尿素水溶液雾化热分解特性的建模及模拟研究  

Simulation and Modeling on Thermal Decomposition Characteristics of Urea-Water-Solution Atomization

作　　者：周英贵[1] 金保昇[1] 

机构地区：[1]东南大学能源与环境学院,江苏省南京市210096

出　　处：《中国电机工程学报》2012年第26期37-42,144,共6页Proceedings of the CSEE

基　　金：国家自然科学基金项目(51076029)~~

摘　　要：基于FLUENT平台对尿素水溶液（urea-water- solution，UWS）液滴的蒸发和热分解特性进行建模和数值模拟研究。对单个尿素水溶液液滴采用快速混合模型（rapid mixingmodel，RM）模拟液滴蒸发，并考虑运动和变化特性，对尿素水溶液液滴采用拉格朗日轨道模型跟踪；同时建立液滴的化学动力学模型，液滴与气相两相耦合之间考虑了动量、质量和热量，研究发现温度窗口对尿素热分解的重要性：对于给定溶液流量和液滴粒径，温度达到406K 时，液滴中的水几乎就蒸发完全，此时尿素开始逐步热分解，NH3的转化率随温度和停留时间的增加而增加，并在温度 650K以上达到比较好的热分解效果，当温度达到 700～735K 附近时，热分解转化率达到最大值，温度继续升高时，因高温空气的氧使得 NH3被氧化，浓度降低至零。另外，还将计算结果与试验测量数据进行了对比，以保证数值研究结论的可靠性。Numerical study and modeling of the evaporation and thermal decomposition characteristics of urea-water-solution （UWS） droplet in high temperature air was conducted based on Fluent platform. The evaporation of water from a single droplet of urea water solution was investigated theoretically by a rapid mixing （RM） model, which also considers droplet motion and variable properties of the solution. The urea water droplets were treated with Lagrange particle tracking model, assuming a kinetic rate de-volatilization and decomposition model of urea after the evaporation of pure water. Between droplets and gas phase two-way coupling was considered for momentum, mass and heat. It is found that the temperature window is dependent on the liquid flow, and droplet size for given nozzle has great influence on the evaporation and thermal decomposition of urea-water-solution （UWS）. At 406 K most of the water of UWS droplets are already evaporated and urea begins thermal decomposition step by step. Conversion rate of NH3 increases with temperature and residence time increasing, and achieves a good thermal decomposition rate at above 650K and urea is transformed completely into NH3. Between the range of 700 K and 735 K, the simulation results show that 02 oxidizes part of urea＇s thermal decomposition gases to NO under high temperature. In addition, the calculation result was compared with the experimental data measured, to guarantee the reliability of the conclusion drawn from this numerical study.

关 键 词：尿素水溶液 热分解 NH3 转化率 

分 类 号：X511[环境科学与工程—环境工程]