in this process were screened, and finally four main significant parameters, including the flow rate of injected gas, permeability, pressure, and irreducible water saturation were selected for designing a design of experiments (DOE) plan. Response surface method (RSM) is one of the best methods of experimental design used for optimizing the process and finding the best combination of parameters to have a high stored gas volume and a high recovered gas volume. The simulation includes 28 runs with four considered parameters, and the output is the recovered gas, which in turn is vital for the process accomplishment. Sensitivity analysis and grid independency test were checked. To this end, three grids with different number of cells in x-direction were generated, and by analyzing the results of gas saturation in the porous medium for each model, a grid with 11250 cells (50 elements in x-direction and 15 elements in y- and z-directions) was then chosen as the main grid. Uncertainty analysis and the validation of numerical simulations were carried out, and good agreement was observed between the numerical results and experimental data. In addition, the numerical results showed that the flow rate of the injected gas had a significant impact on the process in comparison with other parameters. Furthermore, increasing permeability and decreasing pressure and irreducible water saturation raise the amount of trapped gas in aquifers. Therefore, for having the maximum stored gas volume and a high recovered gas volume, the best combination of parameters is a high gas injection flow rate (0.9 cc/min), high permeability (1.54 md), a low pressure (2254 psi), and irreducible water saturation. (0.46). Finally, in a natural gas storage operation in an aquifer, both rock properties and operational parameters play important roles, and they should be optimized in order to have the highest amount of stored gas.

Structural and construction design of the system and structures of the supply and distribution of air in the treatment of waste

Introduction. Neutralization methods (including composting) are widely used in the technologies of chemical and biothermal oxidation of organic matter. A promising method of waste management is their biothermal composting using controlled gas flows. The methods of process intensification are described: the introduction of inoculating additives, increasing the homogeneity of the mixture, recycling of composts, natural and forced low-pressure and high-pressure aeration, and several others. One example of the implementation of these technologies is the disposal of oil-contaminated soils. Materials and methods. The description of the implemented complexes of biothermal composting of oil-contaminated soils: functional zoning, design solutions. The main functional zones are shown: input control section, intermediate placement area, continuous forced aeration zone (inoculation), periodic forced aeration zone (stacked cavalier biodegradation), and natural aeration zone without mixing (ripening zone). The main element of the complex is the combined aeration system (forced from blower devices and natural mechanical mixing). The expediency of using high-pressure forced aeration to intensify the composting process is shown. Results. The developed mode of operation of the aeration system of the composted mass is described: the initial process of incomplete oxidation of organic matter in stacks of inoculation with a constant air flow and the final decomposition of organic matter with a periodic air flow. The constructive design of the high-pressure forced aeration system used to intensify the composting process is given. Aerobic biothermal composting is performed in aerated piles, which are formed on sites with a waterproof coating. Aeration, necessary to accelerate the decomposition of organic matter in the composts, is carried out in natural (mixing with a ladle) and artificial (purging) conditions. For purging use a system of perforated pipes and blower station. Describes measures to protect pipelines (ducts) from aggressive environmental exposure and increase their service life, to ensure the efficiency of the aeration system in an emergency. Conclusions. The possibility of practical implementation of gas flow control technology in the design, construction and operation of biothermal treatment of waste is shown. The implementation of the projects described in the article showed the need to create a generalized mathematical model that would describe in general terms the behavior of gas flows in heterophase wastes.

Experimental study of gas flow characteristics in micro-/nano-pores in tight and shale reservoirs using microtubes under high pressure and low pressure gradients

Due to abundant micro-/nanoscale pores and throats, gas flow behavior in tight/shale reservoirs always showed strongly nonlinearity which deviated from the conventional Darcy’s law. As micro-/nanoscale flow experiment was a direct approach to investigate flow characteristic, in this paper, we improved the microscale flow experiment which was widely used in the field of MEMS to adapt for high-pressure conditions. By using microtubes with inner diameter ranging from 0.2 to 5 µm, we investigated the low velocity nonlinear flow characteristic of nitrogen especially under high pressures. In addition, we used experimental results to evaluate the accuracy of three typical flow models which were widely used in gas apparent permeability determination. The results indicated that gas flow behavior in microtube under high outlet pressures was opposite to that under low outlet pressures. When the outlet pressure was low, slippage effect had a great influence on the flow. With the increase in the pressure gradient, the slippage effect became weakened. And the slippage effect would disappear with the increase in the outlet pressure as well as tube inner diameter. The minimum outlet pressure for eliminating the slippage effect of nitrogen for the 0.2 µm tube was 10 MPa which decreased with the tube diameter. However, under high outlet pressures, the flow resistance increased in the region with smaller pressure gradients and varied inversely with the pressure gradient. This phenomenon became more significant with the increase in the outlet pressure and the decrease in the tube inner diameter. From the comparison of 3 typical flow models against our experimental results, we can find different models will match with the data measured under different mean pressures. And the applicability of those models also varied with the tube inner diameter. Thus, it was crucial to select an appropriate model according to different reservoir conditions.

A criterion for evaluating the effect of shale-matrix dual-continuum flow on gas production

Because of the large range of pore size distribution and the chemical/mineralogical heterogeneity within shale matrix, gas flow in it may exhibit dual-continuum flow behavior even though rock matrix is not fractured. The relative importance of dual-continuum flow has considerable implications to the shale reservoir characterization and gas production. A matrix-dominant gas flow model is developed to evaluate the impacts of dual-continuum gas flow on gas production. The simulation results reveal three regimes with regard to the relative importance of the dual-continuum flow. When the mass transfer coefficient between the mobile and immobile continua is relatively high, the dual-continuum behavior becomes insignificant within the context of production rate prediction. When the mass transfer coefficient is very small, the dual continuum gas flow behavior also becomes insignificant because gas flow between the two continua is essentially negligible. Thus, the dual-continuum gas flow behavior becomes important to the long-term gas production rate only for the intermediate range of mass transfer coefficient that is shown to depend on porosity and gas adsorption properties. Based on the physical reasoning and numerical simulation results, we propose a criterion to determine the relative importance of the dual-continuum gas flow. The criterion is expressed with a dimensionless parameter that combines several parameters including the mass transfer coefficient, gas viscosity and densities and matrix porosity. The numerical simulation results show that when the dimensionless parameter is less than a critical value, the dual-continuum gas flow becomes important under a variety of different conditions.

The influence of CO2 saturation time on the coal gas flow: Fractured bituminous coal

The permeability reduction due to the coal matrix swelling induced by the adsorption of CO2 is the major concern during enhanced coalbed methane recovery (ECBM) as well as CO2 sequestration in coal reservoir. Many problems arise in the context of this process regarding the coal permeability variations, and very few studies have been made with consideration of long-term CO2 saturations on gas flow behaviour alterations. The main objective of this study is therefore to examine the influence of both subcritical and supercritical CO2 flooding durations on N2 and CO2 permeability variation of naturally fractured low volatile bituminous coal under various tri-axial conditions. Five CO2 flooding durations, up to 65 h, both subcritical (6 MPa) and supercritical (14, 20 MPa), were introduced to the sample under three confinements, respectively. Results show that for 11 MPa and 17 MPa confining environment, most permeability reduction occurs during the first CO2 flooding process, and supercritical CO2 flooding causes significant higher N2 permeability reduction (from 14.38% to 50.18%) than subcritical CO2 (from 4.11% to 11.25%). The permeability reduction rate decreases with time but this reduction continues even after a total of 153 h flooding. Longer permeability reduction process is observed upon supercritical CO2 adsorption due to the much higher viscosity of supercritical CO2. Under deep underground condition (>1 km), CO2 exhibits a N2-like flow behaviour because of the dominant poroelastic effect. The influence of CO2 flooding on permeability alterations has been significantly compromised with much smaller permeability reduction after 20 MPa CO2 flooding compared with 14 MPa CO2 flooding (7.33% and 38.75% for 7 MPa CO2 injection pressure, respectively), along with no apparent permeability reduction for the further CO2 flooding scenarios.

Permeability Characteristics of Broken Coal and Rock Under Cyclic Loading and Unloading

During longwall mining, the permeability evaluation in a caving zone is one of the most challenging risks for mine operators because it controls the behavior of gas flow and it significantly influences gob gas extraction and spontaneous combustion. Based on the stress environment of repeated mining in the Huainan coal mine, this study discusses the results of a laboratory experiment on broken coal and rock in a caving zone of a gob. The stress–permeability relationship of broken coal, rock, and combination of coal and rock samples with various particle sizes under cyclic loading and unloading was experimentally studied. The laboratory test results imply that permeability stress sensitivity and permeability loss of the first loading and unloading were significantly greater than the succeeding cyclic loading and unloading. Re-crushing and re-arrangement were the main two factors that lead to a drastic drop in caving zone porosity causing permeability reduction in the first loading and unloading process. The initial permeability and initial pore compressibility increased logarithmically when particle size increased, while the changing rate of pore compressibility decreased exponentially. The stress sensitivity of the broken coal samples’ permeability increased when particle size increased. Based on the laboratory experiments, the stress–permeability fitting model considering particle size of broken coal and rock in a caving zone during repeated mining was proposed in this study.

Probabilistic CFD computations of gas turbine vane under uncertain operational conditions

The stochastic computations of a NASA gas turbine vane are conducted to investigate the effects of the operational uncertainties on the flow and heat transfer characteristics of the NASA C3X blade. The blade contains ten internal cooling channels to remove heat load. In order to minimize the analysis error the full conjugate heat transfer methodology has been employed to simulate the behavior of external hot gas flows, internal cooling air passages and the solid blade simultaneously. The v2-f turbulence model is used and it is shown the predicted results are in acceptable agreement with the available experimental data. Total pressure, total temperature, turbulence intensity, turbulent length-scale of the inlet and the outlet static pressure are assumed to be stochastic with Beta probability distribution functions. The effects of these uncertainties on flow and thermal fields as well as the blade temperature distribution are studied. The polynomial chaos method with polynomials order p=3 is used to quantify the effects of operational uncertainties. The non-deterministic CFD results are found to be in close agreement with the experimental data. Uncertainties specially in inlet total temperature and turbulent length-scale play key roles on the hydrodynamic and thermal fields around the airfoil also the turbine vane temperature distribution.

Transient model analysis of gas flow behavior for a multi-fractured horizontal well incorporating stress-sensitive permeability

The assumption of constant reservoir permeability is not strictly applicable to reservoirs where rock properties undergo changes, such as stress-sensitive porous media. Most researches on the permeability stress sensitivity mainly concentrated on experimental approach, physical modeling or pressure transient analysis, whereas rate transient analysis does not attract much attention. Based on source/sink function method, this paper develops a seepage model of multi-fractured horizontal well incorporating stress-sensitive permeability. The model is semi-analytically solved by fracture discretization, Pedrosa’s transformation, perturbation theory, and integration transformation method. Not only pressure transient analysis, but also rate transient analysis is separately performed with relevant parameters. The model presented here can provide some insights into well dynamic forecasting during exploiting such reservoirs, and contribute to establish the theoretical basic for transient analysis efficiently.

Investigation on choking behavior of gas flow in microducts

In continuum regime, the large surface-to-volume ratio in microscale flow indicates stronger influence of boundary layer on internal flow, which is confirmed by the present study through quantitatively analyzing the in-duct choking and profile of boundary layer in a series of straight rectangular microducts with convergent entrances. The exit height and width of the microducts are 500 µm and 2500 µm. The number density distribution along the duct centerline is measured using a laser-induced fluorescence technique in underexpanded conditions for Reynolds numbers ranging from 745 to 6710. The experimental results show that an unexpected drop in number density emerges upstream of the duct exits. By numerically solving the 3-D Navier–Stokes equations, the computational results reveal that the build-up of boundary layer forms a virtual throat upstream of the duct exit, thus turns the straight duct into a convergent–divergent micronozzle. The location of Mach-number unity (choking) and the boundary-layer thickness are found affected by both duct configuration and Reynolds number at choking. In addition, location of the farthest in-duct choking from duct exit is found corresponding to a certain range of transition from laminar to turbulent at Re ∼ 2000. The 1-D analysis confirms that the in-duct choking phenomenon is related to the boundary-layer blockage rather than friction. The results of the present survey indicate the significance of reckoning boundary-layer blockage in micronozzle or microduct design.

Simulated pulsed flow of gas and particles in a horizontal oppose-pulsed gas jets of bubbling fluidized bed

Flow behavior of gas and particles with a horizontal oppose-pulsed gas jets are simulated by means of a three dimensional Computational Fluid Dynamics (CFD) model with the kinetic theory of granular flow in a gas-particles bubbling fluidized bed. The effects of amplitudes and frequencies on the hydrodynamics of gas and particles are analyzed. The simulation results are presented in terms of phase velocity vector plot, volume fraction of phases, granular temperature, power spectrum and Reynolds stresses in the bed. Results show that the impingement caused by the oppose-pulsed gas jets oscillates with the variation of pulsed gas velocity. The impingement zone with the high solid volume fraction reciprocates from the left side to the right side through the bed center with the variation of pulsed jet gas velocities. The lateral velocity and gas turbulent kinetic energy, granular temperature and Reynolds stresses of gas and particles are larger near the pulsed gas jets than that at the center of the bed. The large dispersion coefficients of particles using the horizontal oppose-pulsed gas jets enhance the mixing of particles in gas-solid fluidized bed.

Evaluation and improvement of particle collection efficiency and pressure drop of cyclones by redistribution of dustbins

The pressure drop and particle collection efficiency are important parameters for cyclone performance. Reynolds stress model (RSM) and discrete phase model (DPM) are used to simulate the gas flow and particle migration behaviors in several cyclone separators. The simulation is validated by comparing simulation results of velocity profile and particle collection efficiency with experimental data. Two cyclones with multi-dustbins distributed at the sidewalls and bottom walls are proposed. Simulation results demonstrate that the distribution of multi-dustbins has a significant effect on the cyclone performance. Obvious particle collection efficiency improvement for fine particles and smaller pressure drop than the standard cyclone are obtained.

A novel approach for solving nonlinear flow equations: The next step towards an accurate assessment of shale gas resources

As ultra-tight porous media that include organic contents, shale gas resources are technically known as complex systems having various mechanisms that impact storage and flow. The slippage, Knudsen diffusion, the process of desorption, an adsorbed layer that affects apparent permeability, and solute gas in kerogen are recognized to be the most important ones. However, simultaneous effects of multi-mechanism flow and storage, and influences of scattered organic contents on shale gas flow behaviour are not well-understood yet.According to the mass conservation law, a basic mathematical model has been developed to investigate, step-by-step, the effects of different changes that are introduced, and examine whether patterns of how kerogen is distributed affect the production plateaus. The discretization of the second-order nonlinear Partial Differential Equation (PDE) that is evolved results in a certain number of nonlinear simultaneous algebraic equations, which are conventionally solved with the application of Newton’s method. To overcome the inherent difficulties of the initial guess, the derivations, and the inversion of the Jacobian matrix, a new application of Particle Swarm Optimization (PSO) as a nonlinear solver was applied to extract the anticipated pressure profile for each step in time outside the bounds of the reference equations.The results show that not only can the PSO effectively meet the required criteria, but also it performed faster than conventional techniques, especially in cases with a larger number of grids that encompass more phenomena. It was further revealed that the insertion of a multi-mechanism apparent permeability model in which the pore radius is also a pressure-dependent parameter causes the lower rate of production. A higher level of production has been recorded after including storage terms of adsorption and solute gas in kerogens. Although different patterns of kerogen distribution have finally overlapped, the different taken trend of each production profile underlines the impact of kerogen distribution as an important parameter within the procedure of history matching.