| 1. |
- Akbarnejad, Shahin, et al.
(författare)
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Effect of Fluid Bypassing on the Experimentally Obtained Darcy and Non-Darcy Permeability Parameters of Ceramic Foam Filters
- 2017
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer. - 1073-5615 .- 1543-1916. ; 48:1, s. 197-207
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Tidskriftsartikel (refereegranskat)abstract
- Ceramic foam filters (CFFs) are used to remove solid particles and inclusions from molten metal. In general, molten metal which is poured on the top of a CFF needs to reach a certain height to build the required pressure (metal head) to prime the filter. To estimate the required metal head, it is necessary to obtain permeability coefficients using permeametry experiments. It has been mentioned in the literature that to avoid fluid bypassing, during permeametry, samples need to be sealed. However, the effect of fluid bypassing on the experimentally obtained pressure gradients seems not to be explored. Therefore, in this research, the focus was on studying the effect of fluid bypassing on the experimentally obtained pressure gradients as well as the empirically obtained Darcy and non-Darcy permeability coefficients. Specifically, the aim of the research was to investigate the effect of fluid bypassing on the liquid permeability of 30, 50, and 80 pores per inch (PPI) commercial alumina CFFs. In addition, the experimental data were compared to the numerically modeled findings. Both studies showed that no sealing results in extremely poor estimates of the pressure gradients and Darcy and non-Darcy permeability coefficients for all studied filters. The average deviations between the pressure gradients of the sealed and unsealed 30, 50, and 80 PPI samples were calculated to be 57.2, 56.8, and 61.3 pct. The deviations between the Darcy coefficients of the sealed and unsealed 30, 50, and 80 PPI samples found to be 9, 20, and 31 pct. The deviations between the non-Darcy coefficients of the sealed and unsealed 30, 50, and 80 PPI samples were calculated to be 59, 58, and 63 pct.
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| 2. |
- Burman, J., et al.
(författare)
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Synthetic boundary conditions using les for urban dispersion modelling
- 2017
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Ingår i: HARMO 2017 - 18th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, Proceedings. - : Hungarian Meteorological Service. ; , s. 788-792
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Konferensbidrag (refereegranskat)abstract
- Large Eddy Simulation with two sub-grid-scale models are used to simulate gas dispersion, utilizing alternatively constant values and synthetic turbulence at inflow boundaries. The results are compared with data from the JU2003 Atmospheric Dispersion Study in Oklahoma City. Turbulence statistics of the simulation is presented at two probe locations, one inside the city-core and one outside. In addition, comparisons with the measured concentration-data and maximum-values are conducted. It was found that in the core of the city, modeled turbulence is mainly determined by buildings and their configurations, and is only weakly affected by model type and assumed turbulence at inflow boundaries. Within the predicted flow-path, the tested models produce similar predictions of maximum concentration values, which in turn are similar to the experimental data. The results indicate that synthetic turbulence at the inflow boundary is less important when building generated turbulence dominate but it is important if not a local boundary layer is developed.
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| 3. |
- Ni, Peiyuan, 1987-, et al.
(författare)
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Numerical and Physical Study on a Cylindrical Tundish Design to Produce a Swirling Flow in the SEN During Continuous Casting of Steel
- 2017
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Science and Business Media LLC. - 1073-5615 .- 1543-1916. ; 48:5, s. 2695-2706
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Tidskriftsartikel (refereegranskat)abstract
- A new tundish design was investigated using both water model experiments and numerical simulations. The results show that the Reynolds Stress Model simulation results agree well with the Particle Image Velocimetry-measured results for water model experiments. A strong swirling flow in the Submerged Entry Nozzle (SEN) of the new tundish was successfully obtained, and the tangential velocity in the region near SEN inlet could reach a value of around 3.1 m/s. A high value of the shear stress was found to exist on the SEN wall, due to the strong swirling flow inside the SEN. This large shear stress leads to the dissipation of the rotational momentum of the steel flow. Thus, the maximum tangential velocity of the steel flow decreases from 3.1 m/s at around the SEN inlet to 2.2 m/s at a location close to the SEN outlet. In addition, the near-wall region has a high pressure, which is larger than the atmospheric pressure, due to the centrifugal effect. The calculated swirl number, with the value of around 1.6 at SEN inlet, illustrates that the current design can produce a similar strong swirling flow compared to the swirl blade method and the electromagnetic stirring method, while this is obtained by simply changing the steel flow path in tundish instead of using additional device to influence the flow.
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| 4. |
- Ni, Peiyuan, et al.
(författare)
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Transport and Deposition of Non-Metallic Inclusions in Steel Flows- A Comparison of Different Model Predictions to Pilot Plant Experiment Data
- 2017
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Ingår i: Steel Research International. - : Wiley-VCH Verlagsgesellschaft. - 1611-3683 .- 1869-344X. ; 88:12
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Tidskriftsartikel (refereegranskat)abstract
- Inclusion behavior during a ladle teeming process is investigated. A Lagrangian method is used to track different-size inclusions and to compare their behaviors in steel flows, solved by the realizable k-epsilon model with SWF (Standard Wall Function), realizable k-epsilon model with EWT (Enhanced Wall Treatment), and RSM (Reynolds Stress Model). The results show that inclusion tracking based on the realizable k-epsilon model with SWF to predict the steel flow does not agree with the data fromplant experiments. The predicted number of inclusions touching the wall shows almost no dependence on inclusion size. This is due to that the boundary layer is not resolved. The inclusion deposition predicted using the realizable k-epsilon model with EWT and the RSM model to predict the steel flow generally agrees with the experimental observations. However, the large size inclusion deposition is over-predicted when using the realizable k-epsilon model with EWT. More specifically, the prediction for 20 mu m inclusions is three times larger than that with the RSM. This is due to that this model cannot calculate the anisotropic turbulence fluctuations. In summary, the turbulence properties in the near-wall boundary layer are found to be very important for a good prediction on inclusion deposition.
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