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.

The numerical simulation of the movements and thermal states of atomized metal droplets in the spray forming process

Numerical simulation was performed in an atomizing chamber to investigate the movements and thermal states of the atomized metal droplets in the spray forming process. The velocity, temperature and solid fractions of metal droplets with different diameters and under different atomizing pressures were investigated. The results indicate that a higher atomizing pressure results in the increased flying velocity of the metal droplets and a decrease in the cone-shaped angle formed by their flight paths. Synchronously, the cooling of the metal droplets is accelerated and the time of the complete solidification process is shortened. Under the same atomization pressure, large metal droplets have a lower flying speed and a lower rate of temperature decrease in the atomizing chamber than small metal droplets. In addition, metal droplets flying along the edge of the atomizing region cool faster than those flying in the core region.

MODELING OF A SOLID CONE PRESSURE-SWIRL ATOMIZER

A Ballistic Modeling (BM) / Discrete Droplet Modeling (DDM) method is used to de- termine the characteristics of a solid cone pressure-swirl atomizer (Dyna Coin nozzle) . The charac- teristic of its liquid spray is of considerable importance to the operation and performance of com- bustion systems. A two-dimensional spray model has been developed to simulate a continuous spray under steady-state condition . This model can simulate the resultant drop-sizc of atomization and reveal the effects of the important physical variables such as fuel injection pressure, air pressure(or density), co-axial air flow and fuel properties on the result of atomization process. Dimensional analysis is used to simulate the drop-size immcdiately after jet breakup and further breakup of the droplets is determined by testifying the critical condition of aerodynamics breakup i.e.(Wed)c= 8 / CD.

Analysis of pneumatic atomizer spray profiles

Our objective is to analyze the atomization processes of a pneumatic atomizer by measuring the size and velocity distributions of droplets in a liquid paint spray. The droplet size and velocity distributions have been determined at different axial positions in the spray; a mathematical description of how these quan- tities vary throughout the spray is then proposed. Additionally, the relative number density of droplets and the relative local mass flux are estimated.