Liquid vaporization under thermodynamic phase non-equilibrium condition at the gas-liquid interface is investigated over a wide range of fluid state typical of many liquid-fueled energy conversion systems. The validit...Liquid vaporization under thermodynamic phase non-equilibrium condition at the gas-liquid interface is investigated over a wide range of fluid state typical of many liquid-fueled energy conversion systems. The validity of the phase-equilibrium assumption commonly used in the existing study of liquid vaporization is examined using molecular dynamics theories. The interfacial mass flow rates on both sides of the liquid surface are compared to the net vaporization rate through an order-of-magnitude analysis.Results indicated that the phase-equilibrium assumption holds valid at relatively high pressures and low temperatures,and for droplets with relatively large initial diameters(for example,larger than 10 μm for vaporizing oxygen droplets in gaseous hydrogen in the pressure range from 10 atm to the oxygen critical state). Droplet vaporization under superheated conditions is also explored using classical binary homogeneous nucleation theory,in conjunction with a real-fluid equation of state. It is found that the bubble nucleation rate is very sensitive to changes in saturation ratio and pressure;it increases by several orders of magnitude when either the saturation ratio or the pressure is slightly increased. The kinetic limit of saturation ratio decreases with increasing pressure,leading to reduced difference between saturation and superheat conditions. As a result,the influence of nonequilibrium conditions on droplet vaporization is lower at a higher pressure.展开更多
Phase equilibria in the Si-rich domain of the Si-Fe system have been reassessed based on the recent DTA experimental results. Thermodynamic properties of liquid phase have been reassessed using the associated solution...Phase equilibria in the Si-rich domain of the Si-Fe system have been reassessed based on the recent DTA experimental results. Thermodynamic properties of liquid phase have been reassessed using the associated solution model. The properties of DIA- MOND_A4 mixture phase have been added in order to evaluate the phase equilibria for the pure silicon materials. The assessed system is able to reproduce the experi- mental values in the whole composition range of the Si-Fe system.展开更多
On the basis of regular solution sublattice model, thermodynamic equilibrium of austenite/carbide in Fe-Nb-C ternary system was investigated. The equilibrium volume fraction, chemical driving force of carbide precipit...On the basis of regular solution sublattice model, thermodynamic equilibrium of austenite/carbide in Fe-Nb-C ternary system was investigated. The equilibrium volume fraction, chemical driving force of carbide precipitates and molar fraction of niobium and carbon in solution at different temperatures were evaluated respectively. The volume fraction of precipitates increases, molar fraction of niobium dissolved in austenite decreases and molar fraction of carbon increases with decreasing the niobium content. The driving force increases with the decrease of temperature, and then comes to be stable at relatively low temperatures. The predicted ratio of carbon in precipitates is in good agreement with the measured one.展开更多
Subsolidus phase relations have been determined in the systems SiO2-Cr-O and MgO-SiO2-Cr-O in equilibrium with metallic Cr, at 1100 to 1500℃ and 0 to 2.88 GPa. The results show that there are no ternary phases in the...Subsolidus phase relations have been determined in the systems SiO2-Cr-O and MgO-SiO2-Cr-O in equilibrium with metallic Cr, at 1100 to 1500℃ and 0 to 2.88 GPa. The results show that there are no ternary phases in the SiO2-Cr-O system at these conditions, i.e., only the assemblage eskolaite-Cr-metal-quartz (or tridymite) is found. In the MgO-containing system, however, extensive substitution of Cr2+ for Mg is observed in (Mg, Cr2+)2SiO4 olivine, (Mg, Cr2+)2Si2O6 pyroxene, and (Mg, Cr2+)Cr2O4 spinel. Cr3+ levels in olivine and pyroxene are below detection limits. The pyroxene is orthohombic at XCrPx2+ < 0.2, monoclinic at higher XCrPx2+ . Thestructure of the spinels becomes tetragonally distorted at XCr2+Sp >0.2. The experimental datahave been fitted to a thermodynamic model, and the authors obtained the mixing parameter (W) of Mg-Cr2+ in olivine, pyroxene and spinel, and the relation between temperatures and free energies of formation for the end-members: Cr2+-olivine (Cr2SiO4), Cr2+-pyroxene (Cr2Si2O6) and Cr2+-spinel (Cr3O4).展开更多
文摘Liquid vaporization under thermodynamic phase non-equilibrium condition at the gas-liquid interface is investigated over a wide range of fluid state typical of many liquid-fueled energy conversion systems. The validity of the phase-equilibrium assumption commonly used in the existing study of liquid vaporization is examined using molecular dynamics theories. The interfacial mass flow rates on both sides of the liquid surface are compared to the net vaporization rate through an order-of-magnitude analysis.Results indicated that the phase-equilibrium assumption holds valid at relatively high pressures and low temperatures,and for droplets with relatively large initial diameters(for example,larger than 10 μm for vaporizing oxygen droplets in gaseous hydrogen in the pressure range from 10 atm to the oxygen critical state). Droplet vaporization under superheated conditions is also explored using classical binary homogeneous nucleation theory,in conjunction with a real-fluid equation of state. It is found that the bubble nucleation rate is very sensitive to changes in saturation ratio and pressure;it increases by several orders of magnitude when either the saturation ratio or the pressure is slightly increased. The kinetic limit of saturation ratio decreases with increasing pressure,leading to reduced difference between saturation and superheat conditions. As a result,the influence of nonequilibrium conditions on droplet vaporization is lower at a higher pressure.
基金financially supported by the Research Council of Norway (NFR),under the project "BASIC 191285/V30"
文摘Phase equilibria in the Si-rich domain of the Si-Fe system have been reassessed based on the recent DTA experimental results. Thermodynamic properties of liquid phase have been reassessed using the associated solution model. The properties of DIA- MOND_A4 mixture phase have been added in order to evaluate the phase equilibria for the pure silicon materials. The assessed system is able to reproduce the experi- mental values in the whole composition range of the Si-Fe system.
基金ItemSponsored by National Natural Science Foundation of China (50504007 ,50474086 ,50334010) Liaoning ProvinceScience Foundation (20041009)
文摘On the basis of regular solution sublattice model, thermodynamic equilibrium of austenite/carbide in Fe-Nb-C ternary system was investigated. The equilibrium volume fraction, chemical driving force of carbide precipitates and molar fraction of niobium and carbon in solution at different temperatures were evaluated respectively. The volume fraction of precipitates increases, molar fraction of niobium dissolved in austenite decreases and molar fraction of carbon increases with decreasing the niobium content. The driving force increases with the decrease of temperature, and then comes to be stable at relatively low temperatures. The predicted ratio of carbon in precipitates is in good agreement with the measured one.
文摘Subsolidus phase relations have been determined in the systems SiO2-Cr-O and MgO-SiO2-Cr-O in equilibrium with metallic Cr, at 1100 to 1500℃ and 0 to 2.88 GPa. The results show that there are no ternary phases in the SiO2-Cr-O system at these conditions, i.e., only the assemblage eskolaite-Cr-metal-quartz (or tridymite) is found. In the MgO-containing system, however, extensive substitution of Cr2+ for Mg is observed in (Mg, Cr2+)2SiO4 olivine, (Mg, Cr2+)2Si2O6 pyroxene, and (Mg, Cr2+)Cr2O4 spinel. Cr3+ levels in olivine and pyroxene are below detection limits. The pyroxene is orthohombic at XCrPx2+ < 0.2, monoclinic at higher XCrPx2+ . Thestructure of the spinels becomes tetragonally distorted at XCr2+Sp >0.2. The experimental datahave been fitted to a thermodynamic model, and the authors obtained the mixing parameter (W) of Mg-Cr2+ in olivine, pyroxene and spinel, and the relation between temperatures and free energies of formation for the end-members: Cr2+-olivine (Cr2SiO4), Cr2+-pyroxene (Cr2Si2O6) and Cr2+-spinel (Cr3O4).
