This article investigates the role of the specularity coefficient(φ,the extent of the energy dissipation due to particle-wall collisions),inter-particle restitution coefficient(e_(pp),the extent of the energy dissipa...This article investigates the role of the specularity coefficient(φ,the extent of the energy dissipation due to particle-wall collisions),inter-particle restitution coefficient(e_(pp),the extent of the energy dissipation due to inter-particle collisions),and four combinations of these variables on the hydrodynamics,and the pressure recovery of the dilute gas-solid suspension in a diffuser.The investigation applies the two-fluid modeling approach along with the kinetic theory of the granular flow.The present investigation’s findings indicate that an increase inφor a reduction in e_(pp) reduces the pressure recovery by weakening the reverse momentum transfer phenomenon,which is recognized as the primary means for the pressure recovery.Besides,in a gas-solid flow system,a higherφor smaller e_(pp) enhances the particles’trapping in the recirculation zone.The recirculation zone’s strength and size increase asφincreases or e_(pp) reduces.Moreover,an increase in the wall-particle and inter-particle interactions strengthens the sidewise displacement of the particles.The effect of the wall-particle and inter-particle interactions are insignificant for extremely small solid loading.展开更多
In this study,a turbulent non-premixed(diffusion)methane-air flame has been investigated computationally to analyze the influences of pressure and gravity on flame structure and sooting characteristics between 1 and 1...In this study,a turbulent non-premixed(diffusion)methane-air flame has been investigated computationally to analyze the influences of pressure and gravity on flame structure and sooting characteristics between 1 and 10 atm.The simulation has been conducted in a 2-D axisymmetric computational domain using the finite volume-based computational fluid dynamics(CFD)code.The interaction of turbulence and chemistry is modeled by considering the steady laminar flamelet model(SLFM)and the GRI Mech 3.0 chemical mechanism.The radiative heat transfer calculation is carried out by considering the discrete ordinate(DO)method and the weighted sum grey gas model(WSGGM).The semi-empirical Moss-Brookes model is considered to calculate soot.The impact of gravity on flame and sooting characteristics are evaluated by comparing the normal-gravity flames with the zero-gravity flames.The effect of soot and radiation on flame temperature is also examined.The results show a close agreement with the measurement when both soot and radiation are included in the numerical modeling.The rates of soot formation,surface growth,and oxidation increase with increased operating pressure,regardless of gravity.Zero-gravity flames have a higher soot volume fraction,a wider soot-containing zone,a higher CO mass fraction,and a lower flame temperature than normal-gravity flames while maintaining constant pressure.In normal-gravity flames,the CO mass fraction decreases with pressure,whereas it increases with pressure rise in flames of zero gravity.Flames of zero gravity appear taller and broader compared to the flames of normalgravity for a fixed pressure.An increase in pressure significantly reduces the flame length and width in normal-gravity flames.However,the pressure elevation has little effect on the shape of a zero-gravity flame.The outcomes of the present study will assist in fully understanding the combustion and sooting characteristics of turbulent diffusion flames that will help design and develop high-efficiency,pollutant-free combustion devices and fire suppression systems for space application.展开更多
文摘This article investigates the role of the specularity coefficient(φ,the extent of the energy dissipation due to particle-wall collisions),inter-particle restitution coefficient(e_(pp),the extent of the energy dissipation due to inter-particle collisions),and four combinations of these variables on the hydrodynamics,and the pressure recovery of the dilute gas-solid suspension in a diffuser.The investigation applies the two-fluid modeling approach along with the kinetic theory of the granular flow.The present investigation’s findings indicate that an increase inφor a reduction in e_(pp) reduces the pressure recovery by weakening the reverse momentum transfer phenomenon,which is recognized as the primary means for the pressure recovery.Besides,in a gas-solid flow system,a higherφor smaller e_(pp) enhances the particles’trapping in the recirculation zone.The recirculation zone’s strength and size increase asφincreases or e_(pp) reduces.Moreover,an increase in the wall-particle and inter-particle interactions strengthens the sidewise displacement of the particles.The effect of the wall-particle and inter-particle interactions are insignificant for extremely small solid loading.
基金Authors(SG,VMR,SKD)would like to acknowledge the support received from the Institute seed grant(ISIRD)project(KNH).
文摘In this study,a turbulent non-premixed(diffusion)methane-air flame has been investigated computationally to analyze the influences of pressure and gravity on flame structure and sooting characteristics between 1 and 10 atm.The simulation has been conducted in a 2-D axisymmetric computational domain using the finite volume-based computational fluid dynamics(CFD)code.The interaction of turbulence and chemistry is modeled by considering the steady laminar flamelet model(SLFM)and the GRI Mech 3.0 chemical mechanism.The radiative heat transfer calculation is carried out by considering the discrete ordinate(DO)method and the weighted sum grey gas model(WSGGM).The semi-empirical Moss-Brookes model is considered to calculate soot.The impact of gravity on flame and sooting characteristics are evaluated by comparing the normal-gravity flames with the zero-gravity flames.The effect of soot and radiation on flame temperature is also examined.The results show a close agreement with the measurement when both soot and radiation are included in the numerical modeling.The rates of soot formation,surface growth,and oxidation increase with increased operating pressure,regardless of gravity.Zero-gravity flames have a higher soot volume fraction,a wider soot-containing zone,a higher CO mass fraction,and a lower flame temperature than normal-gravity flames while maintaining constant pressure.In normal-gravity flames,the CO mass fraction decreases with pressure,whereas it increases with pressure rise in flames of zero gravity.Flames of zero gravity appear taller and broader compared to the flames of normalgravity for a fixed pressure.An increase in pressure significantly reduces the flame length and width in normal-gravity flames.However,the pressure elevation has little effect on the shape of a zero-gravity flame.The outcomes of the present study will assist in fully understanding the combustion and sooting characteristics of turbulent diffusion flames that will help design and develop high-efficiency,pollutant-free combustion devices and fire suppression systems for space application.