Lin Wenyi

Surface Tension Gradients on Mixing Processes after Coalescence of Binary Equal-Sized Droplets

Numerical simulations on coalescence of binary equal-sized droplets with surface tension gradients are carried out by using the front tracking method. Mixing process of the fluid from each droplet is investigated. The tangential flow caused by the Marangoni effect and the interface replacement by the fluid with small surface tension coefficient are simulated successfully. Asymmetry caused by the surface tension gradients can generate some extent of mixing within the coalesced droplet. The effects of the surface tension gradients and viscosity on the tangential velocity, replacement time of interface and mixing are investigated.

Evaluation of Presumed Probability-Density-Function Models in Non-Premixed Flames by using Large Eddy Simulation

Four kinds of presumed probability-density-function (PDF) models for non-premixed turbulent combustion are evaluated in flames with various stoichiometric mixture fractions by using large eddy simulation (LES). The LES code is validated by the experimental data of a classical turbulent jet flame (Sandia flame D). The mean and rms temperatures obtained by the presumed PDF models are compared with the LES results. The β-function model achieves a good prediction for different flames. The predicted rms temperature by using the double-δ function model is very small and unphysical in the vicinity of the maximum mean temperature. The clip-Gaussian model and the multi-δ function model make a worse prediction of the extremely fuel-rich or fuel-lean side due to the clip at the boundary of the mixture fraction space. The results also show that the overall prediction performance of presumed PDF models is better at mediate stoichiometric mixture fractions than that at very small or very large ones.

Numerical modeling of three-dimensional flow field and two-dimensional coal combustion in a cylindrical combustor of co-flow jets with large velocity difference

The three-dimensional flow field and two-dimensional coal combustion in a cylindrical combustor of co-flow jets with large velocity difference are studied by numerical simulation. Prediction results show presence of a large central recirculation zone and its remarkable effect on rapid heating, devolatilization and ignition of coal particles, flame stabilization and combustion intensification. For optimum design of such combustors the effect of jet hole location and jet flow rate on sizes and reverse flow rate of this recirculation zone are also studied.

Experimental Studies on CO2 Capture in a Spray Scrubber Using NaOH Solution

Experimental studies on carbon dioxide capture in a spray scrubber are carried out. Fine spray of sodium hydroxide (NaOH) solution is used as CO2 absorbent. Effects of different operating and design parameters, including concentration of NaOH solution, liquid flow rate, total gas flow rate, initial temperature and concentration of carbon dioxide on CO2 removal efficiency are investigated.

Experimental Studies on Carbon Dioxide Desorption from Carbonated Ammonia Solution in a Packed Column

The desorption of carbon dioxide from partially carbonated ammonia solution in a packed column was investigated. The CO2 desorption efficiency and the CO2 desorption rate varies with the process parameters, including desorption temperature, CO2 loading and the total ammonia concentration. The experimental results showed that the CO2 desorption efficiency and the CO2 desorption rate increased with the desorption temperature and the CO2 loading of the carbonated ammonia solution. The CO2 loading played an important role on the selectivity of the CO2 desorption. Experimental results showed that CO2 could be released selectively from high degree carbonated ammonia solution.

Investigation on Carbon Dioxide Regeneration from Ammonium Bicarbonate Solution in a Packed Reactor

The desorption of carbon dioxide from ammonium bicarbonate solution in a packed column was investigated. The CO2 regeneration efficiency and the CO2 regeneration rate were evaluated over ranges of main operating variables, that is, up to 50L/min gas flow rate of N2, 8~24L/h liquid flow rate, 0.4~2.0mol/L ammonium bicarbonate concentration and 60~95¿ temperature. Experimental results suggested that the CO2 regeneration efficiency and the CO2 regeneration rate increased with the gas flow rate of N2, the concentration of ammonium bicarbonate solution and temperature. The temperature played an important role in the decomposition of ammonium bicarbonate solution, the CO2 regeneration efficiency is more than 90% when temperature in the packed column up to 95¿. Experimental results also demonstrated that the decomposition of ammonium bicarbonate solution is a second-order reaction.