A low cost air hybrid concept

This article is a pre-print version of the full and final article which is available at the link below.Copyright © 2010 Institut français du pétrole Permission to make digital or hard copies of part or all of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than IFP must be honored. Abstracting with credit is permitted. To copy otherwise, to republish, to post on servers, or to redistribute to lists, requires prior specific permission and/or a fee: Request permission from Documentation, Institut français du pétrole, fax. +33 1 47 52 70 78, or [email protected] air hybrid engine absorbs the vehicle kinetic energy during braking, stores it in an air tank in the form of compressed air, and reuses it to propel a vehicle during cruising and acceleration. Capturing, storing and reusing this braking energy to give additional power can therefore improve fuel economy, particularly in cities and urban areas where the traffic conditions involve many stops and starts. In order to reuse the residual kinetic energy, the vehicle operation consists of 3 basic modes, i.e. Compression Mode (CM), Expander Mode (EM) and normal firing mode. Unlike previous works, a low cost air hybrid engine has been proposed and studied. The hybrid engine operation can be realised by means of production technologies, such as VVT and valve deactivation. In this work, systematic investigation has been carried out on the performance of the hybrid engine concept through detailed gas dynamic modelling using Ricardo WAVE software. Valve timing optimization has been done for the more efficient operation of air hybrid operation and obtaining higher braking and Motoring mean effective pressure for CM and EM respectively.EPSR

NLTE study of scandium in the Sun

We investigate the formation of neutral and singly ionized scandium lines in the solar photospheres. The research is aimed derive solar $\log gf\epsilon_{\odot}$(Sc) values for scandium lines, which will later be used in differential abundance analyses of metal-poor stars. Extensive statistical equilibrium calculations were carried out for a model atom, which comprises 92 terms for \ion{Sc}{i} and 79 for \ion{Sc}{ii}. Photoionization cross-sections are assumed to be hydrogenic. Synthetic line profiles calculated from the level populations according to the NLTE departure coefficients were compared with the observed solar spectral atlas. Hyperfine structure (HFS) broadening is taken into account. The statistical equilibrium of scandium is dominated by a strong underpopulation of \ion{Sc}{i} caused by missing strong lines. It is nearly unaffected by the variation in interaction parameters and only marginally sensitive to the choice of the solar atmospheric model. Abundance determinations using the ODF model lead to a solar Sc abundance of between $\log\epsilon_\odot = 3.07$ and 3.13, depending on the choice of $f$ values. The long known difference between photospheric and meteoritic scandium abundances is confirmed for the experimental $f$-values.Comment: 10 pages, 6 figures, A&A accepte

Characteristics of homogeneous charge compression ignition (HCCI) combustion and emissions of n-heptane

This paper reports the outcome from a systematic investigation carried out on HCCI (Homogeneous Charge Compression Ignition) combustion of a diesel type fuel. The n heptane was chosen in this study to study the premixed diesel HCCI combustion characteristics with port fuel injection. Measurements were carried out in a single-cylinder, 4-stroke and variable compression ratio engine. Premixed n-heptane/air/EGR mixture was introduced into the cylinder by a port fuel injector and an external EGR system. The operating regions with regard to Air/Fuel ratio and EGR rate were established for different compression ratios and intake temperatures. The effects of compression ratios, intake temperatures, Air/Fuel ratios and EGR rates on knock limit, auto-ignition timing, combustion rate, IMEP, and engine-out emissions, such as NOx, CO, and unburned HC, were analysed. The results have shown HCCI combustion of n-heptane could be implemented without intake charge heating with a typical diesel engine compression ratio. The attainable HCCI operating region was mainly limited by the knock limit, misfir, and low IMEP respectively. Higher intake temperature or compression ratio could extend the misfire limit of the HCCI operation at low load but they would reduce the maximum IMEP limit at higher load conditions. Compared with conventional diesel combustion, HCCI combustion lead to extremely low NOx emissions ( less than 5 ppm) and smoke free exhaust. But HCCI diesel combustion was found to produce higher HC and CO emissions. An increase in intake temperature or compression ratio helped to reduce HC and CO emissions.

Self-consistent models of triaxial galaxies in MOND gravity

The Bekenstein-Milgrom gravity theory with a modified Poisson equation is tested here for the existence of triaxial equilibrium solutions. Using the non-negative least square method, we show that self-consistent triaxial galaxies exist for baryonic models with a mild density cusp $\rho \sim {\Sigma \over r}$. Self-consistency is achieved for a wide range of central concentrations, $\Sigma \sim 10-1000\mathrm{M_{\odot}pc^{-2}}$, representing low-to-high surface brightness galaxies. Our results demonstrate for the first time that the orbit superposition technique is fruitful for constructing galaxy models beyond Newtonian gravity, and triaxial cuspy galaxies might exist without the help of Cold dark Matter.Comment: 19 pages, 1 table, 7 figures, Accepted for publication in Ap

Anomalous Hall effect in non-collinear antiferromagnetic antiperovskite Mn3_{3}Ni1−x_{1-x}Cux_{x}N

We report the anomalous Hall effect (AHE) in antiperovskite Mn$_{3}$NiN with substantial doping of Cu on the Ni site (i.e. Mn$_{3}$Ni$_{1-x}$Cu$_{x}$N), which stabilizes a noncollinear antiferromagnetic (AFM) order compatible with the AHE. Observed on both sintered polycrystalline pieces and single crystalline films, the AHE does not scale with the net magnetization, contrary to the conventional ferromagnetic case. The existence of the AHE is explained through symmetry analysis based on the $\Gamma_{\rm 4g}$ AFM order in Cu doped Mn$_{3}$NiN. DFT calculations of the intrinsic contribution to the AHE reveal the non-vanishing Berry curvature in momentum space due to the noncollinear magnetic order. Combined with other attractive properties, antiperovskite Mn$_{3}$AN system offers great potential in AFM spintronics.Comment: Supplemental Materials not include