Combustible gases in coal mines are composed of methane, hydrogen, some multi-carbon alkane gases and other gases. Based on a numerical calculation, the explosion limits of combustible gases were studied, showing that...Combustible gases in coal mines are composed of methane, hydrogen, some multi-carbon alkane gases and other gases. Based on a numerical calculation, the explosion limits of combustible gases were studied, showing that these limits are related to the concentrations of different components in the mixture. With an increase of C4H10 and C6H14, the Lower ExplosionLimit （LEL） and Upper Explosion-Limit （UEL） of a combustible gas mixture will decrease clearly. For every 0.1% increase in C4H10 and C6H14, the LEL decreases by about 0.19% and the UEL by about 0.3%. The results also prove that, by increasing the amount of H2, the UEL of a combustible gas mixture will increase considerably. If the level of HE increases by 0.1%, the UEL will increase by about 0.3%. However, H2 has only a small effect on the LEL of the combustible gas mixture. Our study provides a theoretical foundation for judging the explosion risk of an explosive gas mixture in mines.展开更多
The present work is concerned with determining the viscosity,diffusion,thermal diffusion factor and thermal conductivity of five equimolar binary gas mixtures including:CF4-He,CF4-Ne,CF4-Ar,CF4-Kr,CF4-Xe from the prin...The present work is concerned with determining the viscosity,diffusion,thermal diffusion factor and thermal conductivity of five equimolar binary gas mixtures including:CF4-He,CF4-Ne,CF4-Ar,CF4-Kr,CF4-Xe from the principle of corresponding states of viscosity by the inversion technique.The Lennard-Jones (12-6) model potential is used as the initial model potential.The calculated interaction potential energies obtained from the inversion procedure is employed to reproduce the viscosities,diffusions,thermal diffusion factors,and thermal conductivities.The accuracies of the calculated viscosity and diffusion coefficients were 1% and 4%,respectively.展开更多
The flow and the temperature in the threestream mixing flow of the lobed nozzle mixer-ejector with double-wall diffuser are numerically investigated. The domain of computation is divided into sub-domalns according to ...The flow and the temperature in the threestream mixing flow of the lobed nozzle mixer-ejector with double-wall diffuser are numerically investigated. The domain of computation is divided into sub-domalns according to the shapes of the double-plate and lobed nozzle. The three-dimensional body-fitted coordinated grids are generated respectively in these sub-domains by solving Lapalace's equations. Grids are dense on the boundaries and orthogonal at the lobe. The grids of all sub-domains compose the whole grid of the domain. In order to avoid the divergence of the computation as the serious non-orthogonality of the grid from the lobe, the co-located grid, SIMPLEC and Chen-Kim modified k-εturbulence model are applied. The great viscosity, the linear and simultaneous cooperation under-relaxation factors are used to solve the coupling of the fluid and solid. Results show that the air is ejected into the double wall section to form the cooling flow. The wall temperature of the double-wall diffuser is lower than that of the single-wall diffuser. The average wall temperature goes down as the diffuser angle increases at the range of 0～5°,otherwise, the result at the range of 5～10°is opposite.展开更多
It is scientifically important science value and engineering promising to develop the buoyancy-lift integrated hybrid airship for high attitude platform.Through the numerical method,a new tandem wings hybrid airship w...It is scientifically important science value and engineering promising to develop the buoyancy-lift integrated hybrid airship for high attitude platform.Through the numerical method,a new tandem wings hybrid airship with both higher utility value and economy efficiency was obtained and its total performance and technical parameters were analyzed in detail.In order to further improve the lift-drag characteristics,we implemented the optimization design for aerodynamic configuration of tandem wings hybrid airship via the response surface method.The results indicate that the tandem wings hybrid airship has considerable volume efficiency and higher aerodynamic characteristics.After optimization,the lift-drag ratio of this hybrid airship was increased by 6.08%.In a given gross lift condition,tandem wings hybrid airship may provide more payload and specific productivity.Furthermore,the size of tandem airship is smaller so the demand for skin flexible materials can be reduced.Results of this study could serve as a new approach to designing buoyancy-lifting integrated hybrid airship.展开更多
基金Projects 706029 supported by the Cultivation Fund of the Key Scientific and Technical Innovation Project of Ministry of Education of China2007AA04Z332 by the National High Technology Research and Development Program of China
文摘Combustible gases in coal mines are composed of methane, hydrogen, some multi-carbon alkane gases and other gases. Based on a numerical calculation, the explosion limits of combustible gases were studied, showing that these limits are related to the concentrations of different components in the mixture. With an increase of C4H10 and C6H14, the Lower ExplosionLimit （LEL） and Upper Explosion-Limit （UEL） of a combustible gas mixture will decrease clearly. For every 0.1% increase in C4H10 and C6H14, the LEL decreases by about 0.19% and the UEL by about 0.3%. The results also prove that, by increasing the amount of H2, the UEL of a combustible gas mixture will increase considerably. If the level of HE increases by 0.1%, the UEL will increase by about 0.3%. However, H2 has only a small effect on the LEL of the combustible gas mixture. Our study provides a theoretical foundation for judging the explosion risk of an explosive gas mixture in mines.
基金Research Committees of Shiraz University and Shiraz University of Technology for supporting this project and making computer facilities available
文摘The present work is concerned with determining the viscosity,diffusion,thermal diffusion factor and thermal conductivity of five equimolar binary gas mixtures including:CF4-He,CF4-Ne,CF4-Ar,CF4-Kr,CF4-Xe from the principle of corresponding states of viscosity by the inversion technique.The Lennard-Jones (12-6) model potential is used as the initial model potential.The calculated interaction potential energies obtained from the inversion procedure is employed to reproduce the viscosities,diffusions,thermal diffusion factors,and thermal conductivities.The accuracies of the calculated viscosity and diffusion coefficients were 1% and 4%,respectively.
文摘The flow and the temperature in the threestream mixing flow of the lobed nozzle mixer-ejector with double-wall diffuser are numerically investigated. The domain of computation is divided into sub-domalns according to the shapes of the double-plate and lobed nozzle. The three-dimensional body-fitted coordinated grids are generated respectively in these sub-domains by solving Lapalace's equations. Grids are dense on the boundaries and orthogonal at the lobe. The grids of all sub-domains compose the whole grid of the domain. In order to avoid the divergence of the computation as the serious non-orthogonality of the grid from the lobe, the co-located grid, SIMPLEC and Chen-Kim modified k-εturbulence model are applied. The great viscosity, the linear and simultaneous cooperation under-relaxation factors are used to solve the coupling of the fluid and solid. Results show that the air is ejected into the double wall section to form the cooling flow. The wall temperature of the double-wall diffuser is lower than that of the single-wall diffuser. The average wall temperature goes down as the diffuser angle increases at the range of 0～5°,otherwise, the result at the range of 5～10°is opposite.
基金supported by the National High-Tech Research and Development Program of China (Grant No. 863-2007AA11Z243)Foundation for Basic Research of Northwestern Polytechnic University (Grant No.JC-201103)
文摘It is scientifically important science value and engineering promising to develop the buoyancy-lift integrated hybrid airship for high attitude platform.Through the numerical method,a new tandem wings hybrid airship with both higher utility value and economy efficiency was obtained and its total performance and technical parameters were analyzed in detail.In order to further improve the lift-drag characteristics,we implemented the optimization design for aerodynamic configuration of tandem wings hybrid airship via the response surface method.The results indicate that the tandem wings hybrid airship has considerable volume efficiency and higher aerodynamic characteristics.After optimization,the lift-drag ratio of this hybrid airship was increased by 6.08%.In a given gross lift condition,tandem wings hybrid airship may provide more payload and specific productivity.Furthermore,the size of tandem airship is smaller so the demand for skin flexible materials can be reduced.Results of this study could serve as a new approach to designing buoyancy-lifting integrated hybrid airship.
