2,433 research outputs found
Study of advanced electric propulsion system concept using a flywheel for electric vehicles
Advanced electric propulsion system concepts with flywheels for electric vehicles are evaluated and it is predicted that advanced systems can provide considerable performance improvement over existing electric propulsion systems with little or no cost penalty. Using components specifically designed for an integrated electric propulsion system avoids the compromises that frequently lead to a loss of efficiency and to inefficient utilization of space and weight. A propulsion system using a flywheel power energy storage device can provide excellent acceleration under adverse conditions of battery degradation due either to very low temperatures or high degrees of discharge. Both electrical and mechanical means of transfer of energy to and from the flywheel appear attractive; however, development work is required to establish the safe limits of speed and energy storage for advanced flywheel designs and to achieve the optimum efficiency of energy transfer. Brushless traction motor designs using either electronic commutation schemes or dc-to-ac inverters appear to provide a practical approach to a mass producible motor, with excellent efficiency and light weight. No comparisons were made with advanced system concepts which do not incorporate a flywheel
Thermomechanical Behavior of the HL-LHC 11 Tesla Nb3Sn Magnet Coil Constituents during Reaction Heat Treatment
The knowledge of the temperature induced changes of the superconductor
volume, and of the thermo-mechanical behaviour of the different coil and
tooling materials is required for predicting the coil geometry and the stress
distribution in the coil after the Nb3Sn reaction heat treatment. In the
present study we have measured the Young's and shear moduli of the HL-LHC 11 T
Nb3Sn dipole magnet coil and reaction tool constituents during in situ heat
cycles with the dynamic resonance method. The thermal expansion behaviours of
the coil components and of a free standing Nb3Sn wire were compared based on
dilation experiments.Comment: 6 pages, 12 figures, presented at MT25 conferenc
Magnetic flux pumping in 3D nonlinear magnetohydrodynamic simulations
A self-regulating magnetic flux pumping mechanism in tokamaks that maintains
the core safety factor at , thus preventing sawteeth, is analyzed
in nonlinear 3D magnetohydrodynamic simulations using the M3D-C code. In
these simulations, the most important mechanism responsible for the flux
pumping is that a saturated quasi-interchange instability generates
an effective negative loop voltage in the plasma center via a dynamo effect. It
is shown that sawtoothing is prevented in the simulations if is
sufficiently high to provide the necessary drive for the
instability that generates the dynamo loop voltage. The necessary amount of
dynamo loop voltage is determined by the tendency of the current density
profile to centrally peak which, in our simulations, is controlled by the
peakedness of the applied heat source profile.Comment: submitted to Physics of Plasmas (23 pages, 15 Figures
Nb3Sn wire shape and cross sectional area inhomogeneity in Rutherford cables
During Rutherford cable production the wires are plastically deformed and
their initially round shape is distorted. Using X-ray absorption tomography we
have determined the 3D shape of an unreacted Nb3Sn 11 T dipole Rutherford
cable, and of a reacted and impregnated Nb3Sn cable double stack.
State-of-the-art image processing was applied to correct for tomographic
artefacts caused by the large cable aspect ratio, for the segmentation of the
individual wires and subelement bundles inside the wires, and for the
calculation of the wire cross sectional area and shape variations. The 11 T
dipole cable cross section oscillates by 2% with a frequency of 1.24 mm (1/80
of the transposition pitch length of the 40 wire cable). A comparatively
stronger cross sectional area variation is observed in the individual wires at
the thin edge of the keystoned cable where the wire aspect ratio is largest.Comment: 6 pages, 11 figures, presented at EUCAS 201
A New Method for Searching for Free Fractional Charge Particles in Bulk Matter
We present a new experimental method for searching for free fractional charge
in bulk matter; this new method derives from the traditional Millikan liquid
drop method, but allows the use of much larger drops, 20 to 100 mm in diameter,
compared to the traditional method that uses drops less than 15 mm in diameter.
These larger drops provide the substantial advantage that it is then much
easier to consistently generate drops containing liquid suspensions of powdered
meteorites and other special minerals. These materials are of great importance
in bulk searches for fractional charge particles that may have been produced in
the early universe.Comment: 17 pages, 5 figures in a singl PDF file (created from WORD Doc.).
Submitted to Review of Scientific Instrument
Non-linear Simulations of MHD Instabilities in Tokamaks Including Eddy Current Effects and Perspectives for the Extension to Halo Currents
The dynamics of large scale plasma instabilities can strongly be influenced
by the mutual interaction with currents flowing in conducting vessel
structures. Especially eddy currents caused by time-varying magnetic
perturbations and halo currents flowing directly from the plasma into the walls
are important. The relevance of a resistive wall model is directly evident for
Resistive Wall Modes (RWMs) or Vertical Displacement Events (VDEs). However,
also the linear and non-linear properties of most other large-scale
instabilities may be influenced significantly by the interaction with currents
in conducting structures near the plasma. The understanding of halo currents
arising during disruptions and VDEs, which are a serious concern for ITER as
they may lead to strong asymmetric forces on vessel structures, could also
benefit strongly from these non-linear modeling capabilities. Modeling the
plasma dynamics and its interaction with wall currents requires solving the
magneto-hydrodynamic (MHD) equations in realistic toroidal X-point geometry
consistently coupled with a model for the vacuum region and the resistive
conducting structures. With this in mind, the non-linear finite element MHD
code JOREK has been coupled with the resistive wall code STARWALL, which allows
to include the effects of eddy currents in 3D conducting structures in
non-linear MHD simulations. This article summarizes the capabilities of the
coupled JOREK-STARWALL system and presents benchmark results as well as first
applications to non-linear simulations of RWMs, VDEs, disruptions triggered by
massive gas injection, and Quiescent H-Mode. As an outlook, the perspectives
for extending the model to halo currents are described.Comment: Proceeding paper for Theory of Fusion Plasmas (Joint Varenna-Lausanne
International Workshop), Varenna, Italy (September 1-5, 2014); accepted for
publication in: to Journal of Physics: Conference Serie
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