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Implementation of the Semi Empirical Kinetic Soot Model within Chemistry Tabulation Framework for Efficient Emissions Predictions in Diesel Engines
Soot prediction for diesel engines is a very important aspect of internal combustion engine emissions research, especially nowadays with very strict emission norms. Computational Fluid Dynamics (CFD) is often used in this research and optimisation of CFD models in terms of a trade-off between accuracy and computational efficiency is essential. This is especially true in the industrial environment where good predictivity is necessary for engine optimisation, but computational power is limited. To investigate soot emissions for Diesel engines, in this work CFD is coupled with chemistry tabulation framework and semi-empirical soot model. The Flamelet Generated Manifold (FGM) combustion model precomputes chemistry using detailed calculations of the 0D homogeneous reactor and then stores the species mass fractions in the table, based on six look-up variables: pressure, temperature, mixture fraction, mixture fraction variance, progress variable and progress variable variance. Data is then retrieved during online CFD simulation, enabling fast execution times while keeping the accuracy of the direct chemistry calculation. In this work, the theory behind the model is discussed as well as implementation in commercial CFD code. Also, soot modelling in the framework of tabulated chemistry is investigated: mathematical model and implementation of the kinetic soot model on the tabulation side is described, and 0D simulation results are used for verification. Then, the model is validated using real-life engine geometry under different operating conditions, where better agreement with experimental measurements is achieved, compared to the standard implementation of the kinetic soot model on the CFD side
Première mention du Marssonina salicicola sur des saules pleureurs au Québec
Au cours des printemps 1996 et 1997, des prélèvements ont été réalisés sur cinq sites à Montréal (Québec) pour établir l'étiologie de l'anthracnose des saules pleureurs (Salix alba Tristis' et S. babylonica). Sur les 25 arbres examinés, 21 étaient affectés par une maladie fongique due au Marssonina salicicola qui constitue le stade conidien du Drepanopeziza sphaeroides. Cette détection est la première mention de la présence du champignon au Canada, à l’est des Rocheuses.During spring 1996 and 1997, five sites on the Island of Montreal, Quebec, were examined to study the occurrence of anthracnose on weeping willows (Salix alba Tristis' and S. babylonica). On 21 trees of 25 surveyed, the pathogenic fungus Marssonina salicicola, the conidial state of Drepanopeziza sphaeroides, was found. This report is the first mention of the presence of this fungus in Canada, east of the Rocky Mountains
The in vivo effect of hepatotrophic factors ALR, HGF, and IGF-II on natural killer cell functions
Properties of the phi meson at high temperatures and densities
We calculate the spectral density of the phi meson in a hot bath of nucleons
and pions using a general formalism relating self-energy to the forward
scattering amplitude (FSA). In order to describe the low energy FSA, we use
experimental data along with a background term. For the high energy FSA, a
Regge parameterization is employed. We verify the resulting FSA using
dispersion techniques. We find that the position of the peak of the spectral
density is slightly shifted from its vacuum position and that its width is
considerably increased. The width of the spectral density at a temperature of
150 MeV and at normal nuclear density is more than 90 MeV.Comment: 4 pages, 5 figures, Poster presented at Quark Matter 200
CFD modelling of a spark ignition internal combustion engine fuelled with syngas for a mCHP system
Micro Combined Heat and Power (mCHP) powered with biomass is nowadays a technology attracting increasing interest to develop a local supply chain to produce, process and valorise the available material in territorial areas as much as possible circumscribed, with a considerable reduction also of the CO2 related to transportation. Application for biomass powered mCHP produces environmental benefits by reducing primary energy consumption and associated greenhouse gas emissions and complies with the need for increased decentralization of energy supply. Of particular relevance is mCHP based on biomass gasification due to the negligible particulate matter release with respect to combustion. The present work describes a 3D CFD model of the spark ignition (SI) internal combustion engine (ICE) fuelled with syngas installed in the mCHP pilot system ECO20 manufactured by the Italian company Costruzioni Motori Diesel S.p.A. (CMD). The considered system is made of a gasifier combined with proper syngas cleaning devices, an ICE and a generator to deliver a maximum electrical and thermal power of 20 kW and 40 kW, respectively. For the proper initialisation of the 3D CFD model, the syngas composition is experimentally characterised using a gas-chromatograph on samples collected under real operation. The calculated pressure cycle is verified by comparison with the one calculated through a properly developed 1D ICE model. Main goals of the performed numerical analysis are to study into detail the combustion process and to assess the engine performance characteristics related to the use of syngas
Is it possible to formulate least action principle for dissipative systems?
A longstanding open question in classical mechanics is to formulate the least
action principle for dissipative systems. In this work, we give a general
formulation of this principle by considering a whole conservative system
including the damped moving body and its environment receiving the dissipated
energy. This composite system has the conservative Hamiltonian
where is the kinetic energy of the moving body, its potential
energy and the energy of the environment. The Lagrangian can be derived
by using the usual Legendre transformation where is the
total kinetic energy of the environment. An equivalent expression of this
Lagrangian is where is the energy dissipated by the
friction from the moving body into the environment from the beginning of the
motion. The usual variation calculus of least action leads to the correct
equation of the damped motion. We also show that this general formulation is a
natural consequence of the virtual work principle.Comment: 11 pages, no figur
Phi meson production in In-In collisions at =158 GeV: evidence for relics of a thermal phase
Yields and transverse mass distributions of the -mesons reconstructed
in the channel in In+In collisions at =158
GeV are calculated within an integrated Boltzmann+hydrodynamics hybrid approach
based on the Ultrarelativistic Quantum Molecular Dynamics (UrQMD) transport
model with an intermediate hydrodynamic stage. The analysis is performed for
various centralities and a comparison with the corresponding NA60 data in the
muon channel is presented. We find that the hybrid model, that embeds an
intermediate locally equilibrated phase subsequently mapped into the transport
dynamics according to thermal phase-space distributions, gives a good
description of the experimental data, both in yield and slope. On the contrary,
the pure transport model calculations tend to fail in catching the general
properties of the meson production: not only the yield, but also the
slope of the spectra, very poorly compare with the experimental
observations
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