RESEARCH ON THE PARTICLE DISPERSION IN THE PARTICULATE TWO-PHASE ROUND JET

In this paper, the three_dimensional vo rtex filament method was used to simulate the evolution of vortex structures in the axisymmetric round jet. The results agree well with the ones given by Chung and Troutt. Then one_coupling model was employed to calculate the particle motio n based on the computed flows. The results show that the particle motion is affe cted by flows obviously at the case of particle number St1 and negligibly at St1 ,particles distribute around the vortex structures uniformly at St ～1 . When perturbations with wavenumber 5 are introduced to vortex rings, part icles disperse wider along radial direction, which conforms to the experimental results. The degree of particle dispersion is in the direct ratio to the amplitu de of perturbation. The conclusions given in the paper are useful to the practic e usage.

Measurements of Non-reacting and Reacting Flow Fields of a Liquid Swirl Flame Burner

The understanding of the liquid fuel spray and flow field characteristics inside a combustor is crucial for designing a fuel efficient and low emission device.Characterisation of the flow field of a model gas turbine liquid swirl burner is performed by using a2-D particle imaging velocimetry（PIV）system.The flow field pattern of an axial flow burner with a fixed swirl intensity is compared under confined and unconfined conditions,i.e.,with and without the combustor wall.The effect of temperature on the main swirling air flow is investigated under open and non-reacting conditions.The result shows that axial and radial velocities increase as a result of decreased flow density and increased flow volume.The flow field of the main swirling flow with liquid fuel spray injection is compared to non-spray swirling flow.Introduction of liquid fuel spray changes the swirl air flow field at the burner outlet,where the radial velocity components increase for both open and confined environment.Under reacting condition,the enclosure generates a corner recirculation zone that intensifies the strength of radial velocity.The reverse flow and corner recirculation zone assists in stabilizing the flame by preheating the reactants.The flow field data can be used as validation target for swirl combustion modelling.

New Statistical Theory and a k-ε-PDF Model for Simulating Gas-particle Flows

A k ε PDF (probability density function) model based on a statistical theory for turbulent gas particle flows is proposed, and a numerical procedure combining the finite difference and finite fluctuating velocity group methods is used. The obtained statistically averaged equations have the same form as that of the equations obtained by the Reynolds averaging. Using the k ε PDF model (PDF particle turbulence model combined with k ε gas turbulence model), many terms, such as the diffusion term in particle Reynolds stress equations, can be exactly calculated for verifying the second order moment model. The k ε PDF model is used to simulate gas particle flows behind a backward facing step. Comparison of the predictions using both k ε PDF and the k ε k p models with experimental results shows that the k ε PDF model gives more reasonable nonisotropic features of particle turbulence.

Numerical Simulation of Gas-particle Flows with Different Swirl Numbers in a Swirl Burner

Swirl burner design was optimized by simulating swirl gas\|particle flows with different swirl numbers at the exit of a small\|scale swirl burner for pulverized\|coal furnaces using the k\|ε\|k p model. The predicted two\|phase time\|averaged velocities and particle concentration distributions for several different cases were compared to improve the design. The effect of the swirl number on the two\|phase velocities and particle concentration was investigated. The results give the two\|phase axial and tangential time\|averaged and fluctuation velocities and particle concentrations, showing that large recirculation zones of gas and particles forms in the near\|axis region of the burner exit, but the particle concentration in the recirculating zone is very low.

Cold Gas-particle Flows in a New Swirl Pulverized-coal Burner by PDPA Measurement

A new type of swirl burner has been developed to stabilize pulverized\|coal combustion by burning different types of coal at different loads and to reduce NO x formation during combustion. The burner uses a device to concentrate the coal powder in the primary\|air tube that divides the primary coal\|air into two streams with different pulverized\|coal concentrations. This paper reports the measurement of gas\|particle flows at the exit of the different swirl burners using a 3\|D Phase Doppler Particle Anemometer (PDPA). The effect of different geometrical configurations on the two\|phase flow field is studied. The results that give the two\|phase flow fields and particle concentrations show the superiority of the new swirl burner.