2,193 research outputs found
Combustion property analyses with variable liquid marine fuels in combustion research unit
The quality of ignition and co mbustion of four marine and power plant fuels were studied in a Combustion Research Unit, CRU. The fuels were low - sulphur Light Fuel Oil (LFO, baseline), Marine Gas Oil (MGO), kerosene and renewable wood - based naphtha. To meet climate change requirements a nd sustainability goals, combustion systems needs to be able to operate with a variety of renewable and ‘net - zero - carbon’ fuels. Due to the variations in the chemical and physical properties of the fuels, they generally cannot simply be dropped into existi ng systems. The aim of this research project was to understand how changes in fuel composition affect engine operation. The focus was on how various properties of the fuels impact on the combustion process – especially ignition delay and in - cylinder combus tion. The goal of the research project was to allow broad fuel flexibility without any or only minor changes to engine hardware. Before the engine tests, the CRU forms an easy and cost - effective device to find out the engine suitability of the fuel . The re sults showed that the ignition delay decreased expectedly with all fuels when the in - cylinder pressure and temperature increased. The differences in the maximum heat release rates between fuels decreased in high - pressure conditions. MGO had the shortest ig nition delay under both pressure and temperature conditions. Based on the CRU results MGO and kerosene are suitable to use in compression - ignited engines like the reference fuel LFO. In contrast renewable naphtha had a long ignition delay. If naphtha is us ed in a CI engine, the engine must be started and stopped with, e.g. LFO or MGO.fi=vertaisarvioitu|en=peerReviewed
The productivity and financial impacts of eight types of environmental enrichment for broiler chickens
Reduced mobility in broilers can contribute to leg health problems. Environmental enrichment has been suggested as one approach to combat this through stimulating increased physical activity. Past studies have tested the effect of environmental enrichments on bird behaviour, health and welfare, but few have estimated their financial impacts. This study tested the impact of eight types of environmental enrichment on enterprise net margin, accounting for direct intervention costs plus indirect effects via changes to bird mortality, weight, feed intake, feed conversion ratio, and foot pad dermatitis. The trial used 58 pens each containing approximately 500 broilers (Ross 308) at a stocking density of 40 kg/m2. The environmental enrichments were: roughage, vertical panels, straw bales, elevated platforms (5 and 30 cm), increased distances between feed and water (7 and 3.5 m) and stocking density reduced to 34 kg/m2, plus a control group. Mortality was recorded daily and feed intake and weight weekly. Footpad dermatitis was assessed on day 35. Only one intervention improved financial performance (3.5 m between feed and water) above the control, suggesting that most environmental enrichment would have a negative financial impact due to the additional intervention costs, unless consumers were willing to pay a price premium
Abelian and Non-Abelian Induced Parity Breaking Terms at Finite Temperature
We compute the exact canonically induced parity breaking part of the
effective action for 2+1 massive fermions in particular Abelian and non Abelian
gauge field backgrounds. The method of computation resorts to the chiral
anomaly of the dimensionally reduced theory.Comment: 13 pages, RevTeX, no figure
Dynamical Symmetry Breaking in Planar QED
We investigate (2+1)-dimensional QED coupled with Dirac fermions both at zero
and finite temperature. We discuss in details two-components (P-odd) and
four-components (P-even) fermion fields. We focus on P-odd and P-even Dirac
fermions in presence of an external constant magnetic field. In the spontaneous
generation of the magnetic condensate survives even at infinite temperature. We
also discuss the spontaneous generation of fermion mass in presence of an
external magnetic field.Comment: 34 pages, 8 postscript figures, final version to appear on J. Phys.
Shape of the hot topological charge density spectral function
After motivating an interest in the shape of the topological charge density spectral function in hot Yang-Mills theories, we estimate it with the help of thermally averaged classical real-time simulations, for N-c = 2, 3. After subtracting a perturbative contribution at large frequencies, we observe a non-trivial shape at small frequencies (a dip rather than a peak), interpolating smoothly towards the sphaleron rate at zero frequency. Possible frequency scales making an appearance in this shape are discussed. Implications for warm axion inflation and reheating, and for imaginary-time lattice measurements of the strong sphaleron rate, are recapitulated.Peer reviewe
Fixed Charge Ensembles and Parity Breaking Terms
Recently derived results for the exact induced parity-breaking term in 2+1
dimensions at finite temperature are shown to be relevant to the determination
of the free energy for fixed-charge ensembles. The partition functions for
fixed total charge corresponding to massive fermions in the presence of Abelian
and non-Abelian magnetic fields are discussed. We show that the presence of the
induced Chern-Simons term manifests itself in that the free energy depends
strongly on the relation between the external magnetic flux and the value of
the fixed charge.Comment: 10 pages, Revte
Energetic electron avalanches and mode transitions in planar inductively coupled radio-frequency driven plasmas operated in oxygen
Twisted Vortices in a Gauge Field Theory
We inspect a particular gauge field theory model that describes the
properties of a variety of physical systems, including a charge neutral
two-component plasma, a Gross-Pitaevskii functional of two charged Cooper pair
condensates, and a limiting case of the bosonic sector in the Salam-Weinberg
model. It has been argued that this field theory model also admits stable
knot-like solitons. Here we produce numerical evidence in support for the
existence of these solitons, by considering stable axis-symmetric solutions
that can be thought of as straight twisted vortex lines clamped at the two
ends. We compute the energy of these solutions as a function of the amount of
twist per unit length. The result can be described in terms of a energy
spectral function. We find that this spectral function acquires a minimum which
corresponds to a nontrivial twist per unit length, strongly suggesting that the
model indeed supports stable toroidal solitons.Comment: 10 pages, 5 figures, title changed, minor revisions, and more
references adde
Methanol-HVO blends for efficient low-temperature combustion: analytical research on fuel properties
Received: January 31st, 2023 ; Accepted: April 15th, 2023 ; Published: August 14th, 2023 ; Correspondence: [email protected] low-temperature combustion (LTC) engines can accommodate
ultra-high efficiency with near-zero NOx and PM emissions. Reaction kinetics is the governing
mechanism in LTC. Onboard fuel reactivity control is, thus, becoming an interesting concept that
ultimately provides pathways toward a fully fuel-flexible engine. No matter the technical
realisation - in-cylinder blending or pre-blending/emulsification - the reactivity control requires
fuels with complementary properties. Methanol and hydrotreated vegetable oil (HVO) seem to
be one of the most promising, yet under-studied combination for LTC engines. They are both
renewable and can be mixed together. Methanol’s high knock resistance and large latent heat of
evaporation enable a wide engine load range, with a propensity to reduce NOx emissions and
mitigate thermal or mechanical stress. The same properties on the other hand require highly
reactive fuel to enable the mixture to self-ignite controllably in LTC conditions. HVO is amongst
the most reactive renewable alternatives and its clean paraffinic structure further mitigates
particle matter formation. - Importantly, in pre-blending HVO emulsification can resolve the
lubricity issues of methanol. In this paper, the aim was to study the engine-relevant properties of
HVO-methanol fuel blends. The analysed properties were the distillation properties, density,
kinematic viscosity, cetane index, and flash point. Based on the results, the suitability of the
chosen blend shares for LTC concepts was evaluated
Asymptotically Free Yang-Mills Classical Mechanics with Self-Linked Orbits
We construct a classical mechanics Hamiltonian which exhibits spontaneous
symmetry breaking akin the Coleman-Weinberg mechanism, dimensional
transmutation, and asymptotically free self-similarity congruent with the
beta-function of four dimensional Yang-Mills theory. Its classical equations of
motion support stable periodic orbits and in a three dimensional projection
these orbits are self-linked into topologically nontrivial, toroidal knots.Comment: 9 pages incl. 5 fig
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