Gas-solid Two-phase Jet Research Articles

Numerical study on coupled flow characteristics of a gas-solid two-phase jet in a supersonic crossflow

In this study, the Eulerian-Lagrangian scheme coupled with the gas-solid two-phase Reynolds-average Navier-Stokes (RANS) method was used to study the airflow and particles flow characteristics of particles of different diameters injected into a supersonic flow field by a sonic jet. The results show that introducing small particles has little effect on the flow field. When the particle diameter is 1e-6 m, most particles are mainly distributed in the shear layer, and some parts of the particles are sucked into the surface trailing counter-rotating vortex pairs (TCVP) and the wall boundary layers by the airflow. The introduction of large diameter particles hinders the jet's development, reduces the Mach disk's height, and makes the counter-rotating vortex pair (CVP) closer to the wall. This leads to a decrease in the streamwise velocity and an increase in the wall-normal velocity near the wall downstream of the jet. The streamwise velocity increases and the wall-normal velocity decreases at the far wall downstream of the jet. At the same time, it exacerbates the Kelvin-Helmholtz (K-H) instability in the shear layer on the windward side of the jet, forming a large-scale coherent structure between the shear layer and crossflow. The penetration depth and diffusion range of particles increase with particle diameter and density, and the velocity decreases with particle diameter increase by comparing the trajectories of particles with different diameters and densities.

Numerical Simulation of Gas-solid Jet Fire in Natural Gas Pipeline Leakage

Aiming at the problem that gas-solid two-phase jet flame formed by jet fire entrained by natural gas pipeline leakage is less studied, the gas-solid two-phase jet and pure gas-phase jet flame models formed by natural gas pipeline leakage are established by FLUENT software. The differences between the gas-solid two-phase jet and the pure gas-phase jet flame were comparatively studied, and the effect of different particle size on flame height, temperature and radiation of gas-solid jet was analyzed. The results indicate that the solid particles entering the flame will lead to a lower temperature compared to a gas-jet-only flame. The larger the mass flow of solid particles is, the lower the flame temperature of the gas-solid jet will be, and the corresponding flame height and radiation hazards are also reduced. The present study findings can be used for the purpose of studying gas-solid two-phase jet flame in leakage of natural gas pipelines.

Powder fuel transport process and mixing characteristics in cavity-based supersonic combustor with different injection schemes

The transport process and mixing characteristics of powder fuel in the supersonic airflow are essential for the working performance of a powder fueled scramjet. In the current investigation, the effect of different injection schemes on the powder fuel jet flow field and mixing characteristics are numerically studied in the cavity-based supersonic combustion chamber. The simulation is employed by the Eulerian-Lagrangian scheme coupling with the gas-solid two-phase Reynolds-average Navier-Stokes (RANS) method. Verification of numerical method and grid-independent is conducted firstly, which demonstrated the correctness and credibility of the method in this research. The results show that the powder fuel injection into the combustor induces typical gas-solid two-phase jet flow characteristics. With respect to the fuel injection schemes upstream of the cavity, the powder fuel moves across the cavity section and is continuously mixed with the mainstream along the flow direction. The mixing intensity in the combustion chamber is associated with the motion and distribution patterns of the particles. For the cavity internal fuel injection scheme, the particles are mainly distributed inside the cavity. Some of the particles can be coiled and sucked into the supersonic mainstream. The cavity shear layer and expansion section near the bottom wall is the main region with better mixing performance.

DEM–CFD simulation of the particle dispersion in a gas–solid two-phase flow for a fuel-rich/lean burner

The objective of this study was to numerically investigate the particle dispersion mechanisms in the gas–solid two-phase jet for a fuel-rich/lean burner by means of coupling the discrete element method (DEM) with the computational fluid dynamics (CFD). The DEM was employed to deal with the particle–particle and the particle–wall interaction in the computation of solid flow; while gas flow was computed by CFD based on the commercial software package Fluent. The particles with various Stokes numbers equal to 0.1, 0.5, 1, 2 and 3 (corresponding to particle diameter 10.8, 24.17, 34.18, 48.38 and 59.21μm, respectively) in the gas–solid fuel-rich/lean jet were investigated in this study. The particle–particle collision was simulated and its effect on the fuel-rich/lean separating performance was evaluated. The results show that the particle–particle collision occurred more frequently with the increasing of Stokes numbers from 0.1 to 3. The particle dispersion became more uniform between the fuel-rich side and the fuel-lean side for particles with small Stokes number; while for particles at St>1, a better fuel-rich/lean separating performance was achieved. The efficiency of the DEM–CFD coupling method was validated by the corresponding experiments, and a good agreement between the simulation and experiments was achieved as a result of the particle–particle collision.

Experimental investigation on flow structures and mixing mechanisms of a gas–solid burner jet

The objective of this study was to investigate the flow structures and mixing mechanisms of a gas–solid two-phase jet from a burner employed in the utility boiler. Laboratory experiments were conducted in a 0.15 m internal diameter test facility. Gas–solid jet flow downstream of the burner exit was measured by a fiber optic probe. Local solid concentration and particle size distribution were obtained using the probe that was traversed over the cross-section of the jet. The effects of the side flow on the primary air gas–solid flow characteristics were also studied. The measurements showed the availability of fiber optic probe to investigate the gas–solid jet flow downstream the industrial burner nozzle with high solid concentration. Obvious slip between the gas phase and the solid phase in the gas–solid jet flow was found in the experiments. The side flow disturbed the solid concentration distribution in the jet, a more smooth solid concentration profile across the jet can be achieved after the side flow was introduced. The particle size distributions in the jet were similar with the distributions of the solid concentration, the particles with large diameters always appeared in the zones where the solid concentrations were high.

Detached eddy simulation of particle dispersion in a gas-solid two-phase fuel rich/lean burner flow

To predict the particle dispersion in the burner jet is of great importance in industrial application and in the designing of coal burner with good performance. The objective of this study was to numerically investigate the particle dispersion mechanisms in the gas–solid two-phase jet from a fuel rich/lean burner. The detached-eddy-simulation (DES) approach was employed to study the turbulent flow in the fuel rich/lean separator and the gas–solid multiphase jet from the exit of a fuel rich/lean burner. The vortex shedding process was simulated and its effect on the fuel rich/lean separating performance was evaluated. Combined with the Lagrangian tracking procedure for the particle phase, the coal particles with various Stokes numbers equal to 0.000434, 0.043, 1.08, 4.34 (corresponding to particle diameter 1, 10, 50, 100 μm, respectively) in the gas–solid fuel rich/lean jet were studied, which shows that although there are coherent vortex structures behind the central partition plate, these vorticities are small, the fuel-rich stream and the fuel lean stream will not mix quickly downstream of the exit of the nozzle. The large vortex structures at the jet outer boundary are the main factors that make the small particles to mix together. The coal particles with large Stokes number (St>1) disperse very slowly in the jet flow, which realizes the fuel rich/lean combustion in a rather long distance downstream the exit of the nozzle, resulting in low NO x emissions.

Direct Numerical Simulation for Three-Dimensional Gas-Solid Two-Phase Jet Using Two-Way Method and Experimental Verification.

Current progress in the field of supercomputers has made possible the direct numerical simulation of the gas-solid two-phase jet based on the Navier-Stokes equation and the Lagrangian equation of particle motion without the use of any assumptions or simplified models. In this study, three-dimensional Eulerian air velocities and Lagrangian particle trajectories are simultaneously calculated to describe the interaction between particles and air using a two-way method. Although the mesh size is roughly seven times the Kolmogorov microscale, the calculated turbulent characteristics of air and particles (mean velocity distributions and turbulent intensity distributions) are in fairly good agreement with experimental data obtained using laser Doppler anemometry. This means that the simulation well describes the motion of large-scale eddies which play an important role in the formation of turbulent gas-solid two-phase flow.

Direct Numerical Simulation for Three-Dimensional Gas-Solid Two-Phase Jet Using Two-Way Method and Experimental Verification.

Current progress in the field of supercomputers has made possible the direct numerical simulation of the gas-solid two-phase jet based on the Navier-Stokes equation and the Lagrangian equation of the particle motion without the use of any assumptions or models. In this study, three-dimensional Eulerian air velocities and Lagrangian particle trajectories are simultaneously calculated to describe the interaction between particles and air using a two-way method. Although the mesh size is roughly seven times the Kolmogorov microscale, the calculated turbulent characteristics of air and particles (mean velocity distributions and turbulent intensity distributions) are in fairly good agreement with experimental data obtained using laser Doppler anemometry. This means that the simulation well describes the motion of large-scale eddies which play an important role in the formation of turbulent gas-solid two-phase flow.