置于楔形热板上的煤自燃特性数值模拟

Numerical simulation on spontaneous combustion characteristics of coal on wedge-shaped hot plate

基于着火和阴燃蔓延两步化学反应,构建了煤自燃楔形热板模型,考虑了热对流以及热辐射,研究了置于楔形热板上的煤自燃特性。首先进行了模型可靠性验证,之后对楔形热板上的煤样自热温度特性、自热过程的多物理参数的变化以及最敏感点火位置进行研究。研究结果表明:构建的数值模型与实验结果有较好的一致性,楔形热板上的煤样发生热失控的临界温度为193℃;随着热板温度的升高,最小点火时间逐渐缩短,呈线性递减趋势;煤体温度、氧气体积分数以及气体产物体积分数变化均提前,氧气以及气体产物在发生热失控瞬间迅速变化;未发生热失控时,最敏感点火位置的高度随热板温度升高而增加;发生热失控时,最敏感点火位置的高度随热板温度降低而减小。

Based on the two-step kinetic scheme of self-heating ignition and smouldering spread,the model of coal spontaneous combustion for wedge hot plate configurations was constructed.The thermal convection and radiation were considered in the numerical model.The characteristics of coal spontaneous combustion on the plate were studied in this paper.Firstly,the reliability of the model was verified,and then the self-heating characteristics,the change of multi-physical parameters of the self-heating process and the most sensitive ignition position were studied.The results showed that the numerical model established in this paper was in good agreement with the experimental results.Critical temperature for thermal runaway of coal sample was 193℃.With the increase of hot plate temperature,the minimum ignition time decreased gradually and showed a linear downward trend.Temperature of coal,oxygen volume fraction and gas product volume fraction changed in advance,and oxygen and gas product changed rapidly in the instant of thermal runaway.The height of the most sensitive ignition position increased with the increase of hot plate temperature when no thermal runaway occurs,and the height of the most sensitive ignition position decreases with the decrease of hot plate temperature when thermal runaway occurs.