Jianren Fan

Similarity solution of mixed convection with diffusion and chemical reaction over a horizontal moving plate

SummaryThe mixed convective heat and mass transfer over a horizontal plate has been investigated. A diffusion equation with a chemical reaction source term is taken into account. By applying transformation group theory to the analysis of the governing equations, we obtain a similarity solution of the problem in the case that the temperature and concentration at the wall and the moving speed of the plate are proportional to power distributions along the distance from the leading edge. Furthermore the similarity equations have been solved numerically by a fourth-order Runge-Kutta scheme. The numerical results obtained for various values of the Schmidt number, chemical reaction parameter and buoyancy parameters reveal the influence of the parameters on the flow, heat and mass transfer behavior.

Numerical simulation of the flow and combustion processes in a three-dimensional, w-shaped boiler furnace

Numerical simulations of gas-solid flows, heat transfer and gas-particle combustion have been conducted for a three-dimensional, W-shaped boiler furnace. The gas-particle flow, distributions of temperature and concentrations of gaseous constituents, distributions of the rates of heat release, burnout rates of coal particles, and formations of volatiles and CO have been predicted.

Modeling of NOX emissions from a W-shaped boiler furnace under different operating conditions

A numerical model for gas-particle flow dynamics has been combined with an NOx chemistry post-processor to predict the formation of nitric oxide in a three-dimensional, W-shaped boiler furnace burning pulverized fuel. The model includes complex interactions in gas-particle turbulent flow, heat transfer, gaseous chemical reaction, coal combustion, and NOx reaction chemistry. Because fuel nitrogen is released in proportion to burnout of pulverized coal particles, the particles are treated in a Lagrangian framework in order to track burning pulverized coal particles through the gas continuum. The results show capability of the model to describe NOx emissions under different operating conditions for full and partial loads.

Modeling of coal combustion and NOx formation in a W-shaped boiler furnace

A numerical model for the gas-particle flow dynamics has been combined with a NOx – chemistry post-processor to predict the formation of nitric oxide in a three-dimensional, W-shaped boiler furnace burning pulverized fuel. The model includes the complex interaction of gas-particle turbulent flow, heat transfer, gaseous chemical reaction, coal combustion, and NOx reaction chemistry. Because the fuel nitrogen is released in proportion to the burnout of the pulverized coal particles, the particles are treated in a Lagrangian framework in order to track burning pulverized coal particles through the gas continuum. The results show the capability of the model for describing NOx emissions under different operating conditions for full and partial load.

PARTICLE CONCENTRATION AND SIZE MEASUREMENTS IN TWO-PHASE TURBULENT COAXIAL JETS

Particle concentration and particle size distributions have been measured for two-phase (solid/air) turbulent coaxial jets using the Laser Diffraction Method (LDM) and a tomography data transform technique. Effects of velocity ratio, particle loading ratio, and particle size on the dispersions of gas and particles were determined. Experimental results show that the gas disperses much more rapidly than the particles and particle dispersion decreases with increasing in particle size. Increasing velocity ratio significantly increases gas dispersion, while effects of other variables are less significant. The mean particle size at the jet edge is about 15-20% smaller than that at the jet centerline. The turbulent Schmidt number Scp for two-phase turbulent coaxial jets ranges from 1.4 to 1.5.

Numerical study of a dense gas–solid jet flow

A new approach using both Eulerian and Lagrangian coordinates and taking account of inter-particle interactions has been developed for the study of gas–solid flows. A numerical algorithm is presented. Comparison with experimental results shows reasonably good agreement.

Particle-turbulence interactions in the turbulent boundary layer for cross flow over a tube

Abstract The turbulent fluid and particle interaction in the turbulent boundary layer for cross flow over a tube was studied experimentally. A phase Doppler anemometer (PDA) was used to measure the mean and fluctuation velocities of both phases. Two size ranges of particles (30–60 μm and 80–150 μm) at certain concentrations were used to investigate the effect of the particle size on the mean velocity profiles and turbulent intensity levels. The measurements clearly demonstrated that the larger particles damped the fluid turbulence. For the smaller particles, this damping effect was less noticeable. The measurement further showed a delay in the separation point for two-phase turbulent cross flow over a tube.

NUMERICAL SIMULATION OF THE EFFECT OF VELOCITY RATIO ON THE FLOW CHARACTERISTICS IN A COAXIAL JET

Abstract Previous experimental work shows that velocity ratio is the principal independent variable to determine the flow behavior of coaxial jets. This study focusing on the effect of velocity ratio on the flow characteristics such as the velocity and kinetic energy profiles, centerline velocity decaying, flow growing and entraining of the jet, presents a detailed numerical simulation of a coaxial jet with a secondary parallel moving stream. It is found that radial profiles of the mean velocity component u depending on the velocity ratio show good similarity in the fully developed zone. Compared with available experimental data, the results show that the use of standard κ-e model leads to good agreement between the numerical results and experimental data.

Group Theory Analysis of Free Convective Boundary- Layer Behavior at a Stretching Surface

In the present study, free convection and heat transfer behavior of electrically conducting fluid in the boundary layer over a vertical continuously stretching surface is investigated. The effects of free convection, magnetic field, suction/blowing at the surface and the stretching speed of the surface on the flow and heat transfer characteristics are considered. By applying one-parametric group theory to analysis of the problem, a similarity solution is found. The governing equations of continuity, momentum and energy are solved numerically by a fourth-order Runge-Kutta scheme. The numerical results, which are obtained for the flow and heat transfer characteristics, reveal the influences of the parameters.