Rare earth oxide was prepared via direct pyrolysis of rare earth chloride solution. Based on this technique, a new-type jet-flow pyrolysis reactor was designed, and then the fluid dynamics (pressure and velocity) insi...Rare earth oxide was prepared via direct pyrolysis of rare earth chloride solution. Based on this technique, a new-type jet-flow pyrolysis reactor was designed, and then the fluid dynamics (pressure and velocity) inside the reactor was numerically simulated using a computational fluid dynamics method. The self-produced pressure (p) and the fuel inlet velocity (v) satisfied a quadratic function,p=0.06v2+0.23v?4.49. To fully utilize the combustion-generated heat in pyrolysis of rare earth chloride, an appropriate external pressure p=v2+3v?4.27 should be imposed at the feed inlet. The 1.25- and 1.5-fold increase of feed inlet diameter resulted in decline of adsorption dynamic pressure, but the intake of rare earth chloride increased by more than 30% and 60%, respectively. The fluid flow in the reactor was affected by the feeding rate; the fluid flow peaked near the throat of venturi and gradually smoothed down at the jet-flow reactor’s terminal along with the sharp decline of feeding rate.展开更多
The present study deals with analytical investigation of temperature of a single burning iron particle.Three mathematical methods including AGM(Akbari-Ganji’s method),CM(Collocation method)and GM(Galerkin Method)are ...The present study deals with analytical investigation of temperature of a single burning iron particle.Three mathematical methods including AGM(Akbari-Ganji’s method),CM(Collocation method)and GM(Galerkin Method)are applied to solving non-linear differential governing equation and effectiveness of these methods is examined as well.For further investigation,forth order Runge-Kutta approach,a numerical method,is used to validate the obtained analytical results.In the present study,the developed mathematical model takes into account the effects of thermal radiation,convective heat transfer and particle density variations during combustion process.Due to particles’small size and high thermal conductivity,the system is assumed to be lumped in which the particle temperature does not change within the body and all of its regions are at the same temperature.The temperature distributions obtained by analytical methods have satisfactory agreement with numerical outputs.Finally,the results indicate that AGM is a more appropriate method than GM and CM due to its lower mean relative error and less run time.展开更多
Following an order analysis of key parameters, a decoupled procedure for simulation of convection-radiation heat transfer problems in supersonic combustion ramjet(scramjet) engine was developed. The radiation module o...Following an order analysis of key parameters, a decoupled procedure for simulation of convection-radiation heat transfer problems in supersonic combustion ramjet(scramjet) engine was developed. The radiation module of the procedure consisted of Perry 5GG weighted sum gray gases model for spectral property calculation and discrete ordinates method S4 scheme for radiative transfer computation, while the flow field was computed using the Favrè average conservative Navier-Stokes(N-S) equations, in conjunction with Menter's k-ω SST two-equation model. A series of 2D supersonic nonreactive turbulent channel flows of radiative participants with selective parameters were simulated for validation purpose. Radiative characteristics in DLR hydrogen fueled and NASA SCHOLAR ethylene fueled scramjets were numerically studied using the developed procedure. The results indicated that the variations of spatial distributions of the radiative source and total absorption coefficient are highly consistent with those of the temperature and radiative participants, while the spatial distribution of the incident radiation spreads wider. It also demonstrated that the convective heating is significantly affected by the complexity of the flow field, such as the shock wave/boundary layer interactions, while the radiative heating is simply an integral effect of the whole flow field. Although the radiative heating in the combustion chambers reaches a certain level, an order of magnitude of 10 k W/m2, it still contributes little to the total heat transfer(<7%).展开更多
基金Projects(51204040,U1202274)supported by the National Natural Science Foundation of ChinaProjects(2010AA03A405,2102AA062303)supported by the National High-tech Research and Development Program of China+1 种基金Project(2012BAE01B02)supported by the National Science and Technology Support Program of ChinaProject(N130702001)supported by the Fundamental Research Funds for the Central Universities,China
文摘Rare earth oxide was prepared via direct pyrolysis of rare earth chloride solution. Based on this technique, a new-type jet-flow pyrolysis reactor was designed, and then the fluid dynamics (pressure and velocity) inside the reactor was numerically simulated using a computational fluid dynamics method. The self-produced pressure (p) and the fuel inlet velocity (v) satisfied a quadratic function,p=0.06v2+0.23v?4.49. To fully utilize the combustion-generated heat in pyrolysis of rare earth chloride, an appropriate external pressure p=v2+3v?4.27 should be imposed at the feed inlet. The 1.25- and 1.5-fold increase of feed inlet diameter resulted in decline of adsorption dynamic pressure, but the intake of rare earth chloride increased by more than 30% and 60%, respectively. The fluid flow in the reactor was affected by the feeding rate; the fluid flow peaked near the throat of venturi and gradually smoothed down at the jet-flow reactor’s terminal along with the sharp decline of feeding rate.
文摘The present study deals with analytical investigation of temperature of a single burning iron particle.Three mathematical methods including AGM(Akbari-Ganji’s method),CM(Collocation method)and GM(Galerkin Method)are applied to solving non-linear differential governing equation and effectiveness of these methods is examined as well.For further investigation,forth order Runge-Kutta approach,a numerical method,is used to validate the obtained analytical results.In the present study,the developed mathematical model takes into account the effects of thermal radiation,convective heat transfer and particle density variations during combustion process.Due to particles’small size and high thermal conductivity,the system is assumed to be lumped in which the particle temperature does not change within the body and all of its regions are at the same temperature.The temperature distributions obtained by analytical methods have satisfactory agreement with numerical outputs.Finally,the results indicate that AGM is a more appropriate method than GM and CM due to its lower mean relative error and less run time.
基金supported by the National Natural Science Foundation of China(Grant No.11202014)
文摘Following an order analysis of key parameters, a decoupled procedure for simulation of convection-radiation heat transfer problems in supersonic combustion ramjet(scramjet) engine was developed. The radiation module of the procedure consisted of Perry 5GG weighted sum gray gases model for spectral property calculation and discrete ordinates method S4 scheme for radiative transfer computation, while the flow field was computed using the Favrè average conservative Navier-Stokes(N-S) equations, in conjunction with Menter's k-ω SST two-equation model. A series of 2D supersonic nonreactive turbulent channel flows of radiative participants with selective parameters were simulated for validation purpose. Radiative characteristics in DLR hydrogen fueled and NASA SCHOLAR ethylene fueled scramjets were numerically studied using the developed procedure. The results indicated that the variations of spatial distributions of the radiative source and total absorption coefficient are highly consistent with those of the temperature and radiative participants, while the spatial distribution of the incident radiation spreads wider. It also demonstrated that the convective heating is significantly affected by the complexity of the flow field, such as the shock wave/boundary layer interactions, while the radiative heating is simply an integral effect of the whole flow field. Although the radiative heating in the combustion chambers reaches a certain level, an order of magnitude of 10 k W/m2, it still contributes little to the total heat transfer(<7%).
