A CORRELATION EQUATION FOR CALCULATING INCLINED JET PENETRATION LENGTH IN A GAS-SOLID FLUIDIZED BED

Numerical simulation of gas-solid flow in a two-dimensional fluidized bed with an inclined jet was performed. The numerical model is based on the two-fluid model of gas and solids phase in which the solids constitutive equations are based on the kinetic theory of granular flow. The improved ICE algorithm, which can be used for both low and high-velocity fluid flow, were used to solve the model equations. The mechanism of jet formation was analyzed using both numerical simulations and experiments. The emergence and movement of gas bubbles were captured numerically and experimentally. The influences of jet velocity, nozzle diameter, nozzle inclination and jet position on jet penetration length were obtained. A semi-empirical expression was derived and the parameters were correlated from experimental data. The correlation equation, which can be easily used to obtain the inclined jet penetration length, was compared with our experimental data and published correlation equations.

Numerical Simulation of Slurry Diffusion in Fractured Rocks Considering a Time-Varying Viscosity

To analyze the effects of a time-varying viscosity on the penetration length of grouting,in this study cement slur-ries with varying water-cement ratios have been investigated using the Bingham’sfluidflow equation and a dis-crete element method.Afluid-solid coupling numerical model has been introduced accordingly,and its accuracy has been validated through comparison of theoretical and numerical solutions.For different fracture forms(a single fracture,a branch fracture,and a fracture network),the influence of the time-varying viscosity on the slurry length range has been investigated,considering the change in the fracture aperture.The results show that under different fracture forms and the same grouting process conditions,the influence of the time-varying viscosity on the seepage length is 0.350 m.

Mixing of A Non-Circular Jet into A Counterflow

An elliptic jet and a square jet flowing into a counterflow with different jet-to-current velocity ratios are investigated by using realizable Ice model. Some computed mean velocity and scalar features agree reasonably well with experimental measurements, and more features are obtained by analyzing the computed results. After fluid issues from a nozzle, it entrains ambient fluid, and its velocity and concentration on the centerline decay with the distance downstream from the potential core （10）. The decay ratio increases with the decreasing jet-to-current velocity ratio a. For an elliptic jet, the evolution of the excess velocity half-width b and the concentration half-width be merely remains constant near the jet exit on major-axis plane while they increase linearly on the minor-axis plane. However, the half-widths on the major-axis and minor-axis plane become proportional to the axial distance downstream after equaling each other. For a square jet, b and bc increase linearly with the distance downstream from the jet exit, but the spread ratio is larger on the middle plane than that on the diagonal plane before they equal each other. The radial extent of the dividing streamline r~ or the mixing boundary rs~ increases linearly downstream, and decreases exponentially after reaching a peak at Xb. The ratio on the minor-axis plane is larger than that on the major-axis plane for an elliptic jet. The characteristics are the same for the square jet. b, be, rs, and rsc on two corresponding planes become equal to each other more rapidly for the square jet than for the elliptic jet, because the sharp comer of the square nozzle induces secondary structures that are more intense. The distributions of the excess axial velocity and scalar concentration exhibit self-similarity for either the elliptic jet or square jet in the region of 10 〈 x 〈 xb. On the cross section, four counter-rotating pairs of vortices, which enhance the entrainment between the jet and counterflow, form at the four comers of the square jet or at the two ends of the major-axis plane of the elliptic jet. The recirculation pattern formed by these axial vortices is more complex for the square jet than that for the elliptic jet. The turbulent kinetic energy k have large value in the region near the jet exit and stagnation point. The maximum value ofk for the square jet is larger than that of the elliptic jet near the jet exit. This results in the square jet mixing more strongly than the elliptic jet.

Experimental Study on the Penetration of Diesel and Biodiesel Spray Liquid Emerging from an Equilateral Triangular Orifice under Evaporative Conditions

This paper reports the results of an experimental study on the liquid phase characteristics of the biodiesel and diesel discharged from an equilateral triangular orifice and a circular orifice under different injection conditions by Mie-scattering imaging.The results revealed that the biodiesel liquid penetration length was longer than that of diesel under the same injection conditions.In addition,the increase of the chamber pressure was expected to enhance the interaction between air and fuel,resulting in the acceleration of the liquid phase breakup process.Moreover,with increasing chamber temperature,the liquid penetration of biodiesel was reduced less than that of diesel.This was due to the high surface tension and viscosity of biodiesel which inhibited the chamber air entrainment and suppressed the liquid breakup process.Accordingly,the higher probability of shorter diesel liquid penetration length indicated better air-fuel mixing than that of biodiesel.Besides,the triangular orifice liquid length was shorter than that of the circular orifice.And the stabilized liquid cone angle from the circular orifice was larger than that from the triangular orifice,indicating that using an equilateral triangular orifice has the potential to improve the air-fuel mixing process.

Simulation on Evaporation and Motion of Atomized Droplets in Spray Dry Flue Gas Desulfurization Tower

The evaporation and motion of atomized droplets have an essential effect on the safe and efficient long-term operation of the desulphurization tower. Therefore, the two-phase flow model is established and solved by three-dimensional steady Reynolds-averaged Navier-Stokes equations;the droplets are tracked by Eulerian-Lagrangian method. The three factors, including inlet swirling flow of flue gas, initial droplet diameter, and inlet flue gas temperature, are analyzed to show the effects on the evaporation and motion of atomized droplets, respectively. The results show that the swirling flow of flue gas and initial droplet diameter dominate the penetration length of the atomized droplets and the mixing characteristic of droplets and flue gas. With the increase of droplet diameter, the length of droplet penetrating flue gas increases. When droplet diameter is 200 μm and inlet swirl number is 0.35, droplets completely penetrate the core area. Therefore, this is the maximum initial droplet diameter at the inlet swirl number of 0.35. The droplets evaporation time of initial 150 μm diameter is 85.5% longer than that of 50 μm droplets(0.35 of inlet swirl number). Increasing the inlet flue gas temperature can enhance the heat transfer. When inlet flue gas temperature rises from 483 K to 523 K, the evaporation time decreases by 33.8%. The results can be used to guide the optimization of droplets spray evaporation under practical operating conditions in the desulfurization tower.