Reactive Flow Research Articles

Experimental and numerical investigation on the pyrolysis of oil shale particles in a bubbling fluidized bed

The efficient utilization of oil shale resource is beneficial to environment and the resource diversity. In this work, a bubbling fluidized bed (BFB) reactor was first used to pyrolyze Huadian oil shale experimentally, mainly focusing on the influence of fluidization flow rates. The yield of shale oil, char and non-condensable gas varies little at different fluidization flow rates, but the components in shale oil are different due to the secondary cracking, such as the fractions and species of aliphatic hydrocarbons, aromatic hydrocarbons and non-hydrocarbons. Then, the dense discrete phase model (DDPM) was used to track the trajectories of oil shale particles with different diameters in a bubbling fluidized bed. Population balance model (PBM) coupled Eulerian model was used to well describe the bubbling status of bed materials to characterize the hydrodynamic behaviors. Furthermore, a segmented kinetic model was compiled by UDF module to illuminate the pyrolysis of oil shale particles. The multi-phase reactive flow modeling clearly indicated the distribution of oil shale particles and gaseous products in BFB reactor, as well as pyrolysis time and the secondary cracking at different fluidization flow rates. In summary, this work provides a reference basis for complete pyrolysis of oil shale particles in a bubbling fluidized bed and generating shale oil with high yield and good quality.

Numerical analysis of biomass gasification in a fluidized bed reactor using a computational fluid dynamics model integrated with reduced-order reaction kinetics

The use of detailed reaction kinetics in a computational fluid dynamics (CFD) model for simulating the complex reactive gas-solid flow during fluidized bed gasification of biomass (FBGB) is extremely intensive in computations. A reduced-order reaction kinetics model was thus developed and validated that can be integrated with a CFD model to improve the prediction of the formation of tar and syngas components during FBGB at various sizes and chemical compositions of biomass particles. The simulations by the integrated CFD model and reduced-order kinetics showed that pyrolytic products were released from biomass at various temperatures and rates, which created large variations in the concentrations of tar compounds and syngas, and the oxygen to fuel ratio in the bed. The CFD simulations showed that H2 and CO were generated in both heterogeneous phase of the expanded bed and homogenous gas phase in the freeboard region while large portions of CO2 and CH4 were generated in the gas phase near to the top freeboard. Optimization of syngas residence time at a specific gasification temperature can thus reduce the formation of tar, CO2 and CH4.

Characterization of cosputtered (TiZrHfY)Nx films

Medium-entropy TiZrHfY alloy films and corresponding nitride (TiZrHfY)Nx films were fabricated through cosputtering. The Ti0.24Zr0.23Hf0.27Y0.26 film had the form of a hexagonal close-packed (HCP) solid solution with a mixing enthalpy of 9.09 kJ/mol, mixing entropy of 11.50 J/mol·K (1.38 R), atomic size difference of 7.72 %, and valence electron concentration of 3.73. Moreover, this film had a hardness of 6.0 GPa and an elastic modulus of 106 GPa. (TiZrHfY)Nx films with various stoichiometric ratios (x) were fabricated by adjusting the reactive gas flow ratio fN2 [N2/(N2 + Ar)] in the range 0.1–0.7. Adding N to the TiZrHfY matrix resulted in a change of phase from an HCP structure to a face-centered cubic phase. The (Ti0.23Zr0.18Hf0.24Y0.35)N0.71 film (with fN2 = 0.2) exhibited the most favorable mechanical properties, having a hardness of 19.1 GPa and an elastic modulus of 244 GPa. Moreover, the film had the highest critical loads (LC3 = 46.6 N) among the films analyzed in the scratch test. The anticorrosive properties of the TiZrHfY and (TiZrHfY)Nx films were evaluated using potentiodynamic polarization curves, obtained in 3.5 wt% NaCl aqueous solution. High polarization resistance of 1.1 × 106 Ω·cm2 was obtained for the (Ti0.23Zr0.18Hf0.24Y0.35)N0.71 film, which was 145 times higher than that of the bare SUS420 substrate. The (Ti0.23Zr0.18Hf0.24Y0.35)N0.71 film had the most favorable mechanical and anticorrosive properties of the surveyed (TiZrHfY)Nx films.

Plasma emission spectroscopy and optical properties of reactive-sputtered silicon oxynitride films

Silicon oxynitride (SiO x N y ) thin films were synthesized via reactive direct current magnetron sputtering under different reactive gas mass flow ratios (O2:N2) and discharge powers. The process was monitored by optical emission spectroscopy (OES), while spectroscopic ellipsometry was used to characterize the optical properties of the thin films and deposition rates. In this work, the plasma generated under different deposition parameters is analyzed by monitoring the emission lines of different species (Si I, Ar I, O2, and N2) and these results are then correlated with the corresponding target poisoning process and the optical properties of the grown thin films. According to the spectral analysis, the emission lines proved to be sensitive to the synthesis process as it was possible to differentiate deposition variations when other parameters remained unchanged. Furthermore, similar plasma conditions determined via the emission of different species were found to produce consistent thin film optical properties and vice versa. OES showed to be an effective method of monitoring and controlling the deposition of SiO x N y thin films with specific compositions.

AC Networks With Microgrids: Passivity-Based Controllers in Single Phase Electric Network

—This paper is an investigation of the possible integration of distributed energy resources (DERs) in single-phase alternating current networks, using voltage-controlled converters, based on passivity-based control theory. In closed-loop operation, Hamiltonian representations facilitate the development of passive controllers that guarantee stability. The trajectory tracking problem can be solved as a regulation problem by transforming the non-autonomous dynamical model into an incremental model. In this work, the primary contribution is the ability to control active and reactive power flows between DERs and the grid according to the availability of primary energy resources and converter capacity. Simulated results indicate that all passive controllers achieve the control objective, maintaining asymptotic stability and achieving the same dynamic performance as integral proportional controllers. SimPowerSystems library is used to develop all simulations under the MATLAB/Simulink environment. The paper presents a novel approach to integrating distributed energy resources into single-phase alternating current networks, utilizing voltage-controlled converters and leveraging passivity-based control theory.

Analysis of chemical reactive nanofluid flow on stretching surface using numerical soft computing approach for thermal enhancement

ABSTRACT In this work, computational intelligence methodologies are used to investigate the trihybrid nanofluid, a new theoretical model with remarkable thermal transmission properties to enhance liquid thermal performance. The nanostructure Cu, Al2O3, and TiO2 were immersed in the base liquid (C2H6O2) to produce (Cu + Al2O3 + TiO2/C2H6O2) trihybrid nanofluid. In a Darcy-Forchheimer porous medium over a stretching Riga sheet, this study examines the electromagnetic ternary hybrid nanofluid flow under various slip situations. The study takes into account the complex interactions between a number of variables, including as viscous dissipation, radiation, heat sources, and chemical reactions. Similarity transformations are used to convert complex partial differential equations for flow, energy, and concentration into nonlinear ordinary differential equations. The highly nonlinear equations of the problem are solved numerically with the use of techniques from the bvp4c approach. The results of the bvp4c method produce the reference dataset required for the Levenberg-Marquardt backpropagation of neural networks (LMBNN). The neural network performance is validated using regression analysis, mean square errors, and error histogram data. The model problem’s consistency and precision are evaluated using the absolute error, which is given for each model instance at around 10−06–10−08, 10−05–10−10 and 10−06 05–10−09. In order to reduce mean square error, the nonlinear fluid dynamics system’s numerical solutions have been taken into consideration. Using the comparative configurations of MSE, error histograms, state transitions, correlation, and regression, the reliability and competence of the stochastic technique are verified.

Impact of rock heterogeneity on reactive flow during acid stimulation process

Acid stimulation within carbonate rocks represents a crucial aspect of reactive flow applications in subsurface porous media and has been widely used in carbonate reservoir development attributed to its rapid effectiveness and cost-efficiency. This study is motivated to investigate further the impact of rock heterogeneity on the acid stimulation process. The two-scale continuum model is employed for capturing mass, momentum, and energy transfer during the acid stimulation process. The core-scale model is expanded to consider the specific composition of solid minerals, including reactive minerals such as calcite and dolomite and non-reactive ones like quartz and clay. A heterogeneity generator is developed by coupling with the open-source geostatistical program to produce different heterogeneous parameters using random seeds with varying spatial correlation lengths. Sensitive cases are performed to present an investigation into the influence of mineral composition and matrix heterogeneity on the acid stimulation process. Results show that the typical results of acid stimulation are closely tied to different heterogeneity conditions. The optimum conditions for acid stimulation are sensitive to the concentration of reactive components. The optimum acid injection rate declines as dolomite content increases, while the corresponding acidizing breakthrough volume reduces with higher calcite levels. The presence of mineral layers, especially in horizontal distributions, complicates acid fluid efficiency due to the competitive reaction between calcite and dolomite. Compared to the heterogeneous distribution of minerals, matrix heterogeneity plays a critical role in acid fluid consumption efficiency. Increasing heterogeneity leads to significant reductions in breakthrough volumes, largely governed by the correlation length.

Fabrication of diamond film under low methane concentration by hot filament chemical vapor deposition with magnetic field assistance

This study focused on improving diamond film growth through hot filament chemical vapor deposition (HFCVD) with an innovative method, magnetic field assistance. The effects on diamond films were thoroughly investigated using a combination of experiments and simulations. The results of scanning electron microscopy (SEM), Raman spectroscopy, and X-ray diffraction (XRD) all showed significant improvements in nucleation rates, film thickness, and grain size, particularly for grains with (111) orientation, when exposed to a 400 mT magnetic field during HFCVD compared to non-magnetic conditions. Magnetic field application in HFCVD was found to promote the formation of larger diamond grains and increase the film growth rate by nearly 45 %. Concurrent Finite Element Method simulations confirmed that the magnetic field improved reactive gas flow and temperature distribution across the substrate, which was consistent with experimental results. These findings suggest that magnetic field assistance in HFCVD may mitigate the limitations of bias assistance, such as the antenna effect, overheating, and stress imbalance. This approach is especially useful for substrates with complex geometries, such as the sharp edges of cutting tools, as it promotes even film growth.

Optimization and test of a ring-ring typed atmospheric pressure plasma jet for optical fabrication

In recent years, the atmospheric pressure plasma jet (APPJ) has gained considerable attention in the field of optical fabrication because the chemical etching approach offers the advantage of avoiding mechanical damage to workpieces. This paper presents the development of an atmospheric pressure plasma machining system with a ring-ring typed APPJ, which exhibits several favorable characteristics. It has a relatively low processing temperature, no electrode corrosion, no plasma contamination, and a long discharge plume, etc. Optimization of the dimensional parameters and analysis of reactive gas flow rate are conducted through experimental investigations. Comparative experiments are carried out with the commonly used needle-ring typed APPJ, revealing significant improvements of the ring-ring typed APPJ, i.e., a fourfold increase in machining distance, a tenfold increase in machining efficiency, and a 58% enhancement in the stability of the material volumetric removal rate. Furthermore, on-line temperature monitoring of the footprint has been achieved due to the specific traits of the extended discharge plume. Fabrication experiments are conducted to demonstrate the significant correlation between the temperature and material removal rate, which shows the possibility of improving the accuracy of optical fabrication based on the ring-ring typed APPJ.

Study of field distribution characteristics in CVD reactors and enhanced growth of SWNCT

The low efficiency of growing single-walled carbon nanotubes (SWCNT) poses a barrier to their application in high-performance electronic devices. However, it is difficult to control the uniform growth of SWCNT in a floating catalytic reactor due to the complex parameter control. Therefore, it is essential to enhance the growth of SWCNT in the floating catalyst chemical vapor deposition (FCCVD) process. In the present work, the influence of the reactive flow field on the growth of SWCNT, which is often neglected, is revealed. To address this issue, this work combines experiments and simulations to obtain the characteristics of the field distribution within the reactor and the trend of the products. The results of the flow field analysis indicate that thermal buoyancy is the cause of SWCNT growth limitation in FCCVD. By weakening the thermal buoyancy, a homogeneous reaction field is obtained; vortices in the flow field are reduced or even disappear; the temperature field is more homogeneous, and, importantly, the crystallinity of SWCNT is enhanced (IG/ID up to 20-fold). In addition, the decomposition process of the carbon source is also enhanced, thus suppressing the generation of by-products. Based on the results of the small tube experiments, both the increase in temperature and the decrease in residence time increased the IG/ID. Furthermore, the distributions of the maximum and minimum diameters in SWCNT imply variations in the growth modes of SWCNT at different temperatures.

Multiphase reactive flow and heat transfer simulations in the unlocking components of an ultra-low shock pyrotechnic separation nut

This study presents a multiphase reactive flow and conjugate heat transfer model for the unlocking components in an ultra-low shock pyrotechnic separation nut. The process of the shape memory alloy (SMA) tube heated by the heat released from the combustion of the micro gas pyrotechnic charges was simulated. The established model was validated by comparing the simulation with experimental results for the temperature of the outer wall of the SMA tube. Then, the detailed ignition and combustion of micro gas pyrotechnic charges, transient flow of combustion products, and heat transfer in the SMA tube were analyzed. The effects of the amount and burning rate of micro gas pyrotechnic charges on the unlocking time were investigated. It is found that the unlocking time decreases with an increase in the amount of micro gas pyrotechnic charges. Moreover, the reduction range of the unlocking time decreases with the increase in the amount of micro gas pyrotechnic charges. Reducing the differences in the burning rate contributes to enhancing the consistency of unlocking time.

Microcontinuum approach to multiscale modeling of multiphase reactive flow during mineral dissolution

Microcontinuum approach to multiscale modeling of multiphase reactive flow during mineral dissolution

Numerical comparison of nonlinear thermal radiation and chemically reactive bio-convection flow of Casson-Carreau nano-liquid with gyro-tactic microorganisms: Lie group theoretic approach

The current research presents a mathematical model to study the flow of a non-Newtonian magnetohydrodynamics (MHD) Casson-Carreau nanofluid (CCNF) over a stretching porous surface, considering mass and heat transport rates with Stefan blowing, non-linear thermal radiation, heat source-sink, chemical reaction, thermophoretic and Brownian motions, convective heating, Joule heating, motile microorganisms, and bio-convection. The presence of microorganisms is utilized to control the suspension of nanomaterials within the nanofluid. The current flow model has been rendered by the boundary layer approximation and we get the highly nonlinear partial differential equations (PDEs). These nonlinear PDEs are simplified by the novel Lie group theoretic method. The one-parameter Lie scaling method simplified the PDEs and convert it into the ordinary differential equations (ODEs). Numerical solutions for these ODEs are obtained using the bvp4c scheme built-in function in MATLAB, ensuring reliable outcomes for temperature, velocity, concentration, and motile microorganism density profiles. The numerical results are presented through graphs and compared with available data, showing good agreement. These numerical outcomes reveal several important flow characteristics. Rates of change for Nr are 0.0007 and 0.0005, and for Ω, they are −0.0754 and −0.0536, respectively. Similarly, the rate of change for Rb in both models is −0.002 and −0.0002. Analysis shows a positive impact of the bioconvection Rayleigh number in both models, notably higher for the Casson fluid compared to the Carreau fluid model. Buoyancy ratio parameter exhibits consistent rates of change, while the reduction in impact is more pronounced for the Casson fluid model in the case of the mixed bioconvection parameter. The mixed bio-convection parameter reduces momentum velocity for both Casson and Carreau fluids, whereas the Darcy parameter boosts fluid velocity. As the Newtonian heating parameter increases, the temperature velocity distribution of both fluids also increases. The concentration profile of both Casson-Carreau fluid phases declines as the heat source-sink parameter and Schmidt number increase. Microbial velocity shows a decrease with increasing R values, whereas the opposite trend is observed for the Peclet number Pe.

Synergetic optimization operation method for distribution network based on SOP and PV

The integration of distributed generation brings in new challenges for the operation of distribution networks, including out-of-limit voltage and power flow control. Soft open points (SOP) are new power electronic devices that can flexibly control active and reactive power flows. With the exception of active power output, photovoltaic (PV) devices can provide reactive power compensation through an inverter. Thus, a synergetic optimization operation method for SOP and PV in a distribution network is proposed. A synergetic optimization model was developed. The voltage deviation, network loss, and ratio of photovoltaic abandonment were selected as the objective functions. The PV model was improved by considering the three reactive power output modes of the PV inverter. Both the load fluctuation and loss of the SOP were considered. Three multi-objective optimization algorithms were used, and a compromise optimal solution was calculated. Case studies were conducted using an IEEE 33-node system. The simulation results indicated that the SOP and PVs complemented each other in terms of active power transmission and reactive power compensation. Synergetic optimization improves power control capability and flexibility, providing better power quality and PV consumption rate.

Heat and Mass Transfer in Unsteady Radiating MHD Flow of a Maxwell Fluid with a Porous Vertically Stretching Sheet in the Presence of Activation Energy and Thermal Diffusion Effects

The aim of this study is to analyze the effects of activation energy and thermal diffusion an unsteady MHD reactive Maxwell fluid flow past a porous stretching sheet in the presence of Brownian motion, Thermophoresis and nonlinear thermal. The non-linear partial differential equations that govern the fluid flow have been transformed into a two-point boundary value problem using similarity variables and then solved numerically by fourth order Runge–Kutta method with shooting technique. Graphical results are discussed for non-dimensional velocity, temperature and concentration profiles while numerical values of the skin friction, Nusselt number and Sherwood number are presented in tabular form for various values of parameters controlling the flow system. The present study is compared with the previous literature and found to be in good agreement.

An Improvised Modulation and Control Approach for Dual Active Bridge DC–DC Converter System

Aimed at the control and modulation of dual active bridge bi-directional dc (DAB-BIDC) converter, an unconventional approach is applied to explore its effect in symmetrical wave-based isolated dc-dc converters. The existing control schemes of DAB-BIDC converter with unified or optimal phase shift (UPS/OPS) modulation have the constraints like complex control schemes, light load efficiency, current stress, and reactive power. Since a 50 Hz, grid-connected conventional converter system uses the sinusoidal pulse width modulation method to minimize the requirement for passive filters. Similarly, this work investigates the same analogy for the high-frequency (HF) symmetrical wave converters to get effective modulation and control scheme for the DAB-BIDC converter. Furthermore, the proposed sinusoidal pulse width-phase shift (SPW-PS) modulation scheme has been implemented by the optimally derived control parameters using Lagrange's Multiplier Method (LMM) to minimize the reactive power flow and current stress reduction at the HF link. Therefore, the DAB-BIDC converter with the proposed modulation and control approach can be used for EV charging and solid-state transformers applications. Finally, the proposed work is validated using MATLAB simulation and experimental setup having turn ratio 36/12 V, fundamental frequency 5-kHz, and switching frequency 100-kHz for the experimental validation using OPAL-RT.

Thermal and mass transport investigation of magnetohydrodynamic reactive nanofluid flow utilizing Buongiorno’s model

The paper’s primary goal is to investigate mass and heat transfer processes in reactive nanofluid particles. Within Buongiorno’s model, three chemical reactions are discussed. The main subject is on the nanoparticle fractions at the boundary. The characteristics of [Formula: see text] and [Formula: see text] with regard to the nanoparticle fraction have been found to be passively rather than actively controlled at the boundary. To put it another way, these qualities naturally develop and are controlled by the circumstances at the boundary or interface where the nanoparticles interact with the surrounding medium. They are not the result of active manipulation or outside forces. The system of partial differential equations was converted into ordinary differential equations using similarity transformations. To solve the system of ODEs, they combined the shooting method with a numerical technique known as RK-Fehlberg. The study examines various physical parameters and their effects using graphs. The paper also contains a table showing how different parameters affect the regional Nusselt and Sherwood numbers. This enables a deeper comprehension of the impact that these variables have on the heat and mass transfer within the reactive nanofluid particles. Core findings: Examining three chemical reactions involving nanofluids has led to the study’s key discoveries. Additionally, it looks into how specific physical variables may affect the Nusselt and Sherwood numbers.

Role of Peroxiredoxin 1 Induced by Epstein-Barr Virus Infection in Nasopharyngeal Carcinoma.

Nasopharyngeal carcinoma (NPC), a common cancer in Southern China, is associated with Epstein-Barr Virus (EBV) infection. Although many therapies for NPC have been established, the definite role of EBV in NPC remains unclear. Therefore, this work focuses on LMP2A, a latent EBV gene, and investigates whether LMP2A is related to peroxiredoxin 1 (PRDX1) in EBV-positive NPC. The mRNA and protein expression levels of LMP2A, PRDX1, and beta-catenin were compared in patient samples. To identify molecular mechanisms, EBV-negative NP69 and EBV-positive C666-1 NPC cell lines were used. After making an agar cell block for cell slides, the intensity of LMP2A expression was observed visually. To measure the level of reactive oxygen species, both fluorescence microscope and flow cytometry were used. To investigate the intracellular signaling molecular mechanisms with and without the LMP2A gene, reverse transcription polymerase chain reaction and western blotting were used. Both patient samples and cells of nasopharyngeal carcinoma infected with EBV had increased expression of LMP2A compared with controls, and high ROS levels were identified. Cell viability assay showed that LMP2A promoted cell growth by regulating gene expression. Furthermore, LMP2A induced the expression of PRDX1 and beta-catenin. LMP2A also increased the expression of both cyclin B1 and cyclin D1. In NPC cells, PRDX1 and beta-catenin were regulated through LMP2A expression, which reduced cell growth through cell cycle-related gene expression. This study suggests that LMP2A could be a target molecule for inhibiting cancer progression in NPC cells infected with EBV.

Dufour and Soret diffusions phenomena for the chemically reactive MHD viscous fluid flow across a stretching sheet with variable properties

The flow of fluid on a slandering stretchable sheet with variable thickness can have several engineering applications like design and optimization of, aerodynamic structures such as wings and airfoils, wind turbine blade design, efficient cooling systems for electronic devices, power plants and industrial processes. Keeping in view these important applications, this work explores Darcy-Forchheimer flow of magnetohydrodynamics (MHD) fluid across a slandering stretchable sheet with variable thickness in the presence of chemically reactive effects, and heat source. The flow is impacted by the combined influences of diffusive-thermo and thermo-diffusive phenomena. The fluid is set into motion along x-axis due to the stretching behavior of the sheet with y-axis as normal to it. Similarity transformations are employed to convert the modeled equations into nonlinear ordinary differential equations. It has observed as outcomes of this study that velocity distribution has augmented with expansion in viscosity factor and has declined with growth in permeability factor, inertia factor, and magnetic factor for both scenarios h1=0.0 and h1=0.5 where the impacts are more significant for the scenario h1=0.0. Thermal distribution has declined with augmentation in Prandtl number, permeability factor and Dufour number while has upsurge with escalation in thermal source factor for both scenarios h2=0.0 and h2=0.5. Concentration distribution has diminished with escalation in Schmidt number, chemical reactivity factor and has augmented with growth in Soret factor for both the scenarios h3=0.0 and h3=0.5 with more significant impacts in the scenario h3=0.0. Stream lines and contour lines for fluid flow have also sketched for the scenarios h1=0.0 and h1=0.5 as well as for M=0.0 and M=2.0. Validation of the proposed model and the methodology has ensured through comparison with fine agreement amongst current results and previously published work.

Delayed Detached-Eddy Simulations of Rough-Wall Turbulent Reactive Flows in a Supersonic Combustor

Reactive delayed detached-eddy simulations (DDESs) of hydrogen injection into a confined transverse supersonic flow of vitiated air are conducted. The corresponding conditions were studied in the LAPCAT-II combustor, which—due to thermal coating—exhibits non-negligible wall roughness. Its effects are taken into account with the equivalent sand-grain roughness model, and, to the best of the authors’ knowledge, it is the first time that this modeling framework is considered within the DDES framework to simulate turbulent reactive flows. Two operating conditions are considered, which differ in the value of the momentum ratio between the hydrogen and vitiated air inlet streams, thus leading to two distinct values of the operating equivalence ratio (ER). For its smallest value, smooth combustion is subject to a preliminary thermal runaway period, while for its largest value, combustion is more strongly intertwined with shock wave dynamics and boundary-layer separation. Since it features large subsonic regions, which are characteristic of situations close to thermal choking, the latter is referred to as the sudden or partially choked combustion mode. Computational results are assessed through comparisons with available experimental data for both operating conditions. The main mechanism through which wall roughness alters the combustion development lies in the reduction of the effective cross-sectional area that is induced by boundary-layer thickening. For the largest ER value, DDES conducted with the sand-grain roughness model does recover the partially choked combustion mode, while smooth wall (i.e., standard) DDES does not.