Transient Computational Fluid Dynamics Research Articles

3D Modelling of Layer-by-Layer Heat and Mass Transfer in Wire Arc Additive Manufacturing

A comprehensive three-dimensional transient computational fluid dynamics (CFD) model was developed to analyze the thermophysical phenomena in the arc wire additive manufacturing (WAAM) process. The model includes droplet impact, gravity, heat and mass transfer, molten metal flow, and solid-liquid phase changes. By integrating the mass, energy, momentum, and Volume of Fluid (VOF) equations, a layer-by-layer additive process was successfully simulated. The accuracy of the model was validated by comparing the simulation results of single-pass single-layer weld beads at three welding positions with experimental data. The established model was utilized to quantitatively investigate the effects of three crucial welding process parameters–welding direction, droplet transfer frequency, and initial temperature–on the multi-layer cladding process. These findings suggest that the use of opposite welding directions in two adjacent layers can result in a well-distributed overall morphology of the weld bead. Moreover, the high initial droplet temperature enhanced the inclination of the weld bead morphology while decreasing the height of each layer. However, the high droplet transfer frequency caused both the height and width of the weld to increase. This research contributes to explaining the formation mechanism of the multi-layer cladding process and offers insights for improving weld bead morphology. This provides valuable theoretical guidance for the process optimization and control of arc additive manufacturing technology.

Nomograph derivation for underwater sour gas releases in shallow waters based on computational fluid dynamics simulations

Ruptured underwater pipelines releasing sour gas (i.e., natural gas with high concentrations of H2S) pose significant threats to environmental safety due to their toxic and contaminative properties. This study suggests a transient Eulerian-Eulerian multiphase computational fluid dynamics (CFD) model for assessing the environmental impact of sour gas releases in shallow, ecologically sensitive waters. Employing the Realizable k-ε turbulence model and additional bubble plume mechanisms, the model was rigorously validated against well-documented experimental data, showing high levels of agreement across multiple metrics. Key environmental safety parameters—such as rise time and H2S surface gas concentration, indicative of toxic exposure risk to aquatic life and human health—were extracted for multiple release scenarios. To present generalized and easily accessible data, these parameters were nondimensionalized and incorporated into a nomograph, enabling environmental risk assessments to be conducted four orders of magnitude faster than with high-fidelity simulations. The study emphasizes the nomograph's utility in rapid, environmentally relevant risk assessment and emergency planning for mitigating the impact of sour gas spills. An error and sensitivity analysis revealed uncertainties of ±7 % for rise time and ±58 % for surface gas concentration, pinpointing avenues for future research.

Transient Performance Analysis of Centrifugal Left Ventricular Assist Devices Coupled With Windkessel Model: Large Eddy Simulations Study on Continuous and Pulsatile Flow Operation.

Computational fluid dynamics (CFD) simulations are widely used to develop and analyze blood-contacting medical devices such as left ventricular assist devices (LVADs). This work presents an analysis of the transient behavior of two centrifugal LVADs with different designs: HeartWare VAD and HeartMate3. A scale-resolving methodology is followed through Large Eddy Simulations, which allows for the visualization of turbulent structures. The three-dimensional (3D) LVAD models are coupled to a zero-dimensional (0D) 2-element Windkessel model, which accounts for the vascular resistance and compliance of the arterial system downstream of the device. Furthermore, both continuous- and pulsatile-flow operation modes are analyzed. For the pulsatile conditions, the artificial pulse of HeartMate3 is imposed, leading to a larger variation of performance variables in HeartWare VAD than in HeartMate3. Moreover, CFD results of pulsatile-flow simulations are compared to those obtained by accessing the quasi-steady maps of the pumps. The quasi-steady approach is a predictive tool used to provide a preliminary approximation of the pulsatile evolution of flow rate, pressure head, and power, by only imposing a speed pulse and vascular parameters. This preliminary quasi-steady solution can be useful for deciding the characteristics of the pulsatile speed law before running a transient CFD simulation, as the former entails a significant reduction in computational cost in comparison to the latter.

Transient Flow Characteristics of a Pressure Differential Valve with Different Valve Spool Damping Orifice Structures

Lubrication system failure is a significant cause of in-flight shutdown incidents in aviation engines. The pressure differential valve, an essential component of a certain type of aviation engine lubrication system, is responsible for controlling the flow rate and pressure of the lubricating oil. Comprehending the transient flow characteristics of the pressure differential valve is of paramount importance for the secure operation of lubrication systems. This paper establishes a transient flow model of a pressure differential valve based on a transient computational fluid dynamics (CFD) method, and the experimental validation demonstrates the effectiveness of the computational model. The internal flow characteristics of the differential pressure valve at different stages during the opening process were studied. Additionally, four transient lubricating oil flow models with different valve spool damping orifice were established to analyse the impact of damping orifice structure on valve spool movement characteristics, pressure control characteristics, and flow field distribution. The results indicate that when the diameter of the valve spool damping orifice increases from 0.3 mm to 1.0 mm, the valve spool displacement and fluid force increase by 88 % and 20 %, respectively. Meanwhile, the peak valve spool velocity, peak oil supply pressure, and steady-state value decreased by 15 %, 29 %, and 34 %, respectively. As the length of the valve spool damping orifice increases from 0.894 mm to 4.0 mm, the growth rate of valve spool displacement and fluid force gradually decreases, with the peak valve spool velocity decreasing by 7 %. This study has potential significance for the structural optimization and application of pressure differential valve in lubrication systems.

Integrated CFD-FEM approach for external gear pump vibroacoustic field prediction

In this work, a three-dimensional fluid-structural and vibro-acoustics coupled model of a gear pump is presented. Gear pumps represent the majority of the positive displacement machines used for flow generation in fluid power systems. Typically, the dynamics of gear pumps are dependent on the characteristics of the fluid dynamics inside the pump, which translates into vibrations to the housing. These vibrations then propagate to the surrounding medium and emit sound. The purpose of this study is to propose a three-dimensional fully integrated computational model to simulate the complete gear pump behaviour from the fluid dynamics to the structural vibrations, up to the vibroacoustic response. In this hybrid configuration, a transient CFD (Computational Fluid Dynamics) model is first developed to simulate the 3D flow field with a deforming and re-meshing approach to take into account the variation of the volume between the gears. Second, the internal pressure field calculated at each time step is then used as a loading into a structural FEM (Finite Element Method) model of the gear pump to compute the actual stresses and deformations of the housing. Third, the results of the structural response are used as excitation in a vibroacoustic sub-model to simulate the radiated noise using a high-order FEM technique. The comparison between the numerical and experimental flow curves validates the CFD model. The sound power calculations from the vibroacoustic model show good comparison with the sound intensity measurements around the pump casing, confirming the validity of the proposed coupled model. The described CFD-FEM approach proves to be a powerful gear pump design tool: it provides a reliable estimate of gear pump working parameters such as fluid power and vibroacoustic characteristics, starting from the CAD (Computer-Aided Design) geometry of the components. Furthermore, being one of the first multi-domain simulation models of a gear pump, this work can be useful to researchers as a starting point to correlate the noise emitted with the internal flow in full 3D conditions.

Numerical investigation of unsteady heat transfer from a vertical helical coil

A comprehensive investigation was conducted utilizing three-dimensional transient Computational Fluid Dynamics (CFD) to analyze conjugate heat transfer, with a specific focus on determining the cooling time of a hot vertical helical coil. The heat transfer characteristics of the helical coil are assessed numerically with respect to parameters within certain ranges such as Rayleigh number 104≤Ra≤108, surface emissivity 0≤ε≤1, and geometrical parameters of the coil, such as coil-to-rod diameter ratio 8≤D/d≤24, and pitch-to-rod diameter ratio 3≤p/d≤7.5. Furthermore, a lumped heat capacitance model is also proposed, which significantly reduces computational time while maintaining accuracy by utilizing the steady-state correlation of Nusselt number vs. Rayleigh number (Nu vs. Ra) and other pertinent geometrical parameters of the coil. Comparative analysis between the lumped heat capacitance model and transient simulations reveals a remarkable correspondence, with deviations not exceeding 2%. Validation of the computational model is conducted against experimental data, showing good agreement. Results indicate that coils with higher pitch-to-rod diameter ratio (p/d) and coil-to-rod diameter ratio (D/d) dissipate heat more quickly, while higher initial Rayleigh numbers lead to faster cooling rates. Temperature distribution and Nusselt number variations during the cooling process are analyzed and compared between steady and unsteady behavior. The study provides valuable insights into the cooling behavior of helical coils, crucial for industrial applications requiring efficient heat transfer.

Transient investigations of teeth on rotor and teeth on stator modified labyrinth seals

Teeth-on-rotor (TOR) and teeth-on-stator (TOS) layouts are compared in this paper to explore better arrangement for different labyrinth seals. The diaphragm labyrinth seal (DLS) and hole diaphragm labyrinth seal (HDLS) are both redesigned into TOR and TOS layouts. To accurately predict the rotordynamics and leakage performance of different seals, a one-motion transient computational fluid dynamics (CFD) method based on the simplified multi-frequency transient method is proposed. A comparison of the experimental results, two-motion transient CFD method and proposed method showcase the better accuracy of the current method in rotordynamic performance prediction. The results shows the better rotordynamic characteristics of the TOS layout for different layouts and of the HDLS type seals for three labyrinth type seals. Even though, the TOR layout cannot increase the stability of the rotor system, a clear circumferential velocity reduction in the DLS and HDLS seals can be observed in both the TOS and TOR layouts. However, the changes in leakage performance for DLS and HDLS seals are different from those for traditional LSs. Unlike TOR-LS and TOR-HDLS, which exhibit relatively large increases in leakage compared with the TOS layout, TOR-DLS achieves a maximum 1.7% leakage reduction at a 15000 rpm rotation speed. A decrease in the jet flow length and increase in the turbulence kinetic energy in TOR-DLS compared with those in TOS-DLS further explain this abnormal phenomenon.

Three-dimensional transient CFD simulation of lignite chemical looping gasification in a circulating fluidized bed

In this work, a full-loop 3D computational fluid dynamics (CFD) numerical simulation of the chemical looping gasification (CLG) process of lignite in a circulating fluidized bed (CFB) was performed using a two-fluid Eulerian-Eulerian model. The results showed that the CFD simulation effectively captured the axial and radial velocities of the particles. More radial flow occurred in the bottom part of the riser and inside the cyclone. The exothermic reaction became dominant within 7s, while the heat-absorbing reaction became dominant between 7 and 15s. The aggregation regions of syngas moved up with that of the high-temperature zone, and CO was the main contributor to the syngas. The particle size in the range of 175–225 μm was inversely proportional to the size of the average heat transfer coefficient (HTC) in the riser. Extremely small particle size saturated the bed, suppressing the HTC. The peak of the HTC was 387.7 W/(m2·K), which occurred in the upper-middle region of the riser and reached. The maximum HTC average value was 180.6 W/(m2·K). Finally, experimental data were used to verify the reliability of the model.

Flow analysis and sensitivity study of vertical-axis wind turbine under variable pitching

The general frame of the present study falls under the umbrella of ongoing research and innovation in wind energy technology to improve the efficiency and reliability of vertical-axis wind turbines (VAWTs) in terms of design and control. While blade pitching is foreseen as a solution to minimize boundary layer separation and maximize the lift force during the entire cyclic blade operation (effectively enhancing the performances of VAWTs), conclusive research on active blade pitching mechanisms in low wind speed regions is limited because of the 3D complex aerodynamic around VAWT blades. The paper reports a holistic study on active blade pitching solutions to enhance the performance of H-rotor Darrieus VAWTs for different turbine design parameters, i.e., geometrical (different number and airfoil thickness, and solidity) under several operational conditions (Reynolds number (Re), and tip speed ratio (TSR)). In this study, a variable blade pitching technique, adapted for periodic variation of the angle of attack, is incorporated in a high-fidelity two-dimensional VAWTs transient Computational Fluid Dynamics (CFD) model to eliminate the dead band of small-scale wind turbines operating at low wind speed regions and increase the performance coefficient Cp at different TSRs. Sliding mesh and remeshing to capture the blade pitching are used to manage the rotor rotation. The CFD model is validated against experimental data from the literature. The results indicate that the local widening of the angle of attack (AoA) for each NACA0015 airfoil produces a Cp of 0.44, which represents 81% enhancement in the Cp at TSR of 1.5. Moreover, the study shows that increasing the number of blades or extending the blade chord length can eliminate the dead band of wind turbines. Furthermore, the maximum possible torque for 3- and 4-bladed rotor designs is achieved using the variable pitching mechanism.

In silico hemodynamical simulations show additional benefits of artery wall softening induced by antihypertensive drugs

Background and objectivesAge-related arterial stiffening increases peripheral resistance and decreases arterial distensibility, thus contributing to hypertension, an important risk factor of atherosclerosis. It causes abnormal blood flow, endothelial dysfunction, higher pulse wave velocity, and consequently elevated pressure wave amplitude. MethodsThis paper presents the influence of these changes via multiscale 3D-0D transient computational fluid dynamics simulations of blood flow in five patient-specific geometries of human carotid bifurcation using archetypal flow waveforms for young and old subjects. ResultsThe proposed model shows a significant decrease in the time-averaged wall shear stress (TAWSS) for the old archetypal flow waveform. This is in good agreement with clinical data on a straight segment of common carotid arteries available for young and old subjects. Moreover, our study showed that the decrease of area-averaged TAWSS related to the old flow waveform is much more pronounced (2.5 ÷ 4.5 times higher) at risk areas (areas showing TAWSS below its threshold value of 0.48 Pa) than in straight segments commonly considered in clinical studies. ConclusionsSince arterial stiffness can be lowered through long-term usage of any of the five basic groups of antihypertensives, possible benefits of such medical therapy could be not only lowering blood pressure and peripheral resistance but also in increasing the TAWSS and thus attenuating an important mechanism of the atherosclerotic process.

Numerical and experimental analysis of instability in high temperature packed-bed rock thermal energy storage systems

Due to heat losses of preferential areas of packed-bed energy storage systems, transverse temperature variations may occur during the charging, discharging and standby processes. Furthermore, the heat losses of preferential areas of the storage tank cause a lower pressure drop in these areas resulting in an increased mass flow rate and further cooling, and thereby an enhanced transverse temperature variation, in a positive feedback loop – a phenomenon called instability. The transverse temperature variations may deteriorate the performance and thereby the economic feasibility of packed-bed energy storage systems. In this paper, numerical and experimental investigations of an air-based packed-bed rock thermal energy storage system for large-scale high temperature applications are presented. The objective of the study is to predict the instability and to analyze the effect of different standby durations and storage size on the instability of the air-based packed-bed system. Transient axisymmetric computational fluid dynamics models were developed for the standby and discharging processes of the packed-bed thermal energy storage systems. In addition, experimental investigations were carried out at a test facility located at Stiesdal Storage, Denmark, using magnetite rocks as heat storage material and air as heat transfer fluid. The results suggest that the numerical predictions are in good agreement with the test data. The instability phenomenon is found to increase with the standby duration, resulting in a maximum difference of 161 K between the maximum rock temperature and the outlet air temperature for a standby period of 10 h followed by a discharging process. Moreover, the results indicate that the maximum difference between the rock temperature and outlet temperature is 73 K and 56 K for a reduced-scale and a full-scale system (no standby period), respectively.

Impact of wind-driven mixed convection on the performance of passive solar desalination with PCM heat storage in varied Moroccan climates

Mixed convection flows are commonly observed in various technological and industrial applications, including solar stills that are exposed to wind currents and other weather conditions. Combined free and forced convection flows can significantly improve the productivity of solar still devices, making them of practical interest. In fact, a passive solar desalination system with heat storage material is investigated in six climate zones of Morocco and presented by six cities namely: Tangier, Rabat, Ifran, Marrakech, Meknes and Errachidia. This study aims to analyze the effect of mixed convection on the inclined surface of solar desalination systems. Thus, a transient Computational fluid dynamics (CFD) model is developed and investigated under the instantaneous climatic data of the different cities aforementioned. The results indicate that forced convection dominated heat transfer during broad daylight, with the Nusselt number increasing as the Reynolds number increased. Overall, the productivity in Tangier city was found to be significantly higher than that of Rabat, Meknes, Marrakech, Ifran, and Errachidia city, with increases of 45.02%, 50.48%, 23.48%, 83.31%, and 24.89%, respectively.

Effect of NaX Zeolite Mass and Baffle Presence on Copper Sorption

Sorption is often conducted in stirred batch reactors without assessing the impact of mixing on yield and costs. Operating the mixing in the batch reactor at a state of complete suspension, <i>i.e.</i>, at just suspended impeller speed, <i>N</i><sub>JS</sub>, is a compromise between these conflicting goals. Therefore, copper sorption on NaX zeolite using a pitched blade turbine was conducted in both baffled and unbaffled batch reactors at <i>N</i><sub>JS</sub>. Maintaining constant impeller to reactor diameter ratio (<i>D</i>/<i>d</i><sub>T</sub> = 0.32), and impeller off-bottom clearance (<i>C/H</i> = 0.33), kinetic sorption experiments were performed. Besides kinetic sorption experiments and the kinetic analysis of data obtained, to gain insight into the hydrodynamic behaviour of the system, transient multiphase computational fluid dynamics simulations (CFD) were performed.<br /> The <i>N</i><sub>JS</sub> speed is related to the particle settling speed, wherein a higher zeolite suspension mass concentration requires a greater NJS speed, resulting in increased energy consumption. The differences in <i>N</i><sub>JS</sub> speeds for the investigated zeolite suspension mass concentrations were found to be insubstantial, and therefore, the increase in mixing intensity for the tested systems was not deemed significant. Regardless of the zeolite mass used, the values of <i>N</i><sub>JS</sub> and <i>P</i><sub>JS</sub> (mixing power consumption) were consistently higher in the unbaffled reactor. The hydrodynamic conditions employed were found to have no significant effect on the maximum amount of copper sorbed or process efficiency, but was significantly affected by zeolite mass. The kinetics were affected by both, and, generally, sorption occurred faster in the unbaffled reactor.

Positive Pressure and Negative Pressure Irrigation Dynamics with Different Needle Designs Using Computational Fluid Dynamics

This study aimed to investigate the irrigation dynamics of the positive pressure side-vented (SV) needle, EndoVac (micropores) needle and modified apical negative pressure (mANP) open-ended needle using computational fluid dynamics (CFD). A simulation of a prepared root canal (conical frustum) of 15 mm length with an apical diameter of 0.40 mm following Protaper F4 apical preparation was created using three-dimensional (3D) CAD software. The 3D simulated needle of SV 30G needle, EndoVac with micropores needle and mANP, 30G flat open-ended needle were also created. The irrigation dynamics were evaluated through transient CFD simulations. In addition, the irrigation dynamics of mANP at 0.2 mm, 0.5 mm, and 1.0 mm short from the working length were also assessed. The EndoVac and mANP showed negative apical static pressure and streamline patterns able to reach the apical region, thus indicating negligible extrusion. Meanwhile, SV showed positive apical static pressure and almost nonexistent streamlines beyond the needle tip. The SV showed the highest wall shear stress (WSS) magnitude of 1030Pa whereas Endovac (161 Pa) and mANP1 (258 Pa). However, SV revealed lower average WSS (10 Pa) compared to mANP1 (13 Pa) and mANP2 (11 Pa). This is due to SV developed a localised maximum WSS opposite the open vent area only therefore, uneven distribution of WSS. The EndoVac system developed a localised maximum WSS in the pair of micropores furthest away from the apical. CFD analysis of the EndoVac, mANP and SV showed different technique approach, needle design and needle depths insertion affect the irrigation dynamics pattern and magnitude.

The importance of unsteady phenomena of ammonia/methane combustion in an experimental swirl burner: Comparison of steady-state and transient simulation results

Ammonia is a potential advanced green fuel. Combustion simulations play a crucial role in facilitating the usage of ammonia in existing combustion systems as a drop-in fuel. Choosing between the unsteady and steady simulation methods should be done carefully depending on the investigated phenomena. In this study, steady-state and transient Computational Fluid Dynamics simulations were performed using detailed chemistry of the Okafor mechanism for a wide range of ammonia/methane blend combustion under lean conditions. The results revealed that the steady-state simulations could provide close values to the unsteady mean results at the outlet in magnitude, while outlet temperature and intermediate species concentration slightly differ with ammonia concentration-dependent extents. The unsteady simulations provided valuable insights into the temporal evolution of the combustion and flow field characteristics, and the Root Mean Square and mean properties were evaluated comprehensively, indicating that the oscillations highly depend on the fuel composition. The model was validated using measurement data from the literature, including Particle Image Velocimetry, OH* chemiluminescence, and pollutant emission. The velocity and OH* distribution matched acceptably, while the CO, NO, and NO2 emissions were underpredicted, which implies necessary reaction model improvements.

Transient Computational Fluid Dynamics Analysis of Passive Cooling in a Building with Diurnal Radiative Cooling Material Coated onto Its Rooftop

Building cooling loads, which continue to increase with increasing global temperatures, are responsible for large quantities of greenhouse gas emissions. Radiative cooling (RC), whereby structures are cooled by emitting radiation in the atmospheric window, from 8–13 μm, to outer space, is a promising clean technology that can be used to meet ever‐increasing building cooling demands. However, the effects of using RC on the airflow velocity and temperature distributions within the occupied zone of buildings are yet to be investigated. Herein, computational fluid dynamics simulations are performed to study the transient airflow velocity and temperature distributions in buildings that are cooled using RC material on their rooftops. For idealized conditions when the thermal mass of the house is neglected, the results show that when the cooling power provided by the RC material is , and the average temperature of the occupied zone in the building is reduced from 295 K to about 293 and 289.7 K after two minutes, respectively. These rapid cooling rates were attained without exceeding head‐to‐ankle temperature differences of about 2.7 °C and with air flow velocities maintained below 19.0 cm s−1, which is consistent with a comfortable environment.

Rotordynamic characteristics of a novel labyrinth seal with partition walls and helical groove teeth

To improve the stability of the conventional labyrinth seal (LS), in this paper, four novel fully partitioned helically labyrinth seals (FPHGLS) were designed and they were in comparison with one FPPGLS. The influences of the preswirl ratio and the helical groove pitch on the leakage flow and rotordynamic characteristics were numerically investigated, using the transient computational fluid dynamics (CFD) method based on the multi-frequency elliptical whirling orbit model. The accuracy and availability of the present transient numerical method were demonstrated based on the experiment data. The results show that the partition walls design can significantly increase the direct damping and cross-coupling stiffness for labyrinth seals and the helical teeth design can significantly decrease the cross-coupling stiffness and tangential force. When the helical groove pitch is equal to the seal length, the leakage nearly remains unchanged. Compared to the baseline design (LS), the FPPGLS and the FPHGLS have similar and significantly larger direct stiffness and direct damping. The two designs possess positive direct stiffness throughout the frequency range. The FPPGLS and FPHGLS possess significantly higher direct damping (∼323.7% larger than LS). But the FPPGLS possesses the largest cross-coupling stiffness among three seals at two preswirl ratios. From preswirl ratio = 0.13–0.84, the cross-coupling stiffness of the FPHGLS decreases by 53.4-310.1% compared with the FPPGLS. Increasing the helical groove pitch increases both direct stiffness and direct damping and reduces cross-coupling stiffness, but it also leads to greater leakage losses. In general, the novel FPHGLS whose helical groove pitch is equal to seal length possesses superior rotordynamic characteristics and similar leakage characteristic. This work provides the reference of the seal design and safety operation for the turbomachinery.

Influence of impeller clearance, impeller size and baffles on copper sorption on zeolite NaX: Do the size and position really matter?

Even though optimal mixing parameters may significantly influence the sorption process and its costs, the influence of hydrodynamics on sorption in a batch reactor hasn't yet been adequately studied. In this study, the hydrodynamic conditions produced by pitched blade turbine (PBT) impellers of various diameters and positions in baffled and unbaffled reactors were investigated. The objective was to investigate their influence on the just suspended impeller speed (NJS), power consumption per zeolite mass and the sorption process at the same temperature, initial copper solution concentration, and zeolite particle size in all the experiments conducted. The results show that NJS generally decreases as impeller diameter increases and is lower in the reactor without baffles. A transient multiphase computational fluid dynamics model was developed to provide valuable insight into the complex flow kinetics and it was found that the further the impeller is from the bottom of the baffled reactor the wider is the secondary suspension flow and the intensity of the flow below the impeller decreases. For this reason, complete suspension of the NaX zeolite particles in the solution was achieved at a higher PBT impeller speed. Due to the swirling motion of the suspension, this phenomenon is not observed in the unbaffled reactor for all the impellers used besides the smallest one. The power consumption per zeolite mass, at the state of complete zeolite suspension, increases in baffled reactor and decreases in unbaffled reactor with increasing impeller diameter having significantly lower values in the unbaffled reactor. The significantly lower power consumption per zeolite mass in an unbaffled system could be attributed to, not only the generally lower NJS values, but also to the resistance force which baffles make to the tangential fluid flow. The Ritchie model and Mixed surface reaction and diffusion controlled adsorption kinetic model were used for the kinetic analysis of the experimental kinetic data. The kinetic results indicate that the process is faster when the impeller is at the standard of bottom clearance, regardless of the presence of the baffles.

Hot‐Metal Desulfurization Using Calcium Carbide and Calcium Oxide in Transfer Ladle: A Computational Fluid Dynamics Investigation

In this study, a 3D transient computational fluid dynamics (CFDs) model that simulates hot‐metal desulfurization (HMD) using calcium carbide and calcium oxide in an experimental‐scale ladle with a 70 kg capacity is presented. The model takes into account the efficiency of reagent‐particles‐penetrating carrier gas bubbles and is validated through experimental work, with an average difference of 7.06%. In this research, the effects of varying reagent particle sizes, hot‐metal temperatures, gas flow rates, and ladle design on desulfurization rates are discussed. The results indicate that when particle diameter decreases from 30 to 20.9 and 11.8 μm, desulfurization rates rise from 50.92% to 66.02% and 89.99%, respectively. Regarding hot‐metal temperature, a 100° range results in a final desulfurization rate difference of less than 3%. This study also reveals that increasing the carrier gas flow rate from 13 to 15 SLPM reduces the removal rate by 6.10%. As particle gas flow rate increases from 200 to 300 g min−1, the removal rate increases by 9.02%. In the lance arrangement analysis, the duo lance system demonstrates nearly identical desulfurization performance to the single‐center lance system, which outperforms the off‐center lance system.

Numerical investigation of the impact of injecting coke oven gas on raceway evolution in an ironmaking blast furnace

Using coke oven gas (COG) as a cost-effective alternative fuel in the ironmaking blast furnace has gained considerable attention. However, its dynamic impact on the raceway's shape and size remains to be determined. This study presents a comprehensive investigation using a 3D transient Computational Fluid Dynamics (CFD) model to study and compare the effects of injecting COG and reformed COG on the dynamic raceways of blast furnaces. The complex multiphase flow and thermochemical behaviours associated with the combustion of COG and reformed COG in the dynamic raceway are quantified and compared in terms of the evolution of the raceway profile, gas temperature, and species distribution when using different injection rates. The results indicate that injecting COG leads to forming a larger raceway size by 5 % compared to reformed COG. The gas temperature along the tuyere centerline exhibits higher values by 2 %−7 %, while the molar fraction of CO and CO2 increases by 30 % and 15 %, respectively. Moreover, the molar fraction of O2 and H2 shows a 3 % increase under similar injection rates. These findings help to understand the potential of reformed COG injection to further reduce carbon emissions compared to COG injection in blast furnaces.