Flow measurements are performed in a slab model for continuous casting of steel under the influence of a ruler type Electromagnetic Brake (EMBr). The Mini-LIMMCAST facility utilizes the low melting ...GaInSn alloy for flow modeling. Two-dimensional velocity distributions in the center plane of the rectangular mold with a cross section of
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are determined by means of the ultrasound Doppler velocimetry. This study especially focuses on the influence of the vertical position of the EMBr and its magnetic flux density as well as the effect of different immersion depths of the submerged entry nozzle. The horizontal flow velocity just below the free surface can effectively be reduced by choosing an optimal position of the EMBr, while an improper positioning even increases the near-surface velocity compared to the case without activated brake. A general braking effect of the EMBr on the submerged jet is not observed. The decisive mechanism for controlling the near-surface flow results from a modification of the jet geometry and a reorganization of the flow field. In terms of an effective flow control an appropriate positioning of the EMBr has at least the same significance as the regulation of the magnetic field strength.
The flow structure in the mold of a continuous steel caster has a significant impact on the quality of the final product. Conventional sensors used in industry are limited to measuring single ...variables such as the mold level. These measurements give very indirect information about the flow structure. For this reason, designing control loops to optimize the flow is a huge challenge. A solution for this is to apply non-invasive sensors such as tomographic sensors that are able to visualize the flow structure in the opaque liquid metal and obtain information about the flow structure in the mold. In this paper, ultrasound Doppler velocimetry (UDV) is used to obtain key features of the flow. The preprocessing of the UDV data and feature extraction techniques are described in detail. The extracted flow features are used as the basis for real time feedback control. The model predictive control (MPC) technique is applied, and the results show that the controller is able to achieve optimum flow structures in the mold. The two main actuators that are used by the controller are the electromagnetic brake and the stopper rod. The experiments included in this study were obtained from a laboratory model of a continuous caster located at the Helmholtz-Zentrum Dresden Rossendorf (HZDR).
Flow control of liquid metals based on the actual flow condition is important in many metallurgical applications. For instance, the liquid steel flow in the mould of a continuous caster strongly ...influences the product quality. The flow can be modified by an electromagnetic brake (EMBr). However, due to the lack of appropriate flow measurement techniques, the control of those actuators is usually not based on the actual flow condition. This article describes the recent developments of the Contactless Inductive Flow Tomography (CIFT) towards a real-time monitoring system, which can be used as an input to the control loop for an EMBr. CIFT relies on measuring the flow-induced perturbation of an applied magnetic field and the solution of an underlying linear inverse problem. In order to implement the CIFT reconstructions in combination with EMBr, two issues have to be solved: (i) compensation of the effects of the change in EMBr strength on the CIFT measurement system and (ii) a real-time solution of the inverse problem. We present solutions of both problems for a model of a continuous caster with a ruler-type EMBr. The EMBr introduces offsets of the measured magnetic field that are several orders of magnitude larger than the very flow-induced perturbations. The offset stems from the ferromagnetic hysteresis exhibited by the ferrous parts of the EMBr in the proximity of the measurement coils. Compensation of the offset was successfully achieved by implementing a numerical model of hysteresis to predict the offset. Real-time reconstruction was achieved by precalculating the computationally heavy matrix inverses for a predefined set of regularization parameters and choosing the optimal one in every measurement frame. Finally, we show that this approach does not hinder the reconstruction quality.
•The impact of a solidified shell on an MHD flow of a liquid metal is significant.•The transformation of a double-roll flow pattern into a single-roll flow takes place.•The non-monotonic behavior of ...the mean velocity magnitude is observed in the jet region.•The flow reversal is observed in the proximity of the meniscus.•Flow oscillations are strongly suppressed.
In the present study, we have performed a series of numerical simulations of the turbulent liquid metal flow in a laboratory-scale setup of the continuous casting. The liquid metal flow was subjected to an external non-uniform magnetic field reproducing a realistic electromagnetic brake (EMBr) effect. The focus of this research was on the effects of the finite electrical conductivity of Hartmann walls on the flow and turbulence in the mold. To be able to simulate distributions of the electric potential and current in both the fluid and solid wall domains, we applied our recently developed and validated in-house conjugate MHD solver based on the open-source code OpenFOAM. The dynamic Large Eddy Simulation (LES) method was used to simulate the turbulent flow. The results obtained for the neutral (non-MHD) and MHD cases over a range of the imposed EMBr strengths – all for the perfectly electrically insulated walls – were compared with the available Ultrasound Doppler Velocimetry (UDV) measurements. A good agreement between simulations and experiments was obtained for all simulated cases. Next, we completed a series of simulations including a wide range of the finite electric conductivities (ranging from a weakly to perfectly conducting wall conditions) of the Hartmann walls for a fixed value of the imposed EMBr. The obtained results demonstrated a significant influence of the electric wall conductivities on the flow and turbulence reorganization. It is expected that here provided insights can be applicable for the new generation of the laboratory- and real-scale continuous casting setups.
U radu se nastoji prikazati odnos Crkve i medija ako se on promatra kao susret evanđelja s kulturom, prije svega onom društvenom i političkom. Budući da je riječ o trajnom pozivu evanđelja, društvena ...i politička kultura koja je nadahnuta evanđeljem jest “kultura odgovornosti”. Ona ne trpi individualizam, teži širiti se i biti uzorom svakoj drugoj kulturi u njezinoj posebnosti. Takva kultura usmjerena je na drugoga i zato je riječ o “kulturi susreta”. Stoga se govor o odnosu Crkve i medija smješta u govor o misijskoj djelatnosti, o područjima misijske djelatnosti, kao i u govor o inkulturaciji. S obzirom na to, rad donosi i koristan prikaz postojećih podataka o stanju s obzirom na Crkvu i medije u Hrvatskoj, koji su izneseni u nekoliko ranijih istraživanja. Oni pokazuju još uvijek nedovoljnu prisutnost Crkve na području medija, iako su pomaci vidljivi. Također, rad donosi i teološko promišljanje o navedenom odnosu te iznosi razloge i poticaje za čvršće zalaganje Crkve, ponajprije mjesne (župe), na području sredstava društvenog priopćavanja.
More than 96% of steel in the world is produced via the method of continuous casting. The flow condition in the mould, where the initial solidification occurs, has a significant impact on the quality ...of steel products. It is important to have timely, and perhaps automated, control of the flow during casting. This work presents a new concept of using contactless inductive flow tomography (CIFT) as a sensor for a novel controller, which alters the strength of an electromagnetic brake (EMBr) of ruler type based on the reconstructed flow structure in the mould. The method was developed for the small-scale Liquid Metal Model for Continuous Casting (mini-LIMMCAST) facility available at the Helmholtz-Zentrum Dresden-Rossendorf. As an example of an undesired flow condition, clogging of the submerged entry nozzle (SEN) was modelled by partly closing one of the side ports of the SEN; in combination with an active EMBr, the jet penetrates deeper into the mould than when the EMBr is switched off. Corresponding flow patterns are detected by extracting the impingement position of the jets at the narrow faces of the mould from the CIFT reconstruction. The controller is designed to detect to undesired flow condition and switch off the EMBr. The temporal resolution of CIFT is 0.5 s.
Članak istražuje složen odnos eshatologije i politike iz aspekta teološkog diskursa radi otkrivanja njihovih dodirnih točaka, a shodno tomu i implikacija koje eshatologija stavlja pred politiku. ...Nakana je članka da predstavi politiku kao interesno područje eshatologije i eshatologiju kao njezin kritički korektiv, te upozoriti na rizike i mogućnosti koje njihov suodnos ima. Uz pojmovna pojašnjenja prvotno se ističe karakteristično starozavjetno iskustvo eshatologiziranja povijesnih događaja, osobito proročko. Novozavjetna se pak eshatologija fokusira na Isusov odnos prema političkom životu. Konačno, problematizira se (ne)mogućnost govora o eshatološkim implikacijama na politiku, osobito kao zahtjev za političkim djelovanjem koje mora njegovati odnos prema prošlosti i pravilno ga ugraditi u budućnost.
The paper researches the complex relation between Eschatology and Politics from the theological point of view by revealing their mutual points, and along with that aims to present the eschatological implications that are being put to Politics. The intention of this paper is to represent the Politics as interest field of Eschatology and also Eschatology as its critical corrective by warning to the risks and possibilities its relationship has to offer.
Aside to notional explanations the paper firstly emphasizes the characteristic Old testament experience from historical events that were interpreted in the eschatological key, especially with the role of the prophets. New testament Eschatology is focused here on Jesus’ relation to political life. Finally, the paper reflects the (im)possibility to speak of the eschatological implications to Politics in some concrete social issues, especially as a notion for political action that must nourish the relation towards past and correctly embed it to the future.
Nozzle clogging contributes heavily to quality issues seen during the process of continuous casting. The presence of clogging in the Submerged Entry Nozzle (SEN) can significantly change the flow ...patterns in the mould and therefore impact the quality of the steel product. Also, there is a high risk of inclusions due to parts of the clogging material breaking off and entering the mould. In this paper, we propose a new sensor setup that allows us to detect clogging in the SEN by monitoring the angle of the exiting jet. Based on this clog detection setup, a switched MPC controller is used to keep the angle of the exiting jet between the optimum ranges using an Electromagnetic Brake. This allows the controller to keep the angle of the jet in the optimum range even when clogging occurs in the nozzle. Experimental data from a laboratory scale continuous caster is used to derive the models for the controller.
Meniscus velocity in continuous casting is critical in determining the quality of the steel. Due to the complex nature of the various interacting phenomena in the process, designing model-based ...controllers can prove to be a challenge. In this paper a NARX neural network model is trained to describe the complex relationship between the applied current to an Electromagnetic Brake (EMBr) and the measured meniscus velocity. The data for the model is obtained using a laboratory scale continuous casting plant. Adaptive Model Predictive Control (MPC) was used to deal with the non-linearity of the model by adapting the prediction model to the different operating conditions. The controller uses the EMBr as an actuator to keep the meniscus velocity within the optimum range, and reject disturbances that occur during the casting process such as changing the casting speed.
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