Detailed chemical mechanism of the phase transition in nano-SrTiO3 perovskite with visible luminescence

Autoignition in SI engines is an abnormal combustion mode and may lead to engine knock in SI engines. Knock may cause damage and it is a source of noise in engines. It limits the compression ratio of the engine and a low compression ratio means low fuel conversion efficiency of the engine. In this paper a multi zone model based on an existing two zone model Hajireza et al., [1 and 12] and Stenla˚a˚s et al., [30] is developed and validated against the experimental results. The validation is done by using the same detailed chemical mechanism consisting of 141 species and about 1405 reactions under the same conditions. The model is a zero dimensional model capable of simulating a full engine cycle. The two zone combustion model consists of a burned and an unburned zone, separated by a thin adiabatic flame front. The multi zone model differs in the handling of the burned gas. In the multi zone case a number of burned zones are present. The number of zones is decided by the temperature difference between the flame front and the last generated burned zone. The detailed chemical mechanism is taken into account in each zone, while the propagating flame front is calculated from the Wiebe function. Each zone is assumed to be a homogeneous mixture with a uniform temperature, mole and mass fractions of species. The spatial variation of the pressure is neglected, i.e., it is assumed to be the same in the whole combustion chamber at every instant of time. Autoignition is handled by the chemical kinetic model. As the unburned zone is assumed homogeneous the effect of auto ignition is a single pressure peak. The model is not designed to predict the pressure oscillations seen in engine knock.

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Simulating the detailed chemical composition of secondary organic aerosol formed on a regional scale during the TORCH 2003 campaign in the southern UK

Atmospheric Chemistry and Physics ◽

10.5194/acp-6-419-2006 ◽

2006 ◽

Vol 6 (2) ◽

pp. 419-431 ◽

Cited By ~ 63

Author(s):

D. Johnson ◽

S. R. Utembe ◽

M. E. Jenkin

Keyword(s):

Chemical Composition ◽

Secondary Organic Aerosol ◽

Regional Scale ◽

Equilibrium Phase ◽

Organic Aerosol ◽

Oxidation Products ◽

Chemical Mechanism ◽

Phase Partitioning ◽

Biogenic Voc ◽

Detailed Chemical

Abstract. Following on from the companion study (Johnson et al., 2006), a photochemical trajectory model (PTM) has been used to simulate the chemical composition of organic aerosol for selected events during the 2003 TORCH (Tropospheric Organic Chemistry Experiment) field campaign. The PTM incorporates the speciated emissions of 124 non-methane anthropogenic volatile organic compounds (VOC) and three representative biogenic VOC, a highly-detailed representation of the atmospheric degradation of these VOC, the emission of primary organic aerosol (POA) material and the formation of secondary organic aerosol (SOA) material. SOA formation was represented by the transfer of semi- and non-volatile oxidation products from the gas-phase to a condensed organic aerosol-phase, according to estimated thermodynamic equilibrium phase-partitioning characteristics for around 2000 reaction products. After significantly scaling all phase-partitioning coefficients, and assuming a persistent background organic aerosol (both required in order to match the observed organic aerosol loadings), the detailed chemical composition of the simulated SOA has been investigated in terms of intermediate oxygenated species in the Master Chemical Mechanism, version 3.1 (MCM v3.1). For the various case studies considered, 90% of the simulated SOA mass comprises between ca. 70 and 100 multifunctional oxygenated species derived, in varying amounts, from the photooxidation of VOC of anthropogenic and biogenic origin. The anthropogenic contribution is dominated by aromatic hydrocarbons and the biogenic contribution by α- and β-pinene (which also constitute surrogates for other emitted monoterpene species). Sensitivity in the simulated mass of SOA to changes in the emission rates of anthropogenic and biogenic VOC has also been investigated for 11 case study events, and the results have been compared to the detailed chemical composition data. The role of accretion chemistry in SOA formation, and its implications for the results of the present investigation, is discussed.

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The structure of P21/c (Ca0.2Co0.8)CoSi2O6 pyroxene and the C2/c–P21/c phase transition in natural and synthetic Ca–Mg–Fe2+ pyroxenes

Mineralogical Magazine ◽

10.1180/minmag.2017.081.036 ◽

2018 ◽

Vol 82 (1) ◽

pp. 211-228 ◽

Cited By ~ 3

Author(s):

Mario Tribaudino ◽

Luciana Mantovani ◽

Francesco Mezzadri ◽

Gianluca Calestani ◽

Geoffrey Bromiley

Keyword(s):

Phase Transition ◽

High Pressure ◽

Ionic Radius ◽

Structural Changes ◽

Local Level ◽

Chemical Mechanism ◽

Slow Cooling ◽

Cation Radius ◽

The Difference ◽

Natural And Synthetic

ABSTRACTA P21/c synthetic (Ca0.2Co0.8)CoSi2O6 pyroxene was synthesized by slow cooling from melt at high pressure. Single crystals suitable for X-ray diffraction were obtained and refined. The results were compared to those of C2/c pyroxenes along the series CaCoSi2O6–Co2Si2O6. Strong similarities in the crystal chemical mechanism of the transition with the synthetic CaFeSi2O6–Fe2Si2O6 and CaMgSi2O6–Mg2Si2O6 pyroxenes, both at an average and local level are apparent.The results, examined together with two new refinements of pigeonite in the ureilites ALHA77257 and RKPA80239 and with a set of natural and synthetic C2/c and P21/c pyroxenes, show that the average cation radius in the M2 site is the driving force for the phase transition from C2/c to P21/c. The longest M2–O3 distances and the O3–O3–O3 angles follow the same trend, dictated only by the ionic radius in M2, in either synthetic or natural pyroxenes, regardless of the ionic radius of the M1 cations. The transition also affects the difference between bridging and non-bridging oxygen atoms and the extent of tetrahedral deformation, whereas the M1–O, M2–O1 and M2–O2 distances are unaffected by the transition and are determined only by the ionic radius of the bonding cation. The structural changes between the ionic radius and the high temperature C2/c and P21/c transitions are similar, and different to the high-pressure transition.Analysis of natural and synthetic pyroxenes shows that the transition with composition occurs in strain free pyroxenes for a critical radius of 0.85 Å. Increasing strain stabilizes the P21/c structure to a higher temperature and larger cation radius.Finally, our results show that the monoclinic P21/c Ca-poor clinopyroxene, i.e the mineral pigeonite, crystallizes only at conditions where the structure is HT-C2/c, and changes to the P21/c symmetry during cooling.

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Reduction of a detailed chemical mechanism for a kerosene surrogate via RCCE-CSP

Combustion and Flame ◽

10.1016/j.combustflame.2018.04.004 ◽

2018 ◽

Vol 194 ◽

pp. 85-106 ◽

Cited By ~ 14

Author(s):

Panos Koniavitis ◽

Stelios Rigopoulos ◽

W.P. Jones

Keyword(s):

Chemical Mechanism ◽

Detailed Chemical

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Simulating the detailed chemical composition of secondary organic aerosol formed on a regional scale during the TORCH 2003 campaign in the southern UK

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-5-7875-2005 ◽

2005 ◽

Vol 5 (4) ◽

pp. 7875-7902

Author(s):

D. Johnson ◽

S. R. Utembe ◽

M. E. Jenkin

Keyword(s):

Chemical Composition ◽

Secondary Organic Aerosol ◽

Regional Scale ◽

Equilibrium Phase ◽

Organic Aerosol ◽

Oxidation Products ◽

Chemical Mechanism ◽

Phase Partitioning ◽

Biogenic Voc ◽

Detailed Chemical

Abstract. Following on from the companion study (Johnson et al., 2005a), a photochemical trajectory model (PTM) has been used to simulate the chemical composition of organic aerosol for selected events during the 2003 TORCH (Tropospheric Organic Chemistry Experiment) field campaign. The PTM incorporates the speciated emissions of 124 non-methane anthropogenic volatile organic compounds (VOC) and three representative biogenic VOC, a highly-detailed representation of the atmospheric degradation of these VOC, the emission of primary organic aerosol (POA) material and the formation of secondary organic aerosol (SOA) material. SOA formation was represented by the transfer of semi- and non-volatile oxidation products from the gas-phase to a condensed organic aerosol-phase, according to estimated thermodynamic equilibrium phase-partitioning characteristics for around 2000 reaction products. After significantly scaling all phase-partitioning coefficients, and assuming a persistent background organic aerosol (both required in order to match the observed organic aerosol loadings), the detailed chemical composition of the simulated SOA has been investigated in terms of intermediate oxygenated species in the Master Chemical Mechanism, version 3.1 (MCM v3.1). For the various case studies considered, 90% of the simulated SOA mass comprises between ca. 70 and 100 multifunctional oxygenated species derived, in varying amounts, from the photooxidation of VOC of anthropogenic and biogenic origin. The anthropogenic contribution is dominated by aromatic hydrocarbons and the biogenic contribution by α- and β-pinene (which also constitute surrogates for other emitted monoterpene species). Sensitivity in the simulated mass of SOA to changes in the emission rates of anthropogenic and biogenic VOC has also been investigated for 11 case study events, and the results have been compared to the detailed chemical composition data. The role of accretion chemistry in SOA formation, and its implications for the results of the present investigation, is discussed.

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