摘要
本文以洗涤冷却室内气液两相流动为研究对象,分别对鼓泡区分隔板及洗涤冷却管结构进行了优化实验研究。另外,应用Fluent模拟软件对两种工业装置中的洗涤冷却管内热质传递过程和降膜流动特性进行了数值模拟计算。
采用双平行电导探针对洗涤冷却室内气液两相泡状流特性相关参数进行了测量,并以气含率、气泡直径和界面浓度为判断依据,对分隔板结构进行了优化;采用LC0120T型接触式防水加速度传感器测定了不同工况下洗涤冷却管的振动信号,对不同工况下信号的振动能级和振幅的大小进行了比较,并结合鼓泡区气液两相流特性参数的实验结果,分析发现较高气速时可采用无支管洗涤冷却管。
通过对比热模平台下测量得到的实验值与洗涤冷却管内温度分布的模拟值,证实了所选用VOF模型、标准κ-ε湍流模型和所建立传质方程在本文研究系统中的可行性。对长4m的洗涤冷却管内热质传递和降膜流动进行了模拟计算,发现入口降膜厚度、洗涤冷却水入口流速和入口气速对洗涤冷却管出口气体温度和管内液膜流动特性产生了重要的影响;长6.55m的洗涤冷却管,其出口气体温度可以达到659K左右,且当其长度缩短到2m时,出口气体温度值为942K,水蒸气含量可达49%。
The gas-liquid two-phase flow in the water scrubbing-cooling chamber (WSCC) of gasifier was mainly researched in the thesis. The experimental studies of the structure optimization of compartmentation board and dip tube were carried out. At the same time, a two-dimensional numerical simulation was performed to study falling water film flow field and heat and mass transfer in two different industrial-scale dip tubes of WSCC of OMB entrained-flow gasifier.
The characteristic parameters of gas-liquid two-phase flow were measured during experiment by a parallel-wire conductance probe. Based on gas holdup, bubble diameter and surface concentration, the structure of the compartmentation board was optimized. The vibration of dip tube was estimated by a waterproof acceleration sensor of LC0120T type under different conditions. The comparison of vibration energy level and frequency spectrum were discussed in detail. No-branches dip tube was proposed to adopt under higher gas velocities after researching the vibration of dip tube and the characteristic parameters of the gas-liquid two-phase flow in the WSCC.
The predicted axial temperature distribution results were in good agreement with the experimental data measured in the bench-scale dip tube, which validated that the numerical models, including VOF method, standardκ-εturbulent model, mass transfer equations and all the other models applied in this paper were reasonable. The simulation results of 4 m dip tube indicated that the thickness of inlet water falling film, the velocity of inlet quenching water and the inlet velocity of syngas had a great influence on the heat and mass transfer and the flow patterns of the water falling film of industrial-scale dip tube. Furthermore, the results of 6.55 m dip tube revealed that the temperature of the syngas achived 659K at outlet of the dip tube. When the length of the dip tube was shortened to 2 m, the corresponding temperature was 942K and the volume of water steam was 49%.
引文
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