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2 2017

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Vacuum Shroud (VS) for production of clean steel in tundish

Chatterjee D.

Journal of Achievements in Materials and Manufacturing Engineering

2017

Vol. 81, nr 1

18--34

Purpose: Ladle to tundish melt transfer is paramount importance over the last three decades to controlling the cleanliness of high value steel. Tundish is an important buffer between ladle and mould where inclusion separation, flotation can be enhanced and exposed slag eye formation can be hindered by applying the knowledge of fluid dynamics as well heat transfer by changing the design of conventional flow modifiers towards production of ultra clean steel. Design/methodology/approach: In current numerical investigation a new conceptual flow control device called ‘vacuum shroud (VS)’ has been proposed to reduce slag eye formation, emulsifications and unwanted inclusions generations. Due to upward suction force from the side of the pouring nozzle the device is quite capable to reduce turbulence and emulsification within the tundish melt. Findings: Approximately 76% improvement in the overall process and 40% enhancement to inclusion floatability are predictable by using current flow control device (FCD). Research limitations/implications: Slag eye formation during pouring of liquid steel to tundish is a barrier to clean steel production on sustained manner. Several efforts have been made over the decades to resolve this phenomenon by suppressing the turbulence within this reactor incorporating many innovative flow control refractory’s like turbo-stop, trumpet shroud, advance pouring box, dissipative shroud, velocity break shroud, swirling flow shroud etc. But ultimate success is not possible to reach. Originality/value: The present investigation is development of an innovative flow control device (FCD) to control the aforementioned problems within this metallurgical reactor.

Analysis of disturbing effect of 3 kV DC supplied traction vehicles equipped with two-level and three-level VSI on railway signalling track circuits

Steczek M., Szeląg A., Chatterjee D.

Bulletin of the Polish Academy of Sciences. Technical Sciences

2017

Vol. 65, nr 5

663--674

Electric traction vehicles cooperating with a 3kV DC traction system and equipped with drive systems based on voltage source inverters are the most significant sources of disturbances for a railway signalling system. Every traction vehicle to be authorised for operation on railway lines must fulfil the limits imposed on current harmonics magnitudes and those provided by railway operators. The solution introduced for prototypes of most modern traction drives is to replace the two-level inverters with three-level topology. Therefore, it is essential to establish the influence of the new solution on the railway signalling system. This paper presents a comparative analysis between simulation results delivered for two and three-level traction drive system regarding generation of disturbing current harmonics. Two types of VSI modulation techniques were taken under consideration: sinusoidal PWM (SPWM) and a new one, proposed by the authors, based on selective harmonic elimination (SHE). Furthermore, the authors presented application of one of the SHE based optimization techniques for shaping the EMU’s (electric multiple unit) DC side input current harmonics spectrum in order to meet the required limits. The described technique is based on off-line generation of a set of solutions for each of the VSI operating points and selection of the best solution for the assumed criteria. The applied simulation models and the concept of SHE control were verified in a laboratory by means of a low-power drive stand. Using the three-level inverter in traction drives system results in less current harmonics than using two-level topology without modification of the modulation technique. Thus, it does not guarantee fulfilling all limits assumed in this paper. The proposed modulation technique allows for fulfilling the limits, and the technical implementation of the proposed technique in a traction drive system will be considered in future studies.