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Based on a three-step kinetic mechanism, a one-dimensional, time dependent, numerical model is presented forthe smoldering propagation in a horizontally packed bed of cellulosic material. The kinetic processes include pyrolysis andoxidation degradation of fuel and oxidation of char. Heat transfer between solid and gas is taken into account, and the diffusioncoefficient varies with the temperature. Radiative heat transfer is included by using the diffusion approximation. The effectsof airflow velocity and oxygen concentration are simulated on the smoldering velocity and the averaged maximum temperatureof smoldering fuel. The results indicate that the spread rate varies linearly with increasing airflow velocity, and the inlet airvelocity has little effect on the maximum temperature. The evolutions of gas species and solid compositions are predicted.The effects of frequency factors (A1, A2 and A3) are analyzed. Simulations show that the smoldering spread rate increaseswith increasing A2 (fuel oxidation), but decreases with A1 (fuel pyrolysis) and A3 (char oxidation). 相似文献
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本文对船用核动力装置在受到起伏、摇摆等海洋条件影响时堆体一回路系统在额定和自然循环两种工况下运行特性的计算进行了理论描述。并在Math CAD2001环境下针对日本的“陆奥”号压水堆编制了程序进行计算分析,并得出了比较合理的结果。 相似文献
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以聚氨酯泡沫为试样,建立了多孔介质水平燃料床阴燃的二维两相流数学模型.模型包括燃料吸热热解、燃料放热氧化及焦炭的放热氧化3个反应过程.通过有限单元法对聚氨脂泡沫的阴燃控制方程进行离散,并采用数值分析软件包FEMLAB进行计算求解.数值模拟了来流速度为0.28 cm/s时燃料阴燃的温度分布和固体成分(燃料泡沫、炭粒和灰分)的变化,其中阴燃传播平均速度为0.0214cm/s,阴燃最高温度平均为644.67K;固体成分的变化曲线明显的将填充床分成4个区域:未燃区、燃料热解氧化区、焦炭氧化区及燃料燃尽区.同时,模拟研究了来流速度及燃料特性参数(导热率、比热、密度、孔隙直径等)对阴燃传播特性的影响.结果表明:阴燃速度和阴燃温度随着来流速度的增大基本上呈线性增长;燃料密度对阴燃传播影响最大;对于孔径较大的多孔介质燃料,模型中要考虑辐射的影响.模拟数据与实验数据进行了对比,结果基本吻合. 相似文献
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